Massospondylus

Massospondylus ( ; from Greek, (massōn, "longer") and (spondylos, "vertebra")) is a genus of sauropodomorph dinosaur from the Early Jurassic Period (Hettangian to Pliensbachian ages, ca. 200–183 million years ago). It was described by Sir Richard Owen in 1854 from remains discovered in South Africa, and is thus one of the first dinosaurs to have been named. Fossils have since been found at other locations in South Africa, Lesotho, and Zimbabwe. Material from Arizona's Kayenta Formation, India, and Argentina has been assigned to this genus at various times, but the Arizonan and Argentinian material are now assigned to other genera.
The type species is "M. carinatus"; seven other species have been named during the past 150 years, but only "M. kaalae" among these is still considered valid. Early sauropodomorphs systematics have undergone numerous revisions during the last several years, and many scientists disagree where exactly "Massospondylus" lies on the dinosaur evolutionary tree. The family name Massospondylidae was once coined for the genus, but because knowledge of early sauropodomorph relationships is in a state of flux, it is unclear which other dinosaurs—if any—belong in a natural grouping of massospondylids; several 2007 papers support the family's validity.
Although "Massospondylus" was long depicted as quadrupedal, a 2007 study found it to be bipedal. It was probably a plant eater (herbivore), although it is speculated that the early sauropodomorphs may have been omnivorous. This animal, which was long, had a long neck and tail, with a small head and slender body. On each of its forefeet, it bore a sharp thumb claw that was used in defense or feeding. Recent studies indicate that "Massospondylus" grew steadily throughout its lifespan, possessed air sacs similar to those of birds, and may have cared for its young.
History of discovery.
The first fossils of "Massospondylus" were described by paleontologist Sir Richard Owen in 1854. Originally, Owen did not recognize these finds as those of a dinosaur; instead he attributed them to "large, extinct, carnivorous reptiles" that were related to today's lizards, chameleons and iguanas. This material, a collection of 56 bones, was found in 1853 by the government surveyor Joseph Millard Orpen in the Upper Elliot Formation at Harrismith, South Africa and was donated to the Hunterian Museum at the Royal College of Surgeons in London. Among the remains were vertebrae from the neck, back, and tail; a shoulder blade; a humerus; a partial pelvis; a femur; a tibia; and bones of the hands and feet. All these bones were found disarticulated, making it difficult to determine if all material belongs to a single species or not. However, Owen was able to distinguish three different types of caudal vertebrae, which he attributed to three different genera: "Pachyspondylus", "Leptospondylus" and "Massospondylus". "Massospondylus" was separated from the other two genera on the basis of its much longer caudal vertebrae, which also led to the scientific name that has been derived from the Greek terms "masson"/μάσσων 'longer' and "spondylos"/σπόνδυλος 'vertebra', explained by Owen as "because the vertebrae are proportionally longer than those of the extinct Crocodile called "Macrospondylus"". However, later it was shown that the putative caudal vertebrae of "Massospondylus" were actually cervical vertebrae and that all the material probably belongs only to a single species. On May 10, 1941, the Hunterian Museum was demolished by a German bomb, destroying all the fossils; only casts remain. Because the plaster casts of the lost type specimen fossils were not adequate to accurately diagnose a genus and species under modern taxonomic practices and for research purposes, Yates and Barrett (2010) designated BP/1/4934, a skull and a largely complete postcranial skeleton in the Bernard Price Institute for Palaeontological Research, as the neotype specimen.
"Massospondylus" remains have been found in the Upper Elliot Formation, the Clarens Formation, and the Bushveld Sandstone of South Africa and Lesotho, as well as the Forest Sandstone of Zimbabwe. These remains consist of at least 80 partial skeletons and four skulls, representing both juveniles and adults. The report of "Massospondylus" from Arizona's Kayenta Formation is based on a skull described in 1985. The skull of the Kayenta specimen from Arizona is 25% larger than the largest skull from any African specimen. The Kayenta specimen possesses four teeth in the premaxilla and sixteen in the maxilla. Uniquely among dinosaurs, it also had tiny, one-millimetre-(0.04 in-) long palatal teeth. A 2004 restudy of African "Massospondylus" skulls, however, indicated that the Kayenta specimen did not pertain to "Massospondylus". This Kayenta skull and associated postcranial elements, identified collectively as MCZ 8893, was referred to the new genus "Sarahsaurus" in 2010.
"Massospondylus" had also been reported from Argentina, but this has been reassessed as a closely related but distinct genus. The fossils included several partial skeletons and at least one skull, found in the Lower Jurassic Canon del Colorado Formation of San Juan, Argentina. This material was named "Adeopapposaurus" in 2009. A specimen from South Africa previously assigned to "Massospondylus", BP/1/4779, became the holotype of the new genus and species "Ngwevu intloko" in 2019.
Species.
Many species have been named, although most are no longer considered valid. "M. carinatus", named by Richard Owen, is the type species. Other named species include: "M. browni" Seeley, 1895, "M. harriesi" Broom 1911, "M. hislopi" Lydekker, 1890, "M. huenei" Cooper, 1981, "M. kaalae" Barrett 2009, "M. rawesi" Lydekker, 1890, and "M. schwarzi" Haughton, 1924.
"M. browni", "M. harriesi", and "M. schwarzi" were all found in the Upper Elliot Formation of Cape Province, South Africa. All three are based on fragmentary material, and were regarded as indeterminate in the most recent review. "M. browni" is based on two cervical, two back, and three caudal vertebrae and miscellaneous hind limb elements. "M. harriesi" is known from a well-preserved forelimb and parts of a hindlimb. "M. schwarzi" is known from an incomplete hind limb and sacrum. "M. hislopi" and "M. rawesi" were named from fossils found in India. "M. hislopi" is based on vertebrae from the Upper Triassic Maleri Formation of Andhra Pradesh, whereas "M. rawesi" is based on a tooth from the Upper Cretaceous Takli Formation of Maharashtra. "M. hislopi" was tentatively retained as an indeterminate sauropodomorph in the latest review, but "M. rawesi" may be a theropod or nondinosaur. "M. huenei" is a combination derived by Cooper for "Lufengosaurus huenei", as he considered "Lufengosaurus" and "Massospondylus" to be synonyms. This synonymy is no longer accepted.
"M. kaalae" was described in 2009 on the basis of a partial skull from the Upper Elliot Formation in Eastern Cape of South Africa. This species is known from the same time and region as some specimens of "M. carinatus". It differs from the type species in the morphology of the braincase, as well as in several other characters of the skull such as the proportions of the premaxilla.
Dubious names.
Several genera have been previously synonymized with "Massospondylus". These include the above-mentioned "Leptospondylus" and "Pachyspondylus", as well as "Aristosaurus", "Dromicosaurus", "Gryponyx taylori" and "Hortalotarsus", which are dubious names of little scientific value. Together with "Massospondylus carinatus", Owen named "Leptospondylus capensis" and "Pachyspondylus orpenii" for vertebrae from the same unit and location. "Aristosaurus erectus" was named by E.C.N. van Hoepen in 1920 based on a nearly complete skeleton, and Hoepen also named "Dromicosaurus gracilis", which consisted of a partial skeleton. "Gryponyx taylori" was named by Sidney H. Haughton in 1924. It consists of hip bones. All of the above fossils come from the Hettangian or Sinemurian faunal stages of South Africa, where "Massospondylus" has been found. Under the rules of zoological nomenclature, these names are junior synonyms. They were named after "Massospondylus" was described in a scientific paper; the name "Massospondylus" thus takes priority.
"Ignavusaurus", known from a young specimen, was considered by Yates et al. (2011) to be a probable synonym of "Massospondylus". Cladistic analyses by Chapelle & Choiniere (2018) and Chapelle et al. (2019) agreed with Yates et al. (2011) in demonstrating the massospondylid nature of "Ignavusaurus", but nevertheless recovered it as a distinct taxon of massospondylid.
Description.
"Massospondylus" was a mid-size sauropodomorph, around in length and weighed approximately 1000 kilograms (2200 lb), although a few sources have estimated its length at up to . It was a typical early sauropodomorph, with a slender body, a long neck and a proportionally very small head.
The vertebral column was composed of nine cervical (neck) vertebrae, 13 dorsal (back) vertebrae, three sacral (hip) vertebrae, and at least 40 caudal (tail) vertebrae. The pubis faced forward, as with most saurischians. It had a slighter build than that of "Plateosaurus", an otherwise similar dinosaur. The neck was proportionally longer than in most other plateosaurids, with the foremost cervicals being four times the length of their width. The forelimbs were only half the length of the hindlimbs but quite powerful, as indicated by the broad upper end of the humerus that provided attachment areas for a large arm musculature. Like "Plateosaurus", it had five digits on each hand and foot. The hand was short and wide, with a large sickle shaped thumb claw used for feeding or defense against predators. The thumb was the longest finger in the hand, while the fourth and fifth digits were tiny, giving the forepaws a lopsided look.
Cranial anatomy.
The small head of "Massospondylus" was approximately half the length of the femur. Numerous openings, or fenestrae, in the skull reduced its weight and provided space for muscle attachment and sensory organs. These fenestrae were present in pairs, one on each side of the skull. At the front of the skull were two large, elliptical nares, which were roughly half the size of the orbits. The orbits were proportionally larger in "Massospondylus" than in related genera, such as "Plateosaurus". The antorbital fenestrae, smaller than those seen in "Plateosaurus", were situated between the eyes and the nose. At the rear of the skull were two more pairs of temporal fenestrae: the lateral temporal fenestrae immediately behind the eye sockets, which were shaped like an inverted "T" in "Massospondylus", and the supratemporal fenestrae on top of the skull. Small fenestrae also penetrated each mandible. The shape of the skull is traditionally restored as wider and shorter than that of "Plateosaurus", but this appearance may be due just to differential crushing experienced by the various specimens. Some features of the skull are variable between individuals; for example, the thickness of the upper border of the orbit and the height of the posterior maxilla. These differences may be due to sexual dimorphism or individual variation.
Tooth count is variable between individuals and increases with skull size. The premaxilla shows the constant number of four teeth per side in all known skulls; however, in the maxilla, the tooth count ranges from 14 to 22. There are 26 teeth in each side of the lower jaw in the largest known skull. The height of the teeth crowns decreases from front to back in the upper jaw, but was more or less constant in the lower jaw. The lack of pronounced tooth wear and the variable height of the crowns suggests that the teeth were replaced by succeeding new ones in relatively short time intervals. Notably, there was variation in the tooth morphology based on the position of the teeth in the jaw. The heterodonty present in "Massospondylus" is greater than that present in "Plateosaurus", although not as pronounced as the specialization of teeth in "Heterodontosaurus". Teeth closer to the front of the snout had round cross-sections and tapered to points, unlike the back teeth, which were spatulate and had oval cross-sections.
As with other early sauropodomorphs, it has been proposed that "Massospondylus" had cheeks. This theory was proposed because there are a few large holes for blood vessels on the surfaces of the jaw bones, unlike the numerous small holes present on the jaws of cheekless reptiles. The cheeks would have prevented food from spilling out when "Massospondylus" ate. Crompton and Attridge (1986) described skulls of "Massospondylus" as possessing pronounced overbites and suggested the presence of a horny beak on the tip of the lower jaw to make up the difference in length and account for tooth wear on the teeth at the tip of the snout. However, the difference in length may be a misinterpretation based on crushing in a top–bottom plane, and the possession of a beak is considered unlikely in recent studies.
Classification.
