A well preserved paracanthopterygian fish (Teleostei) from freshwater lower Paleocene deposits of Montana

ABSTRACT

A new genus and species of paracanthopterygian fish, †McConichthys longipinnis, is described from freshwater deposits of the Lower Paleocene Tullock Formation in Montana. It is the earliest known paracanthopterygian from North America. Although it is known from only a single specimen, it is nearly complete and extremely well preserved. †McConichthys is considered to be most closely related to (forming a cladistic trichotomy with) two monophyletic groups of Patterson and Rosen (in press): the Gadiformes (codfishes) and the Pediculati (a group containing Lophiiformes [anglerfishes] and Batrachoidiformes [toadfishes]). The fossil species is therefore placed in its own family (†McConichthyidae, fam. nov.).

Well preserved, articulated freshwater teleosts from the pre-Eocene of North America are extremely rare, and †McConichthys longipinnis gives important insight into the composition of the earliest Tertiary freshwater fish faunas. This species also provides an early fossil well enough preserved to be easily included in phylogenetic studies of living paracanthopterygian fishes.