PRELIMINARY DESCRIPTION OF NON-MAMMOTH PLEISTOCENE FAUNA AT THE WACO MAMMOTH NATIONAL MONUMENT AND A REFINEMENT OF THE PALEOECOLOGICAL CONDITIONS

Waco Mammoth National Monument (WMNM; Waco, TX, USA) is a late Pleistocene fossil site dating to 66.8+- 5.0 ka at the confluence of the Bosque and Brazos rivers. WMNM preserves the only known Mammuthus columbi nursery herd (MNI=18). The mechanisms leading to death/burial of the herd are thought to be a flash flood or drought. A more detailed study of the local paleoenvironment is needed to further investigate these competing hypotheses. M. columbi were migratory and reflect regional conditions, especially grassland habitats, rather than highly localized conditions. Co-occurring taxa with restricted ranges may provide greater detail about rapid changes surrounding death/burial. Here, we include the first comprehensive faunal list, supported by detailed systematic descriptions, which we use to: 1. reevaluate ecological interpretations and; 2. contribute a greater faunal dataset for the interpretations of local environmental conditions during the demise/burial of the nursery herd. Detailed examination of the collections identified at least 20 co-occurring taxa including: Alligator cf. mississippiensis, an anatid, an iguanomorph, Aplodinotus grunniens, a lepisostid, Graptemys sp., Terrapene sp., multiple emydids, a testudinid, Canis latrans, a machairodont, Holmesina cf. sp., Platygonus cf. compressus, Odocoileus virginianus, Capromeryx minor, Camelops hesternus, Bison sp., Equus sp., a leporid, and a Glires incisor.

These taxa provide new insights into the local paleoenvironment that the sites’ mammoths cannot do independently, with the migratory taxa likely attracted to the site in search of resources. Previous work supports a weak NE-SW paleocurrent, rejecting a lentic ecosystem. The presence of: 1. a weak paleocurrent, 2. fishes, alligator, and aquatic turtles, and 3. several invertebrate taxa (mussels and snails) suggest a perennial, slow-moving aquatic ecosystem, such as a tributary or complex active floodplain. This refinement of local conditions, paired with future research, will provide an improved understanding of regional climatic conditions, which currently suggests a potential widespread drought in Texas. The use of multiple proxies may provide the data needed to better understand the conditions surrounding the death and burial of this central Texas Pleistocene community.