Suoidea du Miocène inférieur de Laugnac (Lot-et-Garonne, France)

The fossil vertebrate locality of Laugnac is the type locality of the Neogene mammalian zone MN2b. It has yielded many remains of Suoidea belonging to two different genera.Xenohyus venitor is characterized by its large size and especially its large central upper incisors, I1/ and I2/. It is quite difficult to know its phyletic relationships because the material is not abundant.Hyotherium cf.meisneri is more abundant with a quite good skull, pieces of skull, jaws and isolated teeth. It belongs to a peculiar lineage different from that ofH. major from Saint Gérand-le-Puy, France. It has some similarities withAureliachoerus aurelianensis from later geological levels (MN3-MN5).     

The mechanism of olfactory organ ventilation in Periophthalmus barbarus (Gobiidae, Oxudercinae)

Periophthalmus barbarus Linnaeus, 1766 has many adaptations for amphibious life as a consequence of tidal zone occupation. One of them is the ability to keep a little amount of water and air in mouth while on land or in hypoxic water, correlated with closing a gill lid for gas exchange improvement. It causes that mechanisms of olfactory organ ventilation described in other species of actinopterygians (compression of accessory nasal sac(s) by the skull and jaw elements while mouth and gill lid moving) are not in operation. There is a specific mechanism of olfactory organ ventilation independent on jaw and skull elements movements. Compression of accessory nasal sacs is possible by a0 contraction and it is a movement effect on bones combined by ligaments. This process can be observed on P. barbarus as lifting the rostral part of the head.     

Sexual dimorphism of Dall's porpoise and harbor porpoise skulls

To evaluate and quantify sexual dimorphism of skull shape and assess the ontogenetic background for differences, samples of 134 harbor porpoise (Phocoena phocoena) and 85 Dall's porpoise (Phocoenoides dalli) were compared in terms of cranial shape and shape ontogeny using three-dimensional geometric morphometrics. After correction for allometry, no sexual differences were detected in harbor porpoise, while Dall's porpoise showed statistically significant sexual dimorphism of skull shape. Since no sex-specific differences were detected in the directionalities of the ontogenetic vectors, we cannot reject that the dimorphism is innate. Based on the different mating systems of the two species and the lack of sexual dimorphism in the harbor porpoise, the dimorphism in Dall's porpoise is most likely a result of sexual selection in relation physical competition for mates given that male skulls provide room for larger neck muscles with a more favorable lever arm.     

The genetic basis of adrenal gland weight and structure in BXD recombinant inbred mice

Adrenal gland function is mediated through secreted hormones, which play a vital role in the autonomic and hypothalamic-pituitary-adrenal (HPA)-axis-mediated stress response. The genetic underpinnings of the stress response can be approached using a quantitative trait locus (QTL) analysis. This method has been used to investigate genomic regions associated with variation in complex phenotypes, but it has not been used to explore the structure of the adrenal. We used QTL analyses to identify candidate genes underlying adrenal weight and adrenal cortical zone and medulla widths. We used 64 BXD recombinant inbred (RI) strains of mice (n?=?528) and 2 parental strains (C57BL/6J and DBA/2J; n?=?20) to measure adrenal weights and adrenal zone widths. For adrenal weight, we found significant QTLs on chromosome 3 for females (Fawq1) and Chr 4 for males (Mawq1) and suggestive QTLs on Chrs 1, 3, 10, and 14 for females and Chrs 2, 4, 10, 17, and X for males. We identified a significant QTL on Chr 10 (Mawdq1) and a suggestive QTL on Chr 13 for male adrenal total width. For male adrenal medulla width, we found a significant QTL on Chr 5 (Mmwdq1) and a suggestive QTL on Chr 1. We also identified significant QTLs on Chrs 10 (Mxwdq1) and 14 (Mxwdq2) for male X-zone width. There are 113 genes that mapped within the significant QTL intervals, and we identified 4 candidate genes associated with adrenal structure and/or function. In summary, this study is an important first step for detecting genetic factors influencing the structure of the adrenal component of the HPA axis using QTL analyses, which may relate to adrenal function and provide further insights into elucidating genes critical for stress-related phenotypes.     

