The Anatomical Record

The aim of this study was to explore and compare patterns of morphological covariation, including symmetrical deviations, between splanchnocranium and the basicranium in Toy rabbit, a type of paedomorphic rabbit. A sample of 32 skulls of adult Toy rabbits was studied on digital pictures on ventral aspects by means of geometric morphometric methods. A set of 7 landmarks were located on the horizontal plane of the splanchnocranial ventral bones (palatine process of the maxillary bone [processus palatinus maxillae] + palatine bone [lamina horizontalis ossis palatini]), and a set of 8 landmarks were on the basicranium (sphenoid [os sphenoidale] + basilar part of the occipital bone [pars basilaris] + bulla tympanica). Both fluctuating and directional asymmetries were detected on both blocks, being the asymmetry more important among splanchnocranial bones. It appeared also a significant relationship (allometry) between size and shape, especially in the basicranium, as well a significant relationship between the two blocks. From results we deduce that, although normally cranial base usually reaches adult size before the face, in paedomorphic animals the face stops its growth earlier than basicranium, resulting in their proportionally reduced splanchnocranium, the typical brachyfacial morphology for paedomorphy. In other words, our results support the hypothesis of an early stop of facial pattern development in neoteny -the retention of juvenile characteristics into adulthood-, which can affect vital structures. So, further research should expand on clinical data of paedomorphic animals in order to advance in the understanding of pathological results of this growth anomaly.

During dissecting skulls of green frogs of the genus Pelophylax it has found that the description of a number bones and cartilaginous structures requires addition and clarification. In addition, previously undescribed details of anatomical structure of the skull of green frogs has revealed. The traits of anatomical structure of skull of green frogs, characteristic for ancestral forms of Anura found too.

The supracondylar foramen with a seemingly osseous peripheral arch noticed on the medio-distal feline humeri had remained disputed among anatomists. Some scholars have argued in favor of homology between this foramen and the supracondyloid foramen formed in the presence of the ligament of Struthers in humans. Other theories include its presence as a retinaculum holding the median nerve and brachial artery to their anatomical position in a flexed elbow. Unfortunately, these theories lack investigative rigor. The emergence of non-invasive imaging modalities, such as micro-computed tomography, has enabled researchers to inspect the internal anatomy of bones without dismantling. Thus, a micro-computed tomographic investigation was conducted on three feline humeri specimens while the internal anatomy of the supracondylar foramina was examined. Unlike the humerus, the thin peripheral arch of the feline supracondylar foramen failed to elicit any osseous trabeculae or foci of calcification. While adhering to the humeral periosteum at its origin, the non-osseous arch, typical of a muscular tendon or a ligament, inserts into a bony spur attached to the medial humeral epicondyle suggestive of a ligament or aponeurotic extension of a (vestigial) brachial muscle, with the coracobrachialis longus emerging to be the most likely candidate.

Marsupials are born with structurally immature lungs when compared to eutherian mammals. The Gray short-tailed opossum (Monodelphis domestica) is born at the late canalicular stage of lung development. Despite the high degree of immaturity, the lung is functioning as respiratory organ, however supported by the skin for gas exchange during the first postnatal days. Consequently, the majority of lung development takes place in ventilated functioning state during the postnatal period. X-ray computed tomography ({micro}CT) was used to three-dimensionally reconstruct the terminal airspaces in order to reveal the timeline of lung morphogenesis. In addition, lung and air space volume as well as surface area were determined to assess the functional relevance of the structural changes in the developing lung. The development of the terminal air spaces was examined in 35 animals from embryonic day 13, during the postnatal period (neonate to 57 days) and in adults. At birth, the lung of M. domestica consists of few large terminal air spaces, which are poorly subdivided and open directly from short lobar bronchioles. During the first postnatal week the number of smaller terminal air spaces increases and numerous septal ridges indicate a process of subdivision, attaining the saccular stage by 7 days. The 3 D reconstructions of the terminal air spaces demonstrated massive increases in air sac number and architectural complexity during the postnatal period. Between 28 and 35 days alveolarization started. Respiratory bronchioles, alveolar ducts and a typical acinus developed. With alveolarization the volume of the air spaces and the surface area for gas exchange increased markedly. The structural transformation from large terminal sacs to the final alveolar lung in the Gray short-tailed opossum follows similar patterns as described in other marsupial and placental mammals. The processes involved in sacculation and alveolarization during lung development seem to be highly conservative within mammalian evolution.

