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M F Teaford

Publications and source records attributed to M F Teaford.

32 records · Page 2Linked to original sources
PubMed1989

Seasonal or ecological differences in diet and molar microwear in Cebus nigrivittatus.

Dental microwear analyses have raised new hopes and questions for functional morphologists. One hope is that analyses will allow insights into subtle dietary differences of extinct species. One major question is whether seasonal and/or habitat differences in dental microwear are reliably detectable. The extensive collections of Cebus nigrivittatus obtained by the Smithsonian Venezuelan Project allowed us to examine seasonal and habitat differences in dental microwear. Specimens were collected from three distinct ecological life zones that are distinguished by both the amount of rainfall and its seasonability. Environmental variation is generally correlated with variation in resource availability which, in C. nigrivittatus, affects diet. Published field studies indicate that these animals depend more on dry hard fruit and chitinous invertebrates during drier times and succulent fruits and caterpillars during wetter times of the year. As in previous microwear analyses, epoxy replicas were prepared from dental impressions, and the replicas were examined under a scanning electron microscope. Two micrographs were taken of facet 9 on M2 of each specimen. Mean values for the proportion of pits (vs. scratches), pit width, and scratch width were computed for each of 62 individuals and compared between ecological zones and collecting dates by using a multiple comparison test. Results indicate that, while seasonal differences in molar microwear in C. nigrivittatus are perhaps reliably detectable, 1) they are small in magnitude, 2) they are only detectable in certain ecological life zones, and 3) they are not of the order of magnitude that will obscure major interspecific differences in molar microwear such as those between C. apella and C. nigrivittatus.

Analysis of Variance↗
PubMed1989

In vivo and in vitro turnover in dental microwear.

Given the potential usefulness of dental microwear analyses in interpretations of archaeological and paleontological material, it is surprising how little we know about changes in individual microwear features through time. The purpose of this study was to document the turnover in primate dental microwear through in vivo dental studies of monkeys raised on different diets, and through in vitro studies of the abrasive effects of monkey chow biscuits on isolated monkey teeth. As in previous studies, epoxy replicas were prepared from dental impressions and examined under a scanning electron microscope. Results indicate that, under certain conditions, the turnover in primate dental microwear can be on the order of days, hours, or even minutes. Individual microscopic wear features can be obliterated within 24 hours on the molars of laboratory monkeys, and monkey chow biscuits can easily scratch the enamel of isolated monkey teeth. Monkeys raised on a hard diet showed more rapid turnover in dental microwear than monkeys raised on a soft diet. However, paired-sample tests revealed that, for all animals, the molar shearing facets were being abraded at a significantly slower rate than molar crushing/grinding facets. In light of these results, investigators should make every effort to use large samples in interspecific comparisons of dental microwear involving species with variable diets. Another implication of these results is that changes in dental microwear might be useful indicators of changes in oral behavior over relatively short periods of time.

Animals↗
PubMed1989

Differences in tooth wear as an indicator of changes in jaw movement in the guinea pig Cavia porcellus.

Patterns of tooth wear have frequently been used to make inferences about jaw movements and tooth use in modern and extinct mammals. However, there has been relatively little experimental work to define the limits of usefulness of tooth wear studies. In the present study, electrolytic lesions in the left trigeminal motor nucleus of five guinea pigs resulted in significant changes of jaw movement. Scanning electron microscopy revealed significant differences in tooth wear between the lesion and non-lesion sides of these animals. Control animals showed no significant differences in tooth wear between right and left sides. The differences in tooth wear in the experimental animals were readily interpretable in terms of the induced changes in jaw movement.

Animals↗
PubMed1989

Differences in the rate of molar wear between monkeys raised on different diets.

The purpose of this study was to make detailed comparisons of rates and patterns of tooth wear in 15 growing vervet monkeys raised on hard vs. soft diets. Dental impressions were taken every six to eight weeks over a four-year period. Cusp heights and areas of dentin exposure on the buccal cusps of the left mandibular first molar were measured from high-resolution epoxy casts, by use of a Reflex Measuring Microscope. Areas of dentin exposure were regressed against time (by use of least-squares regression) so that the course of tooth wear in animals from both diet groups could be charted. By use of a two-sample t test and the Mann-Whitney test, slopes of the regressions and changes in cusp height were compared between diet groups. In both comparisons, animals raised on the hard diet showed more rapid tooth wear than did animals raised on the soft diet. Analyses of other parameters indicate that this was probably because of differences in dietary consistency between the two groups.

