Amphicticeps

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Amphicticeps
Temporal range: Early Oligocene, 33.9–28.4  Ma
Amphicticeps skull.jpg
Holotype skull of Amphicticeps shackelfordi
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Amphicynodontidae
Genus: Amphicticeps
Matthew & Granger, 1924
Type species
Amphicticeps shackelfordi
Matthew & Granger, 1924
Other species
  • A. dorogWang et al., 2005
  • A. makhchinusWang et al., 2005

Amphicticeps is an extinct genus of small, weasel-like carnivoran mammal. It lived in Mongolia during the Oligocene. The genus was erected in 1924 for the species A. shackelfordi on the basis of a well-preserved skull. Historically, the systematic position of this genus has been problematic until more specimens were described decades later. [1]

Contents

History of discovery

Lower jaw of the A. shackelfordi holotype Amphicticeps jaw.jpg
Lower jaw of the A. shackelfordi holotype

The type specimen of Amphicticeps shackelfordi (AMNH 19010) is an almost complete skull. It was discovered during the 1922 field season of the Central Asiatic Expeditions around 2 miles southwest of the Loh campsite in Övörkhangai Province, Mongolia. This locality is part of the Oligocene-aged Hsanda Gol Formation. Though several other jaw elements were also collected, these were not figured or assigned to Amphicticeps in the original description as they could not be firmly associated with the type skull. [1] During the 1994 field season of the Mongolian Academy of Sciences and the American Museum of Natural History joint expeditions, a naturally associated set of lower and upper jaws of A. shackelfordi was found, and the previously known jaw elements can now be confidently assigned to this species. [2]

Assigned species

In addition to the type species, two more species of Amphicticeps were described by Wang et al. in 2005:

A. dorog is currently known exclusively from teeth and jaw elements found in the top of the Tatal Member of the Hsanda Gol Formation, Mongolia. The type specimen (MAE SG.9194) is a fragment of the right maxilla with premolars and molars, and several additional fragments of rami and maxillae are assigned to this species. The specific name is a Mongolian word for 'badger'. This species is believed to be an intermediate form between the less-derived A. shackelfordi and more derived A. makhchinus based on the size and characters of its teeth. [2]

The least-known of the three species, A. makhchinus is known only from the holotype specimen (MAE 93–213) consisting of a right maxillary fragment with preserved teeth. The specimen was collected from the Tatal Member of the Hsanda Gol Formation, Mongolia. The specific name is a Mongolian word meaning 'meat-eater' or 'carnivore', as tooth features indicate this species was the most hypercarnivorous species in the genus. Based on the premolar labial length, A. makhchinus is the largest known species of the Amphicticeps genus, being 32% larger than A. shackelfordi and 16% larger than A. dorog. [2]

Description

Amphicticeps was a small-sized mammal, with the type skull of A. shackelfordi (the smallest species) measuring 8.7 cm from nasal tip to inion. The skull is strongly-built for a carnivoran of this size, with a broad and short rostrum, and moderately-sized canine teeth. The first upper molar has a postprotocrista, enlarged parastyle and no lingual notch on the entoconid crest. The second upper molar is lingually positioned and reduced, and the third upper molar is either very reduced entirely lost. The upper fourth premolar has a carnassial notch and the suprameatal fossa is shallow, these features being primitive compared to the condition seen mustelids. [2]

Classification and systematics

The classification of Amphicticeps has historically been problematic. In their initial description of the genus, Matthew and Granger (1924) suggested it to be a "highly progressive miacid" rather than placing it in any existing carnivoran family. [1] Later authors have assigned it to Arctoidea based on dental or cranial features. Schmidt-Kittler (1981) noted the basicranium to have features matching arctoids, and deemed it not to belong in Musteloidea due to its shallow suprameatal fossa and the form of its molars, thus regarding it to be a "basal arctoid" that emerged before the development of Musteloidea. [3] Hunt (1996) proposed that Amphicticeps may belong in the family Amphicynodontidae, a classification which was followed by Wang and Qiu (2003). [4] [5]

Wang et al. (2005) conducted a phylogenetic analysis finding Amphicticeps to be a basal ursoid, being the earliest-diverging member of the clade containing it, Amphicynodon , Ursidae and Phocoidea. The cladogram results of their phylogenetic analyses are displayed in the cladogram below: [2]

