Pterodactyloidea Pterodactyloidea Pterodactyloidea (derived from the Greek words "πτερόν" ("pterón", for usual "ptéryx") "wing", and "δάκτυλος" ("dáctylos") "finger" meaning "winged finger", "wing-finger" or "finger-wing") is one of the two traditional suborders of pterosaurs ("wing lizards"), and contains the most derived members of this group of flying reptiles. They appeared during the middle Jurassic Period, and differ from the basal (though paraphyletic) rhamphorhynchoids by their short tails and long wing metacarpals (hand bones). The most advanced forms also lack teeth, and by the late Cretaceous, all known pterodactyloids were toothless. Many species had well developed crests on the skull, a form of
South Polar region of the Cretaceous notably the rhomaleosaurids and "Leptocleidus", which died out in the Early Cretaceous, indicating the polar freshwater systems may have been a refuge for the pliosaurs of the Cretaceous. In contrast to modern marine reptiles, these South Polar plesiosaurs probably had a better tolerance of colder waters. Early to Middle Cretaceous marine reptile remains of South Australia include five families of plesiosaurs–Cryptoclididae, Elasmosauridae, Polycotylidae, Rhomaleosauridae, and Pliosauridae–and the ichthyosaur family Ophthalmosauridae. The discovery of several juvenile plesiosaur remains suggest they used the nutrient-rich waters of the coast as sheltered calving grounds, the cold deterring predators such as sharks. Most of the