Animals↗
PubMed1988

A review of dental microwear and diet in modern mammals.

Recent work has shown that microscopic wear patterns on teeth may yield insights into variations in diet and tooth use in modern and prehistoric mammals. This paper presents a review of dental microwear and diet in modern mammals, plus a discussion of topics for further research. To date, incisor and molar microwear have been examined, although there are far fewer studies of the former. Facilitated by the use of high-resolution casts and scanning electron microscopy, analyses have ranged from: qualitative to quantitative, low magnification to high magnification, and experimental studies to comparative studies of museum collections. Results are encouraging and may lead to further insights into a variety of topics including food processing and dental microstructure.

Animals↗
PubMed1988

Scanning electron microscope diagnosis of wear patterns versus artifacts on fossil teeth.

Recent work with modern mammalian teeth has shown that, during an animal's lifetime, microscopic wear patterns are generally laid down in a regular fashion at specific locations on the teeth. These regularities make it possible to distinguish real dental microwear (resulting from behaviors during life) from artifacts of preservation and preparation (postmortem wear) on fossil teeth. The size, shape, location, and orientation of microscopic wear features can all aid in making such distinctions. Several types of postmortem wear are identifiable on fossil teeth. Since some of these effects are intimately tied to the taphonomic history of the fossil, some postmortem wear will vary significantly within and between paleontological sites. Moreover, certain forms of postmortem wear will undoubtedly pose problems for microwear interpretations involving fragments of teeth. Still, it is usually possible to distinguish postmortem wear from real dental microwear in complete specimens. If there is any doubt about such distinctions, it is best to discard the specimen from the analysis.

Animals↗
PubMed1986

Body weights in mixed species troops of Saguinus mystax mystax and Saguinus fuscicollis nigrifrons in Amazonian Peru.

An investigation of body weights of members of mixed species troops of Saguinus mystax mystax and Saguinus fuscicollis nigrifrons was conducted at the Rio Blanco Research Station in northeastern Peru. A total of 107 adult and subadult tamarin monkeys were trapped, measured, and released. Data collected indicate that mean body weights for adult male and female moustached tamarins are 564 gm and 626 gm, respectively, whereas for adult saddle-back tamarins these values are 412 gm and 411 gm. Subadults weighed 11-27% less than adults. Body weights recorded in this study are significantly greater than those previously reported for tamarins of the same species and age living in other areas of Amazonian Peru. We hypothesize that, in the case of moustached and saddle-back tamarins, advantages associated with feeding and foraging in mixed species troops facilitate greater efficiency in resource monitoring and result in the maintenance of larger body weights.

Age Factors↗
PubMed1986

New wrist bones of Proconsul africanus and P. nyanzae from Rusinga Island, Kenya.

The anatomy of the wrist of two species of the early Miocene hominoid Proconsul is described based on new material collected on Rusinga Island, Kenya. These fossils generally confirm previous findings that the wrist of Proconsul is monkey-like in much of its morphology. However, the structure of the ulnar side of the wrist, particularly the ulnocarpal joint, is significantly different from that of extant monkeys and suggests some functional affinities with extant hominoids. Thus the wrist of Proconsul is neither monkey-like nor ape-like in its total morphology. Instead, it shows a unique combination of features which once again point to the oversimplicity of forcing fossil forms into categories based only on extant taxa.

Animals↗
PubMed1985

Molar microwear and diet in the genus Cebus.

Recent analyses have documented differences in dental microwear between primate species with different diets, especially between primate hard-object feeders and primate leaf-eaters. Thus far, these microwear differences have only been documented for primates with vastly different foraging strategies and geographic distributions. To see if similar differences could be documented for closely related species, dental replicas from Cebus apella, Cebus nigrivittatus, and Cebus capucinus were examined using scanning electron microscopy. Quantitative analyses reveal that (1) even for closely related species, microwear differences between facets of one species are still far less than those between homologous facets of different species; and (2) the dental microwear of Cebus apella, Cebus nigrivittatus, and Cebus capucinus are still significantly different from one another. Furthermore, the data suggest that the dietary differences between these species may center around the presence or absence of hard objects in the diet.

Animals↗
PubMed1984

Quantitative differences in dental microwear between primate species with different diets and a comment on the presumed diet of Sivapithecus.

