148 



C.A. MARSICANO AND A. WARREN 



Fig. 1 Trucheosaurus major, holotype MMF 12697a. Skull. Scale bar represents 20 mm. 



Diagnosis. Rhytidosteid amphibian apparently lacking tabular 

 projections and otic notch; markedly small orbits located laterally on 

 the anterior third of the skull table; extremely anteroposteriorly 

 elongated parietal bones, which are nearly three times the length of 

 the frontals and apparently without pineal foramen. 



Holotype. Skull table (MMF 1 2697a), the partially complete and 

 articulated postcranial skeleton (AMF 50977), and the counterpart 

 of both skull and postcranial skeleton (BMNH R3728). 



TYPE LOCALITY AND HORIZON. Glen Davis Formation of the 

 Charbon Subgroup, the lower deltaic facies of the Illawarra Coal 

 Measures, Airly, near Capertee in the west of the Sydney Basin ( New 

 South Wales, Australia). The whole of the Illawarra Coal Measures 

 are Late Permian (Young & Laurie 1996). The Glen Davis Forma- 

 tion, which is placed mid-way through the Illawarra Coal Measures 

 (McMinn 1985), contains the palynomorph Microreticulatisporites 

 bitriangularis, the index form for the base of the APP5.2 Interval 

 Zone (Burgerem/. 1992), making it middle Dzhulfian.This Dzhulfian 

 correlation for the middle part of the Illawarra Coal Measures was 

 confirmed in the most recent survey of evidence for the placement of 

 the Permo-Triassic boundary in Australia (Foster et al. 1997). 



Description 



Skull. As mentioned above, the specimen is only preserved as a thin 



layer of bone on two slabs (part and counterpart). Although obvi- 



ously part and counterpart of the same specimen, the two halves do 

 not meet cleanly when fitted together as several millimetres of the 

 bone is missing in places. 



Determining sutures was difficult as little detail remains, perhaps 

 because the specimen was preserved in a torbanite. The clearest 

 sutures are in the area of the left tabular, postparietal, supratemporal. 

 parietal, postfrontal and postorbital. The other sutures were deline- 

 ated following the pattern of the bone radiation, although in the 

 anterior snout region sutures remain fairly unclear. Suture lines were 

 traced with chalk on the part and counterpart (Figs 1, 2) and the 

 specimens drawn (Figs 3,4). The drawings were then superimposed 

 and the skull redrawn as a composite (Fig. 5). The main problem 

 encountered during our restoration was determining the position of 

 the orbits, which have been restored in the only possible place. The 

 nostrils are marked by raised areas. Apparent ornamentation pre- 

 served is faint but seems to show a delicate and smooth spider-web 

 pattern with small nodes on the ridges. 



The skull table is nearly straight sided, with the posterior margin 

 lacking both tabular projections and otic embayment. The orbits 

 must have been very small, and located laterally on the anterior third 

 of the skull table. There is no sign of a pineal foramen. A striking 

 feature of the specimen is the extremely anteroposteriorly elongated 

 parietal bones, which are nearly three times longer than the frontals. 

 Apparently, there is no lachrymal bone. 



Part of the occiput is visible behind the posterior border of the 



