thank you hello everyone Dr Polaris here throughout history humans have been both fascinated and to an extent terrified of the deep ocean protecting our fears in the form of gigantic sea monsters that Menace Heroes devour ships and inhabit the blank and Far Away spaces of sea on medieval and early modern Maps while the majority of these ancient beasts are strictly imaginary at least some were based on sightings and encounters with very real animals in particular members of the group satacia which contains the whales dolphins and their relatives while these marine animals are quite familiar and even beloved by modern audiences thanks to books films and Nature Documentaries to many ancient cultures whales were giant mysterious monstrosities considered to be the greatest of all fish on a superficial level this is an understandable conclusion as many fully Marine tetrapods do end up resembling fish to a degree due to convergent evolution although even in ancient times there were some who proposed that cetaceans were more like land mammals in the 3rd Century BCE the Greek philosopher Aristotle made many accurate conclusions about cetacean biology noting that the creatures gave birth to live young which were fed on milk lacked gills and possessed lungs and bones that were close to those of mammals however he still sometimes confusingly referred to whales and dolphins as fish which had unfortunately remain an influential Point lasting into the early 20th century if you can believe it today we can confidently state that old Aristotle was almost correct in that citations are definitely mammals although it has only been in the last few decades that their evolutionary history and relationships have been well understood after Decades of uncertainty regarding their origins in the early 20th century it was proposed that cetaceans were either close relatives of or descended from a lineage of basal carnivorous angulus known as mesonicians this was largely due to the superficial similar triangular shape of their teeth with it being assumed that Wales had evolved from terrestrial carnivorous ancestors during the paleogene however it was also very base or citations were almost unknown at this time in 1981 the Primitive and semi-aquatic pachycetus was described revealing a superficially wolf-like animal with carnivorous habits although the remains were not complete lacking the lower Limbs and importantly the ankles it was still held up as being the missing link between cetaceans and Mesa knickers by the early 2000s the proposed relationship to miser nickats came to be questioned with well-preserved basal whale relatives being found that possessed the distinctive double pulley astragalus bone structure unique to True artiodactyls Mesa nikits lacked this feature and are therefore considered to be very distant relatives of cetaceans possibly being the sister group of rtodactyls or perhaps even more basal ungulates the redescription of the small early EOC arteriodactyl endohiers as sister to all citations finally settled this matter with molecular and genetic analyzes also demonstrating that The Closer living relatives of these marine mammals were the hippos with the two groups diverging roughly 53 million years ago other ancient cousins in the broader clade whipper Morpher include the Mysterious Giant androsarcus the vaguely pig-like anthracathias and the imposing intellidons while Indo Hayes was a very close relative of cetaceans it was not a true member of this lineage instead blowing to the sister grip known as the rowelliards these were generally small digital grade Arty adaptables that inhabited what is now the Indian subcontinent and Southeast Asia during the early and middle ear scene despite five Genera having been described and named information about them is very hard to come by online as is typical for many obscure cenozoic mammal groups the only well-known genus seems to be endohias itself which is represented from early eocene age deposits in the Indian region of Kashmir dated to between 50 and 48 million years ago known from an almost complete skeleton Indo hayats was a small animal about the size of a domestic cat and weighed about three kilograms it possessed a relatively narrow snout equipped with quite unspecialized teeth indicating a generalist omnivorous diet similar to Modern pigs in life it probably would have lived much like a chevrotain or small Forest Antelope feeding on soft leaves fruit invertebrates and the occasional piece of scavenged meat or fish in a tropical forested environment despite resembling a fairly typical basal long-legged long-tailed terrestrial artiodactyl studies of its middle ear have revealed a structure very similar to those of cetaceans so this thing that Indo highest was well equipped to detect sound underwater in addition the limb bones of endohias are osteosclerotic this means that the outer dense layer of the bone is unusually thick making them heavier this is found in a whole range of aquatic animals including sea cows beavers hippos and early whales another indicator of aquatic habits is the ratio of oxygen at into Oxygen 16 in endohysis tooth enamel the ratio in this genus is comparable to that scene in aquatic mammals such as the hippopotamus and very different from Land mammals this suggests that this skittish little ungulate probably utilized rivers and lakes in order to hide from predators such as measure knickers and Ox units diving beneath the surface for probably minutes at a time much like the modern African Watershed routine this type