These earliest cetaceans were not like the whales we know today, and only recently have paleontologists been able to recognize them. The eyes of Pakicetus faced to the side and slightly upward. mesonychids limbs and tail. That's ALL he does! About 375 million years ago, the first tetrapodsvertebrates with arms and legspushed themselves out of the swamps and began to live on land. 3 0 obj << /Linearized 1 /O 5 /H [ 677 158 ] /L 5375 /E 5050 /N 1 /T 5198 >> endobj xref 3 14 0000000016 00000 n 0000000624 00000 n 0000000835 00000 n 0000000988 00000 n 0000001184 00000 n 0000001289 00000 n 0000001393 00000 n 0000001499 00000 n 0000001552 00000 n 0000002666 00000 n 0000003413 00000 n 0000004908 00000 n 0000000677 00000 n 0000000815 00000 n trailer << /Size 17 /Info 2 0 R /Root 4 0 R /Prev 5189 /ID[<4e5292bec552ff6cdecba3d79dd8a517><4e5292bec552ff6cdecba3d79dd8a517>] >> startxref 0 %%EOF 4 0 obj << /Type /Catalog /Pages 1 0 R >> endobj 15 0 obj << /S 36 /Filter /FlateDecode /Length 16 0 R >> stream Pakicetus inachus, a New Archaeocete (Mammalia, Cetecea) from the early-middle Eocene Kuldana Formation of Kohat (Pakistan). This puts mesonychids as a distant relative of cetaceans rather than an ancestor, and their somewhat similar morphology was possibly a result of convergent evolution. [1], Mesonychids possess unusual triangular molar teeth that are similar to those of Cetacea (whales and dolphins), especially those of the archaeocetes, as well as having similar skull anatomies and other morphologic traits. A recent study found mesonychians to be basal euungulates most closely related to the "arctocyonids" Mimotricentes, Deuterogonodon and Chriacus. Nearly all mesonychids are, on average, larger than most of the Paleocene and Eocene creodonts and miacoid carnivorans. Thewissen, J.G.M and Hussain, S.T. [6], Mesonychids varied in size; some species were as small as a fox, others as large as a horse. This, in combination with its inferred diet (see below) and inferred ability to walk on the bottom, suggests that it attacked its prey from below. 2007). Cetaceans, like many other mammals, have ear bones enclosed in a dome of bone on the underside of their skulls called the auditory bulla. Your Privacy Rights Mesonychids [1] were the first mammalian carnivores after the extinction of the dinosaurs . They are not closely related to any living mammals. Mesonychids are a mostly Eocene group that originated in the Paleocene; Mesonyx, from the Middle Eocene of North America, was the first member of the group to be named (Cope published the name in 1872), and it's still one of the most familiar mesonychians, by which I mean one of the kinds featured most frequently in the popular and semi-technical literature. Contributions are fully tax-deductible. By the time the first mammals evolved 200 million years ago, however, dinosaurs were the dominant vertebrates. There was only one other kind of creature with an inner ear that matched: a whale. - . 2007. However, recent work indicates that Pachyaena is paraphyletic (Geisler & McKenna 2007), with P. ossifraga being closer to Synoplotherium, Harpagolestes and Mesonyx than to P. gigantea. While later mesonychids evolved a suite of limb adaptations for running similar to those in both wolves and deer, their legs remained comparatively thick. "Triisodontidae" may be paraphyletic. Mesonychids e.g. Not to toot my own horn, but I found this article very inspiring. There don't seem to be very many reconstructions of these critters available online.http://viergacht.deviantart.com/art/Harpagolestes-133779748, Very nice, Viergacht! Madar, S. I. 2023 Smithsonian Magazine So, in the sheep figure, anterior is to the left and above. While the limb proportions and hoof-like phalanges indicate cursoriality, the limbs were relatively stout and show that it cannot have been a long-distance pursuit runner. The phylogenetic position of cetaceans: further combined data analyses, comparisons with the stratigraphic record and a discussion of character optimization. This major evolutionary transition set the stage for all subsequent groups of land-dwelling vertebrates, including a diverse lineage called synapsids, which originated about 306 million years ago. However, the close grouping of whales with hippopotami in cladistic analyses only surfaces following the deletion of Andrewsarchus, which has often been included within the mesonychids. All rights reserved. Archaic ungulates ("Condylarthra"). A number of other mesonychian taxa have conventionally been included within Mesonychidae. Mesonychids probably originated in China, where the most primitive mesonychid, Yangtanglestes, is known from the early Paleocene. 