Matthew C Mihlbachler

• Ph.D.
• New York Institute of Technology

Several scenarios have been proposed to explain rapid net size increases in some early Cenozoic mammalian lineages: sustained and gradual directional change, successive occupation of adaptive zones associated with progressively larger body sizes, and nondirectional evolution associated with branching events in combination with higher diversificatio...

Mesowear is a dietary proxy that relates attritive wear and abrasive wear to the shape of worn tooth cusps of ungulates. Traditional mesowear methods categorize cusps according to relief and sharpness. A geometric morphometric approach has the potential to measure shape with higher precision and to discover unrecognized aspects of cusp shape, possi...

Preclinical education, medical education, anatomy laboratory, pass/fail grading, honors

Dental microwear is used to investigate feeding ecology. Animals ingest geological material in addition to food. The full effect of geological abrasives on tooth wear is unknown. To evaluate mineralogical abrasives as tooth wear agents, rats were fed food manufactured with quartz silt, diatomaceous earth, and calcium carbonate. Rats were assigned t...

Late Eocene brontotheres are documented most prevalently from formations in the Great Plains of North America. Here we describe UCM 109045, a mandible and lower dentition of a brontothere recovered from a latest Eocene (Chadronian) locality in the Antero Formation in South Park, Colorado. This is a high-altitude locality in which vertebrate fossils...

Retention among academic medicine faculty is problematic, and there has been a decline in the number of physicians pursuing careers in academia. The education of future physicians relies upon physicians who pursue careers in academic medicine. Therefore, efforts must be taken to increase the percentage of physicians who conduct research and/or teac...

Dental microwear studies often analyze casts rather than original surfaces, although the information loss associated with reproduction is rarely considered. To investigate the sensitivity of high magnification (150x) microwear analysis to common surface replication materials and methods, we compared areal surface texture parameters (ISO 25178-2) an...

Although we do not know the cause of death of most fossil animals, mortality is often associated with ecological stress due to seasonality and other stochastic events (droughts, storms, volcanism) that may have caused shifts in feeding ecology preceding death. In these instances, dental microwear, which reflects feeding ecology in a narrow window o...

We diagnose a new species of Brontotheriidae from a middle Eocene locality, the Clarno Nut Beds, from the Clarno Formation, John Day Basin, Central Oregon. Though renowned for its richness in fossil flora, fossil vertebrates are rare in the Clarno Nut Beds and this new species is the most abundantly represented mammal. Radiometric dating constrains...

Dental microwear analyses of ungulates and other large herbivores rely on correlations of diet and microwear among extant ungulates, primarily ruminants. Microwear is considered a ‘taxon-free’ method of paleodietary analysis. The properties of food are associated with causality of microwear, but the possibility that heritable properties of the cons...

The peripheral nervous system is a promising resource for testing phylogeny although the branching patterns of peripheral nerves are not well documented outside of Homo sapiens. Here we describe the brachial plexus of the rare Sumatran rhinoceros (Dicerorhinus sumatrensis). We compare its brachial plexus to that of another perissodactyl (Equus asin...

In this study, we use tooth mesowear analysis to compare the paleodietary patterns of the classic Late Miocene faunas of Pikermi and Samos from Greece to those of China. A new scale is used for evaluating mesowear, a technique that uses the sharpness of molar cusp apices as a proxy for dietary abrasion. Details of this mesowear scale can be found i...

Cadaver‐based human anatomy courses traditionally dissect the brachial plexus (BP) through the axilla. This approach fails to expose the proximal and posterior parts of the BP. In contrast, non‐human BP dissections use a subscapular approach that exposes the entire BP, from roots to branches. Using four human cadavers, we developed a subscapular ap...

The effects of environmental change on fecundity and mortality rates of ancient populations are likely to have influenced extinction patterns and biogeographical range shifts. To test for a relationship between environmental change and palaeodemographical change, the mortality profiles of late Pleistocene muskrats (Ondatra zibethicus) from north Fl...

Despite the increased use of light microscopy in microwear analysis, studies that recognize observer error are scarce. Nonetheless, microwear analysis based on light microscopy may be more prone to observer bias than SEM or confocal microscopy. We measured observer error among five observers, who independently analyzed identical sets of dental wear...

