Crown and stem amniote problems: resolved by the LRT

Modesto 2024 discusses
Problems of the interrelationships of crown and stem amniotes. Modesto reports, “The oldest amniotes are Late Carboniferous in age (ca. 318 million years ago), and they are preserved in coal beds and lycopod tree stumps that have yielded rich faunas of temnospondyls, anthracosaurs, and other early tetrapods.”

And there’s the problem. Here’s the solution:

Add taxa. Neither Modesto nor any other academic steeped in basal amniotes recognize Early Carboniferous (Viséan) Silvanerpeton (Fig 2) as the last common ancestor of all extant amniotes in the large reptile tree (LRT, 2312 taxa) – becaue they omit it from cladograms.

A basal amniote doesn’t have to look like a reptile. It just has to reproduce like a reptile, by enclosing embryos in an amnion.

Basal Diadectomorpha

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Figure 1. Basal Diadectomorpha

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2011/09/diadectomorpha.jpg?w=296″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2011/09/diadectomorpha.jpg?w=584″ class=”size-full wp-image-1973″ src=”https://pterosaurheresies.files.wordpress.com/2011/09/diadectomorpha.jpg?w=584&h=591″ alt=”Basal Diadectomorpha” width=”584″ height=”591″ srcset=”https://pterosaurheresies.files.wordpress.com/2011/09/diadectomorpha.jpg?w=584&h=591 584w, https://pterosaurheresies.files.wordpress.com/2011/09/diadectomorpha.jpg?w=148&h=150 148w, https://pterosaurheresies.files.wordpress.com/2011/09/diadectomorpha.jpg?w=296&h=300 296w, https://pterosaurheresies.files.wordpress.com/2011/09/diadectomorpha.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Basal Diadectomorpha [from 2011].

Modesto follows out-dated textbooks when he reports,
“the overall picturegenerated by the early-tetrapod research community agrees that Amniota is a clade (monophyletic group) that is divided into Synapsida on one hand and Reptilia on the other hand;”

The LRT nests Synapsida within Archosauromorpha (by definition) and Amniota is a junior synonym for Reptilia. Modesto and others will find this out when they add pertinent taxa to their cladograms.

Figure 2. Eusauropleura to scale with ancestral and descendant taxa including Eucritta, Utegenia, Silvanerpeton and Gephyrostegus, the last common ancestor of all reptiles. ” data-image-caption=”

Figure 2. Eusauropleura to scale with ancestral and descendant taxa including Eucritta, Utegenia, Silvanerpeton and Gephyrostegus, the last common ancestor of all reptiles.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2018/12/gephyrostegus_eusauropleura588.jpg?w=202″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2018/12/gephyrostegus_eusauropleura588.jpg?w=584″ class=”size-full wp-image-34503″ src=”https://pterosaurheresies.files.wordpress.com/2018/12/gephyrostegus_eusauropleura588.jpg?w=584&h=869″ alt=”Figure 2. Eusauropleura to scale with ancestral and descendant taxa including Eucritta, Utegenia, Silvanerpeton and Gephyrostegus, the last common ancestor of all reptiles.” width=”584″ height=”869″ srcset=”https://pterosaurheresies.files.wordpress.com/2018/12/gephyrostegus_eusauropleura588.jpg?w=584&h=869 584w, https://pterosaurheresies.files.wordpress.com/2018/12/gephyrostegus_eusauropleura588.jpg?w=101&h=150 101w, https://pterosaurheresies.files.wordpress.com/2018/12/gephyrostegus_eusauropleura588.jpg?w=202&h=300 202w, https://pterosaurheresies.files.wordpress.com/2018/12/gephyrostegus_eusauropleura588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2. Eusauropleura to scale with ancestral and descendant taxa including Eucritta, Utegenia, Silvanerpeton and Gephyrostegus, the last common ancestor of all reptiles. (from 2018]

Modesto cites Klembara et al 2021,
who found diadectomorphs are crown amniotes (= reptiles).

The LRT found diadectomorphs (Fig 1) are the sisters of procolophonids on one branch and pareiasaurs + turtles on the other in 2011 and 2013.

Modesto criticized Klembara et al when he wrote,
“Perhaps the greatest weakness in Klembara et al.’s (2021) phylogenetic conclusions is that these authors neglected to include any “microsaurs,” which is surprising in light of numerous previous studies that recover “microsaurs” (with other lepospondyls) closer
to Amniota than to either seymouriamorphs, gephyrostegids, or chroniosuchids.”

The LRT tests all these clades.

Modesto concluded,
“I infer that the researchers were unfamiliar with the literature on early amniotes, resulting in the use of obsolete anatomical information for certain amniote terminal taxa.”

While it is good to hear that at least a few professionals test published studies and matrices, the number one problem affecting paleontology continues to be taxon exclusion.

Don’t let amateurs lead the way. Don’t let amateurs resolve all the issues and enigmas decades before the professionals get around to adding taxa. Build your own LRT before you’re the last one on your block to do so.

References
Klembara J, Ruta M, Hain M and Berman DS 2021. Braincase and inner
ear anatomy of the Late Carboniferous tetrapod Limnoscelis dynatis (Diadectomorpha)
revealed by high-resolution X-ray microcomputed tomography. Front. Ecol. Evol. 9,
709766. doi:10.3389/fevo.2021.709766
Modest SP 2024. Problems of the interrelationships of crown and stem amniotes. Frontiers Earth Science 12:1155806. doi: 10.3389/feart.2024.1155806

You heard it here in 2011: diadectids are amniotes

Diadectes is not an Amphibian. And Procolophon is a diadectid.