Austrosaurus Mckillopi
Longman 1933

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Austrosaurus
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Information
PRONOUNCED
    Os-troh-saw-rus
MEANING
    Southern reptile
CLASSIFICATION
    Titanosauroidea, Sauropoda, Sauropodomorpha
AGE
    Earliest Late Cretaceous (Aptian/Cenomanian) 97-99 MYA
FORMATION
SIZE
    15 metres (50 feet) long, 4 metres (13 feet) at hip
LOCATION
    Maxwelton, Queensland

Austrosaurus mckillopi was described by Heber Longman of the Queensland Museum in 1933. The fossil remains were first noticed by the overseer Mr H.B.Wade in 1932 and their existance was mentioned to Mr H.J.McKillop, then manager of Clutha Station near Maxwelton in Queensland. The manager showed the remains to his brother, Dr M.J.McKillop, who forwarded them to the Queensland Museum in January of 1933. The area is known for its marine reptile remains such as plesiosaurs, pliosaurs and ichthyosaurs, and it was anticipated that the vertebrae would be from one of these. Instead they turned out to be from a sauropod dinosaur. Their presence in ancient ocean deposits was seen as confirmation that sauropods spent a lot of time in or around water, perhaps to help take the weight off their legs. Such theories have since been abandonded, and in fact it now seems that sauropods deliberately avoided swampy areas, prefering dry firm ground.

The type fossil of Austrosaurus consists of three large blocks of matrix containing dorsal vertebrae and rib fragments. The vertebrae had spent quite some time in the top soil zone and so had been badly damaged by weathering and the roots of plants. This is a common problem in much of Australia, where ancient fossil soils erode so slowly that fossils may be completely broken up in the top soil zone before being fully uncovered, and thus being lost forever. Although dated to the Early Cretaceous the vertebrae are quite primitive, lacking many of the weight saving features of more advanced sauropods. Additional specimens found in 1959 on Alni Station, north-west of Maxwelton, consist of the fragmentary remains of five individuals that have all been classified as Austrosaurus sp. The most complete individual, F7292, consists of caudal vertebrae, partial ulnae, partial radii, partial humeri, a partial scapula, a possible illium fragment, metacarpals and rib fragments.

The reconstruction shown here is taken mostly from specimen F7292, one of the five found in 1959, with the femur taken from F3390 and scaled up according to the ratios of the reconstructed lengths of the humerii of each specimen. One noticable characteristic of the Austrosaurus sp material is the elongated forelimbs and massive metacarpals (wrist bones). My measurements give Austrosaurus a height of approximately 3.9 metres at the hip and 4.1 metres at the shoulder, which would have given it an almost level back like Camarasaurus or Shunosaurus with perhaps a slight upwards slope towards the neck. Accordingly I have kept the neck short after these species. The head is my invention, since it is unknown from fossil material, and is vaguely titanosaurid.

Austrosaurus was initially classified as Cetiosaurinae, which seems to be a common placement of problem sauropods. However the vertebrae of Austrosaurus are much more solid and primitive than those known for Cetiosaurus, or for any other sauropod dating to the Cretaceous. It is the primitive vertebrae that distinguish this as a separate species to the only other well known Australian sauropod, Rhoetosaurus brownei from the Middle Jurassic. Ironically the vertebrae of Rhoetosaurus, one of the earliest known species of sauropod, are much more "advanced" than those of the younger Austrosaurus, with hollows and buttresses within them that help make them lighter while not sacrificing strength. Austrosaurus has since been shown to be related to the Titanosaurs, a group of (mostly) Southern Hemisphere sauropods characterised by (among other things) armoured scutes embedded within the skin.



Plates from Coombs and Molnar 1981


Coombs, W.P. Jr and R.E.Molnar 1981 Sauropoda (Reptilia, Saurischia) from the Cretaceous of Queensland. Memoirs of the Queensland Museum 20(2):351-373

Longman, H.A. 1933 A new dinosaur from the Queensland Cretaceous. Memoirs of the Queensland Museum 13:133-144.


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