The Northernmost Occurrence of Chelydra serpentina in the eastern US during the Pleistocene

Transcription

1 The Northernmost Occurrence of Chelydra serpentina in the eastern US during the Pleistocene by Chase Doran Brownstein Stamford Museum, Stamford, CT. Abstract. The snapping turtle species Chelydra serpentina, which has a wide range across North America, is extremely tolerant to cold and even freezing conditions. Here, I describe a single caudal vertebrae referred to Chelydra serpentina from the Late Pleistocene of New Jersey which represents the northernmost known occurrence of the species in eastern North America and the closest known occurrence of the species to a glacier or ice sheet in the continent during the Pleistocene. The specimen, which was collected at Ramanessin Brook in Holmdel, New Jersey, affirms that the Pleistocene deposits which line the banks of the popular Cretaceous site are not taphonomically biased to preserving larger fossils and in the future may yield an assemblage of small vertebrates. Introduction. The chelydrids, more commonly known as snapping turtles, are a family of large freshwater turtles that are represented presently by the two genera Chelydra and Macrochelys. The first appearance of this turtle family comes from the Late Cretaceous of Montana (Whetstone, 1978), and extinct species are known from Asia, Europe, and North America (e.g. Pidoplichko & Tarashchuk, 1960; Klein & Mors, 2003; Danilov & Parham, 2008). 22 1

2 The common snapping turtle Chelydra serpentina, to which the vertebra described herein has been referred, is one of only two species of chelydrid which inhabit North America (Ernst, 2008). Chelydra serpentina is a large, robustly built turtle which exhibits an omnivorous diet, and individuals of this species continue to grow throughout their lives (Brooks, Brown & Galbraith, 1991). The skull in C. serpentina is robust with a crushing beak, allowing individuals of the species to catch prey with a powerful bite. This species has an interesting ability to withstand cold temperatures, and individuals have been observed alive at temperatures of -9ºC (Costanzo, Litzgus & Lee, 1999). C. serpentina hatchlings will even remain active in gelid lakes and waterways in order not to come into contact with freezing ice and snow (Ernst, Barbour & Lovich, 1994). Here I describe an isolated chelydrid vertebra referred to C. serpentina that was discovered during a trip by the New York Paleontological Society to Ramanessin Brook in Holmdel, NJ, which often produces fossils from Late Cretaceous strata. The vertebra was eroded from late Pleistocene exposures near the brook, which have previously produced the remains of large terrestrial mammals (Gallagher, 1997). The vertebra is important as it represents the northernmost occurrence of Chelydra in eastern North America and suggests that snapping turtles constituted as part of the near-glacial fauna of Pleistocene northeastern North America. The presence of the vertebra at Ramanessin Brook shows that the Pleistocene deposits which line the brook s banks have the potential to have preserved an assemblage of both large- and smallbodied vertebrates Methods. 2

3 Permits. Permits were obtained by the NYPS to fossil hunt at Ramanessin Brook. Access through an Application and Agreement for use of Township Property form distributed by the Holmdel Township recreation department was given to the New York Paleontological Society to hunt for fossils on May 2, 2015 at the Ramanessin Brook trailhead in Holmdel Park. This was the trip during which the specimen described herein was recovered Institutional Abbreviations. I use the term SM&NC to refer to the Stamford Museum and Nature Center, where the vertebra is currently curated. I use the abbreviation NYPS for the New York Paleontological Society, which scheduled the trip to the brook during which the vertebra described herein was retrieved. I use the term NJSM to refer to the New Jersey State Museum Results. Geological Setting. Ramanessin Brook lies within the Inner Coastal Plain Province of New Jersey, within which are all of the Cretaceous Formations known to outcrop in the state. Almost all of the sediment which lines Ramanessin Brook is Cretaceous in age, though near the top of the banks there are outcrops from the Pleistocene. The brooks of Monmouth county, New Jersey, are known to erode and carry fossils from various Pleistocene deposits which appear on their banks (Gallagher 1997). These brooks usually erode away Cretaceous-age rock and produce fossils such as shark teeth, bivalves, turtles, mosasaurs, plesiosaurs, and dinosaurs. However, on 3