Basal sauropodomorph systematics continue to undergo revision, and many genera once considered classic "prosauropods" have recently been removed from the group in phylogenetic nomenclature, on the grounds that their inclusion would not constitute a clade (a natural grouping containing all descendants of a single common ancestor). Yates and Kitching (2003) published a clade consisting of "Riojasaurus", "Plateosaurus", "Coloradisaurus", "Massospondylus", and "Lufengosaurus". Galton and Upchurch (2004) included "Ammosaurus", "Anchisaurus", "Azendohsaurus", "Camelotia", "Coloradisaurus", "Euskelosaurus", "Jingshanosaurus", "Lessemsaurus", "Lufengosaurus", "Massospondylus", "Melanorosaurus", "Mussaurus", "Plateosaurus", "Riojasaurus", "Ruehleia", "Saturnalia", "Sellosaurus", "Thecodontosaurus", "Yimenosaurus" and "Yunnanosaurus" in a monophyletic Prosauropoda. Wilson (2005) considered "Massospondylus", "Jingshanosaurus", "Plateosaurus", and "Lufengosaurus" a natural group, with "Blikanasaurus" and "Antetonitrus" possible sauropods. Bonnan and Yates (2007) considered "Camelotia", "Blikanasaurus" and "Melanorosaurus" possible sauropods. Yates (2007) placed "Antetonitrus", "Melanorosaurus", and "Blikanasaurus" as basal sauropods and declined to use the term Prosauropoda, as he considered it synonymous with Plateosauridae. However, he did not rule out the possibility that a small group of prosauropods consisting of "Plateosaurus", "Riojasaurus", "Massospondylus" and their closest kin were monophyletic.
"Massospondylus" is the type genus of the proposed family Massospondylidae, to which it gives its name. The Massospondylidae may also include "Yunnanosaurus", although Lu "et al." (2007) placed "Yunnanosaurus" in its own family. Yates (2007) considered "Massospondylus", "Coloradisaurus", and "Lufengosaurus" massospondylids, with "Yunnanosaurus" in Anchisauria. Smith and Pol (2007) also found a Massospondylidae in their phylogenetic analysis, including "Massospondylus", "Coloradisaurus", and "Lufengosaurus", as well as their new genus, "Glacialisaurus". "Adeopapposaurus", based on the fossils once thought to belong to a South American form of "Massospondylus", was also classified as a massospondylid, as was "Leyesaurus", another South American genus that was named in 2011. "Pradhania" was originally regarded as a more basal sauropodomorph but new cladistic analysis performed by Novas "et al.", 2011 suggests that "Pradhania" is a massospondylid. "Pradhania" presents two shared traits of the Massospondylidae recovered in their phylogenetic analysis, and the fossils of "Pradhania" were discovered from the same region and basin in India as "M. hislopi".
The following cladogram shows the position of "Massospondylus" within Massospondylidae, according to Fernando E. Novas and colleagues, 2011:
Paleobiology.
As with all dinosaurs, much of the biology of "Massospondylus", including its behavior, coloration, and physiology, remains unknown. However, recent studies have allowed for informed speculation on subjects such as growth patterns, diet, posture, reproduction, and respiration.
A 2007 study suggested that "Massospondylus" may have used its short arms for defense against predators ("defensive swats"), in intraspecies combat, or in feeding, although its arms were too short to reach its mouth. Scientists speculate that "Massospondylus" could have used its large pollex (thumb) claw in combat, to strip plant material from trees, digging, or for grooming.
Growth.
A 2005 study indicated that "Massospondylus"' sister taxon, "Plateosaurus", exhibited growth patterns affected by environmental factors. The study indicated that, when food was plentiful or when the climate was favorable, "Plateosaurus" exhibited accelerated growth. This pattern of growth is called "developmental plasticity". It is unseen in other dinosaurs, including "Massospondylus", despite the close relationship between the two. The study indicated that "Massospondylus" grew along a specific growth trajectory, with little variation in the growth rate and ultimate size of an individual. Another study of age determination indicated that "Massospondylus" grew at a maximum rate of 34.6 kg (76.3 lb) per year and was still growing at around 15 years of age.
Diet.
Early sauropodomorphs such as "Massospondylus" may have been herbivorous or omnivorous. As recently as the 1980s, paleontologists debated the possibility of carnivory in the "prosauropods". However, the hypothesis of carnivorous "prosauropods" has been discredited, and all recent studies favor a herbivorous or omnivorous lifestyle for these animals. Galton and Upchurch (2004) found that cranial characteristics (such as jaw articulation) of most basal sauropodomorphs are closer to those of herbivorous reptiles than those of carnivorous ones, and the shape of the tooth crown is similar to those of modern herbivorous or omnivorous iguanas. The maximum width of the crown was greater than that of the root, resulting in a cutting edge similar to those of extant herbivorous or omnivorous reptiles. Barrett (2000) proposed that basal sauropodomorphs supplemented their herbivorous diets with small prey or carrion. Gastroliths (gizzard stones) have been found in association with three "Massospondylus" fossils from the Forest-Sandstone in Zimbabwe, and with a "Massospondylus"-like animal from the Late Triassic of Virginia. Until recently, scientists believed that these stones functioned as a gastric mill to aid ingestion of plant material, compensating for its inability to chew, as it is the case in many modern birds. However, Wings and Sander (2007) showed that the polished nature and the abundance of those stones precluded a use as an effective gastric mill in most non-theropod dinosaurs, including "Massospondylus".
Gait and range of motion.
Although long assumed to have been quadrupedal, a 2007 anatomical study of the forelimbs has questioned this, arguing that their limited range of motion precluded effective habitual quadrupedal gait. Neither could the forelimbs swing fore and behind in a fashion similar to the hindlimbs, nor could the hand be rotated with the palmar surfaces facing downwards. This inability to pronate the hand is also supported by "in-situ" finds of articulated (still-connected) arms that always show unrotated hands with palmar faces facing each other. The study also ruled out the possibility of "knuckle-walking" and other forms of locomotion that would make an effective locomotion possible without the need to pronate the hand. Although its mass suggests a quadrupedal nature, "Massospondylus" would have been restricted to its hind legs for locomotion.
Since the discovery of rudimentary and nonfunctional clavicles in ceratopsians, it was assumed that these shoulder bones were reduced in all dinosaurs that did not have true furculae. Robert Bakker (1987) suggested that this would have allowed the shoulder blades to swing with the forelimbs in quadrupedal dinosaurs, increasing their functional forelimb length. This would have reduced the discrepancy of length between fore- and hindlimbs in a quadrupedal "Massospondylus". However, a recent discovery shows that "Massospondylus" possessed well-developed clavicles that were joined in a furcula-like arrangement, acting like a clasp between the right and left shoulder blades and prohibiting any rotation of these bones. This discovery indicates that the clavicle reduction is limited to the evolutionary line leading to the ceratopsians. It also indicates that the furcula of birds is derived from clavicles.
Michael Cooper (1981) noted that the zygapophyses of the neck vertebrae were inclined, prohibiting significant horizontal movement of the neck, so that "consequently any significant movement in this direction must have been accomplished by a change in the position of the entire body". This was contradicted in a recent study, noting that only the basalmost cervicals show inclined zygapophyses, allowing sufficient horizontal movement of the neck as a whole.
Reproduction.
In 1976, a clutch of seven 190-million-year-old "Massospondylus" eggs was found in Golden Gate Highlands National Park in South Africa by James Kitching, who identified them as most likely belonging to "Massospondylus". It was nearly 30 years before extraction was started on the fossils of the 15-centimetre- (6 in-) long embryos. They remain the oldest dinosaur embryos ever found. By early 2012, at least 10 egg clutches from at least four fossiliferous horizons had been found, with up to 34 eggs per clutch. This indicates that this nesting site may have been used repeatedly (site fidelity), by groups of animals (colonial nesting); in both cases, these represent the oldest evidence of this behaviour. Sedimentary structures indicate that the nesting area was in the vicinity of a lake. The eggshells were very thin (about 0.1 mm), allowing gas exchange even in a low oxygen and carbon dioxide rich environment, which indicates that the eggs were at least partly buried in the substrate. There are no hints that "Massospondylus" constructed nests; however, the arrangement of the eggs in tight rows indicates that the eggs were pushed in this position by the adults.
The embryos probably represented near-hatchlings. While the skeletal features were similar to those of the adults, the body proportions were very dissimilar. The head was big with a short snout and very large orbits, whose diameter amounts 39% of the entire skull length. The neck was short, contrasting to the very long neck in the adults. Girdle bones and caudals were relatively tiny. The forelimbs were of equal length to the hindlimbs, indicating that newly hatched "Massospondylus" were quadrupedal, unlike the bipedal adults. The discovery of hatching footprints with manus impressions confirmed their quadrupedality. These impressions show that the hand was not pronated, with palm faces facing each other and the thumb facing forwards. The unpronated manus and the big head indicate that an effective locomotion was not possible for newly hatched "Massospondylus". Notably, the near-hatchings had no teeth, suggesting they had no way of feeding themselves. Based on the lack of teeth and the ineffective locomotion, scientists speculate that postnatal care might have been necessary. This is further supported by evidence that the hatchings remained at the nest sites until they had doubled in size.
Newly hatched juveniles are known from a second sauropodomorph, "Mussaurus"; these remains resemble those of the embryonic "Massospondylus", suggesting that quadrupedality was present in newly hatched "Mussaurus" and presumably other basal sauropodomorphs as well. The quadrupedality of the hatchings suggests that the quadrupedal posture of later sauropods may have evolved from retention of juvenile characteristics in adult animals, an evolutionary phenomenon known as pedomorphosis. This discovery therefore "sheds some light in the evolutionary pathways through which the peculiar adaptations of giant dinosaurs were attained", stated French paleontologist Eric Buffetaut.
Respiratory system.
Many saurischian dinosaurs possessed vertebrae and ribs that contained hollowed-out cavities (pneumatic foramina), which reduced the weight of the bones and may have served as a basic 'flow-through ventilation' system similar to that of modern birds. In such a system, the neck vertebrae and ribs are hollowed out by the cervical air sac; the upper back vertebrae, by the lung; and the lower back and sacral (hip) vertebrae, by the abdominal air sac. These organs constitute a complex and very efficient method of respiration. "Prosauropods" are the only major group of saurischians without an extensive system of pneumatic foramina. Although possible pneumatic indentations have been found in "Plateosaurus" and "Thecodontosaurus", the indentations were very small. One study in 2007 concluded that basal sauropodomorphs like "Massospondylus" likely had abdominal and cervical air sacs, based on the evidence for them in sister taxa (theropods and sauropods). The study concluded that it was impossible to determine whether basal sauropodomorphs had a bird-like flow-through lung, but that the air sacs were almost certainly present.
Paleoecology.
The faunas and floras of the Early Jurassic were similar worldwide, with conifers adapted for hot weather becoming the common plants; basal sauropodomorphs and theropods were the main constituents of a worldwide dinosaur fauna. The environment of early Jurassic southern Africa has been described as a desert. African "Massospondylus" was a contemporary of temnospondyli; turtles; a sphenodontia; rauisuchids; early crocodylomorphs; tritylodontid and trithelodontid therapsids; morganucodontid mammals; and dinosaurs including the small theropod "Coelophysis rhodesiensis" and several genera of early ornithischians, such as "Lesothosaurus" and the heterodontosaurids "Abrictosaurus", "Heterodontosaurus", "Lycorhinus" and "Pegomastax". Until recently, "Massospondylus" was regarded as the only known sauropodomorph from the Upper Elliot Formation. However, newer finds revealed a diverse contemporary sauropodomorph fauna with six additional species, including "Ignavusaurus", "Arcusaurus" and two unnamed taxa as well as two unnamed sauropods.
It is not clear which carnivores may have preyed on "Massospondylus". Most of the theropods that have been discovered in rocks of Early Jurassic age in southern Africa, such as "Coelophysis", were smaller than mid-sized sauropodomorphs like "Massospondylus". These smaller predators have been postulated as using fast slashing attacks to wear down sauropodomorphs, which could have defended themselves with their large hand and foot claws. The 6-metre-(20 ft-) long carnivorous theropod "Dracovenator" lived during the same period (Hettangian to Sinemurian stages) as "Massospondylus" and has also been found in the Elliot Formation of South Africa.


