Search

Dental microwear texture analysis (DMTA) is commonly used to assess the dietary ecology of modern and fossil taxa. In carnivorans, teeth with different functions record dietary behavior differently. Here, we assess DMTA variability along the tooth row of an extant carnivorous marsupial—the Tasmanian devil, Sarcophilus harrisii—which has multiple carnassial-like molars that may function and record diet similarly. We compared the complexity (Asfc), anisotropy (epLsar), and textural fill volume (Tfv) of the lower second, third, and fourth molars of Tasmanian devils to test the hypothesis that teeth with similar forms yield similar functions. Although third molars do have significantly higher epLsar values than fourth molars, all other DMTA attributes are indistinguishable from one another. These data suggest that teeth with comparable morphologies in the same taxon have similar functions and largely record diet similarly. In addition, we compared fossil and modern specimens of S. harrisii from Tasmania to assess dietary behavior over time. These analyses indicate that foods with similar textures have been consumed since the late Quaternary. [ABSTRACT FROM AUTHOR]

Xenarthran teeth are rootless and continuously growing. They lack an outer enamel layer and consist instead of a combination of 2 generally different varieties of dentine with or without an outer collar of cementum. This dental make-up is unique among mammals. In the last decade, xenarthran teeth have been subject to a number of studies regarding microscopic features, including analyses of microstructure and microwear patterns. Here, we present a review of the present knowledge in these 2 fields together with new results on feeding adaptations in the giant ground sloth, Megatherium americanum. Microwear patterns suggest that M. americanum fed mainly on plants with low to moderate intrinsic toughness, although we observe a trend that microwear patterns in extinct sloths may reflect habitat (i.e., feeding in open habitats with higher amounts of grit versus closed habitats with lower amounts of grit) as much as, if not more than, the texture of ingested food. [ABSTRACT FROM AUTHOR]

There has been much discussion of the role of behaviour in evolution, especially its potential to lead morphological evolution by placing the organism in a novel selective environment. Many adaptations of living species can be imagined to have originated in this way, although documented examples are relatively few. A fruitful arena for testing hypotheses about behavioural innovation is the fossil record. Traditionally, the behaviour of fossil species has been deduced from their morphology, precluding the observation of a behavioural lead preceding morphological evolution. This circularity can be broken by examining behavioural proxies independent of the adaptive morphology itself. Examples applicable to fossil remains include dietary information (e.g. wear traces on teeth, stable isotopes) and trace fossils indicating locomotor mode (footprints). The signature of a behavioural lead would be an observed shift in behaviour from one horizon (or taxon) to another, followed later by a functionally-related morphological change. This pattern can be sought either in finely-stratified anagenetic sequences of fossils (stratophenetic approach) or among fossils with well-resolved species-level phylogenies (cladistic approach). An array of case studies from the literature is presented. These include feeding shifts in finely-resolved sequences of vertebrates ranging from freshwater fish to terrestrial ungulates, as well as locomotor changes crucial to major evolutionary transitions in the origin of tetrapods, birds, and humans. The latter examples highlight the role of behaviour in initiating exaptation (the requisitioning of structure for a new function). The case studies also illustrate the challenges of using fossil sequences to elucidate behavioural roles, including insufficient stratigraphic resolution and uncertainty over the adaptive function of observed traits. By the same token, they suggest criteria for choosing promising cases for research, as well as for formulating testable hypotheses about evolutionary modes. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 315-331. [ABSTRACT FROM AUTHOR]

Most dental microwear texture studies to date have focused on enamel surfaces. However, for xenarthran microwear we must, in effect, "reinvent the wheel," because adult xenarthrans lack enamel. Dentin is softer than enamel and may record microwear differently. Thus, we aim to determine if dental microwear texture analysis (DMTA, which quantifies microwear in 3 dimensions) of dentin can yield biologically meaningful results by asking: do dentin and enamel in other eutherians record microwear texture the same way; and can DMTA differentiate between extant xenarthrans with different diets? We analyzed the carnassials of Florida panthers (Puma concolor coryi, n = 14), which have functional dentin and enamel, and found differences in texture fill volume and heterogeneity, suggesting that enamel and dentin DMTA cannot be directly compared. Next, we analyzed the teeth of sloths (Bradypus variegatus, n = 12; Choloepus hoffmanni, n = 9) and the 9-banded armadillo (Dasypus novemcinctus, n = 12), which differ in 2 attributes (surface complexity and fill volume) associated with food or abrasive properties. Other DMTA attributes show no differences between trophic groups, suggesting that dentin and enamel may differ in types of texture attributes that separate taxa by diet. [ABSTRACT FROM AUTHOR]

The analysis of orthodentine microwear has recently been established as a proxy for diet in extant and fossil xenarthrans (sloths, armadillos, and their extinct relatives). Previous analyses have relied on standardized comparison of sampling locations between taxa in order to statistically correlate microwear on xenarthran teeth with primary diet; variation in orthodentine microwear across the toothrow and its potential effect on dietary classification in xenarthrans remains unexplored. This study is the 1st to examine intertooth variation of microwear features in extant xenarthrans to test the necessity of standardized tooth comparison in orthodentine microwear analysis of paleodiet in fossil taxa. Statistical mean correlation tests were used to compare microwear variables between different sampling locations in a series of upper and lower teeth in 4 extant xenarthran species (Bradypus tridactylus [pale-throated three-toed sloth], Choloepus didactylus [Linnaeus' two-toed sloth], Dasypus novemcinctus [nine-banded armadillo], and Euphractus sexcinctus [six-banded armadillo]) and showed that microwear distribution between sampling locations is more conserved in three-toed sloths relative to two-toed sloths and armadillos. Significant variation in the latter groups may stem from uneven distribution of bite-force on the dentition in long-faced animals (two-toed sloths and armadillos) relative to short-faced animals (three-toed sloths), although food texture and intraspecific variation in diet may play a role as well. Based on results from extant taxa, standardized tooth comparison is required for analysis of paleodiet in glyptodonts and pampatheres and also is recommended for ground sloths in future studies of microwear. [ABSTRACT FROM AUTHOR]