User:Wasechun tashunka/sandbox/Canis arnensis

Canis arnensis (also named Arno Dog or Arno River Dog, named after the River Arno near where the first identified fossil was found) is an extinct species of Canidae which was endemic to Europe and lived during the Early Pleistocene epoch.

Distribution
The first identification of C. arnensis followed the discovery of a fossil in the Upper Valdarno. Fossils of the species have only been found in the Tasso Faunal Unit.

It is believed that C. arnensis spread across Europe as the result of a dispersal event which populated the continent with the first modern canids. The species arrived in Italy around 1.9 Ma and was homogenized across southern Europe during the late Villafranchian.

Description
C. arnensis was a medium-sized canid, with a close affinity to modern canids. It had a slightly smaller cranial length than both C. etruscus and the extant C. lupus. C. arnensis featured a lower and more pronounced forehead, with less-developed sagittal and nuchal crests and a bulkier braincase than C. etruscus; in addition, the nasal bones were found to be shorter, stopping short of the maxillofrontal suture.

Relation to other canidae
C. arnensis is often described as being coyote-like or jackal-like, with one analysis suggesting that the species is representative, along with the American C. lepophagus, of a single holarctic "coyote-like dog population". Later analysis, however, suggests that the species is better described as being intermediate between extant jackal and wolf species.

C. arnensis was once considered a synonym of C. etruscus and C. mosbachensis, but this was later rejected based on dental differences; however C. senezensis and C. accitanus were later suggested as synonyms. Morphological similarities also suggest a relation to Canis aureus. One study suggests that C. arnensis may be a basal canid to the group of all derived extant and extinct canids, based on cranial structure.

C. arnensis and C. etruscus have been compared, as they are morphologically similar and are believed to have spread to Western Europe together during the so-called "Canis Event". Morphometric analysis of the cranium and upper teeth show that both C. arnensis and C. etruscus showed characteristics of an intermediate between extant Wolves and Jackal species, with C. arnensis being slightly more jackal-like and C. etruscus slightly more wolf-like; however, in some cranial characteristics, C. arnensis is more wolf-like.