Steven C. Wallace

Two new carnivores from an unusual late Tertiary forest biota in eastern North America

Late Cenozoic terrestrial fossil records of North America are biased by a predominance of mid-latitude deposits, mostly in the western half of the continent. Consequently, the biological history of eastern North America, including the eastern deciduous forest, remains largely hidden. Unfortunately, vertebrate fossil sites from this vast region are rare, and few pertain to the critically important late Tertiary period, during which intensified global climatic changes took place. Moreover, strong phylogenetic affinities between the flora of eastern North America and eastern Asia clearly demonstrate formerly contiguous connections, but disparity among shared genera (eastern Asia–eastern North America disjunction) implies significant periods of separation since at least the Miocene epoch. Lacustrine sediments deposited within a former sinkhole in the southern Appalachian Mountains provide a rare example of a late Miocene to early Pliocene terrestrial biota from a forested ecosystem. Here we show that the vertebrate remains contained within this deposit represent a unique combination of North American and Eurasian taxa. A new genus and species of the red (lesser) panda (Pristinailurus bristoli), the earliest and most primitive so far known, was recovered. Also among the fauna are a new species of Eurasian badger (Arctomeles dimolodontus) and the largest concentration of fossil tapirs ever recorded. Cladistical analyses of the two new carnivores strongly suggest immigration events that were earlier than and distinct from previous records, and that the close faunal affinities between eastern North America and eastern Asia in the late Tertiary period are consistent with the contemporaneous botanical record.

Cranial Morphology and Systematics of an Extraordinary Sample of the Late Neogene Dwarf Tapir, Tapirus polkensis (Olsen)

Abstract The previously poorly known “Tapiravus” polkensis Olsen, 1960 (Mammalia, Perissodactyla, Tapiridae) is now known from abundant, well preserved specimens from both the type area in central Florida and from the Gray Fossil Site (GFS) in eastern Tennessee. The latter has produced over 75 individuals, the greatest number of tapirids from a single fossil site, including many articulated skeletons. Almost all linear measurements taken on skulls, mandibles, and cheek teeth from GFS have coefficients of variation less than 10 (most between 3 and 7), indicating the presence of a single species. However, the sample reveals considerable intraspecific variation for a few key morphologic features, including development of the sagittal crest, outline shape of the nasals, and number and relative strength of lingual cusps on the P1. The Florida sample of T. polkensis is more limited, but has the same state as the GFS sample for all preserved characters of systematic significance, and while the Florida teeth are on average smaller (especially narrower lower cheek teeth), they fall either within or just below the observed range of the Gray Fossil Site population. The new material supports a reassignment of “Tapiravus” polkensis to the genus Tapirus, and demonstrates that the geologic age of the species is significantly younger than previously thought, Hemphillian rather than Barstovian. Tapirus polkensis is the smallest known North American Tapirus, and smaller than any of the extant species in the genus, with an estimated average mass of 125 kg.

Helodermatid Lizard from the Mio-Pliocene Oak-Hickory Forest of Tennessee, Eastern USA, and a Review of Monstersaurian Osteoderms

The extant venomous Gila monster and beaded lizards, species of Heloderma, live today in southwestern USA and south along the Pacific coastal region into Central America, but their fossil history is poorly understood. Here we report helodermatid osteoderms (dermal ossicles) from the late Miocene-early Pliocene Gray Fossil Site, eastern Tennessee USA. Twenty-three species of mammals are known from the fauna including abundant Tapirus polkensis, as well as fishes, anurans, salamanders, turtles, Alligator, birds, and snakes. Beaded lizards belong to the Monstersauria, a clade that includes Primaderma + Paraderma + Gobiderma + Helodermatidae (Estesia, Eurheloderma, Lowesaurus, and Heloderma). Osteoderms of lizards in this clade are unique within Squamata; they typically are circular to polygonal in outline, domed to flat-domed in cross-section, have a vermiculate surface texture, are not compound structures, and do not have imbricate surfaces as on many scincomorph and anguid lizards. We review and characterize the osteoderms of all members of Monstersauria. Osteoderms from the cranium, body, and limbs of Heloderma characteristically have a ring-extension (bony flange) at least partly surrounding the dome. Its presence appears to be a key character distinct to all species of Heloderma, consequently, we propose the presence of a ring-extension to be an apomorphy. Three osteoderms from the Gray Fossil Site range from 1.5 to 3.0 mm in diameter, have the circular shape of helodermatid osteoderms with a domed apical surface, and have the ring-extensions, permiting generic identification. Macrobotanical remains from the Gray Fossil Site indicate an oak-hickory subtropical forest dominated by Quercus (oak) and Carya (hickory) with some conifer species, an understorey including the climbing vines Sinomenium, Sargentodoxa, and Vitis. Plant and mammal remains indicate a strong Asian influence.

