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Objectives: Intra‐tooth patterns of trace elements barium (Ba) and strontium (Sr) have been used to infer human and nonhuman primate nursing histories, including australopithecine and Neanderthal juveniles. Here, we contrast the two elemental models in first molars (M1s) of four wild baboons and explore the assumptions that underlie each. Materials and Methods: Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) was employed to create comprehensive calcium‐normalized barium and strontium (Ba/Ca, Sr/Ca) maps of M1 enamel and dentine at 35 micron resolution. Results: Postnatal Ba/Ca values were typically high, peaking ~0.5 years of age and then decreasing throughout M1 crown formation; all four individuals showed minimal Ba/Ca values between ~1.2–1.8 years, consistent with field reports of the cessation of suckling. Enamel Sr/Ca did not support patterns of previous LA‐ICP‐MS spot sampling as the enamel rarely showed discrete Sr/Ca secretory zonation. Increases in Sr/Ca appeared in coronal dentine beginning ~0.3 years, with varied peak value ages (~0.7–2.7 years) and no evidence of a predicted postweaning decline. Discussion: Inferences of baboon weaning ages from initial Ba/Ca minima are more congruent with behavioral observations than Sr/Ca maxima; this is consistent with studies of captive macaques of known weaning ages. Elemental variation is more apparent in the coronal dentine than the enamel of these baboons, which may relate to its more rapid mineralization and protection from the oral environment. Inferences of nursing histories from enamel Sr/Ca patterns alone should be reconsidered, and elevated values of Ba/Ca and Sr/Ca in teeth formed after weaning require further study. [ABSTRACT FROM AUTHOR]

The techniques of dental histology provide a method for reconstructing much of the life history of an individual, as accentuated increments visible in polarized light microscopy record incidents of physiological stress during the formation of dental tissues. Combined with counts of the normal periodic growth increments, they provide a means of reconstructing the chronology of dental development, age at death, and the ages at which stress occurs. In this study, we determine age at death and reconstruct the chronology of dental development in two male anubis baboons from Uganda and two female baboons from the Awash National Park hybrid zone. For the female baboons, we used the dates of death and rainfall records for the region to determine date of birth, ages at periods of physiological stress, dates at which these stresses occurred, and rainfall amounts for those months. Ages determined histologically for each specimen are comparable to ages estimated from dental emergence schedules and dental scores for wild baboons. Crown formation times are longer than those reported in radiographic studies of captive yellow baboons. Age at initiation of crown formation is similar to that reported for radiographic studies, but ages at completion of crown formation are consistently later. The pattern of stresses is similar in the two female baboons, suggesting that individual life history intersects with local ecology to produce a pattern of accentuated increments occurring during the weaning process and at the onset of menarche, as well as during the first postweaning dry and rainy periods. Am J Phys Anthropol 118:239-252, 2002. KEY WORDS dental histology; accentuated growth increments; age determination; crown formation; weaning process; menarche; postpartum cycle; reproduction

Dental developments of two pairs of closely related catarrhine primate species, that differ in their degree of folivory are studied. The two pairs of primate species, used for study are, Hylobates lar and Symphalangus, and Papio hamadryas hamadryas and Semnopithecus entellus.

Paleoenvironmental reconstructions based on mammalian faunas provide the contextual basis for understanding evolutionary events in many branches of paleobiology. This paper presents the first blind test of an environmental reconstruction using extant African small mammals. We collected 1216 specimens representing a minimum of 332 individuals from Ngofila 3, Tanzania, then conducted a blind analysis of the taxonomic and community composition. We found agreement between the observed habitat and the predicted habitat along eight aspects of the environment: (1) mean annual precipitation, (2) surface water availability, (3) soil type, (4) vegetation, (5) land use, (6) topography, (7) habitat heterogeneity, (8) temperature. Of these, the first six had high agreement between the observed and predicted descriptions, two (topography and habitat heterogeneity) had moderate agreement and the last, (temperature) was discussed in the observed habitat description but not addressed in the predicted description and could not be compared. The high level of agreement demonstrates that paleoenvironmental reconstruction can accurately portray a known habitat. In addition, we suggest factors that should be considered in a standard method of habitat description, which would improve comparability of results between different analyses. [ABSTRACT FROM AUTHOR]

