THE FISH TRAIL UNDICHNA FROM PLAYA LAKE DEPOSITS OF THE HARTFORD BASIN (EARLY JURASSIC EAST, BERLIN FORMATION) OF MASSACHUSETTS: IMPLICATIONS FOR EARLY JURASSIC TERRESTRIAL FOOD CHAINS

After dinosaur tracks, fish are the most abundant fossils in the Early Jurassic Hartford and Deerfield Basins of Connecticut and Massachusetts. Considering that the dinosaur ichnofaunas are concentrated in the lake-margin sediments and that tracks of carnivorous dinosaurs are much more abundant than those of herbivores, some researchers have proposed that the terrestrial food chain was based on fish, rather than on herbivores. One problem for this hypothesis is that fish fossils (body or trace) are rare in the shallow lacustrine sediments in which the dinosaur tracks occur. Recently, however, Benner and de Gilbert (2009) reinterpreted the type specimen of the ichnospecies Cochlea archimedea, which was erected by Edward Hitchcock in the 19^th century, as a fish trace. A second occurrence of fish trails is reported here. These trails, called Undichna, were discovered in red, muddy sandstone of the East Berlin Formation in Holyoke, Massachusetts. They were produced in a playa lake, indicating that fish temporarily lived in these ephemeral bodies of water, rather than washing in dead. The co-occurrence of these trails with theropod tracks supports the hypothesis that, with the relative rarity of herbivores, fish could have served as the base of the Early Jurassic terrestrial food chain, even in times of drier climate.