Lake Superior agate

The Lake Superior agate is a type of agate stained by iron and found on the shores of Lake Superior. Its wide distribution and iron-rich bands of color reflect the gemstone's geologic history in Minnesota, Wisconsin, Nebraska, Iowa, Kansas and Michigan. In 1969 the Lake Superior agate was designated by the Minnesota Legislature as the official state gemstone.
The Lake Superior agate was selected because the agate reflects many aspects of Minnesota. It was formed during lava eruptions that occurred in Minnesota about a billion years ago. The stone's predominant red color comes from iron, a major Minnesota industrial mineral found extensively throughout the Iron Range region. Finally, the Lake Superior agate can be found in many regions of Minnesota as it was distributed by glacial movement across Minnesota 10,000 to 15,000 years ago.
Geologic history.
More than a billion years ago, the North American continent began to split apart along plate boundaries. Magma upwelled into iron-rich lava flows throughout the Midcontinent Rift System, including what is now the Minnesota Iron Range region. These flows are now exposed along the north and south shores of Lake Superior. The tectonic forces that attempted to pull the continent apart, and which left behind the lava flows, also created the Superior trough, a depressed region that became the basin of Lake Superior.
The lava flows formed the conditions for creation of Lake Superior agates. As the lava solidified, water vapor and carbon dioxide trapped within the solidified flows formed a vesicular texture (literally millions of small bubbles). Later, groundwater transported ferric iron, silica, and other dissolved minerals passed through the trapped gas vesicles. These quartz-rich groundwater solutions deposited concentric bands of fine-grained quartz called chalcedony, or embedded agates.
Over the next billion years, erosion exposed a number of the quartz-filled, banded vesicles—agates—were freed by running water and chemical disintegration of the lavas, since these vesicles were now harder than the lava rocks that contained them. The vast majority, however, remained lodged in the lava flows until the next major geologic event that changed them and Minnesota.
During the ensuing ice ages a lobe of glacial ice, the Superior lobe, moved into Minnesota through the agate-filled Superior trough. The glacier picked up surface agates and transported them south. Its crushing action and cycle of freezing and thawing at its base also freed many agates from within the lava flows and transported them, too. The advancing glacier acted like an enormous rock tumbler, abrading, fracturing, and rough-polishing the agates.
Description.
The Lake Superior agate is noted for its rich red, orange, and yellow coloring. This color scheme is caused by the oxidation of iron. Iron leached from rocks provided the pigment that gives the gemstone its beautiful array of color. The concentration of iron and the amount of oxidation determine the color within or between an agate's bands. There can also be white, grey, black and tan strips of color as well.
The gemstone comes in various sizes. The gas pockets in which the agates formed were primarily small, about 1 cm in diameter. A few Lake Superior agates have been found that are 22 cm in diameter with a mass exceeding 10 kilograms. Very large agates are extremely rare.
The most common type of Lake Superior agate is the "fortification agate" with its eye-catching banding patterns. Each band, when traced around an exposed pattern or "face," connects with itself like the walls of a fort, hence the name fortification agate.
A common subtype of the fortification agate is the parallel-banded, onyx-fortification or water-level agate. Perfectly straight, parallel bands occur over all or part of these stones. The straight bands were produced by puddles of quartz-rich solutions that crystallized inside the gas pocket under very low fluid pressure. The parallel nature of the bands also indicates the agate's position inside the lava flow.
Probably the most popular Lake Superior agate is also one of the rarest. The highly treasured eye agate has perfectly round bands or "eyes" dotting the surface of the stone.
Cutting and polishing.
A gemstone can be used as a jewel when cut and polished. Only a fraction of the Lake Superior agate are of the quality needed for lapidary. Three lapidary techniques are used on Lake Superior agates:
Distribution of Lake Superior agate.
One of the most appealing reasons for naming the Lake Superior agate as the Minnesota state gemstone is its general availability. Glacial activity spread agates throughout northeastern and central Minnesota, northwestern Wisconsin, Northern Iowa, Nebraska, Kansas and Michigan's Upper Peninsula in the United States and the area around Thunder Bay in Northwestern Ontario, Canada. Lake Superior agates have been found in gravel deposits along the Mississippi River basin. Other types of agate similar to Lake Superior agate have been found in southwestern Wisconsin.


Eccoptochiloides

Eccoptochiloides is a genus of trilobites in the order Phacopida, that existed during the upper Ordovician in what is now the Czech Republic. It was described by Prantl and Pribyl in 1947, and the type species is "Eccoptochiloides tumescens", which was originally described under the genus "Cheirurus" by Barrande in 1852. The type locality was the Vinice Formation.


Ried (natural region)

The Alsatian "ried" consists of meadows liable to flooding, and of gallery forests,
the vegetation of which is lush. The "ried" was formed by the then meandering Rhine,
before it was canalised. The Petit Ried lies north of Strasbourg, whereas the Grand Ried
lies south of Strasbourg. The town of Rhinau possesses 1000 ha of the last example of a temperate
gallery forest in Western Europe, which is located on the right bank of the Rhine.
Toponymy.
The word "ried" derives from Alemannic "Rieth" which means reed, and is related to the English word.
Geography.
Today's Rhine is a pale reflection of what it used to be. Formerly, it used to be many km broad,
spreading its sediments on a large zone, with Europe's largest water table discharging into the Rhine,
or recharging from it, depending on the seasons. In return, the Rhine has become navigable, and
provides Alsace with abundant hydroelectricity. As a matter of fact, France claims for itself the
hydroelectricity produced here, according to the treaty of Versailles. Only the most recent dams, namely Gambsheim (F) - Freistett (D)
and Iffezheim (D) - Beinheim (F), both of them located downstream of Strasbourg in the Petit Ried,
produce electricity shared evenly by both states. The Iffezheim dam has just been equipped with a
fifth turbine.
Ornithology.
The Rhine Rift, and the Ried, is located on a major corridor as regards bird migration
(the other major French corridor is located over the English Channel and the Atlantic Ocean).
Geology.
In the Quaternary period, while the Rhine rift was subsiding, sediment made up of sand and gravel coming partly from the Vosges but above all from the Alps built up. The sediment thickness reaches 75 m in Strasbourg, 250 m in Neuf-Brisach, and 150 m in Mulhouse. Sand coming from the Vosges shows a higher tourmaline content, whereas sand coming from the Alps, which makes up the major part of the sand encountered in the Ried, is characterised by a combination of heavy minerals (green hornblend, epidote and garnet ).
Formerly, the Rhine was flowing into the Rhone, until the barrier constituted by the Kaiserstuhl disappeared. Thanks to their porosity, these weak rocks house Europe's largest water table.
The estimated water quantity amounts to 300 billions cubic metres (of which 50 billions only in Alsace). Numerous sand and gravel pits can be encountered in the Ried, thus making Alsace one of the most productive regions in France, in terms of building materials.


Minmi paravertebra

Minmi is a genus of small herbivorous ankylosaurian dinosaur that lived during the early Cretaceous Period of Australia, about 133 to 120 million years ago.
Discovery and species.
In 1964, Dr Alan Bartholomai, a collaborator of the Queensland Museum, discovered a chalkstone nodule containing an ankylosaurian skeleton in Queensland near Minmi Crossing, along the Injun Road, one kilometre south of Mack Gulley, north of Roma.
In 1980, Ralph E. Molnar named and described the type species, in this case the only species known in the genus, "Minmi paravertebra". The generic name, at the time the shortest of a Mesozoic dinosaur, refers to Minmi Crossing. The meaning of "minmi" itself is uncertain; it refers to a large lily in the local aboriginal language but might also be derived from "min min", a kind of will-o'-the-wisp. The specific name refers to strange bone elements found along the vertebrae, for which Molnar coined the designation "paravertebrae".
The holotype, QM F10329, was discovered in a layer of the Bungil Formation, the Minmi Member, a lagoon deposit which was first dated to the Barremian-Valanginian, but later was recalibrated to the Aptian. It consists of a partial skeleton, lacking the skull. It preserves a series of eleven back vertebrae, ribs, a right hindlimb, and plates of the belly armour. It was the first specimen of a member of the Thyreophora discovered in the Southern Hemisphere.
In 1989, a much more complete skeleton was discovered, specimen QM F1801 that includes the skull and shows an articulated body armour. It was referred to a "Minmi" sp. Since 1989, most information provided on "Minmi" in books and illustrations is based on this second exemplar, but in 2015, it was named as a separate genus, "Kunbarrasaurus".
Between 1989 and 1996 several other specimens were discovered and ultimately referred to a "Minmi" sp. These include QM F33286: a rump with pelvis and osteoderms; AM F35259: ribs with osteoderms; QM F33565: a partial thighbone; and QM F33566: a partial shinbone, perhaps of the same individual as QM F33565. AM F35259 is part of the collection of the Australian Museum. Later specimen QM F119849 was reported, consisting of ribs and osteoderms.
Description.
"Minmi" was a small herbivorous quadrupedal armoured ankylosaurian. In 2016, Gregory S. Paul estimated its length at , its weight at . For an ankylosaurian, "Minmi" had long limbs, perhaps used to quickly search cover under brushes when threatened by large predators which might have been able to flip the small animal on its back.
Unlike other ankylosaurians, "Minmi" had horizontally oriented plates of bones that ran along the sides of its vertebrae, hence its specific name, "paravertebra". Molnar in 1980 acknowledged that these were ossified tendons, but denied that they were homologous to the ossified tendons of other Ornithischia and claimed that they resembled the pathological tendon aponeurosis of modern crocodiles. Victoria Megan Arbour in 2014 deemed this unlikely and could find only one autapomorphy in the holotype: the high vertical extent of the "musculus articulospinalis" tendon ossification at its outer front end, wrapping itself around the side process of the vertebra. In 2015, Arbour and Philip Currie concluded that even this was not unique, which would mean the holotype had no diagnostic features and "Minmi" would be a "nomen dubium". However, the 2015 description of "Kunbarrasaurus" announced that new distinguishing traits of "Minmi" had been discovered and that it should be considered a valid taxon.
Phylogeny.
In 1980, Molnar placed "Minmi" in the Ankylosauria. In 1987, he thought it was a member of the Nodosauridae. In 2011, a new cladistic analysis performed by Thompson "et al." recovered "Minmi" as the basalmost known ankylosaurid. Arbour & Currie entered "Minmi" and "Minmi" sp. as separate operational taxonomic units in their analysis and recovered "Minmi" as the basalmost ankylosaurid but "Minmi" sp. (= "Kunbarrasaurus") as a more basal ankylosaurian, too "primitive" to be included in either the Ankylosauridae or Nodosauridae. Paul in 2010 suggested that both taxa were part of a Minmidae, an ancient and very basal ankylosaurian lineage, also including "Antarctopelta", that had become isolated on Gondwana.
Paleobiology and diet.
A scientific paper that was published in the year 2000 by Ralph E. Molnar and Harold Trevor Clifford found that Minmi was a low browser and grazer whose diet consisted of plants that grew low to the ground. Its diet consisted of plants such as seeds, fruit, flowering plants, and ferns. This meant that Minmi and its cousin "Kunbarrasaurus" had similar diets, but one of the most noticeable differences is that "Kunbarrasaurus" possibly had a diet of fibrous plants while "Minmi" did not.


San Bernardino Valley (Arizona)

The San Bernardino Valley of Arizona is a northeast-by-southwest trending valley in extreme southeast Cochise County, Arizona.
The north end of the valley merges into the northwest-by-southeast trending San Simon Valley; both merge in western perimeter Hidaldgo County, New Mexico. The valley is an asymmetric graben.
Valleys border all flanks of the Chiricahua Mountains massif (and some attached sub-ranges); The San Bernardino Valley borders the southeast of the Chiricahua Mountains; the San Simon Valley borders the northeast. San Bernardino Valley abuts the Peloncillo Mountains of New Mexico on the east, and the smaller adjoining range to its south, the Guadalupe Mountains. To the south, the valley borders Sonora, Mexico and the north regions of the Sierra del Tigre range, of Mexico. At the northern end of the Sierra del Tigre, the Rio San Bernardino joins the Bavispe River, then heads south to Mexico. To the northwest and west, the San Bernardino Valley abuts the Chiricahuas, Pedregosa, and Perilla Mountains.
At the very south of the valley, north of Douglas, Arizona—Agua Prieta, Mexico lies the San Bernardino National Wildlife Refuge. The refuge, grasslands, and wetlands are part of the south and southwest-flowing Yaqui River of Mexico that reaches the northeast region of the Gulf of California.
Geronimo—San Bernardino volcanic field.
The San Bernardino Valley floor is covered by basaltic lava dating from 0.27 to 1.0 Ma (million years ago). The Geronimo—San Bernardino volcanic field is part of the larger Boot Heel volcanic field.
The field covers some 850 km2 and consists of olivine basalt flows, tuff rings and maars with 130 identified volcanic vent areas and cinder cones.


Cerro de las Mitras

The Cerro de las Mitras (Spanish for “Miter's Hill”), is a mountain and a protected area in the Monterrey, San Pedro Garza García, Santa Catarina and García municipalities; state of Nuevo León, México. The mountain is part of the Sierra Madre Oriental, the summit reaches 2,058 MASL, and has 1,303 meters of prominence, the topographic isolation is about 14.48 km. The ridge is about 21 km long stretching east to west. The name comes from the resemblance of the peaks in the ridge with a bishop's mitre.
The Cerro de las Mitras is a popular hiking destination despite its difficulty. Several quarries dedicated to the extraction of limestone to produce concrete operate in the mountain despite its protected area designation.


Antillanca Group

The Antillanca Group is a volcanic group of scoria cones, maars and small stratovolcanoes, in Chile. Casablanca stratovolcano is the tallest volcano of the group, which shelters the Antillanca ski resort on its west flank. Aguas Calientes and Puyehue Hot springs also form part of this volcanic group. The complex encompasses 380 km² and to the west is bordered by the lakes Puyehue and Rupanco.
A great portion of the Antillanca Group lies within Puyehue National Park. The complex is neighbor of the volcanoes Puyehue, Cordón Caulle, Puntiagudo and Osorno.


Lophosteus

Lophosteus is an extinct genus of prehistoric bony fish known from the Pridoli Ohesaare Formation of Estonia.


Cerro Blanco

Cerro Blanco is a hill and historical landmark in the city of Santiago, Chile. This geographic feature
rises above the surrounding terrain and covers a surface area of . It is bordered by Recoleta Avenue on the east, Santos Dumont Avenue on the south and La Unión Street on the north. The latter street separates the hill from the Cementerio General de Santiago. Cerro Blanco (Blanco is Spanish for white) is named so because the white habit used by the Domenicans who were owners of the land where the hill stands during the colonial period.
Completed in 1840, the Iglesia de la Viñita (Church of the Small Wineyard) is located at the lower southeast flank of Cerro Blanco,
which is consecrated to Our Lady of Montserrat.
Stones extracted from a quarry on Cerro Blanco, were used in the construction of some historical buildings in Santiago, including the Santo Domingo Church.
Cerro Blanco metro station is named for the hill.


Lower Paleolithic

The Lower Paleolithic (or Lower Palaeolithic) is the earliest subdivision of the Paleolithic or Old Stone Age. It spans the time from around 3 million years ago when the first evidence for stone tool production and use by hominins appears in the current archaeological record, until around 300,000 years ago, spanning the Oldowan ("mode 1") and Acheulean ("mode 2") lithics industries.
In African archaeology, the time period roughly corresponds to the Early Stone Age, the earliest finds dating back to 3.3 million years ago, with Lomekwian stone tool technology, spanning Mode 1 stone tool technology, which begins roughly 2.6 million years ago and ends between 400,000 and 250,000 years ago, with Mode 2 technology.
The Middle Paleolithic followed the Lower Paleolithic and recorded the appearance of the more advanced prepared-core tool-making technologies such as the Mousterian. Whether the earliest control of fire by hominins dates to the Lower or to the Middle Paleolithic remains an open question.
Gelasian.
The Lower Paleolithic began with the appearance of the first stone tools in the world. Formerly associated with the emergence of "Homo habilis", some 2.8 million years ago, this date has been pushed back significantly by finds of the early 2000s, the Oldowan or Mode 1 horizon, long considered the oldest type of lithic industry, is now considered to have developed from about 2.6 million years ago, with the beginning Gelasian (Lower Pleistocene), possibly first used by australopithecine forbears of the genus "Homo" (such as "Australopithecus garhi").
Still older tools discovered at the single site of Lomekwi 3 in Kenya, announced in 2015, dated to as early as 3.3 million years ago. As such, they would predate the Pleistocene (the Gelasian), and fall into the late Pliocene (the Piacenzian).
The early members of the genus "Homo" produced primitive tools, summarized under the Oldowan industry, which remained dominant for nearly a million years, from about 2.5 to 1.7 million years ago. "Homo habilis" is assumed to have lived primarily on scavenging, using tools to cleave meat off carrion or to break bones to extract the marrow.
The move from the mostly frugivorous or omnivorous diet of hominin "Australopithecus" to the carnivorous scavenging lifestyle of early "Homo" has been explained by the climate changes in East Africa associated with the Quaternary glaciation. Decreasing oceanic evaporation produced a drier climate and the expansion of the savannah at the expense of forests. Reduced availability of fruits stimulated some proto-australopithecines to search out new food sources found in the drier savannah ecology. Derek Bickerton (2009) has designated to this period the move from simple animal communication systems found in all great apes to the earliest form of symbolic communication systems capable of displacement (referring to items not currently within sensory perception) and motivated by the need to "recruit" group members for scavenging large carcasses.
"Homo erectus" appeared by about 1.8 million years ago, via the transitional variety "Homo ergaster".
Calabrian.
"Homo erectus" moved from scavenging to hunting, developing the hunting-gathering lifestyle that would remain dominant throughout the Paleolithic into the Mesolithic.
The unlocking of the new niche of hunting-gathering subsistence drove a number of further behavioral and physiological changes leading to the appearance of "Homo heidelbergensis" by some 600,000 years ago.
"Homo erectus" migrated out of Africa and dispersed throughout Eurasia. Stone tools in Malaysia have been dated to be 1.83 million years old. The Peking Man fossil, discovered in 1929, is roughly 700,000 years old.
In Europe, the Olduwan tradition (known in Europe as Abbevillian) split into two parallel traditions, the Clactonian, a flake tradition, and the Acheulean, a hand-axe tradition. The Levallois technique for knapping flint developed during this time.
The carrier species from Africa to Europe was undoubtedly "Homo erectus". This type of human is more clearly linked to the flake tradition, which spread across southern Europe through the Balkans to appear relatively densely in southeast Asia. Many Mousterian finds in the Middle Paleolithic have been knapped using a Levallois technique, suggesting that Neanderthals evolved from "Homo erectus" (or, perhaps, "Homo heidelbergensis"; see below).
Monte Poggiolo, near Forlì, Italy, is the location of an Acheulian littoral handaxe industry dating from 1.8 to 1.1 million years ago.
Middle Pleistocene.
The appearance of "Homo heidelbergensis" about 600,000 years ago heralds a number of other new varieties, such as "Homo rhodesiensis" and "Homo cepranensis" about 400,000 years ago.
"Homo heidelbergensis" is a candidate for first developing an early form of symbolic language. Whether control of fire and earliest burials date to this period or only appear during the Middle Paleolithic is an open question.
Also, in Europe, a type of human appeared that was intermediate between "Homo erectus" and "Homo sapiens", sometimes summarized under archaic "Homo sapiens", typified by such fossils as those found at Swanscombe, Steinheim, Tautavel, and Vertesszollos ("Homo palaeohungaricus"). The hand-axe tradition originates in the same period. The intermediate may have been "Homo heidelbergensis", held responsible for the manufacture of improved "Mode 2" Acheulean tool types, in Africa, after 600,000 years ago. Flakes and axes coexisted in Europe, sometimes at the same site. The axe tradition, however, spread to a different range in the east. It appears in Arabia and India, but more importantly, it does not appear in southeast Asia.
Transition to the Middle Paleolithic.
From about 300,000 years ago, technology, social structures and behaviour appear to grow more complex, with prepared-core technique lithics, earliest instances of burial and changes to hunting-gathering patterns of subsistence. "Homo sapiens" first appear about 300,000 years ago, as evidenced by fossils found at Jebel Irhoud in Morocco.
Lower Paleolithic era by region.
India.
Neolithic Stone Age of Indian subcontinent (7000 BCE - 5500 BCE) finds were excavated from Pinjore in Haryana on the banks of the stream (paleochannel of Saraswati river) flowing through HMT complex, by Guy Ellcock Pilgrim, a British geologist and palaeontologist, who discovered 1.5 million-year-old prehistoric human teeth and part of a jaw denoting that the ancient people, intelligent hominins dating as far back as 1,500,000 ybp Acheulean period, lived in the Pinjore region near Chandigarh. Quartzite tools of the lower Paleolithic period were excavated in this region extending from Pinjore in Haryana to Nalagarh (Solan district in Himachal Pradesh).


