New Study Suggests Saturnalia Had a Small Head

The South American sauropodomorph Saturnalia (S. tupiniquim) lived some 233 million years ago.  As dinosaurs go, this 1.4 metre long animal might not be regarded as a superstar of the Dinosauria, it is not likely to be offered a starring role in any new instalment of the Jurassic Park movie franchise, but for palaeontologists, Saturnalia is a very significant dinosaur indeed.  Described twenty years ago, the skeleton of this little dinosaur demonstrates both sauropod and theropod traits and as such, any additional information gleaned about it can cause quite considerable shock waves in palaeontological circles.

A Life Reconstruction of Saturnalia tupiniquim

Picture credit: Rodolfo Nogueira

New Study Published in the Journal PLOS One

Scientists from the Universidade de São Paulo in collaboration with a colleague from the Universidade Federal de Santa Maria have published a new study of the skull shape and size of Saturnalia in the on-line academic journal PLOS One.  The research team conclude that Saturnalia had a skull less than 10 centimetres in length, quite small in relation to the size of the animal.  Because it had a long neck and a small, lightweight skull, Saturnalia may have been able to move its head very quickly, helping it to secure tiny, elusive prey.  This idea is also supported by a study of the teeth of this dinosaur and brain shape inferred from an analysis of the skull bones.

The Skull of Saturnalia

Picture credit: Rodolfo Nogueira

Saturnalia with a Reduced Skull

Computerised microtomography was used to assess the shape and structure of the delicate skull fossils still entombed inside their rock matrix.  This non-destructive technique enabled the research team to reconstruct the skull of this dinosaur and to identify the reduced skull.

One of the authors of the scientific paper, Mario Bronzati, postdoctoral fellow at the Department of Biology at the Ribeirão Preto School of Philosophy, Sciences and Letters (Universidade de São Paulo, Brazil) commented:

“It was very difficult to remove the fossil from the sediment in which it was trapped.  Doing so in the traditional way by scraping the sediment could break these bones because they were so fragile.”

Although numerous papers on Saturnalia tupiniquim have been published, little was known about the morphology of the skull.  The three-dimensional images that were created as a result of this analysis provided the researchers with the opportunity to study the head of this dinosaur in detail and the reconstruct the skull of this Late Triassic dinosaur.

A Diagram Showing the Skull of Saturnalia

Picture credit: PLOS One

Studying the Skull of Saturnalia

The skull is disproportionately small when compared to the size of the dinosaur’s body.  It is thought that Saturnalia was carnivorous, eating small prey items  such as lizards, mammals and insects, but the consumption of plants cannot be ruled out.  The reduced skull is a characteristic of the Sauropodomorpha lineage and demonstrated in later sauropods such as Diplodocus and Brachiosaurus.  The specialisation of the skull and neck of Saturnalia has implications for the evolution of these lizard-hipped dinosaurs as later forms became entirely herbivorous.

Skull reduction significantly reduced the biomechanical contraints for the development of long necks, in turn, longer necks permitted access to food resources that were unreachable for other plant-eating dinosaurs.  This would have helped to provide a competitive advantage and might explain why later sauropods grew to such large sizes.  Thus, the idea that skull reduction was first acquired in a likely predatory member of the sauropodomorph lineage (i.e. Saturnalia) implies a scenario where a trait related to one habit (faunivory) was crucial for the evolution of a completely different lifestyle (herbivory) in a subsequently different selection regime.

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New Fossil Study of Jurassic Crocodile Confirms Identity

Numerous genera of Jurassic and Cretaceous marine crocodiles have been described.  However, since many of these genera were erected in the 18th and 19th centuries, sometimes these fossil remains have to be revisited as new discoveries provide additional information.  Take the case of Mystriosaurus laurillardi, a teleosauroid known from fossils found in Germany and in the United Kingdom.  The taxonomy of the teleosauroids has been blighted by the problems associated with  Steneosaurus bollensis.

Specimens have been “lumped” into this species only to be subsequently reassigned.  A new study, published in the journal Acta Palaeontologica Polonica demonstrates that Mystriosaurus is a distinct species.

A Life Reconstruction of Mystriosaurus laurillardi

Picture credit: Julia Beier

Mystriosaurus laurillardi a Marine Predator

M. laurillardi grew to about four metres in length.  The long and narrow jaws and the teeth associated with this marine predator suggest that it fed primarily on fish (piscivore).  It lived 180 million years ago (Toarcian faunal stage of the Early Jurassic).  A fossil skull found in southern Germany in the 1770s had previously been described as Steneosaurus bollensis, a contemporaneous member of the Teleosauridae, but in this new assessment of the cranial material, the researchers led by scientists from the Naturkunde-Museum Bielefeld (Germany) and scientists from Edinburgh University, concluded that the skull represented M. laurillardi.

The research team also announced that another crocodilian skull found in Yorkshire (Mulgrave Shale Member, Whitby Mudstone Formation), should also be assigned to Mystriosaurus laurillardi.

The Holotype Cranial Material of M. laurillardi from southern Germany

Picture credit: Acta Palaeontologica Polonica, Sachs et al.

Sorting Out Steneosaurus brevior

Previously, the crocodilian skull from Yorkshire had been named Steneosaurus brevior, the scientists suggest that this name is now a junior synonym of Mystriosaurus laurillardi.  Intriguingly, a phylogenetic assessment  indicates that Mystriosaurus was closely related to Steneosaurus, but it is probably more closely related to a Chinese teleosauroid (previously known as Peipehsuchus), than any European form.

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