Bothriceps major Woodward, 1909

Warren, Anne, 1997, A tetrapod fauna from the Permian of the Sydney Basin, Records of the Australian Museum 49 (1), pp. 25-33 : 27-30

Bothriceps major Woodward, 1909

This specimen ( Fig. 3 ) which was recovered from the Commonwealth Oil Corporation's shale mine at Airly, near Capertee in the west of the Sydney Basin is preserved in three pieces distributed in three different repositories as follows: head, Geological Survey ofNew South Wales, Sydney, MMF l2697a; body, Australian Museum, Sydney, AM F 50977 ; counterpart head and body, Natural History Museum, London, BM(NH) R3728.

Woodward (1909) recognised the specimen as a brachyopid amphibian, placing it in the same genus as B. australis , presumably because they were both Australian, but decided to separate it specifically because of a difference in the size of its orbits, those of B. major being relatively smaller.

Watson (1956) transferred the specimen to a new genus, Trucheosaurus , largely because in the few structures clearly shown in the only known specimen it differs from the type of the genus Bothriceps and indeed from all other known genera of the family" and also because "the specimen is important as showing the occurrence of a typical brachyopid at an early horizon".

The name Trucheosaurus , from the Greek for rags and tatters, reflects Watson's opinion of the state of preservation of the specimen. It was returned to Bothriceps by Welles and Estes (1969). All three blocks of B. major are currently being restudied by Dr C. A. Marsicano and myself; we intend removing B. major from the family Brachyopidae .

Stratigraphic position. The torbanite from which B. major originated is in the Glen Davis Formation of the Charbon Subgroup, a lower deltaic facies of the Late Permian Illawarra Coal Measures (Eui Kyoo Yoo pers. com., 1995). Palynological evidence indicates that the Glen Davis Formation is older than Tatarian but not older than Kazanian ( McMinn, 1985; Foster pers. com., 1995). Thus B. major is indeed Permian and stratigraphically the earliest recorded member of the stereospondyl radiation.

New material from West Wallsend

A rock fall in 1984 from the roof of the Borehole Seam at the West Wallsend Colliery owned by Oceanic Coal Australia Ltd. was recognised by mining engineer, Bruce Ross, as containing fossil vertebrates. These are preserved in concretions within a highly carbonaceous shale and have been dorsoventrally compressed and partially metamorphosed so that little detail of their anatomy remains. All appear to have been split through the centre of the specimen so that none present a dorsal or ventral aspect. While the majority of the specimens are fish, as indicated by the presence of lepidotrichia and scales, four concretions appear to contain tetrapod remains.

AM F9542l, AM F95122 . These specimens (Figs 4, 5) are part and counterpart of a boomerang shaped concretion which contains most of a tetrapod vertebral column with attached ribs. It is possible to count approximately 24 presacral vertebrae and about ten caudals. A count of between 23 and 26 is typical of the few temnospondyls in which an articulated column is preserved and a similar range is found in early reptiles ( Romer, 1956).

Anteriorly the column is twisted so that neural arches are visible as well as ribs. Here several vertebrae appear typically rhachitomous; neural arches articulate with large pleurocentra separated by smaller intercentra. Posterior to the eighth neural spine the column twists so that it is seen in frontal section, with symmetrically arranged ribs. At centrum twenty four the column again twists revealing two neural arches in the same section as ribs. This part of the column may be immediately postsacral; tetrapods typically have a postsacral area which is rib bearing before the haemal arches begin and the ribs are lost. The final two centra preserved appear to bear haemal arches as well as neural arches.

Beneath vertebrae five and six three bones may be parts of the anterior limb or they could be expanded pectoral ribs.

This specimen appears to be a temnospondyl amphibian as evidenced by the rhachitomous appearance of several of its more anterior vertebrae.

AM F97240 (Fig. 6A). Unfortunately the counterpart of this small concretion was not recovered. An articulated but buckled section of vertebral column is represented by approximately fifteen centra at least five of which are associated with ribs. It is not possible to tell whether these represent rhachitomous or stereospondylous centra, or whether they are from temnospondyls or amniotes.

AM F97241 (Figs 6B, 7). Potentially the most complete of the collection, this specimen, which is preserved in part and counterpart, includes what appear to be cranial and mandibular remains as well as centra, ribs, and possible skin impressions.

A single tooth associated with the mandible is longitudinally infolded in its lower half indicating probable temnospondyl affinity. Although the bones associated with this tooth together define the shape of a mandible none can be positively identified as individual mandibular elements.

Some of the presumed cranial bones are ornamented, with fine ridges radiating from the centres of ossification. No midline symmetry can be found among these elements and none can be named. Individual bones are larger than expected if they are considered to belong to a skull associated with the

mandible and together they occupy too large an area for such a skull. Therefore it is likely that elements of the pectoral girdle are also present.

The two vertebral centra associated with AM F97241 could be rhachitomous or stereospondylous.

Dimpled areas of sediment (Fig. 7) adjacent to the bone in this and AM F97243 may be impressions of soft body parts but equally could be cleavage patterning. They are not present elsewhere on the block of sediment or in the other specimens. Their indentations are too irregular in arrangement to be marks left by small scales and they may be skin impressions.

This specimen is identified as most likely to be a temnospondyl amphibian on the basis of its infolded teeth. Some fish, notably some sarcopterygians, shared folded teeth with early tetrapods, but the last known of these was Ectosteorachis from the Early Permian. Rarely, actinopterygians may have folded teeth. The absence of lepidotrichia or fish-like scales associated with the specimen suggests that it is not an actinopterygian, and the vertebral centra are rather large and heavily ossified for a fish.

AM F97242 (Fig. 6C). While this concretion did not split cleanly through the specimen, so that it is fragmented into five main blocks, the colour differentiation is better. Possible cranial material, vertebrae, ribs and limb elements are present. The cranial segment is traversed by a groove which could be a sensory canal and has a raised area which may be a centre of ossification adjacent to the groove. Two slightly curved lateral margins could be the posterolateral borders of interpterygoid vacuities if the element is a parasphenoid. On the other hand they could define the stem of an interclavicle!

The centra look more reptilian than amphibian, being spool-shaped with one or both ends concave as some sections are solid and others bear a central perforation of varying diameter. Mesozoic temnospondyls sometimes have such centra but Palaeozoic temnospondyls do not, and reptiliomorph amphibians, which do have spool-shaped centra, have not been found in the Southern Hemisphere.

All limb remains, except one, have flattened rather than rounded ends and could be temnospondyl or reptile.

Their size indicates that they are distal limb elements or metapodials.

AM F97243 . All remains on this fragmented block are carbonised and difficult to differentiate from the matrix. It appears to be a partial articulated vertebral column with associated ribs.

Stratigraphic position. The Borehole Seam is the lowermost part of the Lambton Subgroup and lies

immediately above the Waratah Sandstone which forms the base of the Newcastle Coal Measures in the Newcastle area ( McMinn, 1985). The Borehole Seam is Kazanian in age ( Diessel, 1980). On McMinn's palynostratigraphic correlation of the Upper Permian of the Sydney Basin (1985, fig. 3) it is a little younger than the Glen Davis Formation from which the temnospondyl, Bothriceps major , was recovered.

Figures

Fig. 3. The temnospondyl amphibian Bothriceps major; head MMF12697a, body AM F50977.