Drepanosauridae
| Drepanosaurs Temporal range: Late Triassic, 220–216.5 Ma |
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| Fossil specimen of Drepanosaurus unguicaudatus | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | †Protorosauria |
| Clade: |
†Drepanosauromorpha Renesto et al., 2010 |
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Drepanosaurs (members of the clade Drepanosauromorpha) are a group of strange reptiles that lived during the Carnian stage of the late Triassic Period, between 220 and 216 million years ago. The various species of drepanosaurid were characterized by odd specialized grasping limbs and often prehensile tails, adaptions for arboreal (tree-dwelling) and/or possibly aquatic lifestyles. Fossils of drepanosaurs have been found in Arizona, New Mexico, New Jersey, Utah, England, and northern Italy. The name is taken from the family's namesake genus Drepanosaurus, which means "sickle lizard", a reference to their strongly curved claws.
Drepanosaurs are notable for their distinctive, triangular skulls, which resemble the skulls of birds. Some drepanosaurs, such as Hypuronector, had pointed, toothless, bird-like beaks. This similarity to birds may have led to the possible mis-attribution of a drepanosaur skull to the would-be "first bird", Protoavis.
Drepanosaurs featured a suite of bizarre, almost chameleon-like skeletal features. Above the shoulders of most species was a specialized "hump" formed from fusion of the vertebrae, possibly used for advanced muscle attachments to the neck, and allowing for quick forward-striking movement of the head (perhaps to catch insects). Many had derived hands with two fingers opposed to the remaining three, an adaptation for grasping branches. Some individuals of Megalancosaurus (possibly exclusive to either males or females) had a primate-like opposable toe on each foot, perhaps used by one sex for extra grip during mating. Most species had broad, prehensile tails, sometimes tipped with a large "claw", again to aid in climbing. These tails, tall and flat like those of newts and crocodiles, have led some researches to conclude that they were aquatic rather than arboreal. In 2004, Senter dismissed this idea, while Colbert and Olsen, in their description of Hypuronector, state that while other drepanosaurs were probably arboreal, Hypuronector was uniquely adapted to aquatic life. The tail of this genus was extremely deep and non-prehensile – much more fin-like than members of the more exclusive group Drepanosauridae.
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