Phenacodus

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Phenacodus
Temporal range: Late Paleocene–Middle Eocene
Phenacodus at AMNH.jpg
P. primaevus skeleton at American Museum of Natural History
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Family: Phenacodontidae
Subfamily: Phenacodontinae
Genus: Phenacodus
Cope, 1873
Species [1]
  • P. bisonensis
  • P. condali
  • P. grangeri
  • P. intermedius
  • P. lemoinei
  • P. magnus
  • P. matthewi
  • P. primaevus(type species)
  • P. teilhardi
  • P. trilobatus
  • P. vortmani
Synonyms

TrispondylusCope, 1884

Phenacodus (Greek: "deception" (phenax), "tooth' (odus) [2] ) is an extinct genus of mammals from the late Paleocene through middle Eocene, about 55 million years ago. It is one of the earliest and most primitive of the ungulates, typifying the family Phenacodontidae and the order Perissodactyla.

Contents

Description

Phenacodus intermedius reached 10 to 39 kg (22 to 86 lb), while P. trilobatus is estimated at 22 to 87 kg (49 to 192 lb). [3] The typical Phenacodus primaevus was a relatively small ungulate about 1.5 m (4 ft 11 in) long and weighed up to 56 kg (123 lb), of slight build, with straight limbs each terminating in five complete toes, and walking in the digitigrade fashion of the modern horse. [4] [5] The middle toe was the largest, and the weight of the body was mainly supported on this and the two adjoining digits, which appear to have been encased in hooves, foreshadowing the tridactyl type common in perissodactyls and certain extinct groups of ungulates. The skull was small, with proportionately minute brain; and the arched back, strong lumbar vertebrae, long and powerful tail, and comparatively feeble fore-quarters all proclaim kinship with the primitive carnivores Creodonta. All the bones of the limbs are separate, and those of the carpus and tarsus do not alternate - each one in the upper row is placed immediately above the corresponding one in the row below. The full series of forty-four teeth was developed; and the upper molars were short-crowned, or brachyodont, with six low cusps, two internal, two intermediate and two external, so that they were of the typical primitive bunodont structure.

In habits, the animal was cursorial and herbivorous, or possibly carnivorous. In the early Paleocene of North America, the place of the above species was taken by Tetraclaenodon puercensis, an animal only half the size of P. primaevus, with the terminal joints of the limbs intermediate between hoofs and claws, and the first and fifth toes taking their full share in the support of the weight of the body. These two genera may be regarded as forming the earliest stages in the evolution of the horse, coming below Hyracotherium (see Equidae). As ancestors of the artiodactyl section of the Ungulata, we may look to forms more or less closely related to the North American Lower Eocene genus Mioclaenus , typifying the family Mioclaenidae. The species of Mioclaenus were five-toed, bunodont Condylarthra, with a decided approximation to the perissodactyl type in the structure of the feet. A second type of Condylarthra from the North American Lower Eocene is represented by the family Meniscotheriidae, including the genus Meniscotherium .

A 2014 cladistic analysis places both Phenacodus and Meniscotherium within stem perissodactyls. [6]

Teeth and jaws probably referable to the Condylarthra have been obtained in European early Tertiary formations. All Ungulata probably originated from Condylarthra.

Phylogeny

Cladogram after Gelfo and Sigé, 2011: [7]

Related Research Articles

Amblypoda was a taxonomic hypothesis uniting a group of extinct, herbivorous mammals. They were considered a suborder of the primitive ungulate mammals and have since been shown to represent a polyphyletic group.

<span class="mw-page-title-main">Perissodactyla</span> Order of hoofed mammals

Perissodactyla is an order of ungulates. The order includes about 17 living species divided into three families: Equidae, Rhinocerotidae (rhinoceroses), and Tapiridae (tapirs). They typically have reduced the weight-bearing toes to three or one of the five original toes, though tapirs retain four toes on their front feet. The nonweight-bearing toes are either present, absent, vestigial, or positioned posteriorly. By contrast, artiodactyls bear most of their weight equally on four or two of the five toes: their third and fourth toes. Another difference between the two is that perissodactyls digest plant cellulose in their intestines, rather than in one or more stomach chambers as artiodactyls, with the exception of Suina, do.

