September 24, 2023

A good Surge during Mntain Setting up Produced Dinosaur Diversity

Over the last two decades roughly, palaeontologists studying the Late Cretaceous fauna of North America have found a fantastic selection of Ornithischian dinosaurs in strata laid down between 80 million and 70 million years ago. Several horned dinosaurs such as 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 centered on mapping the faunal distribution and studying the myriad of new plant-eating dinosaur species that have been found, but numerous scientists are now turning to the mystery of why so many various kinds of dinosaur evolved in this area of the world over the past few million years of the Cretaceous.

Diversity Explanation Is based on the Geology

For just one team of researchers based at Ohio University, the explanation regarding dinosaur diversity lies in the geology. The rise of the Rocky Mountain range and the look and then disappearance of a massive, inland seaway that split North America into a series of islands, might 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 online scientific journal PloS One (public library of science).  what dinosaur has 500 teeth They state that the rapid changing geology led to populations of animals being isolated which can 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 over the past few decades palaeontologists are becoming increasingly conscious of the huge range of various kinds of plant-eating dinosaur that roamed the thing that was to end up being the United States and Canada. However, immediately, prior to the Cretaceous mass extinction, there were only a few dominant dinosaur species across the complete continent. This phenonmenon has yet to be fully explained.

Examining the Geological Record of North America

The study team set out to examine the geological record of the thing that was to end up being the continent of North America, concentrating on the United States and Canada. During the Campanian faunal stage of the Cretaceous, a time in the Earth’s history that roughly pertains to 83 million years back to 74 million years back there was extensive plate tectonic activity that led to 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 back up before the mass extinction event 65 million years back, there was less extensive plate activity. This coincided with a decline in the amount of genera of dinosaur known from the fossil record. Palaeontologists have interpreted this as evidence as a drop in the amount of dinosaur species living in North America towards the very end of the Cretaceous – dinosaur genera became less diverse.

Mountain Building Isolating Populations

Geologists have calculated that throughout the Early Cretaceous there was an amazing quantity of geological activity in the western United States. Several processes involving subduction, the movement of ocean crust down into the Earth’s mantle occurred along the thing that was to end up being the western coast of North America. These immense geological forces caused the western area of the Americas to be lifted up and this led to the synthesis of a massive 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 with this 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 left out in places as far apart as Alberta and Kansas have provided palaeontologists with an amazing selection of marine reptile fossils to examine – Dolichorhynchops, Elasmosaurs and huge Mosasaurs such as Tylosaurus.

The Ohio based research team have centered on the dinosaur fossils that have been present 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 an amazing and diverse population of Ornithischian dinosaurs.

The Island of Laramidia

The absolute most western of the islands, referred to as Laramidia consisted of land that was to create Alberta in the north with the American states of Dakota and Montana in the middle with the land that was to become Utah forming the southern area of the island. Formations laid down in the north with this island, the famous Dinosaur Provincial Park as an example, have provided palaeontologists with a massive range of horned and duck-billed, Ornithischian dinosaurs. Fossils present in Utah, animals like the horned dinosaurs Kosmoceratops and Utahceratops from rocks of roughly the exact same age, indicate that various kinds 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 led to the nascent development of the thing that was to end up being 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 at that time that the mountain ranges and the Western Interior Seaway isolated populations. These geological processes led to 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 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 big, 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 study team warn that their work on the major, herbivorous dinosaur faunas of North America can not be used as a template to spell out the rise and then the decline in dinosaur diversity on an international scale. However, the rapidly changing geology due to plate movements might have had an influence within the migration of dinosaurs from the Americas into Asia and into South America. The rise of the Rocky Mountains as an example, might have created a barrier that the dinosaurs couldn’t cross. Only dinosaur species resident north with this barrier might 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.