TRUCHEOSAURUS MAJOR AND REASSESSMENT OF THE RHYTIDOSTEIDAE 



149 



Fig. 2 Trucheosaurus major, holotype BMNH R3728. Skull. Scale bar represents 20 mm. 



skull table, presumably owing to the dorso- ventral compression of 

 the specimen. A slender left paroccipital process is the best pre- 

 served part of the skull. It shows a clear tabular-exoccipital suture 

 close to the area of the exoccipital condyle. Part of the descending 

 portion of the left postparietal is also preserved. Posteriorly to the 

 postparietals, a layer of bone is present and presumably could be 

 either part of the palate ( ? parasphenoid) or part of the pectoral girdle 

 (? interclavicle). It has been omitted from the figures but can be seen 

 in the photographs (Figs 1, 2). 



On the posterior left corner of the skull, a fragment of bone 

 projects behind the putative quadratojugal. It either represents part 

 of an extension of the quadratojugal or is part of the mandible. In Fig. 

 5, we have restored it as a quadratojugal. 



Postcranial skeleton. Parts of the right fore and hind limb and at 

 least 31 presacral and postsacral centra are preserved, with accom- 

 panying ribs (Fig. 6). 



The condition of the vertebrae is such that they are most easily 

 counted by means of the clearly defined ribs. In the anterior part 

 of the column the section is frontal, with both left and right ribs 

 from 21 centra preserved. More posteriorly, a flake of torbanite 

 containing 5 ribs is missing from the right side. Following this. 



the section changes so that it preserves part ribs, only, on the left 

 and seven apparent centra with accompanying neural arches on 

 the right. Next are three structures which resemble swept back 

 neural spines from a tail fin with the final two vertebrae repre- 

 sented by poorly defined centra The column is certainly 

 rhachitomous in the caudal region but could be rhachitomous or 

 stereospondylous more anteriorly. 



The ribs themselves are shorter than usual for temnospondyls. In 

 the anterior part of the column they are curved but the curvature is 

 not preserved posteriorly. No indication of uncinate processes is 

 present on any rib. 



The humerus, radius and ulna of the right fore limb are partially 

 preserved close to their expected positon. as are several other small 

 displaced elements. Two long bones either side of the vertebral 

 column in this area may be the remains of a displaced left fore limb 

 or partial pectoral girdle elements. The right hand element was 

 labelled 'x' by Woodward (1909). 



More posteriorly, several patches of bone are preserved on the 

 right and may be the tibia and fibula of both hind limbs as well as 

 some metapodials. There is no sign of the femora. 



