As promised, updates arrive, but not always promptly.
Here is an updated phylogram of the large reptile tree placed against a time scale. Due to the large number of taxa (340+) it is quite impossible to read this unless you download the PDF file. Then there’s no limit to its magnification.
A phylogram differs from a cladogram in showing the amount of change between taxa by the length of the horizontal bars. Longer bars indicate greater morphological change.
Some key features
1. Sometime during the Carboniferous (Mississippian + Pennsylvanian) reptiles had their origin and their original split, but not much happened or is known about them from that remote time. Reptiles remain in the minority (it was the age of Amphibians) and no great radiations occurred then.
2. The Permian was a time of great radiation for both the Archosauromorph and Lepidosauromorph lines. Among the former, synapsids paralleled proto-diapsids and early diapsids. Among the latter large diadectomorphs and pareiasaurs dominated.
3. During the PermoTriassic extinction event only a few lineages made it through.
Among the new Lepidosauromorphs the turtles (Proganochelys) and the lepidosaurs (Paliguana, Lacertulus) survived.
Among the new Archosauromorpha three main lines survived. Certain Permian synapsids evolved to become Triassic protomammals and Jurassic mammals. Dicnynodonts also made it through.
Permian enaliosaurs like Claudiosaurus and Stereosternum gave rise to a large marine radiation in the Triassic.
Permian younginoids, like Thadeosaurus and Protorosaurus, gave rise to a large terrestrial radiation in the Triassic.
4. Many of the Triassic lepidosauromorphs did not change much into the Jurassic, Cretaceous and later eras.
By contrast, most of the Triassic archosaurmorphs became extinct or evolved into other taxa during later eras.
5. There are a few chronological oddballs, like Lotosaurus, a taxon claimed to come from Early Triassic sediments, but this seems at odds with the evolution of its purported temporal contemporaries and phylogenetic sisters.