Georgetown Formation

The Georgetown Formation is a geologic formation in Mexico and the United States. It preserves fossils dating back to the Cretaceous period.
A stratigraphic column at the Mount Bonnell location starts with the Lower Cretaceous Trinity Group overlain by the Edwards Group and the Georgetown Formation. Upper Cretaceous formations follow, starting with the Del Rio Clay, Buda Limestone, and then the Eagle Ford Group. Formations within the Trinity Group include the Hammett Formation, Cow Creek Formation, Hensel Formation, and Lower and Upper Glen Rose Formation. The Hammett and the lower portion of the Upper Glen Rose act as confining units (or aquitard) for the Middle Trinity Aquifer. The Upper Glen Rose contains the Upper Trinity Aquifer, which appears to have intra-aquifer groundwater flow with the Edwards Aquifer as water levels are at the same elevation. Formations within the Edwards Group include the Kainier Formation and the Person Formation. The Upper Cretaceous rock units confine the Edwards Aquifer within the Edwards Group and the Georgetown Formation.


Tetragonias

Tetragonias is an extinct genus of non-mammalian synapsid from the Anisian Manda Beds of Tanzania. "Tetra"- means “four,” and "goni"- means “angle,” referencing the square shape of the "Tetragonias" skull when viewed dorsally. Not to be confused with "Tetragonia," "Tetragonias" were dicynodont anomodonts discovered in the late 1960s by paleontologist A. R. I. Cruickshank in the Manda Formation.
Originally thought to have existed during the lower Middle Triassic age, also called the Anisian age, Gay and Cruickshank (1999) later postulated that the Manda Formation may have actually been of the Ladinian age. This terrestrial herbivore was determined to have relation to the genera Lystrosaurus and Kannemeyeria. It is also classified under Amniota as well as the family, Shansiodontidae. The most common species type analyzed is "Tetragonias njalilus".
Discovery and historical information.
Initially described by F. von Huene in 1942 as "Dicynodon njalilus", Cruickshank renamed this species "Tetragonias njalilus" to correctly point out how different the palate and intertemporal bar structures of this Triassic creature were from the other mostly Permian dicynodonts. He mainly aimed to revise the earlier von Huene descriptions of the skull and postcranial skeleton. Cruickshank’s contribution to the scientific classification for "Tetragonias" is what is used today, although, there have been questions as of late concerning the "taxonomic integrity" of "Tetragonias" due of Cruickshank's misattribution of certain size differences in features to sexual dimorphism as opposed to feeding differences or other taxa.
Description and paleobiology.
As for Cruickshank’s specific diagnosis, "T. njalilus" was described as a “medium sized dicynodont, tusked in both sexes" with an overall rectangular skull shape in dorsal view. He included details about the maxillary processes surrounding the tusks differently in males and females, the fact that the postorbital bones do not meet the squamosals at the back of the temporal fenestrae, information about the size of the interpterygoid space in relation to the length of the internal nares, and most significantly, that the intertemporal bar is “drawn out into low parietal crest.”
Skull.
"T. njalilus" skull bones are quite large. One notable feature is the “sharply downturned snout,” which inspired the hypothesis of possible relation to the genus "Lystrosaurus". However, "T. njalilus" has much larger temporal fenestrae than "Lystrosaurus" "murrayi", as well as a shallower skull, no postfrontals,  a parietal crest, and differences in size of some parts of the palate. The postorbitals don’t cover the parietals to the same degree as von Huene had described, and as mentioned before, do not meet the squamosals.
The palatal openings to the internal nares of Triassic dicynodonts are significantly larger than the palatal openings of Permian dicynodonts, which is a consistent pattern that have prompted some have tried to explain using the idea that concentrations of atmospheric oxygen have been gradually declining and contributed to end-Permian extinction.
Postcranial skeleton.
Pelvic girdle and locomotion.
To further expound on the posture of the "Tetragonias" pelvic girdle, the iliac blade forms a ventromedial angle with the ischium and the pubis. All the pelvic bones in the acetabulum are fused. There is a curvature in the pelvis of "Tetragonias" that causes the pubis and ischium to extend far medially and ventrally (see Fig. 4 of Fröbisch). This causes the iliac blade to form the major vertical component of the pelvic bone, which contrasts with what Cruickshank’s 1967 paper suggests. It appears there was a misinterpretation about the entire pelvis being vertical.
In "Tetragonias" the straight medial margins of the puboischiadic suggest an articulation which is supported by ligaments or cartilage, although there’s no evidence for a suture or fusion along the midline. All pelvic bones in the holotype of "T. njalilus" at both the left and right sides of the pelvic girdle of are fused. This indicates that movement b/n the pelvic bones of one body side was impossible (in the mature animal). The pelvis is separated into a vertically & a more horizontally oriented part. It possesses an upward-arched backbone, though less pronounced than Cruickshank had postulated.
As mentioned earlier concerning the biomechanical strain on the hind limb, most of "Tetragonias's" body weight would have been carried by the adducted hind limb rather than pelvis: “In this orientation of the pelvic girdle, the supraacetabular crest is strongly overhanging the acetabulum, forming a well-developed dorsal roof to the laterally pointing articulation surface. This feature emphasizes a direct transmission of the body load from the pelvis to the femur, resulting in a more adducted position of the hind limb.” This inhibits "Tetragonias" from sprawling motion, but rather, a parasaggital gait.
Vertebrae.
Most synapsids possess only 3 sacral vertebrae, which articulate with the ilium and are vital in tetrapod locomotion. According to Griffin et. al., “The ancestral synapsid probably possessed two sacral vertebrae (Romer 1956; LeBlanc and Reisz 2014), with Therapsida and some non-therapsid lineages (e.g., Caseidae, Edaphosauridae, Sphenacodontidae) incorporating a third sacral from the caudal series.”
Synapsids display very little variation in the number of presacral vertebrae, as their axial column is highly conserved. However, Dicynodontia, including "T. njalilus", is an exception, containing a clade of anomodont therapsids with far greater variation in morphology. These amonodonts can possess up to seven or even more sacral vertebrae, which is quite the deviation from its therapsid relatives. This is likely attributable to the trend of growing body size observed throughout dicynodont evolutionary history, which positively correlates with an increase in sacral vertebrae number. This has also led to a  wide-ranging variety of body sizes. These sacral vertebrae are used as a key identifying feature in "Tetragonias" phylogeny.
Researchers hypothesize that dicynodonts that increased their number of sacral vertebrae from three to four achieved this by adding a novel fourth vertebrae anteriorly to the other three, which make up the plesiomorphic sacrum. (Griffin) As for taxa with more than four sacral vertebrae, they essentially follow the same body plan in that there are “three plesiomorphic sacrals...in addition to one or more novel vertebrae...(see Figs. 1, 2)...Taken together, our observations indicate that all dicynodonts with a given sacral count appear to possess identically constructed sacra...Most novel sacral vertebrae are added anteriorly to the plesiomorphic sacrum in dicynodonts, with only one vertebra added posteriorly.”
Other features.
The basicranium of most Triassic dicynodonts shortens compared to those of the Permian. However, "Tetragonias" and a few other genera actually maintain the same basicranial length as Permian dicynodonts.
Geological and paleoenvironmental information.
The Manda Formation, also known as Manda Beds, is a geological formation located in the southern region of Tanzania in the Ruhuhu Basin. The formation is made primarily of sandstone but also consists of siltstone and mudstone.
At the time of his 1967 publishing, Cruickshank hypothesized that the Manda Formation was of the Middle Triassic age and also made mention that some parts of the Manda Beds were understood to be the stratigraphic equivalent of the Molteno Beds of South Africa. This latter piece of information was due to the fact that Kannemeyeria latifrons, which existed during the Lower Triassic Cynognathus-zone, occurred in both formations.


Nealeodus

Nealeodus is a genus of conodonts which existed in what is now Canada during the middle Ordovician. It was described as a new genus for the species "Lenodus martinpointensis" by Svend Stouge in 2012.


Oecoptychius

Oecoptychius is an extinct genus of fossil ammonite cephalopods. The species lived during the Middle Jurassic.
Taxonomic position.
"Oecophtychius" was named by Neumayr in 1878. It is placed into Oecoptychitidae, a family of dwarf ammonites established by Arkell, 1957, that is a part of the superfamily Stephanoceratoidea.
Diagnosis.
"Oecoptychius" is an eccentrically coiled, dwarf ammonite. Inner whorls smooth, spheroidal; outer whorls with fine biplicate ribbing, ventral groove, and an acute elbow at half a whorl before the aperture; peristome contracted, with outwardly directed lappets.
Distribution.
Fossils of the "Oecophtychius" species have been found in Jurassic sediments of France, Germany and Madagascar.


Mopsitta

Mopsitta tanta is an extinct bird of uncertain taxonomic position from the Early Eocene of Denmark; its remains were recovered from the Fur Formation. So far, the holotype and only known specimen is a single humerus bone of rather large size. Although the phylogenetic position of genus is unclear, it was initially presumed to be phylogenetically closer to Recent Psittacidae than to other known Palaeogene psittaciforms and may, therefore, represent the oldest known crown-group parrot.
However, further examination subsequently pointed out that the fossil lacks clear psittaciform (let alone psittacid) apomorphies. Following the discovery that the fossil ibis genus "Rhynchaeites" also occurred in the Fur Formation, it was hypothesized that the "M. tanta" humerus actually belongs in that genus, being a better match (except in size) to the known "Rhynchaeites" remains than to any psittaciform fossil hitherto found.


