Variation In Skull Morphology Research Articles

Patterns of morphological variation and ecological correlates in the skull of vipers (Serpentes: Viperidae).

The skull of vipers is a highly kinetic anatomical structure involved in envenomating and consuming of prey. Morphological knowledge about the viperid skull is based on studies on some groups of species, but information on its variation within the whole family and its functional morphology is still scarce. In this study, we aimed to explore variation in skull morphology among species of the three subfamilies of Viperidae, and test whether that variation correlates with macrohabitat and diet. We performed quantitative analyses of the viperid skull based on broad taxonomic sampling and two methodological approaches: linear and geometric morphometrics. The results of both approaches showed that much of the variation lies in differences of shape and relative size of the premaxilla, the nasals, the frontals, and the parietals. The results indicated that phylogeny and size influence the shape of the skull, but we also found evidence of morphological differentiation between arboreal and terrestrial species and in species with mammal specialist diet. Our findings imply that, besides evolutionary allometry and phylogenetic signal, demands of particular diets coupled with use of certain habitats have in part shaped morphological evolution of the viperid skull.

Morphological and Morphometric Relations of Infraorbital Foramen in North Indian Population.

Introduction The evidence regarding the anatomy of the infraorbital foramen in the Indian population is limited. It mainly focuses on its shape, size, and incidence in the Indian population. The current study aimed to evaluate morphometric parameters of infraorbital foramen that can help clinicians during surgery and procedures around it. Methods We evaluated 90 dry adult humanhemi-skulls. The morphological parameters studied included the assessment of the shape of the infraorbital foramen, its horizontal and vertical diameters, and its relation to the teeth of the upper jaw. In addition, we measured the distance of the infraorbital foramen from the anterior nasal spine, nasion, infraorbital margin, and the lower extent of the alveolar margin. The lengthof the infraorbital canal till the inferior orbital fissure and the infraorbital groove and the infraorbital canal orientation angles in different planes were also measured. The measurement values were compared between the right and left side hemi-skulls. Results The oval-shaped infraorbital foramen was most commonly noticed. The mean vertical and transverse diameters were 3.8 mm and 2.6 mm, respectively, on the right side. The left side's mean vertical and transverse diameters were 3.9 mm and 2.5 mm, respectively. The most common location of infraorbital foramen was in line with the maxillary second premolar tooth. The distances of infraorbital foramen from the alveolar margin were 29.6 mm and 29 mm on the right and left sides, respectively. The distances of the infraorbital foramen from the anterior nasal spine were 34.3 mm and 34.2 mm on the right and left sides, respectively. The distances of infraorbital foramen from the nasion were 42.3 mm and 42.2 mm on the right and left sides, respectively. The distances of infraorbital foramen from the inferior orbital margin were 5.8 mm and 6.2 mm on the right and left sides, respectively. The distances between the inferior orbital margin and infraorbital groove were 12.7 mm and 12.7 mm on the right and left sides, respectively. The distances between the inferior orbital margin and inferior orbital fissure were 27.5 mm and 27.1 mm on the right and left sides, respectively. The orientation angles of infraorbital foramen were 48.31° in the horizontal plane, 34.07° in the Frankfurt plane, and 14.4° in the parasagittal plane. Conclusion Our findings suggest that the location of the infraorbital foramen is difficult to standardize, considering the wide interindividual variations in the foramen relations.Further research should be performed to investigate the parameters related to the distance and orientation of the infraorbital foramen in relation to nearby bony landmarks that are least affected by individual variations in skull morphology.

