Chiromyoides | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Plesiadapiformes |
Family: | † Plesiadapidae |
Genus: | † Chiromyoides Stehlin, 1916 |
Type species | |
†Chiromyoides campanicus Stehlin, 1916 | |
Species | |
†Chiromyoides caesorGingerich, 1973 Contents |
Chiromyoides is a small plesiadapid primatomorph that is known for its unusually robust upper and lower incisors, deep dentary, and comparatively small cheek teeth. Species of Chiromyoides are known from the middle Tiffanian through late Clarkforkian North American Land Mammal Ages (NALMA) of western North America, and from late Paleocene deposits in the Paris Basin, France.
The unique dental morphology of Chiromyoides has led several authors to propose a specialized ecological role for the genus. Gingerich (1976) hypothesized that Chiromyoides was a specialist on seeds, while Szalay and Delson (1979) and Beard et al. (2020) suggested that it may have consumed wood-boring insects in a manner similar to the aye-aye. [1] [2] [3]
The type species of Chiromyoides, Chiromyoides campanicus, was originally described in 1916 from fragmentary craniodental material discovered in Cernay, France, with additional material also later found at Berru. [4] [5] Gingerich (1973) described the first North American species, Chiromyoides caesor, from two upper incisors found in northern Wyoming. [6] Several years later, he described three additional North American species, Chiromyoides major, Chiromyoides minor, and Chiromyoides potior, from isolated upper incisors found in northern Wyoming, southern Wyoming, and southern Colorado, respectively. [7] Secord (2008) named Chiromyoides gingerichi from material found in northern Wyoming and southern Montana, Burger and Honey (2008) named Chiromyoides gigas from several incisors found in northern Colorado, and Beard et al. (2020) named Chiromyoides kesiwah from material found at several localities in southwestern Wyoming. [8] [9] [3] A second European species, Chiromyoides mauberti, was named by De Bast et al. (2018) from isolated teeth and several mandibular fragments found near Rivecourt, France. [10]
Chiromyoides is known only from isolated teeth, mandibular fragments, and maxillary fragments, and its relationships to other plesiadapiforms are not well understood. Chiromyoides is generally acknowledged to be a member of the family Plesiadapidae, along with Plesiadapis , Platychoerops , Nannodectes , and Pronothodectes . Recent phylogenetic analyses suggest that Chiromyoides is descended from Plesiadapis, perhaps most closely related to Plesiadapis walbeckensis [11] [12] or Plesiadapis tricuspidens . [3]
Beard et al. (2020) found that species of Chiromyoides separated into two distinct clades: a more southern clade consisting of Chiromyoides gigas, C. minor , and Chiromyoides kesiwah from southern Wyoming and Colorado, and a northern clade including Chiromyoides major, Chiromyoides gingerichi, Chiromyoides campanicus, and Chiromyoides mauberti. Chiromyoides caesor formed a polytomy with the two main clades. Chiromyoides potior was not included in their analysis. [3] The nesting of the European species C. campanicus and C. mauberti in the northern clade suggests that Chiromyoides dispersed into Europe from North America.
The oldest specimens of Chiromyoides are C. minor from the Chappo Type Locality in Lincoln County, Wyoming, and an edentulous mandible from the Black Peaks region of southwest Texas that has been referred to either C. minor or an indeterminate species of Chiromyoides. [1] [3] Both the Chappo locality and the Ray's Bonebed locality of southwest Texas where the edentulous mandible was found are arguably middle Tiffanian (Ti3) in age. [1] [13] Chiromyoides caesor and C. kesiwah come from slightly younger Tiffanian (Ti4) beds in the Bighorn Basin and Washakie Basin, respectively, [8] [3] while C. potior, C. gigas, C. gingerichi, and C. major come from even younger Tiffanian and Clarkforkian deposits in Colorado, Wyoming, and Montana. [8] [9]
Chiromyoides campanicus comes from localities in the Paris Basin that appear to correlate with the late Tiffanian of North America, while C. mauberti occurs in somewhat younger strata that correlates with the North American Clarkforkian NALMA. [12] [14]
Plesiadapis is one of the oldest known primate-like mammal genera which existed about 58–55 million years ago in North America and Europe. Plesiadapis means "near-Adapis", which is a reference to the adapiform primate of the Eocene period, Adapis. Plesiadapis tricuspidens, the type specimen, is named after the three cusps present on its upper incisors.