Cipactlichthys

Cipactlichthys is a genus of extinct holostean fish from the Lower Cretaceous of Mexico. The only known species is "Cipactlichthys scutatus".
Discovery and etymology.
"Cipactlichthys scutatus" is known from two fossils discovered in the Tlayua Formation near the town of Tepexi de Rodríguez, in Puebla, Mexico.
 The Tlayua Formation, is Albian (Early Cretaceous) in age, interpreted as an epicontinental marine deposit. Due to its high quality preservation and abundance of fish fossils, the formation is considered one of the most important sources of Cretaceous fishes in Mexico.
The genus name is a combination of "Cipactli", the Aztec mythological sea monster said to be part fish and part reptile, and "ichthys", Greek for "fish". The specific epithet "scutatus" is Latin for shield, referring to the large dorsal and ventral scutes.
Description.
"Cipactlichthys" is an elongate fish, approximately 130 mm in total length, or 100 mm in standard length. Its dermal bones and scales are covered in ganoine and decorated with tubercles and ridges. The jaw extends to behind the rear end of the orbit. The pectoral fins are relatively long, with the first ray extending to the anterior edge of the pelvic fins. The caudal fin is forked and homocercal (upper and lower lobes of equal length). The dorsal fin contains at least 8 fin rays. The anal fin is larger than the dorsal fin and also bears at least 8 rays. The scales vary greatly in size and shape, with a series of large plate-like scutes along the dorsal and ventral midline behind the dorsal and anal fin.
Classification.
"Cipactlichthys" is classified in the clade Halecomorphi due to possession of a crescent-shaped preopercle and the involvement of the symplectic bone in jaw articulation. However, it has not yet been assigned to an order or family, instead considered a halecomorph of uncertain placement ("incertae sedis"). The only living halecomorph is the bowfin, "Amia calva," but this group has a diverse fossil record. A phylogenetic analysis placed "Cipactlichthys "as sister to a clade containing Amiiformes and the extinct order Ionoscopiformes.


Thomasinotus

Thomasinotus is an extinct genus of prehistoric bony fish that lived in the Induan stage of the Early Triassic epoch in what is now Madagascar. It belongs to Parasemionotidae together with "Albertonia", "Candelarialepis", "Jacobulus", "Lehmanotus", "Parasemionotus", "Qingshania", "Stensioenotus", "Suius", and "Watsonulus".


