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At least 145 records · Page 8Linked to original sources
PubMed2006

Lingual incisor traits in modern hominoids and an assessment of their utility for fossil hominoid taxonomy.

The morphology of the anterior dentition has received scant attention for purposes of taxonomic discrimination. Recently, however, lingual incisor morphology was used in differentiating several Miocene ape species and genera. This paper assesses the utility of this morphology for taxonomic discrimination by examining the nature and patterns of variation in lingual incisor morphology in extensive samples of modern chimpanzees, gorillas, orangutans, and gibbons. This paper documents discrete morphological traits on the lingual side of incisors. Trait frequencies are used in univariate and multivariate analyses to examine the apportionment of variation in species, subspecies, and populations. A correlation between lingual incisor traits, tooth dimensions, and sex attempts to determine if such factors affect the manifestation of traits. Finally, the findings are applied to understanding patterns of variation in the Miocene hominids. The study demonstrates that: 1) lingual incisor morphology differs substantially between the hylobatids and great apes; 2) variation in incisor traits is high within species, and most of it is found within local populations; and 3) incisor traits do not correlate significantly with incisor dimensions or sex. Species and to some extent subspecies of extant hominoids can be differentiated statistically using lingual incisor traits, but the frequency of traits such as continuous or discontinuous cingulum, or the presence or absence of pillars, differentiates them. Given this pattern of variation, I argue that it is necessary to assume and document similar patterns of variation in Miocene apes before incisor morphology is used for differentiating taxa.

Analysis of Variance↗
PubMed2006

Associations between Carabelli trait and cusp areas in human permanent maxillary first molars.

Few dental anthropological studies have investigated the associations between tooth crown size and crown traits in humans using quantitative methods. We tested several hypotheses about overall crown size, individual cusp areas, and expression of Carabelli cusps in human permanent first molars by obtaining data from standardized occlusal photographs of 308 Australians of European descent (171 males and 137 females). Specifically, we aimed to calculate the areas of the four main molar cusps, and also Carabelli cusp, and to compare the relative variability of cusp areas in relation to timing of development. We also aimed to compare cusp areas between males and females and to describe how Carabelli cusp interacted with other molar cusps. Measurements included maximum crown diameters (mesiodistal and buccolingual crown diameters), the areas of the four main cusps, and the area of Carabelli cusp. The pattern of relative variability in absolute areas of molar cusps corresponded with their order of formation, the first-forming paracone displaying the least variation, and the last-forming Carabelli cusp showing the greatest. Overall crown size and areas of individual cusps all showed sexual dimorphism, with values in males exceeding those in females. Sexual dimorphism was smallest for paracone area and greatest for Carabelli cusp area. Overall crown size and cusp areas were larger in individuals displaying a Carabelli cusp, especially the hypocone area. Although the combined area of the protocone and a Carabelli cusp was greater in cuspal forms than noncuspal forms, protocone area alone was significantly smaller in the former. Our findings lead us to propose that, in individuals with the genotype for Carabelli trait expression, larger molar crowns are more likely to display Carabelli cusps, whereas molars with smaller crowns are more likely to display reduced forms of expression of the trait. We suggest that the pattern of folding of the internal enamel epithelium in developing molar crowns, particularly in the protocone region, can be modified by a developing Carabelli cusp.

Analysis of Variance↗
PubMed2006

Evolution of genetically correlated traits: tooth size and body size in baboons.

Within a population, only phenotypic variation that is influenced by genes will respond to selection. Genes with pleiotropic effects are known to influence numerous traits, complicating our understanding of their evolution through time. Here we use quantitative genetic analyses to identify and estimate the shared genetic effects between molar size and trunk length in a pedigreed, breeding population of baboons housed at the Southwest National Primate Research Center. While crown area has a genetic correlation with trunk length, specific linear measurements yield different results. We find that variation in molar buccolingual width and trunk length is influenced by overlapping additive genetic effects. In contrast, mesiodistal molar length appears to be genetically independent of body size. This is the first study to demonstrate a significant genetic correlation between tooth size and body size in primates. The evolutionary implications are discussed.

Animals↗
PubMed2007

Mineralization of the mandibular third molar: a study of American blacks and whites.

