THE GIANT ARTHROPLEURA TRACKWAY DIPLICHNITES CUITHENSIS FROM THE CUTLER GROUP (UPPER PENNSYLVANIAN) OF NEW MEXICO

Nonmarine redbeds of the Cutler Group in El Cobre Canyon, New Mexico are a classic Pennsylvanian-Permian vertebrate fossil collecting locality. Recent collecting has yielded an important addition to the El Cobre fossil record, a giant terrestrial arthropod trackway assigned to Diplichnites cuithensis Briggs, Rolfe and Brannan. The trackway is preserved in concave epirelief on ripple-laminated micaceous arkosic sandstone that is stratigraphically low in the Cutler Group section; these strata are of Late Pennsylvanian (Missourian?) age based on palynostratigraphy and megafossil plant and vertebrate biostratigraphy. The tracks are well preserved and interpreted as having been made in a lacustrine-margin setting, most likely under subaerial conditions. The trackway contains two track rows of mostly crescentic imprints oriented perpendicular to the midline. The trackway course is straight to gently sinuous with a length of ~210 cm. Each row is missing a mid-length section of ~50 cm due to erosion. The external trackway width is 32-36 cm. Imprints are 5-7 cm wide and up to 2 cm deep. Spacing between imprints varies between 2.5 and 4 cm. The large dimensions and simple morphology of the tracks are comparable to the diagnostic description of D. cuithensis. The El Cobre trackway is the first occurrence of D. cuithensis in western North America and the first assigned record from the USA. D. cuithensis ranges in age from Viséan to Stephanian. The tracks are attributable to Arthropleura, a gigantic terrestrial myriapod. Arthropleura body fossils have not been reported from western North America, although there are records from Nova Scotia, Illinois, Ohio and Pennsylvania. The Late Pennsylvanian age and paleoenvironmental setting of the El Cobre trackway is consistent with most other records of D. cuithensis.