The evolution of palate shape in the Lepilemur-Cheirogaleidae clade (Primates: Strepsirrhini).

OBJECTIVES: Phylogenies consistently group the folivorous Lepilemur species with the small-bodied insectivorous-frugivorous cheirogaleids. Juvenile lepilemurs and adult cheirogaleids share allometries in most aspects of skull morphology, except the palate. We investigated potential influences on palate shape in these taxa and several outgroups using geometric morphometrics. MATERIALS AND METHODS: Our sample included representatives of four extant strepsirrhine families, Cheirogaleidae (including Lepilemurinae), Lemuridae, Indriidae, and Galagidae, and one subfossil Megaladapis. Our dataset comprised 32 landmarks collected from 397 specimens representing 15 genera and 28 species, and was analyzed using generalized procrustes analyses and between group principal component analysis. We explored the influence of size, phylogeny, diet, and the propagation of loud vocalizations on palate shape. RESULTS: While congeneric species clustered within the morphospace, the phylomorphospace did not mirror molecular phylogenetic hypotheses of higher-order relationships. Four palate forms were distinguished within the Cheirogaleidae. Diet, strongly linked to body size, had the single greatest influence on palate shape. The production of long-distance advertisement calls was most often associated with positive scores on the PC1 axis. DISCUSSION: Our results suggest that the extensive variation in palate shape among Cheirogaleidae is related to dietary shifts that accompanied changes in body size during the clade's radiation. Molecular phylogenies indicate that cheirogaleid diversification involved repeated dwarfing events, which in turn drove dietary shifts from ancestral folivory-frugivory to frugivory, gummivory, and faunivory in the descendant species. The elongated Lepilemur palate is probably related to accelerated eruption of the cheek teeth to render juveniles competent to shear leaves upon weaning.

A comparison of relief estimates used in three-dimensional dental topography.

OBJECTIVES: Topographic estimates of dental relief are now commonly used to make dietary inferences from the teeth of extant and extinct primates. We thoroughly compared commonly used relief estimates in an effort to help researchers decide which variable best suits their objectives. MATERIALS AND METHODS: We combined a total of three datasets: five theoretical models built to compare the effect of tooth complexity and basin depth on relief estimates, a dataset of 110 lower molars of prosimians, and a dataset of 25 upper molars of apes. We investigated intra-mesh variation and tooth average relief, estimated from slope and three different relief indices, according to four criteria: (1) the ability to map relief on topographic maps, (2) the correlation with other relief estimates, (3) the ability to separate high-relief molars of folivores from deep-relief molars of insectivores in prosimians, and (4) the influence of surface complexity on relief estimates in apes. RESULTS: We found that polygon slope and relief index are linked by a mathematical relation. Tooth average slope and all relief indices are strongly correlated. In contrast, relief estimates are moderately correlated to cusp elevation. One relief index of four relief estimates had an excellent ability to separate high-relief from deep-relief molars in prosimians, whereas slope could not separate them. No significant effect of tooth complexity on dental relief could be detected in apes. CONCLUSIONS: Because slope and relief indices are highly correlated, it is strongly recommended not to combine them in multivariate analysis. Still, slope and relief indices show interesting differences in scaling, graphical representation, computation method, and ability to separate high-relief and deep-relief molars. Our results also suggest that slope and relief indices can vary independently of tooth complexity and are moderately affected by mean cusp elevation in apes.

Convergent evolution in the Euarchontoglires.

Convergence-the independent evolution of similar phenotypes in distantly related clades-is a widespread and much-studied phenomenon. An often-cited, but hitherto untested, case of morphological convergence is that between the aye-aye and squirrels. The aye-aye (Daubentonia madagascariensis) is a highly unusual lemuriform primate that has evolved a dentition similar to that of rodents: it possesses large, ever-growing incisors which it uses to strip the bark from trees in order to feed on wood-boring beetle larvae. Indeed, such is the similarity that some of the earliest classifications of the aye-aye placed it in the squirrel genus Sciurus Here, we aimed to test the degree of convergence between the skulls and lower jaws of squirrels and the aye-aye. Three-dimensional landmarks were recorded from the crania and mandibles of 46 taxa representing the majority of families in the Euarchontoglires. Results were plotted as phylomorphospaces and convergence measures were calculated. The convergence between squirrels and the aye-aye was shown to be statistically significant for both the cranium and mandible, although the mandibles seem to converge more closely in shape. The convergence may indicate strong functional drivers of morphology in these taxa, i.e. the use of the incisors to produce high bite forces during feeding. Overall, we have shown that this classic case of convergence stands up to quantitative analysis.

Reversible Deactivation of Motor Cortex Reveals Functional Connectivity with Posterior Parietal Cortex in the Prosimian Galago (Otolemur garnettii).

We examined the functional macrocircuitry of frontoparietal networks in the neocortex of prosimian primates (Otolemur garnettii) using a microfluidic thermal regulator to reversibly deactivate selected regions of motor cortex (M1). During deactivation of either forelimb or mouth/face movement domains within M1, we used long-train intracortical microstimulation techniques to evoke movements from the rostral division of posterior parietal cortex (PPCr). We found that deactivation of M1 movement domains in most instances abolished movements evoked in PPCr. The most common effect of deactivating M1 was to abolish evoked movements in a homotopic domain in PPCr. For example, deactivating M1 forelimb lift domains resulted in loss of evoked movement in forelimb domains in PPCr. However, at some sites, we also observed heterotopic effects; deactivating a specific domain in M1 (e.g., forelimb lift) resulted in loss of evoked movement in a different movement domain in PPCr (e.g., hand-to-mouth or eye-blink). At most sites examined in PPCr, rewarming M1 resulted in a reestablishment of the baseline movement at the same amplitude as that observed before cooling. However, at some sites, reactivation did not result in a return to baseline movement or to the full amplitude of the baseline movement. We discuss our findings in the context of frontoparietal circuits and how they may subserve a repertoire of ecologically relevant behaviors. SIGNIFICANCE STATEMENT: The posterior parietal cortex (PPC) of primates integrates sensory information used to guide movements. Different modules within PPC and motor cortex (M1) appear to control various motor behaviors (e.g., reaching, defense, and feeding). How these modules work together may vary across species and may explain differences in dexterity and even the capacity for tool use. We investigated the functional connectivity of these modules in galagos, a prosimian primate with relatively simple frontoparietal circuitry. By deactivating a reaching module in M1, we interfered with the function of similar PPC modules and occasionally unrelated PPC modules as well (e.g., eye blink). This circuitry in galagos, therefore, is more complex than in nonprimates, indicating that it has been altered with the expansion of primate PPC.

New euprimate postcrania from the early Eocene of Gujarat, India, and the strepsirrhine-haplorhine divergence.

The oldest primates of modern aspect (euprimates) appear abruptly on the Holarctic continents during a brief episode of global warming known as the Paleocene-Eocene Thermal Maximum, at the beginning of the Eocene (∼56 Ma). When they first appear in the fossil record, they are already divided into two distinct clades, Adapoidea (basal members of Strepsirrhini, which includes extant lemurs, lorises, and bushbabies) and Omomyidae (basal Haplorhini, which comprises living tarsiers, monkeys, and apes). Both groups have recently been discovered in the early Eocene Cambay Shale Formation of Vastan lignite mine, Gujarat, India, where they are known mainly from teeth and jaws. The Vastan fossils are dated at ∼54.5 Myr based on associated dinoflagellates and isotope stratigraphy. Here, we describe new, exquisitely preserved limb bones of these Indian primates that reveal more primitive postcranial characteristics than have been previously documented for either clade, and differences between them are so minor that in many cases we cannot be certain to which group they belong. Nevertheless, the small distinctions observed in some elements foreshadow postcranial traits that distinguish the groups by the middle Eocene, suggesting that the Vastan primates-though slightly younger than the oldest known euprimates-may represent the most primitive known remnants of the divergence between the two great primate clades.

Lower molar shape and size in prosimian and platyrrhine primates.

The goal of this research is to evaluate the relative strength of the influences of diet, size, and phylogenetic signal on dental geometric shape. Accurate comprehension of these factors and their interaction is important for reconstructing diet and deriving characters for a cladistic analysis in fossil primates. Geometric morphometric analysis is used to identify axes of shape variation in the lower second molars of (a) prosimian primates and (b) platyrrhines. Landmarks were placed on µCT-generated surface renderings. Landmark configurations were aligned using generalized Procrustes analysis. Principal components analysis and phylogenetic principal components analysis (pPCA) were performed on species average landmark co-ordinates. pPCs were examined with phylogenetic generalized least squares analysis for association with size and with diet. PCs from both phylogenetic and non-phylogenetic analyses were sufficient to separate species by broad dietary categories, including insectivores and folivores. In neither analysis was pPC1 correlated with tooth size, but some other pPCs were significantly correlated with size. The pattern of association between pPCs and size altered when centroid size and dietary variables were combined in the model; effects of diet factors typically exceeded effects of size. These results indicate a dominant phylogenetic and dietary signal in molar shape but also show some shape change correlated with size in the absence of obvious dietary associations. Geometric morphometric analysis appears to be useful for tracking functional traits in molars, particularly in tracking differences between folivorous and insectivorous species.

Craniomandibular signals of diet in adapids.

OBJECTIVES: The craniomandibular morphology of the adapid primates of Europe, especially Adapis and Leptadapis (sensu lato), suggests that they possessed enormous jaw adductor muscles. The goal of this study is to estimate jaw adductor muscle mass, physiological cross-sectional area (PCSA), and fiber length in adapid primates from the Eocene of Europe. We also estimated muscle leverage, bite force, and gape parameters. MATERIALS AND METHODS: We use bony morphology and osteological correlates of soft tissues in a sample of extant strepsirrhines to estimate these soft-tissue and performance variables in Adapis and Leptadapis. RESULTS: Our results suggest that, compared to a broad sample of extant strepsirrhines, Adapis and Leptadapis had relatively great jaw adductor muscle mass, PCSA, and bite force. They had moderately great jaw adductor leverage but no sign of adaptation for wide gapes. There is no support for the hypothesis that either adapid was a gouger. DISCUSSION: Our estimates support the inference that Adapis and Leptadapis were primarily folivorous, perhaps also consuming small to medium-sized tough fruits, nuts, and seeds. Explanations for the likely extreme development of the jaw adductor muscles in adapids remain speculative. These include (1) foods that were generally tougher and/or of higher yield strength than those eaten by strepsirrhines today, (2) using the muscles "in shifts" to avoid muscle fatigue in the context of an obdurate diet, and (3) potential constraints on reshaping of the skull for more efficient food processing.

Dental topography of platyrrhines and prosimians: convergence and contrasts.

Dental topographic analysis is the quantitative assessment of shape of three-dimensional models of tooth crowns and component features. Molar topographic curvature, relief, and complexity correlate with aspects of feeding behavior in certain living primates, and have been employed to investigate dietary ecology in extant and extinct primate species. This study investigates whether dental topography correlates with diet among a diverse sample of living platyrrhines, and compares platyrrhine topography with that of prosimians. We sampled 111 lower second molars of 11 platyrrhine genera and 121 of 20 prosimian genera. For each tooth we calculated Dirichlet normal energy (DNE), relief index (RFI), and orientation patch count (OPCR), quantifying surface curvature, relief, and complexity respectively. Shearing ratios and quotients were also measured. Statistical analyses partitioned effects of diet and taxon on topography in platyrrhines alone and relative to prosimians. Discriminant function analyses assessed predictive diet models. Results indicate that platyrrhine dental topography correlates to dietary preference, and platyrrhine-only predictive models yield high rates of accuracy. The same is true for prosimians. Topographic variance is broadly similar among platyrrhines and prosimians. One exception is that platyrrhines display higher average relief and lower relief variance, possibly related to lower relative molar size and functional links between relief and tooth longevity distinct from curvature or complexity. Explicitly incorporating phylogenetic distance matrices into statistical analyses of the combined platyrrhine-prosimian sample results in loss of significance of dietary effects for OPCR and SQ, while greatly increasing dietary significance of RFI.

New insights into the ear region anatomy and cranial blood supply of advanced stem Strepsirhini: evidence from three primate petrosals from the Eocene of Chambi, Tunisia.

We report the discovery of three isolated primate petrosal fragments from the fossiliferous locality of Chambi (Tunisia), a primate-bearing locality dating from the late early to the early middle Eocene. These fossils display a suite of anatomical characteristics otherwise found only in strepsirhines, and as such might be attributed either to Djebelemur or/and cf. Algeripithecus, the two diminutive stem strepsirhine primates recorded from this locality. Although damaged, the petrosals provide substantial information regarding the ear anatomy of these advanced stem strepsirhines (or pre-tooth-combed primates), notably the patterns of the pathway of the arterial blood supply. Using µCT-scanning techniques and digital segmentation of the structures, we show that the transpromontorial and stapedial branches of the internal carotid artery (ICA) were present (presence of bony tubes), but seemingly too small to supply enough blood to the cranium alone. This suggests that the ICA was not the main cranial blood supply in stem strepsirhines, but that the pharyngeal or vertebral artery primitively ensured a great part of this role instead, an arterial pattern that is reminiscent of modern cheirogaleid, lepilemurid lemuriforms and lorisiforms. This could explain parallel loss of the ICA functionality among these families. Specific measurements made on the cochlea indicate that the small strepsirhine primate(s) from Chambi was (were) highly sensitive to high frequencies and poorly sensitive to low frequencies. Finally, variance from orthogonality of the plane of the semicircular canals (SCs) calculated on one petrosal (CBI-1-569) suggests that Djebelemur or cf. Algeripithecus likely moved (at least its head) in a way similar to that of modern mouse lemurs.

Molar size and diet in the Strepsirrhini: implications for size-adjustment in studies of primate dental adaptation.

Among the Strepsirrhini, molar size does not exhibit a consistent dietary signal when body mass is used to size-adjust molar dimensions. This observation is also true for anthropoid primates, but when postcanine size is expressed relative to the size of the facial skeleton in this clade, folivorous anthropoids tend to have relatively larger postcanine teeth than anthropoids in other dietary categories. The contrast in the results generated by these two independent size variables appears to be related to systematic differences in facial size in the Anthropoidea, particularly between short-faced colobines and long-faced cercopithecines. The goal of this study was to determine whether a similar pattern of relationships characterizes strepsirrhines. Data on molar area, facial size, body mass, and diet for forty-three extant strepsirrhines and seven subfossil lemurs were analyzed using phylogenetic generalized least squares. Results indicate that strepsirrhine folivores tend to have larger molars than frugivores relative to the size of the facial skeleton. Insectivorous species exhibit a wide range of variation in relative molar size that appears to be taxonomically patterned: lorisids in this dietary category resemble folivores, whereas galagids resemble frugivores. These results confirm the generality of the anthropoid pattern and support the idea that, in some contexts, it may be useful to consider elements of the masticatory system relative to their functional and developmental environments rather than to overall organismal size. The biological significance of having large postcanine teeth relative to the size of the face, but not body mass, is discussed with reference to a model that identifies the size of the oral cavity as the most functionally relevant standard for assessing the relative size of the postcanine dentition.

Spatial and temporal ecological diversity amongst Eocene primates of France: evidence from teeth.

Diet is of paramount importance in the life of a primate. It is also highly variable, as potential food sources vary in spatial distribution and availability over time. The fossil record, due to its fragmentary nature, offers few possibilities to assess the dietary range of a given primate across its spatial and temporal distribution. Here we focus on three taxa, Leptadapis magnus (Adapidae, Adapiformes), Necrolemur cf. antiquus (Microchoeridae, Omomyiformes), and Pseudoloris parvulus (Microchoeridae, Omomyiformes). These taxa occur at different localities of the Late Eocene in the south of France ranging from MP16 (Robiac, Lavergne; 39 Ma), MP17a (La Bouffie, Euzet, Fons 4; 38 Ma) to MP17b (Perrière; 37 Ma). Diets of fossil taxa are assessed here by dental microwear analysis using a comparative database of 11 species of living strepsirhines. On the whole, leaves were a preferred food for the large-bodied Leptadapis (4-5 kg). However, the diet of this taxon varied from a mix of leaves and fruit at La Bouffie, a closed tropical rain forest environment, to a strictly leaf-eating one in the more open environment of Perrière. Based on body mass (200-350 g) and dental microwear patterns, Necrolemur had a mainly fruit-based diet, perhaps supplemented by insects. However, the comparison of the different localities reveals the dietary range of this small-bodied omomyiform which seems to vary between insects and a much softer diet. Pseudoloris had a diet strictly based on insects. Contrary to Leptadapis or Necrolemur, its diet seems to have been confined to insects whatever the locality considered.

Lemur habitat and dental senescence in Ranomafana National Park, Madagascar.

Not only can teeth provide clues about diet, but they also can be indicators of habitat quality. Conspecific groups living in different habitats with different kinds of foods may exhibit different rates of dental attrition because their teeth are less well adapted to some foods than to others. Ecological disequilibrium describes the situation in which animals live in habitats to which they are relatively poorly adapted. We test whether dental senescence, the wear-related decrease in dental functionality that is associated with decreased survival of infants born to older Propithecus edwardsi females, can be explained by ecological disequilibrium. Specifically, we compare the rates of dental wear in sifaka groups living in nearby habitats that differ in the degree of anthropogenically induced disturbance. We hypothesize that sifakas living in disturbed areas have an unusual rate of tooth wear compared to those living in a more pristine area, and that dental senescence is a consequence of an atypically high wear rate in a degraded habitat. To test whether habitat quality affects tooth wear more generally, we compare rates of use-wear in two subsets of Microcebus rufus living in either relatively undisturbed or disturbed habitats. Contrary to our predictions, we did not detect different rates of tooth wear in disturbed versus undisturbed habitats for either species and consider that reproductively detrimental dental senescence in P. edwardsi females is unlikely to be a pathological consequence of ecological disequilibrium.

Diet drove brain and dental morphological coevolution in strepsirrhine primates.

The evolution of the remarkably complex primate brain has been a topic of great interest for decades. Multiple factors have been proposed to explain the comparatively larger primate brain (relative to body mass), with recent studies indicating diet has the greatest explanatory power. Dietary specialisations also correlate with dental adaptations, providing a potential evolutionary link between brain and dental morphological evolution. However, unambiguous evidence of association between brain and dental phenotypes in primates remains elusive. Here we investigate the effect of diet on variation in primate brain and dental morphology and test whether the two anatomical systems coevolved. We focused on the primate suborder Strepsirrhini, a living primate group that occupies a very wide range of dietary niches. By making use of both geometric morphometrics and dental topographic analysis, we extend the study of brain-dental ecomorphological evolution beyond measures of size. After controlling for allometry and evolutionary relatedness, differences in brain and dental morphology were found between dietary groups, and brain and dental morphologies were found to covary. Historical trajectories of morphological diversification revealed a strong integration in the rates of brain and dental evolution and similarities in their modes of evolution. Combined, our results reveal an interplay between brain and dental ecomorphological adaptations throughout strepsirrhine evolution that can be linked to diet.

The Hadropithecus conundrum reconsidered, with implications for interpreting diet in fossil hominins.

The fossil 'monkey lemur' Hadropithecus stenognathus has long excited palaeontologists because its skull bears an astonishing resemblance to those of robust australopiths, an enigmatic side branch of the human family tree. Multiple lines of evidence point to the likelihood that these australopiths ate at least some 'hard', stress-limited food items, but conflicting data from H. stenognathus pose a conundrum. While its hominin-like craniofacial architecture is suggestive of an ability to generate high bite forces, details of its tooth structure suggest that it was not well equipped to withstand the forces imposed by cracking hard objects. Here, we use three-dimensional digital reconstructions and finite-element analysis to test the hard-object processing hypothesis. We show that Archaeolemur sp. cf. A. edwardsi, a longer-faced close relative of H. stenognathus that lacked hominin convergences, was probably capable of breaking apart large, stress-limited food items, while Hadropithecus was better suited to processing small, displacement-limited (tougher but more compliant) foods. Our suggestion that H. stenognathus was not a hard-object feeder has bearing on the interpretation of hominin cranial architecture; the features shared by H. stenognathus and robust australopiths do not necessarily reflect adaptations for hard-object processing.

