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Discover the many plant-eating dinosaurs who roamed Victoria 110 millions years ago

Australia was further south than it is today during the Early Cretaceous period 110 million to 107 millions years ago. However, fossils found at several locations on Victoria’s Otway Coast show that dinosaurs were quite common in this region.

Ornithopods were the most common — small plant-eaters with large beaks and a lot of teeth. It was not clear until recently how many species could coexist at once.

Five ornithopod species from the Cretaceous of Victoria have been identified so far. Three species are from the Otway Coast, Diluvicursor Pickeringi, Atlascopcosaurus loadsi and Leaellynasaura micagraphica. Two from the Bass Coast are Qantassaurus Intrepidus and Galleonosaurus dorsae.

The rocks and fossils found on the Bass Coast are approximately 15 to 20 million years younger than the ones on the Otway Coast. Australia’s climate changed dramatically during this time.

Although there is substantial evidence that South Australia experienced glaciation about 125m years ago (110 million years ago), warm-weather-loving crocodiles were still roaming freely in Victoria 110 million years earlier.

It was therefore assumed that the Bass Coast’s Qantassaurus/Galleonosaurus, which lived in colder environments, probably never met the Otway Coast’s Leaellynasaura and Atlascopcosaurus. Is that true?

Eric The Red West

We are now better equipped to answer the question thanks to Ruairidh Duncan’s research. Ruairidh researched fossils at Eric the Red West (ETRW) for his Honours Project.

ETRW discovered a partial ornithopod skull in 2005. The 2018 name of this partial ornithopod skeleton was Diluvicursor Pickeringi. It consisted only of a tail and a partial shin.

Dinosaur Dreaming, a volunteer group, made several more digs at the site to find even more ornithopod bone fragments. We didn’t know if these jawbones belonged to new species until Ruairidh examined them.

Technology can help you a little

Most of the jawbones of ornithopod from ETRW had been broken in half by their discovery. This is normal, since the bones are more soft than the rocks in which they are enclosed.

Depending on how they were broken down, rock might have been removed from one jawbone’s tongue side and rock from its cheek side.

This allowed the jaws to connect nicely but Ruairidh could not see most of his specimens from the cheek or tongue side. Technology is a great help.

Alistair Evans, Monash University’s micro-CT scanner, scanned several ornithopod samples retrieved from ETRW. Micro-CT scanners produce a series 2D cross-sectional images of a 3D object, much like medical CT scanners. However, they are smaller in scale.

Ruairidh was able to digitally remove the rocks from his specimens, which were each less than ten cm long, and then reconstruct each one in 3D.

An unexpected Galleonosaurus

Ruairidh analyzed the ornithopod jawbones taken from the ETRW site, and compared them to other Victorian ornithopods. Three of the five ornithopods from Victoria had been identified and described using the upper jawbones. This allowed for a direct comparison.

He discovered that one of the upper jawbones was attributable both to Atlascopcosaurus, which is the most complete specimen of this species, and Leaellynasaura, which is the first adult specimen of this species.

The bones that we thought were the last two would be from a Diluvicursor had been our expectation. We were surprised to find they were very similar with Galleonosaurus, a species that was previously only known from the Bass Coast. The rocks were approximately 15-20 million years older then those at ETRW.

We had evidence that an ornithopod was alive and well for at least 15,000,000 years.

Possible explanations

An ornithopod that is so similar to Galleonosaurus (ETRW) suggests that there was very little in the way of tooth and jaw anatomy changes, and presumably diet, in these dinosaurs over almost 20 million years despite significant climatic change.

This could mean that their favorite plants were not in great abundance during this period. In which case, they might have felt little pressure to alter the structure or shape of their jaws and teeth.

It is impossible to compare jawbones from ETRW and the Diluvicursor pickingi specimen, as there were no jawbones found with it.

Perhaps the fact that Diluvicursor does not have a jawbone type unique to it could mean that this species is the same species as other jawbone-representing species. It’s likely to be Atlascopcosaurus, or a Galleonosaurus-like animal; Leaellynasaura has been tentatively assigned a different tail and foot.

This will only be possible if an ornithopod skull matches that of Diluvicursor and a skull similar to the jaws of Atlascopcosaurus, or Galleonosaurus, is found.

We might have to wait a while, considering that only four ornithopod bones were found in 40 years of digging for dinosaurs at Victoria.

Ruairidh’s research reveals that three distinct ornithopod species lived happily in southeast Australia, at the Antarctic Circle, about 110 million to107 million years ago. This was when the Earth was much warmer than it is now.

The ETRW site has provided abundant fossil evidence to date. This includes plants (mostly conifers and early flowering plants), bonefish, lungfish and huge-clawed megaraptorids, Australia’s only toothless, long-necked, elaphrosaurine, and even ancient mammals.

Only one ornithopod bone has been found: the Diluvicursor. We never know what we might discover next.

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