Lepidosaur
| Lepidosaurs Temporal range: Middle Triassic - Present,240–0 Ma |
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| A Coachella Valley fringe-toed lizard | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Lepidosauromorpha |
| Superorder: |
Lepidosauria Haeckel, 1866 |
| Orders | |
The Lepidosauria (from Greek meaning scaled lizards) are reptiles with overlapping scales. This subclass includes Squamata and Rhynchocephalia. It is a monophyletic group and therefore contains all descendents of a common ancestor. Squamata includes snakes, lizards, and amphisbaenia. Rhynchocephalia was a widespread and diverse group 220-100 million years ago; however, it is now represented only by the genus Sphenodon, which contains two species of tuatara, native to New Zealand. Lepidosauria is the sister taxon to Archosauria, which includes Aves and Crocodilia. Lizards and snakes are the most speciose group of Lepidosaurs and, combined, contain over 9,000 species. There are many noticeable distinguishing morphological differences between lizards, tuataras, and snakes.
The reptiles in the subclass Lepidosauria can be distinguished from other reptiles by a variety of characteristics. First, the males have evolved a hemipenis instead of a single penis with erectile tissue that is found in crocodilians, birds, mammals, and turtles. The hemipenis can be found in the base of the tail. The tuatara has not fully evolved the hemipenis, but instead has shallow paired outpocketings of the posterior wall of the cloaca that have been determined to be precursors to the hemipenis.
Second, most Lepidosaurs have the ability to autotomize their tails. However, this trait has been lost on some recent species. In lizards, fracture planes are present within the vertebrae of the tail that allow for its removal. Some lizards have multiple fracture planes, while others just have a single fracture plane. The regrowth of the tail is not always complete and is made of a solid rod of cartilage rather than individual vertebrae. In snakes, the tail separates between vertebrae and some do not experience regrowth.
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Wikipedia