Perchoerus
Extinct genus of peccary
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Perchoerus is an extinct genus of suine (pig-like mammal) from the Eocene and Oligocene of North America. Three species are known.[2][1][3] While often considered one of the earliest peccaries (Tayassuidae), other studies have recovered it to be a basal suine outside of either peccaries or Suidae (Old World pigs).[4] Perchoerus is a rare component of the White River fauna, and the largest species, P. probus, also occurs in the John Day Formation of Oregon.[1]
| Perchoerus | |
|---|---|
| |
| Left maxilla fragments of P. minor (specimen USNM 206190) | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Infraclass: | Placentalia |
| Order: | Artiodactyla |
| Family: | Tayassuidae |
| Genus: | †Perchoerus Leidy, 1869 |
| Type species | |
| Palaeochoerus probus Leidy, 1856 | |
| Species | |
| |
| Synonyms[1] | |
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Description
Perchoerus had a steeply-sloped skull with a short snout. It was similar in some respects to Thinohyus, another peccary-like suine from the Oligocene of the John Day Formation. Both are rare, and historically Perchoerus and Thinohyus have often been confused for each other.[2] There are still some clear differences: Perchoerus has a shorter snout, stronger sagittal crests, and more lightly-built zygomatic and occipital areas. In addition, its M3 (upper third molar) is simpler and shorter from front-to-back, and there is less of a gap (diastema) between its canines and premolars.[3][1]
As reported by Scott (1913), the molars of Perchoerus are generally quadrituberculate (four-cusped) and lack any of the accessory cuspules (minor cusps) present in modern peccaries. The feet bore 4 functional digits and had free metacarpals. The bones in the forearm were separate rather than fused.[5]
Species
- P. minor is the oldest and smallest known species of Perchoerus, only the size of a house cat.[6] It is known from skull and tooth material from the Chadronian (latest Eocene, 36-34 Ma) of Nebraska, South Dakota, and Wyoming.[1] Apart from its minuscule size, the jaw more slender and the molars more simple than other Perchoerus species.[1]
- P. nanus was slightly younger and larger, from the Orellan (earliest Oligocene, 34-32 Ma) of Nebraska, South Dakota, and Colorado. It was intermediate between the other two species in anatomy.[1][6]
- P. probus was the latest and largest species, from the Whitneyan to early Arikareean (Oligocene, 32-30 Ma) of Nebraska, South Dakota, and Oregon. The type species of Perchoerus, P. probus was about as large as living peccaries (~35 kg (77 lb)),[7] and is known from more remains than the other species. Apart from its larger size, it also had larger cheek teeth and a more complex structure of its third molars (m3 and M3).[1][3][6]
