Changes In Skull Shape Research Articles

Ontogenetic changes in the craniomandibular skeleton of abelisaurid dinosaur Majungasaurus crenatissimus from the Late Cretaceous of Madagascar

Abelisaurid theropods were one of the most diverse groups of predatory dinosaurs in Gondwana during the Cretaceous. The group is characterized by a tall, wide skull and robust cervical region. This morphology is thought to have facilitated specialized feeding behaviors such as prolonged contact with prey. The Late Cretaceous abelisaurid Majungasaurus crenatissimus typifies this abelisaurid cranial morphotype. Recent fossil discoveries of this species include a partial growth series that allows for the first time an investigation of ontogenetic variation in cranial morphology in a representative abelisaurid. Herein we examine growth trajectories in the shape of individual cranial bones and articulated skulls of Majungasaurus using geometric morphometrics. Several major changes in skull shape were observed through ontogeny, including an increase in the height of the jugal, postorbital, and quadratojugal, an increase in the extent of the contacts between bones, and a decrease in the circumference of the orbi...

云南高山姬鼠头骨的几何形态学研究

PDF HTML阅读 XML下载 导出引用 引用提醒 云南高山姬鼠头骨的几何形态学研究 DOI: 10.5846/stxb201409011737 作者: 作者单位: 云南师范大学生命科学学院,云南师范大学生命科学学院,云南师范大学生命科学学院,云南师范大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31360096);云南省应用基础研究计划重点项目(2013FA014);获云南省博士研究生学术新人奖资助 Geometric morphometric research of the skull of Apodemus chevrieri from Yunnan Province Author: Affiliation: School of Life Sciences,Yunnan Normal University,School of Life Sciences,Yunnan Normal University,School of Life Sciences,Yunnan Normal University,Yunnan Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:表型可塑性是指同一基因型在不同环境条件下而产生多种不同表现型的反应能力。哺乳动物头骨形态的变化是在进化过程中出现的重要表型特征之一。云南省地势西高东低、海拔变化剧烈、是古北界寒带物种南迁,中南半岛热带物种北移的交汇地,自然环境的地带性和非地带性变化明显,栖息在该地区的动物为了适应多样的环境,可能出现不同的表型分化。高山姬鼠(Apodemus chevrieri)为我国特有种,主要分布在中国西南的横断山及其附近地区,是研究表型与生态适应之间关系的理想物种。为研究在云南特殊生态环境下物种的微进化,采用几何形态学的方法测量云南不同地区高山姬鼠头骨形态的变异,采用线粒体细胞色素b(Cytochrome b, Cyt b) 基因和线粒体控制区(Mitochondrial control region, D-loop)探讨基因型的变化。结果显示:昆明种群与横断山种群(中甸、剑川、丽江)间发生了明显的形态变异和遗传分化,高山姬鼠头骨背面和腹面,横断山种群和滇中昆明种群很少重叠,这两个种群变异较大;但头骨的侧面和下颌侧面变异不明显。因此,分布于云南地区的高山姬鼠可能正处于生态物种形成的早期阶段。 Abstract:Phenotypic plasticity is the capacity of individuals to modify their phenotype in response to environmental changes. Fundamental to the way in which organisms cope with environmental variations, phenotypic plasticity is associated with all types of environmentally-induced variations, including changes to morphological, physiological, and behavioral processes. The skull morphology of mammals is the most important phenotypic trait, which changes during the evolutionary process. The Chevrier's field mouse, Apodemus chevrieri is a nocturnal and species endemic to China, and originated in the Palaearctic region. A. chevrieri is mainly distributed in the Hengduan Mountains and nearby regions of China, including Zhaotong, Kunming, Lijiang, Dali, and the land around the Lancang and Nu Rivers in Yunnan Province. A. chevrieri mainly inhabits farmland and its nearby shrubland, and is one of the main natural foci of plague in the Hengduan Mountains, which is a crossroads of species dispersal. The boreal species of the Palaearctic migrating southward, and tropical species from the Indochina Peninsula migrating northward, and thus is an area of interest for biologists studying mammal diversity. Meanwhile, the Hengduan Mountains are located in the west of the Yunnan Province, where there are many mountains and canyons. From west to east, there are dramatic changes in environmental conditions with changes in altitude, and noticeable changes were observed in the zone and non-zone landscape. In order to adapt to the different environments, animals inhabiting the area may exhibit different phenotypic variations, so A. chevrieri was employed as an ideal model for examining the relationships between phenotypic and ecological adaptations. The analysis of morphology is a fundamental part of many biological studies. With the development of more sophisticated statistical techniques, the sophistication of analyses of these types of data also increased. Since the 1980s, there was a fundamental change in the nature of the data gathered and analyzed, as scientists began to focus on the coordinates of landmarks and the geometric information relating to their relative positions. Geometric morphometrics, was hailed as a "revolution" in morphometrics. Morphological divergence among taxa was estimated quantitatively by analyzing the outline of the mandible. This method treats the mandible shape globally, and provides continuous data which can be used to compute phenotypic distances. In order to study the microevolution of species in the Yunnan province, with its special ecological environment, we applied geometric morphometric methods to the study of skull shape changes in different areas of A. chevrieri distribution, and used mitochondrial cytochrome b (Cyt b) gene and control region (D-loop) to investigate the gene type. The results showed that the Kunming and Hengduan Mountain populations (Zhongdian, Jianchuan, and Lijiang) exhibited obvious morphological and genetic variations. In particular, the dorsal and ventral of skull in A. chevrieri rarely overlap between the Hengduan Mountain populations and the Kunming population, with large variations between two populations having been noted. However, the side and lower side of the skull showed no significant variation between populations. Therefore, this study indicates that A. chevrieri in the Yunnan Province might be in the process of undergoing ecological speciation. 参考文献 相似文献 引证文献

