Rethinking Lizards

The origin and evolution of the Lepidosauria
Lepidosauria (= sphenodontids + squamata) has undergone some revision with the recovered results of the large reptile tree. Conventional thinking links archosaurs and lepidosaurs to a common ancestor close to Youngina and Prolacerta. Not true.

Figure 1. Conventional thinking on the family tree of lizards (above). According to the large reptile tree (below).  Conventional thinking includes Prolacerta and Youngina, which are not related to lizards or their kin, but nest on the second branch of the Reptilia, the new archosauromorpha.

Figure 1. Conventional thinking on the family tree of lizards (above). According to the large reptile tree (below). Conventional thinking includes Prolacerta and Youngina, which are not related to lizards or their kin, but nest on the second branch of the Reptilia, the new archosauromorpha.

According to the large reptile tree
Lepdiosauriformes descended from owenettids with which they share a ventrally open lateral temporal fenestra and a more typical upper temporal fenestra. Lepidosauriformes include the so-called “rib” gliders and their flightless ancestors, like Palaegama.

More Sphenodontids (Rhynchocephalia)
At the base of the Sphenodontia is a splinter clade currently composed of Marmoretta and MegachirellaRather than following conventional thinking and excluding Trilphosaurus and rhynchosaurs, the large reptile tree includes these taxa in the Sphenodontia (Rhynchocephalia).

At Least One More Squamate Clade – Tritosauria
Rather than just two squamate clades, the Scleroglossa (including snakes) and Iguania, we now add a third clade, the Tritosauria and perhaps a fourth even more basal clade, including Renestosaurus, Homoeosaurus and Dalinghosaurus. The Tritosauria now includes former protorosaurs like Tanystropheus and drepanosaurs. Tritosaurs also include the Fenestrasauria, which includes pterosaurs.

Diphyletic Snakes
Snakes are now shown to be diphyletic. Small burrowing forms, like Leptotyphlops, are related to Heloderma and Lanthanotus. Large terrestrial forms, like Pachyrhachis, are closer to Bahndwivici and Adriosaurus.

So things are becoming more interesting
The Lepidosauria is expanding as it nests former enigmas.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

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