• May 30, 2022

An important Rise on Mtn Construction Brought about Dinosaur Variation

During the last 20 years or so, palaeontologists studying the Late Cretaceous fauna of North America can see an incredible selection of Ornithischian dinosaurs in strata laid down between 80 million and 70 million years ago. Numerous horned dinosaurs such as for instance Vagaceratops, Utahceratops and Kosmoceratops as well as a number of new genera of Hadrosaurs (duck-billed dinosaurs) have been described from western North America. Most palaeontologists have been focused on mapping the faunal distribution and studying the myriad of new plant-eating dinosaur species which were found, but a number of scientists are now turning to the mystery of why so many different types of dinosaur evolved in this the main world during the last few million years of the Cretaceous.

Diversity Explanation Lies in the Geology

For one team of researchers based at Ohio University, the explanation concerning dinosaur diversity is based on the geology. The rise of the Rocky Mountain range and the appearance and then disappearance of a huge, inland seaway that split North America into a series of islands, could have been the catalysts for an explosion in megafauna diversity. The research team from the University’s Heritage College of Osteopathic Medicine have experienced their paper published in the online scientific journal PloS One (public library of science).  what dinosaur has 500 teeth They claim that the rapid changing geology resulted in populations of animals being isolated which may explain the patterns of evolution, migration and rapid dinosaur diversification.

Terry Gates, the lead composer of the paper and a post-doctoral student at the University commented that in the last few decades palaeontologists are becoming increasingly alert to the huge range of different types of plant-eating dinosaur that roamed what was to become the United States and Canada. However, immediately, ahead of the Cretaceous mass extinction, there were just a few dominant dinosaur species across the entire continent. This phenonmenon has yet to be fully explained.

Examining the Geological Record of North America

The research team attempted to examine the geological record of what was to become the continent of North America, concentrating on the United States and Canada. Throughout the Campanian faunal stage of the Cretaceous, a time in the Earth’s history that roughly relates to 83 million years ago to 74 million years ago there was extensive plate tectonic activity that resulted in mountain ranges being pushed up and the sinking of a lot of the continental landmass under an inland sea (known since the Western Interior Seaway). At its most extensive, this seaway covered a lot of North America from Canada to the Gulf of Mexico.

In the later Maastrichtian faunal stage, that lasted from 74 million years ago up before mass extinction event 65 million years ago, there was less extensive plate activity. This coincided with a decline in how many genera of dinosaur known from the fossil record. Palaeontologists have interpreted this as evidence as a drop in how many dinosaur species living in North America towards ab muscles end of the Cretaceous – dinosaur genera became less diverse.

Mountain Building Isolating Populations

Geologists have calculated that throughout the Early Cretaceous there was a considerable amount of geological activity in the western United States. Numerous processes involving subduction, the movement of ocean crust into the Earth’s mantle occurred along what was to become the western coast of North America. These immense geological forces caused the western the main Americas to be lifted up and this resulted in the formation of a huge mountain range that extended from Alberta (Canada) in a south-western direction to as far south since the southern United States. The region to the east of the newly formed mountain range (the Sevier Mountains), flexed downwards and this coincided with a rise in global sea levels, flooding a lot of the continent and splitting what land remained above sea level into a series of large islands. This sea (Western Interior Seaway), teemed with life and the marine deposits put aside in places as far apart as Alberta and Kansas have provided palaeontologists having an amazing selection of marine reptile fossils to study – Dolichorhynchops, Elasmosaurs and huge Mosasaurs such as for instance Tylosaurus.

The Ohio based research team have focused on the dinosaur fossils which were within association with the islands. At its most extensive, the Western Interior Seaway split the North American land mass into three large islands. These islands each had a considerable and diverse population of Ornithischian dinosaurs.

The Island of Laramidia

The absolute most western of the hawaiian islands, called Laramidia consisted of land that was to make Alberta in the north with the American states of Dakota and Montana at the center with the land that was to become Utah forming the southern the main island. Formations laid down in the north of the island, the famous Dinosaur Provincial Park for instance, have provided palaeontologists with a huge range of horned and duck-billed, Ornithischian dinosaurs. Fossils within Utah, animals such as the horned dinosaurs Kosmoceratops and Utahceratops from rocks of roughly exactly the same age, indicate that different types of plant-eating dinosaur evolved in the south. The Ohio University scientists have postulated that mountain building and the rising sea levels caused the available habitat for dinosaurs to shrink on Laramidia. Populations became isolated and this is further compounded by later plate tectonic movements that resulted in the nascent development of what was to become the North American Rockies.

New Species Every One Hundred Thousand Years

The team postulate that the new species of large, Ornithischian dinosaur evolved every few hundred thousand years at that time that the mountain ranges and the Western Interior Seaway isolated populations. These geological processes resulted in a rapid burst of dinosaur evolution in these cut-off populations, in exactly the same way that the isolated populations of animals in the Galapagos archipelago rapidly diversified into new species.

However, this extensive speciation of mega-herbivores was delivered to a conclusion with the continued rise of the embryonic Rock Mountains which eventually forced the Western Interior Seaway to contract. This exposed a large, open territory for the Ornithischian dinosaurs to exploit. This reduced the turnover in species with new species evolving at a much slower rate. New species taking greater than a million years to evolve.

A Barrier to Migration

The research team warn that their work with the major, herbivorous dinosaur faunas of North America can not be used as a template to describe the rise and then a decline in dinosaur diversity on a global scale. However, the rapidly changing geology due to plate movements might have had an influence on the migration of dinosaurs from the Americas into Asia and into South America. The rise of the Rocky Mountains for instance, might have created a barrier that the dinosaurs could not cross. Only dinosaur species resident north of the barrier may have migrated into Asia and only those species living in the southern part of Laramidia might have had a migration route open for them to South America.

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