Leptocyon

Leptocyon
Original drawing of the holotype of Leptocyon gregorii from 1907
Temporal occurrence
Rupelian (Lower Oligocene ) to Messinian (Upper Miocene )
approx. 34 to approx. 7 million years
Systematics
Higher mammals (Eutheria) Laurasiatheria Predators (Carnivora) Canine (Caniformia) Dogs (Canidae) Leptocyon
Scientific name
Leptocyon
Matthew , 1918

Leptocyon fossil sites in North America

Leptocyon ( Greek : λεπτός leptos 'slim, narrow' and κύον cyon 'dog') is an extinct North American genus of dogs (Canidae).

features

The fossil remains that are known from Leptocyon - naturally only skeletal remains - show that all members of the genus were quite small and fox-like, with elongated, comparatively delicate jaws and relatively small, widely spaced premolars. This jaw structure clearly distinguishes Leptocyon from the contemporary borophagines , which have a much stronger and more compact dentition. The individuals of none of the Leptocyon species are believed to have weighed much more than 2 kg.

Due to the similarity of its skeleton to that of the red fox and its closest relationship, Leptocyon has been classified by some authors as a younger synonym of Vulpes . It differs from this genus, however, in that it has a stronger postorbital constriction of the skull and special features of its teeth: small cusps on the inside (medial) on the upper incisors (I1-I3); a more strongly developed anterior cusp (parastyle) on the broad lip-side ledge (stylar shelf) of the upper molars (M1-M2); a missing rear (distal) main cusp (hypoconulid) as well as at least in the early species a relatively small rear-tongue side (distolingual) main cusp (entoconid) on the first lower molar (m1); a less developed front lip-side (anterolabial) ledge (cingulum) on the second lower molar (m2) and on the same tooth a main cusp (metaconid) located on the front of the tongue, which in the early representatives is smaller or the same size as the front-lip side located main cusps (Protoconid). Furthermore, Leptocyon and Vulpes can be differentiated from one another based on some features of the limb bones. These are: a more robust ulna and fibula with large lower (distal) articulation surfaces for the radius and tibia as well as a larger entocuneiform (a tarsal bone) and a fully functional metatarsal I (the innermost metatarsal bone) with two phalanges (phalanxes).

Geographical and stratigraphic distribution

The genus first appeared at the beginning of the Oligocene about 34 million years ago and lasted until about 7 million years ago into the late Miocene . Leptocyon was limited in its distribution to North America, which means that the Caninae probably also originated in North America. Canines from the genera Eucyon  †, Vulpes and Canis did not appear in the Old World until about 7 million years ago . The vast majority of leptocyon -Fundstellen located in the Midwest (especially in Nebraska ) and the west (especially in California ) of the United States.

Systematics

The genus Leptocyon comprises nine formally named and two informal species (list from Tedford et al., 2009):

• Leptocyon sp. A; early Oligocene
• Leptocyon douglassi Tedford et al., 2009; middle Oligocene
• Leptocyon mollis ( Merriam , 1906); middle Oligocene
• Leptocyon delicatus ( Loomis , 1932); late Oligocene, the smallest Leptocyon species
• Leptocyon gregorii ( Matthew , 1907); recent Oligocene
• Leptocyon vulpinus ( Matthew , 1907); late Oligocene to early Miocene
• Leptocyon Leidyi Tedford et al., 2009; early to middle Miocene
• Leptocyon sp. B; early to middle Miocene
• Leptocyon vafer ( Leidy , 1858); middle to late Miocene; Generotype (by monotype)
• Leptocyon matthewi Tedford et al., 2009; middle to late Miocene
• Leptocyon tejonensis Tedford et al., 2009; middle to late Miocene

The results of the relationship analysis of the Caninae by Tedford et al. (2009), the geologically younger Leptocyon species are more closely related to the Canine genera that still exist today than to the older Leptocyon species, i.e. H. the species is paraphyletisch and represents a stage of development (engl. grade ), at the base of Caninae. Strictly speaking, therefore, for all the formally named species listed above, with the exception of the type L. vafer , either new genera would have to be established or genera currently treated as younger synonyms ( e.g. Neocynodesmus MacDonald , 1963 for L. delicatus ) would have to be reactivated.

literature

• Richard H. Tedford, Xiaoming Wang, Beryl E. Taylor: Phylogenetic systematics of the North American fossil Caninae (Carnivora, Canidae). Bulletin of the American Museum of Natural History. Vol. 325, 2009 ( online )
• Xiaoming Wang, Richard H. Tedford, Mauricio Antón: Dogs, their fossil relatives & evolutionary history. Columbia University Press, New York, 2008, ISBN 978-0-231-13528-3 .

Web links

• Leptocyon in the Paleobiology Database

Individual evidence

1. ^ Tedford et al .: Phylogenetic systematics of the North American fossil Caninae. 2009 (see literature ), p. 14 ff.
2. ^ William D. Matthew: Contributions to the Snake Creek fauna, with notes upon the Pleistocene of western Nebraska, American Museum Expedition of 1916. Bulletin of the American Museum of Natural History. Vol. 38, No. 7, 1918 ( online ), p. 190
3. ^ Tedford et al .: Phylogenetic systematics of the North American fossil Caninae. 2009 (see literature ), Fig. 65/66, p. 172 ff.
4. ↑ James Reid Macdonald: The Miocene faunas from the Wounded Knee area of ​​western South Dakota. Bulletin of the American Museum of Natural History. Vol. 125, No. 3, 1963 ( online ), p. 212