Mylodon

Mylodon is a genus of extinct ground sloth belonging to the family Mylodontidae, known from the region of Patagonia in Chile and Argentina in southern South America. With a total length of 3 to 4 m, it is one of the best-known and largest representatives of the group. The oldest finds probably date to the Lower Pleistocene. Most of the fossil remains, however, date from the Upper Pleistocene period. One of the most important sites of this phase is the Cueva del Milodón in southern Chile. Shortly after, about 10,200 BP, "Mylodon" became extinct. At this point in time, it coexisted with the first human colonists in America. However, there is little evidence that it was hunted by humans.
In "Mylodon"'s case, not only bones and teeth are known, but also various soft tissue and integumentary structures are preserved. The diet of "Mylodon" is known in great detail due to fossilized faeces. Its skull is greatly elongated and, compared to other large mylodontids, is narrower, possessing a completely closed nasal arch. Other distinguishing features concern the dental structure.
"Mylodon" was a terrestrial ground sloth. A thick coat with long hair can be interpreted as an adaptation to a life under cold climatic conditions, as they prevailed in southern South America during the last glacial period. A diet based predominantly on grasses also corresponds to this in this region. The widespread distribution of "Mylodon" into the pampas region and some features on the skull show, however, that the animals had a much larger ecological range and could also cope with warmer temperature conditions and possibly a mixed vegetable diet. Some of the animals fell victim to larger predators.
The genus was described in 1840, and only one species, "Mylodon darwini" is usually recognized. The type material comes from the area of the Pampas, where it was collected by Charles Darwin during his voyage with HMS "Beagle". "Mylodon" was one of the first extinct sloths on which genetic studies were carried out.
Discovery.
"Mylodon" was named by Richard Owen on the basis of a nearly complete lower jaw with teeth, which was found by Charles Darwin in a consolidated gravel cliff at Bahía Blanca, during the survey expedition of HMS "Beagle". At several sites preserved hide and dung have been discovered, and are in such a state of conservation that the people who first discovered them believed they belonged to a living animal instead of an extinct species. The discovery of fresh-looking samples of skin and dung sparked a small wave of expeditions during the early 20th century to search for a living example of the animal. The samples have since been found to be around 10,000 years old, although they look fresh because of the extreme cold and stable conditions in the caves in which they were found.
Fossils assigned to "Mylodon" have also been found in the Ñuapua Formation of Bolivia. Well preserved samples of "Mylodon" remains have been discovered in the Cueva del Milodón site in Patagonia, Chile along the southern flank of Cerro Benítez in the year 1896. Associated with bones of other early Patagonian animals, these remains of "Mylodon" date from an era earlier than 10,000 BC. The American Museum of Natural History has exhibited a sample of "Mylodon" dung from Argentina with a note that reads "deposited by Theodore Roosevelt".
Description.
General.
"Mylodon" was a large representative of the Mylodontidae. Its total length was estimated to be around 3 to 4 m. Based on the size of the skull, a weight between 1 and 2 tonnes is assumed, with an approximate estimate of 1.65 tonnes. Thus, "Mylodon" had about the size of related forms such as "Glossotherium" or "Paramylodon", but was significantly smaller than the giant "Lestodon". In terms of physique, it largely corresponded with the other large ground-living sloths.
Skull and dentition features.
Especially in the construction of the skull, "Mylodon" differed significantly from other related forms. Its length varied between 59 and 71.5 cm, which is significantly longer than "Glossotherium" or "Lestodon". At the skull it was between 16.5 and 22.5 cm wide, in the front nasal area between 11.3 and 15.5 cm. The height of the posterior skull was 14.0 to 19.0 cm and the anterior 15.0 to 23.5 cm. The skull was thereby elongated and narrow, unlike "Glossotherium" and "Lestodon" that had a short and very broad skull. The extraordinary length of the skull of "Mylodon" was mainly due to elongations in the rostrum. Seen from above, the rostrum narrowed towards the front. This is where the most important difference to most of the other representatives of the Mylodontidae can be found: The nasal bone was long and narrow and curved downwards in the front area. At the front end, it connected to the middle jawbone, which was lengthened by an appendage, and which in turn fused with the upper jaw. This resulted in a completely closed nasal arch in adult individuals, which is largely unknown in other sloths. In comparison, the skulls of "Glossotherium" and "Lestodon", but also of "Paramylodon", showed a nasal area, seen from above, which was rather short and looked clearly cut off when viewed from the side; the roof of the skull was largely straight in "Mylodon", only a slight indentation could occur above the orbit. On parietal, significant temporal lines were present, but no head crest formed. The zygomatic arch was slim, the anterior attachment began above the third and fourth molars. It did not form a solid end with the rear arch attachment. As is usual with sloths, the front arch base consisted of three appendages: one ascending, one horizontal, and one descending, the former of which was the longest. The rear arch formed a triangular plate. The occiput bent at an angle of 120° from the roof of the skull. The underside of the occiput was at about the level of the occlusal plane. When viewed from behind, the occiput appeared almost circular and not as depressed as in "Glossotherium" and "Lestodon". The palate was narrow and was more or less triangularly oriented towards the front of the skull. Numerous small bone openings were characteristic here. The glenoid pit, in which the joint of the lower jaw engages, corresponding to that of other mylodonts with its weak form, but this provided free rotation overall.
The lower jaw of "Mylodon" varied in length between 42 and 48 cm. It was elongated, more noticeable than in "Glossotherium" and "Lestodon", since in "Mylodon" the area in front of the teeth, in particular, is strongly elongated. The horizontal bone body increased continuously in height towards the rear, below the last molar it was about 10.5 to 12.7 cm. The symphysis at the front end for the jointing of the two halves of the lower jaw was about 12.4 cm long. Here the lower edge of the body of the lower jaw rose at an angle so that the anterior end of the symphysis was above the occlusal plane of the teeth. As with other sloths, the symphysis extended forward, it ended slightly rounded. According to the rostrum of the skull, "Mylodon"'s symphysis was narrow and not as wide as in "Glossotherium" and "Lestodon". The mandible foramen opened shortly behind the symphysis. The ascending branch started behind the last molar and formed an angle of 140° to the occlusal plane. The crown process rose up to 20 cm. In contrast, the articular process was lower, roughly at the level of the occlusal plane, resulting in a low cranial-mandibular connection. The angular process at the rear end of the lower jaw was clearly visible. Sometimes it tipped down and was below the lower edge of the horizontal bone body. The upper side of the angular process does not reach the occlusal plane.
The dentition of "Mylodon" differs greatly from that of the other placental mammals and usually consists of five teeth at the top and four teeth at the bottom per jaw arch, meaning a total of 18 teeth. In the mylodonts, the first tooth was often caniniform while the rear teeth were more molariform. Within the sloth, this structure of the teeth can be called original. A special feature of "Mylodon" was that the upper canine-like tooth of each row was completely regressed and only the molar-like four rear teeth were found here. In the lower row of teeth, the anterior caniniform tooth was transformed into a molariform. The dentition thus consisted of a total of 16 teeth. This is somewhat reminiscent of "Paramylodon", in which the upper canine-shaped teeth were also missing, but the lower ones had retained their strikingly pointed shape. In contrast to this, "Glossotherium" and "Lestodon" had the original decayed teeth. The flat, flap-like and largely indented structure of the " molariform " teeth can be emphasized as a characteristic of the mylodonts, which clearly differs from that of the Megatheriidae and Megalonychidae with their two transverse raised ridges per tooth. The shapes of the teeth present in "Mylodon" were simpler. In the upper jaw row, they had a rather round to oval outline, in the lower jaw row a more diamond-shaped outline. The typically more complex bilobed design of the molar-like teeth of " Glossotherium " and " Lestodon ", caused by a central constriction, only occurred on the lower rearmost tooth in "Mylodon". In general, the rows of teeth diverged to the front, and the teeth were very high crowned (hypsodont). The upper row of teeth ranges in length from 10.9 to 13.3 cm, the lower row was between 12.0 and 15.0 cm in length.
Postcrania.
Postcranial skeletons are far rarer in "Mylodon" than in the other large mylodontid sloths. As a result, the skeleton is less well documented. Only individual elements of the spine, such as the atlas and various thoracic vertebrae, have been described. The humerus was massive and extremely long at 46 to 48 cm. The joint head, the diameter of which was over 10 cm, stood out due to its hemispherical, but laterally somewhat flattened shape. A distinct deltopectoral ridge ran down the shaft, which acted as an anchor point for the shoulder muscles. As with many ground sloths, the lower end of the joint extended far and brought it here to a width of almost 26 cm. In part, this was caused by a massive internal epicondyle. The articular surfaces (capitulum and trochlea) were almost perpendicular to each other and did not form such an obtuse angle as in "Glossotherium". The cubit was built gracefully. Their length was around 37 cm. The olecranon, i.e. the upper articular process, took up about 8.1 cm of it, which corresponds to about 22% of the total length and is significantly less than in comparison with "Glossotherium" and "Lestodon". It was laterally narrowed, which is also found in "Paramylodon". The spoke largely resembled that of Glossotherium and was compact and straight built with a length of about 30 cm. The head was oval in shape with a prominent lip. The pelvis was extremely expansive and 114 cm wide between the two iliac bones. The thigh bone measured between 55 and 59 cm in length. It was typical of ground sloths, being flat in shape. Its width decreased significantly on the shaft, the lowest value was reached just below the midpoint. Here the width was about 18 cm, the thickness about 7.5 cm. The joint ends, on the other hand, were markedly wider, around 30 cm at the knee end and around 26 cm at the foot end. The thighbone reached the shin with only about half of its length, a characteristic of mylodonts. This bone, too, was clearly flat with a thickness that was only half the value of the width at the shaft. The fibula is so far only fragmented. It was drawn in on the shaft and widened at the joint ends, with the upper joint end showing more pronounced curves than in "Glossotherium".
The hand comprised a total of five digits (I to V), whereby the metacarpal bone was fused with the large polygonal bone on the first digit. This created the so-called Metacrapal Carpal Complex (MCC for short), which is typical for many ground sloths. As a special feature of the wrist, the pea bone was clearly flat, its shape resembled that of "Glossotherium", but differed from the corresponding bone of other Mylodonts with spherical, walnut-like or a pyramidal shape. The fourth digit had formed the longest metacarpal bone, while that of the fifth was only slightly shorter. The respective bones measured there around 12.5 and 10.7 cm in length. As with "Glossotherium" and "Paramylodon", only the three inner digits were probably clawed, but only of the second digit have all bone elements been documented. The metacarpal bone was 7.8 cm long and was built very gracefully. The first phalanx was extremely short and only about 2.5 cm long, the second was about 4.2 cm long and the third at least 11.5 cm. It was tubular and went forward into an extension on which the claw rested. The first phalanges of the two outer digits were significantly reduced in length. Only individual root bones of the foot, such as the talus, are present.
Integument.
"Mylodon" is one of the few extinct mammals that has mummified skin remains. The most important location for such finds is the Cueva del Milodón in the Chilean province of Última Esperanza, where the first skin parts were brought to light at the end of the 19th century. Individual pieces have lengths of up to 150 cm, but have shrunk through drying processes. Its thickness is up to 1.5 cm in some places, but it is usually around 1 cm. The skin is densely covered with stiff, slightly wavy hair, with only the top hair being developed, while the undercoat is missing. This feature is similar to the two-toed sloths but less so than the three-toed sloths), which possess an undercoat. The length of the individual hairs vary between 5 and sometimes over 20 cm with the shortest in the area of the back of the head, medium-length hair on the back and very long hair on the limbs. Their known color ranges from yellowish to reddish-brown. The hair shafts are uniformly tubular, at the upper end they form blunt tips. As with today's sloths, the hair did not have a pith (medulla). In contrast to the hair of the two-toed sloth, they lack their characteristic longitudinal ribbing.
The mylodonts are the only representatives of the sloths to have bony plates embedded in their skin. Such structures, called osteoderms, are known today to a greater extent only in armadillos. In contrast to the outer armor of the armadillos, the bone platelets of the Mylodonts were rather loosely scattered. Hermann Burmeister published the first finds of individual osteoderms of "Mylodon" as early as the 1860s. The remains of skin found in the caves of Última Esperanza give an impression of how they were embedded in the skin and distributed over the body. The bone platelets are all located in the lower section of the skin, while the hairs originate in the upper sections. The distribution turned out to be very inconsistent. Some areas with a dense array of osteoderms contain between 83 and 95 platelets per 10 cm². For others, however, the number is very thin. However, even with a close arrangement, the osteoderms never unite to form a closed shell, but are always separated from one another by individual skin folds. In accordance with the armadillos' shells, the bone platelets form a single layer and do not appear stacked. Since all skin residues were found isolated from the body skeletons, it is sometimes difficult to assign the skin areas with a dense and thin arrangement of bone platelets to a specific part of the body. However, it can be assumed that the back was largely armored and the stomach was free. In the sections with dense osteoderm formation, these were larger than in the clear areas. The bone platelets of "Mylodon" were mostly of irregular oval shape with dimensions of 0.5 to 2.5 cm in length, 0.3 to 1.8 cm in width and 0.2 to 1.1 cm in thickness, with weights of a maximum of 2g. On the surface, they showed individual dimples. In cross-section, they consisted of numerous bundles of fibers mixed with hard bone blades ( osteoma ). This made their structure much simpler than that of the armadillos, and they probably lacked the keratin layer known from the armadillos. In principle, the osteoderms of "Mylodon" were similar to those of other large mylodonts.
Distribution and important fossil finds.
Overview and origins.
"Mylodon" was mainly distributed in the southern part of South America. Fossil finds are available from Argentina, Chile, Bolivia, Uruguay and Brazil. Thus, the colonized regions include very far southern sites on the island of Tierra del Fuego as well as most of Patagonia northward to the Pampa region. Its southern limit reached the range at about 53° southern latitude. The Tres Arroyos site on Tierra del Fuego and the region around Cueva del Milodón in southwestern Patagonia are among the southernmost known records of a sloth representative in the Pleistocene. In the Pampa region, the northern limit was found approximately at the Chuí River in the southeastern Brazilian state of Rio Grande do Sul around 30 degrees south latitude. Even more northerly points of discovery, such as Ñuapua in Bolivia, are tangent to the 20th parallel south. Finds reported from Paraguay, however, are considered rather uncertain.
The first occurrence of "Mylodon" may have been in the Lower Pleistocene, but finds are rather rare. During this period, the possibly closely related form "Archaeomylodon" also occurred in the Pampas region, whose foremost canine teeth of the upper dentition were greatly reduced in size, but not yet completely reduced. Among the early and more northerly finds of "Mylodon" is, for example, a skull from the El Palmar Formation in the Argentine province of Entre Ríos, which dates to the end of the last warm period about 80,000 years ago. Also from the northern distribution areas two partial skeletons are worth mentioning, one of which was found at the Río Anisacate in the Argentine province of Córdoba and the other in Arroyo Quequén Salado near Oriente in the Argentine province of Buenos Aires. Mainly in the Pampas, there was an overlap in the occurrence of "Mylodon" with the two other major mylodontid sloth representatives "Glossotherium" and "Lestodon" during the Upper Pleistocene. However, actual co-occurrence is rarely attested. These include the important archaeological site of Paso Otero in Buenos Aires Province, the locality of Arroyo de Vizcaíno in southern Uruguay, and the Chuí River.<ref name="farinaetal2014"/
Important Upper Pleistocene finds.
As with many of the other large ground sloths, most of the "Mylodon" material is from the Upper Pleistocene, with a focus toward the end of the last glacial period. It is also the phase when "Mylodon" again disappeared from the fossil record. From a global perspective, numerous larger animals became extinct during the transition from the Pleistocene to the Holocene, which is why this event is considered a Quaternary extinction wave. In South America, this coincides with the first appearance of humans. Whether the two are causally related is the subject of much controversy. In addition to potential hunting and possible landscape overprinting by early human hunter-gatherer groups, climatic changes may also have had an influence.<ref name="villavincencioetal2016"/ Numerous archaeological sites, especially in the Pampa region and in the Patagonian area, are between 13,500 and 10,000 years old. The majority of these attest to at least a coexistence of humans and ground sloths over an extended period of time. Direct associations of human cultural products and fossil remains of "Mylodon" are found, among others, at Gruta del Indio in the eastern foothills of the Andes, at Piedra Museo or Las Buitreras, all in Argentina, and at Tres Arroyos in Tierra del Fuego, respectively.
"Mylodon" is often represented by isolated osteoderms, bones or in the form of coprolites, while human remains are limited to stone artifacts and/or hearths. Whether this also involved a more or less intensive raw material use of sloth bones on the part of humans is in many cases unproven. Numerous bone marks that were originally interpreted as anthropogenically caused are, according to recent studies, due to predation. Evidence of direct hunting by humans of the large ground sloths is even more difficult. One piece of evidence is often considered to be Quebrada de Quereo, a site on an ancient coastline in northern Chile. From here come, among other things, skeletal remains of two individuals of "Mylodon", distributed in each case over a narrowly defined area, but in two different stratigraphic units and at a spatial distance of 21 m from each other. One of the individuals was associated with about 70 stone objects, whose anthropogenic origin is under discussion. No cut marks are found on the bones as evidence of any human manipulation. The age of the site is given as 11,600 to 10,900 years before present.<ref name="jacksonetal2003"/<ref name="borrero2009elusive"/