<span class="mw-page-title-main">Ungulate</span> Group of animals that walk on the tips of their toes or hooves

Ungulates are members of the diverse clade Euungulata, which primarily consists of large mammals with hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined to be a polyphyletic and thereby invalid clade based on molecular data. As a result, true ungulates had since been reclassified to the newer clade Euungulata in 2001 within the clade Laurasiatheria while Paenungulata has been reclassified to a distant clade Afrotheria. Living ungulates are divided into two orders: Perissodactyla including equines, rhinoceroses, and tapirs; and Artiodactyla including cattle, antelope, pigs, giraffes, camels, sheep, deer, and hippopotamuses, among others. Cetaceans such as whales, dolphins, and porpoises are also classified as artiodactyls, although they do not have hooves. Most terrestrial ungulates use the hoofed tips of their toes to support their body weight while standing or moving. Two other orders of ungulates, Notoungulata and Litopterna, both native to South America, became extinct at the end of the Pleistocene, around 12,000 years ago.

<span class="mw-page-title-main">Litopterna</span> Extinct order of hoofed mammals

Litopterna is an extinct order of South American native ungulates that lived from the Paleocene to the end of the Pleistocene-early Holocene around 63 million-12,000 years ago, and were also present in Antarctica during the Eocene. They represent the second most diverse group of South American ungulates after Notoungulata. It is divided into nine families, with Proterotheriidae and Macraucheniidae being the most diverse and last surviving families.

<span class="mw-page-title-main">Condylarthra</span> Grouping of extinct mammals

Condylarthra is an informal group – previously considered an order – of extinct placental mammals, known primarily from the Paleocene and Eocene epochs. They are considered early, primitive ungulates. It is now largely considered to be a wastebasket taxon, having served as a dumping ground for classifying ungulates which had not been clearly established as part of either Perissodactyla or Artiodactyla, being composed thus of several unrelated lineages.

<span class="mw-page-title-main">Mesonychia</span> Extinct taxon of carnivorous ungulates

Mesonychia is an extinct taxon of small- to large-sized carnivorous ungulates related to artiodactyls. Mesonychians 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. 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.

<span class="mw-page-title-main">South American native ungulates</span> Extinct clade of mammals

South American native ungulates, commonly abbreviated as SANUs, are extinct ungulate-like mammals of controversial affinities that were indigenous to South America prior to the Great American Biotic Interchange. They comprise five major groups conventionally ranked as orders—Astrapotheria, Litopterna, Notoungulata, Pyrotheria, and Xenungulata—as well as the primitive "condylarth" groups Didolodontidae and Kollpaniinae. It has been proposed that some or all of the members of this group form a clade, named Meridiungulata, though the relationships of South American ungulates remain largely unresolved. The two largest groups of South American ungulates, the notoungulates and the litopterns, were the only groups to persist beyond the mid Miocene. Only a few of the largest species of notoungulates and litopterns survived until the end-Pleistocene extinction event around 12,000 years ago where they became extinct with most other large mammals in the Americas, shortly after the first arrival of humans into the region.

<span class="mw-page-title-main">Xenungulata</span> Extinct order of mammals

Xenungulata is an order of extinct and primitive South American hoofed mammals that lived from the Late Paleocene to Early Eocene. Fossils of the order are known from deposits in Brazil, Argentina, Peru, and Colombia. The best known member of this enigmatic order is the genus Carodnia, a tapir-like and -sized animal with a gait similar to living African elephants.

<span class="mw-page-title-main">Dinocerata</span> Extinct order of mammals

Dinocerata or Uintatheria, also known as uintatheres, is an extinct order of large herbivorous hoofed mammals with horns and protuberant canine teeth, known from the Paleocene and Eocene of Asia and North America. With body masses ranging up to 4,500 kilograms (9,900 lb) they represent some of the earliest known large mammals.

<i>Didolodus</i> Extinct genus of mammals

Didolodus is an extinct genus of mammals from Middle Eocene Argentina. It is an ungulate mammal of uncertain affinities, possibly related to Litopterna, though this is uncertain due to the lack of reliable post-cranial remains, and for now remains Meridiungulata incertae sedis. Its remains were found in the Sarmiento Formation of Patagonia.

<span class="mw-page-title-main">Pantodonta</span> Extinct suborder of mammals

Pantodonta is an extinct suborder of eutherian mammals. These herbivorous mammals were one of the first groups of large mammals to evolve after the end of the Cretaceous. The last pantodonts died out at the end of the Eocene.

<i>Meniscotherium</i>

Meniscotherium is an extinct genus of dog-sized mammal which lived 54–38 million years ago. It was a herbivore and had hooves. Fossils have been found in Utah, New Mexico. and Colorado. Many individuals have been found together, indicating that it lived in groups.

<span class="mw-page-title-main">Hyopsodontidae</span> Extinct family of mammals

Hyopsodontidae is an extinct family of primitive mammals, initially assigned to the order Condylarthra, living from the Paleocene to the Eocene in North America and Eurasia. Condylarthra is now thought to be a wastebasket taxon; hyopsodontids have occasionally been speculated to be related to Afrotheria, but the most recent consensus is that they are related to Perissodactyla. Analysis of the inner ear shows shared characteristics with the Equoidea ; they may be a basal ungulate group near to perissodactyls.

