The
creodonts are an extinct
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of
mammalMammals are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.Mammals are divided into three main...
s that lived from the
PaleoceneThe Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from 65.5 ± 0.3 Ma to 55.8 ± 0.2 Ma . It is the first epoch of the Palaeogene Period in the modern Cenozoic era...
to the
MioceneThe Miocene is a geological epoch of the Neogene period and extends from about 23.03 to 5.33 million years before the present . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the...
epochs. They shared a common ancestor with the
CarnivoraThe diverse order Carnivora includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...
.
Creodonts were an important group of carnivorous mammals from 55 to 35 million years ago in the ecosystems of
AfricaAfrica is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area. With a billion people in 61 territories, it accounts for about 14.8% of the...
,
EurasiaEurasia is a large landmass covering about 52,990,000 km
2 or about 10.6% of the Earth's surface...
and
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
. In
OligoceneThe Oligocene is a geologic epoch of the Paleogene period and extends from about 33.9 million to 23 million years before the present. As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
Africa, they were the dominant predatory group. They competed with the
MesonychidMesonychia are an extinct order of medium to large-sized carnivorous mammals that were closely related to artiodactyls , and to cetaceans...
s and the
EntelodontEntelodonts, sometimes nicknamed Hell Pigs or Terminator Pigs is an extinct family of pig-like omnivores endemic to forests and North America, Europe, and Asia and from the middle Eocene to early Miocene epochs , existing for approximately .-Taxonomy:Entelodontidae was named by Richard Lydekker and...
s and ultimately outlasted them by the start of the Oligocene and by the middle of the
MioceneThe Miocene is a geological epoch of the Neogene period and extends from about 23.03 to 5.33 million years before the present . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the...
respectively, but lost ground to the carnivorans. The last genus went extinct 8 MYA, and carnivorans now occupy their ecological niches.
Evolution and taxonomy
Creodonts were traditionally considered ancestors to Carnivora, but are now considered to have shared a common ancestor further back - possibly a
CimolestaCimolesta is an extinct order of mammals. A few experts place the pangolins within Cimolesta, though most other experts prefer to place the pangolins within their own order, Pholidota....
such as
CimolestesCimolestes is a genus of early eutherians. The species are found primarily in North America, where they first appeared during the Late Cretaceous, and died out during the Paleocene....
. They share with the Carnivora the
carnassial shear, a modification of teeth that evolved to slice meat in a manner like scissors and gave both orders the tools to dominate the
nicheIn ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different school if the members of these schools utilize significantly different...
. Some researchers argue that the creodonts represent a group of mammals of diverse biological ancestry that resemble one another via
convergent evolutionConvergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, birds and bats do, and are capable of powered flight. The wings are similar in...
, rather than being the descendants of a single common ancestor. Their origins lie at least as far back as the late
CretaceousThe Cretaceous , Latin language for "chalky", usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period of the...
, though they did not
radiateAn adaptive radiation is a rapid evolutionary radiation characterized by an increase in the morphological and ecological diversity of a single, rapidly diversifying lineage. Phenotypes adapt in response to the environment, with new and useful traits arising...
much until the
CenozoicThe Cenozoic Era The Cenozoic (also Cænozoic or Cainozoic) Era The Cenozoic (also Cænozoic or Cainozoic) Era (meaning "new life" (Greek (kainos), "new", and (zoe), "life"), is the most recent of the three classic geological eras and covers the period from 65.5 million years ago to the...
. Creodonts were the dominant carnivorous mammals from 55 to 35
MYAIn astronomy, geology, and paleontology, mya or "m.y.a." is an abbreviation for "million years ago". Like the related unit bya, mya is traditionally written in lower case...
, peaking in diversity and prevalence during the
EoceneThe Eocene epoch, lasting from 55.8 ± 0.2 to 33.9 ± 0.1 Ma , is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era. The Eocene spans the time from the end of the Paleocene epoch to the beginning of the Oligocene epoch. The start of the...
. By the mid
OligoceneThe Oligocene is a geologic epoch of the Paleogene period and extends from about 33.9 million to 23 million years before the present. As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
, Creodonts supplanted both the Mesonychids, and giant flightless predatory birds entirely in
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
,
EurasiaEurasia is a large landmass covering about 52,990,000 km
2 or about 10.6% of the Earth's surface...
and
AfricaAfrica is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area. With a billion people in 61 territories, it accounts for about 14.8% of the...
, and in turn, competed with their own relatives, the Carnivorans. The last genus,
DissopsalisDissopsalis is a genus of extinct predatory mammals of the order Creodonta. The older species, D. pyroclasticus, lived in Kenya during the middle Miocene, while the type species, D. carnifex, ranged from, Pakistan, India to China during the middle to late Miocene .Dissopsalis is the last known...
, went extinct about eight million years ago.