Arctoidea
Ursida

Amphicticeps

Amphicynodon

Ursidae

Cephalogale

Phocoidea

Allocyon

Pachycynodon

(Pinnipedia)
Mustelida

Mustelavus

Procyonidae

Amphictis

Simocyon

Ailuridae

Ailurus

Bavarictis

Mustelictis

Pseudobassaris

Plesictis

Potamotherium

Promartes

Mustelidae

In their description of Eoarctos , Wang et al. (2023) conducted a phylogenetic analysis recovering Amphicticeps as the earliest-diverging pinniped. Their results are shown in the cladogram below: [6]

Arctoidea

Cynodictis spp.

Gustafsonia cognita

Amphicyonidae

Ursoidea

Subparictidae

Ursidae

Amphicynodon leptorhynchus

Campylocynodon personi

Drassonax harpagops

Pachycynodon spp.

Allocyon loganensis

Cephalogale spp.

Ursus arctos

Zodiolestes daimonelixensis

Pinnipedia

Amphicticeps shackelfordi

Potamotherium valletoni

Puijila darwini

Enaliarctos spp.

Pteronarctos spp.

Otariidae

Musteloidea

Paleoecology

Artist's depiction of the Hsanda Gol Formation with Paraceratherium and Hyaenodon Paraceratherium transouralicum.jpg
Artist's depiction of the Hsanda Gol Formation with Paraceratherium and Hyaenodon

All known species of Amphicticeps hail from the Hsanda Gol Formation, which is dated to around 33.4 to 31 million years ago (early Oligocene). This formation is believed to have been deposited in an open, semiarid steppe environment with playa lakes and ephemeral rivers. [7] In this habitat, Amphicticeps lived alongside a wide variety of small mammals including various rodents, the leporid Desmatolagus , and the erinaceid Palaeoscaptor . [8] [9] Sympatric predators included several species of Hyaenodon , the stenoplesictids Shandgolictis and Asiavorator , the feliforms Nimravus and Palaeogale , the amphicynodontid Amphicynodon and the didymoconids Didymoconus and Ergilictis . [10] The largest animal living alongside Amphicticeps in this formation was Paraceratheriumtransouralicum, a giant hornless rhinocerotoid. [11]

Related Research Articles

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

Carnivora is an order of placental mammals that have specialized in primarily eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the fifth largest order of mammals, comprising at least 279 species.

<i>Proailurus</i> Extinct genus of carnivores

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.

<span class="mw-page-title-main">Amphicyonidae</span> Extinct family of carnivores

Amphicyonidae is an extinct family of terrestrial carnivorans belonging to the suborder Caniformia. They first appeared in North America in the middle Eocene, spread to Europe by the late Eocene, and further spread to Asia and Africa by the early Miocene. They had largely disappeared worldwide by the late Miocene, with the latest recorded species at the end of the Miocene in Africa. They were among the first carnivorans to evolve large body size. Amphicyonids are colloquially referred to as "bear-dogs".

<span class="mw-page-title-main">Creodonta</span> Former order of extinct flesh-eating placental mammals

Creodonta is a former order of extinct carnivorous placental mammals that lived from the early Paleocene to the late Miocene epochs in North America, Europe, Asia and Africa. Originally thought to be a single group of animals ancestral to the modern Carnivora, this order is now usually considered a polyphyletic assemblage of two different groups, the Oxyaenids and the Hyenodonts, not a natural group. Oxyaenids are first known from the Palaeocene of North America, while hyaenodonts hail from the Palaeocene of Africa.

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

Hyaenodon ("hyena-tooth") is an extinct genus of carnivorous placental mammals from extinct tribe Hyaenodontini within extinct subfamily Hyaenodontinae, that lived in Eurasia and North America from the middle Eocene, throughout the Oligocene, to the early Miocene.

<span class="mw-page-title-main">Carnassial</span> Mammal tooth type

Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. This adaptation is found in carnivorans, where the carnassials are the modified fourth upper premolar and the first lower molar, however this may vary in family. These teeth are also referred to as sectorial teeth.

