When Crocodiles Swam The Oceans

it is common knowledge that crocodiles have changed very little for over a hundred million years and while in most cases this is definitely true there are some notable periods of history where a certain crocodile lineage broke off and went in its own way drastically changing from the classic crocodile formula 190 million years ago in the jurassic a group of ancient crocodiles known as the thalatosokians left their semi-aquatic and freshwater habitats for the ocean and because of this some of them took a similar evolutionary pathway to other marine reptiles or marine mammals with their bodies changing to be more fish-like because crocodiles are good swimmers and many species can spend fairly long periods of time in the sea they are always at a tipping point of becoming marine animals if the selective pressures are just right this is known because there are many marine forms of crocodile known from different points throughout history but none were as well adapted for the ocean life as the thalatosokians in the early jurassic period global temperatures were higher than today warming the oceans and making them much more inviting to cold-blooded adventurers and because of this a lineage of semi-aquatic crocodiles migrated into the oceans in the jurassic which would become the thalatosokians at first these crocodiles wouldn't have been all too unfamiliar to us today as crocodiles there is a family of thalatosukians called the teleosaurids that are the most primitive members of the group showing a transition into the more aquatic forms the teleosaurids were heavily armored and had normal tails like modern crocodiles but their feet had began to become a little bit more paddle-like and may have even been webbed plus they had a very streamlined body and narrow snout that could cut through the water one teliosaurid was called peligosaurus that was found with a jurassic era fish in its stomach and due to their long narrow snouts it is likely that many teleosauris ate fish as well peligosaurus fossils have been found from england to switzerland when europe was a set of islands showing they must have been strong swimmers swimming from island to island but teleosaurus were not confined to europe they were very successful with many species being found almost all over the world and some of them even grow to very large sizes the teleosaurid called machimosaurus had species that could grow to over 9 meters long making it one of the largest crocodiles known to have ever lived there are fossilized turtle remains found in germany and switzerland showing bite marks that match the teeth of machimosaurus including one that actually has an embedded matrimosaurus tooth in its shell and their skull and teeth were the correct shape for crushing hard prey this means these giant marine crocodiles were likely specialist turtle trompers however there are also bite marks on a femur of an early sauropod known as setius oriskus that matched these crocs as well but it can't be known if the sauropod was actively hunted or just scavenged the teleosaurids were much more adapted to marine ecosystems than any living crocodile but the lineage of thalatosukins would branch off and become significantly more adapted to the water and even a fish-like migrating further out into the ocean called the metria rinkids their limbs were flat and paddle-like they had lost their thick armor to become more streamlined and flexible and they had even developed a shark-like tail fluke to help propel them through the water it is also known that they had highly developed salt-excreting glands on their skull due to numerous well-preserved fossils of one of the smallest members of the group called metriorinkus this would have allowed them to drink seawater so they could stay out at sea indefinitely this is something that saltwater crocodiles are unable to do and is one of the big barriers that stops them from spending longer out at sea in 2018 a marine crocodile was discovered in hungary dating back to about 180 million years ago called magiarasukus it was heavily armored with claws and had a streamlined body and long thin snout like the teleosaurus but it had a tail fluke like a metreorinkid so this creature bridged the gap between these two families and shows how they developed into their more aquatic forms the metria rinkers lived in a marine environment that couldn't have been more different to today's oceans as the jurassic seas would have already been populated by other marine reptile predators like the plesiosaurs and the ichthyosaurs but despite all of the large predators in the sea at this time these crocs did very well spreading around the world with their fossils being found all around europe and in south america and also evolving into many different forms some metro rinkheads like cricketsaurus were long and thin with narrow snouts so it would have been agile which was most likely an adaptation to eat small prey like fish or squid they were also one of the smallest metroerinkids as they were around three meters long whereas some of these marine crocodiles could grow to the size of an orca like plesiosuccus in contrast to the long and thin krykosaurus there were other metroerinkids like dakosaurus that was about the same size as a great white shark and had a short and stumpy jaw that was filled with finely serrated teeth these types of teeth are usually seen in animals that are adapted to eating prey much larger than themselves and are very rare in other marine reptiles with their large size and mouth structure they would have hunted large prey perhaps like the other marine reptiles it shared the oceans with like ichthyosaurs it has also been found that dakosaurus's teeth had extensive tooth wear where its larger relative plesiosucus did not these two animals both lived in the oceans of jurassic europe around the same time as each other and the difference in tooth wear means they would have had different diets explaining how they were able to co-exist but surprisingly it was the largest species that was eating the smaller prey as plesiosucus had less damage on its teeth one of the biggest barriers for marine reptiles to take up permanent residents out at sea is that they have to lay their eggs on land fossils from at least one teleosaurid have been found in an area that would have been land during the jurassic showing that some of them weren't stuck in the water however their specializations for swimming were at a point where it seems unlikely they spent very long on land perhaps just hauling up onto a beach to lay their eggs and then back into the water like sea turtles however in the case of metro rinkids from looking at their fossils it seems incredibly unlikely that they would have been able to leave the water to lay their eggs it is well known that some marine reptiles way of reproducing out at sea was to give birth to live young there are numerous ichthyosaur fossils that have fetuses found inside of them that are sometimes even found in the birth canal and there is also a fossil of a pregnant plesiosaur called polycotylus because the other jurassic marine reptiles gave birth to live young it is thought that the meteoria rinkids may have also reproduced like this krykosaurus has a rib and hip structure that was more similar to other marine reptiles like ichthyosaurs and plesiosaurs than other crocodiles so it is possible but this can't be known for certain until a fossil of a pregnant metrorinkid is discovered the teleosaurids went extinct in the early cretaceous about 130 million years ago and the metrorinkids would soon follow just a few million years after this why the thalatosukians went extinct is not completely understood but it is known that in the very late jurassic and early cretaceous there was a small climate changing event that saw sea levels changing although ichthyosaurs and plesiosaurs survived until the late cretaceous they also saw a slight dip in numbers around this time which was probably from the changing sea levels as well so the thalatosukia did not outlast any of the large marine reptile dynasties but they will always show where crocodile evolution can go if the conditions are just right thank you for watching a big shout out to my patrons for supporting the channel especially hunter and marin green falls ryuka grim marshall sammy voz brandon klopp ken ham knight runner nemanja dunderavic calvin dunn jerry the barry and crazy cody if you enjoy content like this then consider supporting the channel as well you

Channel: Moth Light Media

Views: 205,461

Rating: 4.9529738 out of 5

Keywords: Marine Crocodiles, Thalattosuchia, Metriorynchids, Teleosaurids, Machimosaurus, Giant Crcodiles, Sea Crocodile, Ocean Crcodile, Jurassic, Marine Reptile, Animals that lived alongside the dinosaurs, Icthyosaurs, Plesiosaurs, Croc, Marine Croc, Turtle Chompper

Id: xcg-sq1pzD8

Length: 8min 54sec (534 seconds)

Published: Thu Jun 11 2020

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