One of the most important sites is the Cueva del Milodón near Lago Sofía in the Chilean province of Última Esperanza, known mainly for its surviving skin remains. It is part of a whole system of caves in the region, such as the Cueva del Medio<ref name="Martin et al. 2015"/<ref name="Nami et al. 2015"/ or the Cueva Chica,<ref name="Martin et al. 2013"/> which line the southern flank of the 556 m high Cerro Benitez like pearls. Cueva del Milodón is a large cave 250 m long, 140 m wide and 30 m high at the entrance and 10 m at the back, respectively. It was discovered in 1895 by the German captain Hermann Eberhard, who also found the first skin remains. The great importance of these finds led to the cave, initially known as "Cueva Eberhardt", being subsequently visited and explored by numerous scientists. As a result, a large number of finds accumulated over time, among which "Mylodon" with bone remains, and numerous coprolites has a large share. Other finds belong to camelss such as "Lama", horses such as "Hippidion" or South American ungulates such as "Macrauchenia", in addition, several predators are represented, including the jaguar, "Smilodon" as a member of the saber-toothed cats, and the giant bear form "Arctotherium". Some of the mammal bones have marks that were originally associated with human activity, but the current view is that they are more likely due to predator browsing. In addition to faunal remains, the cave also held a myriad of botanical material. It also yielded one of the most extensive data sequences from the Upper Pleistocene. Several radiocarbon dates, measured from a wide variety of "Mylodon" finds, span a period from about 16,700 to 10,200 years ago. The upper data are among the most recent obtained directly from finds of the sloth vertebrate.<ref name="Tonni et al. 2003"/<ref name="Barnosky et al. 2010"/<ref name="Borrero et al. 2012"/
Taxonomy.
"Mylodon"'s close relatives include the ground sloths of the genera "Glossotherium" and "Paramylodon". The latter genus has often been confused with "Glossotherium", but "Paramylodon" is a distinct genus that was restricted to the Pleistocene of North America. "Glossotherium" also shares a long history of taxonomic confusion with "Mylodon", and currently the only recognized species is "Mylodon darwini". At one time, the elephant-sized "Megatherium" was thought to be closely related, but is recognized as belonging to a separate family (Megatheriidae).
Below is a phylogenetic tree of the Mylodontidae, based on the work of Boscaini and colleagues (2019).
Recent molecular sequence results obtained using collagen and mitochondrial DNA extracted from fossils indicate that the closest living relatives of "Mylodon" are the two-toed sloths of genus "Choloepus". This revelation came as a surprise, since morphological analyses had previously suggested that two-toed sloths were close to Caribbean sloths and "Megalonyx", now regarded as representing two separate and distant branches of the sloth evolutionary tree.
History of research.
First description.
The taxonomic history of "Mylodon" is complex. It has involved confusion and equivocation with other mylodont forms such as "Glossotherium" and "Paramylodon" over a long period of time. Some of this complexity can be attributed to the first describer of the genus itself, who is Richard Owen (1804-1892). Owen, one of the most important explorers of the Victorian era, was concerned from 1836 with fossil finds brought back by Charles Darwin from his pioneering voyage on the HMS "Beagle" to South America. The collection also included a mandible from Punta Alta near Bahía Blanca in the south of the Argentina Buenos Aires Province (specimen number NHM 16617). The nearly complete specimen was distinguished by a row of teeth consisting of a total of four molar-like Teeth. In an extensive 1840 paper, Owen referred the mandible to the new genus he had created, "Mylodon," and named the species "M. darwinii" ("darwinii" is the spelling used by Owen, but in modern times "darwini" is also often used; according to the Regulations of Zoological Nomenclature, the former version is correct.<ref name="Iuliis et al. 2017"/) He related the genus name to the molar-like teeth (from Greek "μυλη" ("myle") for "molar" and "ὀδούς" ("odoús") for "tooth", thus translating as much as "molar tooth"), with the species epithet "darwinii" honoring Darwin as finder of the voucher specimen. As a second species besides "M. darwinii" Owen referred in his paper to "M. harlani". This form was based on a mandible and clavicle, both of which came from the Big Bone Lick in Boone County in the U.S. state of Kentucky, and which Richard Harlan had already described in 1831 under the species assignment "Megalonyx laqueatus".<ref name="Harlan 1831"/ Owen, however, recognized similarities in the construction of the mandible to his "M. darwinii" and renamed Harlan's form.<ref name="Owen 1840"/ Harlan used an essay two years later to comment on Owen's choice of name regarding "Mylodon," which he felt was not very descriptive. According to him, the name could be applied to almost any extinct mammalian form because almost all of them had the posterior molars. Moreover, the name would be inappropriate because, starting from the Latin version "dens molaris" for "molar tooth" and the second part of speech "don" (from "dens" for "tooth"), there is a duplication that would translate as "molar tooth-tooth".<ref name="Harlan 1842"/ Regardless, Owen's establishment of the genus "Mylodon" with two species resulted in the extinct sloth representative being distributed in both South and North America.<ref name="Fernicola et al. 2009"/<ref name="Vizcaino et al. 2009"/
"Glossotherium", "Grypotherium" and "Paramylodon".
Owen, in his 1840 work, established the genus "Glossotherium" in addition to "Mylodon", but without designation of a specific species. The basis here was a posterior skull fragment taken from the riverbed of the Arroyo Sarandi in the Uruguay department of Soriano. In contrast to "Mylodon", for which Owen assumed a kinship proximity to the other large ground sloths known at the time, such as "Megatherium" or "Megalonyx", he placed "Glossotherium" in a series with the anteaters and with the pangolins, respectively, and postulated an insectivorous lifestyle for the animals. Two years later, however, Owen discarded the name "Glossotherium" again. This occurred in the course of processing a nearly complete skeleton that had been discovered the year before in the flood plains of the Río de la Plata north of Buenos Aires. The largely intact skull was characterized by a short and broad snout and by a dentition consisting of a total of 18 teeth, of which the foremost tooth in each case showed a canine design. Based on the similarities in dental structure with the flat, molar-like teeth, Owen placed the skeleton in the genus "Mylodon" and introduced the new species "M. robustus." The skull fragment that he had originally placed in "Glossotherium" he now associated with "M. darwinii".<ref name="Owen 1842"/ As a result of this study, three species of the genus "Mylodon" already existed in the 1840s.<ref name="Fernicola et al. 2009"/><ref name="mcafee2009"/
A skull including mandible found at Pergamino in Buenos Aires Province served the Danish zoologist Johannes Theodor Reinhardt (1816-1882) in 1879 as the basis for a comprehensive description. Characteristic of the skull was the narrow snout and a closed nasal arch, which was formed by the firm adhesion of the nasal bone to the middle jaw bone. Furthermore, the dentition consisted of a total of 16 teeth, the upper front canine-like tooth was reduced in each case, in the lower jaw, however, sat four molar-like teeth each. Reinhardt noticed similarities to "M. darwinii" in the construction of the lower jaw, but in the skull design his find deviated clearly from the broad-nosed "M. robustus" by the narrow snout. However, according to Reinhardt, there were matches in Owen's "Glossotherium" skull fragment with corresponding skull sections in "M. robustus". Based on the clear parallels between "M. darwinii" and his narrow-beaked skull finding, Reinhardt propagated the new genus "Grypotherium" with "Grypotherium darwinii" as the type species.<ref name="Reinhardt 1879"/ A different approach was taken by Florentino Ameghino (1854-1911) about ten years later. He confirmed in 1889, the separation of both "M. darwinii" and "M. robustus" not only at the species level, but also at the genus level. Deviating from Reinhardt, but agreeing with Owen, he considered the mandible of "M. darwinii" and the skull fragment of "Glossotherium" to belong together. Since in this scenario "Glossotherium" possessed priority over "Mylodon" (Owen mentioned the former over the latter in 1840) and "Grypotherium," Ameghino introduced the species "Glossotherium darwinii." In contrast, he left the status of "M. robustus" untouched.<ref name="Ameghino 1889"/ Arthur Smith Woodward (1864-1944), in turn, followed Reinhardt's reasoning. In a paper published in 1900, he presented findings from ground sloths of southern Patagonia and at the same time revised Charles Darwin's collection. In doing so, he equated the mandible of "M. darwinii" with Reinhardt's "Grypotherium" and subsequently recovered "Grypotherium darwinii". Smith Woodward assigned the skull fragment of "Glossotherium" to "M. robustus" by analogy with Reinhardt.<ref name="McDonald 1995"/
Paleobiology.
Diet.
The mylodontids (particularly "Mylodon" itself) are often considered to be pronounced grazers because of their dental structure with flat chewing surfaces on the molar-like teeth. This is also supported by the high (hypsodont) tooth crowns and the wide mouth with numerous shapes. The ungulates are mostly used as analogous examples, in which shapes with high tooth crowns and broad-lipped mouths are usually grass-eating, such as various cattle, horses or the white rhinoceros. In contrast, those with low tooth crowns and narrow snouts such as the duiker or the black rhinoceros feed largely selective from various leaves and other soft vegetable foods. In contrast to other large mylodontid sloths such as "Glossotherium", "Paramylodon" or "Lestodon", the mouth of "Mylodon" is relatively narrow. A special feature is the closed nasal arch, which is heavily roughened in its front area and thus offers muscle attachment points for a mobile upper lip. Something similar can be said about individual depressions in the vicinity of the infraorbital foramen, which also functioned as starting points for individual muscle strands in the nose and lip area. Maybe "Mylodon" was more well-adapted to a mixed-vegetation diet, which was picked up with the help of a movable upper lip. The loss of the front teeth in the upper row of teeth also leads to the assumption that, comparable to cattle, there was a horn-like structure on the middle jawbone that could be used to pluck the food.
The entire anterior cranial structure of "Mylodon" is relatively solid, combined with a partially ossified nasal septum, it can be assumed that relatively high chewing forces acted when the food was chopped up. In contrast to the sometimes huge representatives of the Megatheriidae, the joint between the lower jaw and the skull of the Mylodonts was relatively low, roughly at the chewing level of the teeth. The resulting decreasing lever arm of the masseter muscle experiences through the structure of the zygomatic arch, mainly of the descending process, a certain compensation, so that there should have been only minor differences to the Megatheria with regard to the biting force. The extended mandibular joint allows a wide freedom of movement when chewing. Against this, however, is the zygomatic arch, which is not closed and therefore could only withstand the opposing forces of the masseter and musculus pterygoideus to a limited extent. It can therefore be assumed that forwards and backwards directed chewing movements dominated in "Mylodon". The flat tooth crowns lead to a comparatively small size of the total available chewing surface. In "Mylodon", this amounts to a good 1320 mm² corresponding to other mylodonts of the same size. The Indian rhinoceros, which is comparable in terms of its dimensions, has, on the other hand, double to four times the value with 2660 to 5190 mm². The situation is similar with the hippopotamus, the total surface area of which is between 3290 and 5410 mm². The small total occlusal surface of the teeth in "Mylodon" probably resulted in a rather low processing capacity for the food in the mouth. This can result in either a high rate of fermentation in the gastrointestinal tract and/or a very slow metabolism concluded. The latter is the case with today's sloths. This is due to the long passage time of the food of up to a week through the large, multi-chambered stomach. It can be assumed that this also applies to the extinct sloths. Possibly this made the stomach of the mylodonts a functional equivalent to the complex stomach of the ruminants, whereby a long passage time of the food enabled efficient digestion, in which even more difficult to access nutrients could be provided, for example from foods with a greater fiber content. Such a digestive system could reduce the amount of processed food in the mouth and thus ultimately also the small total sales area with Mylodonhave balanced.
Direct analysis of the food resources used is possible, among many other things, due to the numerous dung residues in the form of coprolites. These are available not only from the Cueva del Milodón in the Chilean part of Patagonia, but also from other caves. The coprolites of "Mylodon" have a diameter of up to 18 cm. Investigations of the plant residues showed 80 to 95% sweet grasses and 5 to 20% sour grasses. Herbaceous plants, on the other hand, could only be detected in traces. Accordingly, "Mylodon" led, at least in southwestern Patagonia, a diet consisting almost exclusively of grasses. The food is reflected in the paleohabitat, as pollen analyzes show that the landscape at that time was tundra-like in character and was therefore almost free of trees with only a few low bushes. Occasional evidence of false beeches is interpreted as pollen carried by the wind.
Locomotion.
In general, large mylodonts are ground-dwelling animals. The lower section of the hind leg, which is very short compared to the upper, is also found in "Mylodon", whose tibia is 27 cm in length and only half as long as the thigh bone, 59 cm in length. In comparison, the Megatheriidae possess significantly longer lower leg portions, about the almost equally-proportioned "Pyramiodontherium" possessing to a 47 cm long shin to a 49 cm long femur. Possibly these differences in the hind leg structure result in much more agile locomotion in the Megatheria in relation to the mylodonts. Similar to other large ground sloths, the hand of "Mylodon" made contact with the ground with the outer side edge and thus sat up rotated. This is indicated by the long metacarpal bones of the external digits and the decreasing number of phalanges on them. The special hand position protected the long claws of the inner digits, which did not penetrate the ground while walking. A functionally similar but fundamentally different hand position can be found in the ankle duct of the distantly related present-day great anteater. The elbow joint was pointed slightly outwards when standing on four feet and the arms were thus angled slightly inwards, which is evident from the position of the olecranon yields. The hands came to rest slightly within the width of the elbow. Such an orientation of the arms can effectively support the large mass of "Mylodon". As a result, the hands would also be in a line with the feet, which is also conveyed, among other things, by footprints from "Paramylodon". The laterally limited articular surface of the femoral head severely restricted the mobility of the hindlimbs. The same applies to the forearm, the straight spoke with the laterally elongated head of which did not allow any major rotational movements. These features can be interpreted as adaptations to a purely terrestrial lifestyle. Finally, the muscle attachment points on the first cervical vertebra referenced, which are more developed than for example with "Paramylodon". Correspondingly, the occipital joint surfaces are also somewhat further apart. Both can be interpreted as meaning that the more massive skull of "Mylodon", caused by the lengthening of the snout region, required greater muscle support.
For some of the mylodonts of South America, such as "Glossotherium", a partially burrowing way of life is being reconstructed, which results from the construction of the foreleg, among other things. An indicator for this is the upper articular process (olecranon) of the ulna. The longer the olecranon, the higher the leverage of the forearm, since more attachment surface is available for the forearm muscles. In "Glossotherium", the olecranon takes up up to 35% of the total length of the ulna. The resulting ability to dig would be comparable to that of the "Tolypeutes" armadillos, which seldom build their own burrows, but can do so. The previous analyses for "Mylodon" resulted in a much shorter olecranon, which accounts for only about 22% of the total length of the ulna. However, the fact that proportional estimates for "Mylodon" refer to a not fully grown specimen is problematic. Other clues can be derived from the construction of the hand. In "Mylodon", for example, the metacarpal bones of the second and third ray are very delicate, in contrast to "Glossotherium". A weakly pronounced central ray does not seem to support a digging activity, as this is usually most strongly developed in underground mammals. However, the distal articular facet of the third metacarpal bone is flat, which means that the middle finger is generally stiff and stable. The same articulation surface on the second metacarpal is significantly more rounded and thus supports greater mobility of the finger when gripping. This obviously resulted in functional differences between the individual rays of the hand. The rare signs of wear and tear on the last phalanx, which are isolated from the Cueva del Milodón several times, can serve as an additional indicator of digging activities.
Predation and Parasites.
Especially in southern and southwestern Patagonia, numerous bone changes in finds of "Mylodon" can be proven to be caused by predatory animals. This includes, above all, the remains from the Cueva del Milodón in southwestern Chile. Some caves in their immediate vicinity, such as Cueva Lago Sofía 4 and Cueva Chica, are interpreted as clumps of predators. The same applies to the Cueva del Puma or the Cueva Fell in the Pali-Aike area of southern Chile. Some of the caves mainly contain smaller skeletal elements such as hand and foot bones or bone plates, which indicate that only part of the carcass was carried into the shelter. Whether this is the result of direct foraging or scavenging cannot be determined in many cases. Other caves, in turn, contained a larger proportion of young "Mylodon" animals.<ref name="borrero2009"/ The largest predators occurring at that time are the puma and the jaguar, as well as the saber-toothed cat "Smilodon populator" and the extinct bear "Arctotherium". The latter two could have reconstructed body weights of over 400 kg, with prey sizes between 1 and 2 t being assumed for the saber-toothed cat, which makes "Smilodon" a likely predator of "Mylodon".
In various coprolites produced by "Mylodon", eggs of nematodes are preserved. The eggs are ovaloid in shape with lengths of almost 50 µm in length and 29 µm in thickness. In addition, individual beetles could be detected.