<i>Tsaganomys</i> Extinct genus of rodents

Tsaganomys altaicus is an extinct species of rodent from Asia, and the only species in the genus Tsaganomys.

<span class="mw-page-title-main">Tsaganomyidae</span> Extinct family of rodents

The Tsaganomyidae are an extinct family of rodents from Asia. It contains three genera. Tsaganomyids are generally considered to be related to the Hystricognathi. Members of Tsaganomyidae were fossorial (digging) rodents that probably used their incisor teeth to dig like some living mole rats.

<span class="mw-page-title-main">Ursoidea</span> Superfamily of mammals

Ursoidea is a superfamily of arctoid carnivoran mammals that includes the families Subparictidae, Amphicynodontidae, and Ursidae which the last family includes the extant lineages of bears as well the extinct Hemicyoninae and Ursavinae. The interrelationships of ursoids has had slight arrangements. In the past it was thought the extinct Amphicyonidae were stem-bears based on morphological analysis of the ear region, though the most recent publications on early amphicyonids suggests they were basal caniforms. The amphicynodontids are sometimes classified as either a subfamily of bears, a paraphyletic assemblage of early bears, or even stem-pinnipeds. The subparictids were previously classified as amphicynodontine/ids. The hemicyonines have been occasionally reclassified as a separate family.

Nothocyon is an extinct genus of carnivoran in the family Subparictidae which inhabited North America during the late Oligocene. At one time, many species of the dog family Canidae were placed in Nothocyon, but new fossils showed that the type species of Nothocyon, N. geismarianus, is more closely related to bears. The other species have been reassigned to other genera such as Cormocyon.

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

Didymictis is an extinct genus of placental mammals from extinct subfamily Didymictinae within extinct family Viverravidae, that lived in North America and Europe from the late Paleocene to middle Eocene.

<i>Asiavorator</i> Extinct genus of carnivores

Asiavorator is an extinct genus of civet-like carnivoran belonging in the family Stenoplesictidae. It was endemic to Asia and lived during the Eocene and Oligocene epochs.

<i>Palaeogale</i> Extinct genus of carnivores

Palaeogale is an extinct genus of carnivorous mammal known from the Late Eocene, Oligocene, and Early Miocene of North America, Europe, and Eastern Asia. A small carnivore often associated with the mustelids, Palaeogale might have been similar to living genets, civets, and linsangs.

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

Forstercooperia is an extinct genus of forstercooperiine paraceratheriid rhinocerotoids from the Middle Eocene of Asia.

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

Hyaenodonta is an extinct order of hypercarnivorous placental mammals of clade Pan-Carnivora from mirorder Ferae. Hyaenodonts were important mammalian predators that arose during the early Paleocene in Europe and persisted well into the late Miocene.

<span class="mw-page-title-main">Amphicynodontidae</span> Extinct clade of mammals

Amphicynodontidae is a probable clade of extinct arctoids. While some researchers consider this group to be an extinct subfamily of bears, a variety of morphological evidence links amphicynodontines with pinnipeds, as the group were semi-aquatic otter-like mammals. In addition to the support of the pinniped–amphicynodontine clade, other morphological and some molecular analyses support bears being the closest living relatives to pinnipeds. According to McKenna and Bell (1997) Amphicynodontinae are classified as stem-pinnipeds in the superfamily Phocoidea. Fossils of these mammals have been found in Europe, North America and Asia. Amphicynodontines should not be confused with Amphicyonids (bear-dogs), a separate family of Carnivora which is a sister clade to arctoids within the caniforms, but which may be listed as a clade of extinct arctoids in older publications.

Eoarctos is an extinct genus of arctoid carnivorans, known from the latest Eocene to early Oligocene of North Dakota and Nebraska. It is known from several remains, the most notable of which is the almost perfectly preserved skeleton of a large male. It was comparable in build and size to a fisher or small raccoon, with an estimated body mass of 4.3 kg, and possessed a variety of features that indicate a mix of terrestrial and scansorial locomotion. Its most notable feature is its unique dentition, with its massive premolars and hypocarnivorous molars, as well as its robust mandible, indicating that it consumed hard-shelled prey, possibly making it the oldest molluscivorous carnivoran known.