Oberbergischer Kreis

The Oberbergischer Kreis is a Kreis (district) in the state of North Rhine-Westphalia, Germany. Neighboring districts are Ennepe-Ruhr, Märkischer Kreis, Olpe, Altenkirchen, Rhein-Sieg, Rheinisch-Bergischer Kreis, and the urban districts Remscheid and Wuppertal.
Name.
The area of the "Bergisches Land" belonged to the County of Berg for most of the medieval times, which still gives the district its name. What is called "Oberbergisch" ("upper Bergian") lies in the southeast of that earldom: Already in 1740, a description of what had meanwhile become a duchy made a distinction between the "Niederbergisch" part north of the river Wupper and the "Oberbergisch" to its south.
In 1816, after the whole Rhineland was annexed to Prussia, the districts of Waldbröl, Homburg, Gimborn, Wipperfürth, and Lennep were created on the area now covered by the district. In 1825 the districts Gimborn and Homburg were merged to the district Gummersbach. In 1932 it was merged with the district of Waldbröl, and then for the first time called "Oberbergischer Kreis". The restructuring of the districts in 1969/75 did then create the district to its current extent.
Geography.
The Oberbergischer Kreis covers the hills west of the Sauerland and north of the Westerwald. It constitutes the eastern part of the Bergisches Land nature reserve. Situated at an altitude of 100–520 meters above sea level, it is rich in wood and water (numbering ten artificial lakes) and thus a recreational area for citizens from Cologne, the Ruhr area and the Netherlands.
The prevailing rock is greywacke, which was and in places still is mined in large stone quarries.
Coat of arms.
The coat of arms is a combination of the heraldic signs of the territories the district belonged to. The red-white bar in the top symbolizes the County of Mark and the lion that of Berg. Homburg Castle (near Nümbrecht) was the seat of the Princes of Sayn-Wittgenstein-Berleburg.
Politics.
District Administrator.
Since the October 1st, 1999 there is only one (directly elected) District Administrator who at the same time is head of management:
Economy.
The district's economy is marked by small and middle-sized industry, particularly in the areas of plastic and metal processing.


La Portada Formation

La Portada Formation () is a geologic formation of Miocene and Pliocene age located near the Coast Range of northern Chile. The coarse-grained sandstones of the formation contain penguin fossils.


Dolerosaurus

Dolerosaurus is an extinct genus of diapsid known from the early Late Triassic (late Carnian stage) upper Lunz Formation of Austria. "Dolerosaurus" was first named by Richard J. Butler in 2013 and the type species is "Francosuchus trauthi".
Discovery and naming.
In 1939 Friedrich von Huene named a new species of the phytosaur "Francosuchus", "F. trauthi", based upon a small fragment of rostrum. It was at some point later referred to "Paleorhinus", but in 2013, it was renamed to the new genus "Dolerosaurus". Unfortunately very little can be said about "Dolerosaurus" given that its holotype fossil is so small (c. long) and the known remains are so scant. "Dolerosaurus" was referred to phytosauria in 1939, but after subsequent analyses in 2013, it was reclassified as a basal diapsid.


Wollenberg (hill)

The Wollenberg is a hill in Hesse, Germany.


Aggiosaurus

Aggiosaurus is an extinct genus of geosaurine metriorhynchid crocodyliform known from the Late Jurassic (late Oxfordian stage) of Nice, southeastern France. It contains a single species, Aggiosaurus nicaeensis, which was named by H. Ambayrac in 1913.
History of discovery.
"Aggiosaurus" is known only from its holotype, an unnumbered, poorly preserved upper jaw collected by H. Ambayrac in 1912, preserved in limestone which is now housed in the Muséum d'histoire naturelle de Nice. It was collected from the late Oxfordian-aged locality of Cap d’Aggio-La Turbie, in Nice, France. It was initially described as a megalosaurid dinosaur by Ambayrac (1913). Later, Buffetaut (1982) demonstrated that it was in fact a metriorhynchid, closely related to, if not a member of "Dakosaurus". As the type specimen is poorly preserved it is sometimes considered to be a nomen dubium. Young & Andrade (2009) suggested that "Aggiosaurus" is a junior synonym of "Dakosaurus", and that "A. nicaeensis" is referrable to "Dakosaurus" as a distinct species provisionally. They based this referral on its unusually large dentition (apicobasal length in excess of ) that thought to be unique to species of "Dakosaurus" among all other thalattosuchians. "Aggiosaurus" actually has the largest dentition of any known metriorhynchid (up to in apicobasal length), although further phylogenetic analyses found that large robust teeth present also in other geosaurins, such as "Torvoneustes". Young "et al." (2012) resurrected the genus name "Plesiosuchus" for "D. manselii" (which also present this trait) as their phylogenetic analysis found a paraphyletic "Dakosaurus" and suggested more basal position for it within Geosaurini than previously thought. As the presence of unusually large dentition (apicobasal length in excess of ) was considered to be homoplastic among geosaurins, "Aggiosaurus" cannot be considered a junior synonym of either "Dakosaurus" or "Plesiosuchus".
Etymology.
"Aggiosaurus" was first described and named by H. Ambayrac in 1913, and the type species is "Aggiosaurus nicaeensis". The generic name is derived from the name of its type locality, Cap d'Aggio-La Turbie, and from "" (), meaning "lizard" in Ancient Greek. The specific name honors Nice, France, in which it was discovered.


Los Patos

Los Patos (also known as Tres Quebradas) is a mountain in the Andes mountain range of South America. The peak is located on the international border of the Catamarca Province of Argentina and the Atacama Region of Chile. It has a summit elevation of .
Los Patos is a volcano. Potassium-argon dating on dacite taken from the northern flank showed an age of 4,550,000 ± 180,000 years ago. At that time, volcanic activity in the Maricunga Belt had just ended and was shifting towards the area of Ojos del Salado and Nevado Tres Cruces. Another date obtained on the lower part of the volcano is 7,600,000 ± 600,000 years ago. The base of Nevado Tres Cruces rises immediately east of Los Patos. Los Patos is part of the Cordillera Sundt, a mountain chain containing stratovolcanoes with lava domes and lava flows. The chain is constructed by dacite and smaller amounts of andesite. Other volcanoes in the chain include Falso Azufre, Monte Pissis and Mulas Muertas. So-called "Pircas Negras" lavas with compositions similar to adakite have been found on the northern flanks of Los Patos. They contain amphibole and clinopyroxene as the dominant minerals and some samples have been found at and .


Psilopterus

Psilopterus (Greek for "bare wing") is an extinct genus of phorusrhacid ("terror bird") from the Middle Oligocene to Late Pleistocene of Argentina and Uruguay. Compared to other phorusrhacids, members of the genus are both relatively gracile and diminutive, and include the smallest known species of terror bird: with the head raised "P. bachmanni" was in height and weighed about , while the largest members of the genus were only about . The birds resemble the modern cariama ("Cariama cristata"), except with a heavier build and considerably smaller wings. The strong morphological similarity between the claws of the predatory cariama and "Psilopterus", both of which are sharp, curved, and laterally compressed, may indicate they were used to strike prey. In contrast to the other, larger terror birds, Tonni and Tambussi also suggested "Psilopterus" could use their claws to climb trees, and could even fly, but this has been rejected in more recent literature. Fossil finds in Uruguay indicate the genus may have survived until 96,040 ± 6,300 years ago, millions of years after the larger phorusrhacids became extinct.
Description and taxonomy.
The most recent systematic revision of Phorusrhacidae placed "Psilopterus" within the subfamily Psilopterinae, along with the genera "Procariama" and "Paleopsilopterus", and divided "Psilopterus" into four species.
"P. bachmanni".
"Psilopterus bachmanni" (Moreno & Mercerat, 1891) is the smallest species of phorusrhacid, rivaled only by "P. affinis". The species (and genera) is defined by the upper portion of a fused ankle and leg bone (the lectotype MLP-168 is a tarsometatarsus). Other material assigned the species includes additional leg bones that are probably from the same bird, and an almost complete skeleton (PUM-15.904) The material is from several sites in the Santa Cruz Formation in the Santa Cruz Province of Argentina dating to the Middle Miocene (Santacrucian). The most important diagnostic characteristics are a low skull and upper jaw (or maxilla; similar to the mesembriornithine phorusrhacids) and the extreme slant of the front edge of the hole just before the eye (rostal portion of the antorbital fenestra), though there are also differences in the rest of the skeleton.
Synonyms:
Brodkorb considered "Psilopterus minutus" Amerghino, 1981 a separate species, but the incomplete foot bone (tarsometatarsus) is indistinguishable from "P. bachmanni".
"P. lemoinei".
"Psilopterus lemoinei" (Moreno & Mercerat, 1891) is contemporaneous with "P. bachmanni" and likely filled a very similar ecological niche, though "P. lemoinei" is slightly larger, with an estimated weigh approaching . The species is defined by part of a lower leg bone (the lectotype, MLP-162, is the distal end of a tibiotarsus), but a wide variety of material has been referred to the taxon. This material has been found at a number of sites in the Monte León and Santa Cruz Formations in the Santa Cruz Province of Argentina that are dated to the Middle Miocene (Santacrucian). Diagnostic characteristics include a higher skull and upper jaw (maxilla), and the front portion of the hole in front of the eyes (rostral edge of the antorbital fenestra) is less slanted. Additional differences in the remainder of the skeleton are noted in Sinclair and Farr (1932). A number of discrepancies between various specimens have been attributed to differences in age or sex, but material currently assigned to "P. lemonei" and "P. bachmanni" may be reclassified at the species level if reexamined in depth.
Synonyms:
"P. affinus".
"Psilopterus affinus" (Ameghino, 1899) is the most poorly known species of terror bird, represented only by part of a leg bone (tarsometatarsus, MACN-A-52-184) which indicates the bird was very close to "P. bachmanni" in size. "P. affinus" is one of several species known from fragmentary material found in 1899 in the Chubut Province of Argentina (Patagonia), in rocks which dated to the Middle to Late Oligocene (Deseadan). Additional specimens might help clarify the taxonomy of the four apparently unrelated species. "P. affinus" was originally assigned to the genus "Phororhacos" despite the difference in size, and is distinguished from "P. bachmanni" by a groove on the leg bone. Bertelli et al. kept this species in "Phororhacos". Brodkorb assigned the species to "Andrewsornis" in 1967, but this is no longer considered accurate.
"P. colzecus".
The most recently discovered species in the genus, "Psilopterus colzecus" Tonni & Tambussi, 1988, is similar to "P. lemoinei" in size. Known only from a single incomplete skeleton that includes parts of the jaw, arm, and leg (holotype MLP-76-VI-12-2), the species is defined by a groove in the front of the thigh bone (trochlea). The elements were found in the Arroyo Chasicó Formation in Buenos Aires Province of Argentina and are dated to the Late Miocene (Chasicoan).