1998. Long-snouted marsupial martens and false thylacines, Marsupial 'bears' and marsupial sabre-tooths, Because it would be wrong not to mention a sperm whale named like a tyrannosaur, http://viergacht.deviantart.com/art/Harpagolestes-133779748, http://www.archive.org/details/introductiontoos1885flow, The Lab Leak Theory Was Dismissed As Trump Xenophobia - Now Deniers Say It Was Not Accepted Because of Trump Xenophobia, DAN5/P1: Homo Erectus Early Cranial Capacity Was More Like Australopiths Such As 'Lucy', DART Made A Big Difference In Ability To Accurately Calculate Asteroid Deflections, The Subsidies Paradox: Affordable Food Versus The Environment, Degrowth communism as asolution for climate change. On January 23rd 2007, Tet Zoo ver 2 - the ScienceBlogs version of Tetrapod Zoology - graced the intertoobz for the first time. It had limbs like a land animal and webbed toes in replacement for fins, suggesting that it recently changed from land to water through evolution. [13][14] One possible conclusion is that Andrewsarchus has been incorrectly classified. Adapted fromWritten in Stone: Evolution, the Fossil Record, and Our Place in Nature, by Brian Switek. Darwin had done no such thing, but the jeering caused him to modify the passage in subsequent editions of the book. Richard Owen, a rising star in the academic community, carefully scrutinized every bone, and he even received permission to slice into the teeth to study their microscopic structure. mesonychids limbs and tail. There was rapturous applause, swooning, the delight of millions. Harlan traveled to London in 1839 to present Basilosaurus to some of the leading paleontologists and anatomists of the day. Mesonychids possess unusual triangular molar teeth that are similar to those of Cetacea (whales and dolphins), especially those of the archaeocetids, as well as having similar skull anatomies and other morphologic traits. Summary written by Jonathan Geisler and Melody Ho. (1988) to name a new clade, Hapalodectini, which they regarded as the sister-taxon to a (mesonychid + (Andrewsarchus + cetacean)) clade (that's right, they regarded Andrewsarchus as the sister-taxon to Cetacea). Isotopic records from early whales and sea cows: contrasting patterns of ecological transition. These "wolves on hooves" were probably one of the more important predator groups in the late Paleocene and Eocene ecosystems of Europe (which was an archipelago at the time), Asia (which was an island continent), and North America. Nature 413:277281. Posted by ; dollar general supplier application; Mesonychids probably originated in China, where the most primitive mesonychid, Yangtanglestes, is known from the early Paleocene. ? Together they illustrate how the entire transition took place. Adult fish, chickens, dogs, and lizards don't look much like humans. There were bone-cracking scavengers, small jackal or fox-like generalists, large wolf-like hunters, and so on. homestead high school staff. > given that mesonychian meat processing really didn't seem While later mesonychids evolved a suite of limb adaptations for running similar to those in both wolves and deer, their legs remained comparatively thick. The order is sometimes referred to by its older name "Acreodi". > traditional characterisation as archaic,'inferior' One genus, Dissacus, had successfully spread to Europe and North America by the early Paleocene. Clarendon Press (Oxford), pp. In Janis, C. M., Scott, K. M. & Jacobs, L. L. (eds) Evolution of Tertiary Mammals of North America. His attention to such tiny details ultimately settled the identification of the sea monster. In some localities, multiple species or genera coexisted in different ecological niches. The sound passage via the external ear of Pakicetus was intact and was similar to that of other mammals. Yantanglestes from Paleocene Asia (originally described as a species of Dissacus) is also thought to be a basal member of the group. Furthermore, the lumbar region wasn't as flexible as it is in carnivorans: the zygapophyses have the peculiar revolute morphology seen in modern artiodactyls (where the prezygapophyses are medially concave and prevent movement of the short, laterally convex postzygapophyses: see adjacent photos of sheep zygapophyses [and many thanks to Augusto Haro for pointing out a previous mistake made here, now corrected]). But, because they are mammals, we know that they must . 