ANTIPUS FLEXILOQUUS – THE EARLIEST PTEROSAUR TRACKS FROM NORTH AMERICA?

Antipus flexiloquus Hitchcock 1858 was named for material from the Early Jurassic Turners Falls Formation on Roswell Field's property in Gill, Mass. While 2 specimens were identified by Hitchcock, only one (AC 41/52) actually bears the species; the prints on the second slab (AC 35/25) are indeterminate and unidentifiable. The ichnospecies consists of a quadrupedal trackway of leptodactylous prints (a preservational style in which digits are narrow and lack phalangeal pads). The pes is tetradactyl, the manus pentadactyl, somewhat resembling Batrachopus. Unlike Batrachopus, which is attributed to a crocodylomorph, the trackway is extremely wide, and the manus is rotated outwards so that the axis of digit III is oriented slightly posterolaterally (and digit IV approximately 135° from the midline); this is consistent with ichnites that are considered pterosaurian. The trackway includes both walking and resting traces and ends abruptly (although the slab continues) – perhaps the trackmaker flew away?

Whilst pterosaurs are known from the Late Triassic of Europe, the oldest pterosaur tracks (other than A. flexiloquus) are known from the Late, or possibly Middle, Jurassic of western North America and Europe; however, A. flexiloquus, if pterosaurian, would be the oldest pterosaur tracks known to date. Ironically, the specimen was collected a century prior to the better-known material from Europe and the American west, although it has received little study. Hitchcock suggested the trackmaker may have been a lizard, turtle or salamander; Coombs (the only other worker to have looked at this species) suggested a lizard or crocodile affinity, based on similarity to prints now considered pterosaurian.