Dinosaurs - Wintonotitan wattsi

Introduction

Wintonotitan wattsi, dubbed ‘Clancy’, after a poem by Banjo Patterson, was a primitive titanosauriform and one of three new dinosaurs recently named from the Winton Formation in central Queensland. Wintonotitan and a second titanosaur, Diamantinasaurus matildae, are the first new sauropods from Australia in over 75 years. Titanosaurs, most of which are known from Gondwanan continents, could grow to a massive size. The 15 metre long Wintonotitan was therefore comparatively small for a titanosaur.

Identification

Wintonotitan wattsi was a titanosaur, a group of sauropods known mainly from Gondwanan continents. Titanosaurs, the largest terrestrial animals known, may have reached 35 metres in length and 100 tonnes in weight. Wintonotitan was relatively small for a titanosaur, at up to 15 metres in length and around 10 to 15 tonnes in weight.

Wintonotitan had relatively long front legs (its hind legs have not been found) and was comparatively slender in build. Unique features of Wintonotitan that distinguish it from other basal titanosauriforms include incipiently biconvex distal caudal (tail) vertebrae; anterior caudal neural arches with prespinal laminae; and anterior and middle caudal vertebrae with ventral longitudinal hollows (from the description of Wintonotitan by Hocknull et al., 2009). This list of features is based on the limited amount of material recovered so far, which does not include a skull or dentition.

Habitat

The Winton Formation is made up of sandstones, siltstones and claystones formed during the mid-Cretaceous period (about 100 million years ago). At this time, the region was an extensive river plain filling the lowlands left behind by the retreating Eromanga Sea. The environment would have been a mosaic of large, winding rivers, freshwater pools, billabongs, swamps, lakes and coastal estuaries (a spectacular ‘dinosaur stampede’ was recorded in a mudflat deposit from the Winton area). The climate would have been subtropical to temperate, with marked seasons and abundant rainfall. Fossil plants from the Winton Formation include angiosperms, araucarian conifers, ginkgoes and ferns. Australovenator, Diamantinasaurus and Wintonotitan are from the basal part of the Winton Formation, not far from the type locality of Lovellea wintonensis (an early flowering plant).

Distribution

Wintonotitan is known only from the Winton Formation of central-western Queensland, Australia.

Feeding and diet

The huge size of sauropods, along with features of the skull and teeth, suggest an herbivorous diet for these massive reptiles. However, there is little direct evidence for sauropod diets other than tooth shape and wear facets (not yet known for Wintonotitan).

Edible plants known from the Winton Formation or from other parts of Cretaceous Australia include araucarian conifers, angiosperms, ginkgoes, cycads, ferns and horsetails.

Fossils description

Fossils of the sauropod now known as Wintonotitan were first discovered in the 1970s by Keith Watts, who donated the material to the Queensland Museum (the specific name, wattsi, honours Watts for his discovery). These bones (partial front limbs and tail vertebrae) were excavated in the 1980s by the Queensland Museum and were first thought to be those of Austrosaurus mackillopi from Queensland, at that time the only named Cretaceous Australian sauropod. More material of the same species was found in 2004 and 2006 at Elderslie Station, about 60 km north-west of Winton. This material was excavated and prepared in a joint Queensland Museum-Australian Age of Dinosaurs project (additional material includes vertebrae and part of the pelvic girdle, or hip).

Wintonotitan is now represented by most of the front limb and shoulder girdle, thoracic and caudal vertebrae, partial ribs, and partial hip bones (left scapula, partial right and left humeri and ulnae, partial right and near complete left radii, near complete right metacarpus (front foot) with complete metacarpals II-V and proximal half of metacarpal I, fragmentary dorsal and sacral vertebrae and ribs, partial right ilium, right ischium, and caudal vertebrae series (including anterior, middle and posterior series as well as proximal chevron bones). Additional unidentified or fragmentary fossils of Wintonotitan have also been recovered. Wintonotitan (QMF 7292) is held by the Queensland Museum in Brisbane, Queensland. Referred material (QMF 10916: isolated middle and posterior caudal vertebrae) was found near Chorregan, Queensland.

Evolutionary relationships

Wintonotitan is placed as a basal titanosauriform outside of Titanosauria. It appears to be closest to either Phuwiangosaurus (from the Early Cretaceous of Thailand) or Malarguesaurus (from the Late Cretaceous of Argentina). Wintonotitan is only distantly related to Diamantinasaurus, a more advanced lithostrotian titanosaur.
Fossilized sauropod footprints left along the Broome coastline in Western Australia provide evidence that other sauropods lived in Australia during the Early Cretaceous. Judging from the size of the footprints (the largest of which is 1.5 metres across: Thulborn et al. 1994), these sauropods were probably also titanosaurs, but at least some were much larger than either Wintonotitan or Diamantinasaurus.

References

• Curry Rogers, K. 2005. Titanosauria: a phylogenetic overview. Pp. 50-103 in Curry Rogers, K. and Wilson, J. A. (eds) The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley.
• Hocknull, S. A., White, M. A., Tischler, T. R., Cook, A. G., Calleja, N. D., Sloan, T. and Elliott, D. A., 2009. New mid-Cretaceous (latest Albian) dinosaurs from Winton, Queensland, Australia. PloS One 4(7), e6190.
• Molnar, R. E., 2000. A reassessment of the phylogenetic position of Cretaceous sauropod dinosaurs from Queensland, Australia. Pp. 139-144 in Leanza, H. A. (ed) VII International Symposium of Terrestrial Ecosystems. Asociacion Paleontologica Argentina Publicacion Especial No. 7 Buenos Aires: Asociacion Paleontologica Argentina.
• Molnar, R. E. and Salisbury, S. W. 2005. Observations on Cretaceous sauropods from Australia. Chapter 20 in V. Tidwell and K. Carpenter (eds) Thunder-Lizards: The Sauropodomorph Dinosaurs (2005). Indiana University Press, Bloomington. Pp. 454-465.
• Salgado, L., Calvo, J. L. and Coria, R. A., 1997. Evolution of the titanosauriform sauropods. I. Phylogenetic evidence based on the postcranial evidence. Ameghiniana 34, 3-32.
• Thulborn, R. A. and Wade, M., 1984. Dinosaur trackways in the Winton Formation (mid-Cretaceous) of Queensland. Memoirs of the Queensland Museum 21, 413-517.
• Thulborn, R. A., Hamley, T. and Foulkes, P., 1994. Preliminary report on sauropod dinosaur tracks in the Broome Sandstone (Lower Cretaceous) of Western Australia. Gaia 10, 85-94.
• Upchurch, P., Barrett, P. M. and Dodson, P., 2004. Chapter 13: Sauropoda, pp. 259-322 in Weishampel, D. B., Dodson, P. and H. Osmólska, H. (eds) The Dinosauria, Second Edition. University of California Press, Berkeley.
• Wilson, J. A., 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136, 217-276.

Further reading

• Long, J. A. et al. 2002. Dinosaurs of Australia and New Zealand and Other Animals of the Mesozoic Era. New South Wales University Press, Sydney.
• Salisbury, S. W., 2002. A giant awakes. Australian Geographic 65, 100-105.
• Salisbury, S. W., 2003a. Clash of the titans: the world’s largest dinosaurs. Nature Australia 27(7), 44-51.
• K. Curry Rogers and J. Wilson (eds). 2005. The Sauropods – Evolution and Paleobiology. University of California Press, Berkeley.
• V. Tidwell and K. Carpenter (eds). 2005. Thunder-Lizards: The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington.