Fossilised dinosaur footprints dating from the Late Triassic that were once thought to represent a large, predatory dinosaur have been re-examined and are now thought to have been made by a mainly vegetarian sauropodomorph. A series of fossilised footprints preserved on the ceiling of a gallery in a coal mine close to the suburb of Dinmore (Queensland, Australia), had been assigned to the ichnogenus Eubrontes. The three-toed tracks, discovered in 1964, were thought to represent a track made by a large theropod dinosaur. They were regarded as the earliest known evidence for the presence of big meat-eating dinosaurs, however, the tracks have been reassessed and are now thought to represent a basal sauropodomorph.

Walking on the Ceiling?

University of Queensland palaeontologist, Dr Anthony Romilio, lead author of the scientific paper published in the journal “Historical Biology”, commented:

“It must have been quite a sight for the first miners in the 1960s to see big bird-like footprints jutting down from the ceiling”.

Around 220 million years ago, dinosaurs walked across water-sodden layers of plant debris and these tracks were later filled in by fine silt and sand. Over millions of years the plant material turned into coal and this was removed by the miners, leaving a ceiling of siltstone and sandstone in the excavated galleries complete with the preserved natural casts of the dinosaur tracks.

The First and Only Evidence of an Australian Basal Sauropodomorph

The coalmine has been closed down, but the original photographs, drawings and plaster casts made in the 1960’s were available for study and under close scrutiny, the research team recognised that the tracks shared characteristics with the sauropodomorph ichnogenus Evazoum.

The Sauropodomorpha is a sister clade to the Theropoda within the lizard-hipped dinosaurs (Saurischia), the first sauropodomorphs evolved around 230 million years ago and these, large-bodied, long-necked herbivores were the ancestors of the huge sauropods that were to dominate many terrestrial ecosystems in the Jurassic. If the research team’s interpretation of the ceiling tracks is correct, these prints provide the first and only evidence of basal sauropodomorph dinosaurs from Australia.

The coalmine ceiling tracks suggest that the sauropodomorph that made them was around six metres long.

To read an article about other Australian tracks preserved on the ceiling of a cave: Mystery of Dinosaur Prints on Cave Ceiling Solved.

Everything Dinosaur acknowledges the assistance of a media release from the University of Queensland in the compilation of this article.

The scientific paper: “Saurischian dinosaur tracks from the Upper Triassic of southern Queensland: possible evidence for Australia’s earliest sauropodomorph trackmaker” by Anthony Romilio, Hendrik Klein, Andréas Jannel and Steven W. Salisbury published in Historical Biology.

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Paul Barrett of the Department of Earth Sciences at the University of Oregon, has put the prehistoric “cats” amongst the prehistoric pigeons with the publishing of a new scientific paper that reassesses the evolution of the “false-sabre tooths”, the Nimravidae. Previous studies had focused on the remarkable, over-sized canines of these placental predators. The paper, published in the journal “Scientific Research”, examined non-sabre-tooth anatomical features and as a result, a different hypothesis on the evolution of nimravids has been proposed.

An Over Emphasis on the Teeth and Skulls

Previous studies attempting to map the evolutionary history of the Nimravidae from their origins in the Middle Eocene Epoch to their extinction in the Late Miocene, had focused on examining the shape of the skull and the dentition (teeth). This over reliance on anatomical characters associated with the teeth and the necessary cranial adaptations to wield the enlarged canines led to palaeontologists thinking that these predators evolved in a relatively narrow, restricted way – that there was a gradual evolution of more specialised sabre-tooth features.

This new research based on sophisticated Bayesian analysis looking at a much broader suite of characters and traits suggests that the Nimravidae split, relatively early on in their evolution, into two distinct clusters. One branch (Hopliphoninae) became sabre-toothed hunters, whilst the second branch (Nimravinae) evolved traits reminiscent of extant big cats.

Eusmilus adelos

In addition to the reassessment of the evolutionary direction of the nimravids, PhD student Paul also examined the fossilised remains of a lion-sized specimen found in Wyoming (White River Formation). This has led to the erection of a new species Eusmilus adelos. Regarded as the biggest member of the Hopliphoninae described to date, it is suggested that a large predator such as E. adelos specialised in hunting prey bigger than itself. Eusmilus adelos may have tackled tapirs, rhinoceratids and large anthracotheriids (an extinct family of hooved, even-toed ungulates distantly related to hippos).

Studying False Sabre-tooths

Coeval hoplophonines were smaller and the author suggests these predators specialised in tackling much smaller prey. This niche partitioning (avoiding of competition by focusing on different resources), would have reflected what is seen on the plains of Africa today amongst extant felids. Large predators such as lions specialising in prey bigger than themselves, whilst smaller felids such as the caracal (Caracal caracal) and the leopard (Panthera pardus) tend to hunt prey smaller than themselves.

To read a related article from Everything Dinosaur that focuses on a study into the evolution of sabre-toothed predators across deep geological time, that suggests that these superficially similar animals evolved very different hunting strategies: Sabre-toothed Predators Evolved Different Hunting Styles.

The scientific paper: “The largest hoplophonine and a complex new hypothesis of nimravid evolution” by Paul Zachary Barrett published in Scientific Reports.