of behavior may have been the first step towards the further semiocratic adaptations seen in the first of the true citations with the omnivorous diet of indo-hyus-like forms transitioning towards a more active carnivorous one in the first archaeocetations speaking of which the most basal lineage of cetaceans were the carnivorous semi-aquatic pachycetids which first appear in the fossil record roughly 50 million years ago and were unsurprisingly native to Pakistan and Northern India three Genera have been described all of which were noticeably larger than indo-his being about the size of wolves or larger domestic dogs these animals have been found in or near river deposits in Northern Pakistan and Northwestern India a region which was probably arid with only temporary streams where these animals lived no pachycitas have been found in Marine deposits and they were apparently terrestrial or fresh water animals their long Limbs and small feet also indicate that they were poor swimmers probably being capable of paddling and bounding along the riverbed much like hippos their bones were heavy and Compact and probably used as ballast they clearly indicate Packy seateds were not fast Runners notwithstanding their otherwise cursorial morphology most likely pakisitids lived in or near bodies of fresh water and their diet could have included both land animals and aquatic organisms during the year scene Pakistan was a coastal region of the Eurasian land mass and therefore an ideal habitat for the evolution and diversification of the pakisitids the type genus of the family was pachucetus itself with up to four species being described which range between one to two meters in length with a pointed snout long heavy tail and a full complement of mammalian teeth pachycetus would have resembled a strange canine more than a whale or dolphin unlike endohias its owners were clearly adapted for processing meat with it being suggested the genus fed on fish and other small animals in and around fresh water like modern hippos the eyes were placed high up on the skull and they blame pachucetus to view its surroundings while submerged an effective attribute for a semi-aquatic carnivore although the genus is often depicted with a hairy coat in paleo art it is possible that the living animal may have been largely hairless like hippos and modern cetaceans another pack you see it did ichthyolestes were slightly smaller being about the size of a red fox and possessing a narrow elongated snout well adapted for snapping at fish unlike modern whales and dolphins its nose was located at the tip of the snout and would have breathed much like living semiocratic carnivores pakistutids were a short-lived group assisting for only a few million years before dying out roughly 48 million years ago they were joined in the rivers and lakes of early years in Pakistan by the roughly contemporary and more derived ambula seated which may have evolved directly from the pakistids by far the most famous of these was ambulocytus itself which related to the cul'dana formation of Pakistan between 48 and 47 million years ago it was significantly larger and more heavily adapted for an aquatic existence than the pack is seated placing an elongated narrow snout proportionally large wide feet and eyes that were positioned at the very top of the skull because of these features it is hypothesized to have behaved much like a furry crocodile waiting near the water's surface to Ambush terrestrial mammals utilizing its powerful jaws to clamp down and tear apart prey additionally its ears possess traits similar to Modern cetaceans which are specialized for hearing and detecting certain frequencies underwater although these features were still only marginally developed measuring up to 3 meters or 10 feet long and weighing in the region of 300 kilograms or 660 pounds ambulocetus was comparable to a male South American sea lion in terms of size and much like living Pinner pads it may have been capable of still walking about on land albeit rather clumsily although some recent Studies have suggested that it was almost totally aquatic in nature in life this car never respond probably swam in a similar manner to otters utilizing its large webbed feet and flexible torso for propulsion underwater stable Carbon on oxygen isotope fallacies indicate Amino acetous inhabited brackish Coastal Waters probably at or near river mouths where it lived alongside Requiem sharks catfish Turtles and crocodilians the genus may have also preyed on the stem parisodactyl anthracabune when it came down to the river to drink two other Genera of ambula seated are known and both were also native to Pakistan during the early ear scene with these being Gunda cassia and himalayasitas although they are represented here by a very fragmentary Remains by around 47 million years ago another more derived family of alkylositations had appeared in the indo-pakistan region of the tethis sea which was the epicente of whale evolution these were the Remington assetids which took Marine adaptations a step further than their earlier relatives with elongated bodies and muscular Tails adapted for otter-like underwater Locomotion their snouts were narrow and almost garial-like being equipped with conical teeth at the front of the Jaws and slicing triangular molars at the rear well suited for grabbing and slicing through slippery fish and Squid the eyes were small and Beady somewhat like those of living river dolphins sitting that Remington has seated did not primarily rely on Vision to hunt prey