Petitclercia

Petitclercia is a genus of molluscs from the strigoceratid subfamily Disticocratinae which are included in the ammonitid superfamily Haplocerataceae. "Petitclercia", named by Rollier, 1909.
The shell of "Petitclercia" is involute, very compressed, with a sharp umbilical angle and sharp fastigate venter. Spath (1928)speculated that "Petitclercia" is perhaps "an involute development of "Chanasia"", another of the Distichoceratinae.
Distribution.
Only found in the upper Middle Jurassic (Callovian) of Vendée, France.


List of gold mines in Australia

This list of gold mines in Australia is subsidiary to the list of mines article and lists working, defunct and planned mines in the country organised by state.


Puesto Cortaderas

Puesto Cortaderas is an isolated basaltic pyroclastic cone in Neuquén Province, Argentina.
It is in the Andean Volcanic Belt.


Jama Formation

The Jama Formation is a Pliocene to Early Pleistocene (Montehermosan to Ensenadan in the SALMA classification) geologic formation in Ecuador. The claystones and sandstones were deposited in an coastal environment. The age of the Jama Formation is constrained by 40Ar/39Ar dating of tephra beds. The formation is correlated to the Charco Azul Formation of western Panama and southeastern Costa Rica.
Subdivision.
The formation is subdivided in, from top to base:
Fossil content.
The formation has provided bivalve, gastropod and scaphopod fossils.


Ourhoud Oil Field

Ourhoud Oil Field is an oil field located in Ouargla Province. It was discovered in 1994 and developed by [ Sonatrach. The total proven reserves of the Ourhoud oil field are around 1 billion barrels (140×106tonnes), and production is centered on .


Dubreuillosaurus

Dubreuillosaurus is a genus of carnivorous dinosaur from the middle Jurassic Period. It is a megalosaurid theropod. Its fossils were found in France. The only named species, Dubreuillosaurus valesdunensis, was originally described as a species of "Poekilopleuron", "Poekilopleuron? valesdunensis", which is still formally the type species of the genus. It was later renamed "Dubreuillosaurus valesdunensis" when, in 2005, Allain came to the conclusion that it was not part of the genus "Poekilopleuron". Its type specimen, MNHN 1998-13, is only rivalled in the number of preserved elements in this group by that of "Eustreptospondylus". "Dubreuillosaurus" is considered to be the sister species of "Magnosaurus". It did not show signs of insular dwarfism even though it was uncovered on an island.
Discovery and naming.
In 1994, the mayor of Conteville in Normandy, André Dubreuil, noted that during land rehabilitation of the old quarry of "Pierre de Caen", dinosaur bones had surfaced. He secured a partial skull and some ribs and notified the Paris "Muséum national d'Histoire naturelle". However, professional excavations only started in 1998 when the rock of the collapsed quarry face had already been spread by a bulldozer over a considerable surface. It proved necessary to dig up and sieve many cubic metres of rubble over several years, ultimately salvaging about two thousand bone fragments, varying in size between one and ten centimetres. From these scraps a more complete skeleton had to be reassembled.
In 2002, when this process had not yet been completed, Ronan Allain, after having dedicated a thesis to it, named the find as a new species of "Poekilopleuron": "Poekilopleuron? valesdunensis". The specific name referred to the nearby ancient battlefield of the Battle of Val-ès-Dunes, where William the Conqueror had in 1046 defeated his enemies. The naming paper also contained a description of the skull. The question mark after the generic name already indicated the assignment to "Poekilopleuron" was tentative. By 2005, Allain had come to the conclusion that the new species was not part of "Poekilopleuron". He therefore created the new genus name "Dubreuillosaurus" for this species, the name honouring the Dubreuil family. The type species of the genus is the original "Poekilopleuron valesdunensis", the "combinatio nova" is "Dubreuillosaurus valesdunensis". The 2005 paper also contained a description of the postcranial skeleton.
The holotype, MNHN 1998-13, has been uncovered in a layer of the Calcaire de Caen dating from the middle Bathonian. It consists of a fragmentary skeleton with skull. Preserved parts include: the majority of the skull; the splenial and angular of the lower jaw, a natural mold of the surangular, two cervical vertebrae, cervical ribs, seven dorsals, ribs, gastralia, three sacrals, ten caudals, a chevron, a piece of the scapula, a claw of the hand, a partial thighbone, the upper part of a shinbone, a partial fibula, a fifth metatarsal and the first phalanx of the third toe. Considering the incompleteness of most other megalosaurids, this genus is exceptional in having a significant percentage of the skeleton been found. The type specimen of "Dubreuillosaurus" is in the number of preserved elements only rivalled in this group by that of "Eustreptospondylus". The holotype represents a subadult individual.
Description.
"Dubreuillosaurus" was physically comparable to "Eustreptospondylus". The holotype was an individual by Gregory S. Paul estimated to measure long and to weigh . However, this was a subadult; the adult length is uncertain, though it has been indicated as high as .
In 2005, Allain established some distinctive traits. "Dubreuillosaurus" has an unusually low and long skull, with a length three times the height. In the upper corner of the front edge of the nasal branch of the maxilla, a kink is present, separating a convex curvature below from a concave curvature above. The descending branch of the postorbital has a U-shaped cross-section. The parietal bones are not visible in side view. The supratemporal fenestra has a straight inner edge. A paraquadratic fenestra is lacking. A well-developed process is present on the underside of the jugal branch of the ectopterygoid. The rear edge of the jugal branch of the ectopterygoid, in front of the infratemporal fenestra, is deeply grooved. The lower jaw has a large external mandibular fenestra. The "foramen mylohyoideum" is largely oriented to the front and below. The head of the thighbone is directed to the inside and below. The front underside of the thighbone has a concave surface. In 2012 Matthew Carrano added one autapomorphy: on the rear of the braincase there is a notch between the basioccipital and the bone surface formed by the exoccipitals and the opisthotic.
"Dubreuillosaurus" seemed to lack any sort of crest or horns, but the only known specimen is a juvenile, and it is possible that these structures developed in later life. Like its relatives, "Dubreuillosaurus" probably had short, powerful arms with three-fingered hands.
Phylogeny.
In 2002, "Poekilopleuron? valesdunensis" was assigned to the Megalosauridae. In 2012, Carrano "et al." refined this to the Afrovenatorinae, in which it would be the sister species of "Magnosaurus" within the clade.
The phylogenetic position of "Dubreuillosaurus" according to Carrano "et al." is shown by this cladogram:
Paleobiology.
During the Middle Jurassic much of Europe consisted of a number of islands. The fossil of "Dubreuillosaurus" was discovered in sedimentary rocks that were laid down in coastal, mangrove swamps at the east coast of the Armorican Massif. This suggests that it might have hunted fish and other marine prey.
Allain in 2002 described "P? valesdunensis" as a fish eater or piscivore but this was influenced by the fact that the holotype of "Poekilopleuron bucklandii" had been found together with fish remains. Though uncovered at an island "Dubreuillosaurus" did not show the effects of insular dwarfism; like with "Eustreptospondylus" its small size is due to its being a subadult.


Agkistracanthus

Agkistracanthus is an extinct genus of Chimaera from the Mesozoic era. It currently contains a single species, A. mitgelensis. It is known from the Rhaetian to Hettangian epochs, spanning the transition from the Triassic to Jurassic period. Fossils from this genus are known from Switzerland, Austria, and Britain. It is known mostly from isolated and fragmentary material, including fin spines as well as palantine, symphyseal, and mandibular structures.


Stylonuroides

Stylonuroides is a genus of prehistoric eurypterid. The genus is classified as a stylonurine but more precise classification has proven difficult, with the genus remaining classified as "incertae sedis" within the suborder. The genus contains two species, "S. dolichopteroides" from the Silurian of Ringerike, Norway and "S. orientalis" from the Devonian of Lake Shunet, Southern Siberia.
Description.
The compound eyes of "Stylonuroides" are comparatively large, though their exact shape is unclear due to poor preservation. The posterior margin of the eyes lie in the middle of the prosoma. "Stylonuroides orientalis" is smaller in size than "S. dolichopteroides", with a prosoma measuring about 12 mm. "S. orientalis" differs from "S. dolichopteroides" in a number of features, including that it preserves processes on the genal angles, a slightly convex posterior margin of the prosoma and slightly more widely set compound eyes.
"S. orientalis" is based on a single specimen, PIN 1220/1 (consisting of parts of a prosoma and five anterior segments of the opisthosoma), which can be placed in the genus based on a combination of features, including its strongly elongated parabolic prosoma, large compound eyes and the broad marginal rim of the prosoma.
Species.
"Stylonuroides" contains two valid species, with other named species now seen as invalid.
Invalid or reassigned species are listed below:


Spatsizi Formation

The Spatsizi Formation is a geologic formation in British Columbia. It preserves fossils dating back to the Jurassic period.


The Palms Shopping Centre

The Palms Shopping Centre is a shopping mall located in the suburb of Shirley, Christchurch. Situated from the city's CBD.
Description.
The mall consists of 95 retailers, including Countdown, Farmers and the first Reading Cinemas multiplex in Christchurch. In 2003, a $50 million NZD upgrade was completed, nearly doubling the size to 35,343 m² (380,429 ft²) . The entry plaza of the mall won an NZILA Silver award for landscape design in 2004.
Since the 1990s, AMP Capital has bought 57 residential properties in the area surrounding the mall that is zoned residential. During 2015, the mall owners applied to have some of the land they owned rezoned commercial so that the mall could expand. In December 2015, the commercial rezoning was approved. At the same time, Christchurch City Council also rezoned some residential land to allow higher density around the mall. It was also confirmed that the owners have talked to Christchurch City Council about purchasing a block of council-owned social housing located between the mall and the residential properties they purchased north of the mall.


