LATE TRIASSIC TRACKS REINTERPRETED AT GETTYSBURG NATIONAL MILITARY PARK

BY VINCENT L. SANTUCCI AND ADRIAN P. H UNT tracks has advanced signifi- ONG BEFORE THE FOOTSTEPS OF UNION cantly over the past two decades and confederate soldiers traversed and we are now able to offer a Lsouth-central Pennsylvania, early di- different interpretation of the nosaurs left their footprints in ancient mud. Gettysburg tracks. The fossil Fossilized tracks preserve evidence that di- tracks represent the ichnogenus nosaurs existed in the Gettysburg area over Atreipus which was first de- 200 million years ago during a time period scribed by Olsen and Baird in called the Triassic. The tracks also illustrate 1986. The tracks can be further another example of a NPS unit, primarily identified to the ichnospecies A. focused on cultural resources, that must face mil-fordensis. the challenges of managing and interpret- Atreipus milfordensis repre- ing paleontological resources. sents, as of yet, an undescribed The dinosaur tracks are preserved in dinosaur that exhibits a thero- blocks of mudstone that were quarried from podlike pes (foot) in combina- Figure 1. Fossil and pes tracks of Atreipus an area outside park boundaries. However, tion with a short-clawed and milfordensis from atop a stone bridge at Gettysburg the quarried blocks were transported to the functionally tridactyl (three- National Military Park, Pennsylvania. park and used in the construction of stone toed) manus (hand). The track bridges during the 1930s. In 1937, over 50 pattern indicates that this dinosaur habitu- Additionally, as with the Gettysburg fos- additional tracks were discovered in blocks ally used all four limbs in locomotion. The sils, tracks can yield information about ani- from another nearby quarry within Adams manus track is incompatible with any mals that are not yet known from skeletal County. The park superintendent at that known theropod (carnivorous, upright di- material. The presence of early dinosaur time was especially interested in the nosaurs like Tyranosaurs, that usually have tracks at Gettysburg provides park rangers and placed some on display within the park. small forelimbs). Thero-pods have large with the opportunity to interpret the local He encouraged interpretation of the tracks trenchant manus claws that are designed history well before the fateful days in July and unofficially coordinated distribution of for grasping, not walking. This pattern of 1863. P some specimens to the Smithsonian Insti- manus and pes tracks is unusual and a con- S tution, Carnegie Museum of Natural His- dition not exhibited in any other described tory in Pittsburgh, and the State Museum dinosaur tracks. LITERATURE CITED of Pennsylvania in Harrisburg. Today, the The tracks are recognized as dinosau- Olsen, P.E., and D. Baird. 1986. The ichnogenus Atreipus tracks are informally monitored by park rian because of the birdlike tridactyl pat- and its significance for Triassic biostratigraphy. Pages 61-87 in K. Padian, editor. The beginning of the age of rangers and are interpreted by rangers and tern of the pes track (fig.1). This pattern, . Cambridge University Press, New York. concessioners alike. represented in the foot skeleton, is a de- Santucci, V.L., and A.P. Hunt. 1993. Late Triassic Altogether, tracks are known from two rived character for dinosaurs. Olsen and tracks discovered at Petrified Forest National Park. Park localities in Gettysburg Basin, the Trostle Baird (1986) suggest that Atreipus may Science 13(4):14. Quarry in Adams County, and a smaller represent the track of a very early ornithis- quarry near Goldsboro in York County. All chian (-hipped) dinosaur. Vince Santucci is a former NPS Park were discovered in the Late Triassic Late Triassic tracks are also known from Ranger and resource manager now Gettysburg Shale, a rock formation that also Dinosaur National Monument and Petri- teaching parks & recreation management, occurs within the park. These deposits were fied Forest National Park (Santucci & Hunt interpretive methods, law enforcement, and general resource management in the laid down in a gradually deepening trough 1993). The Late Triassic was the phase of Department of Parks and Recreation at of sediments that comprise the Newark Su- vertebrate history in which the dinosaurs Slippery Rock University, Slippery Rock, pergroup. first originated. Research investigations re- PA 16047. Adrian Hunt is a Vertebrate The park files at Gettysburg National garding fossil tracks provide information Paleontologist in the Department of Military Park identify these fossil tracks as not available solely through the study of Geology, University of Colorado at Denver, Grallator and Anchisauripus. However, these fossil bones and teeth. Tracks and track- Denver, CO 80217. identifications are based upon interpreta- ways can yield information about behav- tions recognized in the 1930s. Research into ior, locomotion, and paleoecology.

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