New Mexico Geological Society Annual Spring Meeting — Abstracts

The Late Cretaceous (Campanian) Fruitland Formation is widely exposed within the San Juan Basin of northwestern New Mexico and represents deltaic and paludal environments. The Fruitland contains an extensive vertebrate fauna, but there is only one previous report of tetrapod tracks.

The new track is in the collections of New Mexico Museum of Natural History and Science (NMMNH P-7145). This track is preserved in a carbonaceous siltstone from the upper part of the Formation. It is a tridactyl pedal track with a maximum length (through the central digit impression) of 800 mm and a maximum width of 870 mm. There is small, rounded heel impression. The track consists of three, broad digit impressions with blunt tips. The side digit impressions are 750 and 630 mm long.

The majority of North American ichnofaunas from the Late Cretaceous are dominated by ornithopod tracks. NMMNH P-7145 is similar to an ornithopod track in: (1) being wider than long: (2) having wide divarification of the digit impressions; (3) in the length of the middle digit impression not being substantially greater than the side digit impressions; (4) possessing broad digit impressions; and (5) in the tips of the digit impressions being blunt. Hadrosaurs are the only large Campanian ornithopods known from New Mexico and so NMMNH P-7145 presumably represents a hadrosaur. The Fruitland Formation contains the lambeosaurine Parasaurolophus cyrtocristatus and indeterminate hadrosaurines. However, the conservative postcrania of hadrosaurs does not allow the identification of tracks below the family level.