Cranial morphology of Aegyptopithecus and Tarsius and the question of the tarsier-anthropoidean clade

New crania of the Oligocene anthropoidean Aegyptopithecus provide a test of the hypothesized tarsier-anthropoidean clade. Three cranial characters shared by Tarsius and some modern anthropoideans (apical interorbital septum, postorbital septum, "perbullar" carotid pathway) were examined. 1) An apical interorbital septum is absent in Aegyptopithecus. A septum does occur in Galago senegalensis (Lorisidae) and Microcebus murinus (Cheirogaleidae), so the presence of a septum is not strong evidence favoring a tarsiiform-anthropoidean clade. 2) In Aegyptopithecus and other anthropoideans, the postorbital septum is formed mainly by a periorbital flange of the zygomatic that extends medially from the lateral orbital margin onto or near the braincase. The postorbital plate of Tarsius is formed by frontal and alisphenoid flanges that extend laterally from the braincase to the zygomatic's frontal process, which is not broader than the postorbital bars of other prosimians. Periorbital flanges evolved in Tarsius for support or protection of the enormous eyes, as suggested by the occurrence of maxillary and frontal flanges that cup portions of the eye but do not separate it from temporal muscles. 3) The internal carotid artery of Aegyptopithecus enters the bulla posteriorly and crosses the anteroventral part of the promontorium. The tympanic cavity was probably separated from the anteromedial cavity by a septum stretching from the carotid channel to the ventrolateral bullar wall. In Tarsius, the carotid pathway is prepromontorial, and a septum stretches from the carotid channel to the posteromedial bullar wall. Quantitative analyses indicate that anterior carotid position has evolved because of erect head posture. The cranium of Oligocene anthropoideans thus provides no support for the hypothesized tarsier-anthropoidean clade.     

Molecular control of facial morphology

We present a developmental perspective on the concept of phylotypic and phenotypic stages of craniofacial development. Within orders of avians and mammals, a phylotypic period exists when the morphology of the facial prominences is minimally divergent. We postulate that species-specific facial variations arise as a result of subtle shifts in the timing and the duration of molecular pathway activity (e.g., heterochrony), and present evidence demonstrating a critical role for Wnt and FGF signaling in this process. The same molecular pathways that shape the vertebrate face are also implicated in craniofacial deformities, indicating that comparisons between and among animal species may represent a novel method for the identification of human craniofacial disease genes.     

Enamel thickness,microstructure and development in Afropithecus turkanensis

Afropithecus turkanensis, a 17-17.5 million year old large-bodied hominoid from Kenya, has previously been reported to be the oldest known thick-enamelled Miocene ape. Most investigations of enamel thickness in Miocene apes have been limited to opportunistic or destructive studies of small samples. Recently, more comprehensive studies of enamel thickness and microstructure in Proconsul, Lufengpithecus, and Dryopithecus, as well as extant apes and fossil humans, have provided information on rates and patterns of dental development, including crown formation time, and have begun to provide a comparative context for interpretation of the evolution of these characters throughout the past 20 million years of hominoid evolution. In this study, enamel thickness and aspects of the enamel microstructure in two A. turkanensis second molars were quantified and provide insight into rates of enamel apposition, numbers of cells actively secreting enamel, and the time required to form regions of the crown. The average value for relative enamel thickness in the two molars is 21.4, which is a lower value than a previous analysis of this species, but which is still relatively thick compared to extant apes. This value is similar to those of several Miocene hominoids, a fossil hominid, and modern humans. Certain aspects of the enamel microstructure are similar to Proconsul nyanzae, Dryopithecus laietanus, Lufengpithecus lufengensis, Graecopithecus freybergi and Pongo pygmaeus, while other features differ from extant and fossil hominoids. Crown formation times for the two teeth are 2.4-2.6 years and 2.9-3.1 years respectively. These times are similar to a number of extant and fossil hominoids, some of which appear to show additional developmental similarities, including thick enamel. Although thick enamel may be formed through several developmental pathways, most Miocene hominoids and fossil hominids with relatively thick enamel are characterized by a relatively long period of cuspal enamel formation and a rapid rate of enamel secretion throughout the whole cusp, but a shorter total crown formation time than thinner-enamelled extant apes.     

BCL3 gene role in facial morphology

BACKGROUND: Cleft lip (CL) with or without palate (CLP) and isolated cleft palate (CP) are etiologically complex diseases with interactions among various environmental and genetic factors. The aim of the current study was to identify association with genetic markers and phenotypic craniofacial data in patients with CL/CLP/CP parents. METHODS: Posteroanterior and lateral digital radiographs of the cranium were obtained from 74 parents of patients with CL/CLP/CP. One hundred seventy‐three patients with CL/CLP/CP and 190 controls were enrolled in the study for the association test. Five genetic markers of the IRF6 gene and 14 markers of the 19q13 locus were genotyped. Linear regression analysis was performed for the relationship of cephalometric measurements with genotype data adjusted for age, gender, and cleft type. Chi‐square and transmission disequilibrium tests were performed to evaluate differences in alleles of the BCL3 gene. Positive findings were replicated in an independent sample (n = 95) of patients with CL/CLP/CP parents. RESULTS: Genetic markers of the BCL3 gene at 19q13, rs7257231, and rs1979377 in the familial association test and rs10401176 in the case‐control association test, were associated with craniofacial phenotype. Carriers of BCL3 allele rs7257231T had longer posterior cranial bases than noncarriers (p_adjusted = 0.0028), and in the familial‐based association test showed the statistically strongest relationship (p_adjusted = 0.05) to phenotype. Relation of rs7257231 to facial formation was confirmed in the replication group (p = 0.0024). CONCLUSIONS: The results indicate that BCL3, which has functions related to cell adhesion and whose downregulation can cause disruption of ectodermal development, is likely to be important in facial formation. Birth Defects Research (Part A), 2012. © 2012 Wiley Periodicals, Inc.     

Australopithecine taxonomy and phylogeny in light of facial morphology

The beginning of specialization characterizing the robust australopithecines is manifested in almost every aspect of the masticatory system of Australopithecus africanus. Of particular significance is the presence of two massive bony columns on both sides of the nasal aperture that support the anterior portion of the palate. These columns--the anterior pillars--are viewed as a structural response to the greater occlusal load stemming from the beginning stages of molarization of the premolars and exerted on the more anterior part of the dental arcade. In A. africanus the molarization process is, indeed, just in its initial phase, but the still considerable protrusion of the palate relative to the more peripheral facial frame increases the need for pillars. The anterior pillars and the advancement of the inferior part of the infraorbital plate (the origin of the masseter) play a major role in molding the facial topography of A. africanus. The absence of the pillars and the common position of the masseteric origin lead us to define the face of A. afarensis as the most primitive of the australopithecines and allow us to discriminate between its facial morphology and that of A. africanus. The presence of anterior pillars in the face of the latter places it clearly in the robust australopithecine clade.     

New evidence for canine dietary function in Afropithecus turkanensis

Despite considerable post-cranial and cranial morphological overlap with Proconsul, Afropithecus turkanensis is distinguished from that taxon by a suite of anterior dental and gnathic characters shared in common with extant pitheciin monkeys (i.e. low crowned, robust and laterally splayed canines, procumbent incisors, prognathic premaxilla, powerful temporalis muscles, reduced or absent maxillary sinuses, and deep mandibular corpora). Pitheciins are unique among living anthropoids because their canines serve a habitual dietary function and are not strictly influenced by inter-male competition. Given the functional association between pitheciin canine morphological specializations and sclerocarp foraging, a feeding strategy where the hard pericarps of unripe fruit are mechanically deformed by the canines, it has been suggested that Afropithecus may also have used its canines in a dietary context. This is confirmed by quantitative morphometric analyses of Afropithecus canine curvature and basal dimensions demonstrating that Afropithecus and extant pitheciins (Chiropotes, Cacajao) are distinguished from all other anthropoids by pronounced and evenly distributed mesial canine crown contours as well as greater resistance to canine bending in both the mesiodistal and labiolingual axes. In addition, Afropithecus, Chiropotes and Cacajao are also shown to have significantly longer and more curved premaxillae with greater incisor procumbency that effectively isolates the incisor and canine functional complexes. These morphological similarities are a result of convergence and not a shared derived ancestry. Despite their considerable morphological overlap, it is unlikely that Afropithecus and extant pitheciin diets are identical given significant dissimilarities in their post-canine morphology, maximum angular gape and body size. Nevertheless, Afropithecus canine dietary function is unique among hominoids and may have been a key component for the expansion of hominoids into Eurasia at the end of the early Miocene.     

Similarities and differences in Chinese and Caucasian adults' use of facial cues for trustworthiness judgments

Background

All cultural groups in the world place paramount value on interpersonal trust. Existing research suggests that although accurate judgments of another''s trustworthiness require extensive interactions with the person, we often make trustworthiness judgments based on facial cues on the first encounter. However, little is known about what facial cues are used for such judgments and what the bases are on which individuals make their trustworthiness judgments.

