Lizard - Evolution and relationships 1
2010-12-30 @ 17:57:11
The retention of the basic 'reptilian' amniote body form by lizards makes it tempting to assume any similar animal, alive or extinct, is also a lizard. However, this is not the case, and lizards as squamates are part of a well-defined group.
The earliest "lizard" was superficially lizard-like, but had a solid, box-like skull, with openings only for eyes, nostrils, etc. (termed Anapsid). Turtles retain this skull form. Early anapsids later gave rise to two new groups with additional holes in the skull to make room for and anchor larger jaw muscles. Those with a single hole, the Synapsids, gave rise to the superficially lizard-like Pelycosaurs, which include Dimetrodon and the Therapsids, including the Cynodonts, from which the modern mammals would evolve.
The earliest "lizard" was superficially lizard-like, but had a solid, box-like skull, with openings only for eyes, nostrils, etc. (termed Anapsid). Turtles retain this skull form. Early anapsids later gave rise to two new groups with additional holes in the skull to make room for and anchor larger jaw muscles. Those with a single hole, the Synapsids, gave rise to the superficially lizard-like Pelycosaurs, which include Dimetrodon and the Therapsids, including the Cynodonts, from which the modern mammals would evolve.