A ?comprehensive phylogeny and revised taxonomy of Diadectomorpha

From the Ponstein et al 2024 abstract:
“A 100 Ma gap separates the oldest terrestrial tetrapods and the first undisputed herbivorous tetrapods. While four clades of early tetrapod herbivores are undisputed amniotes, the phylogenetic position of Diadectomorpha with respect to Amniota has long been controversial.”

Not controversial in the LRT.
Diadectes was allied with Procolophon in the LRT in 2013 (Fig 1).

Ponstein et al begin tetrapods
with Middle Devonian quadrupedal tracks from 390 million years ago.

By the Early Permian,
280 mya, herbivorous captorhinds, bolosaurids, millerettids and diadectids were widespread, so their origin was much earlier. Carbonodraco (Fig 2), a pareiasaur ancestor close to diadectids, appeared much earlier, in the Middle Pennsylvanian, 310 mya. So that’s 80 million years after the Middle Devonian tracks. More primitive herbivorous reptiles (see figure 3) would have filled the later segment of that time gap.

Ponstein et al continued,
“Historically, phylogenetic analyses have found Diadectomorpha as the sister-group to
amniotes, but recent analyses recover Diadectomorpha as sister-group to Synapsida, within Amniota. We tested whether diadectomorphs are amniotes by updating the most recent character–taxon matrix.”

In the LRT (Fig 3) Diadectomorpha nest within the Lepidosauromorpha, of which a majority, if not all, are herbivores from their Early Carboniferous start. Lepidosauromoropha immediately follow the advent of the amniotic egg in Silvanerpeton at 346–330 million years ago. So there’s a last common ancestor of lepidosauromorph herbivores likely appearing only 50–60 million years  after those Middle Devonian tracks.

“Our majority rule consensus places Diadectomorpha as sister-group to Synapsida; other methods do not recover this relationship.”

Three Ponstein et al cladograms are shown in figure 4. This cladogram suffers from taxon exclusion. Synapsida are members of the Archosauromorpha in the LRT.

Add taxa to resolve phylogenetic issues within the Ponstein et al cladograms.

The authors list Desmatodon from the Upper Carboniferous
as the oldest known undisputed herbivorous tetrapod. This is a diadectid known from some jaw materials, perhaps postdating, perhaps coeval with Carbonodraco (Fig 2). More primitive herbivores appear in the LRT (Fig 3) despite their late-survivor status. They should be counted as ghost lineages.

The taxon lists in Ponstein et al
omit large swaths of pertinent taxa. So many taxa that they do not recover the basal reptile dichtomy following scaly Silvanerpeton (Fig 3) the first known reptile based on its last common ancestor status in the LRT.

The Pontein et al phylogeny is not a comprehensive phylogeny, as they claim.

References
Ponstein J, MacDougall MJ and Fröbisch J 2024. A comprehensive phylogeny and revised taxonomy of Diadectomorpha with a discussion on the origin of tetrapod herbivory. R. Soc. Open Sci. 11: 231566. https://doi.org/10.1098/rsos.231566

wikiDesmatodon
wiki/Diadectomorpha

Source: https://pterosaurheresies.wordpress.com/2024/07/02/a-comprehensive-phylogeny-and-revised-taxonomy-of-diadectomorpha/