265-8 PAMPATHERE AND OTHER MEGAFAUNA NOVEL TO THE EDWARDS PLATEAU OF TEXAS SUGGEST THAT LATE PLEISTOCENE FOSSILS IN BENDER’S CAVE DATE TO THE LAST INTERGLACIAL (MIS 5).

Session: New Frontiers in Cave and Karst Science (Posters)

Presenting Author:

Authors:

Abstract:

Sampling of Late Pleistocene fossils in 16 caves across the Edwards Plateau of central Texas produced a record of the last glacial interval, Marine Isotope Stage (MIS) 2, that was influential in shaping understanding of Quaternary faunal change in North America. Bender’s Cave, in Comal County, Texas, contains evidence of Late Pleistocene biodiversity that contrasts with the existing regional record. Bender’s Cave is a groundwater conduit system with an underground stream. Vertebrate fossils occur in the cave as an underwater lag assemblage scattered across the stream bed. Polish and abrasion on the fossils indicate a history of fluvial transport and demonstrate that the fossils are in secondary depositional contexts. Fossils recovered represent taxa that are typical of the Rancholabrean Land Mammal Age and common throughout central Texas, including Mammuthus sp., Equus sp., Camelops hesternus, and Bison sp. The ground sloth Megalonyx jeffersonii and a mastodon, Mammutidae indet., also occur in Bender’s Cave but are rare elsewhere in the region. Other fossils provide the first regional records of the pampathere Holmesina septentrionalis and the giant tortoise Hesperotestudo sp.  Megalonyx and Mammutidae indet. were consumers of woody C₃ vegetation, indicating forest habitats. The paleobiogeography of pampatheres and giant tortoises, combined with the ecology of their extant relatives, suggests that these taxa were restricted to relatively warm climatic settings. Those paleoecological inferences are inconsistent with regional paleoenvironmental proxies for MIS 2, which document a relatively open, dry grassland and cool climate. The novel composition of the assemblage may be the product of sample bias and the fossils may be time-averaged, a mix of different temporal intervals. However, these taxa frequently co-occur in Late Pleistocene faunas from other regions of Texas that are interpreted as interglacial, corresponding to MIS 3 or MIS 5. Results of a hierarchical cluster analysis support this association, revealing that among Late Pleistocene sites in Texas, the fauna of Bender’s Cave is most similar to sites dating to the last interglacial, MIS 5. Radiometric age data (¹⁴C and/or U-Th) on bone and associated speleothems is now needed to test the age hypothesized for the fossil assemblage from Bender’s Cave.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10797

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.