T79 Undergraduate Research Posters Showcasing Research by 2YC and 4YCU Geoscience Students (Posters)

Sunday, 22 October 2017
9:00 AM - 5:30 PM
Halls 4EF

CLOSING THE TURONIAN-CONIACIAN GAP IN THE GLOBAL RECORD OF IGUANODONTIPODIDAE: NEW SPECIMENS FROM THE CREVASSE CANYON FORMATION, MCKINLEY COUNTY, NEW MEXICO

Paper number: T79-13
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

Abstract

Tracks referable to Iguanodontipodidae are documented from strata spanning the Berriasian to Maastrichtian of Laurasia and South America. However, the record is not continuous, with a notable gap in definitive specimens between the Turonian through Coniacian globally. Here we report on newly discovered ornithopod dinosaur pes tracks from the Coniacian-Santonian-aged Crevasse Canyon Formation, San Juan Basin, New Mexico. A minimum of 13 tracks are preserved as natural casts on a fine-grained sandstone boulder approximately 2.13 by 2.34 meters; no manus prints or tail drags are identifiable. All tracks are tridactyl, mesaxonic, and relatively equidimensional, with a length:width ratio on the best preserved exemplars of 1:1. The majority are similar in size ranging from 27–35 cm in length and 26–34 cm in width. At least five partial trackways can be distinguished representing multiple individuals, one of markedly smaller body size. Based on the subsymmetrical track morphology, 1:1 length/width ratio, presence of gracile digits bearing one digit pad impression that is longer than wide, proximal digit constriction, and single caudally convex heel pad impression, we refer these tracks to Iguanodontipodidae. Long, narrow digit impressions, some bearing sharp termini, and a small heel impression suggest a refined referral to Iguanodontipus; however, the presence of a subtriangular heel impression that is wider than the maximal width of digit III (a diagnostic traits of Caririchnium) prevents us from definitively assigning them to either ichnogenus. Nonetheless, the tracks can clearly be differentiated from Hadrosauropodus, which is to date, the only valid iguanodontipodid ichnogenus recognized from Upper Cretaceous strata of North America. Specimens from the Crevasse Canyon Formation therefore not only fill a key temporal gap in the ornithopod track record globally, they also suggest tracks morphologically similar to the Early Cretaceous ichnogenera Iguanodontipus and Caririchnium and likely derived from early diverging ankylopollexian or styracosternan trackmakers, persist well into the Upper Cretaceous record of North America, overlapping temporally with Hadrosauropodus, which is generally considered to represent the tracks of a more specialized hadrosauroid.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-300534

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