A new skull of early cetacean Remingtonocetus harudiensis from the Eocene of Kutch Basin,India

A nearly complete skull of Remingtonocetus harudiensis was discovered from the Harudi Formation of the Kutch Basin, western India. Though several specimens have been collected over the last two decades by earlier workers, this skull shows variations in morphology within the species that were not known earlier. Hence, this finding is significant because it helps in expanding our knowledge of the skull morphology with the addition of characters such as the larger size of the skull, the difference in dental morphology, and the two-ridged external nasal feature and our understanding of how the molar morphology can vary within the same species. The newly excavated skull is the largest Remingtonocetus skull so far discovered and is similar to the size of Dalanistes ahmedi from Kutch, India and from Baluchistan, Pakistan. Thus, the range of the overall body size of the species will change considerably towards the higher side nullifying a major distinction between Dalanistes and Remingtonocetus. The new skull was excavated from the chocolate brown shales of the clastic facies of the Harudi Formation, in the inner ramp of a lagoonal phase. It is approximately 4 m above the nodular limestones from which the other Remingtonocetus materials were previously described. The limestone represents the carbonate facies of the Formation formed in a middle to outer ramp setting. An emended diagnosis of R. harudiensis is provided in this study. The Bartonian Harudi Formation of the Kutch Basin, thus, becomes unique in having Remingtonocetus specimens discovered from two different lithological facies from both the inner and outer ramp settings.     

New insights into the skull of Istiodactylus latidens (Ornithocheiroidea, Pterodactyloidea)

The skull of the Cretaceous pterosaur Istiodactylus latidens, a historically important species best known for its broad muzzle of interlocking, lancet-shaped teeth, is almost completely known from the broken remains of several individuals, but the length of its jaws remains elusive. Estimates of I. latidens jaw length have been exclusively based on the incomplete skull of NHMUK R3877 and, perhaps erroneously, reconstructed by assuming continuation of its broken skull pieces as preserved in situ. Here, an overlooked jaw fragment of NHMUK R3877 is redescribed and used to revise the skull reconstruction of I. latidens. The new reconstruction suggests a much shorter skull than previously supposed, along with a relatively tall orbital region and proportionally slender maxilla, a feature documented in the early 20^th century but ignored by all skull reconstructions of this species. These features indicate that the skull of I. latidens is particularly distinctive amongst istiodactylids and suggests greater disparity between I. latidens and I. sinensis than previously appreciated. A cladistic analysis of istiodactylid pterosaurs incorporating new predicted I. latidens skull metrics suggests Istiodactylidae is constrained to five species (Liaoxipterus brachyognathus, Lonchengpterus zhoai, Nurhachius ignaciobritoi, Istiodactylus latidens and Istiodactylus sinensis) defined by their distinctive dentition, but excludes the putative istiodactylids Haopterus gracilis and Hongshanopterus lacustris. Istiodactylus latidens, I. sinensis and Li. brachyognathus form an unresolved clade of derived istiodactylids, and the similarity of comparable remains of I. sinensis and Li. brachyognathus suggest further work into their taxonomy and classification is required. The new skull model of I. latidens agrees with the scavenging habits proposed for these pterosaurs, with much of their cranial anatomy converging on that of habitually scavenging birds.     

Body size of the weasel Mustela nivalis and the stoat M. erminea in Sweden

In this study we examined temporal and geographical variations in a sample of 124 skulls of the weasel Mustela nivalis and 146 skulls of the stoat M. erminea, collected in Sweden between 1959-1992 and 1913-1990, respectively.We used Principal Component Analysis (PCA) to combine the effects of latitude, longitude, year of collection, mean ambient temperature and Net Primary Productivity (NPP). The first principal component (PC1) contained latitude, ambient temperature and NPP and was significantly and positively related to male (but not female) skull size of both stoats and weasels. None of the other factors or their interactions were significantly related to skull size.We conclude that ambient temperature, either directly through energy savings, or indirectly through improved food availability (increased NPP), had a significant effect on determining body size of male stoats and weasels in Sweden. Our results support the hypothesis that male and female of these species are affected by different selection pressures and thus react differently to changing environmental conditions.     

Three-dimensional computer simulations of feeding behaviour in red and giant pandas relate skull biomechanics with dietary niche partitioning

The red (Ailurus fulgens) and giant (Ailuropoda melanoleuca) pandas are mammalian carnivores convergently adapted to a bamboo feeding diet. However, whereas Ailurus forages almost entirely on younger leaves, fruits and tender trunks, Ailuropoda relies more on trunks and stems. Such difference in foraging mode is considered a strategy for resource partitioning where they are sympatric. Here, we use finite-element analysis to test for mechanical differences and similarities in skull performance between Ailurus and Ailuropoda related to diet. Feeding simulations suggest that the two panda species have similar ranges of mechanical efficiency and strain energy profiles across the dentition, reflecting their durophagous diet. However, the stress distributions and peaks in the skulls of Ailurus and Ailuropoda are remarkably different for biting at all tooth locations. Although the skull of Ailuropoda is capable of resisting higher stresses than the skull of Ailurus, the latter is able to distribute stresses more evenly throughout the skull. These differences in skull biomechanics reflect their distinct bamboo feeding preferences. Ailurus uses repetitive chewing in an extended mastication to feed on soft leaves, and Ailuropoda exhibits shorter and more discrete periods of chomp-and-swallow feeding to break down hard bamboo trunks.     

Morphometric study of allometric skull growth in the temnospondyl Archegosaurus decheni from the Permian/Carboniferous of Germany

The skulls of ninety-six specimens of the temnospondyl Archegosaurus decheni from the Permian/Carboniferous of Germany, ranging in length from almost 20 to almost 280 mm, are used in a morphometric analysis of cranial ontogeny. A Cartesian transformation, a bivariate regression analysis, and a principal component analysis (PCA) reveal changes of general skull proportions and of particular skull roofing bones during growth. The preorbital part of the skull exhibits a much faster growth rate than the postorbital region, whereas the orbits exhibit a considerable decrease in relative size. The skull bones possess low allometry coefficients of growth in width, what leads to a proportionally much more slender skull than in most other temnospondyls, comparable only to other archegosaurids, the cochleosaurid Chenoprosopus, and longirostrine stereospondyls like Australerpeton and trematosaurids. Distinctly negative allometry of the width of the cheek region, where part of the adductor musculature originated, suggests a weaker bite in A. decheni than in temnospondyls with broad-parabolic skulls like Onchiodon and Sclerocephalus. Results from the analysis of skull growth in A. decheni offer a biological interpretation of the life habits of this animal as becoming increasingly more adaptated to piscivory during ontogeny. The continuous growth of the skull with a gradual shift in proportions supports, in conjunction with morphological data, the hypothesis that A. decheni did not undergo a metamorphosis.     

Skull deformations in craniosynostosis and endocrine disorders: Morphological and tomographic analysis of the skull from the crypt of the Silesian Piasts in Brzeg (16th–17th century), Poland

Results

of morphological and tomographic (CT) studies of the skull that was found in the crypt of the Silesian Piasts in the St. Jadwiga church in Brzeg (Silesia, Poland) are presented and discussed here. The established date of burial of probably a 20–30 years old male was 16th–17th century. The analyzed skull showed premature obliteration of the major skull sutures. It resulted in the braincase deformation, similar to the forms found in oxycephaly and microcephaly. Tomographic analysis revealed gross pathology. Signs of increased intracranial pressure, basilar invagination and hypoplasia of the occipital bone were observed. Those results suggested the occurrence of the very rare Arnold-Chiari syndrome. Lesions found in the sella turcica indicated the development of pituitary macroadenoma, which resulted in the occurrence of discreet features of acromegaly in the facial bones. The studied skull was characterized by a significantly smaller size of the neurocranium (horizontal circumference 471 mm, cranial capacity ∼1080 ml) and strongly expressed brachycephaly (cranial index = 86.3), while its height remained within the range for non-deformed skulls. A narrow face, high eye-sockets and prognathism were also observed. Signs of alveolar process hypertrophy with rotation and displacement of the teeth were noted. The skull showed significant morphological differences compared to both normal and other pathological skulls such as those with pituitary gigantism, scaphocephaly and microcephaly.     

