But… for the wrong reasons.
Reig 1967 prophetically wrote:
“Archosaurs and lepidosaurs apparently have different origins; the former come from the pelycosaurs, and the latter come from the captorhinomorph cotylosaurs through the Millerettiformes.”
Considered heretical at the time,
Reig’s pronouncement echoes in the large reptile tree (LRT, 1151 taxa).
Here’s the full abstract:
“The characteristics of the first archosaurs, the proterosuchian thecodonts, show that neither of the supposed common ancestors of archosaurs and lepidosaurs could actually be an ancestor of archosaurs. Instead, the evidence seems to indicate that the archosaurian ancestors are probably in the ophiacodont-varanopsid group of the pelycosaurian synapsids. In particular, the Varanopsidae are strongly indicative of proterosuchian relationships, as they have evolved some characters which are elsewhere found only in archosaurs. Archosaurs and lepidosaurs apparently have different origins; the former come from the pelycosaurs, and the latter come from the captorhinomorph cotylosaurs through the Millerettiformes.”
The only thing he got wrong
(as everyone else got wrong until seven years ago) was not splitting the Varanopsidae into the Synapsida and the Prodiapsida, as demonstrated in the LRT. He also thought proterosuchids arose directly from varanopsids like Varanodon (Fig. 1), which converge with proterosuchids in size and skull shapes. There’s even an antorbital fenestra, or elongated naris and a drooping premaxilla in Varanodon. No wonder Reig got excited.
Archosauriforms do arise from
former varanopsids, like Heleosaurus and Mycterosaurus, but not directly. They have to pass through the diapsid grade, then the basal terrestrial younginiform grade before evolving into proterosuchids.
Lepidosaurs do arise from
captorhinomorphs and millerettids in the LRT, but again, not directly. First they have to pass through the nycteroleterid, owenettid, and basal lepidosauriform grades before evolving into lepidosaurs.
The LRT recovered
two clades of diapsids one closer to lepidosaurs and another closer to archosaurs.
Reig OA 1967. Archosaurian reptiles: a new hypothesis on their origins.