DIFFERENTIATING MICROTUS XANTHOGNATHUS AND MICROTUS PENNSYLVANICUS LOWER FIRST MOLARS USING DISCRIMINANT ANALYSIS OF LANDMARK DATA

Abstract The distinct ecological requirements of Microtus xanthognathus (yellow-cheeked vole or taiga vole) and M. pennsylvanicus (meadow vole) warrant accurate discrimination of their remains in studies of paleoecology and past biogeographical shifts. An occlusal length of the lower 1st molars (m1) that is >3.2 mm for M. xanthognathus is the method most frequently used to separate these 2 taxa in archaeological and paleontological samples. However, these measurements alone are unreliable because some specimens of M. pennsylvanicus overlap smaller individuals of M. xanthognathus in size. Therefore, I created and tested a morphometric technique that discriminates Recent lower 1st molars (m1s) of M. pennsylvanicus from those of M. xanthognathus, and is applicable to other taxa (both modern and fossil). Despite overlapping occlusal length, my discriminant function based on landmark data correctly classified 100% (n = 53) of Recent m1s from the 2 taxa and 97.7% (43 of 44) of (assumed) m1s of M. pennsylvanicus from an archaeological site from about AD 1200 in central Nebraska. This landmark scheme is applicable to fossil and modern Microtus worldwide.

Investigation into the Paleobiology of Dasypus bellus Using Geometric Morphometrics and Variation of the Calcaneus

The extinct taxon Dasypus bellus has long been considered identical to the extant Dasypus novemcinctus osteologically when disregarding allometric differences. In this study, we undertake a preliminary investigation into this extinct taxon and an extant relative D. novemcinctus, by comparing the calcanea of these two dasypodids. Clear osteological differences are observed including a mediolaterally-reduced facet region, an anteriorly-shortened calcaneal head, a reduced peroneal process, and a curved and dorsoventrally-shortened calcaneal foot in D. bellus. Such characters are not allometric and likely correlate to distinct behavioral differences. Specifically, we suggest that D. novemcinctus maintains a more fossorial lifestyle, while the larger D. bellus was likely more terrestrial, with potentially little digging behavior. Such lifestyle differences could not only explain the osteological differences present, but also why fossils of D. bellus have been recovered farther north than the present range of D. novemcinctus. Fossils of Dasypus may need to be re-evaluated to determine how these two taxa relate temporally and geographically, which may have further implications regarding some past interpretations and provide new details on the behavior and potential relationships between these (and other) xenarthrans.

A New Machairodont from the Palmetto Fauna (Early Pliocene) of Florida, with Comments on the Origin of the Smilodontini (Mammalia, Carnivora, Felidae)

South-central Florida’s latest Hemphillian Palmetto Fauna includes two machairodontine felids, the lion-sized Machairodus coloradensis and a smaller, jaguar-sized species, initially referred to Megantereon hesperus based on a single, relatively incomplete mandible. This made the latter the oldest record of Megantereon, suggesting a New World origin of the genus. Subsequent workers variously accepted or rejected this identification and biogeographic scenario. Fortunately, new material, which preserves previously unknown characters, is now known for the smaller taxon. The most parsimonious results of a phylogenetic analysis using 37 cranio-mandibular characters from 13 taxa place it in the Smilodontini, like the original study; however, as the sister-taxon to Megantereon and Smilodon. Accordingly, we formally describe Rhizosmilodon fiteae gen. et sp. nov. Rhizosmilodon, Megantereon, and Smilodon ( =  Smilodontini) share synapomorphies relative to their sister-taxon Machairodontini: serrations smaller and restricted to canines; offset of P3 with P4 and p4 with m1; complete verticalization of mandibular symphysis; m1 shortened and robust with widest point anterior to notch; and extreme posterior “lean” to p3/p4. Rhizosmilodon has small anterior and posterior accessory cusps on p4, a relatively large lower canine, and small, non-procumbent lower incisors; all more primitive states than in Megantereon and Smilodon. The former also differs from Megantereon and Smilodon gracilis by having a very small mandibular flange. Rhizosmilodon is the oldest known member of the Smilodontini, suggesting that the tribe originated in North America. Two more derived, similar-sized species evolved in parallel during the Blancan, Megantereon hesperus and Smilodon gracilis. The former is rarer, known only from the north-central and northwestern US, and presumably dispersed into the Old World. The latter is known from the eastern and southern US, and dispersed into South America.

Chapter 4 – Advanced Members of the Ailuridae (Lesser or Red Pandas – Subfamily Ailurinae)

Publisher Summary This chapter deals with the advanced members of Ailuridae. A side from a few well-represented taxa such as Simocyon batalleri and Pristinailurus bristoli, the fossil record of the Ailuridae consists of mostly isolated teeth and fragmentary specimens. However, these two taxa are beginning to shed new light on this group of specialized carnivorans. The selection of the various dental characters appears to have been mosaic, with different teeth specializing at different rates (and with different focal zones). In addition, some forms specialized in hypercarnivory, while others were becoming adapted to hypocarnivory to varying degrees. It is quite likely that Simocyons move to the trees may have directly led to the selection of features which allowed this group to exploit flowers and/or fruit (in addition to eating meat), and therefore hypocarnivory may have been a direct result of this change in lifestyle. Moreover, it appears that although both living “pandas” use their so-called “falsethumb” for feeding, each lineage acquired this unique trait via different pathways—one for feeding and one for climbing—making this one of the most fascinating examples of convergent evolution. Lastly, as demonstrated by Pristinailurus bristoli, not every member of this group remained arboreal, which may have reduced its ability to compete with other more generalized omnivores, and ultimately to the extinction of nearly every member of this group.

Geometric Morphometrics of Dentaries in Myotis: Species Identification and Its Implications for Conservation and the Fossil Record

Abstract Dentaries of 6 species of Myotis from eastern North America were analyzed, using landmark-based geometric morphometrics, and were distinguished with 83.3% accuracy, although sexes were poorly discriminated using this technique. Fossils of Myotis from Bat Cave, KY, were studied in an attempt to identify these specimens to species level. Southeastern Bats and endangered Indiana Bats dominated the fossil sample, with some Eastern Small-footed Bats and endangered Gray Bats. Such results demonstrate the ability to differentiate Myotis from historic and prehistoric sites and provide a tool for researchers to understand and potentially to conserve these species.

Phylogenetics of Panthera, including Panthera atrox, based on craniodental characters

The phylogenetic position of Panthera atrox within Felidae is still controversial despite many morphological and molecular studies addressing its relationships. This is in part due to the lack of consensus on a tree for Panthera. These inconsistencies suggest the need for further analysis and perhaps even different methodology to better understand pantherine evolution. Morphologic characters from the skull and dentary were analysed within Panthera to elucidate pantherine phylogeny. Extant taxa included Panthera leo (African lion), Panthera tigris (tiger), Panthera onca (jaguar), Panthera pardus (leopard), Uncia uncia (snow leopard) and Neofelis nebulosa (clouded leopard). Four outgroups were used: Crocuta crocuta (spotted hyena), Metailurus spp., Proailurus lemanensis and Pseudaelurus validus. Our study found a clade containing Panthera leo, Panthera tigris and Panthera atrox, suggesting that Panthera atrox is more closely related to the African lion and the tiger than the jaguar, in contrast to what has been recently proposed. Moreover, gross morphological similarities between Panthera atrox and Panthera onca are more likely the result of convergent hunting styles and/or prey selection, rather than phylogenetic affinity.

A new species of Gulo from the Early Pliocene Gray Fossil Site (Eastern United States); rethinking the evolution of wolverines

The wolverine (Gulo gulo) is the largest living terrestrial member of the Mustelidae; a versatile predator formerly distributed throughout boreal regions of North America and Eurasia. Though commonly recovered from Pleistocene sites across their range, pre-Pleistocene records of the genus are exceedingly rare. Here, we describe a new species of Gulo from the Gray Fossil Site in Tennessee. Based on biostratigraphy, a revised estimate of the age of the Gray Fossil Site is Early Pliocene, near the Hemphillian—Blancan transition, between 4.9 and 4.5 Ma. This represents the earliest known occurrence of a wolverine, more than one million years earlier than any other record. The new species of wolverine described here shares similarities with previously described species of Gulo, and with early fishers (Pekania). As the earliest records of both Gulo and Pekania are known from North America, this suggests the genus may have evolved in North America and dispersed to Eurasia later in the Pliocene. Both fauna and flora at the Gray Fossil Site are characteristic of warm/humid climates, which suggests wolverines may have become ‘cold-adapted’ relatively recently. Finally, detailed comparison indicates Plesiogulo, which has often been suggested to be ancestral to Gulo, is not likely closely related to gulonines, and instead may represent convergence on a similar niche.