This study aims to discriminate cercopithecid taxa of higher taxonomic levels (subfamily, tribe, subtribe, and genus) on the basis of corpus shape in transverse cross-section at the M1-M2 junction and to assess its variation using 2D geometric morphometrics. Specifically, we evaluated the effect of allometry and sexual dimorphism on differences in corpus shape at interspecific and intraspecific levels, respectively. We also investigated whether corpus variation among cercopithecids was following Brownian motion using Pagels {lambda}. Taxonomic discrimination and sexual dimorphism were established using Analysis of Variance on Principal Component scores. Allometry was studied using phylogenetic least-squares regressions and partial least-squares regressions. We demonstrated that, using corpus shape, extant cercopithecids can be significantly discriminated at the subfamilial, tribal, and subtribal levels. In addition, the main axis of variation of the Principal Component Analysis follows a distribution expected under Brownian motion, validating the presence of a phylogenetic signal in corpus shape. Colobines exhibit a robust corpus (superoinferiorly short and transversely broad) with large lateral prominences while cercopithecines have a gracile corpus (superoinferiorly long and transversely thin in its distal portion) with marked corpus fossae in African papionins. Exception to the typical subfamilial or tribal shape pattern exist, with the best examples being Trachypithecus, Presbytis and Pygathrix within colobines, Allenopithecus within Cercopithecini, and Macaca, Theropithecus and Cercocebus within Papionini. Sexual dimorphism is a confounding factor in shape discrimination, as there are significant differences between sexes, notably in Papio anubis, Nasalis larvatus and Procolobus verus . Intriguingly, sexual dimorphism in corpus shape does not seem to follow the dimorphism deduced in canine and molar crown dimensions. This discrepancy is illustrated by the low degree of dimorphism in corpus shape in Piliocolobus badius, despite dimorphic canine and molar dimensions. Overall, our findings concerning corpus shape variation in cercopithecids will greatly benefit to paleontological studies that seek to identify taxa in the fossil record, and to neontological studies aiming to explore the ecomorphological value of the cercopithecid mandible.

In veterinary medicine, canine Chiari-like malformation (CLM) disease is surgically managed through foramen magnum decompression (FMD) with cranioplasty. This study aimed to assess the efficacy of cranioplasty surgery by establishing a rat CLM model and then applying FMD with and without cranioplasty and comparing the outcomes. Twenty-four 8-week-old male Sprague-Dawley rats underwent surgery to induce CLM by reducing the caudal cranial fossa volume, mimicking cerebellum herniation. The rats were randomly and equally assigned to three groups: a control group (induced CLM), an FO group (induced CLM rats undergoing FMD only), and a CR group (induced CLM rats undergoing FMD with cranioplasty). At 11 weeks of age, the FO and CR groups underwent FMD surgery. Four weeks later, magnetic resonance imaging (MRI) was used to measure the cisterna magna volume to assess surgical outcomes. Post-surgery MRI revealed that the mean cisterna magna volume was 23.82 {+/-} 1.70, 34.88 {+/-} 4.39, and 29.48 {+/-} 2.20 mm3 in the control, FO, and CR groups, respectively. There was a significant increase in the cisterna magna volume in the FO and CR groups compared to that in the control group (p < 0.05), with the FO group showing a significantly greater increase than the CR group (p < 0.05). These findings suggest that FMD surgery alone is more effective at restoring the cisterna magna volume than FMD surgery with cranioplasty. FMD surgery alone resulted in a greater increase in cisterna magna volume than FMD with cranioplasty in our rat CLM model, suggesting that FMD alone may be more effective to treat canine CLM. These findings challenge the typical approach of combining FMD with cranioplasty in treating canine CLM disease and underscore the need for further investigation into optimizing surgical techniques for CLM.