Oak Ridges Moraine Foundation

The Oak Ridges Moraine Foundation (ORMF) is a non-profit organization based in Newmarket, Ontario, Canada. It was founded in 2002 as a governing body dedicated to the enhancement and preservation of the Oak Ridges Moraine as a healthy and vibrant ecosystem.
History.
The Oak Ridges Moraine stretches 160 kilometres from the Trent River in the east to the Niagara Escarpment in the west. It is more than 90 per cent privately owned with a population of approximately 250,000 to 300,000 people. It crosses 32 municipalities, supplies drinking water to more than 250,000 individuals and supports related agricultural, industrial, commercial and recreational uses.
In 2001 the Ontario government recognized that in order to preserve the Moraine’s health and diversity there was a need for provincial regulation over its many complex land use issues. On May 17, 2001, The Oak Ridges Moraine Protection Act was passed followed by the Oak Ridges Moraine Conservation Act on December 13, 2001. Less than a year later, in April 2002, the Oak Ridges Moraine Conservation Plan (ORMCP) was passed. In the same year, the ORMF was created.
The ORMF has an independent board of directors that consists of individuals nominated by Ontario Nature, the Nature Conservancy of Canada, Conservation Ontario, the Government of Canada, the Government of Ontario, and the Association of Municipalities of Ontario. The Foundation Chair is Caroline Schultz, Executive Director of Ontario Nature.
Accomplishments.
Since established in 2002 the ORMF has distributed in excess of $14 million in grants to 177 projects and leveraged, in collaboration with Moraine partners, an additional $35.8 million for Moraine-related projects. Of the money distributed 41 per cent was dedicated to land securement, 37 per cent to stewardship, 12 per cent to public education, 7 per cent to the expansion of the Oak Ridges Trail, and 3 per cent to research.
In addition, on September 15, 2016 the dedication was held for the official opening of the western trail head in Mono Township which replaced the original western terminus dedication in spring of 2012. In keeping with their mandate "To build and maintain a public hiking trail system on the Oak Ridges moraine, off-road where possible, and To organize and promote hiking on this trail system, and To encourage responsible stewardship of the Moraine's natural environment" the Oak Ridges Trail Association was able to secure part of the Bruce Trails original side trails as part of their main trail. This enabled less highway and road hiking into the more favourable forested areas. Working with partners to establish a trail that continued across the entire Moraine was one of the ORMF's initial goals. The completion of the Trail is also significant as it meets one of the ORMCP's main objectives of a continuous east to west trail along the entire length of the Moraine. However, continued stakeholder and landowner engagement is required to further more off-road sections of this trail system.
Future of the ORMF.
The ORMF’s granting function is currently suspended; however, it is dedicated to continue its work with the government, Moraine stakeholders and the public to create a lasting legacy for the Moraine.
On Friday, February 27, 2015, the Province announced and formally launched the co-ordinated review of the Growth Plan, Greenbelt Plan, Oak Ridges Moraine Conservation Plan and Niagara Escarpment Plan. The review will include two formal stages of public consultation. To facilitate the first stage of the review, the province has released a discussion document – Our Region, Our Community, Our Home, containing guiding questions for comments to assist in the development of proposed amendments to the four Plans. Stakeholders may participate in the review in a variety of ways by visiting the Ministry of Municipal Affairs and Housing website: http://www.mah.gov.on.ca/Page10882.aspx
ORMF is working to prepare for the review and together with your efforts will help the Province make informed decisions about any changes required to the ORMCP to ensure it continues to protect and enhance the environment and water resources on the Oak Ridges Moraine. The Recommendations of the ORMF on the ORMCP can be viewed in their document "Sustaining Our Environment, Planning For Our Future 2015 ORMF Recommendations Report" here http://moraineforlife.org/index.php
In order to further provide long-term funding for ongoing program initiatives the ORMF is continuing to seek additional funding from the Provincial and Federal Governments.


Cerritosaurus

Cerritosaurus is a genus of proterochampsid archosauromorph from the Late Triassic. It has been found in the Santa Maria Formation, in the Geopark of Paleorrota, Brazil. It is represented by one species.
It was collected in 1941 by Antonio Binsfeld, in Sanga da Alemoa. Nearby, there is a small mountain called the Cerrito, after which the genus is named.


Gourdonia

Gourdonia is a trilobite in the order Phacopida (family Acastidae), that existed during the middle Devonian in what is now France. It was described by Pillet in 1954, and the type species is "Gourdonia gourdoni", which was originally described under the genus "Dalmanites" by Barrois in 1883. The generic name is derived from the species epithet. The type locality was the Cathervielle Shale in the Pyrenees mountains.


Geology of Equatorial Guinea

The geological basement of the central and eastern regions Equatorial Guinea is composed of Precambrian rocks which form a part of the Congo craton. They include gneiss, greenstone, schist-amphibolite and granitoids. These older rocks are overlain by sedimentary rocks of Mesozoic, Neogene and Quaternary age in the west and along the coast. The islands of Pagalu and Bioko (Annobon and Fernando Poo) are of relatively recent volcanic origin, forming a part of the Cameroon Volcanic Line.
Tectonics.
The Meso- and Cenozoic formation of the Atlantic rifting event show pre-, syn-, and post-rift tectono sedimentary units.
Economic geology.
There is no significant amount of mineral extraction in Equatorial Guinea. Artisanal gold mining occurs in rivers that come from the Precambrian rocks of the Río Muni. Additional minerals mined are: diamonds, coltan, iron, bauxite, tin, and tungsten
In contrast, Equatorial Guinea is the fourth leading exporter of petroleum in Africa, which contributes significantly to the country's GDP. The country is also seventh in Africa for production of crude oil and the ninth largest producer of natural gas. The reserves are estimated at 150 Mt and 36.81 billion m3, respectively. An increase of production of crude oil has had a significant positive impact on Equatorial Guinea's economy. Since Equatorial Guinea relies so heavily on crude oil, the crude oil price drops in 2009 and 2014 had a measurable effect on the economy.
Geohazards.
Volcanic eruptions may occur on the islands of Bioko and Pagalú. Three amalgamated strato-volcanoes exist on Bioko.


Keseberg (hill)

The Keseberg is a hill in the county of Landkreis Waldeck-Frankenberg, Hesse, Germany.


Bucaramanga Nest

The Bucaramanga Nest is a seismic region located in Colombia. It is named after Bucaramanga, Santander.


Arambourgisuchus

Arambourgisuchus ("[Prof. Camille] Arambourg's crocodile") is an extinct genus of dyrosaurid crocodylomorph from the late Palaeocene of Morocco, found in the region of Sidi Chenane in 2000, following collaboration by French and Moroccan institutions, and described in 2005 by a team led by palaeontologist Stéphane Jouve.
Its type and only species is "A. khouribgaensis", after the town of Khouribga, near which the holotype was found.
Material.
Four specimens of this taxon have been found:
The remains of "A. khourgbaensis" were found in a phosphate mine in the region of Sidi Chenane, part of the Ouled Abdoun Basin. The age of this animal is therefore Thanetian (late Palaeocene).
Systematics.
"Arambourgisuchus khourbgaensis" is a member of the Dyrosauridae, based on the presence of the following synapomorphies:
According to Jouve et al. (2005), it is probably one of the most derived forms, but the lack of better material makes a correct determination of its affinities difficult.
Palaeobiology.
The skull of "A. khourbgaensis" was proportionally one of the longest among all of the Dyrosauridae, reaching a length of 1 meter. Its teeth were sharp but strong and large, as well as being less numerous than the ones in "Dyrosaurus phosphaticus".
Like other dyrosaurids, it was a marine predator.


El Boludo (meteorite)

El Boludo is a meteorite named after the nearest town to where it was found. All known pieces are currently owned by Aerolite Meteorites of Tucson, Arizona.
History.
Numerous meteorite fragments and whole stones were found in 2013 in Sonora, Mexico by American prospector Greg Bruce and his hunting partners while metal detecting for gold nuggets. The first and largest complete individual, weighing , was found on the surface a few kilometers northwest of the town of El Boludo in a dry wash. A search with metal detectors yielded smaller fragments and a few smaller whole stones.
All known specimens were purchased by Aerolite Meteorites of Tucson, Arizona, owned by Geoff Notkin. Aerolite Meteorites currently holds the main mass, while a mass is held at the University of New Mexico’s Institute of Meteoritics.
El Boludo is one of 109 confirmed meteorites from Mexico, including El Tiro (meteorite), which was also held by Aerolite Meteorites.
Physical characteristics.
Relatively small chondrules and abundant opaque grains set in a dark brown groundmass.
See also.
Glossary of meteoritics


Discosauriscus

Discosauriscus was a small seymouriamorph which lived in what is now Central and Western Europe in the Early Permian Period. Its best fossils have been found in the Broumov and Bacov Formations of Boskovice Furrow, in the Czech Republic.
Classification.
"Discosauriscus" belongs to the order Seymouriamorpha, and is the type genus of the family Discosauriscidae. Currently recognised are two valid species - "Discosauriscus austriacus" and "Discosauriscus pulcherrimus". "Letoverpeton" is a junior synonym of "Discosauriscus".
Characteristics.
Discosauriscids were long thought to be known from larval or neotenic forms, and three ontogenetic stages had been distinguished. However, more recent studies concluded that some subadult, probably terrestrial specimens were known, so the case for neoteny in this taxon is not as well-supported as once thought. "Discosauriscus" had wide jaws with sharp teeth, short limbs and relatively long tail. The phalangeal formula was 2-3-4-5-3 for both hind- and forelimbs. The body was covered with rounded scales with concentric rings, and a well-preserved lateral-line system has been described.
"Discosauriscus" may have had electroreceptive organs.


Makowskia

Makowskia is an extinct genus of discosauriscid seymouriamorph known from the early Permian (lower Saxonian age) of Boskovice Furrow, in the Czech Republic. It was first named by Jozef Klembara in 2005 and the type species is "Makowskia laticephala". The generic name honors Alexander Makowsky for describing the first specimens of discosauriscids from the Boskovice Furrow, and the specific name means “broad” ("latus" in Latin) + “head” ("kefalé" in Greek). "Makowskia" is known only from one specimen, the holotype SNMZ 26506, a skull and anterior portion of postcranial skeleton. A phylogenetic analysis places "Makowskia" as the sister taxon to "Spinarerpeton".


