''Archaeotherium'' ( grc, αρχαιοθήριον, meaning "ancient beast") is an extinct genus of
entelodont
Entelodontidae, the entelodonts, are an extinct family of pig-like artiodactyls (even-toed ungulates) which inhabited the Northern Hemisphere (Asia, Europe, and North America) from the late Eocene to the Middle Miocene epochs, about 38-19 million ...
artiodactyl
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
endemic to
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
during the
Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
and
Oligocene
The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...
epochs (35—28
mya), existing for approximately . ''Archaeotherium'' fossils are most common in the
White River Formation
The White River Formation is a geologic formation of the Paleogene Period, in the northern Great Plains and central Rocky Mountains, within the United States.
It has been found in northeastern Colorado, Dawes County in western Nebraska, Badlands ...
of the
Great Plains
The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, an ...
, but it has also been found in the
John Day Basin of
Oregon
Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...
and the
Trans-Pecos
The Trans-Pecos, as originally defined in 1887 by the Texas geologist Robert T. Hill, is the portion of Texas that lies west of the Pecos River. The term is considered synonymous with Far West Texas, a subdivision of West Texas. The Trans-Peco ...
area of
Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
.
Taxonomy
''Archaeotherium'' was named by
Joseph Leidy
Joseph Mellick Leidy (September 9, 1823 – April 30, 1891) was an American paleontologist, parasitologist and anatomist.
Leidy was professor of anatomy at the University of Pennsylvania, later was a professor of natural history at Swarthmore ...
(1850
Its type is ''Archaeotherium mortoni''. It was synonymized subjectively with ''Entelodon'' by Leidy (1853) and synonymized subjectively with ''Elotherium'' by Leidy (1857). It was assigned to Entelodontidae by Leidy (1850), Peterson (1909), Scott (1940), Galbreath (1953), Russell (1980), Carroll (1988) and Effinger (1998).
''Archaeotherium'', along with all other Entelodontidae, is an
artiodactyl
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
whose exact taxonomic position has been disputed, but taxonomists agree the group lies between the
Suina
Suina (also known as Suiformes) is a suborder of omnivorous, non-ruminant artiodactyl mammals that includes the domestic pig and peccaries. A member of this clade is known as a suine. Suina includes the family Suidae, termed suids, known in Eng ...
(pigs and peccaries), and the
anthracotheres
Anthracotheriidae is a paraphyletic family of extinct, hippopotamus-like artiodactyl ungulates related to hippopotamuses and whales. The oldest genus, ''Elomeryx'', first appeared during the middle Eocene in Asia. They thrived in Africa and Euras ...
,
hippopotamus
The hippopotamus ( ; : hippopotamuses or hippopotami; ''Hippopotamus amphibius''), also called the hippo, common hippopotamus, or river hippopotamus, is a large semiaquatic mammal native to sub-Saharan Africa. It is one of only two extan ...
es, and
whale
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...
s.
Description
''Archaeotherium'' was about tall at the shoulder and around long. Adults weighed 150–250 kg (330-530 lbs). The largest specimens, though much less common, which had been described under the name ''Megachoerus'' had skulls up to long, stood about tall at the shoulder and weighed up to .
There is no sign of sexual dimorphism in the canine teeth; females and males may have been similar in size. Though ''Archaeotherium'' is one of the best preserved of all entelodonts, skulls of entelodonts are far more commonly preserved than full skeletons, and the large size of the head in proportion to the body makes it difficult to accurately estimate the animal's living size and weight.
[Joeckel, R. M.]
A Functional Interpretation of the Masticatory System and Paleoecology of Entelodonts
''Paleobiology'' 16, no. 4 (1990): 459-82.
In life, ''Archaeotherium'' probably somewhat resembled a cow-sized
peccary
A peccary (also javelina or skunk pig) is a medium-sized, pig-like hoofed mammal of the family Tayassuidae (New World pigs). They are found throughout Central and South America, Trinidad in the Caribbean, and in the southwestern area of North A ...
with a longer face, humped shoulders, wide cheekbones, and bosses on the face similar to male
warthog
''Phacochoerus'' is a genus in the family Suidae, commonly known as warthogs (pronounced ''wart-hog''). They are pigs who live in open and semi-open habitats, even in quite arid regions, in sub-Saharan Africa. The two species were formerly cons ...
s, but without a pig-like nasal disk.
Paleobiology
It lived in forested and riverbank environments before the evolution of grasslands. Like all entelodonts, the genus had typical
artiodactyl
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
legs but lacked specializations for fast running; though it supported its weight on cloven hooves, the foot bones remained unfused, and the toes could spread as
camelid
Camelids are members of the biological family Camelidae, the only currently living family in the suborder Tylopoda. The seven extant members of this group are: dromedary camels, Bactrian camels, wild Bactrian camels, llamas, alpacas, vicuñas, ...
feet do. This structure, unique to entelodonts, may have helped the living animal move on soft ground. The head was unusually large, and the high spines on the vertebrae above the shoulders supported strong neck muscles and tendons to handle the weight of the head. The brain was tiny, but had relatively large
olfactory lobes, suggesting that the animal had a keen sense of smell.