Rhynchaeites

Rhynchaeites is an extinct genus of Threskiornithidae related to modern ibises and has a single named species Rhynchaeites meselensis. It lived in today's Germany during the mid-Eocene and its remains were found in the famous Messel pit.
However, leg bone fossils of a similar bird were found in the Early Eocene Fur Formation in Denmark. It has been hypothesized that the supposed parrot relative "Mopsitta tanta", known from a single humerus bone, is the same bird as the leg fossils and thus actually belongs in "Rhynchaeites" too.


El Mogote

El Mogote is a sand barrier peninsula opposite the city of La Paz in Baja California Sur, Mexico. The peninsula forms the northern shore of the Bay of La Paz. The peninsula is arid, with extensive dunes at its neck. Clusters of mangroves are established on the southern shore of the peninsula. The mangroves are considered important habitat for local and migratory birds, as well as marine life and are listed under the Ramsar Convention.
Paraiso del Mar.
El Mogote is the location of Paraiso del Mar, a resort development on on the eastern portion of the peninsula. The development, begun in 2005, was planned to include over 3,000 homes and condominiums, two golf courses, a marina, a town plaza and various other amenities. Land acquisition and development began despite concerns that the project would damage the ecology of the peninsula and surrounding waters.
In August 2011, the developer, Luis Raymundo Cano Hernández, abandoned the project. In October 2012, he abandoned operation of the golf course. As of 2014 the new owner of the development was searching for a buyer.
There are approximately 170 owners who have formed an HOA to manage the property. There are 91 homes built and 120 condo units. There is one golf course, also currently operated by the HOA and it is open to the public, under the name "The Golf Club at El Mogote". Potable water is provided by a desalination plant.
There are two methods of access to the development; an unpaved road, and a scheduled ferry from the La Paz malecon.
Portions of the partly completed development have been described as an eyesore. As of 2013 Mexican federal courts had ruled the development illegal and had directed all further development to cease.


Red Beach (Santorini)

Red Beach is a volcanic sand beach on the Aegean island of Santorini. The beach is famed for its titular red-hued sand, and is a noted for being popular tourist attraction.
Description.
The beach's sand is composed of black and red pulverized volcanic rock from the nearby Santorini caldera. Red Beach can be accessed from nearby Akrotiri. The area is prone to landslides, and since 2013 parts of the beach have been inaccessible due to said slides.


Lonquimay (volcano)

Lonquimay Volcano is a stratovolcano of late-Pleistocene to dominantly Holocene age, with the shape of a truncated cone. The cone is largely andesitic, though basaltic and dacitic rocks are present. It is located in the La Araucanía Region of Chile, immediately SE of Tolhuaca volcano. Sierra Nevada and Llaima are their neighbors to the south. The snow-capped volcano lies within the protected area Malalcahuello-Nalcas.
The volcano's last eruption began on December 25, 1988, earning it the nickname "Navidad". The eruption lasted for 13 months before ending in 1990. The Volcanic Explositivy Index was 3, indicating tropospheric injections and catastrophic damage. The eruption was from a flank vent and involved mostly andesite lava, and had been preceded by increased seismicity for three weeks. The volume of the lava flow decreased as time went on and the vent dimensions decreased, though by the end of the eruption the andesite had still built up to a length of 10.2 km.
There was only a single fatality for the duration of the eruption, but it caused the evacuation of over 2000 people and caused extensive damage to farming and livestock in the surrounding region.
Research that models the internal architecture of the volcano indicate that Lonquimay has reached its maximum height and that any large eruption of lava will likely occur from flank vents and not from the summit.


Gogolin Formation

Gogolin Formation - Triassic geologic formation, hitherto named the Gogolin Beds, is the lowermost lithostratigraphical unit of the Lower Muschelkalk in the Silesian-Cracow Upland (S Poland, Central Europe), underlain by the Upper Buntsandstein (Lower Triassic) carbonates and overlain by the Górażdże Formation (Middle Triassic) carbonates.
Name.
Historical name coming from Gogolin, a small town in south Poland, where the Gogolin Formation was described for the first time, and where the main stratotypes have been exposed (see section Stratotypes).
Age.
The Late Olenekian or Early Aegean (Anisian) to Pelsonian (Anisian).
Rocks.
The formation is built of various carbonates which were deposited on a carbonate ramp.
Subdivision.
This Formation has recently been divided into four members, six beds, and two horizons:
Stratotypes.
Stratotypes are located at Gogolin and its vicinity, Błotnica Strzelecka and Ligota Dolna (southern Poland).


Sierra de Sangra

Sierra de Sangra is an extinct ice-clad stratovolcano with its summit located 10 km east of Villa O'Higgins. The volcanic masiff is heavily eroded and constitutes part of the Argentine-Chilean border in Patagonia.