The morphology and post-hatching development of the skull of Bolitoglossa nicefori (Caudata: Plethodontidae): developmental implications of recapitulation and repatterning

The cranial morphology of the direct-developing salamander Bolitoglossa nicefori and its post-hatching development are described and compared with that of other urodeles. Four stages of cranial development are defined on the basis of conspicuous events that occur during post-hatching ontogeny. The adult skull morphology of B. nicefori is similar to that of other plethodontids; however, some regions show interspecific variation. The post-hatching ontogeny of the skull and the stage of ossification observed in the hatchlings of B. nicefori show two important ontogenetic features: (1) a mosaic of early larval, metamorphic and post-metamorphic skull features in hatchlings, and (2) absence of characteristic larval elements in skull and hyoid apparatus. The distinctive stage of ossification in the hatchlings of B. nicefori could be caused by heterochronic changes in the ossification sequence, compared to the ontogeny of metamorphic salamanders. The possible heterochronic changes and the absence of larval traits are perhaps due to ontogenetic repatterning, yet without an obvious impact on the adult skull morphology (absence of morphological novelties). This might indicate a compartmentalized development. Further studies should be performed in order to establish the possible occurrence of recapitulatory patterns or ontogenetic repatterning in the skull morphogenesis of B. nicefori during its embryonic development.     

Bergmann’s rule for Neomys fodiens in the middle of the distribution range

The body size of Palearctic Sorex shrews decreases at higher latitudes, and as such the Bergmann’s rule does not work. However, no analysis has ever been done for water shrew (Neomys fodiens) in the middle of distribution range. Analysis of available literature data showed that some body and skull measurements of N. fodiens are negatively correlated to latitude. Measurements of 158 water shrews from Estonia and Lithuania were also analyzed with respect to the short scale latitudinal pattern. We found that populations are separated (Wilk’s lambda = 0.363, p<0.0001). Differences are related to PC1 (skull size), explaining 49.80% of the variance and PC2 (body size), explaining 10.06% of the variance. Estonian shrews are smaller in their body and skull (most differences significant) and their skulls are relatively shorter and wider in the area of the brain case. Thus, the negative correlation of body and skull size to latitude in N. fodiens is applicable even over quite short latitudinal distances. Further analysis of diagnostic characters between N. fodiens and N. anomalus is required.     

The systematic status of the Italian wolfCanis lupus

In the past, the gray wolfCanis lupus Linnaeus, 1758, has been recognized in Italy as either the subspecieslupus oritalicus. It has also been postulated that this population has undergone introgression from the domestic dogCanis familiaris. In order to clarify these issues, multistatistical analyses were made of 10 skull measurements of 34 full grown male wolves from the Italian Peninsula, 91 other male Eurasian wolves, and 20 domestic dogs. The analyses, together with other morphological evidence and prior genetic research, support recognition of the Italian wolf as a separate subspecies,Canis lupus italicus. The same evidence indicates that the subspecies has not been affected through hybridization with the domestic dog.     

The first complete skull of Simopithecus darti from Makapansgat,South Africa,and its systematic position

The skull of a subadult female of Simopithecus darti from the “Upper Phase I” of the Makapansgat Limeworks, South Africa, is described. It is the first complete skull of Simopithecus which is recorded from the lower Pleistocene “Australopithecine cave deposits” of southern Africa. The present skull shows an interesting mixture of primitive and advanced features. In some respects, it is reminiscent of Parapapio, in others it seems to have affinities with the extant Theropithecus gelada rather than with Simopithecus oswaldi. The systematics of the fossil genus Simopithecus and of the tribe Theropithecini Jolly (1966) are discussed.     

