Armbruster's wolf (''Canis armbrusteri'') is an extinct

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

that was endemic to North America and lived during the Irvingtonian stage of the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

epoch, spanning from 1.9 Mya—250,000 years BP.The _Blancan, Irvingtonian and Rancholabrean Mammal Ages
by Christopher J. Bell and Ernest L. Lundelius Jr., Anthony D. Barnosky, Russell W. Graham, Everett H. Lindsay, Dennis R. Ruez Jr., Holmes A. Semken Jr., S. David Webb, and Richard J. Zakrzewski. January 2004 in the book: Late Cretaceous and Cenozoic Mammals of North America: Biostratigraphy and Geochronology. Chapter: 7. Publisher: Columbia University Press; Editors: Michael O. Woodburne. pp274-276 It is notable because it is proposed as the ancestor of one of the most famous prehistoric carnivores in North America, the

dire wolf The dire wolf (''Aenocyon dirus'' ) is an extinct canine. It is one of the most famous prehistoric carnivores in North America, along with its extinct competitor ''Smilodon''. The dire wolf lived in the Americas and eastern Asia during the Late ...

, which replaced it.

Taxonomy

''Canis armbrusteri'' was named by James W. Gidley in 1913. The first fossils were uncovered at

Cumberland Bone Cave The Cumberland Bone Cave is a fossil-filled cave along the western slope of Wills Mountain on the outskirts of Cumberland, Maryland near Corriganville in Allegany County, Maryland. History and paleontology In 1912 workers excavating a cut for th ...

, Maryland, in an Irvingtonian terrestrial horizon. Fossil distribution is widespread throughout the United States.''Preliminary report on a recently discovered Pleistocene cave deposit near Cumberland, Maryland'', JW Gidley - 1913 - US Government Printing Office
/ref> Middle Pleistocene in North America. The North American wolves became larger, with tooth specimens indicating that '' C. priscolatrans'' diverged into the large wolf ''C. armbrusteri''. R. A. Martin disagreed, and believed that ''C. armbrusteri'' was ''C. lupus''. Ronald M. Nowak disagreed with Martin and proposed that ''C. armbrusteri'' was not related to ''C. lupus'' but ''C. priscolatrans'', which then gave rise to ''C. dirus''. Richard H. Tedford proposed that the South American '' C. gezi'' and '' C. nehringi'' share dental and cranial similarities developed for hypercarnivory, suggesting ''C. armbrusteri'' was the common ancestor of ''C. gezi'', ''C. nehringi'' and ''C. dirus''. Based on morphology from China, the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Middle Pleistocene The Chibanian, widely known by its previous designation of Middle Pleistocene, is an age in the international geologic timescale or a stage in chronostratigraphy, being a division of the Pleistocene Epoch within the ongoing Quaternary Period. Th ...

and is a wolf-like form larger than any ''Canis'' at that time. The three noted paleontologists X. Wang, R. H. Tedford and R. M. Nowak have all proposed that ''C. dirus'' had evolved from ''C. armbrusteri'', with Nowak stating that there were specimens from Cumberland Cave, Maryland that indicated ''C. armbrusteri'' diverging into ''C. dirus''. The two taxa share a number of characteristics (

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

), which suggests an origin of ''dirus'' in the late Irvingtonian in the open terrain in the midcontinent, and then later expanding eastward and displacing ''armbrusteri''.

References

{{Taxonbar, from=Q3884275 Wolves Prehistoric canines Pleistocene carnivorans Prehistoric mammals of North America Irvingtonian Fossil taxa described in 1913