perhaps utilizing hearing and touch via sensitive snouts the type genus Remington acetis was native to Northern India and Pakistan between 45 and 43 million years ago this slender Renault measured about 3.5 meters or 11.5 feet long and would have been an effective swimmer with a streamlined body long tail and flat and hydrodynamic skull the limbs were short but probably still enabled Remington acetas to come out of the water to rest and give birth the related coochie suits was generally similar but was notably smaller measuring just two meters long and resembled a strange hybrid of agarial as an otter the tail was elongated and powerfully muscled clearly playing a very important role in swimming when compared to the short and gracile limbs the narrow Jaws would have been effective at making quick snapping motions in order to seize fish and other small aquatic animals in life kuchu has probably lived in coastal Enviro months and was better adapted for ocean-going hunting than ambulocetus and relatives although it almost certainly preferred shallow lagoons to the Open Sea it was once thought that Remington are suited to restricted to India and Pakistan being unable to Journey further afield however a middle ear Saint member of the family ryanisties was discovered in Egypt in 2016. demonstrating that these animals had spread across the tethis and proving that they were more powerful swimmers than previously thought although successful these crocodile otters died out by around 43 million years ago probably being out competed but that more derived relatives such as the proto-seated although ones thought to be a genuine grouping in recent studies the proto-c tits have been considered to perform a grade rather than a clade that leads towards the totally Marine bacillusaurids these animals were diverse and widespread being the first citations to spread well beyond the tethis sea but their range reaching into West Africa Eastern North America and the Pacific Coastline of South America like modern pinnipeds proto-seateds were clearly strong swimmers capable of Crossing significant stretches of open ocean although they probably would have hugged the coastline in order to find places to rest and to escape from sharks and other Marine Predators some species are well represented in the fossil record Being known from near complete skeletons which are given paleontologists a firm idea of their biology and life appearance one of the better understood Genera was rhodocetus from the middle ear scene of Pakistan measuring up to three meters long and possessing a heavier build than the Remington are suited this semi-aquatic animal would have weighed up to 1 300 pounds in large male individuals the sacrum was immobile unlike in more basal archaeuscitations while the limbs were quite short and terminated in Broad webbed feet furnished with elongated digits despite being better adapted for a sea gulling lifestyle visible traces of its terrestrial artsyodactyl ancestors remained including the possession of small blunt Hooves at the tips of the digits the typical double pulley astragalus unique to even-toed ungulates and differentiated heterodont teeth reconstructions of its Anatomy have revealed many similarities to the modern Desmond a semi-aquatic member of the mole family which is a hind foot-propelled diver that uses its tail as a Rudder it seems likely that rhodo Sita swam in a similar manner but the living animal probably being largely hairless and quite blubbery like seals and sea lions this may have also given it a passing resemblance to its distant modern cousin the hippopotamus when it was hauled out on land the related genus mayacetus was quite similar with a remarkably well-preserved specimen containing an unborn fetus which was positioned head first this suggests that this animal and probably other a semi-aquatic archaeuscitations gave birth on land with modern cetaceans developing from Young born tail first instead the hip bones of mayacetus were still strongly developed although the short legs would have given it a waddling awkward gate when walking on the beach while the middle ear bones are similar to those of the totally marine basilosaurus and living toothed whales preventing an odd mixture of traits wedged between Land and Sea some proto-seaters were very widespread but the genus peregocetus being found in France Italy and Peru being the oldest known quadrupedal cetacean to inhabit the southern hemisphere other members of the family becoming more obviously whale or dolphin-like such as the Egyptian protocetus this modestly sized 2.5 meter genus possessed a more streamlined fusiform body shape with nostrils at positioned halfway up the snout representing an early stage in the development of a blowhole the bones at the tail tip indicate the presence of a small fluke enabling more efficient swimming from forms such as this and the more derived Georgia cetus the first truly Marine cetaceans would evolve by the middle ear scene roughly 43 million years ago in the form of the bacillusaurids these would also be the first citations to possess a near global distribution as well as producing the largest mammals on Earth during the eocene in the form of the 17 meter long apex predator bacillosaurus however discussion of these animals and the emergence of True Modern whales from them will have to wait for a future video thanks for watching everyone the next episode will be covering the rise and development of the saber tooth Permian gorgonopsians so until then I'll see you again soon cheerio