Age variability of the sexual size dimorphism in sables in nature and captivity

Inter-sexual differences in craniometric parameters were studied in sables of varying sex and age in natural (n = 2338) and farm (n = 516) populations. In nature, the differences between the skull size in males and females are, as a rule, highly significant (p < 0.001) and the size dynamics correlate well with age. In the farm population, the difference in the skull size between the sexes is statistically significant (p < 0.01), but the correlation of sizes with age is absent. In natural populations, index of sexual dimorphism (ISD) correlate positively with age, with a maximum correlation found in the animals aged nine and a minimum found in juveniles. The index of sexual dimorphism grows considerably until three years of age, after which the dynamics resemble a cyclical process with a repetition of maximum values each fourth year with a general trend of growth in the ISD. The highest values of ISD in farm sables are registered at 3?C5 years of age, while the minimum ones are noted in the age groups of 6?C9 and 13?C14 years of age. In nature, juveniles aged 6?C10 months are characterized by a tendency to general growth (which is not manifested in the introduced population from the basin of the Vakh River) and increase in the SD index with age. The Vakh population is characterized by a decrease in the SD index. The specific rate of skull growth in males is 1.8-fold higher than in females. The age dynamics of the skull size and the vectors of rates between the sexes are not in accordance, as a rule. The results of our study correspond to the theory by Geodakyan (1991) about dichronomorphism. In our opinion, the differences in age manifestations of sexual dimorphism and postnatal skull growth in natural and farm sable populations are determined by the different directions of selection.     

The Braincase of Eocaecilia micropodia (Lissamphibia,Gymnophiona) and the Origin of Caecilians

The scant fossil record of caecilians has obscured the origin and evolution of this lissamphibian group. Eocaecilia micropodia from the Lower Jurassic of North America remains the only stem-group caecilian with an almost complete skull preserved. However, this taxon has been controversial, engendering re-evaluation of traits considered to be plesiomorphic for extant caecilians. Both the validity of the placement of E. micropodia as a stem caecilian and estimates of the plesiomorphic condition of extant caecilians have been questioned. In order to address these issues, the braincase of E. micropodia was examined via micro-computed tomography. The braincase is considered to be a more reliable phylogenetic indicator than peripheral regions of the skull. These data reveal significant new information, including the possession of an ossified nasal septum, ossified anterior wall of the sphenethmoid, long anterolateral processes on the sphenethmoid, and paired olfactory nerve foramina, which are known only to occur in extant caecilians; the latter are possibly related to the evolution of the tentacle, a caecilian autapomorphy. A phylogenetic analysis that included 64 non-amniote taxa and 308 characters represents the first extensive test of the phylogenetic affinities of E. micropodia. The results place E. micropodia securely on the stem of extant caecilians, representing a clade within Temnospondyli that is the sister taxon to batrachians plus Gerobatrachus. Ancestral character state reconstruction confirms the braincase of E. micropodia to be largely representative of the plesiomorphic condition of extant caecilians. Additionally, the results refine the context within which the evolution of the caecilian form can be evaluated. The robust construction and pattern of the dermal skull of E. micropodia is interpreted as symplesiomorphic with advanced dissorophoid temnospondyls, rather than being autapomorphic in its robust construction. Together these data increase confidence in incorporating E. micropodia into discussions of caecilian evolution.     

The population biology and genetics of the deep-sea spider crab,Encephaloides armstrongi Wood-Mason 1891 (Decapoda: Majidae)