Bisonalveus is an extinct genus of shrew-like mammals that were presumably ground-dwelling and fed on plants and insects. Bisonalveus fossils have been discovered in the upper Great Plains region of North America, including sites in modern-day Wyoming, North Dakota, Montana, and Alberta. The fossils have been dated to 60 million years ago, during the Tiffanian North American Stage of the Palaeocene epoch. Bisonalveus is the last known genus of the Pentacodontinae sub-family to have arisen, replacing the genus Coriphagus in the early Tiffanian. Bisonalveus itself appears to have gone extinct by the middle Tiffanian.
Paroodectes is an extinct genus of placental mammals from clade Carnivoraformes, that lived in Europe during middle Eocene.
Plesiadapidae is a family of plesiadapiform mammals related to primates known from the Paleocene and Eocene of North America, Europe, and Asia. Plesiadapids were abundant in the late Paleocene, and their fossils are often used to establish the ages of fossil faunas.
Vassacyon is an extinct genus of placental mammals from clade Carnivoraformes, that lived in North America and Europe from the late Paleocene to early Eocene. It is considered the largest of the early Eocene mammals.
Xinyuictis is an extinct genus of placental mammals from clade Carnivoraformes, that lived in Asia from early to late Eocene.
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.
Ictidopappus is an extinct genus of mammals from extinct subfamily Ictidopappinae within extinct family Viverravidae, that lived in North America during the early Paleocene.
The Clarkforkian North American Stage, on the geologic timescale, is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 56,800,000 to 55,400,000 years BP lasting 1.4 million years.
The Tiffanian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 60,200,000 to 56,800,000 years BP lasting 3.4 million years.
The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene, or Clarkforkian, Wasatchian and Bridgerian in the NALMA classification.
The Wasatch Formation (Tw) is an extensive highly fossiliferous geologic formation stretching across several basins in Idaho, Montana Wyoming, Utah and western Colorado. It preserves fossils dating back to the Early Eocene period. The formation defines the Wasatchian or Lostcabinian, a period of time used within the NALMA classification, but the formation ranges in age from the Clarkforkian to Bridgerian.
The Conglomérat de Cernay is a geologic formation in Champagne-Ardenne, northern France. It preserves fossils dating back to the Thanetian stage of the Paleocene period. The lizard Cernaycerta and placental mammal Bustylus cernaysi are named after the formation.
Acidomomys is a plesiadapiform mammal of the family Paromomyidae, a precursor to the primates or very closely related to them.
Carpodaptes was a genus that encompassed small, insectivorous animals that roamed the Earth during the Late Paleocene. Specifically, Carpodaptes can be found between the Tiffanian and Clarkforkian periods of North America. Although little evidence, this genus may have made it through to the early Eocene. They are known primarily from collections of jaw and teeth fragments in North America, mainly in southwestern Canada and northwestern America. Carpodaptes are estimated to have weighed approximately 53-96 grams which made them a little bigger than a mouse. However small, Carpodaptes was a placental mammal within the order Plesiadapiformes that appeared to have a high fiber diet. This insect-eating mammal may have been one of the first to evolve fingernails in place of claws. This may have helped them pick insects, nuts, and seeds more easily off the ground than with paws or claws. Carpodaptes was thought to only exist in North America but recent discoveries of dentition fragments have been found in China.
Protictis is an extinct paraphyletic genus of placental mammals from extinct subfamily Didymictinae within extinct family Viverravidae, that lived in North America from early Paleocene to middle Eocene.
Navajovius is an extinct genus of plesiadapiforms that lived during the Paleocene epoch. Plesiadapiforms were small, arboreal mammals that are theorized to be either closely related to primates or dermopterans. Navajovius has only been documented from localities within North America. This genus was officially named in 1921 by Walter Granger and William Matthew and the type specimen is housed at the American Museum of Natural History.
Saxonella is a genus of extinct primate from the Paleocene Epoch, 66-56 Ma. The genus is present in the fossil record from around ~62-57 Ma. Saxonella has been found in fissure fillings in Walbeck, Germany as well as in the Paskapoo Formation in Alberta, Canada. Saxonella is one of five families within the superfamily Plesiadapoidae, which appears in the fossil record from the mid Paleocene to the early Eocene. Analyses of molars by paleontologists suggest that Saxonella most likely had a folivorous diet.
Viverravinae is an extinct subfamily of mammals from extinct family Viverravidae, that lived from the early Palaeocene to the middle Eocene in North America, Asia and Europe.
Didymictinae is an extinct subfamily of mammals from extinct family Viverravidae, that lived from the early Palaeocene to the middle Eocene in North America and Europe.