From: Olsen, P. E., and Rainforth, E. C., 2002, Continental tetrapod ichnofaunal sucession and turnover in the Newark Supergroup (?Middle-Upper Triassic and Lower Jurassic, eastern North America) and temporally equivalent strata in Morocco. Journal of Vertebrate Paleontology, v. 22, no. 3, supp., p. 93A-94A.
CONTINENTAL TETRAPOD ICHNOFAUNAL SUCCESSTON AND TURNOVER IN THE NEWARK SUPERGROUP (?MIDDLE-UPPER TRIASSIC AND LOWER JURASSIC, EASTERN NORTH AMERICA) AND TEMPORALLY-EQUIVALENT STRATA IN MOROCCO
OLSEN, Paul E., and RAINFORTH, Emma C., Lamont-Doherty Earth Observatory, Columbia University, 61 Rt. 9W, Palisades, NY 10964.
Three distinct assemblages characterize the >34-million-year track record in the Newark Supergroup and coeval Moroccan strata. The oldest, Atlas-type (Deep River, Moroccan basins), is characterized by numerous Apatopus; unnamed, sometimes very large (>30 cm) ?bipedal tetradactyls; Brachychirotherium; ?Chirotherium; Rhynchosauoides; and far less common indeterminate tridactyls. Grallatorids appear to be absent. Conventionally considered Early-Late Carnian, the strata may extend into the Ladinian.
The Passaic-type assemblage (Dan River, Culpeper, Gettysburg, Newark, Fundy basins; Late Carnian to the Triassic-Jurassic boundary [TJB]) is the most diverse and long-ranging. Theropod prints increase in size and abundance: the small and quite rare Grallator parallellum occurs throughout, but by the end of the Triassic (202 Ma) both Grallator, and the larger Anchisauripus are common. The ornithischian track Atreipus is abundant from the base (~228 Ma) to ~207 Ma but absent thereafter. Other common forms include Rhynchosauroides, Brachychirotherium, Gwynnedichnium and Apatopus; far rarer are Procolophonichnium, Chirotherium and a new dinosaurian genus. The latest Triassic has several batrachopids.
The youngest (Connecticut Valley-type) assemblage (Culpeper, Newark, Hartford, Deerfield, Fundy basins; basal Hettangian [202 Ma] to base of Sinemurian [~200 Ma]) is much less diverse, with only grallatorids, Batrachopus and Rhynchosauroides basally. Eubrontes is an abundant grallatorid, appearing within 10,000 years after the TJB. Above this, the assemblage remains quite stereotyped through the end of the Newarkian record. Grallatorids, Anomoepus and Batrachopus are abundant; Rhynchosauroides and Amheghinichnus are much rarer. In the northern basins, Otozoum is also present and can be common.
Ichnofaunal change is slow through the Late Triassic except at the TJB, where the turnover between Passaic and Connecticut Valley-type assemblages, characterized by a 20% increase in the maximum size of theropod tracks, occurs in <30,000 years. The transition between Atlas and Passaic-type assemblages also seems unusually rapid, but sampling is still too sparse to assess the pace of change.