Talar morphology of azibiids, strepsirhine-related primates from the Eocene of Algeria: phylogenetic affinities and locomotor adaptation.

The HGL-50 locality, situated on the Glib Zegdou outlier in the Gour Lazib of Algeria (Hammada du Dra), is famous for having yielded several dental remains of primates dating from the late Early to the early Middle Eocene. These primates include Algeripithecus minutus, Azibius trerki and a new species of cf. Azibius (not described yet). Algeripithecus was widely acknowledged to be one of the oldest known anthropoids from Africa. However, very recent discoveries strongly suggest that Algeripithecus is closely related to Azibius and that both taxa are phylogenetically remote from the clade Anthropoidea. Algeripithecus and Azibius make up the family Azibiidae and appear as stem strepsirhines. Here we describe and analyse two ankle bones (tali) found in HGL-50. UM/HGL50-466 is a small left talus, which is appropriate in size to belong to A. trerki, while UM/HGL50-467 is a right talus, which is significantly larger and appropriate in size to belong to the new large species of cf. Azibius. Both tali exhibit a suite of features that resemble conditions primarily found in extinct and extant strepsirhine and adapiform primates; conditions that are consistent with the strepsirhine-like dentition characterizing azibiids. Functionally, these two tali indicate that Azibius species were engaged in a form of active arboreal quadrupedalism with some ability to climb and leap. Azibiids were rather small-bodied primates, approximating the size of some modern dwarf lemurs (Cheirogaleidae) and sportive lemurs (Lepilemuridae) from Madagascar. Given their small body-size and their talar morphology, living cheirogaleid lemurs, which are agile arboreal quadrupeds (with climbing, springing and branch running activities), might appear as good analogues for azibiids in terms of locomotor behaviour.

Comparing Dirichlet normal surface energy of tooth crowns, a new technique of molar shape quantification for dietary inference, with previous methods in isolation and in combination.

Inferred dietary preference is a major component of paleoecologies of extinct primates. Molar occlusal shape correlates with diet in living mammals, so teeth are a potentially useful structure from which to reconstruct diet in extinct taxa. We assess the efficacy of Dirichlet normal energy (DNE) calculated for molar tooth surfaces for reflecting diet. We evaluate DNE, which uses changes in normal vectors to characterize curvature, by directly comparing this metric to metrics previously used in dietary inference. We also test whether combining methods improves diet reconstructions. The study sample consisted of 146 lower (mandibular) second molars belonging to 24 euarchontan taxa. Five shape quantification metrics were calculated on each molar: DNE, shearing quotient, shearing ratio, relief index, and orientation patch count rotated (OPCR). Statistical analyses were completed for each variable to assess effects of taxon and diet. Discriminant function analysis was used to assess ability of combinations of variables to predict diet. Values differ significantly by diets for all variables, although shearing ratios and OPCR do not distinguish statistically between insectivores and folivores or omnivores and frugivores. Combined analyses were much more effective at predicting diet than any metric alone. Alone, relief index and DNE were most effective at predicting diet. OPCR was the least effective alone but is still valuable as the only quantitative measure of surface complexity. Of all methods considered, DNE was the least methodologically sensitive, and its effectiveness suggests it will be a valuable tool for dietary reconstruction.

Changes in orientation of attritional wear facets with implications for jaw motion in a mixed longitudinal sample of Propithecus edwardsi from Ranomafana National Park, Madagascar.

In many mammalian species, the progressive wearing down of the teeth that occurs over an individual's lifetime has the potential to change dental function, jaw movements, or even feeding habits. The orientation of phase-I wear facets on molars reveals the direction of jaw movement during the power stroke of mastication. We investigated if and how molar wear facets change with increasing wear and/or age by examining a mixed longitudinal dataset of mandibular tooth molds from wild Propithecus edwardsi (N = 32 individuals, 86 samples). Measurements of the verticality of wear facets were obtained from three-dimensional digital models generated from µCT scans. Results show that verticality decreases over the lifetime of P. edwardsi, a change that implies an increasingly lateral translation of the jaw as the teeth move into occlusion. A more transverse phase-I power stroke supports the hypothesis that these animals chew to maximize longevity and functionality of their teeth, minimizing the "waste" of enamel, while maintaining sharp shearing crests. Results of this study indicate that wear facet verticality is more closely correlated with age than overall amount of tooth wear, measured as area of exposed dentin, suggesting that age-related changes in cranial morphology may be more responsible for adjustments in jaw motion over the lifetimes of Propithecus than wear-related changes inthe shape of occluding teeth. Finally, the rate of decrease in wear facet verticality with age is greater in males than in females suggesting differences in development and/or access to resources between the sexes in this species.