The scaling pattern of the forelimb in Carnivora was determined using a sample of 30 variables measured on the scapula, humerus, radius, ulna, and third metacarpal, of 429 specimens belonging to 137 species of Carnivora. Standardized major axis regressions on body mass were calculated for all variables, using both traditional regression methods and phylogenetically independent contrasts (PIC). In agreement with previous studies on the scaling of the appendicular skeleton, conformity to either the geometric similarity hypothesis or the elastic similarity hypothesis was low. The scaling pattern of several phyletic lines and locomotor types within Carnivora was also determined, and significant deviations from the scaling pattern of the order were found in some of these subsamples. Furthermore, significant evidence for differential scaling was found for several variables, both in the whole sample and in various phylogenetic and locomotor subsamples. Contrary to previous studies, significant differences were found between the allometric exponents obtained with traditional and PIC regression methods, emphasizing the need to take into account phylogenetic relatedness in scaling studies. In light of these and previous results, we conclude that similarity hypotheses are too simplistic to describe scaling patterns in the carnivoran appendicular skeleton, and thus we propose that scaling hypotheses should be built from similarities in the scaling patterns of phylogenetically narrow samples of species with similar locomotor requirements. The present work is a first step in the study of those samples.

As biological shape is usually complex and evolves on different constraints, it can be assessed using integrative methods such as geometric morphometrics. Allometric changes were analysed in three species of Didelphis genus (D. albiventris n=20, D. marsupialis n=82, D. pernigra n=35) by means of geometric morphometric techniques. A significant correlation between shape and size was found, suggesting an allometric change pattern for all three species studied. However, allometries appeared to be different between D. marsupialis and D. pernigra, both of which belong to different groups (the so-called black-eared group and the white-eared group, respectively). Results are consistent with taxonomic recognition at the group level and can help to elucidate phylogenetic relationships between these three Didelphis species.

The group Tapejaridae forms a clade of toothless pterosaurs easily recognized by their premaxillary sagittal crests and particularly large nasoantorbital fenestrae. The tapejarids represent the most representative group of pterosaurs from the Lower Cretaceous Crato Formation of the Araripe Basin (Northeastern Brazil). The holotype of the large tapejarid Tupandactylus imperator Campos and Kellner, 1997 is known by two main slabs from the New Olinda Member of the Crato Formation, however, only one of the slabs containing the sagittally bipartite skull is referred to the holotype of Tupandactylus imperator, remain the counter-slab be properly described. The cotype is fragmented in several broken pieces and presents a significative number of cranial elements. A medial internasal septum completely preserved inside the nasoantorbital fenestra is reported for the first time for pterosaurs. The exceptional preservation of a collagenous septum and other integumentary structures visible in the cotype specimen is extremely rare and supports the concept of the unusual pattern of soft tissue observed in the fossils from the Crato Konservat-Lagerstätte, specially pterosaurs. Herein is presented the description of the cotype of Tupandactylus imperator, in complementation to the previously designated slab of the holotype of this tapejarid species. The occurrence of casques in pterosaurs is supported by comparative anatomy with the bird galliform Pauxi (Cracidae). Besides that, it is discussed on the skull with extravagant cranial crests of Tupandactylus imperator and the significance of the associated soft tissues and other cranial integuments, which indicates an expressive morphological and taxonomic diversity among the tapejarid pterosaurs.View Full Text

Quantitative analyses of morphological variation using geometric morphometrics are often performed on 2D photos of 3D structures. It is generally assumed that the error due to the flattening of the third dimension is negligible. However, despite hundreds of 2D studies, few have actually tested this assumption and none has done it on large animals, such as those typically classified as megafauna. We explore this issue in living equids, focusing on ventral cranial variation at both micro- and macro-evolutionary levels. By comparing 2D and 3D data, we found that size is well approximated, whereas shape is more strongly impacted by 2D inaccuracies, as it is especially evident in intra-specific analyses. The 2D approximation improves when shape differences are larger, as in macroevolution, but even at this level precise inter-individual similarity relationships are altered. Despite this, main patterns of sex, species and allometric variation in 2D were the same as in 3D, thus suggesting that 2D may be a source of noise that does not mask the main signal in the data. However, the problem is complex and any generalization premature. Morphometricians should therefore test the appropriateness of 2D using preliminary investigations in relation to the specific study questions in their own samples. We discuss whether this might be feasible using a reduced landmark configuration and smaller samples, which would save time and money. In an exploratory analysis, we found that in equids results seem robust to sampling, but become less precise and, with fewer landmarks, may slightly overestimate 2D inaccuracies.