Estimating age of wild eastern grey kangaroos through molar progression

Age is an essential attribute in studies of animal development, survival and reproduction. Here we evaluate the age estimation technique of molar progression devised for kangaroos in 1965. We used 71 wild eastern grey kangaroos (Macropus giganteus) that were first captured and aged as pouch young at Wilsons Promontory National Park, Victoria, and subsequently found dead between the ages of 1 and 14 years. We expected that the original equation, derived from captive kangaroos in Queensland, would not estimate age correctly due to differences in diet and/or clinal variation in skull morphology. We found no difference in rate of molar progression between males (n = 44) and females (n = 27). Our overall regression of age on molar index (MI) was log10 (age, days) = 0.284 (MI) + 2.511, r2 = 0.97. The slope of this equation was indistinguishable from that of the original one, meaning that molar progression in the wild was equivalent to that originally developed on captive kangaroos, despite likely differences in diet and morphology.

Skull variation in populations of the Indian gerbil Tatera indica (Gerbillinae, Rodentia) sampled across its broad geographic range

Populations of broadly distributed species often exhibit geographic structuring, which is sometimes reflected in phenotype. The monotypic Indian gerbil (Tatera indica) is an example of a widely distributed species, with its range encompassing much of Asia. This study aims to determine if T. indica populations exhibit marked variation in skull morphology—this structure is particularly adaptable and thus could be amenable to show such variation. Furthermore, the potential drivers of skull variation are examined, including the role of climate and geography. To achieve these goals, 21 linear measurements were measured on the skulls of 509 specimens, coming from 111 different localities, across this species wide range. The specimens were then assigned into one of four broad geographic groups (≈ populations) based on their geographic proximity, and the overall and the pairwise differences in the 21 skull measurements among these groups were assessed. Specimens from Pakistan significantly differed from those belonging to the West Iran, East Iran, and India populations, which in turn did not significantly differ from each other. Pairwise bioclimatic and geographic distances between the localities explained a significant, yet small amount of variation in the measurements. Thus, while the Pakistani T. indica population was distinct in skull measurements, both climatic and non-climatic spatial factors seem not to account largely for its distinctiveness (from the other populations).

Multivariate analyses of skull morphology inform the taxonomy and evolution of geomyoid rodents.

Morphological analyses are critical to quantify phenotypic variation, identify taxa, inform phylogenetic relationships, and shed light on evolutionary patterns. This work is particularly important in groups that display great morphological disparity. Such is the case in geomyoid rodents, a group that includes 2 of the most species-rich families of rodents in North America: the Geomyidae (pocket gophers) and the Heteromyidae (kangaroo rats, pocket mice, and their relatives). We assessed variation in skull morphology (including both shape and size) among geomyoids to test the hypothesis that there are statistically significant differences in skull measurements at the family, genus, and species levels. Our sample includes 886 specimens representing all geomyoid genera and 39 species. We used the geometric mean to compare size across taxa. We used 14 measurements of the cranium and lower jaw normalized for size to compare shape among and within taxa. Our results show that skull measurements enable the distinction of geomyoids at the family, genus, and species levels. There is a larger amount of size variation within Geomyidae than within Heteromyidae. Our phylomorphospace analysis shows that the skull shape of the common ancestor of all geomyoids was more similar to the common ancestor of heteromyids than that of geomyids. Geomyid skulls display negative allometry whereas heteromyid skulls display positive allometry. Within heteromyids, dipodomyines, and non-dipodomyines show significantly different allometric patterns. Future analyses including fossils will be necessary to test our evolutionary hypotheses.

A geometric morphometric analysis of geographic variation in the Cape Short-eared gerbil, Desmodillus auricularis (Rodentia: Gerbillinae)