4 occasion the bones of Pleistocene species including the fossils of megafauna such as the giant beaver Castoroides, the American mastodon Mammut americanum, and the elk-moose Cervacles will be found (Gallagher, 1997). In New Jersey, Monmouth County was never directly covered by late Wisconsinan, pre-illinoian or Illionoian glaciations (Witte, 1998). Rather, Monmouth County was a near-glacial ecosystem. The NYPS fossil collecting hunt took place in the Homdel Park portion of Ramanessin Brook which was accessed by means of the Ramanessin Brook trailhead Systematic Paleontology Testudines Batsch 1788 Cryptodira Cope 1868 Chelydridae Gray 1831 Chelydra?serpentina Linnaeus 1758 Material: SM&NC , a complete first caudal vertebra from a snapping turtle worn from being carried by water. Stratigraphy: Wisconsinan/Illionoian deposits along Ramanessin Brook, Holmdel Park, Holmdel Township, New Jersey (~ N, W). Description: SM&NC (fig. 1A-G) is an opisthocoelus caudal vertebra from the base of the tail of a Chelydra serpentina based on its size and overall morphological similarity to basal caudal vertebra of the turtle. The vertebra is mm in length as measured along the lateral surface and 12.7 mm wide as measured along the distal face. In lateral and ventral views a portion of the lower left distal face has been eroded by stream wear and the internal bone 4

5 structure is apparent. The specimen is identified as a fossil from the Pleistocene layers alongside the brook based on the partial mineralization of the specimen. Multiple small cavities are apparent on SMNC , possibly from stream wear Discussion. This vertebra represents the first published report of a snapping turtle from the middle to late Pleistocene of Ramanessin Brook, NJ. The vertebra shows that the large turtle Chelydra was present within the waterways of the near-glacial Monmouth County ecosystem, where such animals may have remained those the waterways through colder winter months or migrated to during the spring and summer. The ability to withstand freezing conditions as witnessed in modern Chelydra individuals (Costanzo, Litzgus & Lee, 1999) would have assisted animals living in near-glacial environments. Today, Chelydra serpentina snapping turtles are known to be omnivorous, consuming not only reptiles, frogs, fish, small mammalians, birds, arthropods, mollusks, and other invertebrates but also terrestrial plant matter (Hartzell, 2015). Pleistocene representatives of the species in New Jersey likely consumed a similar diet. The vertebra is also important as it affirms that the Pleistocene sediments alongside Ramanessin Brook are able to produce smaller specimens of vertebrates in addition to the already documented specimens of megafauna (Gallagher, 1997) and significantly extends the known range of Chelydra during the Pleistocene. A similar site which produced both the remains of large mammals and smaller vertebrates is the well-known Port Kennedy Bone Cave of Pennsylvania s Valley Forge National Historic 5

6 Park (Cope, 1871; Wheatleyi, 8171; Cope, 1895; Mercer, 1895; Mercer, 1899; Cope, 1899; Kurten & Anderson, 1980; Daeschler, Spamer & Parris, 1993). Daeschler, Lamanna & Carfioli (2005) summarized the literature which discussed this significant Pleistocene site and in addition tentatively located the site s location. The cave, in addition to yielding specimens of large carnivores and herbivores such as the giant ground sloth Megalonyx wheatleyi and Smilodon gracilis, has produced the remains of a variety of small mammals and few different species of snakes, turtles, and tortoises (Cope, 1871; Wheatleyi, 8171; Cope, 1895; Mercer, 1895;Mercer, 1899; Cope, 1899; Kurten & Anderson, 1980; Daeschler, Spamer & Parris, 1993; Gallagher, 1997). It is likely that the Pleistocene fauna of Monmouth County was somewhat similar to that at Port Kennedy. However, the common snapping turtle Chelydra serpentina has not been reported from the latter site. The closest locations to Holmdel Park from which Pleistocene remains of C. serpentina have been reported are from southern Maryland and both northern and southern Virginia (Lucas, 1906; Wetmore, 1962; Ray & Cooper, 1967). This makes SM&NC the northernmost occurrence of the snapping turtle genus Chelydra in eastern North America. Importantly, Chelydra remains were reported from the Pleistocene of western Nebraska at the Lisco Locality (Schultz & Stout, 1948), which, at 41.4 degrees latitude is slightly to the north of Holmdel Park, New Jersey at north. This site is from the Blancan North American faunal stage (Schultz & Stout, 1948) of the late Pliocene to early Pleistocene. The Nebraska Blancan Chelydra therefore might not have been as close to ice sheets or glaciers as the Holmdel specimen, which would have been within 40 kilometers of late Wisconsinan and Illionain glaciations (Witte, 1998, fig. 2). Chelydra serpentina would therefore have been a component of near-glacier fluvial and lacustrine ecosystems during the middle or late Pleistocene. 6

