New research has revealed that even as a teenager, the Tyrannosaurus-Rex showed signs of maturing into a formidable predator. Meanwhile, jaws discovered in Australia reveals herbivorous dinosaurs were far more diverse than previously b
In a study published last week in the peer-reviewed journal Peerj–the Journal of Life and Environmental Sciences, University of Wisconsin Oshkosh scientists reported evidence that a juvenile T. rex fed on a large plant-eating dinosaur, even though it lacked the bone-crushing abilities it would develop as an adult.
While studying fossils from an Edmontosaurus–a plant-eating Hadrosaurid or duck-billed dinosaur, UWO vertebrate palaeontologist Joseph Peterson noticed three large, V-shaped, bite marks on a tail bone and questioned what animal was responsible for them.
Peterson knew that T. rex–a member of the meat-eating dinosaur suborder known as Theropoda–was a likely culprit.
Peterson explains: “We suspected that T. rex was responsible for the bite marks because, in the upper Cretaceous rock formation, where the hadrosaur was discovered, there are only a few carnivorous dinosaurs and other reptiles in the fossil record.
“Crocodile fossils are found there, but such a crocodile would have left tooth marks that are round rather than the elliptical punctures we found on the vertebra.”
Peterson realised that teeth belonging to small Velociraptor-like dinosaurs would have been too small, and, conversely, adult T.Rex teeth would have been too large. “That’s when we started considering a juvenile Tyrannosaur,” he reasons.
To test the hypothesis, Peterson and geology student Karsen Daus, of Suamico, coated the fossil with silicon-rubber to make a silicone peel of the puncture marks.
They found that the dimensions of the “teeth” better matched a late-stage juvenile T. rex (11 to 12 years) than an adult (approximately 30 years).
Pearson adds: “Although this T. rex was young, it really packed a punch.
“This is significant to palaeontology because it demonstrates how T. rex may have developed changes in diet and feeding abilities while growing.”
The research forms part of a larger, ongoing research initiative by many palaeontologists to better understand how T. rex grew and functioned as a living creature over 65 million years ago.
Peterson explains that most theropod feeding traces and bite marks are attributed to adults, so juvenile tooth marks have rarely been reported in the literature.
That includes another discovery, recently reported in a separate piece of research–a wallaby-sized dinosaur found in the ancient Australian-Antartic rift valley.
Upper jaw of a new-dinosaur, gives insight into the diversity of herbivorous dinosaurs
A new, wallaby-sized herbivorous dinosaur has been identified from five fossilized upper jaws in 125 million year old rocks from the Cretaceous period of Victoria, southeastern Australia.
The new dinosaur–named Galleonosaurus
Dr Matthew Herne, a Postdoctoral Fellow at the University of New England, NSW and lead author of the new study, says: “The jaws of Galleonosaurus
The paper–published in Journal of Paleontology–reveals that Galleonosaurus was a small-bodied herbivorous dinosaur within the large family called ornithopods. Herne explains: “These small dinosaurs would have been agile runners on their powerful hind legs.”
The Galleonosaurus finding confirms that on a global scale, the diversity of these small-bodied dinosaurs had been unusually high in the ancient rift valley that once extended between the spreading continents of Australia and Antarctica. It also indicates that small ornithopods appear to have thrived on the vast, forested floodplain within the ancient rift valley.
At the time of Galleonosaurus, sediments were shed from a four thousand km long massif of large, actively erupting volcanoes that once existed along the eastern margin of the Australian continent.
Some of these sediments were carried westward by large rivers into the Australian-Antarctic rift valley where they formed deep sedimentary basins.
However, as these sediments washed down the rivers of the rift valley the bones of dinosaurs, such as Galleonosaurus and other vertebrates, along with the logs of fallen trees, became mixed in. Herne says: “This land has now vanished, but as ‘time-travellers’ we get snapshots of this remarkable world via the rocks and fossils exposed along the coast of Victoria.”
The new article shows that Galleonosaurus
Herne continues: “The jaws of Galleonosaurusand the partial skeleton of Diluvicursor were similarly buried in volcanic sediments on the floor of deep powerful rivers
The name Galleonosaurus dorisae refers to the shape of the upper jaw, resembling the upturned hull of a sailing ship called a galleon, and also honours the work of Dr Doris Seegets-Villiers, who produced her PhD thesis on the palaeontology of the locality where the fossils were discovered.
The jaws of Galleonosaurus were discovered by volunteers of the Dinosaur Dreaming project during excavations near the town of Inverloch. The most complete jaw and the key specimen carrying the name Galleonosaurus dorisae was discovered in 2008 by the seasoned fossil hunter Gerrit (‘Gerry’) Kool, from the nearby town of Wonthaggi. Gerry and his wife Lesley have been instrumental in organizing the Dinosaur Dreaming excavations along the Victorian coast for 25 years.
Prior to discovery of Galleonosaurus dorisae, the only other ornithopod known from the Gippsland region was Qantassaurus intrepidus, named in 1999. However, Qantassaurus had a shorter more robust snout than that of Galleonosaurus, explained Dr Herne, who added, “we consider that these two, similarly-sized dinosaurs fed on different plant types, which would have allowed them to coexist.”
The new study reveals that the ornithopods from Victoria are closely related to those from Patagonia in Argentina. Herne adds: “We are steadily building a picture of terrestrial dinosaur interchange between the shifting Gondwanan continents of Australia, South America and Antarctica during the Cretaceous period.”
Exciting times for dinosaur research
These are exciting times for dinosaur research, explains Dr Herne: “Using advanced techniques, such as 3D micro-CT scanning and printing, new anatomical information is being revealed on dinosaurs such as Galleonosaurus
“These techniques are helping us to delve deeper into the mysterious world of dinosaur ecology–what they ate, how they moved and how they coexisted–and their evolutionary relationships with dinosaurs from other continents.”
Palaeontologist Joseph Peterson–who discovered the teenage T.Rex– adds: “We are learning more now than we ever thought we would know about dinosaurs.”
“We really are in the ‘Golden Age’ of palaeontology. “