The terms
"Sauropsida" ("lizard faces") and "Theropsida" ("beast faces")
were used again in 1916 by E.S.
Goodrich to
distinguish between lizards, birds, and their relatives on the one hand
(Sauropsida) and mammals and their extinct relatives
(Theropsida) on the other. Goodrich supported this division by the nature of
the hearts and blood vessels in each group, and other features such as the
structure of the forebrain. According to Goodrich, both lineages evolved from
an earlier stem group, Protosauria ("first lizards") which included
some Paleozoic amphibians as well as early reptiles.[7]
In 1956 D.M.S. Watson observed that the first two
groups diverged very early in reptilian history, and so he divided Goodrich's
Protosauria between them. He also reinterpreted Sauropsida and Theropsida to
exclude birds and mammals, respectively. Thus his Sauropsida included Procolophonia, Eosuchia, Millerosauria, Chelonia (turtles), Squamata (lizards and snakes), Rhynchocephalia, Crocodilia, "thecodonts" (paraphyletic basal Archosauria), non-avian dinosaurs, pterosaurs, ichthyosaurs, and sauropterygians.[8]
The
traditional class Reptilia (green field) are a paraphyletic group comprising all non-avian
and non-mammalian amniotes.
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