Australia: The Land Where Time Began

A biography of the Australian continent 

Lepidosauria - Class REPTILIA

Order Squamata

?Paliguanidae

Kundu mackinlayi, Lower Triassic, from The Crater, the Arcadia Formation, Rewan Group, 72 km SW of Rolleston, south central Queensland

This species is known only from a small partial skull in a red mudstone nodule. The anterior part of the snout and the posterior region of the skull are missing. It is estimated the skull was about 20 cm long. Its appearance it would been very much like typical modern lizards. It was demonstrated to be a true lizard by the presence of a lacrymal bone between the nasal bone and the maxilla.

Order Eosuchia

These had 2 large holes on on each side of a diapsid (condition of reptilian skulls, 2 fenestrae (openings) behind the orbit) type skull. Eosuchians include the Lepidosaurs, the earliest, most primitive members of the lizard-like reptiles.

Prolacertidae

This group of reptiles are not well-defined. In overall form they are lizard-like, the hind limbs slightly longer than the arms for short bursts of bipedal running. This characteristic became a feature of advanced archosaurs, eventually leading to the rise of the dinosaurs.

Kadimakara australiensis, Lower Triassic, The Crater, the Arcadia Formation, Rewan Group, 72 km SW of Rolleston, south central Queensland. Some think this species was insectivorous. A lower temporal bar is absent and the the lachrymal bone tapers out at the nasal bone, separating the prefrontal and maxilla bones. There is a tetraradiate squamosal and a gap between the pterygoids that accommodates the parasphenoid.

The single incomplete skull has been estimated to be about 35 cm long, by comparison with the similar appearing African  Prolacerta.

Subclass Archosauria

This group contains thecodonts, dinosaurs, crocodilians and birds.

Order Thecodonta

Proterosuchidae

Some of the features that characterised this family are triple-headed ribs and teeth not completely anchored to the jawbone (subthecodontian teeth). They were mostly aquatic predators living around ponds, and swimming was their main form of locomotion.

Kalisuchus newmensis, Lower Triassic, The Crater, the Arcadia Formation, Rewan Group, 72 km SW of Rolleston, south central Queensland and Duckworth Creek, the Arcadia Formation, Rewan Group, NW of Rolleston, south central Queensland.

This species is known from a number of fragmentary bones - skull bones, vertebrae, limb and girdle bones. This is the oldest archosaur known from Australia. The skull is known from a jugal bone, a partial skull roof and fragments of the upper and lower jaws. The calcaneum (ankle bone) is very similar to that of crocodiles. It is believed to have been a crocodile-like predator closely related to the Chinese and African genus Chasmatosaurus. Its body has been estimated to have been about 3 m long. Among thecodonts it is characterised by its crocodile-like calcaneum. There is a maxillary shelf in the upper jaw that suggests it had a broad snout. The limb bones are slender and the neck is relatively long for a proterosuchian.

Tasmaniosaurus triassicus, Early Triassic, Crisp and Gunn's quarry at the head of Arthur St, West Hobart, Tasmania (Poets Road member of the Knocklofty Formation).

This the most complete Australian Triassic reptile, as well as the most complete fossil reptile from any period in Australia. It appeared lizard-like, and was about 1 m long. Some small labyrinthodont bone fragments were found associated with the ribs. It has been assumed the lamyrinthodont might have been its last meal.

It had a long, slightly curved premaxilla, no parietal foramen, vertical quadrate, vacuity at the posterior end of the dentary, shallowly amphicoelous vertebrae, long double-headed cervical ribs, long limbs and feet, and no bony scutes. It is the only member of the group to retain the interclavical, making it the most primitive member. The skull has a narrow snout with antorbital fenestra with a rounded anterior margin, differing from the square ones of Kalisuchus. The premaxilla has an unusually large number of teeth.

Order Saurischia

Prosauropodidae

Prosauropods had long necks and tails, and mostly walked upright. They gave rise to the sauropods, the largest land animals that ever lived, such as Brachiosaurus ands Diplodocus. They were large omnivorous dinosaurs of the Triassic, some were carnivorous but others became herbivores.

Agrisaurus macgillvaryi, Late Triassic-Early Jurassic, from the northern Queensland coast, possibly near the tip of Cape York. They were discovered by the crew of HMS Fly and the exact location of the find is unknown and the age is uncertain, it is even uncertain if they actually came from Australia. The remains are a well-preserved tibia, a claw, and other fragments collected by the ship's crew in 1844 and taken to England. In the late 1980s the original block of stone was prepared further at the National History Museum in London and more small bones such as a small vertebra were found.

The tibia has been used to characterise it among the prosauropods. The dorsal surface is much longer antero-posteriorly than across the anterior width. There is a well-defined notch for the astragalus on the distal end of the tibia.

Order Theropsida

Suborder Dicydontia

?Lystrosauridae

Indeterminate indeterminate, Early Triassic, The Crater, the Arcadia Formation, Rewan Group, 72 km SW of Rolleston, south central Queensland

The species is known from a single bone fragment, part of the quadrate (upper jaw) joint is of characteristic shape of some of the mammal-like reptiles. This enabled the identification of the Australian species with its close relative Lystrosaurus from the Triassic of South Africa.

Among other therapsid bones from the same site are part of a large canine tusk, 2 small vertebrae, and a skull fragment. The dicynodonts bone fragments are from herbivorous reptiles with large canine tusks. It is believed the tusks were used for digging up roots, defence, and possibly mating rituals. They were heavy-built animals with an average size similar to sheep. The quadrate bone of dicynodonts is in the form of a double knuckle to that the lower jaw articulated in an almost pulley-like fashion.

Sources & Further reading

  1. Long, John A, 1998, Dinosaurs of Australia and New Zealand, University of New South Wales Press.

 

Author: M. H. Monroe
Email:  admin@austhrutime.com
Last updated  08/02/2012
 
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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading