Nimravidae Temporal range: | |
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Hoplophoneus mentalis | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Carnivora |
Suborder: | Feliformia |
Superfamily: | † Nimravoidea |
Family: | † Nimravidae Cope, 1880 |
Genera [1] | |
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Nimravidae is an extinct family of carnivorans, sometimes known as false saber-toothed cats, whose fossils are found in North America and Eurasia. Not considered to belong to the true cats (family Felidae), the nimravids are generally considered closely related and classified as a distinct family in the suborder Feliformia. Fossils have been dated from the Middle Eocene through the Late Miocene epochs (Bartonian through Tortonian stages, 40.4–7.2 million years ago), spanning about 33.2 million years. [3]
The barbourofelids, which were formerly classified as a subfamily of the Nimravidae, were reassigned to their own distinct family Barbourofelidae in 2004. [4] However, some recent (2020) studies suggest the barbourofelids are a branch of the nimravids, suggesting that this debate might not be settled yet. [5]
Most nimravids had muscular, low-slung, cat-like bodies, with shorter legs and tails than are typical of cats. Unlike extant Feliformia, the nimravids had a different bone structure in the small bones of the ear. The middle ear of true cats is housed in an external structure called an auditory bulla, which is separated by a septum into two chambers. Nimravid remains show ossified bullae with no septum, or no trace at all of the entire bulla. They are assumed to have had a cartilaginous housing of the ear mechanism. [6] Nimravid feet were short, indicating they walked in a plantigrade or semiplantigrade posture, i.e., on the flat of the feet rather than the toes, like modern cats. [7]
Although some nimravids physically resembled the saber-toothed cats, such as Smilodon , they were not closely related, [8] but evolved a similar form through parallel evolution. They possessed synapomorphies with the barbourofelids in the cranium, mandible, dentition, and postcranium. [9] They also had a downward-projecting flange on the front of the mandible as long as the canine teeth, a feature which also convergently evolved in the saber-toothed sparassodont Thylacosmilus .
The ancestors of nimravids and cats diverged from a common ancestor soon after the Caniformia–Feliformia split, in the middle Eocene about 50 million years ago (Mya), with a minimum constraint of 43 Mya. Recognizable nimravid fossils date from the late Eocene (37 Mya), from the Chadronian White River Formation at Flagstaff Rim, Wyoming, to the late Miocene (5 Mya). Nimravid diversity appears to have peaked about 28 Mya.
A 2021 study has shown that a sizeable number of species developed feline-like morphologies in addition to saber-toothed taxa. [10]
The family Nimravidae was named by American paleontologist Edward Drinker Cope in 1880, [11] with the type genus as Nimravus. The family was assigned to Fissipedia by Cope (1889); to Caniformia by Flynn and Galiano (1982); to Aeluroidea by Carroll (1988); to Feliformia by Bryant (1991); and to Carnivoramorpha, by Wesley-Hunt and Werdelin (2005). [12]
Nimravids are placed in tribes by some authors to reflect closer relationships between genera within the family. Some nimravids evolved into large, toothed, cat-like forms with massive flattened upper canines and accompanying mandibular flanges. Some had dentition similar to felids, or modern cats, with smaller canines. Others had moderately increased canines in a more intermediate relationship between the saber-toothed cats and felids. The upper canines were not only shorter, but also more conical, than those of the true saber-toothed cats (Machairodontinae). These nimravids are referred to as "false saber-tooths".
Not only did nimravids exhibit diverse dentition, but they also showed the same diversity in size and morphology as cats. Some were leopard-sized, others the size of today's lions and tigers, one had the short face, rounded skull, and smaller canines of the modern cheetah, and one, Nanosmilus , was only the size of a small bobcat.
The Barbourofelids were for a while no longer included in Nimravidae, following elevation to family as sister clade to the true cats (family Felidae). [13] [14] However, several recent studies have returned them to Nimravidae, including as part of Nimravinae. [1] [10]
Tribe | Image | Genus | Species |
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† Dinailurictis (Helbing, 1922) |
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† Dinictis (Leidy, 1854) |
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† Eofelis (Kretzoi, 1938) |
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† Maofelis [15] (Averianov et al., 2016) |
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† Pangurban [2] (Poust et al, 2022) |
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† Pogonodon (Cope, 1880) |
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† Quercylurus (Ginsburg 1979) |
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†Nimravini | † Dinaelurus (Eaton, 1922) |
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† Nimravus (Cope, 1879) |
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†Hoplophoneini | † Hoplophoneus [16] (Cope, 1874) |
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† Nanosmilus (Martin, 1992) |
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The phylogenetic relationships of Nimravidae are shown in the following cladogram: [15] [16] [17]
A 2021 study divides Nimravidae into Hoplophoninae and Nimravinae, the latter including the bulk of species in addition to barbourofelids.
Phylogeny of Nimravidae from the 2022 description of Pangurban: [2]
Nimravidae |
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Nimravids appeared in the middle of the Eocene epoch, about 40 Mya, in North America and Asia. The global climate at this time was warm and wet, but was trending cooler and drier toward the late Eocene. The lush forests of the Eocene were transforming to scrub and open woodland. This climatic trend continued in the Oligocene, and nimravids evidently flourished in this environment. North America and Asia were connected and shared much related fauna. [18] Europe in the Oligocene was more of an archipelago than a continent, though some land bridges must have existed, for nimravids also spread there.