In modern humans, facial soft tissue thicknesses have been shown to covary with craniometric dimensions. However, to date it has not been confirmed whether these relationships are shared with non-human apes. In this study, we analyze these relationships in chimpanzees (Pan troglodytes) with the aim of producing regression models for approximating facial soft tissue thicknesses in Plio-Pleistocene hominid individuals. Using CT scans of 19 subjects, 637 soft tissue, and 349 craniometric measurements, statistically significant multiple regression models were established for 26 points on the face and head. Examination of regression model validity resulted in minimal differences between observed and predicted soft tissue thickness values. Assessment of interspecies compatibility using a bonobo (Pan paniscus) and modern human (Homo sapiens) subject resulted in minimal differences for the bonobo but large differences for the modern human. These results clearly show that (1) soft tissue thicknesses covary with craniometric dimensions in P. troglodytes, (2) confirms that such covariation is uniformly present in both extant Homo and Pan species, and (3) suggests that chimp-derived regression models have interspecies compatibility with hominids who have similar craniometric dimensions to P. troglodytes. As the craniometric dimensions of early hominids, such as South African australopithecines, are more similar to P. troglodytes than those of H. sapiens, chimpanzee-derived regression models may be used for approximating their craniofacial anatomy. It is hoped that the results of the present study and the reference dataset for facial soft tissue thicknesses of chimpanzees it provides will encourage further research into this topic.

Sciurus vulgaris Linnaeus, 1758, the red squirrel, is a small, mostly arboreally living rodent, spread across the Palearctic. It is mostly vegetarian, feeding on plants, fungi and seeds, and is less active in the winter months, but does not hibernate. In this lateral study, the humeri of the subspecies Sciurus vulgaris fuscoater, the Central European red squirrel, were analysed to uncover potential intraspecific variation between individuals found in different seasons. The {micro}CT-scans were obtained with a resolution of 26 microns. Five bone parameters were calculated and statistically evaluated with regards to seasonal variations: total volume, bone volume, endocortical surface, cortical thickness, and average trabecular thickness. Bone volume, trabecular thickness and endocortical thickness correlate with bone size, whereas cortical thickness does not. Seasonal differences were observed between the warmer summer and autumn months versus the colder winter and spring months for all parameters. We, speculatively, relate the observed seasonal variation to nutrient intake, notably calcium. These results offer a deeper understanding of intraindividual variation in red squirrels, that may be useful in further ecological, taxonomic, and paleontological research.

The Eurasian lynx (Lynx lynx) was historically native to the Iberian Peninsula, as evidenced by scarce paleontological records and sightings across northern Spain, dating from the Last Glacial Maximum until the 17th century. A novel and nearly complete skeleton of a medium-sized felid, morphologically identified as L. lynx, was recently recovered from Sima Topinoria in Picos de Europa (Cantabria, Spain). The present study aims to recover and analyze the full skeletal assemblage, establishing its chronological framework, taxonomic identification, and comparative craniometry with other ancient and modern Eurasian lynxes. Radiocarbon dating estimates the specimen around 210 years BP, representing the most recent confirmed occurrence of Eurasian lynx in the Iberian Peninsula. This evidence revises the accepted timeline for the species extirpation in the region, indicating its persistence into the early 19th century, connecting physical evidence with historical and traditional narratives. Morphometric analysis identifies the individual as an adult male with an estimated body mass of 19.7 kg. Comparative osteometric analyses revealed that the specimen from Sima Topinoria falls within the average size for modern males from the Carpathian population, while being significantly smaller than older Holocene males from the Iberian Peninsula ([~]2570 yBP), suggesting a possible trend toward a protohistoric body size reduction in the Holocene, akin to patterns reported for other mammalian fauna from the Cantabrian Mountains. These results redefine the Eurasian lynx s historical range collapse in southwestern Europe, suggesting that the species survived until recent times, coinciding with periods of intense anthropogenic landscape change. The study highlights the critical role of paleontological data in refining extinction chronologies and contributes valuable insights into the biogeographic history of this elusive feline in western Europe.