The condylarths, or archaic ungulates, are a paraphyletic mammalian group including a number of fossil taxa whose relationships are unresolved. Included are two genera from the Paleocene and Eocene of North America, Meniscotherium and Phenacodus. Some workers place both genera in the family Phenacodontidae, while others exclude the highly dentally derived Meniscotherium. In this study, we use growth increments in histological thin sections to examine the timing of crown formation in five molars of Meniscotherium and one each of Phenacodus intermedius and Phenacodus trilobatus. We also use perikymata counts on an additional six molars of Meniscotherium. Although estimated body mass and molar dimensions in Meniscotherium are smaller than in either species of Phenacodus, molar formation times are longer, ranging from 0.71 to 1.44 years. Both Phenacodus molars take less than a year to form. Crown extension rates, the rate at which the crown grows in height, are as low as 3-15 µm per day in Meniscotherium, but range from 13 to 54 µm per day in Phenacodus. Although striae periodicities and daily enamel secretion rate are similar in both genera, the differences in the crown extension rate and overall timing of crown formation suggest differences in life histories and raise questions about the phylogenetic relationship of the two genera. [ABSTRACT FROM AUTHOR]

The article discusses the highlights of the 15th International Symposium on Dental Morphology, held in Newcastle Upon Tyne, United Kingdom from August 24-27, 2011. Topics of research presented at the symposium included clinical aspects of dental morphology, dental anthropology, dental evolution, dental function or tooth food interactions, dental growth and development, dental morphology, dental issues, genetics of tooth morphology and paleodontology.

The use of dental development to chart and understand life history evolution has been one of the most fruitful lines of research in palaeontology and biological anthropology for many years. My aim here is to present an overview of the current state of this research using examples from my own research and that of my colleagues. My focus will be on the levels at which we understand life history variation and the appropriate levels at which both our questions and our methods can inform our work. Life history variables, e.g. gestation, age at weaning, age at first reproduction, and lifespan, vary between individuals within populations, between populations within species, between species, and between clades above the species level. Dental development can be seen to operate at two basic levels - the formation of individual teeth and the formation of the dentition. The formation of teeth is one step removed from life history, as the primary purpose of its components (e.g. daily secretion rate of enamel and dentine, angle of the striae of Retzius, combining to form extension rate) is to create a functional unit of a certain size, constrained by the time (life history) in which it develops. The formation of the dentition is more closely related to life history, as the development and eruption of teeth must match the pace of overall growth of the individual. The questions we ask about life history and the measures we make of aspects of dental development need to be aligned in order to be meaningful. Exciting new techniques allow us to look at life history variation between individuals; other methods are required to allow us to look at life history at higher levels, including not just eruption of teeth, particularly molars, but also their development relative to each other across the growth period. [ABSTRACT FROM AUTHOR]

The origin of determinate growth in mammals is associated with other important mammalian characters, including diphyodont dentition, lactation and endothermy. These characters likely evolved in the extinct cynodont and basal mammaliaform lineages of the Triassic and early Jurassic, with Morganucodon hypothesised to be the most basal mammaliaform to have both determinate growth and diphyodonty. Histological techniques to assess periodic enamel increments have not previously been applied to cynodonts and mammaliaforms, and are likely to improve understanding of their dental replacement and growth patterns. We prepared histological thin sections of postcanines of three cynodonts (Thrinaxodon, Scalenodon, Diademodon), molars of Morganucodon, and teeth from crown mammals and diapsids (e.g. Crocodylus, Canis, Tupaia). Using polarized light microscopy we assessed measures relating to dental growth patterns, including daily secretion rates of enamel, and crown and root extension rates. Two orders of incremental lines, analogous to daily prism cross-striations and longer period striae of Retzius of mammalian enamel, were observed in all cynodont and mammaliaform specimens. Daily secretion rate was lower in cynodont and mammaliaform enamel than in crown mammal teeth of comparable size. Very high mean crown extension rates were observed, both in diapsids and cynodonts (e.g. Crocodylus: 33.9μm/day; Thrinaxodon: 104.2μm/day), with cynodont extension rates at least double those of crown mammals with comparably sized teeth. Enamel thus extended extremely rapidly in thin 'sheath'-like layers in diapsids and cynodonts. In contrast, crown extension rate in Morganucodon is much lower (7.8μm/day), more closely resembling the crown mammals used for comparison. Low extension- and daily secretion rates suggest lower differentiation rates and secretory function of ameloblasts in Morganucodon. If this is coupled with reduced function of osteoblasts, it may suggest reduced rates of bone growth during molar formation. These patterns would be consistent with the hypothesis of determinate growth patterns in Morganucodon and of more indeterminate growth in cynodont species. [ABSTRACT FROM AUTHOR]