Alagtsavbaatar is an extinct species of carnivorous cat-like carnivoran belonging to the superfamily Aeluroidea. It was endemic to Asia, with all known specimens being found in Mongolia, and lived during the late Eocene epoch. It is a monotypic genus, with the type and only known species being A. indigenus, and is named after the Alag Tsav locality where its remains were first discovered.

<i>Didymoconus</i> Extinct genus of mammal

Didymoconus is an extinct genus of mammal that lived during the early Oligocene epoch. It was endemic to Asia, and its fossils have been found in Mongolia, China and Kazakhstan. It is the type genus of the Didymoconidae, a family of eutherian mammals with uncertain taxonomic affinities.

References

  1. 1 2 3 Matthew, William Diller; Granger, Walter (1924). "New Carnivora from the Tertiary of Mongolia". American Museum Novitates (104). hdl:2246/3213.
  2. 1 2 3 4 5 Wang, Xiaoming; McKENNA, Malcolm C.; Dashzeveg, Demberelyin (2005-07-25). "Amphicticeps and Amphicynodon (Arctoidea, Carnivora) from Hsanda Gol Formation, Central Mongolia and Phylogeny of Basal Arctoids with Comments on Zoogeography". American Museum Novitates (3483): 1–60. doi:10.1206/0003-0082(2005)483[0001:AAAACF]2.0.CO;2. ISSN   0003-0082. S2CID   59126616.
  3. Schmidt-Kittler, Von Norbert (1981). "Zur Stammesgeschichte der marderverwandten Raubtiergruppen (Musteloidea, Carnivora)". Eclogae Geologicae Helvetiae. 74: 753–801.
  4. Hunt, Robert (1996). "15. Biogeography of the Order Carnivora". Carnivore Behavior, Ecology, and Evolution. Cornell University Press. ISBN   9781501745829.
  5. Wang, Banyue; Qiu, Zhanxiang (January 2003). "Notes on early oligocene ursids (Carnivora, Mammalia) from Saint Jacques, Nei Mongol, China". Bulletin of the American Museum of Natural History.
  6. Wang, Xiaoming; Emry, Robert J.; Boyd, Clint A.; Person, Jeff J.; White, Stuart C.; Tedford, Richard H. (2022-06-29). "An exquisitely preserved skeleton of Eoarctos vorax (nov. gen. et sp.) from Fitterer Ranch, North Dakota (early Oligocene) and systematics and phylogeny of North American early arctoids (Carnivora, Caniformia)". Journal of Vertebrate Paleontology. 42 (sup1): 1–123. doi: 10.1080/02724634.2022.2145900 . ISSN   0272-4634.
  7. Richoz, Sylvain; Baldermann, Andre; Frauwallner, Andreas; Harzhauser, Mathias; Daxner-Höck, Gudrun; Klammer, Dietmar; Piller, Werner E. (March 2017). "Geochemistry and mineralogy of the Oligo-Miocene sediments of the Valley of Lakes, Mongolia". Palaeobiodiversity and Palaeoenvironments. 97 (1): 233–258. doi:10.1007/s12549-016-0268-6. ISSN   1867-1594. PMC   5367698 . PMID   28450967.
  8. Matthew, William Diller; Granger, Walter (1923). "Nine new rodents from the Oligocene of Mongolia". American Museum Novitates (102). hdl:2246/3214.
  9. Matthew, William Diller; Granger, Walter; Expeditions (1921-1930), Central Asiatic (1924). "New insectivores and ruminants from the Tertiary of Mongolia, with remarks on the correlation". American Museum Novitates (105). hdl:2246/3212.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  10. Morlo, Michael; Nagel, Doris (2006). "The carnivore guild of the Taatsiin Gol area: Hyaenodontidae (Creodonta), Carnivora, and Didymoconida from the Oligocene of Central Mongolia". Annalen des Naturhistorischen Museums in Wien. Serie a für Mineralogie und Petrographie, Geologie und Paläontologie, Anthropologie und Prähistorie. 108: 217–231. ISSN   0255-0091.
  11. Osborn, Henry Fairfield; Berkey, Charles Peter (1923). "Baluchitherium grangeri, a giant hornless rhinoceros from Mongolia". American Museum Novitates (78). hdl:2246/3262.