Pederpes gets the DGS treatment

Updated March 15, 2017 with higher resolution data. 

The first known basal tetrapod with a five-toed pes is
Pederpes finneyae (Clack 2002; Tournasian, early Carboniferous, 348mya; 1m in est. length) and it is known from a fairly complete articulated skeleton. In an attempt to reconstruct the skull I have colored elements (Fig. 1) and moved those tracings to a reconstruction in which some of the broken loose pieces have been replaced to their in vivo positions.

The lacrimal, maxilla and jugal
have broken parts that fit together like puzzle pieces. I did not realize the premaxilla was rotated, along with the lower jaw tip, such that in appeared in more dorsal view.

Figure 2. Pederpes skull elements returned to their in vivo positions. Skull roof is shown rotated to the picture plane, but in life would have been flat and seen edge-on. This is a revised reconstruction based on higher resolution data.

Figure 1. Pederpes skull elements returned to their in vivo positions. Skull roof is shown rotated to the picture plane, but in life would have been flat and seen edge-on. This is a revised reconstruction based on higher resolution data.

In the large reptile tree
Pederpes now nests with Whatcheeria.

References
Clack JA 2002. An early tetrapod from ‘Romer’s Gap’. Nature. 418 (6893): 72–76.

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8 thoughts on “Pederpes gets the DGS treatment

  1. That postfrontal you’re “finding” is really seriously strange. So are several other bones. I hope you can get a better photo…

    …which won’t be easy, seeing as the specimen is behind glass and the published photos are all small and coarse-grained.

  2. Strange? How so? Remember, this is only a guess from broken puzzle pieces and comparisons to sisters recovered in the LRT. Perhaps the answer isn’t here, but an attempt here might lead to further studies.

    • Strange in that it has a very strange shape and position for a postfrontal.

      and comparisons to sisters recovered in the LRT

      Ah, there you run the risk of circular logic: first you interpret Pederpes according to its supposed relatives, then you score it that way, then the supposed similarities tie it together in your tree with the relatives you already supposed…

      But Whatcheeria & friends don’t have such a strange postfrontal either. And I only noticed just now that you’ve doubled the parietal! In the photo, the bone you rendered in gray is the temporal series of the right side, not a parietal.

  3. re: the postfrontal – the drawing data I have for Whatcheeria
    http://reptileevolution.com/whatcheeria.htm
    actually has a similar shape and touches the same bones. And Crassigyrinus does so too, but with a deeper cheek. Am I working from old data? What I rendered in gray between the supratemporal and tabular I presumed was part of the endocranium, close to the first cervical.
    re: Circular logic, actually it’s a one-way street in this clade. Crushed bones are difficult to piece back together. The sutures are cracks!

    • The postfrontal of Whatcheeria is damaged; that’s absolutely obvious from Lombard & Bolt (1995: fig. 1A). That’s not surprising – the whole skull is crushed completely flat.

      The V-shaped gap between the supratemporal and the tabular of Pederpes is an obvious crack. In that crack you can see part of the stapes (Clack & Finney, 2005: fig. 1, 4). The whole skull has all kinds of damage (Clack & Finney, 2005: all figures that show the skull, and me, 2014: pers. obs. of the specimen on exhibit in the Hunterian Museum in Glasgow).

      I’ll send you both papers in a few minutes.

      • Done! You should have received a download link from wetransfer.com; it’ll expire in 7 days.

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