Methodology/Principal Findings

In the present study, we tested the hypothesis that individuals may use facial attractiveness cues as a “shortcut” for judging another''s trustworthiness due to the lack of other more informative and in-depth information about trustworthiness. Using data-driven statistical models of 3D Caucasian faces, we compared facial cues used for judging the trustworthiness of Caucasian faces by Caucasian participants who were highly experienced with Caucasian faces, and the facial cues used by Chinese participants who were unfamiliar with Caucasian faces. We found that Chinese and Caucasian participants used similar facial cues to judge trustworthiness. Also, both Chinese and Caucasian participants used almost identical facial cues for judging trustworthiness and attractiveness.

Conclusions/Significance

The results suggest that without opportunities to interact with another person extensively, we use the less racially specific and more universal attractiveness cues as a “shortcut” for trustworthiness judgments.     

Discriminating power of localized three-dimensional facial morphology

Many genetic syndromes involve a facial gestalt that suggests a preliminary diagnosis to an experienced clinical geneticist even before a clinical examination and genotyping are undertaken. Previously, using visualization and pattern recognition, we showed that dense surface models (DSMs) of full face shape characterize facial dysmorphology in Noonan and in 22q11 deletion syndromes. In this much larger study of 696 individuals, we extend the use of DSMs of the full face to establish accurate discrimination between controls and individuals with Williams, Smith-Magenis, 22q11 deletion, or Noonan syndromes and between individuals with different syndromes in these groups. However, the full power of the DSM approach is demonstrated by the comparable discriminating abilities of localized facial features, such as periorbital, perinasal, and perioral patches, and the correlation of DSM-based predictions and molecular findings. This study demonstrates the potential of face shape models to assist clinical training through visualization, to support clinical diagnosis of affected individuals through pattern recognition, and to enable the objective comparison of individuals sharing other phenotypic or genotypic properties.     

Morphological integration of soft-tissue facial morphology in Down Syndrome and siblings

Down syndrome (DS), resulting from trisomy of chromosome 21, is the most common live-born human aneuploidy. The phenotypic expression of trisomy 21 produces variable, though characteristic, facial morphology. Although certain facial features have been documented quantitatively and qualitatively as characteristic of DS (e.g., epicanthic folds, macroglossia, and hypertelorism), all of these traits occur in other craniofacial conditions with an underlying genetic cause. We hypothesize that the typical DS face is integrated differently than the face of non-DS siblings, and that the pattern of morphological integration unique to individuals with DS will yield information about underlying developmental associations between facial regions. We statistically compared morphological integration patterns of immature DS faces (N = 53) with those of non-DS siblings (N = 54), aged 6-12 years using 31 distances estimated from 3D coordinate data representing 17 anthropometric landmarks recorded on 3D digital photographic images. Facial features are affected differentially in DS, as evidenced by statistically significant differences in integration both within and between facial regions. Our results suggest a differential affect of trisomy on facial prominences during craniofacial development.     

New faces of Aegyptopithecus from the Oligocene of Egypt

Three recently discovered faces of Aegyptopithecus zeuxis from the Oligocene Jebel Qatrani Formation of Egypt provide new information about the shape and variation of the facial cranium, the earliest preserved for a presumed forerunner of apes and humans. Although varying considerably in details of shape and proportion, the new finds and a skull found in 1966 all appear to be of males, a conclusion based in part on the development of temporal and sagittal crests and on the large size of upper canines or their sockets (female canines are much smaller). The snouts of the three new faces all are shorter and broader than that of the earlier found skull as reconstructed. As in most later species of Anthropoidea, variation between these specimens is high.Aegyptopithecus helps define the nature of the oldest Anthropoidea and generally most resembles later-occurring apes. Many features, both derived and shared primitive, link Aegyptopithecus, the large Miocene great apes of the Proconsul group, and modern great apes. That these shared features and proportions are not direct allometric consequences of body size is indicated by Aegyptopithecus' resemblance to the large apes and its many distinctions from similar-sized Hylobates.In Aegyptopithecus brain volume scales smaller than in later catarrhines relative to facial size, the ectotympanic tube is less developed and the premaxilla is more primitive than in later higher primates. In closure of orbits and conformation of forehead, face and dentition, Aegyptopithecus closely resembles higher primates and not prosimians. Taken together, its overall cranial and dental anatomy constitutes one of the most important connecting links in primate evolutionary history.     