Habitat
The creodonts ranged across
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
,
EurasiaEurasia is a large landmass covering about 52,990,000 km
2 or about 10.6% of the Earth's surface...
and
AfricaAfrica is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area. With a billion people in 61 territories, it accounts for about 14.8% of the...
, in forms that resemble those of some modern carnivores. Amongst their number was
MegistotheriumMegistotherium osteothlastes was an enormous hyaenodontid creodont that lived during the early Miocene Epoch some 24 million years ago and is one of the largest terrestrial carnivorous mammals that ever existed. It was named by Robert Savage in 1973...
, which may have been the largest mammalian land predator of all time, the size of a
bisonMembers of the genus Bison are large even-toed ungulates within the subfamily Bovinae. Two extant species and four extinct species are recognized...
and with a skull twice as big as a tiger's.
Megistotherium may have rivaled
Andrewsarchus mongoliensisAndrewsarchus mongoliensis , , was a basal, heavily-built, wolf-like, hoofed mammal that lived during the Eocene epoch, roughly between 45 and 36 million years ago. It walked on four short legs and had a long body, a long tail, and feet with hoofed toes...
in size. Their dominance over the early Carnivora, known as miacids, began to wane after 35 MYA. The creodonts survived until 8 million years ago; the last form,
DissopsalisDissopsalis is a genus of extinct predatory mammals of the order Creodonta. The older species, D. pyroclasticus, lived in Kenya during the middle Miocene, while the type species, D. carnifex, ranged from, Pakistan, India to China during the middle to late Miocene .Dissopsalis is the last known...
, died out in
PakistanPakistan , officially the Islamic Republic of Pakistan, is a country located at the crossroads of South Asia, the Middle East, and Central Asia...
.
BearBears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern...
s,
catThe cat , also known as the domestic cat or housecat to distinguish it from other felines and felids, is a small carnivorous mammal that is valued by humans for its companionship and its ability to hunt vermin and household pests...
s,
mustelidsMustelidae or Mustelids , commonly referred to as the weasel family, is a family of carnivorous mammals...
,
hyenaThe Hyaenidae is a mammalian family of order Carnivora. The Hyaenidae family, native to both African and Asian continents, consists of four living species, the Striped Hyena and Brown Hyena , the Spotted Hyena , and the Aardwolf .-Evolution:Hyenas seem to have originated 26 million years ago from...
s,
canidsCanidae is the biological family of carnivorous and omnivorous mammals that includes the wolves, foxes, jackals, coyotes, and the domestic dog; a member of this family is called a canid . The Canidae family is divided into the "wolf-like" and "dog-like" animals of the tribe Canini and the "foxes"...
such as wolves and other Carnivora now occupy the former creodont niches.
Reasons for extinction
It is not known exactly why the creodonts were replaced by Carnivora. It may be because of their smaller brains and their
locomotionAnimal locomotion, which is the act of self-propulsion by an animal, has many manifestations, including running, jumping and flying. Animals move for a variety of reasons, such as to find food, a mate, or a suitable microhabitat, and to escape predators...
, which was somewhat less energy-efficient (especially while running) and mostly
plantigraderight|151px|thumb|Human skeleton, showing plantigrade habitIn mammals, plantigrade locomotion means walking with the podials and metatarsals flat on the ground....
. These subtle disadvantages may have been important over millions of years. The creodont lumbosacral spine was not arranged as efficiently for running as in Carnivora. The arrangement of the teeth was also somewhat different. In the miacids (and so in the modern Carnivora), the last upper
premolarThe premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
and the first lower
molarMolars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
are the
carnassialCarnassials are large teeth found in many carnivorous mammals, used for shearing flesh and bone in a scissor or shear-like way. In the Carnivora, the carnassials are the modified last upper premolar and the first lower molar, but in the prehistoric creodonts, the carnassials were further back in...
s, allowing grinding teeth to be retained behind for feeding on non-meat foods (the
CanidaeCanidae is the biological family of carnivorous and omnivorous mammals that includes the wolves, foxes, jackals, coyotes, and the domestic dog; a member of this family is called a canid . The Canidae family is divided into the "wolf-like" and "dog-like" animals of the tribe Canini and the "foxes"...
are the closest modern analog to miacid dentition). In creodonts, the carnassials were further back - either first upper and second lower molars, or second upper and third lower molars. This committed them to eating meat almost exclusively.
In the most strictly carnivorous family of modern Carnivora, the
FelidaeFelidae is the biological family of the cats; a member of this family is called a felid. Felids are the strictest carnivores of the sixteen mammal families in the order Carnivora...
, the second and third molars have disappeared completely, and the first upper molars behind the carnassials have become vestigial. Modern cats thus eat plant food only incidentally.
JaguarThe Jaguar, Panthera onca, is a big cat, a feline in the Panthera genus. It is the only Panthera species found in the Americas. The jaguar is the third-largest feline after the tiger and the lion, and the largest and most powerful feline in the Western Hemisphere...
s, for example, have been known to eat avocados.