292-331. Geisler, J.G.,Theodor, J.M. & Geisler, J. H. 1999. Early mesonychids probably walked on the flats of their feet (plantigrade), while later ones walked on their toes (digitigrade). Mesonyx species have been estimated as 1.25-1.5m (4.5-5 ft.) long in life, not including the tail. Glad you tooted. Age: But where skeletons are known, they indicate that mesonychids had large heads with strong jaw muscles, relatively long necks, and robust bodies with robust limbs that could run effectively but not rotate the hand or reach out to the side. 2009. Rather, they're the better known ones: the ones that have been included in phylogenetic studies, or the ones known from remains complete enough that allow functional or palaeobiological inferences to be made. However, these specimens generally lack forelimbs, hind limbs, and tails. If mathematical, chemical, physical and other formulas are not displayed correctly on this page, please useFirefox or Safari, This article is about the prehistoric ungulate. Some members of the group are known only from skulls and jaws, or have fragmentary postcranial remains. Cooper, L.N., Thewissen, J.G.M., and Hussain, S.T. Ambulocetus's skull was quite cetacean (Novacek 1994). See you there. The fossil remains of such a creature remained elusive. 1999. Little more than the back of the animals skull had been recovered, but it possessed a feature that unmistakably connected it to cetaceans. With the permission of the publisher, Bellevue Literary Press. The early representatives of these groups appeared about 33 million years ago and ultimately gave rise to forms as diverse as the Yangtze River dolphin and the gigantic blue whale. Its type genus is Mesonyx. One possible conclusion is that Andrewsarchus has been incorrectly classified. Museum of Paleontology 25:235-246. Cope admitted in an 1890 review of whales: The order Cetacea is one of those of whose origin we have no definite knowledge. This state of affairs continued for decades. Based on this, Pakicetus retained the ability to hear airborne sound. They first appeared in the Early Paleocene, undergoing numerous speciation events during the Paleocene, and Eocene. The head End of preview Want to read all 2 pages? There are currently 4 species of Pakicetus: Pakicetis inachus, P. attocki, P. calcis, P. chittas. wzi88?&wXo. These forms eventually died out, but not before giving rise to the early representatives of the two groups of whales alive today, the toothed whales and the baleen whales. In Benton, M. J. Which embryo is human? Recent fossil discoveries have overturned this idea; the consensus is that whales are highly derived artiodactyls. Nature 450, 1190-1195. Geisler, J. H. 2001. However, the close grouping of whales with hippopotami in cladistic analyses only surfaces on deletion of Andrewsarchus, which has often been included within the mesonychids. Hr6prGO]di3nO[wK]DQ %H'U : yqsOa&'gR@&,CEN~I.{8Kei^I&. American Zoologist 41, 487-506. They would have resembled no group of living animals. Clementz, M. T., A. Goswami, P. D. Gingerich, and P. L. Koch. References Consulted: These animals would have migrated to North America via the Bering land bridge. A million years later livedAmbulocetus, an early whale with a crocodile-like skull and large webbed feet. In 1832, a hill collapsed on the Arkansas property of Judge H. Bry and exposed a long sequence of 28 of the circular bones. Inside Nature's Giants: polar bear special, Nick Saunders's Battlefield Archaeology Is Much Better Than Everybody Else's, Dark Matter: what it does, what it doesn't do. Inside Nature's Giants: a major television event worthy of praise and accolade. Reconstructions of pakicetids that followed the discovery of composite skeletons often depicted them with fur; however, given their close relationships with hippos, they more likely had sparse body hair. Szalay, F. S. & Gould, S. J. As E.D. Copyright 2010. Blubber, blowholes and flukes are among the hallmarks of the roughly 80 species of cetaceans (whales, dolphins and porpoises) alive today. Image credit: NASA / Apollo 17. While, as noted earlier and elsewhere, Pachyaena and other mesonychids are often imagined as wolf-like, the good data we have on the osteology of this animal show that it was quite different from a canid in many respects. Brys donation was soon matched, and even exceeded, by that of Judge John Creagh from Alabama. can general dentists do bone grafts; apple tartlets with pillsbury pie crust; what bulbs will squirrels not eat; can cinnamon cause a miscarriage; mesonychids limbs and tail. Is there any hard evidence for the sexual dimorphism - the males having blunt, heavy, bone-crushing teeth, the females having blade-like ones - suggested for *Ankalogon* and *Harpagolestes* in the popular and semi-technical literature? Some mesonychids are reconstructed as predatory (comparable to canids), others as scavengers or carnivore-scavengers with bone-crushing adaptations to their teeth (comparable to the large hyenas), and some as omnivorous (comparable to pigs, humans, or black bears). You're welcome. The basic design of all these animals is more similar than you might think. Zygorhiza is fairly common in the Gulf Coastal region of the southeastern United States. Many species are suspected of being fish-eaters, though some of these