Australia: The Land Where Time Began

A biography of the Australian continent 

This family of temnospondyl labyrinthodonts contains most of the genera of Australian fossil amphibians from the Triassic and Jurassic. Characteristic features of Brachyopidae are a short, broad skull, large orbits near the anterior. There is either no otic notch or it is very shallow. The tabular bones are short, broad and lack tabular horns.

The original description of Brachyops was a head only fossil from Mangali, India. The first Australian form was found in erosion gullies near Duckworth Creek in south-west Queensland. The skull was originally classified as a Brachyops but later reclassified as a Xenobrachyops. The skull was 11 cm long and 14 cm wide, had several large fangs. The skull was wider than long, shallow at the front and deep at the rear, as is normal with other brachyopids, but there were also several features that distinguished it from the brachyopids. Among these were the proportions of the skull and the size of certain bones and the relative sizes of the interpterygoid vacuities of the palate. A primitive feature of Xenobrachyops is that the occipital condyles are almost level with the jaw articulation. After a recent reconstruction of the skull roof and palate it was concluded that it was closely related to Sinobrachyops from the Jurassic of China, in fact that they are so closely related that they might actually constitute their own separate family.

Austropelor wadleyi was found in the bed of the Brisbane River near Lowood Station, south central Queensland. Both these animals lived about 30 million years after the labyrinthodonts were thought to have become extinct, but there is also a Jurassic labyrinthodont from China.

It is known from a single fragmentary lower jaw, so its assignment to a separate genus is uncertain. Its jaw is similar to that of Siderops, but could also have been assigned to the Chugitosauridae.

Notobrachyops picketti from the Ashfield Shale, Winamatta Group, Hurstville Brick Company quarry at Mortdale, Sydney area, New South Wales.

This genus is known from a single impression of the skull roof and lower jaw. The skull, which had an undulating appearance, was 35 mm long, indicating the total length was about 30 cm. It was a small brachyopid with a narrow skull roof, broadest across the quadratojugal bones which was 0.9 times the length along the midline. The bones composing the skull roof each had a raised centre and depressed margins. As it was from the Upper Triassic it is the latest known survival of a labyrinthodont.

Blinasaurus henwoodi from the Blina Shale in Erskine Ranges about 90 km east of Derby, Western Australia. This species was described from an almost complete skull and lower jaw. The skull was about 12 cm long, indicating that the animal was about 60-70 cm long. It probably fed mostly on small fish in the ancient streams of the Kimberley. The head is rounded in top view and had a large broad snout with large orbits. The upper margin of the mouth has a border of large fangs.

Blinasaurus townrowi from the Knocklofty Formation, Old Beach Site on the Derwent River about 3 km north of Hobart, Tasmania. Represented by a well-preserved skull and isolated bones. The skull is about the same size as B. henwoodi but differs in a number of minor features.

Blinasaurus wilkinsoni, earlier called  Platyceps wilkinsoni, from the Narrabeen Group, Railway Ballast quarry, near Gosford, New South Wales. The skull was about 3 cm long. It is believed that it is a separate small species and not a juvenile individual. The orbits are proportionately smaller in B. wilkinsoni than in B. henwoodi. Juvenile labyrinthodonts usually had proportionately larger orbits than in the adults. At the time of writing it has been suggested that Blinasaurus is actually synonymous with another brachyopid, Platycepsion.

Xenobrachyops allos, from the Arcadia Sandstone near the headwaters of Duckworth Creek, southwest of the township of Bluff in south-central Queensland.

Sources & Further reading

1. John A Long The Rise of Fishes - 500 Million years of Evolution, University of New South Wales Press, 1995

See Phylogeny of Australian temnospondyl labyrinthodonts

Amphibians

Ampibian Deposits