Some Surge through Mountain peak Generating Took Dinosaur Variation
Over the last twenty years or so, palaeontologists studying the Late Cretaceous fauna of North America have discovered an amazing variety of Ornithischian dinosaurs in strata laid down between 80 million and 70 million years ago. Several horned dinosaurs such as for instance 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 dedicated to mapping the faunal distribution and studying the myriad of new plant-eating dinosaur species that have been found, but numerous scientists are actually turning to the mystery of why so many various kinds of dinosaur evolved in this the main world during the last few million years of the Cretaceous.
Diversity Explanation Is based on the Geology
For starters 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 looks 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 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 state 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 have grown to be increasingly conscious of the huge selection of various kinds of plant-eating dinosaur that roamed that which was to end up being the United States and Canada. However, immediately, ahead of the Cretaceous mass extinction, there were only some 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 that which was to end up being the continent of North America, focusing on the United States and Canada. Throughout 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 clearly 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 while 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 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 drop in the number of dinosaur species residing 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 clearly was an amazing level 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 that which 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 massive mountain range that extended from Alberta (Canada) in a south-western direction to as far south while 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 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 having an amazing variety of marine reptile fossils to study – Dolichorhynchops, Elasmosaurs and huge Mosasaurs such as for instance Tylosaurus.
The Ohio based research team have dedicated to 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
The most western of the hawaiian islands, referred to as Laramidia contained 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 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 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 exactly the 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 was further compounded by later plate tectonic movements that resulted in the nascent development of that which was to end up being the North American Rockies.
New Species Every One Hundred Thousand Years
The team postulate 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 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 a finish with the continued rise of the embryonic Rock Mountains which eventually forced the Western Interior Seaway to contract. This exposed 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 greater than a million years to evolve.
A Barrier to Migration
The investigation team warn that their focus on the major, herbivorous dinosaur faunas of North America cannot be used as a template to describe the rise and then a decline in dinosaur diversity on an international scale. However, the rapidly changing geology caused by plate movements could have had an influence over the migration of dinosaurs from the Americas into Asia and into South America. The rise of the Rocky Mountains for instance, could have created a barrier that the dinosaurs couldn’t cross. Only dinosaur species resident north of the barrier might have migrated into Asia and only those species residing in the southern element of Laramidia could have had a migration route open in their mind to South America.