Numerous specimens of the majid spider crab, Encephaloides armstrongi, were sampled from six stations (populations) between 150 and 650 m depth, on the continental slope off the coast of Oman. This extended the known geographic and bathymetric range of E. armstrongi, which is now known to occur along the continental margins of the northern Indian Ocean from the western coast of Burma to the coast of Oman. This band-like distribution is contiguous to the oxygen minimum zone in this region.The biology and genetics of populations of Encephaloides armstrongi separated by depth were studied. The overall sex ratio of the E. armstrongi sampled was male-biased (p less than 0.01; 3.3 males: 1 female; S_o = 0.538). However, sex ratio varied both between populations (p less than 0.01) and between size classes of crabs. Size frequency analysis indicated that the male and female crabs consisted of at least two instars, one between 6 and 16mm carapace length and one between 16 and 29 mm carapace length, which probably represented the terminal (pubertal) moult for most individuals. Accumulation of female crabs in the terminal instar probably caused the variation of sex ratio with size classes. Some male crabs grew to a larger size (up to 38 mm carapace length), possibly as a result of maturity at later instars.Length frequency distribution was significantly different between sexes (one-way ANOVA p less than 0.001). Within sexes, length frequency distributions varied between different populations. In both male and female Encephaloides armstrongi the individuals from a single population located at 150 m depth were significantly smaller than individuals at all other stations and were considered to represent a juvenile cohort. For female crabs no other significant differences were detected in length frequency between populations from 300 m to 650 m depth. Significant differences in length frequency were detected between male crabs from populations between 300 and 650 m depth.Horizontal starch gel electrophoresis was used to detect six enzyme systems coding for eight loci for individuals sampled from each population of Encephaloides armstrongi. Genetic identity (I) values between populations of E. armstrongi (I = 0.98-1.00) were within the normal range for conspecific populations. Observed heterozygosity (H_o = 0.080-0.146) was lower than expected heterozygosity (H_e = 0.111-0.160), but in the normal range detected for eukaryotic organisms.F-statistics were used to analyse between population (F_ST) and within population (F ) genetic structure. For both male and female E. armstrongi significant genetic differentiation was detected between the population located at 150 m depth and all other populations. Analyses of F_IS and F_ST, excluding the 150 m population indicated that for female E. armstrongi there was no significant structuring within or between populations. For male E. armstrongi significant heterozygote deficiencies were detected within populations and significant genetic differentiation between populations.The most likely explanations for the observations of the present study are: the population of Encephaloides armstrongi located at 150 m depth represented a juvenile cohort that is genetically distinct from deeper populations; female E. armstrongi formed a single population between 300 m and 650 m depth in the sampling area; male E. armstrongi were from two or more genetically distinct populations which are represented by different numbers of individuals at stations between 300 m and 650 m depth. This caused the observed significant differences in morphology (size distribition) and allele frequencies of male populations. It is likely that E. armstrongi exhibits gender-biased dispersal and that the crabs collected between 300 m and 650 m depth formed spawning aggressions. This also explains the bias in sex ratio of individuals sampled in the present study.     

Pleistocene Extinctions and the Perceived Morphofunctional Structure of the Neotropical Felid Ensemble

The felid Neotropical ensemble has experienced important changes from the Pleistocene to the present, the extinction of sabertooth cats being the most significant. Assuming that the morphofunctional structure of the Neotropical felid ensemble was maximally expressed when machairodontines were present, we added specimens of Smilodon fatalis and S. populator to a morphological dataset inclusive of all extant species of Neotropical felids to explore the hypothetical effect of extinction of machairodontines on the perceived morphofunctional structure of the ensemble. We studied 321 specimens of 12 extant species of Neotropical felids plus S. populator and S. fatalis by measuring 123 skull and postcranial morphofunctional variables. We used Principal Component Analysis to find morphofunctional patterns of the skull, postcranium, and both combined (with and without correction for size) of both ensembles, past (with Smilodon) and present (with Smilodon lost to extinction). Canonical Phylogenetic Ordination was performed to assess the degree of phylogenetic influence on this morphospace. We also explored the effect of including homotherines in the Pleistocene guild by including specimens of North American Homotherium serum. Size was the principal factor structuring ensembles. Important morphological characters were associated to ecological performance of species. A pattern of bodily proportions was apparent: more stout species with larger skull, longer rostrum, stronger bite force, and longer pectoral crests, versus gracile, jumping species with opposing characters. The felid morphospace shrank after the extinction of Smilodon and Homotherium, but the configuration of the portion of space containing extant felids remained stable. This pattern is associated with deep phylogenetic roots.