The detection of chemical signals by the vomeronasal organ (VNO) is critical for communication among mammals from an early age, influencing behaviors such as suckling and recognition of the mother and conspecifics. Located in a concealed position at the base of the nasal cavity, the VNO features a duct covered with a sensory epithelium rich in neuroreceptors. A critical aspect of VNO functionality is the efficient access of stimuli from the nasal and oral cavities to the receptors. In adult dogs, it has been demonstrated through in vivo magnetic resonance imaging and anatomically postmortem how the VNO duct (VD) communicates to the environment through the incisive duct (ID). However, in newborn puppies, the existence of functional communication between the ID and the VD has not been confirmed to date, raising doubts about the potential physiological obliteration of the ID due to its small size and the degree of immaturity of the puppies at birth. Determining this aspect is necessary to evaluate the role played by chemical communication in this critical phase for the survival and socialization of puppies. This study employs serial histological staining techniques to examine the presence and functionality of the incisive duct in neonatal dogs. The serial histological sections have confirmed both the existence of functional communication between both the vomeronasal and incisive ducts in perinatal puppies, and the dual functional communication of the incisive duct with the oral and nasal cavities. The ID shows an uninterrupted lumen along its path and is associated with a sophisticated cartilaginous complex that prevents its collapse, as well as erectile tissue rich in blood vessels and connective tissue that acts as a cushion, facilitating its action under pressure induced by sampling behaviors such as tonguing. This investigation demonstrates the communicative capabilities of the VNO during the perinatal stage in dogs.

In birds, the quadrate bone serves as a hinge articulating with the lower jaw and the skull, playing an important mechanical role in the feeding apparatus. Avian cranial kinesis is dependent on the streptostylic quadrate transferring force from the adductor muscles at the back of the skull toward the beak, as part of a four-bar mechanical linkage to elevate and depress the bill. The complex morphology of the bird quadrate has led to authors adopting a range of alternative terminologies to describe the same anatomical structures and character states, impeding clarity of communication and presenting a barrier to progress in our understanding of the evolution of this important component of the avian feeding apparatus. Here, we reconcile terminological discord among previous studies on avian quadrate morphology and propose a stable nomenclature for future work. To characterise the considerable variation in quadrate form across crown bird diversity, we present an extensive anatomical atlas of the avian quadrate and summarise major patterns of quadrate morphological variation across extant avian phylogeny. In addition, we investigate macroevolutionary patterns in avian quadrate morphology, incorporating comparisons of crown birds and Late Cretaceous near-crown stem birds. We demonstrate that quadrate characters are useful for diagnosing a range of major avian subclades, and suggest that numerous distinctive features are likely to be associated with important biomechanical consequences. This investigation has implications for resolving the unsettled phylogenetic relationships of extinct bird clades such as Pelagornithidae and Gastornithiformes, as well as controversial relationships within several extant groups.

Morphological integration and modularity are concepts that refer to the covariation level between the components of a structure. Species of the opossums, genus Didelphis, have been the object of several taxonomic and morphometric analyses but no study has so far analysed mandibular morphological integration and modularity at a species-level. The aim of this work was to check whether the body (corpus mandibulae, mandibular corpus) and the ramus (ramus mandibulae, ascending mandibular ramus) are separate modules in Didelphis pernigra using a two-dimensional geometric morphometric approach. For this purpose, a sample of hemimandibles from 36 D. pernigra (13 males and 23 females) was analysed using 17 landmarks in lateral view. The modularity hypothesis based on different developmental origins was tested, by using the RV coefficient. Later, the integration level was assessed applying a partial least-squares analysis (PLS). The underlying aim was to know whether the traditional division between mandibular body and ramus has a modular basis, as well as the morphological integration level between these two structures. Results reflected that landmarks integration was not uniform throughout the mandible but structured into two distinct modules: ramus and body. Results allow to conclude that allometry plays an important role in shape variation in this species, and that the hypotheses of two-module organization in males cannot be confirmed. Models that accurately represent the biting mechanics will strengthen our understanding of which variables are functionally relevant and how they are relevant to performances, not only masticatories.

In the course of performing a detailed dissection of adult rat to map the cutaneous nerves of cervical, thoracic, and lumbar levels a small and unexpected structure was isolated. It appeared to be a cutaneous striated muscle and was observed in both male and female rats and in mice but absent from cats and humans. With the skin reflected laterally from midline, the muscle lies closely apposed to the lateral border of the Thoracic Trapezius (Spinotrapezius) muscle and is easily missed in standard gross dissections. Focussed prosections were performed to identify the origin, insertion, and course of gross innervation. Identification of each of these elements showed them to be distinct from the nearby Trapezius and Cutaneous Trunci (Cutaneous Maximus in mouse) muscles. The striated muscle nature of the structure was validated with whole-mount microscopy.Consulting a range of published rodent anatomical atlases and gross anatomical experts revealed no prior descriptions. This preliminary report is an opportunity for the anatomical and research communities to provide input to either confirm the novelty of this muscle or refer to prior published descriptions in rodents or other species while the muscle, its innervation, and function are further characterized. Presuming this muscle is indeed novel, the name "Cutaneous Scapularis muscle" is proposed in accord with general principles of the anatomical field.

