A new Upturn throughout Huge batch Making Triggered Dinosaur Diversification

During the last 20 years approximately, palaeontologists studying the Late Cretaceous fauna of North America can see an amazing number of Ornithischian dinosaurs in strata laid down between 80 million and 70 million years ago. A number of horned dinosaurs such as for example Vagaceratops, Utahceratops and Kosmoceratops in addition to numerous new genera of Hadrosaurs (duck-billed dinosaurs) have already been described from western North America. Most palaeontologists have already been focused on mapping the faunal distribution and studying the myriad of new plant-eating dinosaur species which were found, but numerous scientists are now actually embracing the mystery of why so many several types of dinosaur evolved in this area of the world over the past 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 lies in 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 study team from the University’s Heritage College of Osteopathic Medicine experienced their paper published in the on line scientific journal PloS One (public library of science).  what dinosaur has 500 teeth They state that the rapid changing geology generated populations of animals being isolated that might 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 within the last few decades palaeontologists are becoming increasingly aware of the huge array of several types of plant-eating dinosaur that roamed the thing that was to become the United States and Canada. However, immediately, prior to the Cretaceous mass extinction, there have been only 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 study team attempt to examine the geological record of the thing that was to become the continent of North America, focusing on the United States and Canada. Through the Campanian faunal stage of the Cretaceous, a amount of time in the Earth’s history that roughly pertains to 83 million years back to 74 million years back there clearly was extensive plate tectonic activity that generated mountain ranges being pushed up and the sinking of much of the continental landmass under an inland sea (known as the Western Interior Seaway). At its most extensive, this seaway covered much of North America from Canada to the Gulf of Mexico.

In the later Maastrichtian faunal stage, that lasted from 74 million years back up until the mass extinction event 65 million years back, there clearly was less extensive plate activity. This coincided with a decline in the number of genera of dinosaur known from the fossil record. Palaeontologists have interpreted this as evidence as a fall in the number of dinosaur species surviving in North America towards the end of the Cretaceous – dinosaur genera became less diverse.

Mountain Building Isolating Populations

Geologists have calculated that during the Early Cretaceous there clearly was a substantial number of geological activity in the western United States. A number of processes involving subduction, the movement of ocean crust on to the Earth’s mantle occurred along the thing that was to become the western coast of North America. These immense geological forces caused the western area of the Americas to be lifted up and this generated the synthesis of an enormous mountain range that extended from Alberta (Canada) in a south-western direction to as far south as the southern United States. The region to the east of this newly formed mountain range (the Sevier Mountains), flexed downwards and this coincided with a rise in global sea levels, flooding much 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 by having an amazing number of marine reptile fossils to review – Dolichorhynchops, Elasmosaurs and huge Mosasaurs such as for example Tylosaurus.

The Ohio based research team have focused on the dinosaur fossils which were found in 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 substantial and diverse population of Ornithischian dinosaurs.

The Island of Laramidia

The absolute most western of the hawaiian islands, known as Laramidia consisted of land that has been to create Alberta in the north with the American states of Dakota and Montana in the middle with the land that has been to become Utah forming the southern area of the island. Formations laid down in the north of this island, the famous Dinosaur Provincial Park for instance, have provided palaeontologists with a huge array of horned and duck-billed, Ornithischian dinosaurs. Fossils found in Utah, animals such as the horned dinosaurs Kosmoceratops and Utahceratops from rocks of roughly the exact same age, indicate that several 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 generated the nascent development of the thing that was to become the North American Rockies.

New Species Every One Hundred Thousand Years

The team postulate that a new species of large, Ornithischian dinosaur evolved every few hundred thousand years in the period that the mountain ranges and the Western Interior Seaway isolated populations. These geological processes generated a rapid burst of dinosaur evolution in these cut-off populations, in the exact 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 taken to a finish with the continued rise of the embryonic Rock Mountains which eventually forced the Western Interior Seaway to contract. This opened 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 higher than a million years to evolve.

A Barrier to Migration

The study team warn that their work with the major, herbivorous dinosaur faunas of North America can’t be used as a template to describe the rise and then your decline in dinosaur diversity on an international scale. However, the rapidly changing geology brought on by plate movements would have had an influence within the migration of dinosaurs from the Americas into Asia and into South America. The rise of the Rocky Mountains for instance, would have created a barrier that the dinosaurs could not cross. Only dinosaur species resident north of this barrier would have migrated into Asia and only those species surviving in the southern section of Laramidia would have had a migration route open for them to South America.

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