Studies of dental microwear have been used to relate tooth form to function in a variety of recent and extinct mammals. Probably the most important aspect of microwear analysis is the possibility of using it to deduce the diet of extinct animals. Such deductions must be based on comparative studies of modern species with known diets, but to date, only qualitative studies have been attempted and all have been based on small samples. Here we report quantitative differences in dental microwear between primate species that are known to have different diets. Occlusal facets with different functions have previously been shown to exhibit different microwear patterns. However, the differences between facets of one species are shown to be far less than those between homologous facets of different species. Study of seven species of extant primates shows that enamel microwear can be used to distinguish between those with a mainly frugivorous diet and those with a mainly folivorous one. Microwear can also distinguish hard-object feeders from soft-fruit eaters. The microwear of Miocene Sivapithecus indicus cannot be distinguished statistically from that of the chimpanzee, but it is different from that of the other species. On this evidence S. indicus was not a hard-object feeder and the adaptive significance of its thick molar enamel is at present unknown.

Animals↗
PubMed1983

The morphology and wear of the lingual notch in macaques and langurs.

Although interspecific differences in the relative development of molar occlusal features have been documented for most primate species, wear-related changes in these features are only beginning to be understood. In the present study, the notch between the metaconid and entoconid of M2 was examined in a skeletal sample of Macaca fascicularis, presbytis cristatus, and Presbytis rubicunda from the Museum of Comparative Zoology at Harvard University. Photogrammetric analyses yielded X, Y, and Z coordinates that were used to compute three angular measurements and two length measurements at the lingual notch. Statistical analyses of measurements from unworn dentitions indicated that the mesial slope of the entoconid is steeper than the distal slope of the metaconid in all three species. In addition, interspecific comparisons demonstrated that P. cristatus has the steepest lingual notch bordered by the largest molar shearing crests, while P. rubicunda and M. fascicularis have molar shearing crests of similar size, with P. rubicunda merely having higher cusps that are closer together than those of M. fascicularis. Finally, P. cristatus shows a smaller decrease in lingual cusp relief with wear than M. fascicularis, while P. cristatus and P. rubicunda probably show similar decreases in lingual cusp relief with wear. The differences in wear-related changes in lingual cusp relief between M. fascicularis and P. cristatus may well be related to the frugivorous/folivorous dietary differences between these species.

Animals↗
PubMed1983

Dental microwear in adult and still-born guinea pigs (Cavia porcellus).

Scanning electron microscope analyses of dental microwear showed that (1) microscopic striations are not caused by tooth-tooth contact, and (2) the model of striation formation used by Ryan (1979a, J. dent. Res. 58, 525-530; 1979b, Am. J. phys. Anthrop. 50, 155-168) to make directional interpretations of jaw movement is incorrect.

Animals↗
PubMedDate not supplied

Error rates in dental microwear quantification using scanning electron microscopy.

There is a degree of correlation between dietary habits and dental microwear in extant primates, and this has enabled inferences to be made about prehistoric diets. Several techniques have been used to quantify microwear, but the comparability of results derived from each has not been demonstrated. Moreover, neither intra- nor interobserver error rates in microwear quantification have been documented to date. We here assess intra- and interobserver error using Microware 4.0, and evaluate intertechnique comparability using the three methods that have been most widely employed in the field. This study documents an overall intraobserver error rate of about 7%, and an overall interobserver error rate of some 9%. Both intra- and interobserver error appears to be influenced substantially by the nature of the micrograph being measured. In no instance did the results obtained by different observers using Microware 4.0 differ significantly, and there was a reasonable degree of interobserver consistency in the rank ordering of micrographs in relation to any given parameter. The results obtained through the use of different quantitative techniques differed significantly, with an overall intertechnique error rate of approximately 19%. Several variables, including differences in magnification factor, scanning electron microscope kV settings, and specimen-detector relationships undoubtedly contribute to the differences among the three methods, but we were not able to assess their relative importance. Microwear quantification permits distinctions between broad dietary categories, but the margin of intra- and interobserver error should be taken into account when defining pattern differences between populations (or species) or when documenting seasonally mitigated differences within a taxon. In view of the error introduced by the use of different methods, we suggest that a consistent technique, such as offered by the Microware software package, be adopted by current researchers to establish a common microwear database.

Animals↗