Any Increase inside Pile Constructing Generated Dinosaur Diversity
During the last 20 years roughly, 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 Vagaceratops, Utahceratops and Kosmoceratops along with a number of new genera of Hadrosaurs (duck-billed dinosaurs) have now been described from western North America. Most palaeontologists have now been dedicated to mapping the faunal distribution and studying the myriad of new plant-eating dinosaur species which were found, but a number of scientists are now actually embracing the mystery of why so many several types of dinosaur evolved in this the main world over the past few million years of the Cretaceous.
Diversity Explanation Is based on 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 look and then disappearance of an enormous, inland seaway that split North America into some islands, might have been the catalysts for an explosion in megafauna diversity. The investigation 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 suggest that the rapid changing geology resulted in 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 in the last few decades palaeontologists are becoming increasingly aware of the huge range of several types of plant-eating dinosaur that roamed the thing that was to end up being the United States and Canada. However, immediately, before the Cretaceous mass extinction, there have been only a few dominant dinosaur species across the whole 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 the thing that was to end up being the continent of North America, focusing on the United States and Canada. During the Campanian faunal stage of the Cretaceous, a amount of time in the Earth’s history that roughly pertains 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 much of the continental landmass under an inland sea (known whilst 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 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 fall in how many 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 during the Early Cretaceous there was an amazing amount 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 the thing that 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 resulted in the synthesis of a huge 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 much of the continent and splitting what land remained above sea level into some 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 with an amazing number of marine reptile fossils to study – Dolichorhynchops, Elasmosaurs and huge Mosasaurs such as Tylosaurus.
The Ohio based research team have dedicated to 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 an amazing and diverse population of Ornithischian dinosaurs.
The Island of Laramidia
Probably the most western of the islands, referred to as Laramidia contains land that has been to create Alberta in the north with the American states of Dakota and Montana in the centre 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 as an example, have provided palaeontologists with an enormous range of horned and duck-billed, Ornithischian dinosaurs. Fossils within Utah, animals like the horned dinosaurs Kosmoceratops and Utahceratops from rocks of roughly exactly the 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 resulted in 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 the 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 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 brought to an end 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 more than a million years to evolve.
A Barrier to Migration
The investigation 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 the decline in dinosaur diversity on an international scale. However, the rapidly changing geology brought on by 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 could not cross. Only dinosaur species resident north with this barrier would have migrated into Asia and only those species living in the southern part of Laramidia might have had a migration route open to them to South America.