Crushed fossils missing some of the middle/connecting bones give paleontologists several options for restoration. Case in point: Cutleria (Figs. 1, 2) a very basal therapsid. We looked at this specimen/taxon earlier here and here.
The first restoration aligns the ventral maxilla in a straight line. Note the very deep reflected lamina on the angular, sharply angled from the dentary.
The second restoration (Fig. 2) is the more conservative (more like the in situ fossil) producing a deeper, ventrally convex maxilla. Note the reflected lamina of the angular is not so deep here. In both cases the mandible needs to mate to the maxilla, so it changes in each case, enabled by the mid-length break.
Which one is more correct?
Factors to consider:
- Ancestral taxa (like Haptodus and Ophiacodon) have a shallow reflected lamina.
- Descendant taxa (like Biarmosuchus) have a deeper reflected lamina; but then
- Other descendant taxa (like Stenocybus) have a shallow reflected lamina.
- Descendant taxa (like Haptodus and Ophiacodon) have a convex maxilla.
- Descendant taxa (like Biarmosuchus have a less convex to straight maxilla.
- Other descendant taxa (like Stenocybus, dromasaurs, dicynodonts and other therapsids) have a convex maxilla.
- Version 2 requires less bone movement.
- Version 1 requires less ‘putty’ to fill in holes left by missing bones. The puzzle pieces fit tighter.
- The strong posterior lean of the lateral temporal fenestra is not present in either ancestral or descendant taxa and it probably reflects the angle of the mandible adductor.
Your opinion or insights would be appreciated.