Mike Simms with the theropod tibia (left) and the Scelidosaurus femur (right). (University of Portsmouth) ENVIRONMENT Ireland's Only 2 Dinosaur Bones Have Just Been Confirmed For The First Time JACINTA BOWLER 4 DECEMBER 2020
Once upon a time, dinosaurs were a pretty ubiquitous lot. Even 66 million years after the last dinosaurs went extinct, the fossils they left behind have been found on every continent on Earth.
But bones don't just fossilise anywhere – they're most often found in sedimentary rocks. One particular area where there's a distinct lack of dinosaur remains is Ireland.
Sedimentary rocks from the time of the dinosaurs in Ireland have been moved about, buried, or undergone erosion. These Mesozoic Era rocks were torn from the supercontinent of Pangea and shifted north before being buried under basalt from intense volcanic activity after the time of the dinosaurs, so that they now make up only about 1 percent of Ireland's rocks.
"Most of Ireland's rocks are the wrong age for dinosaurs, either too old or too young, making it nearly impossible to confirm dinosaurs existed on these shores," explains National Museums Northern Ireland curator and palaeontologist Mike Simms.
But it's not entirely void of dinosaur fossils. The late Roger Byrne, a school teacher and fossil collector, has an incredible legacy – he found not one but both of Ireland's only dinosaur fossils.
And those fossils – found in the 1980s and donated to the Ulster Museum among several other fossils – have just been described for the first time in a scientific paper.
"Finding an Irish dinosaur might seem a hopeless task but, nonetheless, several potential candidates have been identified and are described for the first time here," the researchers write in their new paper.
"Several specimens from Northern Ireland have been suspected, or suggested, as dinosaur bones but just two can be definitely assigned to this group on the basis of their bone histology, surface texture and morphology."
The paper looks into four specimens that could have been dinosaur fossils, three that Byrne found on the beach near the Gobbins on the Eastern coast of Northern Ireland between 1980 and 2000, and one that's been in the museum collection since 1920, but its history is a little hazy.
That 1920s specimen is a fossil, but not of a dinosaur. Instead, the team believes it's likely a marine reptile like an ichthyosaur.
Byrne's 2000 discovery, on the other hand, was a weird pentagonal shape with a bone-like texture and seemed to be unlike any dinosaur discovered so far.
"It was only through examination by a fresh pair of eyes in 2019 that the mystery was finally solved," the researchers write.
"It is not a bone at all but merely a small pentagonal piece of basalt!"
And that left two of Byrne's fossil finds – one femur fragment of a four-legged herbivore called Scelidosaurus, and one tibia fragment of a two-legged carnivore part of the neotheropod clade.
"Analysing the shape and internal structure of the bones, we realised that they belonged to two very different animals," says the University of Portsmouth palaeontologist Robert Smyth.
"One is very dense and robust, typical of an armoured plant-eater. The other is slender, with thin bone walls and characteristics found only in fast-moving two-legged predatory dinosaurs called theropods."
Of course, there's still the question of how they got there in the first place, especially with so little 'correct' rock. Ireland was also underwater for a significant chunk of the age of the dinosaurs, so there's even less land for the creature's bones to eventually fossilise in.
"The two dinosaur fossils that Roger Byrne found were perhaps swept out to sea, alive or dead, sinking to the Jurassic seabed where they were buried and fossilised," says Simms.
The rocks from the age of dinosaurs found in Ireland are mostly limestone, chalks, and mudstones, but these were deposited under the sea. The thing about the Gobbins beach though is that there's a large amount of basalt and limestone on the shore.
If the occasional land dinosaur washed out to sea, it could have been fossilised in these undersea rocks, and then eventually washed back onto the shore hundreds of millions of years later.
"Despite being fragmentary, these fossils provide valuable insight on a very important period in dinosaur evolution, about 200 million years ago. It's at this time that dinosaurs really start to dominate the world's terrestrial ecosystems," says Smyth.
The research has been published in the Proceedings of the Geologists' Association.