Jeffrey J. Saunders

Geochelone in Illinois and the Illinoian-Sangamonian vegetation of the type region

Abstract An investigation of Illinoian- and Sangamonian-age deposits in the type region for both Pleistocene stages in central Illinois has yielded a palynological record spanning the Illinoian-Sangamonian boundary associated with an interglacial fauna containing Geochelone crassiscutata. The pollen indicates a shift from high Picea and Pinus to deciduous trees, followed by grass and herbaceous taxa, and finally, a return of deciduous trees. This sequence appears to correlate with marine isotopic stages 6 through 5d. Faunal remains are abundant throughout but megafauna are present only in the interglacial section where Geochelone occurs. The presence of Geochelone suggests above-freezing temperatures in central Ilinois throughout the year during at least the portion of the Sangamonian represented.

Mammuthus Population Dynamics in Late Pleistocene North America: Divergence, Phylogeography, and Introgression

After evolving in Africa at the close of the Miocene, mammoths (Mammuthus sp.) spread through much of the northern hemisphere, diversifying morphologically as they entered various habitats. Paleontologically, these morphs are conventionally recognized as species. In Pleistocene North America alone, several mammoth species have been recognized, inhabiting environments as different as cold tundra-steppe in the north and the arid grasslands or temperate savanna-parklands of the south. Yet mammoth phylogeographic studies have overwhelmingly focused on permafrost-preserved remains of only one of these species, Mammuthus primigenius (woolly mammoth). Here we challenge this bias by performing a geographically and taxonomically wide survey of mammoth genetic diversity across North America. Using a targeted enrichment technique, we sequenced 67 complete mitochondrial genomes from non-primigenius specimens representing M. columbi (Columbian mammoth), M. jeffersonii (Jeffersonian mammoth), and M. exilis (pygmy mammoth), including specimens from contexts not generally associated with good DNA preservation. While we uncovered clear phylogeographic structure in mammoth matrilines, their phylogeny as recovered from mitochondrial DNA is not compatible with existing systematic interpretations of their paleontological record. Instead, our results strongly suggest that various nominal mammoth species interbred, perhaps extensively. We hypothesize that at least two distinct stages of interbreeding between conventional paleontological species are likely responsible for this pattern – one between Siberian woolly mammoths and resident American populations that introduced woolly mammoth phenotypes to the continent, and another between ecomorphologically distinct populations of woolly and Columbian mammoths in North America south of the ice.

Reply to F. E. Green's Comments on the Clovis Site

F. E. Green has corrected errors regarding the provenience and prior determination of the artifactual nature of the ivory semifabricate reported by Saunders et al. (1990) and has brought forth new information regarding the spring deposits of the north bank of the gravel pit at the Clovis site. This statement addresses the contemporaneity of Clovis occupation with deposition of the gray sand and the relation of the gray sand to spring deposits. We offer it in expectation that a better understanding of north-bank stratigraphy and geochronology might result regardless of which of two views of the archaeology of the gray sand eventually prevails.

The Billings Mastodon: A Terminal Pleistocene Locality in Santa Cruz County, Arizona

Skeletal remains of mastodon were found in southern Arizona in 1985. Radiocarbon testing indicates they are of Clovis age, but no artifacts were found. At the time this was the second find of Mammut americanum in Arizona reported with any detail. The find contributes to our knowledge of the Clovis-age genus Mammut in Arizona. It is another example of the extinction the megafauna at the end of the Pleistocene 13,000 cal yr BP.