Prehistoric Breakdown: Platecarpus

Added: 2026-05-22

[00:00:04]North America 82 million years ago a continent half covered by a sea of monsters.

[00:00:13]From sharks to plesiosaurs, every living thing makes the most of the shallow seas plentiful resources.

[00:00:21]In an ecosystem filled with giant reptiles and fish it might be surprising to learn even a mosasaur the size of a modern saltwater crocodile is considered small.

[00:00:33]The mosasaur in question is a young adult platycarpus.

[00:00:38]5.8 m long with a uniquely short blunt skull.

[00:00:42]He is far from the 14-plus giants that rule these rich waters.

[00:00:48]Unlike their larger relatives, however, platycarpus can be found worldwide from Belgium to Australia.

[00:00:55]As it's not just size that makes a species successful.

[00:00:59]This male, however, is struggling to catch anything recently and has traveled towards the coast where he knows prey will be in abundance.

[00:01:10]Near the end of the day, mass amounts of Hesperornis haul themselves out of the surf onto dry land to sleep on the beaches in large colonies.

[00:01:20]The platycarpus has hunted by the shores of these colonies both in the morning and in the afternoon when the seabirds enter and exit the water often being successful.

[00:01:31]But today he is too late, only seeing the last of the feathery dinosaurs ride the waves to the safety of dry land.

[00:01:41]Undeterred, he heads for a different feeding spot with different prey.

[00:01:47]As the sun sets lower on the horizon, the platycarpus approaches a mass of migrating fish currently being harassed by multiple species of plesiosaurs.

[00:01:58]Fish form the main part of platycarpus diet, but this individual has not quite mastered the art of catching fish out of a swarm.

[00:02:08]And as he swims through the massive school, his prey part before him, leaving a half a meter gap between them and the predator.

[00:02:17]He makes a few darting lunges at them, but the constantly moving mass is disorientating, and he doesn't catch a thing.

[00:02:25]He could try and grab one of the juvenile plesiosaurs, but they are well protected by the adults, and he knows from first-hand experience that the bite of a plesiosaur is very painful.

[00:02:38]Fortunately, there is another option.

[00:02:40]Diving into the water from the skies above is a flock of pteranodon.

[00:02:45]These large flyers are braving the dangerous waters in order to snare some fish in their long jaws, and each is experienced in grabbing a morsel and ascending back into the air as swiftly as possible.

[00:02:58]The platycarpus listens to the sounds of the flying reptiles spear into the sea one after another.

[00:03:05]Unable to see through the great number of fish, and steadily he swims towards where he thinks a few of the pteranodon have impacted.

[00:03:14]He drew closer and increased his speed.

[00:03:17]The fish parted, and above him, to his left, he saw several of the pterosaurs had made it to the surface and were rapidly beating their wings to get airborne.

[00:03:26]He corrected his course and accelerated towards the nearest one. Each took off into the sky, leaving only ripples in their wake. The platycarpus opened his jaws, about to bite into the pterosaur's foot.

[00:03:38]He broke the surface and snapped his jaws shut, but just missed, crashing back down into the water, his target only just escaping.

[00:03:47]As bubbles churned around him, the The was forced to twist out of the way as two of the plesiosaurs came from below snapping their jaws at him.

[00:03:56]Apparently, he got too close to their young and was chased away from both the pod and the school of fish.

[00:04:03]Having used up more energy for nothing, the platycarpus swam to deeper water as the sun dipped below the horizon.

[00:04:13]Hours later and far more hungry, the male mosasaur is still looking for food.

[00:04:19]Tasting the water with his forked tongue and feeling the current of the ocean over his body.

[00:04:25]Then another platycarpus swims past him, seeming to be in a rush.

[00:04:30]He tastes the water again and picks up on the potential source of food the other reptile is swimming towards.

[00:04:38]Following his fellow mosasaur, the male soon finds the source of the smell.

[00:04:44]A mass amount of platycarpus have gathered at this location, over a dozen.

[00:04:50]But none have been bold enough to make the first move.

[00:04:54]For the creature below them is one of the world's true giants, an 18-m long octopus, the Nanamoteuthis, the kraken of the Cretaceous.

[00:05:09]A top order carnivore in the world's oceans, but this one is acting strangely.

[00:05:15]Normally, they do not rest near the ocean's surface, preferring deeper waters where they can hide in the dark.

[00:05:22]This Nanamoteuthis is old, nearing the end of its life.

[00:05:27]Unlike some modern giant squid, has floated to the surface almost by accident.

