Your Lift around Mountain / hill Establishing Ended in Dinosaur Diversification

Throughout the last 20 years or so, palaeontologists studying the Late Cretaceous fauna of North America have discovered an incredible selection 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 along with 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 that have been found, but a number of scientists are actually looking at the mystery of why so many several 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 as to dinosaur diversity is based on the geology. The rise of the Rocky Mountain range and the appearance and then disappearance of a massive, inland seaway that split North America into a series of islands, could have been the catalysts for an explosion in megafauna diversity. The investigation 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 claim that the rapid changing geology generated populations of animals being isolated which may explain the patterns of evolution, migration and rapid dinosaur diversification.

Terry Gates, the lead author of the paper and a post-doctoral student at the University commented that within the last few decades palaeontologists have grown to be increasingly conscious of the huge selection of several types of plant-eating dinosaur that roamed what was to end up being the United States and Canada. However, immediately, prior to the Cretaceous mass extinction, there were just 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 investigation team set out to examine the geological record of what was to end up being 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 pertains to 83 million years back to 74 million years back there is extensive plate tectonic activity that generated mountain ranges being pushed up and the sinking of a lot of the continental landmass under an inland sea (known whilst 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 until the mass extinction event 65 million years back, there is 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 drop in the number 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 through the Early Cretaceous there is an amazing level of geological activity in the western United States. A number of processes involving subduction, the movement of ocean crust down into the Earth’s mantle occurred along what was to end up being the western coast of North America. These immense geological forces caused the western the main Americas to be lifted up and this generated the formation of a massive mountain range that extended from Alberta (Canada) in a south-western direction to as far south whilst 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 behind in places as far apart as Alberta and Kansas have provided palaeontologists with an amazing selection of marine reptile fossils to study – Dolichorhynchops, Elasmosaurs and huge Mosasaurs such as for example Tylosaurus.

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

The Island of Laramidia

Probably the most western of the hawaiian islands, referred to as Laramidia consisted of land that has been to form 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 the main island. Formations laid down in the north with this island, the famous Dinosaur Provincial Park like, have provided palaeontologists with a massive selection 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 was further compounded by later plate tectonic movements that generated the nascent development of what was to end up being 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 during the time 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 conclusion with the continued rise of the embryonic Rock Mountains which eventually forced the Western Interior Seaway to contract. This opened a sizable, 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 investigation team warn that their work on the major, herbivorous dinosaur faunas of North America can’t be used as a template to spell out the rise and then a decline in dinosaur diversity on a global scale. However, the rapidly changing geology caused by plate movements could have had an influence on the migration of dinosaurs from the Americas into Asia and into South America. The rise of the Rocky Mountains like, could have created a barrier that the dinosaurs couldn’t cross. Only dinosaur species resident north with this barrier may have migrated into Asia and only those species living in the southern element of Laramidia could have had a migration route open in their mind to South America.

Leave a Reply

Your email address will not be published. Required fields are marked *