Eudibamus update

Earlier we looked at the complete skeleton of Eudibamus based, unfortunately, on low rez data. But we do with what we’re given. Mistakes were made. Today, based on higher rez imagery (Fig. 1) an update is in order. The nesting of Eudibamus at the base of the Diapsida does not change based on this new data. The feet, of course, with those tiny medial digits, are distinctly araeoscelidian. There’s no mistaking those.

Figure 1. Click to enlarge. Eudibamus in situ (above), traced (middle) and reconstructed (below). The revised skull retains a large orbit and has a shorter rostrum.

Figure 1. Click to enlarge. Eudibamus in situ (above), traced (middle) and reconstructed (below). The revised skull retains a large orbit and has a shorter rostrum.

Eudibamus still nests at the base of the new Diapsida (no relation to lizards and kin) and at the base of the Araeoscelida, otherwise including Petrolacosaurus, Araeoscelis, Aphelosaurus and Galesphyrus. Eudibamus also nested close to Tangasaurus at the base of the Enaliosauria and Thadeosaurus at the base of the largely terrestrial Younginiformes.

So this is a key taxon in any large-scale phylogenetic analysis, like the large reptile tree.

Still not sure why this taxon was originally (Berman et al. 2000) assigned to bolosaurids because nothing about that assignment makes sense other than the large orbit and small temporal fenestra. Few postcranial details are available for bolosaurids, but their nearest relatives are bulky plant eaters.

The long neck was broken at mid length with anterior cervicals backed up against the skull occiput. Manual digits 4 and 5 were not preserved or are still buried. Berman et al. (2000) noted the teeth resembled those of bolosaurs. The current data does not provide sufficient resolution to note the shape of the teeth, but sister taxa have numerous small, sharp teeth. If they are blunt in Eudibamus, as they are in bolosaurids, that would be autapomorphic. The five posterior dorsal ribs were more gracile than the anterior ones. No chevrons could be seen, but that may be a resolution issue also.

With such a large orbit, longer than the rostrum, one wonders if this was a nocturnal reptile. As noted earlier, not all the toes were long and tendril-like, so an arboreal lifestyle is not especially indicated. The tibia was longer than the femur, indicating a speedy, perhaps bipedal configuration in the manner of living lizards capable of this. But then, most bipeds have a more symmetric foot. A curious case here.

References
Berman, DS, Reisz RR, Scott D, Henrici AC, Sumida SS and Martens T 2000. Early Permian bipedal reptile. Science 290: 969-972.

paleocritti/Eudibamus
wiki/Eudibamus

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