The tempo of tooth mineralization is under significant genetic control, and the orderly progression of morphological changes-in concert with the long span during growth in which teeth form-makes "dental age" a useful measure of a person's degree of biological maturity. The third molar is of particular interest because (1) it is the last and most variable tooth to form and (2) it is the only tooth to complete formation after puberty, which has made it attractive in forensic and legal circles as an estimator of adulthood. Age standards are described here for mandibular third molar formation stages in a cross-sectional sample of 4,010 persons (age range: 3-25 years), with proportionate sample sizes of American blacks and whites and males and females. Formation was scored against the 15-grade ordinal scheme of Moorrees, and descriptive statistics were computed using proportional hazards survival analysis. Blacks achieved each formation stage significantly ahead of whites, but not in a uniform manner. Instead, there was an enhanced advancement in blacks during crown formation and during late stages of root formation. In both races formation proceeded faster in males, which is unique for the third molar, as prior studies suggest. Sample variance increases with the stage of formation, such that 95% confidence limits span 8 or more years for root formation stages. Consequently, the third molar provides a rough gauge of an individual's chronological age, but the considerable variability precludes any precise estimate, particularly in late adolescence where most forensic interest has focused.

Adolescent↗
PubMed2007

Population structure of the Classic period Maya.

This study examines the population structure of Classic period (A.D. 250-900) Maya populations through analysis of odontometric variation of 827 skeletons from 12 archaeological sites in Mexico, Guatemala, Belize, and Honduras. The hypothesis that isolation by distance characterized Classic period Maya population structure is tested using Relethford and Blangero's (Hum Biol 62 (1990) 5-25) approach to R matrix analysis for quantitative traits. These results provide important biological data for understanding ancient Maya population history, particularly the effects of the competing Tikal and Calakmul hegemonies on patterns of lowland Maya site interaction. An overall F(ST) of 0.018 is found for the Maya area, indicating little among-group variation for the Classic Maya sites tested. Principal coordinates plots derived from the R matrix analysis show little regional patterning in the data, though the geographic outliers of Kaminaljuyu and a pooled Pacific Coast sample did not cluster with the lowland Maya sites. Mantel tests comparing the biological distance matrix to a geographic distance matrix found no association between genetic and geographic distance. In the Relethford-Blangero analysis, most sites possess negative or near-zero residuals, indicating minimal extraregional gene flow. The exceptions were Barton Ramie, Kaminaljuyu, and Seibal. A scaled R matrix analysis clarifies that genetic drift is a consideration for understanding Classic Maya population structure. All results indicate that isolation by distance does not describe Classic period Maya population structure.

Central America↗
PubMed2004

Statistical genetics of molar cusp patterning in pedigreed baboons: implications for primate dental development and evolution.

Gene expression and knock-out studies provide considerable information about the genetic mechanisms required for tooth organogenesis. Quantitative genetic studies of normal phenotypic variation are complementary to these developmental studies and may help elucidate the genes and mechanisms that contribute to the normal population-level phenotypic variation upon which selection acts. Here we present the first quantitative genetic analysis of molar cusp positioning in mammals. We analyzed quantitative measures of molar cusp position in a captive pedigreed baboon breeding colony housed at the Southwest National Primate Research Center in San Antonio, Texas. Our results reveal complete pleiotropy between antimeric pairs of traits--i.e., they are influenced by the same gene or suite of genes. Mandibular morphological homologues in the molar series also exhibit complete pleiotropy. In contrast, morphological homologues in maxillary molar series appear to be influenced by partial, incomplete pleiotropic effects. Variation in the mandibular mesial and distal molar loph orientation on the same molar crown is estimated to be genetically independent, whereas the maxillary molar mesial and distal loph orientation is estimated to have partially overlapping genetic affects. The differences between the maxillary and mandibular molar patterning, and the degree of genetic independence found between lophs on the same molar crown, may be indicative of previously unrecognized levels of modularity in the primate dentition.

Animals↗
PubMed2003

Dentition and tooth replacement pattern in Chalcides (Squamata; Scincidae).

This study was undertaken as a prerequisite to investigations on tooth differentiation in a squamate, the Canarian scincid Chalcides. Our main goal was to determine whether the pattern of tooth replacement, known to be regular in lizards, could be helpful to predict accurately any stage of tooth development. A growth series of 20 laboratory-reared specimens, aged from 0.5 month after birth to about 6 years, was used. The dentition (functional and replacement teeth) was studied from radiographs of jaw quadrants. The number of tooth positions, the tooth number in relation to age and to seasons, and the size of the replacement teeth were recorded. In Chalcides, a single row of pleurodont functional teeth lies at the labial margin of the dentary, premaxillary, and maxillary. Whatever the age of the specimens, 16 tooth positions were recorded, on average, in each quadrant, suggesting that positions are maintained throughout life. Replacement teeth were numerous whatever the age and season, while the number of functional teeth was subject to variation. Symmetry of tooth development was evaluated by comparing teeth two by two from the opposite side in the four jaw quadrants of several specimens. Although the relative size of some replacement teeth fitted perfectly, the symmetry criterion was not reliable to predict the developmental stage of the opposite tooth, whether the pair of teeth compared was left-right or upper-lower. The best fit was found when comparing the size of successive replacement teeth from the front to the back of the jaw. Every replacement tooth that is 40-80% of its definitive size is followed, in the next position on the arcade, by a tooth that is, on average, 20% less developed. Considering teeth in alternate positions (even and odd series), each replacement tooth was a little more developed than the previous, more anterior, one (0.5-20% when the teeth are from 10-40% of their final size). The latter pattern showed that tooth replacement occurred in alternate positions from back to front, forming more or less regular rows (i.e., "Zahnreihen"). In Chalcides, the developmental stage of a replacement tooth in a position p can be accurately predicted provided the developmental stage of the replacement tooth in position p-1 or, to a lesser degree, in position p-2 is known. This finding will be particularly helpful when starting our structural and ultrastructural studies of tooth differentiation in this lizard.

Animals↗
PubMed2003

Postcanine dental form in the mustelidae and viverridae (Carnivora: Mammalia).

This study investigates whether the gross morphology of mustelid and viverrid postcanine dentitions corresponds with differences in diet. For each species, the predominant foods ingested are used to form predictions of dental form and measurements of the carnassial and molar teeth determine the extent of shearing and crushing surfaces on the postcanine teeth. Principal components analysis distinguishes species according to morphological differences in the dentition and these differences are compared with predictions of dental form based on diet. Dietarily specialized species are more likely to be correspondingly specialized in the dentition and species with varied food sources are more likely to possess dental characteristics that are generalized in function. Consumers of foods with high fracture resistance, such as vertebrate tissue and hard-surfaced invertebrates, possess specialized shearing or crushing postcanine teeth. On the other hand, species that consume foods of lesser fracture resistance, such as fruit and soft invertebrates, differ greatly in dental form and are more generalized in dental function. A few species possess postcanine dentitions that do not correspond with diet; the absence of dental-dietary correlation in these species suggests that other factors, such as phylogeny, are important in determining dental form.

Adaptation, Physiological↗
PubMed2002

Additional human remains from Blombos Cave, South Africa: (1999-2000 excavations).

The uppermost Middle Stone Age (MSA) layers at Blombos Cave contain high densities of Still Bay bifacial points. Information from other regional sites places the Still Bay prior to the Howiesons Poort industry, which has been dated at 65-70 ka. The Blombos Cave MSA strata have yielded nine human teeth or dental fragments. Four that were recovered during the 1997-1998 excavations have been published elsewhere. The remaining five were discovered during the 1999-2000 field seasons; these are described here. Three of the new specimens are deciduous teeth, and two are permanent premolar and molar crown fragments. The entire dental sample probably represents at least five and as many as seven individuals. The deciduous teeth from the upper MSA levels are likely to have been exfoliated in the cave. One deciduous tooth and the permanent tooth fragments from the lower MSA levels probably represent three individuals who died in or near the cave. The Blombos Cave premolars preserve horizontal circum-cervical striae suggestive of palliative tooth pick use. Approximately half of the permanent and deciduous crown diameters exceed those of recent Africans; for the remainder, the fossil values fall among modern African sample means. The Blombos Cave tooth crowns tend to be smaller than the majority of penecontemporaneous Neandertal teeth. The morphology of the Blombos Cave di is comparable to MSA homologues from the nearby, and presumably somewhat younger site of Die Kelders Cave 1.