reconstructions may be influenced by earlier theories that the group was ancestral to cetaceans. Even better, two jaw fragments showed that the teeth ofPakicetuswere very similar to those of mesonychids. But where skeletons are known, they indicate that mesonychids had large heads with strong jaw muscles, relatively long necks, and robust bodies with robust limbs that could run effectively but not rotate the hand or reach out to the side. They were also most diverse in Asia, where they occur in all major Paleocene faunas. Together, these traits suggest that Pakicetus represents an early stage in the evolution of cetaceans, one where many running adaptations were retained but rarely used. An unrelated early group of mammalian predators, the creodonts, also had unusually large heads and limbs that traded flexibility for efficiency in running; large head size may be connected to inability to use the feet and claws to help catch and process food, as many modern carnivorans do. So why do these embryos look so much alike? Take a look at our home planet, Earth, and one of the things you'll notice is that over 70% of the surface is coated in water. With a short lower spine stiffened by revolute joints, they would have run with stiff backs like modern ungulates rather than bounding or loping with flexible spines like modern Carnivorans. ScienceBlogs is where scientists communicate directly with the public. We do not collect or store your personal information, and we do not track your preferences or activity on this site. USA Distributor of MCM Equipment mesonychids limbs and tail One particular ankle bone, the astragalus, had the potential to settle the debate. deer, camel, pigs) and appears to be adapted for running at high speeds. This page was last updated at 2022-07-17 03:07 UTC. [5]. The skeleton of Pakicetus resembles those of many other even-toed hoofed mammals (e.g. He tentatively assigned it the name Basilosaurus. Part I! Now the tide has turned. In fact, the density of the limb bones of Pakicetus is so great that they would have been at increased risk of breakage during running. There is a grain of truth in the cat versus dog question. Ambulocetus's skull was quite cetacean (Novacek 1994). Skulls and teeth have similar features to early whales, and the family was long thought to be the ancestors of cetaceans. I've been in Romania and Hungary where I had a great time - saw lots of neat animals (fossil and living) and hung out with some neat people. The fore limbs are so much shorter than the hind limbs that the animal customarily sat on its haunches when on land. The only other possible aquatic characteristics evident in its skeleton are scars on the toe bones that indicate strong muscles for separating the toes. It had a long muzzle, teeth that were very similar to later archaeocetes, a reduced . 8. Were there really any distance runners in the paelogene? Looking back at it now, that very first ver 2 post is rather odd. Huxley in 1871, Darwin asked whether the ancient whale might represent a transitional form. Author: That the whole South should commit itself to the principle that the colored people have a right to be educated is an immense acquisition to the cause of popular education.Fannie Barrier Williams (18551944), America loves the representation of its heroes to be not just larger than life, but stupendously, awesomely bigger than anything else. Mesonychid dentition consisted of molars modified to generate vertical shear, thin blade-like lower molars, and carnassial notches, but no true carnassials. Sensory Abilities: LikeBasilosaurus, though,Squalodonwas fully aquatic and provided few clues as to the specific stock from which whales arose. | READ MORE. Privacy statement. For another, more detailed, article about Mesonychidae, see, Creative Commons Attribution-ShareAlike License. As in most land mammals, the nose was situated at the tip of the snout. When the unnerved scientists gathered the fragments, they noticed that the bone now revealed the inner ear. There is evidence to suggest that some genera were sexually dimorphic. Like the Paleocene family Arctocyonidae, mesonychids were once viewed as primitive carnivorans, and the diet of most genera probably included meat or fish. Throughout the Paleocene and Eocene, several genera, including Dissacus, Pachyaena and Mesonyx would radiate out from their ancestral home in Asia and into Europe and North America, where they would give rise to new mesonychid genera. The foot was compressed for efficient running with the axis between the third and fourth toes (paraxonic); it would have looked something like a hoofed paw. Given that the hippopotamus is the closest living relative of cetaceans, Pakicetus and hippos may have inherited this behavior from their common ancestor. It's on the