7 Conclusions. SM&NC represents the northernmost occurrence of Chelydra serpentina in the northeastern US and the closest occurrence of the species to a Pleistocene glacier. The vertebra adds to the known Pleistocene fauna of Ramanessin Brook and affirms that the Pleistocene exposures which line the brook preserved both larger and smaller vertebrates Acknowledgements. I would like to acknowledge Kirsten Brophy, curator of collections at the SM&NC, for taking the pictures of the vertebra used in figure 1. I would like to thank David Parris of the New Jersey State Museum for providing feedback on the identity of the vertebra, to the New York Paleontological Society for scheduling the fossil hunting trip during which the vertebra described herein was recovered, and to Donald Phillips of the NYPS for providing information on the permits. Lastly, I would like to thank Jason Schein of the NJSM for his comments on the specimen. References. Whetstone KN A new genus of cryptodiran turtles (Testudinoidea, Chelydridae) from the Upper Cretaceous Hell Creek Formation of Montana. Univeristy of Kansas Science Bulletin 51(17): Pidoplichko IG & Tarashchuk BI New genus of large-headed (macrocephalous) turtle from the Pontion beds in the environs of Odessa. Zbirn Prats Zool Mus Akad USSR 29:

8 Klein N & Mors T Die Schildkroten (Reptilia: Testudines) aus dem Mittel-Miozan von Hambach (Niederrheinische Bucht, NW-Deutschland). Palaeontographica Abteilung A 268(1-3): Danilov G & Parham JF A reassessment of some poorly known turtles from the Middle Jurassic of China, with comments on the antiquity of extant turtles. Journal of Vertebrate Paleontology 28(2): Brooks RJ, Brown GP & Galbraith DA Effects of a sudden increase in natural mortality of adults on a population of the common snapping turtle (Chelydra serpentina). Canadian Journal of Zoology 69(5): Costanzo, J. P., J. D. Litzgus and R. E. Lee Behavioral responses of hatchling painted turtles (Chrysemys picta) and snapping turtles (Chelydra serpentina) at subzero temperatures. Journal of Thermal Biology 24, Ernst CH, Barbour RW & Lovich JE Turtles of the United States and Canada. Washington DC: Smithsonian Institution Press Gallagher WB When Dinosaurs Roamed New Jersey. New Brunswick: Rutgers University Press. pp

9 Witte RW Glacial Sediment and the Ice Age in New Jersey. New Jersey Geological Survey Information Circular Cope ED Preliminary report on the Vertebrata discovered in the Port Kennedy bone cave. Proceedings of the American Philosophical Society 12: Wheatley CM Notice of the discovery of a cave in eastern Pennsylvania, containing remains of Post-Pliocene fossils, including those of mastodon, tapir, megalonyx, mylodon, etc. The American Journal of Science and Arts 1(4): Cope ED The fossil Vertebrata from the fissure at Port Kennedy, Pennsylvania. Proceedings of the Academy of Natural Sciences of Philadelphia 47: Mercer HC A preliminary account of the re-exploration in 1894 and 1895 of the Bone Hole, now known as Irwins Cave, at Port Kennedy, Montgomery County, Pennsylvania. Proceedings of the Academy of Natural Sciences of Philadelphia 47: Cope ED New and little known Mammalia from the Port Kennedy bone deposit. Proceedings of the Academy of Natural Sciences of Philadelphia 48: Mercer HC The Bone Cave at Port Kennedy, Pennsylvania, and its partial excavation in 1894, 1895, and Journal of the Academy of Natural Sciences of Philadelphia 11:

10 Cope ED Vertebrate remains from Port Kennedy bone deposit. Journal of the Academy of Natural Sciences of Philadelphia 11: Kurten B & Anderson E Pleistocene mammals of North America. Columbia University Press: New York City Daeschler E, Spamer EE & Parris DC Review and new data on the Port Kennedy local fauna and flora (Late Irvingtonian), Valley Forge National Historical Park, Montgomery County, Pennsylvania. The Mosasaur 5: Daeschler EB, Lamanna MC & Carfioli M On the Trail of an Important Ice Age Fossil Deposit: Rediscovering the Port Kennedy Cave (Middle Pleistocene), Valley Forge National Historical Park, Montgomery County, Pennsylvania. Park Science 23(2): Lucas FA The elephants of the Pleistocene; Mammalia. Maryland Geological Survey Wetmore A Notes on fossil and subfossil birds. Smithsonian Miscellaneous Collections 145(2): Ray CE & Cooper BN Fossil mammals and pollen in a late Pleistocene deposit at Saltville, Virginia. Journal of Paleontology 41(3):

11 Schultz CB & Stout TM Pleistocene mammals and terraces in the Great Plains. Geological Society America Bulletin 59: