Rhizodont remains are very rarely articulated and so it has been difficult to reconstruct the cranial anatomy. However, several recent finds by other palaeontologists (see Strepsodus anculonamensis Andrews 1985; Barameda decipiens (Long 1989) and Gooloogongia loomesi Johanson & Ahlberg, 1998) coupled with my further preparation of existing UK material has made it possible.

In the Carboniferous European species (Screbinodus ornatus, Rhizodus hibberti and Strepsodus sp.*) the skull is dominated by its dentition. The upper jaw (including the inner, palatal arcades) had a marginal row of small teeth on the maxilla and premaxilla, medium sized fangs on the ectopterygoid and dermopalatine bones, and large tusks on the vomers and premaxillae. On the lower jaw (mandible) the were marginal teeth on the dentary, with fangs on the three coronoids and a huge tusk at the symphysial tip of the dentary. The mandible also possessed a large ascending process on the prearticular, to aid muscle attachment.

All this would have given rhizodonts an extremely powerful bite. It is unusual, then, that the left and right mandible are 'C' shaped in cross section - they are effectively hollow tubes with the lingual side incomplete. This means that, on biting, the left and right mandibles would rotate inwards towards each other. This may be a kinetic mechanism to dig the marginal teeth more deeply into the prey, to help grip slippery or struggling items. The upper jaw also appears to have been quite kinetic, with loosely fitting bones surrounding a cartilaginous braincase.

This morphology (coupled with what is known of the postcranial anatomy) would have suited a 'grip and drag' hunting technique, where prey was ambushed, the tusks sunk in to secure it, and then (depending on its size) either thrashed on the surface to subdue it, or dragged to where the rhizodont could consume it without being disturbed.

The skull of Screbinodus ornatus


An isolated coronoid of Rhizodus hibberti