blood-feeding behaviour of, So sorry for the very short notice. The cervical vertebrae were relatively long, compared to those of modern whales; Ambulocetus must have had a flexible neck. Hb``a``Z b. (1995), Geisler and McKenna (2007) and Spaulding et al. 1946). They were endemic to North America and Eurasia during the Early Paleocene to the Early Oligocene, and were the earliest group of large carnivorous mammals in Asia. I'll talk about some of this, Yet more from that book project (see the owl article for the back-story, and the hornbill article for another of the book's sections). Postcranial skeleton of the early Eocene mesonychid Pachyaena (Mammalia: Mesonychia). Harpagolestes and Mesonyx appear to be sister-taxa, and the most derived of mesonychids (O'Leary & Geisler 1999, Geisler 2001, Thewissen et al. Upload your study docs or become a member. Mesonychidae They were also most diverse in Asia where they occur in all major Paleocene faunas. Origins of underwater hearing in whales. These ancestral creatures were stranger than anyone ever expected. Inside, If you didn't know, I've been away. The semi-aquatic otters and beavers, he claimed, were better alternative models for the earliest terrestrial ancestors of whales. (1995); and to Cete by Archibald (1998);[7] and to Mesonychia by Carroll (1988), Zhou et al. The phylogeny of the ungulates. We all know why this is, of course: it's because the Earth's oceans float atop the rocks and dirt that make up what we know as, "You still don't get it, do you? Journal of Vertebrate Paleontology 15, 387-400. Based on the orientations of the wear facets, Pakicetus sheared its prey into smaller pieces before swallowing. 1846. Where whales differ is that the margin of the dome closest to the midline of the skull, called the involucrum, is extremely thick, dense, and highly mineralized. In this case, the resemblances to early whales would be due to convergent evolution among ungulate-like herbivores that developed adaptations related to hunting or eating meat. For another, more detailed, article about Mesonychidae, see, Sarah L. Shelley, Thomas E. Williamson, Stephen L. Brusatte, Resolving the higher-level phylogenetic relationships of Triisodontidae (Condylarthra) within Placentalia, October 2015, Society of Vertebrate Paleontology (abstract), "New Mesonychid mammals found from lower Paleogene of Erlian Basin, Nei Mongol", "Carnivores, creodonts and carnivorous ungulates: Mammals become predators", 10.1671/0272-4634(2000)020[0387:ANSOAM]2.0.CO;2, "Mesonyx and the other mesonychid mesonychians (mesonychians part IV) | ScienceBlogs", "The position of Hippopotamidae within Cetartiodactyla", "Evidence from milk casein genes that cetaceans are close relatives of hippopotamid artiodactyls", https://en.wikipedia.org/w/index.php?title=Mesonychid&oldid=1115476645, This page was last edited on 11 October 2022, at 17:25. Let's back up a bit, though, and take a look at normal matter first. Pakicetus has not been found from deposits of the Tethys Sea but instead from adjacent river and floodplain deposits, which also yield bones of land dwelling mammals. 1993. Mesonychids are a mostly Eocene group that originated in the Paleocene; Mesonyx, from the Middle Eocene of North America, was the first member of the group to be named (Cope published the name in . He wasnt certain, though. The molars were laterally compressed and often blunt and were probably used for shearing meat or crushing bones. You can also shop using Amazon Smile and though you pay nothing more we get a tiny something. In artiodactyls this bone has an immediately recognizable double pulley shape, a characteristic mesonychids did not share. Mesonychid dentition consisted of molars modified to generate vertical shear, thin blade-like lower molars, and carnassial notches, but no true carnassials. 1995. Technically speaking, the term "mesonychid" refers specifically only to the members of the family Mesonychidae, such as the species of the genus Mesonyx. Parsimony analysis of total evidence from extinct and extant taxa and the cetacean-artiodactyl question (Mammalia, Ungulata). Cambridge University Press, pp. The long-snouted and otter-like remingtonocetids appeared next, including small forms like the 46-million-year-oldKutchicetus. - ., Zhai, R. J., Gingerich, P. D. & Chen, L. Z. Unlike all modern and possibly all other fossil cetaceans, it had four fully functional, long legs. Terms of Use It uses its long limbs to swim in a 'doggy paddle' style. The manus of Pachyaena gigantea (Mammalia: Mesonychia). Journal of Vertebrate Paleontology 15, 401-430. Over time, the family evolved foot and leg adaptations for faster running, and jaw adaptations for greater bite force. The largest species are considered to have been scavengers. The bones were so