A scientific paper has just been published describing the fossilised remains of a juvenile titanosaur from the Winton Formation of Queensland, Australia. The specimen has been assigned to the Diamantinasaurus taxon (D. matildae) and it represents the smallest sauropod described from fossils found in Australia to date.

Reconstructed skeleton of the juvenile Diamantinasaurus (D. matildae) compared to a human skeleton.
A model of the reconstructed skeleton of the juvenile Diamantinasaurus (D. matildae) compared to a human skeleton. The young dinosaur is estimated to have weighed around 4.2 Tonnes. Picture credit: Australian Age of Dinosaurs Museum.

About Ten Percent of the Skeleton Recovered

The fossils were discovered on Elderslie Station land which lies some 35 miles northwest of the town of Winton (Queensland). Landowners noticed fragments of a femur and dorsal ribs exposed on the surface (2012). Staff from the Australian Age of Dinosaurs Museum along with volunteers excavated the site and found the remainder of the fossil material representing about 10% of the total skeleton about a metre below the surface.

The postcranial material consists of cervical ribs, three incomplete dorsal vertebrae, sacral vertebrae and limb bones.

Views of the juvenile Diamantinasaurus fossils (AODF 663) a right humerus and right manual ungual with accompanying digital models.
Views of the juvenile Diamantinasaurus fossils (AODF 663) a right humerus and right manual ungual with accompanying digital models. Right humerus photographs in A, dorsal, B, anterior, C, ventral, D, medial, E, posterior, F, lateral views. Right humerus digital models in G, dorsal, H, anterior, I, ventral, J, medial, K, posterior, L, lateral views. The right manual ungual in M, proximal, N, dorsal, O, anterior, P, ventral, Q, posterior views. Right manual ungual digital models in R, proximal, S, dorsal, T, anterior, U, ventral, and V, posterior views. Note scale bar for humerus equals 10 cm and for the manual ungual 5 cm. Picture credit: Rigby et al.

A Young Titanosaur from the Late Cretaceous

Although age estimates for the Winton Formation vary, it has been informally divided into lower and upper members, with the Diamantinasaurus material coming from the “upper” portion which is regarded as Cenomanian to potentially the lowermost Turonian stages of the Late Cretaceous (approximately 95-89 million years ago).

The study of the juvenile titanosaur was led by Museum Research Associate Samantha Rigby who is undertaking a Master of Science (Research) at Swinburne University of Technology (Victoria, Australia), under the supervision of Dr Stephen Poropat who was one of the co-authors of the scientific paper published in the Journal of Vertebrate Palaeontology. Each bone from the specimen was scanned to create three-dimensional models to digitally compare them with other sauropod remains.

This comparison suggests the small specimen belongs to the Diamantinasaurus taxon though with juvenile characteristics, vertebrae which are unfused, minimal muscle scarring on the bones, smooth bone texture and marked proportional bone size differences when compared to adult titanosaur material.

Diamantinasaurus dorsal vertebrae and digital models.
Diamantinasaurus juvenile dorsal vertebrae with digital models. Dorsal vertebra photographs in A, dorsal, B, right lateral, C, anterior, D, left lateral, E, posterior views. Dorsal vertebra digital models in F, dorsal, G, right lateral, H, anterior, I, left lateral, J, posterior views. Note scale bar equals 10 cm. Picture credit: Rigby et al.

Allometric Growth

The fossil specimen (AODF 663) nicknamed “Oliver” is only the third specimen to be referred to the taxon Diamantinasaurus matildae. D. matildae was formally named and described in 2009: A Trio of New Dinosaurs from Down Under. The research team found that the bones of this small titanosaur grew allometrically, meaning that its bones changed shape and different parts of its body grew at different rates.

The limb bones are also narrower in width when compared to other Diamantinasaurus limb bones from older individuals. This suggests that as this titanosaur grew its limb bones became thicker and more robust to help support its enormous bulk.

A Juvenile Diamantinasaurus

Fossils of juvenile titanosaurs are rare and it is hoped that “Oliver” will provide important insights into the ontogeny of titanosaurs.

Everything Dinosaur acknowledges the assistance of a media release from the Australian Age of Dinosaurs Museum in the compilation of this article.

The scientific paper: “A juvenile Diamantinasaurus matildae (Dinosauria: Titanosauria) from the Upper Cretaceous Winton Formation of Queensland, Australia, with implications for sauropod ontogeny” by Samantha L. Rigby, Stephen F. Poropat, Philip D. Mannion, Adele H. Pentland, Trish Sloan, Steven J. Rumbold, Carlin B. Webster and David A. Elliott published in the Journal of Vertebrate Paleontology.

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