Afrops

Afrops larvifer ("Eye of Africa bearing a mask") is a phacopid trilobite which lived in a marine environment during the Pragian stage in what is now southwestern Algeria. The holotype and only known specimen is an incomplete cephalon that was described by G. Alberti in 1983.


Hides gas field

The Hides gas field is a natural gas field located in the Hela Province of Papua New Guinea. It was discovered by BP in 1987 who relinquished their interest, and later developed by ExxonMobil. It began production in 1988 and produces natural gas and condensates. The total proven reserves of the Hides gas field are around 7.1 trillion cubic feet (203×109m³), and production is slated to be around 100 million cubic feet/day (2.9×105m³) in 2010.


Progalesaurus

Progalesaurus is an extinct genus of galesaurid cynodont from the early Triassic. "Progalesaurus" is known from a single fossil of the species "Progalesaurus lootsbergensis", found in the "Lystrosaurus" Assemblage Zone of the Balfour Formation. Close relatives of "Progalesaurus," other galesaurids, include "Galesaurus" and "Cynosaurus". Galesaurids appeared just before the Permian-Triassic extinction event, and disappeared from the fossil record in the Middle-Triassic.
The name “Progalesaurus” is derived from Greek, “pro” meaning before, “gale” meaning weasel or cat, and “saurus” meaning lizard or reptile (Sidor and Smith). The name refers to the relationship "Progalesaurus" has to the more derived "Galesaurus."
Discovery and history.
"Progalesaurus" was originally discovered by Roger M. H. Smith in 1998. The specimen was found in the Sneeuberg mountains near New Lootsberg Pass in the Karoo Basin of South Africa. "Progalesaurus" was first described in 2004 by Christian A. Sidor and Roger M. H. Smith in their paper titled, “"A New Galesaurid (Therapsida: Cynodontia) From the Lower Triassic of South Africa.”"
Although no other specimen of "Progalesaurus" has been found as of yet, Sidor and Smith's findings have been included in many papers on the Permian-Triassic extinction event, cynodont diversity, and the paleoenvironment of South Africa.
Description.
"Progalesaurus" was a relatively small mammal-like creature, with the skull of its holotype measuring 9.35 cm in length. It likely closely resembled its early cynodont relatives, walking on four legs and covered in fur.
Skull.
"Progalesaurus," like "Galesaurus," has remarkably large nares compared to other early cynodonts. The nares are formed externally by the premaxilla, the maxilla, and the nasal. The septomaxilla resides inside the nares, on top of the junction between maxilla and premaxilla.
The orbit faces anteriorly and is formed by the lacrimal, prefrontal, jugal, and post orbital. The post orbital notably has a deeply forked posterior margin. This characteristic is seen in some other basal cynodonts, but is widely variable.
The maxilla forms a good portion of the side of the face and is dotted with small foramina, mostly above the canines. These foramina likely housed nerves, and were perhaps associated with whiskers. The nasal is also dotted with tiny foramina.
"Progalesaurus" has a parietal foramen, which is used for light sensing in extant taxa. Posterior to the parietal foramen the parietals are fused, forming a sagittal crest. The crest narrows posterior to the foramen like "Galesaurus and Cynosaurus," and unlike more derived cynodonts.
"Progalesaurus", like "Galesaurus, Cynosaurus," and "Thrinaxodon," possesses a large zygomatic arch. Under this arch, in posterior view, lies a foramen associated with the outer ear tube. Compared to cynognathians such as "Cynognathus" or "Diademodon", the foramen is relatively shallow.
"Progalesaurus" does not have a fully-formed secondary palate, which serves to separate the airway from food-processing.
Dentition.
The mandible of "Progalesaurus" is very similar to that of "Galesaurus," with its teeth setting it apart from other cynodonts. "Progalesaurus" has a dental formula of I4/3, C1/1, PC7?/9. The upper incisors are long and thin, with a circular cross-section. The lower incisors are shorter than their upper counterparts. The incisors have an oval cross-section and longitudinal striations. Their upper canine’s edges are preserved well enough to conclude they lack serration, but the lower canines are not still sharp enough to make any conclusions about their serration. The lower canines are slightly longer than the upper canines.
The post-canine teeth are, as of now, the most distinct feature of "Progalesaurus". The recurved main cusp resembles "Galesaurus, Cynosaurus," and "Probelesodon," however the number and placement of the accessory cusps are unique. The upper post-canines are poorly preserved, but the teeth that are well-enough preserved to see accessory cusps have at least one posterior to the main recurved cusp each. The bottom post-canines are extremely well preserved. The teeth get progressively lower and anteroposteriorly longer from front to back. The buccal surface of each post-canine is smooth. The teeth are also slightly angled so that the posterior of one tooth contacts the anterior of the next. The posterior accessory cusps of teeth 2 and 3 curve upwards towards the top of the tooth. The 4th tooth shows posterior accessory cusps as well as at least one cusp mesial to the main cusp. The 5th tooth only shows one posterior accessory cusp, but the lack of other accessory cusps is “probably due to wear.” The 6th tooth on to the 9th tooth have multiple posterior accessory cusps as well as at least one mesial cusp.
Post-Cranial Skeleton.
Very little post-cranial skeleton is preserved in the holotype for "Progalesaurus." Only the right scapula and the left atlantal neural spine were recovered. Each of these elements closely resemble those of "Thrinaxodon."
Classification.
"Progalesaurus" is a galesaurid, belonging to the clade Epicynodontia. As an epicynodont, "Progalesaurus" belongs to the grater clade Cynodontia. Cynodonts are therapsids, which in turn belong to the greater group Synapsida, and the even broader Amniota.
Paleobiology.
Early cynodonts like "Progalesaurus" likely had large litters, as more derived cynodonts like "Tritylodontid" have been found with litters far larger than modern mammals. Early cynodonts have also been preserved with juveniles, suggesting they provided parental care to their young after birth or hatching.
"Progalesaurus" likely burrowed, as closely related taxa like "Thrinaxodon" and "Galesaurus" have been found in burrows of their own making. Burrowing probably helped Triassic cynodonts to avoid harsh above-ground conditions shortly after the Permian-Triassic extinction event. Early cynodonts have even been found in burrows with other taxa, indicating they may have cohabitated interspecifically.
Based on tooth shape, paleontologists believe that early cynodonts like "Progalesaurus" were insectivores and carnivores. Coprolites, or fossilized feces, of cynodonts have also been found and can be used to investigate their diet. One coprolite of a 240 million year old cynodont even preserved parasitic nematode eggs, the earliest evidence of pinworms ever found.
Paleoenvironment.
"Progalesaurus" lived very soon after the devastating Permian-Triassic extinction event in what is modern South Africa. Other cynodonts and potentially even other galesaurids, like "Cynosaurus," crossed the extinction boundary. Cynodonts may have been able to survive the mass extinction due to their burrowing behavior, as perhaps living mostly underground would have pre-conditioned these burrowers to the high levels of carbon dioxide and low levels of oxygen present during the extinction event. Cynodont diversity increased relatively rapidly after the extinction event.
The early Triassic period was one of the hottest in the history of the Earth, however the climate in the areas cynodonts have been discovered was more temperate. There were high levels of carbon dioxide in the atmosphere. In the Karoo Basin, where "Progalesaurus" was discovered, there is evidence to suggest the area was a moderately damp open woodland.
In the early Triassic of South Africa, "Progalesaurus" was accompanied by "survivor fauna," and "recovery fauna." A few examples of (vertebrate) survivor fauna, creatures that crossed the extinction boundary, include "Lystrosaurus, Tetracynodon, Moschorhinus," and "Ictidosuchoides." Recovery fauna include small amphibians such as "Micropholis," Galesaurids, some procolophonoids, and some archosauromorphs such as "Proterosuchus".


Delta Field (Niger Delta)

