Fossil ants (Hymenoptera: Formicidae) of the early Oligocene Canyon Ferry Reservoir deposit

Abstract

The early Oligocene (ca. 32.0 Ma) Canyon Ferry Reservoir deposit is known to contain an extraordinary number of well-preserved plant and animal fossils. Among those are 111 fossil ant specimens that were examined and assigned to five genera: Dolichoderus, Liometopum, Camponotus, Lasius, and Manica from three subfamilies: Dolichoderinae, Formicinae, and Myrmicinae. Two new fossil species are described. Liometopum greenwalti sp. nov. is the third fossil species known from this genus in North America and is morphologically distinct from the other two fossil species that are known from the Florissant deposit. The three fossil Liometopum species are compared to the three extant North American species. Manica iviei sp. nov. is the first fossil species in this genus known from North America and only the second fossil species described. This species possesses a broad ventral postpetiolar process which among North American extant species is only present in Manica hunteri. The Canyon Ferry ants represent the only definitively Oligocene-aged fossil deposit that contains ants in North America and therefore offer a unique view into a time when the modern-day ant communities of the continent were emerging.