NEW INVESTIGATIONS OF THE AGE AND DIVERSITY OF LATE PLEISTOCENE VERTEBRATE FOSSILS FROM INNER SPACE CAVERN ON THE EDWARDS PLATEAU OF TEXAS

Inner Space Cavern (ISC; aka Laubach Cave) is a show cave in the Edwards Limestone of Texas with a rich Pleistocene record. Investigations in the 1960s documented vertebrate remains within debris/talus cone deposits associated with now-closed sinkholes. Variation in faunal composition and three whole-bone radiocarbon ages suggested that the debris cones developed asynchronously and may, together, form a composite sequence documenting millennia of the late Pleistocene. A paleoclimatic signal is preserved in cave speleothems and the stable temperature and moisture conditions are conducive to the preservation of bone collagen. These faunal, abiotic, and radiocarbon resources suggest that ISC is a natural lab, readymade to explore ecosystem dynamics prior to late Pleistocene extinctions.

I have systematically sampled deposits containing late Pleistocene fossils throughout ISC to delineate patterns of diversity, date individual taxa, and test hypotheses regarding faunal change and the age of associated deposits. Despite the sheltered setting of the cave, my initial attempts to obtain radiocarbon ages on collagen have, so far, proved unsuccessful. Ongoing radiocarbon analyses seek to clarify if collagen loss is typical of the fossil remains or is limited to certain deposits, taphonomic settings, or skeletal elements. The new samples expand the faunal record of the cave with many salamander (Ambystomatidae), reptile (e.g., Anguidae, Hesperotestudo sp.), bird (e.g., Columbidae, Odontophoridae, Accipiter sp.), and extinct mammal taxa (e.g., Capromeryx furcifer, Camelidae) recorded for the first time. Those samples reveal that some differences in faunal composition between deposits sampled in the 1960’s were the product of sampling biases, not faunal change. Other taxonomic distinctions between deposits persist. Remains of bats (Myotis sp., Molossidae) appear to document changes in species diversity through time. Molossid samples associated with a sequence of cave breakdown provide the opportunity to study colony demographics and, potentially, migratory dynamics in the late Pleistocene. Still, the implications of these fossils and their capacity to improve our understanding of extinctions in the late Pleistocene are constrained by an ongoing lack of clarity regarding their precise age.