[00:05:33]Even near death, the platycarpus continue to circle, not wanting to get within reach of the powerful tentacles of the large octopus.

[00:05:42]The young male does the same for a while, watching it bob up and down just below the waves.

[00:05:49]But his hunger gets the better of him and he rushes forward to take a bite.

[00:05:53]His teeth spear into the soft flesh of one tentacle and he thrashes his head a few times ripping the end from the body.

[00:06:00]He then turns to swim away but another tentacle grabs his tail and a third tries to wrap around his rear left fin.

[00:06:07]Struggling to break free, the near 6-m lizard is not as strong as the name of toothless even though it is hours away from death.

[00:06:16]But the male's attack was enough to spur on the rest of the platycarpus and one by one the short jaws of the reptiles bite into the body, head, and tentacles of the giant.

[00:06:28]Reacting to the new threat, the name of toothless releases the male and tries to fend off the mass of attackers.

[00:06:35]But with over a dozen of the predators ripping and fleeing over and over again, plus his own limbs being severed at different points, his struggle was minimal and soon his body shut down completely.

[00:06:48]The platycarpus had turned the tide on the monster cephalopod.

[00:06:53]Each took turns tearing apart its colossal form.

[00:06:56]Though even they would not be able to eat all of it.

[00:07:00]If they could, they'd leave only the hard beak to float to the bottom of the sea.

[00:07:06]The now satisfied male chomped down the last piece of giant calamari that his stomach could fit and he returned to the surface to breathe and rest along with a few others of his kind.

[00:07:20]Enjoying the relative calm before all manner of aquatic scavengers arrived to finish what the platycarpus started.

[00:07:31]Hello fellow travelers and welcome back.

[00:07:34]Today we will be breaking down one of the smaller genera of mosasaurs from the Western Interior platycarpus.

[00:07:44]The first remains of Platycarpus were discovered by Professor B.F. Mudge and described by Edward Drinker Cope in 1869.

[00:07:53]But originally it was identified as a different genus of mosasaur called Clidastes.

[00:08:00]It wasn't until 1898 that further analysis saw these remains given their own genus name, that being Platycarpus, which means flat wrist.

[00:08:11]From there, many remains have been attributed to Platycarpus and a number of species names given to it. However, most turned out to be their own genera or ended up being too fragmentary to assign even at a genus level.

[00:08:27]Most remains have been found in the US, especially in the state of Kansas, but other fossils attributed to Platycarpus have been found in Belgium, Canada, Africa, and Australia.

[00:08:38]It was a mosasaur in the large subfamily called the Plio-Platycarpinae.

[00:08:44]It lived during the late Santonian to the early Campanian, between 84 and 81 million years ago.

[00:08:51]Now, plenty of individual Platycarpus have been discovered, especially from the Smoky Hill Chalk Member. But despite having a wealth of fossils, only one complete skeleton has been found and with it the only complete skull as well.

[00:09:07]The specimen was given the designation LACM 128319.

[00:09:14]And from it has come a wealth of knowledge on the species as a whole.

[00:09:19]For a mosasaur, it was considered small, being 6 m long and weighing around a ton.

[00:09:25]With a short, compact skull, all limbs having developed into flippers, a long, streamlined body, and an even longer tail that ended in a fluke.

[00:09:34]Let's break down its anatomy in more detail, starting with the skull, which had quite a few unique features.

[00:09:40]For one, it is very short for its body size.

[00:09:44]And it has the lowest number of teeth out of any mosasaur.

[00:09:49]These teeth were conical and curved backwards, but were far less robust than other members of its family, leading to the theory that Platecarpus may have been specializing in soft-bodied prey.

[00:10:01]Though specialized may be a bit of a stretch, as this includes fish and squid, a very plentiful food source.

[00:10:10]This is supported by the fact that fish remains were found in the stomach cavity of LACM 128319, which I will be referring to as LACM from now on.

[00:10:22]Having a smaller, shorter skull, Platecarpus may have had better stereoscopic vision.

[00:10:28]Not having a long snout in the way likely gave it much better coordination when it came to hunting fast-moving prey.

[00:10:36]On the skull of LACM, scleral rings were found. These reinforce the eye, and apparently even traces of the retina were preserved.

[00:10:46]Like other mosasaurs, Platecarpus had extra teeth in the back of the jaws, called the pterygoid teeth.

[00:10:53]These would have been used to get extra grip on slippery prey, and when swallowing, acted like a conveyor belt to drag prey down the throat.

[00:11:04]LACM even preserved a part of the respiratory tube near the shoulder girdle.

[00:11:09]The tube split into two, showing that it had two lungs, which sounds obvious, but many modern snakes only have one lung.

[00:11:19]Snakes and lizards are the closest relatives of mosasaurs, with them all being in the Squamata order.

[00:11:26]Snakes likely losing their second lung, along with their limbs and other adaptations to become misunderstood danger noodles.

[00:11:35]Each limb had shortened, but it still retained all five digits, which had extended and developed into flippers.

[00:11:43]Though these likely played more of a role in steering than in propulsion.

[00:11:47]That was done by the long tail. And it's thanks to Platycarpus that we now know a lot more about how many mosasaurs use them.

[00:11:56]For a long time, it was thought that these giant marine lizards were moving in an anguilliform motion, using most of their bodies like an eel.

[00:12:05]But a few good remains show that more derived mosasaurs at least had a tail fluke.

[00:12:11]Many marine animals have flukes, from sharks to dolphins. And on the reptile side of the tree, ichthyosaurs.

[00:12:18]We can tell where the fluke began because the vertebra chain shaped partway down the tail, becoming shorter and more like a disk.

[00:12:26]To quote, "The neural spines of these vertebra also have grooves for the insertion of interspinal ligaments and dorsal connection tissues, which would have aided in lateral movement of the fluke." End quote.

[00:12:41]What this means is that every time the animal swung its tail to move, the special ligaments would pull it back into a neutral position.

[00:12:48]This is an energy-saving adaptation, which also meant the tail fluke was doing most of the work when it came to locomotion. So, the rest of the tail, and indeed the rest of the body, didn't move that much.

[00:13:00]This is known as carangiform movement, seen in many fish like sharks, showing how well adapted Platycarpus and many other mosasaurs were adapted to aquatic life.

[00:13:12]Even its scales had evolved, as we have impressions of them across the body of LACM.

[00:13:19]They were small and nearly uniform in shape across the entire body, making the torso stiffer and more hydrodynamic.

[00:13:27]Though the scales on the face do differ, with those on the snout being hexagonal and not touching, while those on the jaws were overlapping and being more rhomboidal in shape.

[00:13:40]They were likely also thicker, probably for better protection against predators and each other.

[00:13:46]It's not just scales and fish remains that were preserved in LACM.

[00:13:50]The fossil was so well preserved that there were even impressions of some internal organs around the rib cage.

[00:13:58]Though they seem to have gone through some level of decay before they fossilized.

[00:14:03]Based on their position and the size, these may be the heart, liver, and kidneys.

[00:14:09]The kidneys are in a bit of an odd place for a squamate, but this may be an adaptation for aquatic life, as modern whales also have their kidneys in the same position. An interesting case of convergent evolution.

[00:14:24]Going back to the fish remains found in the stomach cavity, it was noted that not just the bones of the fish were preserved, but scales as well. So, why is this important?

[00:14:35]Coprolites, which are fossilized dung attributed to another mosasaur species called Globidens, contains a large amount of crushed bivalve shells.

[00:14:46]Basically, they went through the whole digestive tract with little damage.

[00:14:51]This, along with evidence of Platecarpus not being able to fully break down bones and scales, suggests that mosasaurs may have either had a fast digestive process or not a very powerful one and weren't able to break down all of the hard parts of the food they ate, unlike say crocodiles that can digest bone.

[00:15:12]Isotopic analysis of the teeth of Platecarpus showed something very interesting. They were on occasion entering freshwater.

[00:15:20]Now, this may have been to hunt or breed, but it has been suggested Platecarpus and some other relatives may have sought out fresh water simply to drink it, being unable to process the salt water of the ocean.

[00:15:34]This is seen in modern sea snakes as they don't have salt glands like sea turtles who are able to drink salty water and secrete the excess salt they don't need.

[00:15:45]As we can see, Platecarpus, and especially LAC 128319, has given us a wealth of knowledge on its own genus, mosasaurs, and marine life at that time in general.

[00:15:59]There were many mosasaur genera in the Late Cretaceous, and though we may not know as much about every one of them as we do about Platecarpus, it's great to have at least one genera that has so many fossils and in such good condition to reveal so much about their lives.

[00:16:16]But, what do you think of Platecarpus?

[00:16:18]And for my question of the week, do you see Platecarpus as a sort of blueprint for a standard mosasaur, or more as the family's fish and squid specialist?

[00:16:29]What lesser known marine reptile would you like me to do a breakdown on next?

[00:16:33]And until then, please like, share, subscribe, and thank you for watching.