Abstract The genus Desmodillus is monospecific, consisting of only the Cape short-eared gerbil (Desmodillus auricularis). Despite being widely distributed across southern Africa, previous studies did not find evidence of intraspecific phenotypic geographic differentiation. The objectives of this study is to use geometric morphometrics to investigate if and how the skull of D. auricularis varies spatially. It examines the covariation of skull morphology with broad spatial (latitude and longitude) and climatic variables, based on a sample of 580 specimens from southern Africa (Botswana, Namibia, and South Africa). The results did not support the differentiation of D. auricularis populations into distinct geographically isolated phenotypic groups. However, there is strong evidence for clinal variation in skull morphology; the most prominent pattern being a decrease in size from the west (closest to the South Atlantic coast) to the east (towards the continent’s interior). Shape variation was not localized in any skull region and seem to be driven mostly by size (allometry), although it also covaried significantly with latitude and longitude. Statistically significant skull shape sexual dimorphism was also detected, with males having larger crania than females. Spatial clinal variation in skull morphology was mostly associated with differences in the aridity of the habitats relative to their distance from the coast as evidenced by precipitation-related bioclimatic variables—annual precipitation (BIO12), precipitation of driest month (BIO14), and precipitation of driest quarter (BIO17)—covarying the most with skull morphology. This could be driven by either the climate influencing local resources available to populations or by the climate directly instigating phenotypic climatic adaptations.

Assessment of the Possibilities of Forensic Identification Population of Kazakhstan by Craniometric Indicators

BACKGROUND: Craniometric indicators are one of the most reliable sources of information about the population. Despite the development of genetic methods, skull measurements are extremely important in anthropology and forensic medicine. In addition to the history of population development, environmental factors such as climate and lifestyle contribute to variations in human skull shape. Due to the high variability of human individuals, the anthropological study of the population is carried out selectively, with a comparison of different population groups (ethnic, professional, age, gender). The lack of clear ideas about the typical parameters and proportions of the skull among the people of Kazakhstan creates a certain gap in forensic-medical identification.
 AIM: The aim of the work is to check the hypothesis about the relationship between variations in skull morphology and changes in craniometric indicators with climatic conditions and the specifics of lifestyle in populations living in different territories of Kazakhstan.
 METHODS: 187 male and 114 female adult skulls found on the territory of the two largest regions of Kazakhstan were examined. The variable variability of 25 craniometric indicators of skulls found on the territory of Central and South Kazakhstan was studied. All osteometric changes were performed using standard anthropometric instruments, followed by the calculation of craniometric indices. Multidimensional statistics were applied.
 RESULTS: The two populations demonstrate differences in craniometric indicators formed in different geographical and ecological conditions, regardless of gender. It was found that the sizes of the skulls found in the two studied regions of Kazakhstan statistically significantly differ in 5 craniometric indicators for men and 8 craniometric indicators for women. Significant changes were noted in the size of the full and upper height of the face, the average width of the face, the height of the body of the lower jaw and the height of the nose in men. The most dimorphic variables for forensic medical evaluation in the studied populations of female skulls were transverse, altitudinal and zygomatic diameters, mastoid width, width of the base of the skull, width of the occipital foramen, upper face height and nose height. The shape of the skulls found in the studied territories is predominantly brachycephalic. The cranial index was >81.1% - at men, 83% - at women. The study showed that race affects the size of the skull, regardless of gender. Craniometric parameters in male and female skulls vary according to different criteria. In women between races, there are statistically significant differences in the size of the width of the occipital foramen and the average width of the face. Statistically significant differences in the width of the base of the skull, the zygomatic diameter and the average width of the face between the Caucasoid and Mongoloid races were revealed in the studied regions in men. The established differences made it possible to form additional differential diagnostic criteria.
 CONCLUSION: Identification of the features inherent in the population living in certain territories provides auxiliary information for medical and forensic identification of a person. In this study, population-specific craniometric indicators have been developed for inhabitants of two regions of Kazakhstan, which expand and complement identification capabilities when categorizing skeletal remains found in these territories.

Cranial variation in the Altai weaselMustela altaica(Carnivora: Mustelidae) and its possible taxonomic implications

AbstractThe Altai weasel, Mustela altaicaPallas 1811 (Carnivora: Mustelidae), is widely distributed across open landscapes of central and eastern Asia. The geographical variation in skull morphology and taxonomic composition of this small mustelid remain poorly known. Based on extensive sampling in museum collections, we analyzed morphometric variation in 23 cranial characters of 232 M. altaica specimens from across its entire range. The multivariate analysis (nonmetric multidimensional scaling) revealed a geographical pattern of variation in cranial size and shape. Based on this result, two morphological groups have been comprehensively characterized. Weasels of the first group differ from those of the second in having larger skulls, wider neurocrania, elongated toothrows, and larger carnassial teeth, as well as in sexual size dimorphism. The first group is confined to the southwestern part of the species range (Tien Shan Mountains, Pamir, the Himalayas, and southern Tibet). The second group is widespread from the foothills of Tien Shan in the west to Khingan and Manchuria in the east. The distribution of the two groups of M. altaica is consistent with the “Out-of-Tibet” hypothesis. The first group presumably can be attributed to M. a. temonHodgson, 1857, whereas the second group can be treated as nominotypical M. a. altaicaPallas, 1811.

Functional correlates of skull shape in Chiroptera: feeding and echolocation adaptations.

Morphological, functional, and behavioral adaptations of bats are among the most diverse within mammals. A strong association between bat skull morphology and feeding behavior has been suggested previously. However, morphological variation related to other drivers of adaptation, in particular echolocation, remains understudied. We assessed variation in skull morphology with respect to ecology (diet and emission type) and function (bite force, masticatory muscles and echolocation characteristics) using geometric morphometrics and comparative methods. Our study suggests that variation in skull shape of 10 bat families is the result of adaptations to broad dietary categories and sound emission types (oral or nasal). Skull shape correlates with echolocation parameters only in a subsample of insectivorous species, possibly because they (almost) entirely rely on this sensory system for locating and capturing prey. Insectivores emitting low frequencies are characterized by a ventrally tilted rostrum, a trait not associated with feeding parameters. This result questions the validity of a trade-off between feeding and echolocation function. Our study advances understanding of the relationship between skull morphology and specific features of echolocation and suggests that evolutionary constraints due to echolocation may differ between different groups within the Chiroptera.

Interspecific skull variation at a small scale: The genus Eospalax exhibits functional morphological variations related to the exploitation of ecological niche

Ecology influences the process of speciation. The interspecific differences in mammalian skull morphology, induced by environmental factors, are important when investigating speciation. In the Qinghai–Tibetan Plateau, the genus Eospalax consists of six species of subterranean rodents, each with its unique niche, making it an ideal model for studying the relationship between biological evolution and the environment. Here, the interspecific differences in five of the six extant species (E. cansus, E. baileyi, E. rufescens, E. smithii, and E. fontanierii) were evaluated at the morphometric and ecological levels using geometric morphometrics, a powerful tool for studying morphological variation. The multivariate analysis of variance showed significant differences in skull morphology on the dorsal and ventral sides in all species. The thin-plate splines showed that the variations in skull morphology were primarily in the infraorbital foramen, frontal bone, zygomatic arch, occipital bone, incisors, incisive foramen, and tooth row. The multivariate regression analysis showed a significant positive correlation between skull morphological variations and ecological factors; precipitation accounted for the more variations than altitude and temperature. Species inhabiting regions with the highest altitude, minimum precipitation, and temperature (E. baileyi) had the largest infraorbital foramen and zygomatic arch, shortest occipital bone and widest frontal bone, smallest angle formed by two incisors, and longest incisive foramen. Our study elucidates the relationship between skull morphological differentiation and environmental factors in Eospalax, while the biological response to the environment detected warrants further investigation. Our results can provide references for speciation at local environmental scale.