Morphometrics and pattern of growth in wild sifakas (Propithecus edwardsi) at Ranomafana National Park, Madagascar.

We summarize morphometric data collected over a period of 22 years from a natural population of rainforest sifakas (Propithecus edwardsi) at Ranomafana National Park, Madagascar, and we use those data to document patterns of growth and development. Individually identified, known-age sifakas were successfully captured, measured, and released. We found that body segment lengths increased faster during growth than did body mass, with individuals attaining adult lengths earlier than adult mass. Females can begin reproducing before they are fully grown, but this may not be common. With the exception of hand length, we found no significant sex difference in any adult metric including body mass, chest, and limb circumferences, body segment lengths, and canine tooth height; however, body masses of individual females fluctuated more, independently of pregnancy, than did those of males. We found considerable interannual fluctuation in body mass with single individuals differing more within the same season in different years than from season to season in the same year. Such body mass fluctuation may be a consequence of eastern Madagascar's variable and unpredictable environment in which rainfall during any selected month varies from year to year.

A reconstruction of the Vienna skull of Hadropithecus stenognathus.

Franz Sikora found the first specimen and type of the recently extinct Hadropithecus stenognathus in Madagascar in 1899 and sent it to Ludwig Lorenz von Liburnau of the Austrian Imperial Academy of Sciences. Later, he sent several more specimens including a subadult skull that was described by Lorenz von Liburnau in 1902. In 2003, some of us excavated at the locality and found more specimens belonging to this species, including much of a subadult skeleton. Two frontal fragments were found, and these, together with most of the postcranial bones, belong to the skull. CT scans of the skull and other jaw fragments were made in Vienna and those of the frontal fragments at Penn State University. The two fragments have been reunited with the skull in silico, and broken parts from one side of the skull have been replaced virtually by mirror-imaged complete parts from the other side. The parts of the jaw of another individual of a slightly younger dental age have also been reconstructed virtually from CT scans with mirror imaging and by using the maxillary teeth and temporomandibular joints as a guide to finish the reconstruction. Apart from forming a virtual skull for biomechanical and systematic analysis, we were also able to make a virtual endocast. Missing anterior pieces were reconstructed by using part of an endocast of the related Archaeolemur majori. The volume is 115 ml. Hadropithecus and Archaeolemur seem to have had relatively large brains compared with the other large-bodied subfossil lemurs.

"Life history space": a multivariate analysis of life history variation in extant and extinct Malagasy lemurs.

Studies of primate life history variation are constrained by the fact that all large-bodied extant primates are haplorhines. However, large-bodied strepsirrhines recently existed. If we can extract life history information from their skeletons, these species can contribute to our understanding of primate life history variation. This is particularly important in light of new critiques of the classic "fast-slow continuum" as a descriptor of variation in life history profiles across mammals in general. We use established dental histological methods to estimate gestation length and age at weaning for five extinct lemur species. On the basis of these estimates, we reconstruct minimum interbirth intervals and maximum reproductive rates. We utilize principal components analysis to create a multivariate "life history space" that captures the relationships among reproductive parameters and brain and body size in extinct and extant lemurs. Our data show that, whereas large-bodied extinct lemurs can be described as "slow" in some fashion, they also varied greatly in their life history profiles. Those with relatively large brains also weaned their offspring late and had long interbirth intervals. These were not the largest of extinct lemurs. Thus, we distinguish size-related life history variation from variation that linked more strongly to ecological factors. Because all lemur species larger than 10 kg, regardless of life history profile, succumbed to extinction after humans arrived in Madagascar, we argue that large body size increased the probability of extinction independently of reproductive rate. We also provide some evidence that, among lemurs, brain size predicts reproductive rate better than body size.