One potentially problematic aspect of dental microwear analysis is sensitivity to the resolution (fineness of detail) at which dental wear surfaces are viewed. Magnification is one of many variables that determine resolution. Microwear studies based on light microscopy generally report magnifications ranging from 30X-100X, although ambiguities in r...

The evolution of high-crowned molars among horses (Family Equidae) is thought to be an adaptation for abrasive diets associated with the spread of grasslands. The sharpness and relief of the worn cusp apices of teeth (mesowear) are a measure of dietary abrasion. We collected mesowear data for North American Equidae for the past 55.5 million years t...

Diplacodon gigan is a new species of uintan brontothere recognized from an exquisitely preserved skull from the Wiggins Formation, Hot Springs County, Wyoming. Close affinity to Protitanotherium emarginatum has been suggested based on similarities of canine size and horn shape. However, evidence suggests that canine size and horn morphology were se...

In addition to its abundance in the middle Eocene of the Western Interior of North America, fossils of the brontothere Metarhinus are known from similar aged deposits in Southern California. Because of additional material from the Friars and Santiago Formations, San Diego County, California, M. pater Stock (1937)52. Stock , C. 1937. An Eocene tita...

The paleodietary ecology of Late Pleistocene ungulate faunas of the Mammoth Steppe ecosystem was investigated at Fairbanks (Alaska) and Brown Bank (North Sea) through dental mesowear and microwear analysis. The purpose of the study is to address questions concerning the paleoecology of the Mammoth Steppe, an ecosystem that has no extant analog. Den...

A new genus and species of “horned” brontothere, Aktautitan hippopotamopus, from the Ily Basin of Kazakstan is described from three skulls and nearly complete postcranial material. This material occurs in fluvio-lacustrine red beds of the upper part of the Eocene (Irdinmanhan) Kyzylbulak Formation at Aktau Mountain. Trackways occurring in the overl...

The Brontotheriidae is an extinct family of Eocene perissodactyls known from North America, Asia, and, rarely, Eastern Europe. Brontotheres are widely recognized as having evolved very large body size and conspicuous frontonasal horns, although these traits do not characterize every species. Characters shared by all brontotheriids include an antero...

Rhinos are the only modern perissodactyls that possess cranial weapons similar to the horns, antlers and ossicones of modern ruminants. Yet, unlike ruminants, there is no clear relationship between sexual dimorphism and sociality. It is possible to extend the study of the coevolution of sociality and sexual dimorphism into extinct rhinos by examini...

Without Abstract

The evolution of increased tooth crown height is considered to be an adaptation for coping with excessive rates of dental wear associated with abrasive herbivorous diets, such as grazing and(or high levels of exogenous grit (e.g. dust, sand, ash). Evolutionary trends in the crown heights of North American ungulates are grossly consistent with a tra...

Wet sites in Florida are widely known for their exceptional preservation of organic materials, including diverse plant remains, collagen-rich bone, and brain and other animal soft tissues (Cushing, 1897; Clausen et al., 1979; Beriault et al., 1981; Wharton et al., 1981; Purdy, 1987a,b; Doran and Dickel, 1988; Dunbar et al., 1989; Doran, 2002; see P...

A strong relationship between sexual dimorphism and the degree of polygyny (i.e., the degree to which males compete for mates) is not apparent in living perissodactyls. For instance, in both monomorphic and dimorphic species of rhinos, about half of male mortality is attributable to tusk and horn mediated combat. Males of the North American Miocene...

Among polygynous mammals, a heightened risk of mortality is linked to the intensity of intragender competition and life-history stages, such as sexual maturity, where inexperienced individuals are vulnerable to the aggressive behaviors of dominant individuals. In this respect, the age- and sex-specific mortality patterns found in fossil assemblages...

The muskrat (Ondatra zibethicus) is presumed to have undergone a rapid phyletic size decrease near the end of the Pleistocene. Evolutionary changes in the size of middle to late Wisconsinan (ca. 32,000–12,300 14C yr B.P.) muskrats from the Aucilla River, Jefferson County, Florida, were reconstructed by examining length and width of the lower first...