Knowledge Dinosaurs lived in the northern hemisphere earlier than previously thought
Dinosaurs probably colonized the northern hemisphere much earlier than previously thought. This is indicated by around 230 million-year-old remains of the dinosaur species Ahvaytum bahndooiveche and an as yet undetermined species.
10.01.2025, 11:06
10.01.2025, 11:07
SDA
The fossils are almost as old as the oldest dinosaur finds on southern landmasses (around 233 million years), as reported by a team led by David Lovelace from the University of Wisconsin Geology Museum in Madison in the specialist journal "Zoological Journal of the Linnean Society". "With these fossils, we have the oldest equatorial dinosaur in the world - it is also the oldest dinosaur in North America," explained Lovelace with regard to A. bahndooiveche.
The previous assumption was that the origin of the dinosaurs was deep in the southern hemisphere, the researchers explain. At that time, all of the Earth's land masses formed the supercontinent Pangaea, which began to break apart into a northern continent (Laurasia) and a southern continent (Gondwana) around 200 million years ago. While a number of fossils of early dinosaurs have been found in the area of the former Gondwana, there were no comparably old finds from low latitudes (around the equator) and Laurasia: between the oldest Gondwanan finds and the oldest known dinosaur occurrences in the northern hemisphere (Laurasia), there were about 6 to 10 million years.
Hypothesis begins to falter
The findings, which are around 230 million years old, now call into question the hypothesis of a delayed spread of dinosaurs from Gondwana to high latitudes. It is possible that too few layers of the earlier Laurasia have been studied over time. According to this, the previous hypothesis was based on a sampling bias.
The name Ahvaytum bahndooiveche comes from a Shoshonean language and means "long ago" (Ahvaytum) and "dinosaur" (bahndooiveche). It was selected in collaboration with the indigenous population. The researchers identified the new species on the basis of fossilized bones: a talus bone and part of a femur. Database comparisons revealed that the fossils cannot be assigned to any known dinosaur species.
Many details still unclear
Further analysis revealed that A. bahndooiveche belonged to the Sauropodomorpha, one of the two main groups of lizard pelvic dinosaurs (Saurischia), from which birds later evolved. In addition, the scientists found leg bones of an as yet undetermined animal from the bird lineage archosaur group in the same rock formation, the Popo Agie Formation in Wyoming (USA).
The researchers cannot say anything about the diet of A. bahndooiveche because no skull bones are available. It is assumed that A. bahndooiveche, like its closest relatives, was an omnivore. According to the researchers, the appearance of A. bahndooiveche could be linked to the Carnian rain episode, also known as the Raibl event. Between 232 and 234 million years ago (during the Carnian period), it rained a lot, which greatly changed the ecosystems on land and in the sea. Recent studies have linked the evolution of dinosaurs from preforms to this event.