Reproduction
''Archaeotherium'', like all entelodonts, possessed huge jugal projections. These projections are sexually dimorphic, with the males having much larger jugals than the females. Due to dimorphism, the function of the expanded jugals was likely used more for display than diet. This same sort of dimorphism can be seen in
giant forest hog
The giant forest hog (''Hylochoerus meinertzhageni''), the only member of its genus (''Hylochoerus''), is native to wooded habitats in Africa and is generally considered the largest wild member of the pig family, Suidae; however, a few subspecie ...
s, so it can be reasonably assumed that entelodont jugals supported large preorbital glands used for
chemical communication signaling the intention to mate. Males would have fought for dominance through non-lethal intraspecific biting as seen by bite marks.
Their mandibular tubercles are also dimorphic, and may have offered protection during combat.
Feeding and diet
![Archaeotherium](https://upload.wikimedia.org/wikipedia/commons/6/60/Archaeotherium.jpg)
The largest (and type) species, ''A. mortoni'', has been analyzed as an omnivore with specializations for biting and chewing resistant objects, such as hard fruits, stems, and bones. Like all entelodonts, the teeth and jaws resemble no living animal, though there are some similarities to peccaries, pigs, bears, predatory carnivores, rhinos, and bone-crushing scavengers. There is a full dentition. The canines, premolars, and molars were all large and heavily enameled, and show heavy wear. The jaws were enormously strong and operated largely by chopping, though they could move laterally enough for the flat molars to grind. There are no blades or notches on any teeth for slicing meat, which are seen in all living and fossil taxa of predators that can chew. ''Archaeotherium'' did not have the ability to slice its meat like most modern predators, but they would have used their strong neck musculature, using their entire head and neck to rip off chunks instead.
[Foss, S. E., 2001, Systematics and paleobiology of the Entelodontidae (Mammalia, Artiodactyla) ]h.D. dissertation
Hilda Doolittle (September 10, 1886 – September 27, 1961) was an American modernist poet, novelist, and memoirist who wrote under the name H.D. throughout her life. Her career began in 1911 after she moved to London and co-founded the ...
Dekalb, Northern Illinois University, 222 p. Fossil evidence suggests that in North America they may sometimes have hunted the early camel ''Poebrotherium'', severing the body in half and crushing and swallowing the foot-long rear section
Bite marks on the cervical vertebrae of the camels suggests they attacked by running alongside their prey, snapping at their necks. The remains of these camels have been found together, implying ''Archaeotherium'' brought its kills to caches for later consumption.
Unlike both grazers and
hypercarnivore
A hypercarnivore is an animal which has a diet that is more than 70% meat, either via active predation or by scavenging. The remaining non-meat diet may consist of non-animal foods such as fungi, fruits or other plant material. Some extant examp ...
s, ''Archaeotherium'' teeth frequently show uneven wear that indicates the animal favored chewing on one side of the jaw, usually the result of tooth damage from hard foods. But the teeth do not show the bone-eating "piecrust fractures" seen in the larger ''
Daeodon
''Daeodon'' is an extinct genus of entelodont even-toed ungulates that inhabited North America about 23 to 20 million years ago during the latest Oligocene and earliest Miocene. The type species is ''Daeodon shoshonensis'', described by a very ...
(Dinohyus),'' which may have specialized more at eating large carcasses''.'' Tooth wear patterns suggest the interlocking front teeth of ''A. mortoni'' were frequently used to strip leaves from plants, but do not show soil scratches from rooting in the ground.
Among living animals, ''Archeotherium'' has some resemblance to peccaries, and may have been a similarly aggressive mixed feeder; it was able to take animals considerably smaller than itself, scavenge on carcasses, and exploit plant foods few other animals can process. (The largest living peccary species, ''
Catagonus wagneri'', eats mostly cacti.
)
Adult ''Archeotherium'' had huge
temporalis
In anatomy, the temporalis muscle, also known as the temporal muscle, is one of the muscles of mastication (chewing). It is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomatic a ...
muscles, but they were normal-sized in juveniles and only developed as the animal matured. This suggests the expanded cheekbones and extreme jaw strength of the genus may have been involved in adult social behavior more than eating. It is also possible that younger animals had softer diets, or ''Archaeotherium'' had significant parental care. Like other entelodonts, the jaws had an unusually wide gape; one entelodont skull shows the animal survived a bite mark near the orbit by another of the same species. Adult entelodonts may have had aggressive jaw-gaping displays and biting fights like living hippos, which have the same adaptation; in male camels, similar wounds result when one animal gets a rival's head between its jaws and bites down with the canines. The gape may also have been used to grab and position large, hard food objects like bones or nuts between the jaws to be cracked by the rear teeth, as in pigs and peccaries.
References
{{Taxonbar, from=Q519252
Entelodonts
Eocene even-toed ungulates
Oligocene even-toed ungulates
Eocene genus first appearances
Eocene mammals of North America
Oligocene mammals of North America
Rupelian genus extinctions
White River Fauna
Fossil taxa described in 1850
Prehistoric even-toed ungulate genera