THE FOOTPRINT RECORD OF EARLY JURASSIC DINOSAURS IN THE CONNECTICUT VALLEY: STATUS OF THE TAXON FORMERLY KNOWN AS BRONTOZOUM

RAINFORTH, E. C. (2004)

Edward Hitchcock’s studies of fossil footprints from the Connecticut Valley (Early Jurassic, Newark Supergroup) include some of the earliest descriptions of dinosaurs from North America, although they were not recognized as such until several years after his death. Well-preserved dinosaurian ichnotaxa attributed to dinosaurs include the ornithischian Anomoepus (and several junior synonyms), the prosauropodan Otozoum, and the theropodan Grallator, Eubrontes, Gigandipus and Hyphepus. Later authors described Otouphepus (Cushman) and Anchisauripus (Lull) from the same strata. The taxonomy of the footprints attributed to theropods is particularly confused, with numerous synonymies and mis-identification of type specimens leading to errors in later taxonomic revisions. Most of the species currently contained within Grallator, Anchisauripus and Eubrontes were formerly referred to the 1847 genus Brontozoum (an objective junior synonym of Eubrontes 1845), from which Grallator was separated in 1858. Recent work suggests that these three taxa should be subjectively synonymized; Eubrontes has priority. The informal term brontozoid is introduced to encompass all tridactyl prints of this general morphology, harkening back to the original concept of Brontozoum. Anchisauripus was defined as being intermediate in most aspects between Grallator and Eubrontes, differing by having a hallux impression. However in instances where the hallux has not been previously refuted, it is clear that this feature – consisting of small triangular indentations separated from the body of the track – is actually an under-claw print transmitted from a higher level; all such occurrences are on shales from the Lily Pond quarry. Gigandipus and Hyphepus are large and small brontozoids respectively, with both hallux and tail impressions; in all other respects they are very similar to Eubrontes and Grallator/Anchisauripus. The hallux impressions are clearly attached to the rest of the foot, and prints with this hallux are always accompanied by a tail drag mark. These genera are apparently behavioral variants on the brontozoid morphology, and it is suggested they be synonymized with Eubrontes. The tail and hallux impressions justify the retention of the species caudatus for all the material previously included in Hyphepus and Gigandipus.

Geological Society of America, Abstracts with Programs, 36 (2):96.