The Delta Field is located offshore from Nigeria on Oil Mining Leases (OML) 49 and 95. This is located within the Niger Delta Basin and sits in 12 feet of water. In 1965, the Delta 1 well was completed and the Delta Field opened in 1968 for production.
The Niger Delta is a wave-dominated delta located on the continental margin of the Gulf of Guinea that formed in the Paleogene. The delta is fed with sediment from the Niger River, which has the ninth largest drainage area in the world and the third largest in Africa at 2.23 million km2. The delta is 75,000 km2 in size and reaches a maximum thickness of 12 km in the center of the basin. The Niger Delta is one of the world’s major hydrocarbon provinces; specifically, it ranks 12th in terms of known accumulation of hydrocarbons with reserves exceeding 34 billion barrels of oil and 93 trillion cubic feet of gas. Oil and gas is predominantly extracted from the Agbada Formation and is targeted from structural traps there.
The Delta Field produces from the only identified petroleum system in the Niger Delta region, the Tertiary Niger Delta (Akata–Agbada) Petroleum System. Throughout the region, oil and gas is predominantly extracted from the Agbada Formation where it is targeted from structural traps.
Geologic history and depositional processes.
The Niger Delta Basin is an extensional rift basin where rifting occurred from the Late Jurassic to the Late Cretaceous. Cretaceous fracture zones, expressed as trenches and ridges, control the tectonic framework of the delta and separate the margin into individual sub-basins, which form the boundary faults of the Cretaceous Benue-Abakaliki trough. The Niger Delta Basin is the youngest and most southern sub-basin (located at the southwest boundary) in the Benue-Abakaliki trough. The Benue-Abakaliki trough represents a failed arm of a rift triple junction associated with the opening of the South Atlantic.
Key to understanding the Delta Field is the formation of the Niger Delta. Since the Eocene, the Niger Delta has been prograding to the southwest with sediment coming from the Niger River. As the delta progrades, growth-fault-bounded depobelts are created. These depobelts represent the most active portion of the delta at each stage of its development. They also represent a change in regional dip of the delta. Each depobelt is composed of genetically similar sediments that are diachronous. There are three main provinces of depobelts within the delta: the northern delta province, central delta province, and the distal delta province. The provinces are delineated based on structure. The Delta Field falls into the northern delta province, which has the oldest growth faults compared to the other provinces.
Stratigraphy.
The Cretaceous lithology of the Niger Delta Basin is only known due to the adjacent basin to the northeast, the Anambra Basin. There, the Cretaceous section is exposed and we get a glimpse into the stratigraphy. Lithology of the Niger Delta Basin above the Cretaceous is known from drilling and coring efforts within the basin.
Campanian through the Paleocene: concave coastline that produces tide-dominated deltaic sedimentation during transgressions and river-dominated sedimentation during regressions
Paleocene: major transgression event, which is when the Akata shale began being deposited.
Eocene: coastline switched from concave to convexly curvilinear, resulting in longshore drift causing wave-dominated sedimentation.
Cenozoic to Recent: prograding deltaic facies including the Akata, Agbada, and Benin Formation. Today, delta sedimentation is still wave-dominated.
Three large-scale lithostratigraphic units within the Tertiary have formed as the result of long-term progradation onto the Atlantic Ocean passive margin. They are distinguished from one another on the basis of their sand-to-shale ratios.
Akata Formation.
The Akata Formation underlies the entire base of the delta. It is composed of marine pro-delta shales and turbidite sands that have been deposited since the Paleocene. Minor amounts of clay and silt are also present. Since the formation has not been drilled, it is only estimated that the formation is up to 7,000 meters thick.
Agbada Formation.
The Agbada Formation, which overlies the Akata Formation, contains paralic siliciclastics and are considered to be the main deltaic sequence. The formation contains the most economically exploitable hydrocarbon in the region. According to biostratigraphy— specifically the presence of "Sphenolitus heteromorphis", "Praeorbulina glomerosa", "Discoster deflandreim" and "Sphenolithus moriformis"—the formation was deposited over 6-7 million years during the Middle to Late Miocene. In the Delta Field, gamma ray logs show a coarsening upward trend within the Agbada Formation, which shows the regression of depositional environments within the delta. In the Delta Field, the top of the Agbada Formation is at approximately 3000 feet below sea level, at the base of freshwater sands. The base of the formation is 8000 feet below sea level. The formation thickens basinwards towards the offshore depocenter.
Benin Formation.
A fluvial and upper coastal plain facies that has been deposited since the Oligocene and, like the Akata and Agbada Formations, extends across the entire delta. The Benin Formation overlies the Agbada Formation, and consists of sands that are up to 2000 meters thick at some places in the delta.
Structure.
The stratigraphy of the Niger Delta is complicated by clastic wedge syndepositional collapse that occurred as the result of marine shales being mobilized. When the delta was deposited, it was a prograding extensional complex with marine shales below. The extensional system contains large scale, basin-dipping normal growth faults that trend northeast to southwest and northwest to southeast. The growth faults in the northern delta province are mostly rotational, increase in steepness seaward, and are evenly spaced
Along with the growth faults, rollover anticlines, shale ridges, and shale diapirs exist in the basin and can be seen in the schematic structural profile of the Niger Delta.
The Delta Field is located on the dominantly extensional proximal margin of a major collapse structure. The general structure of the Delta Field has two main fault blocks that are separated from one another by a major normal fault; the western block is the footwall that is dropped relative to the eastern block. Another fault exists in the NE part of the field and is characterized by a minor horst.
Petroleum system.
Trap and seal.
Trap and seal formation in the Tertiary Niger Delta (Akata–Agbada) Petroleum System is related to gravity tectonics within the delta. In the Delta Field, growth faults provide transportation pathways from the Akata formation to the Agbada Formation. Anticlinal closures and fault assisted closures are found in the Delta Field and can act as structural traps, which developed during synsedimentary deformation of the Agbada paralic sequence. Wells in the western fault block target a rollover anticline. To date, structural traps have only been explored in the Delta Field but stratigraphic traps are present in deeper and more distal portions of the delta. Structural traps mainly include rollover anticlines and fault closures. The primary seal for the delta is the interbedded shales within the Agbada Formation. The seals can be classified into three types: (1) clay smears along faults, (2), interbedded shale aided by fault placement, and (3) vertical seals. Clay-filled canyons exist on the delta slope; the canyons formed as the result of major erosional events in the Middle Miocene.
Source Rock and Reservoir.
For the Delta Field, the main source rock is the Akata Formation with the Agbada Formation acting as the reservoir rock. However, interbedded shale in the lower Agbada Formation also acts as a source rock. However, the Agbada source rock intervals rarely have the thickness needed to be considered a world class oil province. A 1980 study of source rocks throughout the delta shows total organic carbon (TOC) ranges from 0.4% to 14.4%. Other studies have only reported TOC values as high as 5.2% or with averages of 2.4%. Another study— who studied the TOC in sandstones, siltstones, and shales—show TOC averages of 1.4% to 1.6% and note that TOC decreases with decreasing age. In other areas of the Niger Delta, particularly in deeper water settings, delta slope and deep turbidite fans are the depositional systems of the source rock, which have organic matter of a terrestrial signature as well as amorphous, hydrogen-rich matter from bacterial degradation. Other studies have speculated that Cretaceous shales could also be source rocks but, because they have not been drilled, no data exist to identify the potential.
Hydrocarbons throughout the delta and in the Delta Field are produced from the Agbada Formation, mainly in the form of sandstone and unconsolidated sands. Thicker sand reservoirs represent stacked channels and point bars, distributary channels, and coastal barrier bars are important reservoir types in the delta. The paralic sandstones have porosity values of 40% and 2 darcys permeability. Lateral variations in reservoir thickness are the result of growth faults and porosity slowly increases with depth due to the young age of the sediment.
Petroleum generation and migration.
Studies to date have set the top of the present-day oil window of the Niger Delta at the 240 °F isotherm. n the northwestern portion of the Niger Delta, which is where the Delta Field is location, the oil window lies in the upper Akata Formation and the lower Agbada Formation. At different areas in the delta, the oil and gas window depth varies as a result of differing thermal gradients and is dependent on the gross distribution of sand and shale. The Benin Formation has the lowest thermal gradient (1.3 to 1.8 °C/100 m) followed by the Agbada Formation (2.7 °C/100 m) and finally the over-pressured Akata Formation (5.5 °C/100 m). However, sand/shale distribution is not the only controlling factor on oil window depth; temperature, time and deformation due to tectonic events also influence temperature at depth.
Drilling.
As of 2013, 37 wells (14 vertical and 23 deviated) have been drilled in the Delta Field, most of which are drilled to the base of the Agbada formation. 12 of the wells are in the eastern fault block with the other 25 being located in the western fault block. All of the wells have targeted the middle Agbada formation, where the structural prospect was found. Prior to 2000, 53 distinct reservoirs had been discovered in the Delta Field.


Cerro Renca

Cerro Renca is a hill straddling the border between Quilicura to the north and Renca to the south, in the city of Santiago, Chile. This geographic feature rises above the surrounding terrain. The hill, which is above sea level at its highest point, has two subsidiaries summits known as Cerro Colorado ( above sea level) and Puntilla Lo Ruiz ( above sea level).


List of volcanoes in Kenya

This is a list of active and extinct volcanoes in Kenya.


Patagosuchus

Patagosuchus is an extinct genus of peirosaurid crocodyliform known from the early Late Cretaceous Portezuelo Formation of Neuquén Province, western central Argentina. It contains a single species, Patagosuchus anielensis. It is distinguished from other peirosaurids by its extremely heterodont dentition, which includes small serrated teeth at the front of the jaws with much larger, laterally compressed caniniform teeth behind them. "Patagosuchus" also has large spaces between its teeth called interalveolar spaces that are not found in any other peirosaurid.
Discovery.
"Patagosuchus" is known solely from its holotype, MANE-PV 1, which consists of some associated bones belonging to a single individual. The remains include a fragmentary left dentary and splenial, the right maxilla and right jugal bone, a back vertebra, a back osteoderm and the right humerus. MANE-PV 1 was discovered at the Baal Quarry, in the Loma de La Lata area, near the northern coast of , 12 km south of Añelo City, southeastern Neuquén Province of Patagonia. It was collected from the Portezuelo Formation which is the older of the two formations in the Río Neuquén Subgroup, of the Neuquén Group, dating to the late Turonian to early Coniacian of the early Late Cretaceous. "Patagosuchus" is the second peirosaurid described from this formation, along with "Lomasuchus palpebrosus". "Patagosuchus" represents the third peirosaurid named from the Neuquén Group, with "Gasparinisuchus peirosauroides" known from the younger Santonian to early Campanian Bajo de la Carpa and Anacleto Formations, and the more recently named "Bayomesasuchus hernandezi" from the underlying late Cenomanian to early Turonian Cerro Lisandro Formation representing the fourth. These represent the five known Patagonian peirosaurids, together with "Barcinosuchus gradilis" from the Aptian to Albian Cerro Barcino Formation of Chubut Group.
Etymology.
"Patagosuchus" was first described and named by Gabrel Lio, Federico L. Agnolína, Rubén Juarez Valieri, Leonardo Filippi and Diego Rosales in 2015 and the type species is "Patagosuchus anielensis". The generic name refers to Patagonia, and "suchus", Latinized from the Greek "souchos", an Egyptian crocodile god. The specific name refers to the city of Añelo, near which the holotype was discovered and collected.