In the Miocene, the fossil record suggests that many animals suited for living in forest or woodland were replaced by grazers suited for grassland. This suggests that much of North America and Asia became dominated by savanna. Nimravids disappeared along with the woodlands, but survived in relictual humid forests in Europe to the late Miocene. When conditions ultimately changed there in the late Miocene, the last nimravids disappeared about 9 Mya. [18]
Felidae is the family of mammals in the order Carnivora colloquially referred to as cats. A member of this family is also called a felid. The term "cat" refers both to felids in general and specifically to the domestic cat.
Proailurus is an extinct felid genus that lived in Europe and Asia approximately 25-30.8 million years ago in the Late Oligocene and Miocene. Fossils have been found in Mongolia, Germany, and Spain.
Pseudaelurus is a prehistoric cat that lived in Europe, Asia and North America in the Miocene between approximately twenty and eight million years ago. It is considered to be a paraphyletic grade ancestral to living felines and pantherines as well as the extinct machairodonts (saber-tooths), and is a successor to Proailurus. It originated from Eurasia and was the first cat to reach North America, when it entered the continent at about 18.5 Ma ending a 'cat-gap' of 7 million years. The slender proportions of the animal, together with its short, viverrid-like legs, suggest that it may have been an agile climber of trees.
The Knife Tooth Cat (Machairodus) is a genus of large machairodont or ''saber-toothed cat'' that lived in Africa, Eurasia and North America during the late Miocene. It is the animal from which the subfamily Machairodontinae gets its name and has since become a wastebasket taxon over the years as many genera of sabertooth cat have been and are still occasionally lumped into it.
A saber-tooth is any member of various extinct groups of predatory therapsids, predominantly carnivoran mammals, that are characterized by long, curved saber-shaped canine teeth which protruded from the mouth when closed. Saber-toothed mammals have been found almost worldwide from the Eocene epoch to the end of the Pleistocene epoch.
Metailurini is an extinct taxonomic tribe of large saber-toothed cats that lived in Africa, Asia, Europe, and North America from the Miocene to the Pleistocene.
Dinictis is a genus of the Nimravidae, an extinct family of feliform mammalian carnivores, also known as "false saber-toothed cats". Assigned to the subfamily Nimravinae, Dinictis was endemic to North America from the Late Eocene to Early Miocene epochs, existing for about 16.8 million years.
Eusmilus is a prehistoric genus of nimravid that lived in Europe and North America during the Late Eocene to Early Oligocene epochs.
Barbourofelidae is an extinct family of carnivorans of the suborder Feliformia, sometimes known as false saber-toothed cats, that lived in North America, Eurasia and Africa during the Miocene epoch and existed for about 7.9 million years. Thought to be an independent lineage from the Nimravidae and Machairodontinae, which had all attained elongated canines, recent research argues that it may be a subfamily of the Nimravidae, extending its biochronological range into the Miocene, although this issue is not yet fully resolved.
Feliformia is a suborder within the order Carnivora consisting of "cat-like" carnivorans, including cats, hyenas, mongooses, viverrids, and related taxa. Feliformia stands in contrast to the other suborder of Carnivora, Caniformia.
Dinailurictis was an extinct nimravid carnivoran belonging to the subfamily Nimravinae. It was named in 1922, with subsequent material being recovered from middle Oligocene deposits across France and Spain.
Quercylurus major is an extinct, cat-like nimravid carnivora from the early Oligocene of France. Its fossils were found in Early Oligocene strata in Quercy. Q. major was possibly the largest nimravid ever known, as its fossils suggest it was similar in size to the modern-day lion.
Sansanosmilus is an extinct genus of carnivorous mammal of the family Barbourofelidae endemic to Europe, which lived during the Miocene, 13.65—9.7 mya, existing for approximately 3.95 million years.
Prosansanosmilus is an extinct genus of barbourofelid that lived in Europe during the Late Miocene epoch, existing for approximately 9.654 million years. It contains Prosansanosmilus peregrinus, which died out in the Miocene epoch.
Ginsburgsmilus is an extinct genus of carnivorous mammal of the family Barbourofelidae that was endemic to Africa during the early Miocene. There is only one known specimen of Ginsburgsmilus napakensis, dated to 20-19 mya.
The cat gap is a period in the fossil record of approximately 25 million to 18.5 million years ago in which there are few fossils of cats or cat-like species found in North America. The cause of the "cat gap" is disputed, but it may have been caused by changes in the climate, changes in the habitat and environmental ecosystem, the increasingly hypercarnivorous trend of the cats, volcanic activity, evolutionary changes in dental morphology of the Canidae species present in North America, or a periodicity of extinctions called van der Hammen cycles.
Amphimachairodus is an extinct genus of large machairodonts. It is also a member of the tribe Homotherini within Machairodontinae and is most closely related to such species as Xenosmilus, Homotherium itself, and Nimravides. It inhabited Eurasia, Northern Africa and North America during the late Miocene epoch.
Tchadailurus is a genus of machairodontine felid from the late Miocene of Chad, Africa.
Sivasmilus is a fossil genus of barbourofelid containing only a single species, Sivasmilus copei. It is known from only a single specimen, a partial mandible collected from the Chinji Formation in the Lower Siwaliks in Pakistan, estimated to be from the Miocene. The fossil was originally described in 1915 when it was assigned to the fossil feline Sivaelurus chinjiensis, but was used as the basis of a new genus and species in 1929 by Hungarian paleontologist Miklós Kretzoi. Sivasmilus copei was a relatively small, cat-like animal.
Stenogale is an extinct genus of carnivorans whose fossils are found in France, Germany, and Switzerland.