Systematics, biogeography, and evolution of Cynorca and Dyseohyus (Tayassuidae). Bulletin of the AMNH ; v. 141, article 2

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New York : [American Museum of Natural History]
"The genus Cynorca Cope, 1867, is a small peccary of Miocene age which stands at the base of the second evolutionary radiation of the Tayassuidae. Although its ancestry has not been brought to light, the genus probably arose from Thinohyus or Perchoerus, primitive genera that range in age from early Oligocene to early Miocene. The oldest known species of Cynorca is C. sociale (Marsh, 1875), recorded from deposits of early Miocene age in Oregon, Texas, and possibly Nebraska. Cynorca sociale was probably adapted to a relatively moist, temperate climate. Three species of Cynorca are recognized as having been derived from C. sociale. Cynorca proterva Cope (1867), the genotypic species, is known from deposits of probably early late Miocene age in Maryland, South Carolina, Texas, and Nebraska. Although the evidence is imperfect, it is likely that C. proterva arose from a local, coastal population of C. sociale sometime in the early or middle Miocene. Inasmuch as C. proterva has been recorded from primarily Eastern and Gulf coastal localities, it almost certainly preferred moist, lowland habitats. This species apparently also ranged into areas such as western Nebraska along the courses of the major east-flowing tributaries of the proto-Mississippi River system. Cynorca occidentale, new species, is first found in middle Miocene deposits of the Montana-Wyoming-Nebraska area after having differentiated from a local population of C. sociale. Thereafter, in the late Miocene, C. occidentale was apparently restricted to areas of more xeric conditions in southern California. A third species, C. hesperia (Marsh, 1871), is of uncertain status. If a valid species, it lived in Oregon in late middle Miocene or early late Miocene time and was probably derived from a northwestern population of C. sociale. Dyseohyus Stock, 1937, is a larger and more advanced derivative of Cynorca. The more primitive of the two species, D. fricki Stock, 1937, is restricted to the late Miocene of California. Dyseohyus fricki is found in some of the same deposits as C. occidentale and probably was also adapted to relatively xeric conditions. Dyseohyus fricki may have been derived from a segment of the Oregon population of C. sociale that was invading drier habitats. The more advanced species of Dyseohyus, D. stirtoni, new species, is found in deposits of late Miocene age in Colorado, Nebraska, and Texas. Dyseohyus stirtoni was apparently adapted to somewhat drier conditions than the geologically and geographically proximal species, C. proterva. Specimens known as Dyseohyus or Cynorca from Texas range in age from early to late Miocene. If this group of specimens represents a single species, it may have given rise to D. stirtoni and was, in turn, derived from C. sociale. Inasmuch as both D. fricki and D. stirtoni were probably derived from the same species of Cynorca (C. sociale), they can be considered as pertaining to one genus. Dyseohyus, as currently constituted, might be polyphyletic at the subspecies level, but the evidence is not adequate for a definitive decision. Aside from C. sociale, which was ancestral to Dyseohyus, and D. stirtomi, which probably gave rise to some of the later peccary species such as Prosthennops niobrarensis, all other species of the two genera reviewed in this report are terminal lineages. A large form, ?Dyseohyus sp., from the late Miocene of Colorado and early Pliocene of Nevada, is aberrant and of uncertain ancestry. As far as can be determined, it, too, represents a terminal lineage"--P. 351.
p. 273-355, [11] p. of plates : ill., maps ; 27 cm.
Includes bibliographical references (p. 352-355).