Carnassials are paired upper and lower teeth (either molars or premolars and molars) modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. The modification arose separately in several groups of carnivorous mammals. Different pairs of teeth were involved in the separate modifications. In modern Carnivora, the carnassials are the modified fourth upper premolar and the first lower molar. These teeth are also referred to as sectorial teeth. Humans lack carnassial teeth.
Left: Carnassial teeth of [A] bear (Ursus), [B] leopard (Panthera), [C] dog (Canis), [D] badger (Meles), and their respective close ups.
Right: Carnassial teeth of [E] otter (Lutra), [F] raccoon (Procyon), [G] mongoose (Herpestes), [H] weasel (Mustela), and their respective close-ups.
Photos taken at Imperial College London.
Carnassial teeth are modified molars (and in the case of carnivorans premolars) which are adapted to allow for the shearing (rather than tearing) of flesh to permit the more efficient consumption of meat. These modifications are not limited to the members of the order Carnivora, but are seen in a number of different mammal groups. Not all carnivorous mammals, however, developed carnassial teeth. Mesonychids, for example, had no carnassial adaptations, and as a result, the blunt, rounded cusps on its molars had a much more difficult time reducing meat. Likewise, neither members of Oxyclaenidae nor Arctocyonidae had carnassial teeth.
On the other hand, carnivorous marsupials have carnassial teeth. Both the living Tasmanian devil (Sarcophilus harrisii) and the recently extinct Tasmanian wolf (Thylacinus cynocephalus) possessed modified molars to allow for shearing, although the Tasmanian wolf, the larger of the two, had adaptation more similar to the modern dog. The Pleistocene marsupial lion (Thylacoleo carnifex) had massive carnassial molars. A recent study concludes that these teeth produced the strongest bite of any mammal in history. Moreover, these carnassial molars appear to have been used, unlike in any other known mammal, to inflict the killing blow to the prey by severing the spinal cord, crushing the windpipe or severing a major artery. Like these true marsupials, the closely related borhyaenids of South America had three carnassial teeth involving the first three upper molars (M1-M3) and the second through fourth lower molars (m2-m4). In the borhyaenids the upper carnassials appear to have been rotated medially around the anteriorposterior axis of the tooth row in order to maintain tight occlusional contact between the upper and lower shearing teeth.
Creodonts have two or three pairs of carnassial teeth, but only one pair performed the cutting function: either M1/m2 or M2/m3, depending on the family. In Oxyaenidae, it is M1 and m2 that form the carnassials. Among the hyaenodontids it is M2 and m3. Unlike most modern carnivorans, in which the carnassials are the sole shearing teeth, in the creodonts other molars have a subordinate shearing function. The fact that the two lineages developed carnassials from different types of teeth has been used as evidence against the validity of Creodonta as a clade.
Modern carnivorous bats generally lack true carnassial teeth, but the extinct Necromantis had particularly convergent teeth, in particular M1 and M2, which bore expanded heels and broad stylar shelves. These were particularly suited for crushing over an exclusively slicing action.
Though not superficially similar, the triconodont teeth of some early mammals such as eutriconodonts are thought to have had a function similar to those of carnassials, sharing a similar shearing function. Eutriconodonts possess several speciations towards animalivory, and the larger forms such as Repenomamus, Gobiconodon and Jugulator probably fed on vertebrate prey. Similarly the "tooth lips" of clevosaurid sphenodontians such as Clevosaurus are described as "carnassial-like".
In modern carnivorans the carnassial teeth pairs are found on either side of the jaw and are composed of the fourth upper pre-molar and the first lower molar (P4/m1). The location these carnassial pairs is determined primarily by the masseter muscle. In this position, the carnassial teeth benefit from most of the force generated by this mastication muscle, allowing for efficient shearing and cutting of flesh, tendon and muscle.
The scissor-like motion is created by the movement between the carnassial pair when the jaw occludes. The inside of the fourth upper pre-molar closely passes by the outer surface of the first lower molar, thus allowing the sharp cusps of the carnassial teeth to slice through meat.
The length and size of the carnassial teeth vary between species, taking into account factors such as:
The shape and size of sectorial teeth of different carnivorous animals vary depending on diet, illustrated by the comparisons of bear (Ursus) carnassials with those of a leopard (Panthera). Bears, being omnivores, have a flattened, more blunt carnassial pair than leopards. This reflects the bear's diet, as the flattened carnassials are useful both in slicing meat and grinding up vegetation, whereas the leopard's sharp carnassial pairs are more adapted for its hypercarnivorous diet. During the Late Pleistocene – early Holocene a now extinct hypercarnivorous wolf ecomorph existed that was similar in size to a large extant gray wolf but with a shorter, broader palate and with large carnassial teeth relative to its overall skull size. This adaptation allowed the megafaunal wolf to predate and scavenge on Pleistocene megafauna.
Anachlysictis gracilis is an extinct carnivorous mammal belonging to the group Sparassodonta, which were metatherians (a group including marsupials and their close relatives) that inhabited South America during the Cenozoic. Unlike other remains assigned to the family Thylacosmilidae (a group of metatherian predators equipped with "saber teeth") that had been found previously, Anachlysictis is the first record of such borhyaenoids in northern South America, and also most primitive and ancient in the family (in fact, is the first confirmed record that did not belong to the genus Thylacosmilus, until the official publication of Patagosmilus in 2010). This species was found in the Villavieja Formation in the area of La Venta in Colombia, a famous fossil deposit in the Middle Miocene (Laventan; 13.8-11.8 million years ago), based on fragments that include a front portion of the lower jaw, with an incipient molar tooth and a piece of carnassial from the front of the maxilla.Asiatic linsang
The Asiatic linsang (Prionodon) is a genus comprising two species native to Southeast Asia: the banded linsang (Prionodon linsang) and the spotted linsang (Prionodon pardicolor). Prionodon is considered a sister taxon of the Felidae.Beringian wolf
The Beringian wolf is an extinct type of wolf (Canis lupus) that lived during the Ice Age. It inhabited what is now modern-day Alaska, Yukon, and northern Wyoming. Some of these wolves survived well into the Holocene. The Beringian wolf is an ecomorph of the gray wolf and has been comprehensively studied using a range of scientific techniques, yielding new information on the prey species and feeding behavior of prehistoric wolves. It has been determined that these wolves are morphologically distinct from modern North American wolves and genetically basal to most modern and extinct wolves. The Beringian wolf has not been assigned a subspecies classification and its relationship with the extinct European cave wolf (Canis lupus spelaeus) is not clear.
The Beringian wolf was similar in size to the modern Yukon wolf (Canis lupus pambasileus) and other Late Pleistocene gray wolves but more robust and with stronger jaws and teeth, a broader palate, and larger carnassial teeth relative to its skull size. In comparison with the Beringian wolf, the more southerly occurring dire wolf (Canis dirus) was the same size but heavier and with a more robust skull and dentition. The unique adaptation of the skull and dentition of the Beringian wolf allowed it to produce relatively large bite forces, grapple with large struggling prey, and therefore made predation and scavenging on Pleistocene megafauna possible. The Beringian wolf preyed most often on horse and steppe bison, and also on caribou, mammoth, and woodland muskox.
At the close of the Ice Age, with the loss of cold and dry conditions and the extinction of much of its prey, the Beringian wolf became extinct. The extinction of its prey has been attributed to the impact of climate change, competition with other species, including humans, or a combination of both factors. Local genetic populations were replaced by others from within the same species or of the same genus. Of the North American wolves, only the ancestor of the modern North American gray wolf survived. The remains of ancient wolves with similar skulls and dentition have been found in western Beringia (north-east Siberia). In 2016 a study showed that some of the wolves now living in remote corners of China and Mongolia share a common maternal ancestor with one 28,000-year-old eastern Beringian wolf specimen.Canidae
The biological family Canidae
(from Latin, canis, “dog”) is a lineage of carnivorans that includes domestic dogs, wolves, coyotes, foxes, jackals, dingoes, and many other extant and extinct dog-like mammals. A member of this family is called a canid (, ).The cat-like feliformia and dog-like caniforms emerged within the Carnivoramorpha 43 million years before present. The caniforms included the fox-like genus Leptocyon whose various species existed from 34 million years ago (Mya) before branching 11.9 Mya into Vulpi (foxes) and Canidae (canines).Canids are found on all continents except Antarctica, having arrived independently or accompanied human beings over extended periods of time. Canids vary in size from the 2-m-long (6 ft 7 in) gray wolf to the 24-cm-long (9.4 in) fennec fox. The body forms of canids are similar, typically having long muzzles, upright ears, teeth adapted for cracking bones and slicing flesh, long legs, and bushy tails. They are mostly social animals, living together in family units or small groups and behaving co-operatively. Typically, only the dominant pair in a group breeds, and a litter of young is reared annually in an underground den. Canids communicate by scent signals and vocalizations. One canid, the domestic dog, long ago entered into a partnership with humans and today remains one of the most widely kept domestic animals.Canis
Canis is a genus of the Canidae containing multiple extant species, such as wolves, coyotes, jackals, dingoes, and dogs. Species of this genus are distinguished by their moderate to large size, their massive, well-developed skulls and dentition, long legs, and comparatively short ears and tails.Carnivora
Carnivora (; from Latin carō (stem carn-) "flesh" and vorāre "to devour") is a diverse scrotiferan order that includes over 280 species of placental mammals. Its members are formally referred to as carnivorans, whereas the word "carnivore" (often popularly applied to members of this group) can refer to any meat-eating organism. Carnivorans are the most diverse in size of any mammalian order, ranging from the least weasel (Mustela nivalis), at as little as 25 g (0.88 oz) and 11 cm (4.3 in), to the polar bear (Ursus maritimus), which can weigh up to 1,000 kg (2,200 lb), to the southern elephant seal (Mirounga leonina), whose adult males weigh up to 5,000 kg (11,000 lb) and measure up to 6.7 m (22 ft) in length.
Carnivorans have teeth and claws adapted for catching and eating other animals. Many hunt in packs and are social animals, giving them an advantage over larger prey. Some carnivorans, such as cats and pinnipeds, depend entirely on meat for their nutrition. Others, such as raccoons and bears, are more omnivorous, depending on the habitat. The giant panda is largely a herbivore, but also feeds on fish, eggs and insects. The polar bear subsists mainly on seals.
Carnivorans are split into two suborders: Feliformia ("catlike") and Caniformia ("doglike").Claudia Roth (paleobiologist)
Claudia Roth is a research scientist in the field of paleobiology. She is associated with Institute of Sciences of Evolution, Lille University of Science and Technology, Villeneuve-d'Ascq, France and the Institute of Geosciences-Palaeontology, University of Mainz, Germany. Roth and Legendre have both contributed as a team to the Paleobiology Database, an online closed scientific database.Creodonta
Creodonta is an extinct, potentially polyphyletic order of carnivorous mammals that lived from the Paleocene to the Miocene epochs. Because they both possess carnassial teeth, creodonts and carnivorans were once thought to have shared a common ancestor, but given that different teeth are involved in making up the carnassials (both between creodonts and carnivorans and between the main groups of creodonts), this appears to be a case of evolutionary convergence. Carnassials are also known in other mammal clades, such as in the extinct bat Necromantis.
Two distinct families were historically thought to compose the order: Oxyaenidae and Hyaenodontidae. They may both represent separate orders of fossil mammals related to carnivoramorphs or are descended from more basal taxa.
Creodonts had an extensive range, both geographically and temporally. They are known from the late Paleocene through the late Oligocene in North America, the early Eocene through late Oligocene in Europe, from the early Eocene through late Miocene in Asia, and from the Paleocene to the late Miocene in Africa.Creodonts were the first large, obviously carnivorous mammals with the radiation of the oxyaenids in the late Paleocene. During the Paleogene, they were the most abundant form of terrestrial carnivore in the Old World. In Oligocene Africa, they were the dominant predatory group. They competed with the Mesonychids and the Entelodonts and ultimately outlasted them by the start of the Oligocene and by the middle of the Miocene respectively, but lost ground to the carnivorans. The last genus became extinct 11.1 million years ago, and carnivorans now occupy their ecological niches.Darkwing (novel)
Darkwing (known as Dusk in the United Kingdom) is a young adult fantasy novel by Canadian author Kenneth Oppel. It is the prequel and fourth book of the Silverwing series, and takes place 65 million years before the events of the first book. It describes the origins of the war between the birds and the beasts.Dire wolf
The dire wolf (Canis dirus, "fearsome dog") is an extinct species of the genus Canis. It is one of the most famous prehistoric carnivores in North America, along with its extinct competitor, the sabre-toothed cat Smilodon fatalis. The dire wolf lived in the Americas during the Late Pleistocene and Early Holocene epochs (125,000–9,440 years ago). The species was named in 1858, four years after the first specimen had been found. Two subspecies are recognized: Canis dirus guildayi and Canis dirus dirus. The dire wolf probably evolved from Armbruster's wolf (Canis armbrusteri) in North America. The largest collection of its fossils has been obtained from the Rancho La Brea Tar Pits in Los Angeles.
Dire wolf remains have been found across a broad range of habitats including the plains, grasslands, and some forested mountain areas of North America, and in the arid savannah of South America. The sites range in elevation from sea level to 2,255 meters (7,400 ft). Dire wolf fossils have rarely been found north of 42°N latitude; there have been only five unconfirmed reports above this latitude. This range restriction is thought to be due to temperature, prey, or habitat limitations imposed by proximity to the Laurentide and Cordilleran ice sheets that existed at the time.
The dire wolf was about the same size as the largest modern gray wolves (Canis lupus): the Yukon wolf and the northwestern wolf. C. d. guildayi weighed on average 60 kilograms (132 lb) and C. d. dirus was on average 68 kg (150 lb). Its skull and dentition matched those of C. lupus, but its teeth were larger with greater shearing ability, and its bite force at the canine tooth was the strongest of any known Canis species. These characteristics are thought to be adaptations for preying on Late Pleistocene megaherbivores, and in North America its prey are known to have included horses, ground sloths, mastodons, bison, and camels. As with other large Canis hypercarnivores today, the dire wolf is thought to have been a pack hunter. Its extinction occurred during the Quaternary extinction event along with most of the American megafauna of the time, including a number of other carnivores, that occurred soon after the appearance of humans in the New World. Its reliance on megaherbivores has been proposed as the cause of its extinction, along with climate change and competition with other species, but the cause remains controversial. Dire wolves lived as recently as 9,440 years ago, according to dated remains.Hyaenodontidae
Hyaenodontidae ("hyena teeth") is a family of extinct predatory mammals, and is the type family of the extinct mammalian order Hyaenodonta. Hyaenodontids were important mammalian predators that arose during the late Paleocene and persisted well into the Miocene. They were considerably more widespread and successful than the oxyaenids, the other clade historically considered part of Creodonta.Megafaunal wolf
The megafaunal wolf (Canis cf. lupus) was a Late Pleistocene – early Holocene hypercarnivore similar in size to a large extant gray wolf. It had a shorter, broader palate with large carnassial teeth relative to its overall skull size. This adaptation allowed it to prey and scavenge on Pleistocene megafauna. Such an adaption is an example of phenotypic plasticity. It was once distributed across the northern Holarctic.Megantereon
Megantereon was a genus of prehistoric machairodontine saber-toothed cat that lived in North America, Eurasia, and Africa. It may have been the ancestor of Smilodon.Miacidae
Miacids are extinct primitive carnivoramorphans within the family Miacidae that lived during the Paleocene and Eocene epochs, about 62–34 million years ago. Miacids existed for approximately 28 million years.Miacids are thought to have evolved into the modern carnivorous mammals of the order Carnivora. They were small carnivores, superficially marten-like or civet-like with long, little bodies and long tails. Some species were arboreal, while others lived on the ground.They probably fed on invertebrates, lizards, birds, and smaller mammals like shrews and opossums. Their teeth and skulls show that the miacids were less developed than modern carnivorans. They had carnivoran-type carnassials, but lacked fully ossified auditory bullae (rounded protrusions).Pleistocene coyote
The Pleistocene coyote (Canis latrans orcutti), also known as the Ice Age coyote, is an extinct subspecies of coyote that lived in western North America during the Late Pleistocene era. Most remains of the subspecies were found in southern California, though at least one was discovered in Idaho. It was part of a carnivore guild that included other canids like foxes, gray wolves, and dire wolves.Compared to their modern Holocene counterparts, Pleistocene coyotes were larger and more robust, weighing 39–46 lb (18–21 kg), likely in response to larger competitors and prey rather than Bergmann's rule. Their skulls and jaws were significantly thicker and deeper than in modern coyotes, with a shorter and broader rostrum and wider carnassial (denoting the large upper premolar and lower molar teeth of a carnivore, adapted for shearing flesh) teeth. These adaptions allowed it to cope with higher levels of stress, when it killed larger prey, compared to modern coyotes. Pleistocene coyotes were also likely more specialized carnivores than their descendants, as their teeth were more adapted to shearing meat, showing fewer grinding surfaces which were better suited for processing vegetation. The lower jaw was also deeper, and the molars showed more signs of wear and breakage than modern populations, thus indicating that the animals consumed more bone than today. Behaviorally, it is likely to have been more social than the modern coyote, as its remains are the third most common in the La Brea Tar Pits, after dire wolves and sabre-toothed cats, both thought to be gregarious species.Their reduction in size occurred within 1,000 years of the occurrence of the Quaternary extinction event, when the climate changed and the majority of their larger prey became extinct. Furthermore, Pleistocene coyotes were unable to successfully exploit the big game hunting niche left vacant after the extinction of the dire wolf, as that gap was rapidly filled by gray wolves. These gray wolves are likely to have actively killed off the larger-bodied coyotes, with natural selection favoring the modern gracile morph. Human predation on the Pleistocene coyote's dwindling prey base may have also impacted the animal's change in morphology.Priscileo
Priscileo ("Ancient Lion") is the basal-most genus of marsupial lions. Fossils of this genus have been found in Oligocene and Miocene strata of South Australia and Queensland. It was about the size of a possum and was less powerful than the other marsupial lions. The two species have crushing molar teeth (as in omnivorous kangaroos) as well as carnassial blades (large, flesh cutting teeth derived from the first lower molar and last upper molar). The Early Miocene species of P. roskellyae may have been an arboreal species.
Priscileo pitikantensis lived in Australia about 25 million years ago from the late Oligocene to middle Miocene and was approximately the size of a cat.
It is known only from a few post cranial bones found at Lake Pitakanta in northeastern south Australia and a poorly preserved maxillary fragment. To date P. pitikantensis is the oldest and most primitive of the Thylacoleonidae known.Serge Legendre
Serge Legendre is a research scientist in the field of paleobiology with the Institute of Paleoenvironment & Paleobiosphere, University of Lyon and Editor-in-Chief of Geobios, a scientific journal published bi-monthly.Thylacoleo
Thylacoleo ("pouch lion") is an extinct genus of carnivorous marsupials that lived in Australia from the late Pliocene to the late Pleistocene (2 million to 46 thousand years ago). Some of these "marsupial lions" were the largest mammalian predators in Australia of that time, with Thylacoleo carnifex approaching the weight of a small lion. The estimated average weight for the species ranges from 101 to 130 kg.Viverravidae
Viverravidae is an extinct family within the superfamily Miacoidea. They are related to carnivorans, and lived from the early Palaeocene to the Eocene.
In viverravids, the number of molars is reduced to two and the skull is elongated. Viverravidae is a monophyletic family, a plesion-group. They are not thought to be ancestral to any extant carnivorans.The viverravids were thought to be the earliest carnivorans: they first appeared in the Paleocene of North America about 60 million years ago. One author proposed that they should be placed outside the order Carnivora based on cranial morphology.Wang and Tedford propose that they arose in North America 65-60 million years ago, spread to Asia then later to Europe, and were the first carnivorans and possessed the first true pair of carnassial teeth.