Accurate quantification of variation in tooth shape is important in hypodontia patients. Several techniques have been used to quantify tooth size and shape in hypodontia patients and these have shown smaller tooth dimensions and anomalous tooth shapes in these patients when compared with controls. However, previous studies have mainly used 2D images and provided limited information. In the present study, 3D surface-imaging and statistical shape analysis were used to evaluate tooth form differences between hypodontia and control patients. Eighteen anatomical landmarks were recorded on the clinical crown of the lower left first permanent molar of 3D scanned study models of hypodontia and control subjects. The study sample comprised 120 hypodontia patients (40 mild, 40 moderate and 40 severe hypodontia patients) and 40 age- and sex-matched controls. Procrustes coordinates were utilized to scale and superimpose the landmark coordinate data and then were subjected to principal component analysis (PCA). Subsequently, shape differences were tested statistically using MANOVA. Significant interaction was found between the two factor variables "group" and "gender" (p< 0.002). Overall expected accuracies were 66% and 56% for females and males respectively in the discriminant analysis using the first 20 PCs. There appears to be progression in shape variation from mild, to moderate to severe hypodontia, while the controls are isolated from all three groups. Hypodontia groups showed significant shape differences compared with the control subjects (p<0.0001). Significant differences in tooth crown shape were also found between sexes (p<0.0001). The degree of variation in tooth shape was associated with the degree of the severity of the hypodontia. Quantitative measurement of the tooth shape in hypodontia patients may enhance the multidisciplinary management of those patients. [ABSTRACT FROM AUTHOR]

Objectives: Intra-tooth patterns of trace elements barium (Ba) and strontium (Sr) have been used to infer human and nonhuman primate nursing histories, including australopithecine and Neanderthal juveniles. Here we contrast the two elemental models in first molars (M1s) of four wild baboons and explore the assumptions that underlie each., Materials and Methods: Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was employed to create comprehensive calcium-normalized barium and strontium (Ba/Ca, Sr/Ca) maps of M1 enamel and dentine at 35 micron resolution., Results: Postnatal Ba/Ca values were typically high, peaking ~0.5 years of age and then decreasing throughout M1 crown formation; all four individuals showed minimal Ba/Ca values between ~1.2-1.8 years, consistent with field reports of the cessation of suckling. Enamel Sr/Ca did not support patterns of previous LA-ICP-MS spot sampling as the enamel rarely showed discrete Sr/Ca secretory zonation. Increases in Sr/Ca appeared in coronal dentine beginning ~0.3 years, with varied peak value ages (~0.7-2.7 years) and no evidence of a predicted postweaning decline., Discussion: Inferences of baboon weaning ages from initial Ba/Ca minima are more congruent with behavioral observations than Sr/Ca maxima; this is consistent with studies of captive macaques of known weaning ages. Elemental variation is more apparent in the coronal dentine than the enamel of these baboons, which may relate to its more rapid mineralization and protection from the oral environment. Inferences of nursing histories from enamel Sr/Ca patterns alone should be reconsidered, and elevated values of Ba/Ca and Sr/Ca in teeth formed after weaning require further study.