numerous that in some fields they were destroyed because they interfered with cultivating the land. The hypothesis that Ambulocetus lived an aquatic life is also supported by evidence from stratigraphy Ambulocetus's fossils were recovered from sediments that probably comprised an ancient estuary and from the isotopes of oxygen in its bones. Comments: The cervical vertebrae were relatively long, compared to those of modern whales; Ambulocetus must have had a flexible neck. By the turn of the 20th century the oldest fossil whales were still represented byBasilosaurusand similar forms likeDorudonandProtocetus, all of which were fully aquaticthere were no fossils to bridge the gap from land to sea. [5], Most paleontologists now doubt that whales are descended from mesonychids, and instead suggest mesonychians are descended from basal ungulates, and that cetaceans are descended from advanced ungulates (Artiodactyla), either deriving from, or sharing a common ancestor with, anthracotheres (the semiaquatic ancestors of hippos). In 2007, Thewissen and other collaborators announced thatIndohyus, a small deer-like mammal belonging to a group of extinct artiodactyls called raoellids, was the closest known relative to whales. As you well know, normal matter here on Earth is, Mesonyx and the other mesonychid mesonychians (mesonychians part IV), Because we all love Paleogene 'ungulates', Five things you didn't know about armadillos. Such muscles are consistent with webbed feet that were used for aquatic locomotion. It was presented as a stumpy-legged, seal-like creature, an animal caught between worlds. The similarity in dentition and skull may be the result of primitive ungulate structures in related groups independently evolving to meet similar needs as predators; some researchers have suggested that the absence of a first toe and a reduced metatarsal are basal features (synapomorphies) indicating that mesonychids, perissodactyls, and artiodactyls are sister groups. Unlike all modern and possibly all other fossil cetaceans, it had four fully functional, long legs. The following airs here in the UK tonight (Thursday 30th June 2011), Channel 4. New morphological evidence for the phylogeny of Artiodactyla, Cetacea, and Mesonychidae. Forgot to say great post! While the limb proportions and hoof-like phalanges indicate cursoriality, the limbs were relatively stout and show that it cannot have been a long-distance pursuit runner. The postcranial skeleton of early Eocene pakicetid cetaceans. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Though these creatures, such as Dimetrodon, looked like reptiles, they were actually the archaic precursors of mammals. A recent study found mesonychians to be basal euungulates most closely related to the "arctocyonids" Mimotricentes, Deuterogonodon and Chriacus. For this reason, scientists had long believed that mesonychids were the direct ancestor of Cetacea, but the discovery of well-preserved hind limbs of archaic cetaceans, as well as more recent phylogenetic analyses now indicate cetaceans are more closely related to hippopotamids and other artiodactyls than they are to mesonychids, and this result is consistent with many molecular studies. You can't stop him!" However, they also found Dissacus to be paraphyletic with respect to other mesonychids, so further study and perhaps some taxonomic revision is needed [Greg Paul's reconstruction of Ankalagon shown in adjacent image]. He had found vertebrae and other fragments while blasting on his property and also sent off a few samples to the Philadelphia society. The current uncertainty may, in part, reflect the fragmentary nature of the remains of some crucial fossil taxa, such as Andrewsarchus. ), Evolution of Tertiary Mammals of North America 1:292-331, "The Mammals that Conquered the Seas; New Fossils and DNA Analyses Elucidate the Remarkable History of Whales", "Relationships of Cetacea (Artiodactyla) Among Mammals: Increased Taxon Sampling Alters Interpretations of Key Fossils and Character Evolution", Mammoths, Sabertooths, and Hominids: 65 Million Years of Mammalian Evolution in Europe, "Mesonychids from Lushi Basin, Henan Province, China", https://en.wikipedia.org/w/index.php?title=Mesonychidae&oldid=1049612098, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 12 October 2021, at 20:41. Its limbs indicate a cursorial lifestyle [Charles Knight's Mesonyx shown below]. Relatively complete remains were described by Geisler & McKenna (2007) and confirm that the first toe was absent and that the first metatarsal was highly reduced: this is also the case in basal perissodactyls, cetaceans and artiodactyls, and it might be a synapomorphy uniting these groups. Journal of Vertebrate Paleontology 26:355-370.
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