118 D24. Paleontology: Phylogenetic/Morphological Patterns (Posters)

Monday, 23 September 2019
9:00 AM - 6:30 PM
Hall AB, North Building

ICHNOTAXA DETERMINATION OF A TRIDACTYL TRACKWAY FROM THE LATE TRIASSIC-AGED PASSAIC FORMATION (NEWARK SUPERGROUP) OF BLAUVELT, ROCKLAND COUNTY, NEW YORK USING 2D GEOMETRIC MORPHOMETRICS AND 3D PHOTOGRAMMETRY

Paper number: 118-31
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

A poorly-preserved tridactyl trackway from the Late Triassic-Aged Passaic Formation (Newark Supergroup) of Blauvelt, Rockland County, New York has been assigned to either Grallator or Atreipus by previous workers. The tracks were studied using 2D geometric morphometrics and 3D photogrammetry to help determine the appropriate ichnogenus assignment. The results of a principal component analysis (PCA) were inconclusive and showed greater clustering of Atreipus and Grallator from the literature compared to the unnamed specimen from Blauvelt. Ellipses surrounding data points for Atreipus and Grallator from the literature showed minor overlap with each other. The ellipse surrounding data points for the unnamed specimen showed overlap with neither, which can be explained by one of the following: the unnamed specimen belongs to neither the ichnogenus Atreipus, nor Grallator or that a disparity in the level of preservation among specimen used in the morphometric portion of this study led to skewed results. A numerical scale for M-preservation as defined in the literature will be employed to further examine both of these possibilities. Depth maps created in ArcMap revealed strong evidence for a positive identification of Atreipus in the form of possible manus impressions, which were of consistent size and depth as well as in a location consistent with those observed in the literature. These possible manus impressions are barely recognizable in the surface of the slab, an attribute consistent with the ichnogenus Atreipus, of which the manus more rarely preserved as compared to the pes. Additional distinctive characteristics indicative of Atreipus are the absolute measurements of the digit III and the total width. Despite the presence of possible manus impressions and dimensional measurements characteristic of Atreipus, the unnamed specimen should be referred to as nomina dubia until the discrepancy in the PCA is explored further.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-337917

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