<span class="mw-page-title-main">Phenacodontidae</span> Family of mammals

Phenacodontidae is an extinct family of large herbivorous mammals traditionally placed in the “wastebasket taxon” Condylarthra, which may instead represent early-stage perissodactyls. They lived from the late early Paleocene to early middle Eocene and their fossil remains have been found in North America and Europe. The only unequivocal Asian phenacodontid is Lophocion asiaticus.

<i>Umayodus</i> Extinct genus of mammals

Umayodus is an extinct genus of "condylarth" mammal from the late Paleocene or the earliest Eocene. It is a didolodontid which lived in what is now Peru. It is known from the holotype LU3-801, an isolated right third molar, which was found in the Muñani Formation of Laguna Umayo, Peru. It was first named by Javier N. Gelfo and Bernard Sigé in 2011 and the type species is Umayodus raimondi.

<i>Ocepeia</i> Extinct Afrotherian mammal

Ocepeia is an extinct genus of afrotherian mammal that lived in present-day Morocco during the middle Paleocene epoch, approximately 60 million years ago. First named and described in 2001, the type species is O. daouiensis from the Selandian stage of Morocco's Ouled Abdoun Basin. A second, larger species, O. grandis, is known from the Thanetian, a slightly younger stage in the same area. In life, the two species are estimated to have weighed about 3.5 kg (7.7 lb) and 10 kg (22 lb), respectively, and are believed to have been specialized leaf-eaters. The fossil skulls of Ocepeia are the oldest known afrotherian skulls, and the best-known of any Paleocene mammal in Africa.

<span class="mw-page-title-main">Didolodontidae</span> Extinct family of mammals

Didolodontidae is a possibly paraphyletic family of "condylarth" mammals known from the Paleogene of South America, with most specimens known from Argentina. They were generally small-medium in body size, and had a bunodont dentition. A close relationship with litopterns has been suggested by some studies. They range in age from the early Paleocene (Selandian/Peligran) to late Eocene (Priabonian/Mustersan). The attribution of Salladolodus deuterotheroides from the Late Oligocene of Bolivia to the family is doubtful.

Megadolodus is an extinct genus of proterotheriid litopterns.

Ernestokokenia is an extinct genus of mammal, belonging to the Didolodontidae. It lived during the Early Eocene and the Middle Eocene, and its fossils were discovered in South America.

Sparnotheriodontidae is an enigmatic extinct family of litopterns known primarily from teeth. Sparnotheriodontids are one of two South American native ungulate clades known to have reached Antarctica, the other being astrapotheres.

References

  1. Thewissen, J.G.M. (1990). "Evolution of Paleocene and Eocene Phenacodontidae". University of Michigan Papers on Paleontology. 29: 1–107.
  2. "Glossary. American Museum of Natural History". Archived from the original on 20 November 2021.
  3. Dirks W.; Anemone R. L.; Holroyd P. A.; Reid D. J. (2009). "Phylogeny, Life History and the Timing of Molar Crown Formation in Two Archaic Ungulates, Meniscotherium and Phenacodus (Mammalia, 'Condylarthra')". Comparative Dental Morphology. Frontiers of Oral Biology. 13: 3–8. doi:10.1159/000242381. ISBN   978-3-8055-9229-1. PMID   19828961.
  4. T. S. Kemp (November 4, 2004). The Origin and Evolution of Mammals. Oxford University Press, USA. p. 237. ISBN   9780191545177 . Retrieved 3 March 2024.
  5. Jerison, Harry J (December 2007). "What Fossils Tell Us about the Evolution of the Neocortex" (PDF). Evolution of Nervous Systems: 1–12. doi:10.1016/B0-12-370878-8/00065-3. ISBN   9780123708786. Archived (PDF) from the original on 2022-11-20.
  6. Cooper, L. N.; Seiffert, E. R.; Clementz, M.; Madar, S. I.; Bajpai, S.; Hussain, S. T.; Thewissen, J. G. M. (2014-10-08). "Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls". PLOS ONE. 9 (10): e109232. Bibcode:2014PLoSO...9j9232C. doi: 10.1371/journal.pone.0109232 . PMC   4189980 . PMID   25295875.
  7. Javier N. Gelfo and Bernard Sigé (2011). "A new didolodontid mammal from the late Paleocene–earliest Eocene of Laguna Umayo, Peru" (PDF). Acta Palaeontologica Polonica. 56 (4): 665–678. doi: 10.4202/app.2010.0067 .