Mesonychids first appeared in the early Paleocene, went into a sharp decline at the end of the Eocene, and died out entirely when the last genus, Mongolestes, became extinct in the early Oligocene. Good remains of P. ossifraga show that it was a large animal of 60-70 kg [skull of Sinonyx jiashanensis from Late Paleocene China shown below, from Zhou et al. :). Locomotion: (ed) The Phylogeny and Classification of the Tetrapods, Volume 2: Mammals. They were major predators in the Northern Hemisphere from shortly after the demise of the dinosaurs until about 30 million years ago, and the shape of their teeth resembled those of whales likeProtocetus. Goodbye Tet Zoo ver 2. Isotopic records from early whales and sea cows: contrasting patterns of ecological transition. [5]. This page was last updated at 2022-07-17 03:07 UTC. 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 indicates that cetaceans are more closely related to hippopotamids and other artiodactyls than they are to mesonychids, and this result is consistent with many molecular studies. 1988, the feature they thought united Andrewsarchus and Cetacea (they include a cladogram with a list of synapomorphies for each node (or at least for many)) was arrangement of incisors in a fore-and-aft line: early whales (and I'm not sure how many really early Cetaceans were known when they wrote) have all three incisors in a line, Andrewsarchus has M3 behind rather than beside M2, which they saw as an intermediate step towards the Cetacean condition. 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. While later mesonychids evolved a suite of limb adaptations for running similar to those in both wolves and deer, their legs remained comparatively thick. Origins of underwater hearing in whales. Pakicetus had a long snout; a typical complement of teeth that included incisors, canines, premolars, and molars; a distinct and flexible neck; and a very long and robust tail. Who says that the solution adopted by carnivorans, dasyurids, sparassodonts and "creodonts" - basal cynodont dentition + carnassials - is the best or the only solution for processing meat? Archaic ungulates ("Condylarthra"). Originally mistaken for dinosaur fossils, whale bones uncovered in recent years have told us much about the behemoth sea creatures. mesonychids limbs and tail. Even better, two jaw fragments showed that the teeth ofPakicetuswere very similar to those of mesonychids. queen of the south why did javier kill tony. Copyright 2010. This conflict makes his soul a battlefield, where the forces that wish this reconciliation fight those that do not and reject the alternative solutions they offer. 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? For previous articles on Paleogene mammals see And for other stuff on neat and obscure fossil mammals see Archibald, J. D. 1998. 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 . In walking, its high rump and low withers would give it somewhat the figure of a huge rabbit. Mesonychids limbs and tail description. [5] They would have resembled no group of living animals. Throughout the 1990s, the skeletons of more or less aquatically adapted ancient whales, or archaeocetes, were discovered at a dizzying pace. 201-234. They were also most diverse in Asia where they occur in all major Paleocene faunas. 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. Author: In Janis, C. M., Scott, K. M. & Jacobs, L. L. (eds) Evolution of Tertiary Mammals of North America. Mammals diversified in the shadow of the great archosaurs, and they remained fairly small and secretive until the non-avian dinosaurs were wiped out by a mass extinction 65 million years ago. But, because they are mammals, we know that they must have evolved from land-dwelling ancestors. Phylogenetic and morphometric reassessment of the dental evidence for a mesonychian and cetacean clade. In some localities, multiple species or genera coexisted in different ecological niches. Gingerich, P.D. Technically speaking, the term "mesonychid" refers specifically only to the members of the family Mesonychidae, such as the species of the genus Mesonyx. ScienceBlogs is a registered trademark of Science 2.0, a science media nonprofit operating under Section 501(c)(3) of the Internal Revenue Code. 1995]. Systematic Biology 48, 455-490. Mesonychid dentition consisted of molars modified to generate vertical shear, thin blade-like lower molars, and carnassial notches, but no true carnassials. Given that both Creagh and Bry said they had seen intact vertebral columns in excess of 100 feet in length, the living creature must have been one of the largest vertebrates to have ever lived. About 375 million years ago, the first tetrapodsvertebrates with arms and legspushed themselves out of the swamps and began to live on land. Which were more reliable, teeth or genes? The eyes of Pakicetus faced to the side and slightly upward. [4] [5] Like other mesonychids, the toes ended in small hooves. In the meantime, scientists speculated about what the ancestors of whales might have been like. Hb``a``Z b. A number of other mesonychian taxa have conventionally been included within Mesonychidae. > to be up to snuff, compared to modern carnivorans, their 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. & Rose, K. D. 1995. (1995) found Mongolonyx and Mongolestes (both from Eocene Asia) to be part of this clade as well. - . Learn Mesonychid facts for kids. 1846. 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. They are not closely related to any living mammals. Harpagolestes, known from several North American and Asian species, is a notably robust-skulled mesonychid with proportionally large canines, a deep lower jaw, and relatively broad post-canine teeth that are often heavily worn [skull of H. uintensis shown here, from Szalay & Gould (1966)]. But while preparing the sixth edition, he decided to include a small note aboutBasilosaurus. It had a long muzzle, teeth that were very similar to later archaeocetes, a reduced . 2023 Smithsonian Magazine Skulls and teeth have similar features to early whales, and the family was long thought to be the ancestors of cetaceans. At last, whales could be firmly rooted in the mammal evolutionary tree. Nearly all mesonychids are, on average, larger than most of the Paleocene and Eocene creodonts and miacoid carnivorans. 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. It had slender jaws and narrow teeth, and on account of these has sometimes been suggested to be piscivorous. Huxley thought thatBasilosaurusat least represented the type of animal that linked whales to their terrestrial ancestors. These "wolves on hooves" are an extinct order of carnivorous mammals, closely related to artiodactyls.. Mesonychids first appeared in the early Palaeocene with the genus Dissacus.They went in decline at the end of the Eocene, and became extinct in the early Oligocene. Thus it is unclear if it was an active predator or if instead it ambushed unsuspecting prey that wandered too closely. > given that mesonychian meat processing really didn't seem 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). The phylogeny of the ungulates. Image credit: NASA / Apollo 17. 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]. Not to toot my own horn, but I found this article very inspiring. | READ MORE. 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. 2007. Thewissen, J.G.M., Williams, E.M., Roe, L.J., and Hussain, S.T.. 2001. Many of the skeletons of the earliest archaeocetes were extremely fragmentary, and they were often missing the bones of the ankle and foot. 1999. mesonychids limbs and tail. Since other predators, such as creodonts and Carnivora, were either rare or absent in these animal communities, mesonychids most likely dominated the large predator niche in the Paleocene of eastern Asia. Typified by hooves and sometimes by horns or antlers, today these creatures fill most of the existing niches for large herbivores all over the world. They would have resembled no group of living animals. You're welcome. malleus, incus, stapes), which transmitted the sound to the organ of hearing. Well-developed puncturing cusps (incisors) and serrated cheek teeth indicate that Pakicetus ate flesh, most likely that of fish. It was thick and highly mineralized, just like the bone in whale ears. 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. It was a wolf-like animal, not the slick, seal-like animal that had originally been envisioned. Huxley replied that there could be little doubt thatBasilosaurusprovided clues as to the ancestry of whales. Dissacus was a jackal- or wolf-sized mesonychid that occurred throughout the Northern Hemisphere during the Late Paleocene (more than ten species have been named). Bulletin of the American Museum of Natural History 132, 127-174. (1995); and to Cete by Archibald (1998);[7] and to Mesonychia by Carroll (1988), Zhou et al. It was assigned to Creodonta by Cope (1880); to Creodonta by Cope (1889); to Carnivora by Peterson (1919); to Mesonychia by Carroll (1988) and Zhou et al. The sound passage via the external ear of Pakicetus was intact and was similar to that of other mammals. Pakicetus had a long snout; a typical complement of teeth that included incisors, canines, premolars, and molars; a distinct and flexible neck; and a very long and robust tail. The phylogenetic position of cetaceans: further combined data analyses, comparisons with the stratigraphic record and a discussion of character optimization. > predators might have some credit after all. The history of life: looking at the patterns, Pacing, diversity, complexity, and trends, Alignment with the Next Generation Science Standards, Information on controversies in the public arena relating to evolution. Thus the thickened bulla of Pakicetus is interpreted as a specialization for hearing underwater sound. Basilosaurus is characterized by extremely elongate vertebrae (three times as long as those in most other basilosaurids, relative to vertebral width), a very high degree of flexibility in the vertebral column, a high number of vertebrae, and an incredibly elongate body form in general. The last four articles that have appeared here were all scheduled to publish in my absence. Looking back at it now, that very first ver 2 post is rather odd. One genus, Dissacus, had successfully spread to Europe and North America by the early Paleocene. 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 large tail of Pakicetus is possibly a specialization for aquatic locomotion, although exactly how is unclear. Its limbs indicate a cursorial lifestyle [Charles Knight's Mesonyx shown below]. Often called wolves with hooves, mesonychids were medium- to large-sized predators with long, toothy snouts and toes tipped with hooves rather than sharp claws. Nearly all mesonychids are, on average, larger than most of the Paleocene and Eocene creodonts and miacoid carnivorans. (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). 2001. 2008. Asiatic Mesonychidae (Mammalia, Condylarthra). mesonychids limbs and tailokinawan sweet potato tempura recipe. He could not imagine that early cetaceans used their limbs to swim and then switched to tail-only propulsion at some later point. 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. 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. Then, in 2001, J.G.M. Ambulocetus's skull was quite cetacean (Novacek 1994). Mesonyx species have been estimated as 1.25-1.5m (4.5-5 ft.) long in life, not including the tail. The largest hunters probably competed with biggest hyenodonts, but some may survived occupying more specialized niches. 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]). whale or land mammal? The American Phrenological Journal and Miscellany, Vol. 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. 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. Mesonychidae Mesonychids have often been reconstructed as resembling wolves albeit superficially, but they would have appeared very different in life. Journal of Vertebrate Paleontology 15, 855-859. [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. Were there really any distance runners in the paelogene? In artiodactyls this bone has an immediately recognizable double pulley shape, a characteristic mesonychids did not share. & Gingerich, P. D. 1992. 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. %PDF-1.2 % 1998. Adapted fromWritten in Stone: Evolution, the Fossil Record, and Our Place in Nature, by Brian Switek. Pakicetus had a dense and thickened auditory bulla, which is a characteristic of all cetaceans. It had a long muzzle, teeth that were very similar to later archaeocetes, a reduced . Sensory Abilities: One branch of the ungulate family, called the mesonychids, were predators. So, in the sheep figure, anterior is to the left and above. There is a grain of truth in the cat versus dog question. There was no straight-line march of terrestrial mammals leading up to fully aquatic whales, but an evolutionary riot of amphibious cetaceans that walked and swam along rivers, estuaries and the coasts of prehistoric Asia. Your Privacy Rights American Museum Novitates 3344, 1-53. The link between other ungulates and whales is thought to be mesonychids, extinct four-legged mammals that sometimes feasted on fish at river edges. Dissacus was a jackal-sized predator that has been found all over the Northern Hemisphere, but species of a closely related or identical genus, Ankalagon, from the early to middle Paleocene of New Mexico, were far larger, growing to the size of a bear. ("8v`HaU The thickened part of the auditory bulla was suspended from the skull, allowing it to vibrate in response to sound waves propagating through the skull. Based on the orientations of the wear facets, Pakicetus sheared its prey into smaller pieces before swallowing. These forms, likeRodhocetus, were nearly entirely aquatic, and some later protocetids, likeProtocetusandGeorgiacetus, were almost certainly living their entire lives in the sea. Please make a tax-deductible donation if you value independent science communication, collaboration, participation, and open access. It's on the blood-feeding behaviour of, So sorry for the very short notice. LikeBasilosaurus, though,Squalodonwas fully aquatic and provided few clues as to the specific stock from which whales arose. The following airs here in the UK tonight (Thursday 30th June 2011), Channel 4. These ancestral creatures were stranger than anyone ever expected. He wasnt certain, though. Mesonychids varied in size; some species were as small as a fox, others as large as a horse. Contributions are fully tax-deductible. Dissacus was a jackal-sized predator that has been found all over the Northern Hemisphere,[3] but species of a closely related or identical genus, Ankalagon, from the early to middle Paleocene of New Mexico, were far larger, growing to the size of a bear. Archaeocetes had a double-pulley astragalus, confirming that cetaceans had evolved from artiodactyls. Together they illustrate how the entire transition took place. The jaw contained teeth that differed in size and shape, a characteristic of mammals but not most reptiles. These hoofed predators came in diverse forms, from tiny to horse-sized. The fossil record was so sparse that no definite determination could be made, but in a thought experiment included inOn the Origin of Species, Darwin speculated about how natural selection might create a whale-like creature over time: In North America the black bear was seen by [the explorer Samuel] Hearne swimming for hours with widely open mouth, thus catching, like a whale, insects in the water. Summary written by Jonathan Geisler and Melody Ho. Accept Cookies, Osteopathic Manipulative Medicine Research. Geisler & McKenna (2007) found Ankalagon to be nested within a clade of Dissacus species, suggesting that it doesn't deserve generic separation after all. Nature 361:444-445. & McKenna, M. C. 2007. While later mesonychids evolved a suite of limb adaptations for running similar to those in both wolves and deer, their legs remained comparatively thick. 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. Such muscles are consistent with webbed feet that were used for aquatic locomotion. Based on the skull sizes of Pakicetus specimens, and to a lesser extent on composite skeletons, species of Pakicetus are thought to have been 1 to 2 meters in length (4 to 5 feet). [4] In contrast to arctocyonids, the mesonychids had only four digits furnished with hooves supported by narrow fissured end phalanges. They looked as if they would have been more at home on land than in the water, and they probably got around lakes and rivers by doing the doggie paddle. Mesonychids fared very poorly at the close of the Eocene epoch, with only one genus, Mongolestes,[6] surviving into the Early Oligocene epoch. Place the mesonychid strip (#2) at about the 55 mya level on your timeline (mesonychids lived from 58-34 mya). As in most land mammals, the nose was situated at the tip of the snout. The long-snouted and otter-like remingtonocetids appeared next, including small forms like the 46-million-year-oldKutchicetus. Various genera and species coexisted in some locations, as hunters and omnivores or scavengers. Journal of Vertebrate Paleontolgy 29:1289-1299. 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? When the fossil data was combined with genetic data by Jonathan Geisler and Jennifer Theodor in 2009, a new whale family tree came to light. Harpagolestes and Mesonyx appear to be sister-taxa, and the most derived of mesonychids (O'Leary & Geisler 1999, Geisler 2001, Thewissen et al. A few years later, a scientist handling a different specimen with his colleagues pulled out a bone from the skull, dropped it, and it shattered on the floor. 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. 2_%v>sr&u ! mesonychids limbs and tailbiblical counseling raleigh, nc | Critics took it to mean he was proposing that bears were direct ancestors of whales. 1998. (1995), Geisler and McKenna (2007) and Spaulding et al. We use cookies to see how our website is performing. They may not have included hypercarnivores (comparable to felids); their teeth were not as effective at cutting meat as later groups of large mammalian predators. 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. 2009. You can't stop him!" As a result, the back was relatively stiff, and Pachyaena would have been a stiff-legged runner, its gait perhaps more resembling that of a horse or antelope than that of a carnivoran. - . Clarendon Press (Oxford), pp. In Asia, the record of their history suggests they grew gradually larger and more predatory over time, then shifted to scavenging and bone-crushing lifestyles before the group became extinct. What springs to mind when you think of a whale? Forgot to say great post! Mesonychidae (meaning "middle claws") is an extinct family of small to large-sized omnivorous-carnivorous mammals. Some genera may need revision to clarify the actual number of species or remove ambiguity about genera (such as Dissacus and Ankalagon). 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. References Consulted: 8. (2009).[8]. At this time, Pakistan was on the edge of a great shallow seaway called the Tethys Sea, extending from the present-day Mediterranean to India. The current uncertainty may, in part, reflect the fragmentary nature of the remains of some crucial fossil taxa, such as Andrewsarchus. One genus, Dissacus, had successfully spread to Europe and North America by the early Paleocene. 24 Jun . The fact that it was found in freshwater deposits and did not have specializations of the inner ear for underwater hearing showed that it was still very early in the aquatic transition, and Gingerich and Russell thought ofPakicetusas an amphibious intermediate stage in the transition of whales from land to sea, though they added the caveat that Postcranial remains [bones other than the skull] will provide the best test of this hypothesis. The scientists had every reason to be cautious, but the fact that a transitional whale had been found was so stupendous that full-body reconstructions ofPakicetusappeared in books, magazines and on television. The cervical vertebrae were relatively long, compared to those of modern whales; Ambulocetus must have had a flexible neck. The anatomist William Henry Flower pointed out that seals and sea lions use their limbs to propel themselves through the water while whales lost their hind limbs and swam by oscillations of their tail. Since other predators, such as creodonts and Carnivora, were either rare or absent in these animal communities, mesonychids most likely dominated the large predator niche in the Paleocene of eastern Asia. 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. Mesonychians were long considered to be creodonts, but have now been removed from that order and placed in three families (Mesonychidae, Hapalodectidae, and Triisodontidae), either within their own order, Mesonychia, or within the order Condylarthra as part of the cohort or superorder Laurasiatheria. Its skeleton bears no evidence that it could move fast in the water. Postcranial skeleton of the early Eocene mesonychid Pachyaena (Mammalia: Mesonychia). Recently scientists determined which group of prehistoric artiodactyls gave rise to whales. 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. 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. But, long ago, not all ungulates were herbivores. While analyzing the relationships of ancient meat-eating mammals in 1966, however, the evolutionary biologist Leigh Van Valen was struck by the similarities between an extinct group of land-dwelling carnivores called mesonychids and the earliest known whales. 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. The cervical vertebrae were relatively long, compared to those of modern whales; Ambulocetus must have had a flexible neck. In the space of just three decades, a flood of new fossils has filled in the gaps in our knowledge to turn the origin of whales into one of the best-documented examples of large-scale evolutionary change in the fossil record. Yep, you are correct - a stupid error that I will now go correct, thanks. 49 million years old. Journal of Vertebrate Paleontology 15, 387-400. Limbs and tail: Description; Did it swim? Update now. The order is sometimes referred to by its older name Acreodi. Vague similarities with other long, I read something annoying; always a good impetus for a blog entry. . Now the tide has turned. > traditional characterisation as archaic,'inferior' Since other carnivores such as the creodonts and Carnivora were either rare or absent in these animal communities, mesonychids most likely dominated the large predator niche in the Paleocene of Asia. Unlike all modern and possibly all other fossil cetaceans, it had four fully functional, long legs. mesonychids limbs and tail. The bulla was in turn connected to the chain of middle ear bones (i.e. These later mesonychids had hooves, one on each toe, with four toes on each foot. Van Valen hypothesized that some mesonychids may have been marsh dwellers, mollusk eaters that caught an occasional fish, the broadened phalanges [finger and toe bones] aiding them on damp surfaces. A population of mesonychids in a marshy habitat might have been enticed into the water by seafood. On this Wikipedia the language links are at the top of the page across from the article title. Kids Start Forgetting Early Childhood Around Age 7, Archaeologists Discover Wooden Spikes Described by Julius Caesar, 5,000-Year-Old Tavern With Food Still Inside Discovered in Iraq, Artificial Sweetener Tied to Risk of Heart Attack and Stroke, Study Finds, The Surprisingly Scientific Roots of Monkey Bars. To see new stuff (from July 2011 to present), click here. 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. Although they share a common ancestor, the Carnivora are split into two quite well-defined groups that are broadly dog-like, the . There were bone-cracking scavengers, small jackal or fox-like generalists, large wolf-like hunters, and so on. Why did the largest fossil reptile that ever lived have mammal-like teeth? There was rapturous applause, swooning, the delight of millions. Our inability to find limbs and tails was so frustrating that in 2000 we moved from this area, where fossil-bearing strata are beautifully exposed, to the west side of the Sulaiman Range in Balochistan Province. Thewissen, J.G.M and Hussain, S.T. Even in so extreme a case as this, if the supply of insects were constant, and if better adapted competitors did not already exist in the country, I can see no difficulty in a race of bears being rendered, by natural selection, more and more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale.