SVP 2018: Clinging to invalidated clades: Parareptilia

MacDougall, Brocklehurst and Fröbisch 2018
bring us a look at the evolutionary disparity of a paraphyletic traditional clade, Parareptilia, a clade not recovered in the large reptile tree (LRT, 1311 taxa). The clade has disparate members because the clade is not monophyletic and purported clade members are not closely related to one another. This is a poor wastebasket clade that needs to go. Now. We’ve known this since 2012.

The first line of their abstract reflects taxon exclusion thinking.
“The clade Parareptilia, the sister taxon of Eureptilia, is a group of sauropsids that thrived
during the Late Palaeozoic and Early Mesozoic.” The LRT invalidated these clades seven years ago by including more taxa that split the Reptilia (= Amniota) into Archosauromorpha and Lepidosauromorpha in the Viséan.

Red Flag ignored by the authors who report,
“Parareptilia is notable in that members of the clade exhibit a wide range of morphologies. Examples include: small, predatory superficially lizard-like taxa, secondarily aquatic taxa, and large, armored herbivorous taxa.” Wikipedia topic: Parareptilia reports these traditionally include procolophonids, millerettids, mesosaurs and pareiasaurs, taxa essentially unrelated in the LRT, which tests all known tetrapod clades.

So several problems arise
when the authors report, Most major parareptilian clades go extinct during or before the end-Permian mass extinction event, with only one clade, the Procolophonoidea, surviving into the Mesozoic, before eventually going extinct at the end of the Triassic.”

  1. Several traditional procolophonids (like Owenetta and Barasaurus, neither closely related to Procolophon, bolosaurids and diadectids) are basal to lepidosauriformes in the LRT, so they don’t go extinct.
  2. Some millerettids are basal to turtles and lepidosaurs in the LRT, so they don’t go extinct.
  3. Mesosaur sisters evolve to become thalattosaurs and ichthyosaurs in the LRT. They do go extinct.
  4. Pareiasaurs are basal to turtles in the LRT, so they don’t go extinct.

In time
the authors are going to find themselves embarrassed by this abstract. All they have to do is add more taxa to see the folly of their hypothesis.

MacDougall MJ, Brocklehurt N, Fröbisch J 2018. The morphological disparity and phylogenetic diversity of Parareptilia throughout their evolutionary history. SVP abstracts.


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