In the cerebellum of juvenile Oncorhynchus masou, proliferating BrdU+ and HuCD+ cells and constitutive neurogenic niches were detected in different zones; the largest number of labeled cells were found in the dorsal part of the molecular layer and the dorsal matrix zone (DMZ). Cells labeled with glutamine synthetase (GS) and radial glia were also present in the intact O. masou cerebellum. The most intensive proliferation was detected in the rostral part of cerebellum. This part is assumed to contain active zones of constitutive neurogenesis. After an injury inflicted to the cerebellum, the number of BrdU+ and HuCD+ cells increased significantly. The number of BrdU+ cells after this type of injury was much greater than after a telencephalon trauma. A quantitative analysis revealed that after the cerebellum injury the proliferative activity in the caudal part of CCb is increased compared to that in the control. A reactivation of neurogenic and neuroepithelial niches and their transformation into reactive neurogenic domains, with an increased distribution density of intensely labeled HuCD+ cells of different types, were observed. The increase in the number of HuCD+ differentiated cells in the basal area suggests that the processes of neuronal differentiation are intensified in the cerebellum of juvenile O. masou after injury. The number of GS positive cells (GS+) and fibers increased in all the zones of cerebellum. The most intensive astrocytic response was noted in the dorsal part of cerebellum. The data of the enzyme immunoassay confirm the multiple variations in the level of GS after a traumatic injury to cerebellum in O. masou.

Marsupials (Marsupialia, Mammalia) represent a clade with highly varied ecologies. This is particularly true for opossums (South American marsupials), which are difficult to observe and collect. Consequently, few studies have focused on their bite force and the muscles of their masticatory apparatus, and there exists only scant information about the diet of certain species. Here we describe the masticatory muscles of several previously unstudied opossum species including Caenolestes fuliginosus, Dromiciops gliroides, and Monodelphis touan. We calculate the bite force of these species using data from both manual and virtual dissections and compare their theoretical bite forces with literature data. Additionally, we explore the differences between manual and virtual dissection to determine muscle PCSA (Physiological Cross-Sectional Area). We tried two virtual methods (VPDE: "virtual physiological data estimating method" and SM: "slicing muscle method") to calculate the PCSA, determine the differences induced by the inter-fiber void in the virtual volume, and calculate a correction post-treatment with the contrast agent. The results highlighted variation in the position of the muscular attachments of the M. zygomaticomandibularis, whose insertion area is the largest in Monodelphis touan and the smallest in Caenolestes fuliginosus. The bite forces are coherent with estimates from the literature suggesting that the biomechanical model is reliable. The comparison between manual and virtual dissection showed that while virtual dissection allows an overall description of the masticatory muscles, it is more complex to accurately describe the different subdivisions of the muscle bundles. Virtual dissection data could potentially complete manual dissection data with the association of the VPDE method, the exclusion of inter-fiber voids, and a correction for the treatment with contrast-agents.

The symphyseal anatomy of extant and fossil cercopithecids has not yet been demonstrated as a useful tool for taxonomic discrimination, and the source of variation in cercopithecid symphysis has not been addressed on a broad taxonomic scale. Here, we used linear and angular dimensions to quantify symphysis shape. Using univariate, multivariate data and allometric regressions (partial least squares and phylogenetic generalized least square regressions), we addressed the hypothesis that extant cercopithecids can be distinguished by symphysis shape. Significant differences in univariate and multivariate data and allometric regressions permitted to distinguish cercopithecids at the subfamilial, tribal, and genus levels. We showed that multivariate data followed the distribution expected under Brownian Motion and significantly discriminates taxa at different taxonomic levels. Colobine symphysis are characterized by developed inferior transverse tori, short planum alveolare, and short symphysis, whereas cercopithecine symphysis are characterized by developed superior transverse tori, long planum alveolare, and long symphysis. Exceptions to this pattern exist within each subfamily, and this study underlines the particular anatomy of Colobus and Presbytis among the colobines, Allenopithecus among the Cercopithecini, and Theropithecus and Lophocebus among the Papionini. We also demonstrate that the relative development of the transverse tori, the relative length of the planum alveolare and symphyseal inclination are dimorphic traits. Specifically, we show that the symphysis of Procolobus verus, Nasalis larvatus, and Papio anubis is strongly dimorphic.