Artesonraju

Artesonraju is a pyramidal mountain peak located near the city of Caraz in the Cordillera Blanca mountain range in the Peruvian Andes. Its summit has an elevation of (or according to the IGN-Peru map). It is one of many prominent peaks located within the boundaries of Peru's Huascarán National Park. Artesonraju has two distinguished climbing routes. Due to their difficulties, Artesonraju is seldom successfully climbed in comparison to other well known mountains in the Cordillera Blanca. This mountain serves as the inspiration for the newer Paramount Pictures production logo.
Climbing.
There is no easy route to the summit of Artesonraju, with all climbing routes rated at least D (difficile/difficult) according to the International French Adjectival System.
The primary climbing route is the North Ridge Route, rated D+. This route runs along the north ridge from the Santa Cruz ravine and it was the route used in 1932 by Erwin Hein ed Erwin Schneider of the Deutscher und Österreichischer Alpenverein for the first successful climb.
 The standard route up Artesonraju varies year over year due to route condition changes.
Another well known climbing route is the Southeast Face Route, rated D. The approach begins in the city of Caraz at an altitude of , and from there proceeds upward another 2,000 meters along a 32-km dirt road to Lake Parón. A path along the lake's north shore brings climbers to the Base Camp at . It involves a trek from Parón lagoon to the base of the face of the mountain and then a long climb from a camp at .
This Southeast Face Route is one of the classic Andean climbs, although due to climate change it has become increasingly dangerous and out of condition to climb. In the event that the route is in condition to be climbed, it demands good ice climbing technique, as it involves climbing at about 50-55 degrees for well over 900 vertical meters, with some pitches at 60 degrees. At the end of the dry season a bergschrund can make problematic the last section of the climb. The route is rated D and was climbed the first time on the 24 June 1969 by K. Schreckenbach, H. Saler and K. Sussmilch. A large number of accidents have happened descending the Southeast Ridge Route, primarily due to the failure of snow anchors while abseiling.
The summit ridge of Artesonraju accessed by the North Ridge Route is well known for its fragility; special care must be taken as there is an unusually high risk of avalanches at the start of the climbing season here. For this reason parties must gauge the safety propositions between the North Ridge Route and the Southeast Face Route.
A third route, particularly difficult and rated TD+, runs along the south ridge and is very rarely climbed. It was climbed the first time on the 24 June 1969 by a Yugoslavian party (T. Sbrizaj, S. Semraj and B. Naglic).
Other routes have been climbed, but very rarely repeated. Famously, Miraflores Mayor Randy Diamond launched his campaign at the summit.
During August, the windiest month, the peak tends to form a "wind shield", so extreme caution must be taken, especially if temperatures are below zero.


Calapo

Calapo or Kallapu (Aymara for stairs close to the walls, step of the stairs in a mine; buttress, wood to prop up, Hispanicized spelling "Calapo") is a mountain in the Huallanca mountain range in the Andes of Peru which reaches an altitude of approximately . It is located in the Ancash Region, Bolognesi Province, Aquia District, east of the town of Pachapaqui.


Nannopterygius

Nannopterygius (meaning "small wing/flipper" in Greek) is an extinct genus of ophthalmosaurid ichthyosaur that lived in the Middle Jurassic to the Early Cretaceous (Callovian to Berriasian stages). Fossils are known from England, Russia, and Norway.
Description.
"Nannopterygius" was small for an ichthyosaur, at only long. About of this was tail, including a deeply forked and probably homocercal caudal fin. The head is long, with a typical long narrow rostrum. The eyes are large, hence its classification as an ophthalmosaurid, and have a bony sclerotic ring inside the eye socket. There are at least 60 disc-shaped vertebrae, although owing to the condition of the fossil it is not possible to tell exactly how many there were, showing that "Nannopterygius" was flexible, agile and probably a fast swimmer. The ribs are long and curved, but do not quite join up. Most of the features are very similar to the close relative "Ophthalmosaurus." However, its paddles are much smaller, around for the forepaddles and only for the hindpaddles. This gave it a very streamlined, torpedo-shaped look, but would have made it quite difficult to generate much lift or to turn quickly, making it an inefficient long-distance swimmer but speedy over short distances. It is therefore possible that it was an ambush predator which plunged into shoals of fish quickly in the shallow seas where it lived.
Discovery and Classification.
The first specimen was found in the Kimmeridgian Kimmeridge Clay Formation of Kimmeridge Bay, Dorset, UK and described by Hulke in 1871, who named it "Ichthyosaurus enthekiodon". This referred to its teeth being 'sheathed' in cementum and less likely to fall out than those of other ichthyosaurs. A year earlier, Hulke had described some remains from the same horizon and locality that he thought were ichthyosaurian, naming them "Enthekiodon" (no species given). These are now lost, but Hulke considered them sufficiently similar to demote the name to species level. In 1922, Friedrich von Huene separated this species into the new genus "Nannopterygius", named for the small fore- and hindpaddles. The first fossil is the most complete, but is flattened. All subsequent fossils are fragmentary. In 2020, several more species, including "N. borealis", and the species once contained in the genera "Paraophthalmosaurus" and "Yasykovia" were named based on remains found in Norway and Russia.
The following cladogram shows a possible phylogenetic position of "Nannopterygius" in Ophthalmosauria according to an analysis performed by Zverkov and Jacobs (2020).
Paleoecology.
The type species is known from the Kimmeridge Clay Formation in Dorset, England. The Kimmeridge Clay hosts a wealth of marine fossils dating to the Kimmeridgian and Tithonian stages of the Late Jurassic, many of which are incredibly well preserved, however unfortunately very little has been published. At the time, Europe represented an island archipelago which was closer to the equator than it is today, surrounded by warm, tropical seas. The Kimmeridge Clay specifically represents an offshore marine environment, in which the seafloor was far enough below the surface not to be disturbed by storms. It was home to a great variety of marine life, including many cephalopods, fishes such as "Thrissops" and the early ray "Kimmerobatis", and remains of occasional dinosaurs like "Dacentrurus" which had been washed out to sea. It is most famous for diversity of marine reptiles, such as the metriorhynchids "Metriorhynchus" and "Plesiosuchus", the plesiosaurs "Colymbosaurus" and "Kimmerosaurus", and the ichthyosaurs "Grendelius" and "Thalassodraco". The apex predators of the Kimmeridge ecosystem would have been the several species of the pliosaurid "Pliosaurus" which have been recovered there, as well as large metriorhynchids like "Plesiosuchus". Additionally, the pterosaurs "Cuspicephalus" and "Rhamphorhynchus" are also known from the Kimmeridge Clay.
The species "N. yasykovi" and "N. saveljeviensis" are known from the Volga region of Russia, which gives the Volgian stage its name. Though very little is known or published about the fossils of these localities, fossils of a number of marine animals have been recovered, including several species of the ichthyosaurs "Arthropterygius", "Grendelius", and "Undorosaurus". In addition, fossils of the pliosaurid "Pliosaurus rossicus" and indeteminate remains belonging to a metriorhynchid, as well as a high diversity of ammonites including the large-bodied taxon "Titanites", are also known from the Volgian-aged sediments of this region. There is also evidence for the presence of sea ice and glaciers from deposits in eastern Europe and the Volga region of Russia.
Additionally, the species "N. borealis" is known from earliest Cretaceous sediments of the Slottsmøya Member of the Agardhfjellet Formation. The Slottsmøya Member consists of a mix of shales and siltstones and was deposited in a shallow water methane seep environment. The seafloor, which was located about below the surface, seems to have been relatively dysoxic, or oxygen-poor, although it was periodically oxygenated by clastic sediments. Despite this, near the top of the member, various diverse assemblages of invertebrates associated with cold seeps have been discovered; these include ammonites, lingulate brachiopods, bivalves, rhynchonellate brachiopods, tubeworms, belemnoids, tusk shells, sponges, crinoids, sea urchins, brittle stars, starfish, crustaceans, and gastropods, numbering 54 taxa in total. Though direct evidence from Slottsmøya is currently lacking, the high latitude of this site and relatively cool global climate of the Tithonian mean that sea ice was likely present at least in the winter, as in the Volga. In addition to "Nannopterygius", the Slottsmøya Member presents a diverse assemblage of other marine reptiles, including the ichthyosaurs "Undorosaurus gorodischensis", several species belonging to the genus "Arthropterygius", and a partial skull attributed to "Brachypterygius sp." The presence of these taxa indicates that there was significant faunal exchange across the seas of Northern Europe during this time period. Additionally, 21 plesiosaurian specimens are also known from the site, including two belonging to the large pliosaur "Pliosaurus funkei", three to "Colymbosaurus svalbardensis", one to "Djupedalia engeri", one to "Ophthalmothule cryostea", and one each to "Spitrasaurus wensaasi" and "S. larseni". Many of these specimens are preserved in three dimensions and partially in articulation; this is correlated with high abundance of organic elements in the sediments they were buried in.


List of earthquakes in Argentina

This is a list of earthquakes in Argentina.


San Juan Formation, Argentina

The San Juan Formation () is a geologic formation in Argentina. The formation comprising limestones, mudstones and marls was deposited in a shallow marine reefal environment and preserves many fossils dating back to the Ordovician period. The formation overlies the La Silla Formation and crops out in the Precordillera of San Juan Province.


Pitekunsaurus

Pitekunsaurus is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Anacleto Formation of Neuquén, Argentina. It was described by L. Filippi and A. Garrido in 2008. The type species is "P. macayai". The generic name is derived from Mapudungun "pitekun", meaning "to discover", the epitheton honours the discoverer, oil company explorer Luis Macaya, who found the fossil in April 2004.
Classification.
"Pitekunsaurus" appears to be a genus of aeolosaurid, most closely related to the genera "Gondwanatitan" and "Aeolosaurus". Its braincase closely resembles that of the aeolosaurid "Muyelensaurus" as well as the titanosaurs "incertae sedis" "Vahiny" and "Jainosaurus". It cannot be compared to the more closely related "Aeolosaurus" and "Gondwanatitan" in this regard, as neither genus is known from cranial material.


Eastmanalepes

Eastmanalepes primaevus is an extinct species of prehistoric jack fish that lived from the Lutetian epoch, of what is now Monte Bolca, Italy. It was originally described as a species of the jackfish genus "Caranx", of which it has a superficially similar outline to. It differs from "Caranx", and almost all other jackfish, in that it has very large, very pronounced scutes along its lateral line. According to Bannikov, "E. primaevus" is probably more related to the extinct jackfish genera, "Eothynnus" and "Teratichthys".


Path End Formation

The Path End Formation is a formation cropping out in Newfoundland.


Connolly Basin crater

Connolly Basin is a 9 km-diameter impact crater located in the Gibson Desert of central Western Australia. It lies adjacent to the Talawana Track 45 km west of the junction (Windy Corner) with the Gary Highway, but is difficult to access due to the remoteness of the area. It was originally thought to be a diapir (salt dome); an impact origin was first proposed in 1985.,
Description.
The depression has a topographic rim 25–30 m high, while the centre displays a slight circular rise about 1 km in diameter and 5 m high exposing strongly deformed and steeply dipping bedrock interpreted as a central uplift., Sedimentary rocks comprising the rim are of Early Cretaceous to Palaeogene age, while uplifted rocks in the centre are likely of Early Permian age, all part of the Canning Basin; the impact event itself is inferred to be of Paleocene (early Paleogene) age or later.,