DINOSAUR TRACKS AND ASSOCIATED ICHNOFAUNA IN THE LATE TRIASSIC GRATERS MEMBER OF THE PASSAIC FORMATION, SOUTHEASTERN PENNSYLVANIA

The Late Triassic (Norian) Graters Member of the Passaic Formation in southeastern Pennsylvania is known for its abundant reptile footprints. One long-existing yet unreported locality has recently produced not only the typical Newark Basin vertebrate tracks but also a diverse suite of invertebrate traces. The ichnofossils were formed in a lake-shore environment composed of mud-flats and mud affected by shallow water.

Although preservation of the vertebrate tracks is not optimal, some determinations can be made. Tridactyl dinosauromorph tracks found here with a manus present can be referred to the ichnogenus Atreipus. Atreipus may represent an ornithischian dinosaur or a close relative to the dinosaurs. Tracks lacking a manus print could be referable to Atreipus or the small theropod track Grallator. The lepidosauromorph track Rhynchosauroides is very common and easily the most abundant track at this site. Indeterminate swimming reptile tracks are also present.

Arthropod trackways found here are fairly well-preserved and include Diplichnites isp., Camurichnus alternans (Bifurculapes?), and some enigmatic forms, one possibly assignable to Paleohelcura. Invertebrate trails, burrows and feeding traces include Scoyenia and numerous horizontal and vertical traces which are difficult to assign to an ichnotaxon. The arthropod resting trace Rusophycus is present. One bedding plane appears to be covered with insect resting traces of unknown affinity, some showing signs of movement or have associated trails. One clam shrimp impression with an associated trackway was found.