Anthracosaurus

The genus and type species Anthracosaurus russelli were named by Thomas Henry Huxley in 1863, based on fossils acquired by mining surveyor James Russell in 1861.[3] Nearly all fossils were found near Airdrie, in the historic County Lanarkshire of Scotland. Geologically speaking, they hail from the Blackband Ironstone of the Scottish Middle Coal Measures. In traditional European stratigraphy, this layer would be dated to the Westphalian B, corresponding to the early-middle part of the Pennsylvanian (Late Carboniferous). The holotype is a large flattened cranium embedded in an ironstone nodule. Due to the tough mineral encrustation, it would take more than a century for the skull to be fully prepared and cleared of matrix.[1] Subsequent to Huxley's original description, incremental preparation allowed for the skull to be redescribed by Watson (1929)[4] and later Panchen (1977).[1] Other fossils from Airdrie include lower jaw fragments, teeth, vertebrae, and possibly a partial interclavicle.[1] It is uncertain whether the postcranial fossils truly belong to Anthracosaurus. The vertebrae are undiagnostic beyond their embolomerous form, while the interclavicle shows similarity to that of Pholiderpeton.[2]

A second, less complete skull from Washington (in the historic County Durham of England) was assigned to Anthracosaurus russelli by Panchen et al. (1967). It is slightly older than the Scottish fossils, dating to the Lower Coal Measures (Westphalian A).[5][1] Panchen (1981) expanded the list of English fossils with an incomplete jaw stored in the Hancock Museum, possibly from the Lower Main Seam of Newsham, Northumberland (Westphalian B).[6] Clack (1987) described two additional Anthracosaurus fossils from Newsham: a partial skull roof (previously referred to Pteroplax cornuta or Eogyrinus attheyi) and an isolated jugal bone.[2]

Romer (1963)[7] attempted to name a second species of Anthracosaurus from the Diamond Coal Mine, a productive Carboniferous site in Linton, Ohio. This American species, Anthracosaurus lancifer, consists of a collection of isolated teeth, vertebrae, and molds of a snout and shoulder girdle. The species name 'lancifer' was borrowed from a large tooth ("Rhizodus lancifer"), an undiagnostic fossil which could belong to a variety of predatory fish or amphibians. The snout does show enlarged premaxillary teeth, but this trait is present in other American embolomeres like Eobaphetes and Neopteroplax. It is probable that "Anthracosaurus lancifer" simply represents adult specimens of another Linton embolomere, Leptophractus obsoletus.[1]