Non-metric features in the ulna of Aegyptopithecus, Alouatta, Ateles, and Lagothrix.

A comparison of the non-metric features of the ulnar fragment (YPM 23940) referred to Aegyptopithecus zeuxis with those in the same bone of Alouatta, Ateles, and Lagothrix -- the three living taxa whose ulnae most closely resemble that of the fossil -- reveals that the closest similarities of the fragment are with the ulna of Alouatta.     

Age at first molar emergence in early Miocene Afropithecus turkanensis and life-history evolution in the Hominoidea

Among primates, age at first molar emergence is correlated with a variety of life history traits. Age at first molar emergence can therefore be used to broadly infer the life histories of fossil primate species. One method of determining age at first molar emergence is to determine the age at death of fossil individuals that were in the process of erupting their first molars. This was done for an infant partial mandible of Afropithecus turkanensis (KNM-MO 26) from the approximately 17.5 Ma site of Moruorot in Kenya. A range of estimates of age at death was calculated for this individual using the permanent lateral incisor germ preserved in its crypt, by combining the number and periodicity of lateral enamel perikymata with estimates of the duration of cuspal enamel formation and the duration of the postnatal delay in the inception of crown mineralization. Perikymata periodicity was determined using daily cross striations between adjacent Retzius lines in thin sections of two A. turkanensis molars from the nearby site of Kalodirr. Based on the position of the KNM-MO 26 M(1)in relation to the mandibular alveolar margin, it had not yet undergone gingival emergence. The projected time to gingival emergence was estimated based on radiographic studies of M(1)eruption in extant baboons and chimpanzees.The estimates of age at M(1)emergence in KNM-MO 26 range from 28.2 to 43.5 months, using minimum and average values from extant great apes and humans for the estimated growth parameters. Even the absolute minimum value is well outside the ranges of extant large Old World monkeys for which there are data (12.5 to <25 months), but is within the range of chimpanzees (25.7 to 48.0 months). It is inferred, therefore, that A. turkanensis had a life history profile broadly like that of Pan. This is additional evidence to that provided by Sivapithecus parvada (Function, Phylogeny, and Fossils: Miocene Hominoid Evolution and Adaptations, 1997, 173) that the prolonged life histories characteristic of extant apes were achieved early in the evolutionary history of the group. However, it is unclear at present whether life-history prolongation in apes represents the primitive catarrhine pace of life history extended through phyletic increase in body mass, or whether it is derived with respect to a primitive, size-adjusted life history that was broadly intermediate between those of extant hominoids and cercopithecoids. Life history evolution in primates as a whole may have occurred largely through a series of grade-shifts, with the establishment of fundamental life-history profiles early in the histories of major higher taxa. These may have included shifts that were largely body mass dependent, as well as those that occurred in the absence of significant changes in body mass.     

两类植物型沙丘上植物群落的异同及其对沙丘形态的响应

为探究相同环境条件下发育的两类植物型沙丘上植物群落的异同点,以及相异点与沙丘形态的关系,对毛乌素沙地南缘盐碱地上相间分布的抛物线形沙丘和白刺灌丛沙丘分别进行形态学、植物群落学及土壤理化性质的调查分析。结果显示:抛物线形沙丘的水平尺度虽为白刺灌丛沙丘的12-23倍,但两类沙丘上物种数相当,其植物分属12科31属39种和12科30属33种,均以菊科、藜科、禾本科、豆科植物为主(占70%以上),其中共有植物17种,群落相似度0.66;两类沙丘上的群落建群种不同,优势种的重叠度较低,抛物线形沙丘的不同部位共统计到7个植物群丛,可分为沙生植物群落和喜湿耐盐碱群落,白刺灌丛沙丘上均以白刺为建群种,油蒿、冰草、雾冰藜、沙蓬、狗尾草为主要优势种;沙丘形态造成其不同部位风沙活动及土壤水分、PH值和全盐含量的差异是两类沙丘上植物群落相异的重要影响因素。     

Evaluating developmental shape changes in Homo antecessor subadult facial morphology