Adult↗
PubMed2002

Skeletal and dental morphology of African papionins: unmasking a cryptic clade.

One of the more perplexing problems in primate systematics concerns the phyletic relationships of the large African monkeys--Mandrillus (including drills), Papio, Lophocebus and Cercocebus. For over twenty years, there has been molecular evidence that mangabeys are an unnatural group and that the terrestrial forms--Cercocebus--are the sister taxon of Mandrillus, while the arboreal forms--Lophocebus--are more closely allied with Papio. Nevertheless, most systematists have been reluctant to accept this scheme due to the lack of morphological evidence. In this paper, we undertake a detailed analysis of the scapula, humerus, radius, ulna, pelvis, femur and dentition of papionin primates. We identify a host of features shared by Cercocebus and Mandrillus to the exclusion of Lophocebus and Papio. The polarity of characters is established by examining an outgroup comprised of several species of Macaca. The features shared by Cercocebus and Mandrillus are functionally related to specific feeding and locomotor behaviors that include aggressive manual foraging, the processing of hard-object foods and the climbing of vertical trunks. We hypothesize that the ability to subsist on hard seeds and nuts gleaned from the forest floor is a key adaptation for the Cercocebus-Mandrillus clade.

Anatomy, Comparative↗
PubMed1995

Odontological identification of the victims of flight AI. IT 5148 air disaster Lyon-Strasbourg 20.01.1992.

The authors report on the contribution of odontological identification of the flight AI. IT 5148 air disaster victims, which occurred on 20th January 1992. The identification procedure was difficult due to large numbers of bodies and mutilations and required the involvement of multidisciplinary teams composed of odontologists, forensic pathologists, radiologists and biologists. The authors set up a simple, discriminant classification which was easy to handle by a multidisciplinary team. Four groups were defined according to the matching characteristics between ante and post mortem data. Perfect matching characteristics between ante and post mortem data were achieved in only 44 cases (Group A). Partial matching characteristics between ante and post mortem data were achieved in 12 cases (Group B). In 29 cases, the insufficiency or absence of odontological data (Group C and D) did not enable the victim to be identified. The results of the investigations showed that the dental examination alone enabled 17 victims to be identified and by including a morphological examination the figure reached 33. By the end of the investigations, 85 of the 87 victims were positively identified. Odontological identification is an essential, accurate and rapid method with allows a body to be identified from its dental characteristics. This anthropometrical method of identification is included with the descriptive and the biological methods. The authors present their experience in performing a formal identification of 44 victims in less than 15 days.

Accidents, Aviation↗
PubMed1999

The tooth-width relation of the incisors in closed bite.

On the basis of various opinions expressed in the literature, "closed bite" is associated in particular with an impaired front-tooth relation. Applying Tonn's index, evaluation of the records (models and cephalograms) of 1,100 patients, however, yielded no evidence of changes in the width ratio of the front teeth with regard to Angle classes, growth type, axial inclination of the central upper incisors, interincisal angle, or overbite.

Cephalometry↗
PubMed1999

Individual-based prediction of the size of the supporting zones in the permanent dentition. A comparison of the Moyers method with a unitary prediction value.

The aims of this individual-based study were 1. to assess the actual space requirements of the permanent canines and premolars, 2. to test the reliability of the Moyers method in predicting a space deficiency at the 75% confidence level and 3. to try to find a reliable unitary prediction value (= unitary value) as a possible substitute for the calculated Moyers values. Dental cast measurements were taken of the permanent dentition of 100 females and 100 males. The average sum of the widths of the maxillary and mandibular permanent canines and premolars was 20.8 mm (17.3 to 24.3 mm). The Moyers method could predict a maxillary space deficiency in 77.5% and a mandibular space deficiency in 65.5% of the subjects. The unitary value of 22.0 mm made it possible to predict a space deficiency in 83.5% of the subjects. The unitary value thus had a higher confidence level (83.5%) than the 75% level stated by Moyers and might thus substitute the calculated Moyers values. Furthermore, the unitary value is easy and quick to handle.

Bicuspid↗