Basal Tetrapods, slightly revised

Figure 1. Click to enlarge. With the addition of Panderichthys and Anthracosaurus the position of Koilops and Deltaherpeton have shifted to the base of the Temnospondyli.

Figure 1. Click to enlarge. With the addition of Panderichthys and Anthracosaurus the position of Koilops and Deltaherpeton have shifted to the base of the Temnospondyli. Some of that shifting is due to rescoring.

After earlier identifying
phylogenetic miniaturization at the bases of several major clades in the large reptile tree (LRT, 969 taxa), I wondered if similar size-related patterns appear in basal tetrapods.

  1. Osteolepis is smaller than Eusthenopteron. Has anyone removed the scales from the fore fins of Osteolepis to see what the bones inside look like?
  2. Pholidogaster is much larger than Osteolepis, but Colosteus and Phlegethontia are successively smaller with smaller limbs.
  3. Ventastaga and Pederpes are successively smaller than Ichthyostega.
  4. Koilops is much smaller than Ventastaga and Pederpes
  5. Eucritta is much smaller than Proterogyrinus, both in overall size and in relative torso length. Eucritta nests at the base of the Seymouriamorpha + Crown Tetrapoda.
Figure 2. Basal tetrapod skulls in dorsal view.

Figure 2. Basal tetrapod skulls in dorsal view. Tetrapoda arise with flattened skulls. Paratetrapoda retain skulls with a circular cross section. 

 

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2 thoughts on “Basal Tetrapods, slightly revised

  1. Eucritta is much smaller than

    Well, all known specimens are juvenile. Take a look at their vertebrae if you can find them.

    Concerning flat vs. round, take a look at Pederpes and Crassigyrinus and Megalocephalus and Spathicephalus – it’s a character with a complex history.

  2. As you know, and as I learned while constructing the LRT, when clades originate they often do so with smaller taxa, typically with juvenile traits. For casual readers: this is called neotony.
    With regard to Pederpes and Crassgyrinus, indeed they had skulls that were taller and boxier, but not rounder.

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