The fossil ATD6-69 from Atapuerca, Spain, dated to ca. 900 ka (thousands of years ago) has been suggested to mark the earliest appearance of modern human facial features. However, this specimen is a subadult and the interpretation of its morphology remains controversial, because it is unclear how developmental shape changes would affect the features that link ATD6-69 to modern humans. Here we analyze ATD6-69 in an evolutionary and developmental context. Our modern human sample comprises cross-sectional growth series from four populations. The fossil sample covers human specimens from the Pleistocene to the Upper Paleolithic, and includes several subadult Early Pleistocene humans and Neanderthals. We digitized landmarks and semilandmarks on surface and CT scans and analyzed the Procrustes shape coordinates using multivariate statistics. Ontogenetic allometric trajectories and developmental simulations were employed in order to identify growth patterns and to visualize potential adult shapes of ATD6-69. We show that facial differences between modern and archaic humans are not exclusively allometric. We find that while postnatal growth further accentuates the differences in facial features between Neanderthals and modern humans, those features that have been suggested to link ATD6-69's morphology to modern humans would not have been significantly altered in the course of subsequent development. In particular, the infraorbital depression on this specimen would have persisted into adulthood. However, many of the facial features that ATD6-69 shares with modern humans can be considered to be part of a generalized pattern of facial architecture. Our results present a complex picture regarding the polarity of facial features and demonstrate that some modern human-like facial morphology is intermittently present in Middle Pleistocene humans. We suggest that some of the facial features that characterize recent modern humans may have developed multiple times in human evolution.     

Opposite effects on facial morphology due to gene dosage sensitivity

Sequencing technology is increasingly demonstrating the impact of genomic copy number variation (CNV) on phenotypes. Opposing variation in growth, head size, cognition and behaviour is known to result from deletions and reciprocal duplications of some genomic regions. We propose normative inversion of face shape, opposing difference from a matched norm, as a basis for investigating the effects of gene dosage on craniofacial development. We use dense surface modelling techniques to match any face (or part of a face) to a facial norm of unaffected individuals of matched age, sex and ethnicity and then we reverse the individual’s face shape differences from the matched norm to produce the normative inversion. We demonstrate for five genomic regions, 4p16.3, 7q11.23, 11p15, 16p13.3 and 17p11.2, that such inversion for individuals with a duplication or (epi)-mutation produces facial forms remarkably similar to those associated with a deletion or opposite (epi-)mutation of the same region, and vice versa. The ability to visualise and quantify face shape effects of gene dosage is of major benefit for determining whether a CNV is the cause of the phenotype of an individual and for predicting reciprocal consequences. It enables face shape to be used as a relatively simple and inexpensive functional analysis of the gene(s) involved.     

Tooth wear, Neanderthal facial morphology and the anterior dental loading hypothesis

The Anterior Dental Loading Hypothesis states that the unique Neanderthal facial and dental anatomy was an adaptive response to the regular application of heavy forces resulting from both the masticatory and cultural use of the anterior teeth. Heavy anterior tooth wear frequently observed in Neanderthal specimens is cited as a main source of evidence for heavy forces being applied to these teeth. From this, it might be predicted that the wear shown on the anterior teeth of Neanderthals would greatly exceed that of the posterior teeth and that this differential would be greater than in other hominins with different facial morphologies.In this paper, a new method of examining tooth wear patterns is used to test these predictions in a large assemblage of Late Pleistocene hominins and a group of recent hunter-gatherers from Igloolik, Canada. The results show that all Late Pleistocene hominins, including Neanderthals, had heavily worn anterior teeth relative to their posterior teeth but, contrary to expectations, this was more pronounced in the modern humans than in the Neanderthals. The Igloolik Inuit showed heavier anterior tooth wear relative to their posterior teeth than any Late Pleistocene hominins. There was, however, a characteristic Neanderthal pattern in which wear was more evenly spread between anterior teeth than in modern humans. Overall, the evidence presented here suggests that all Late Pleistocene hominins habitually applied heavy forces between their anterior teeth and that Neanderthals were not exceptional in this regard. These results therefore does not support the Anterior Dental Loading Hypothesis.     

The origins of species-specific facial morphology: the proof is in the pigeon

One of the principal objectives of developmental research isto understand morphogenesis and in doing so, gain insights intothe genetic basis of variation observed throughout the AnimalKingdom. In this review we take an approach, first popularizedby Darwin, to understanding how diversity is created by usingthe domesticated pigeon as a model organism. Nearly 3000 yearsof selective breeding has produced an astonishing array of featherpatterns, behaviors, skeletal shapes, and body sizes. Cumulatively,these features make the pigeon an exemplar of morphologicalvariation. Our research interests center around exploiting theunique properties of domesticated pigeons to gain critical insightsinto the molecular and cellular basis for craniofacial variation.