Ichnotaxonomy of the fossil footprints of the Connecticut Valley (Early Jurassic, Newark Supergroup, Connecticut and Massachusetts)

From 1836 to 1865, Edward Hitchcock named 94 ichnogenera and 216 ichnospecies (including unjustified emendations), in a total of 269 combinations. After a comprehensive examination of all syntypes, ichnospecies, and ichnogenera, tracing both objective and subjective synonymies, 71 ichnogenera and 185 ichnospecies are valid. It is likely that this number can be reduced significantly in the future by subjective synonymization. Type ichnospecies are designated for six ichnogenera not previously typified. Lectotypes are designated for 75 ichnospecies, all of which had previously (C. H. Hitchcock 1865; Cushman 1904; Lull 1904a, 1915, 1953) had lectotypes invalidly designated. Five neotypes are designated.; Hitchcock's (1836--1865) classification of Ornithichnites into Leptodactyli and Pachydactyli (slender- and thick-toed respectively) is considered to be a taphonomic rather than biologic division. For trackmaker identification and subsequent biostratigraphic analysis, the Pachydactyli are more useful. The ornithischian Pachydactyli have recently been re-evaluated (Olsen and Rainforth 2003); the theropodan Pachydactyli (Eubrontes ispp.) require major revision and are expected to be valuable for high-resolution biostratigraphy in the Newark Supergroup.; Otozoum moodii (Hitchcock 1847) is one of the classic Connecticut Valley ichnotaxa. It is redescribed, and AC 4/1a re-established as the holotype. O. minus and O. caudatum are synonymized with O. moodii. The syntypes of Kalosauropus pollex are described as O. pollex sp. nov.; K. masitisii is considered a nomen dubium. Cladistic, quantitative, and comparative methods of trackmaker identification suggest that Otozoum was a prosauropod print. In quantitative analyses, only those phalanges likely to contribute to footprint morphology were considered; claws were excluded owing to their variable impression. Several diagnostic characters distinguish Otozoum from Brachychirotherium, Chirotherium, Batrachopus, Tetrasauropus, and Pseudotetrasauropus ; these ichnotaxa were probably made by crurotarsans. Otozoum is found primarily in Hettangian strata of the Hartford, Deerfield, and Fundy basins (eastern North America); it is also present in the Early Jurassic Navajo Sandstone (Colorado Plateau, USA) and Clarens Formation (Lesotho). It is unknown in older strata; Triassic material previously referred to Otozoum (including O. grandcombensis) instead belongs in Pseudotetrasauropus. Correlation of sediments and comparison of faunal assemblages, particularly within the Newark Supergroup, suggest that the Otozoum trackmakers were restricted to quite arid environments.