Geometric morphometric analysis of the plateau zokor (Eospalax baileyi) revealed significant effects of environmental factors on skull variations

The plateau zokor (Eospalax baileyi) is employed as an ideal model for examining the relationships between phenotypic and ecological adaptations to the underground conditions in which the skull morphology evolves to adapt to tunnel environment. We evaluated the influence of environmental factors (altitude, temperature, and precipitation) and geographical distance on the variations in skull morphology of a native subterranean rodent plateau zokor population. Thin-plate spline showed that the trend of morphological changes along the CV1 axis was as follows: the two zygomatic arch and the two postorbital processes moved down, the two mastoid processes and the tooth row moved upward, and the tympanic bulla grew longer. The changes along the CV2 axis were as follows: the nasal bone and the tooth row became longer, the distance between the two anterior tips of zygomatic arch lengthened, the infraorbital foramen became smaller, the whole posterior part of the skull became shorter, the zygomatic bone and the two posterior tips of zygomatic arch moved down, and the foramen magnum became bigger. Thus we found significant differences in the skull shape among the seven populations studied. Along with the reduction in the altitude and increase in the mean annual temperature and mean annual precipitation, the nasal bone became shorter, the distance between the two anterior tips of the zygomatic arch became shorter, the whole posterior part of the skull lengthened, the infraorbital foramen became smaller, the two mastoid processes moved upward, and the occipital bone moved down on the dorsal surface of the skull. On the ventral surface of the skull, with an increase in the altitude, mean annual temperature, and mean annual precipitation, the tympanic bulla became shorter, the tooth row moved down, and the foramen magnum became smaller. The morphological changes in the skull were significantly positively correlated with environmental factors. Finally, there was a significant positive correlation between the Procrustes distance matrix of the skull and the geographic distance matrix, which indicates that the evolution of the plateau zokor follows the distance isolation model, but it needs to be further explored from genetic perspectives.

Ontogenetic and interspecific variation in skull morphology of two closely related species of toad, Bufo bufo and B. spinosus (Anura: Bufonidae)

Using micro-CT and 3D landmark-based geometric morphometrics, I investigated postmetamorphic shape variation in the skull of Bufo bufo and Bufo spinosus, two widespread European toad species with small phenotypic differences. Two ontogenetic series were compared, for a total of 58 individuals. They exhibited similar allometric growth patterns, characterised by cranial widening with relative shortening and dorsoventral compression. However, some interspecific shape divergence was observed, particularly among adults: a relatively shorter skull and a more dorsally extended snout distinguished B. spinosus from B. bufo. This disparity, which gives further support to species separation, can probably be ascribed to changes in the allometric trajectories, and seen in light of the evolutionary history of the two lineages.

Intra-specific variation in skull morphology of juvenile Chelonia mydas in the southwestern Atlantic Ocean

The genetic diversity and skull morphology of juvenile Chelonia mydas recruited to the southwestern Atlantic were evaluated to quantify intraspecific variation in the skull shape and size related to (1) broad geographic origin and (2) age (within the most abundant haplotype). 155 C. mydas stranded at 25o S in Brazil were sampled, with 108 assessed for haplotypes (mtDNA) and 102 aged. The hypothesis of no effects of intrinsic variables on the morphology of three skull views was evaluated via 2D geometric morphometrics. Mixed stock analyses identified ten haplotypes among 12 nesting sites, with Ascension Island dominant (65%), then Suriname (10%) and Sao Tome (9%). Compared to CM-A8 (southern Atlantic and west African haplotype) individuals, those assessed as CM-A5 (northern Atlantic and southern Caribbean haplotype) consistently had different skull shapes, which might affect physiology and behaviour. Within CM-A8, there was a positive relationship between centroid size and age (3–5 years), and differences in ventral shape, possibly attributed to ontogenetic diet shifts. The clear morphological differences between haplotypes could imply evolutionary consequences for genetic diversity and trophic polymorphism if there is increased future bias towards CM-A8 (owing to fewer anthropogenic impacts during/post hatching). Conserving priority Caribbean nesting grounds during regional management initiatives might protect phenotypic variability and ultimately population diversity and resilience.

Morphological variation under domestication: how variable are chickens?

The process of domestication has long fascinated evolutionary biologists, yielding insights into the rapidity with which selection can alter behaviour and morphology. Previous studies on dogs, cattle and pigeons have demonstrated that domesticated forms show greater magnitudes of morphological variation than their wild ancestors. Here, we quantify variation in skull morphology, modularity and integration in chickens and compare those to the wild fowl using three-dimensional geometric morphometrics and multivariate statistics. Similar to other domesticated species, chickens exhibit a greater magnitude of variation in shape compared with their ancestors. The most variable part of the chicken skull is the cranial vault, being formed by dermal and neural crest-derived bones, its form possibly related to brain shape variation in chickens, especially in crested breeds. Neural crest-derived portions of the skull exhibit a higher amount of variation. Further, we find that the chicken skull is strongly integrated, confirming previous studies in birds, in contrast to the presence of modularity and decreased integration in mammals.

Biogeographic variation in skull morphology across the Kra Isthmus in dusky leaf monkeys

Biogeographic variation in skull morphology across the Kra Isthmus in dusky leaf monkeys

Computed tomographic morphometry of tympanic bulla shape and position in brachycephalic and mesaticephalic dog breeds.

Anatomic variations in skull morphology have been previously described for brachycephalic dogs; however there is little published information on interbreed variations in tympanic bulla morphology. This retrospective observational study aimed to (1) provide detailed descriptions of the computed tomographic (CT) morphology of tympanic bullae in a sample of dogs representing four brachycephalic breeds (Pugs, French Bulldogs, English Bulldog, and Cavalier King Charles Spaniels) versus two mesaticephalic breeds (Labrador retrievers and Jack Russell Terriers); and (2) test associations between tympanic bulla morphology and presence of middle ear effusion. Archived head CT scans for the above dog breeds were retrieved and a single observer measured tympanic bulla shape (width:height ratio), wall thickness, position relative to the temporomandibular joint, and relative volume (volume:body weight ratio). A total of 127 dogs were sampled. Cavalier King Charles Spaniels had significantly flatter tympanic bullae (greater width:height ratios) versus Pugs, English Bulldogs, Labrador retrievers, and Jack Russell terriers. French Bulldogs and Pugs had significantly more overlap between tympanic bullae and temporomandibular joints versus other breeds. All brachycephalic breeds had significantly lower tympanic bulla volume:weight ratios versus Labrador retrievers. Soft tissue attenuating material (middle ear effusion) was present in the middle ear of 48/100 (48%) of brachycephalic breeds, but no significant association was found between tympanic bulla CT measurements and presence of this material. Findings indicated that there are significant interbreed variations in tympanic bulla morphology, however no significant relationship between tympanic bulla morphology and presence of middle ear effusion could be identified.

Geographic Variation in Skull Morphology of the Large Japanese Field Mice, Apodemus speciosus (Rodentia: Muridae) Revealed by Geometric Morphometric Analysis.

We analyzed geographic variation in skull morphology of the large Japanese field mouse (Apodemus speciosus) and determined changes in skull morphology that occurred during the evolutionary history of A. speciosus in relation to the estimated distribution range in the last glacial maximum (LGM). We analyzed 1,416 specimens from 78 localities using geometric morphometric techniques applied to the dorsal side of the cranium and mandible. While large variations within and among the populations in Honshu, Shikoku, and Kyushu were observed, geographic patterns were not observed. Hokkaido and peripheral island populations showed shared differentiation from the Honshu, Shikoku, and Kyushu populations with a larger skull and distinct mandible shape. In addition, these two groups also differed from each other in accumulated random shape variation. Common characteristics found in Hokkaido and peripheral island populations were considered to be the ancestral states, which were retained by geographic isolation from the main islands. Random variations in Hokkaido and the peripheral island populations were formed through stochastic processes in relation to their isolation. Characteristic morphologies widely found in the populations of Honshu, Shikoku, and Kyushu were considered to be derived states that expanded after separation from the peripheral islands. Complex geomorphology and a shift in distribution range related to climate change and altitudinal distribution are suggested to have formed the complex geographic variation in this species.

Cranial morphological differences within U. deningeri – U. spelaeus lineage: A double traditional and geometric morphometrics approach

Abstract Two complete skulls of Ursus deningeri , one recovered from the Middle Pleistocene site of the Sima de los Huesos in the Sierra de Atapuerca (Spain), and the other one from Petralona (Chalkidiki, Greece), were reconstructed through computed tomography. The cranial morphology of U. deningeri was analysed using dual “traditional” and geometric morphometric and compared to extinct and extant Ursidae ( Ursus spelaeus , Ursus arctos , and Ursus americanus ). The goal of this work was to explore the variation in skull morphology between these different taxa. The analysis presented here indicates that combined traditional and geometric morphometric methods could be useful for a taxonomic approach. In this preliminary study, in which only 2D information is used, it is possible to distinguish the three bear lineages presented here. U. deningeri occupies an intermediate position between the U. spelaeus and U. arctos , which supports an early evolutionary stage of U. deningeri within the cave bear phylogenetic lineage. This study establishes that genera of the Ursus can be differentiated based on cranial shape. Combined studies with computed tomography, traditional and geometric morphometrics of endocraneal remains will provide important new evidence about diet, taxonomical and biochronological studies.

Geographic variation in the greater Japanese shrew-mole, Urotrichus talpoides: Combining morphological and chromosomal patterns

Although much information on the species dynamics of small mammals may be gleaned from the integration of morphological and molecular data sets, the two are not routinely combined when species boundaries and definitions are investigated. The greater Japanese shrew-mole (Urotrichus talpoides) presents a rare example of intraspecific and geographical euchromatic chromosomal variation. In this study a combination of 2D landmark-based and outline-based geometric morphometric methods were used to provide the first quantitative examination of variation in skull morphology occurring between populations of U. talpoides. Geographic variation was found to be most conspicuous in ventral and dorsal cranial morphology, and less evident for outline-based analyses of the dentary, thereby indicating differing magnitudes of skeletal plasticity associated with geographic variation in each system. Both ventral and dorsal cranial morphology differed significantly between shrew-moles from western and eastern Honshu, in agreement with previously identified chromosomal variation boundaries. Inclusion of other island populations revealed shape differences between shrew-moles in Kyushu, Tsushima and North Honshu. These results lend general support for the unification of morphological and chromosomal data when assessing species boundaries.

Revisando el estatus taxonómico y la partición ecológica de los monos nocturnos del género Aotus en el noroccidente de Colombia, con notas sobre Aotus zonalis Goldman, 1914

As part of the project Programa Regional de Biodiversidad, subprograma Linea Base de Conoci- miento de la Biodiversidad del Choco , designed to document the mammalian fauna of the Biogeographic Choco, museum voucher specimens from the Colombian Chocoan Region deposited in American institutions have been taxonomically assessed in the past three years. Herein, we review the morphological variation, distribution patterns, and taxonomy of night monkeys in the genus Aotus from northwestern Colombia deposited at the Field Museum of Natural History (FMNH), and GIS based analyses and Maxent modeling are used to define the geographic extent and ecological limiting factors of the analyzed taxa. Our Principal Component Analysis showed high variation in skull morphology among Aotus from northwestern Colombia. However, differences observed in both discrete and morphometric analyses of the interorbital region of A. zonalis (more depressed than that in the grographically adjacent A. griseimembra and A. lemurinus ) appear as good diagnostic characters for this taxon. Our analyses on the ecological variation associated with collecting localities of Aotus specimens support the geographic subdivision previously proposed based on karyotypic data. Based on obtained models of potential distribution we define the location and extent of potential contact zones among species of Aotus from northwestern Colombia.