Cerro Tuzgle

Cerro Tuzgle is a dormant stratovolcano in the Susques Department of Jujuy Province in Argentina. Tuzgle is a prominent volcano of the back-arc of the Andes and lies about east of the main volcanic arc. Part of the Central Volcanic Zone of the Andes, it is high above sea level and was constructed during different stages over a caldera and lava domes. Some major lava flows emanate from the summit crater, and one confirmed and one possible flank collapse unit as well as an ignimbrite sheet are associated with this volcano.
The first volcanic activity of Tuzgle occurred 650,000 years ago and formed the Tuzgle Ignimbrite. Subsequently, lava domes were erupted and three lava flow units were named San Antonio, Azufre, and Tuzgle. The latest lava flows are dated at 300,000 years ago and volcanic activity may have continued into the Holocene. Several thermal springs are associated with the volcano, and some have been investigated for possible geothermal energy production. Sulfur was formerly mined on the mountain.
Geography and geomorphology.
Cerro Tuzgle is located near the eastern border of the Argentina Puna. Politically, it is part of the Susques Department of the Jujuy Province. San Antonio de Los Cobres lies from Cerro Tuzgle and Susques , while the cities of Salta and San Salvador de Jujuy are and away, respectively. A locality called "Sey" is reported northwest from Cerro Tuzgle. The volcano is visible from Provincial Route 74. Its name, which is also rendered as , or , comes from the Kunza language. It means "knoll" and refers to the shape of the volcano.
Cerro Tuzgle is a simple volcanic cone and the largest in the backarc region of the Andes. It is a well preserved stratovolcano that rises from a surrounding terrain at elevation to a summit at elevation. A platform lies at the summit of the volcano. The mountain is occasionally snow-covered and frost weathering has produced patterned ground and blockfields. In 1926 it was reported that a crater lake lies on the summit.
Three east-west trending fissure vents in the summit area are the source of dark lava flows that flowed southward and southwestward, and are flanked by high scoria ridges. The lava flows that make up the volcanic cone are blocky, rich in crystals and have variable appearance. Numerous young-looking lava flows descend the slopes of Cerro Tuzgle. A well-preserved lava flow descends the mountain and is visible on its southern flank. Older flows reached distances of from the volcano. A long scarp runs across the northwestern flank of Cerro Tuzgle and separates two units of lava flows; it probably formed through a localized collapse of the volcanic edifice in this sector. A depression in the southern flank of the volcano may also be evidence of a collapse in that direction. A parasitic vent is located on the western foot of the volcano.
Abandoned sulfur mines occur on Cerro Tuzgle and are visible from its south-southwestern flank; these include Mina Betty on the northwestern flank between elevation where in 1939 seven sulfur outcrops were reported. A road transitable by trucks was constructed at that time to reach the summit area.
The volcano rises in a north-tilted, north-south trending tectonic depression, which is delimited by normal faults and two horsts north and south of Cerro Tuzgle. The region is endorheic and drainages ultimately end in salt pans. The Quebrada Aguas Calientes passes west and Quebrada de Charcos east of the volcano; the latter later becomes Quebrada Los Charcos north of the volcano and converges with Quebrada Aguas Calientes. Drainage around the volcano is focused by surrounding ridges into a watershed that drains northward, which contains permanent rivers feed by springs at the bottom of valleys. Carbonate deposits and thermophilic algae have been reported from the Quebrada Aguas Calientes. Peatland-lake complexes occur southeast of Cerro Tuzgle.
Geology.
Along the west coast of South America, the Nazca Plate subducts in east-northeast direction beneath the South American Plate in the Peru-Chile Trench, at a rate of . The subduction process is responsible for the volcanic activity in the Andes, which occurs in four volcanic belts, from north to south these are the Northern Volcanic Zone, the Central Volcanic Zone, the Southern Volcanic Zone and the Austral Volcanic Zone.
The Central Andes are subdivided in three sectors, the Western Cordillera with the active volcanic arc, the wide Altiplano-Puna high plateau and the Eastern Cordillera-Subandean Ranges. The high plateau began to form in the Eocene-Oligocene due to tectonic shortening of the Andes. Volcanic activity is distributed between the Western Cordillera and the Altiplano-Puna high plateau, where strike-slip faults and thrust faults organize magma ascent.
The tectonic regime in the area has changed over time and now the volcano lies just north of a transitional zone which separates steep subduction farther north from shallow subduction farther south. During the Miocene and Pliocene, the lower crust failed, allowing the uplift of the region and the injection of fresh magma that triggered extensive volcanic activity. During that time, the Subandean Ranges and the Eastern Cordillera formed. Later, during the Pliocene, subduction became steeper and volcanism shifted westward, and the composition of the remnant volcanism changed along with a change in the tectonic regime from uplift and east-west directed compression to north-south directed spreading and east-west directed compression. Volcanic activity also changed; between 17.5 and 5.3 million years ago it took place over the entire area whereas after 1.5 million years it has focused on the central-eastern Puna plateau. Between these two phases, sedimentation occurred and formed the Pastos Chicos Formation.
Local.
Cerro Tuzgle is part of the back-arc of the Andean Central Volcanic Zone, being about east of the main volcanic arc, and its largest Quaternary member. Other volcanic cones in the area are San Geronimo and Negro de Chorrillos, which erupted 780,000±100,000 and 200,000±150,000 years ago, respectively, Tocomar, which erupted 1.5–0.5 million years ago, and Aguas Calientes caldera. All these volcanoes are located south of Cerro Tuzgle.
Extensive volcanic rocks of Miocene to Pliocene age occur in the area, which were erupted by volcanoes such as Aguas Calientes caldera and Cerro Queva. Older rocks belong to the Faja Eruptiva geologic formation of Ordovician age. The total thickness of the crust reaches . The basement is formed by Cambrian and Precambrian formations of metamorphic character, such as the Puncoviscana Formation. A large tectonic lineament, the Calama-Olacapato-El Toro lineament, intersects the Andes at Cerro Tuzgle. It reaches from the forearc in Chile across the mountain range into the foreland of Argentina, and it separates the northern from the southern Puna. The distribution and history of volcanic activity differs between these two regions. Other similar faults cut across the Andes. It is a strike-slip fault that consists of several separate faults, some of which show evidence of Quaternary activity and could produce earthquakes. Within the Andes proper, this activity mainly occurs in the form of normal faulting; only south of Cerro Tuzgle is there a segment with strike-slip faulting. Movement along most of these faults appears to clamp the magma chamber and magma conduits at Cerro Tuzgle, thus impeding volcanic activity there.
Gravimetric and magnetotelluric surveys have identified a partially molten magma chamber between depth, which also contains saline fluids. Seismic tomography has identified zones with anomalously low seismic velocity which descend from Cerro Tuzgle to depth in the downgoing slab.
Composition.
Cerro Tuzgle has mainly erupted andesite and dacite, which define a crystal- and potassium-rich calc-alkaline suite with seriate flux and porphyritic textures. The rocks contain large feldspar and quartz phenocrysts and small phenocrysts of amphibole, clinopyroxene, olivine, orthopyroxene and plagioclase. Xenoliths and xenocrysts are also found and biotite, sanidine and zircon have been reported as well. At Aguas Calientes, sinters consisting of boronatro-calcite, chalcedony and opal occur. A cesium-rich pharmacosiderite-like mineral has been found at a hot spring. Different rock units have different phenocryst components and trace element compositions. The rocks of Cerro Tuzgle are the most diverse volcanic rocks in the back-arc of the Central Andes.
Magma mixing processes involving fractionating mafic magmas and crystallization have been invoked to explain the origin of Cerro Tuzgle's magmas. The parent magmas originated in the mantle and the crust, with the crustal parts joining the mantle-derived magmas in the deep crust. These crustal components originally came from the upper crust and reached the lower crust during tectonic processes. At this stage crystal fractionation also takes place. The ascending magmas then accumulate in the crust and either erupt or are assimilated by ascending mafic magmas.
Climate and vegetation.
The climate is cold, owing to its high elevation, and the diurnal temperature range reaches . Winds blow mainly from the west and reach . During winter, insolation is high, cloud cover and precipitation are low and strong winds blow through the area. According to 1939 reports, thunderstorms and snowfall are common at Cerro Tuzgle.
The region is arid, with less than annual precipitation as it is part of the Andean Arid Diagonal where the Eastern Cordillera prevents moisture-bearing winds from reaching the Puna. The little precipitation that falls originates in the Atlantic Ocean and the Amazon and arrives during the summer monsoon; additionally cold fronts coming from the westerlies over the Pacific Ocean occur. The amount of precipitation is influenced by the El Niño-Southern Oscillation, where El Niño is associated with drought and La Niña with wetter weather.
Vegetation is sparse and consists of tola, "Vachellia caven" and yareta. Animals that live in the area include chinchillas, condors, Coots, Darwin's rheas, ducks, eagles, "Galea" species, guanacos, llamas, suris and vicuñas. Peatlands are dominated by the plant "Oxychloe andina", "Distichia muscoides" and "Zameioscirpus muticus", with other cyperaceae being subordinate. Annual precipitation there amounts to , almost all of which falls during October to March. Peatlands close to Cerro Tuzgle have been used to reconstruct the local climate during the Holocene. Reconstructed past precipitation levels show alternations between wetter and drier periods during the last 1,800 years, with the last 130 years being relatively dry.
Eruption history.
Cerro Tuzgle was active during the Pleistocene and its most recent eruption may have followed a period of inactivity. With the exception of one flow, most are partially degraded and buried by aeolian material. Volcanic activity took place in multiple stages:
Two schemes for classifying the subsequent activity have been proposed, the first:
A substantially different reconstruction was provided by Norini "et al." 2014:
The "Old Complex" has a volume of , the subsequent units only reach . There is a trend from voluminous ignimbrites and dacites, formed through melting of the crust at high temperatures, early in the volcano's history to less voluminous mafic magmas, which erupted through brittle faults.
The volcano is presently inactive. The Argentina geological service SEGEMAR considers Cerro Tuzgle among the more dangerous volcanoes in Argentina. While the region is thinly inhabited, the occurrence of a sector collapse at Cerro Tuzgle implies that mining and geothermal energy exploitation efforts in the area could be imperiled by similar future events.
Geothermal activity.
Springs occur at Agua Caliente de Tuzgle northwest from the summit and at Mina Betty () south-southeast from Cerro Tuzgle. Both emit alkaline waters containing chloride at temperatures of and , respectively. Agua Caliente de Tuzgle also emits gases and has produced sinter deposits. The Antuco hot springs southwest from Cerro Tuzgle may receive their heat from Cerro Tuzgle. These springs and other springs in the Tuzgle area are recharged by precipitation on surrounding ridges; large-scale fracture systems in the ground control its flow and water emerges in proximity to deeply incised valleys which provide the path for water to reach the surface. Temperatures at depth exceed .
Tourism, mining and geothermal potential.
These hot springs and others such as Pompeya and Tocomar might be used for tourism, as they are located close to the main roads of the area. The volcano might also be a suitable target for mountaineering; its ascent poses little difficulty to trained mountaineers. The first reported ascent was done by Von Rosen in 1990, but the occurrence of Inca ceremonial sites in the form of a raised platform and structures formed by piled-up rocks on the summit region was reported by Ceruti 1999. Neighbouring volcanoes as well as the Nevado del Chañi ridge are visible from the summit.
The first findings of sulfur occurred in 1924, but they were not immediately exploited. A mining concession for Mina Betty was reportedly issued by 1933, while approval for two other mines in the summit area was still pending in 1939. The machinery required for sulfur processing was installed south-southeast of the volcano and bore the name "Ojo del Tuzgle"; the sulfur was transported there either by mules or by trucks. A spring there was used as a water source for mining activities. During parts of the year bad weather conditions rendered mining impossible.
In the 1970s and 1980s numerous companies prospected the area for geothermal power generation. They established the presence of two superposed heat reservoirs, one at depth in an older ignimbrite and another at depth in Ordovician-age rocks. A major power line between Argentina and Chile runs across the area, and local mines along with the towns of Olacapato and San Antonio de Los Cobres could provide a market for geothermal power. A potential yield of 28–34 megawatt electrical power has been estimated, but no progress towards exploiting these resources has been made. The geothermal vents could also be used to extract minerals or for spas. Concerns have been raised that the sensitive ecosystems might be threatened by human activity.