Helmet therapy in infants with positional skull deformation: randomised controlled trial

Objective To determine the effectiveness of helmet therapy for positional skull deformation compared with the natural course of the condition in infants aged 5-6 months.Design Pragmatic, single blinded, randomised controlled...

P05 No effect of helmet therapy can be shown in infants with positional skull deformation: a randomised controlled trial

AimsTo determine the effectiveness of helmet therapy compared with the natural course in children aged five months with positional skull deformation, measured at 24 months.MethodsPragmatic randomised controlled trial in 84...

The ontogeny of sexual dimorphism in the skull of the springbok antelope (Antidorcas marsupialis) (918.7)

Antelope (Artiodactyla: Bovidae) provide many classic examples of sexual dimorphism, but the ontogenetic pathway to adult sexual dimorphism has not been systematically studied. Moreover, it is unknown whether the development of obvious sexual differences in horn size correlate with the development of sexual differences in other horn traits, skull size, or skull shape. To better understand springbok skull development in general, and the development of sexual dimorphism in particular, I compared skulls from more than 50 springbok (Antidorcas marsupialis), which had been harvested, sexed and age‐estimated from a wild population in northern Namibia from 1992‐1994, and ranged from 7 months to >5 years old. Seven traits were examined: horn length, circumference, and number of horn rings, and skull size and shape in ventral and lateral views. Skulls were photographed in ventral and lateral views, landmarks were digitized, and 2D geometric morphometric analysis was performed using standard software and procedures. For each trait, male and female values were compared in yearlings and in adults to test the hypothesis that springbok sexual dimorphism increases after one year of age. By one year of age, males were significantly larger than females in horn length, horn circumference, and the sexes differed significantly in lateral skull shape. After one year of age, sexual differences increase in horn circumference and lateral skull size, and decrease and then reverse in the number of horn rings. Sexual differences were observed in nearly all trait studied. However, sexual differences arose at various times for the different traits. Whether these differences increased, were maintained, or reversed with age also depended on the trait. The developmental timing of sexual differences in size and shape indicates that sex‐specific changes in skull shape, and not allometry through male growth, are the primary mechanism for achieving sexual differences in skull shape.Grant Funding Source: Supported by an NSF‐GRF pre‐doctoral fellowship.

A new fossil species supports an early origin for toothed whale echolocation

Odontocetes (toothed whales, dolphins and porpoises) hunt and navigate through dark and turbid aquatic environments using echolocation; a key adaptation that relies on the same principles as sonar. Among echolocating vertebrates, odontocetes are unique in producing high-frequency vocalizations at the phonic lips, a constriction in the nasal passages just beneath the blowhole, and then using air sinuses and the melon to modulate their transmission. All extant odontocetes seem to echolocate; however, exactly when and how this complex behaviour--and its underlying anatomy--evolved is largely unknown. Here we report an odontocete fossil, Oligocene in age (approximately 28 Myr ago), from South Carolina (Cotylocara macei, gen. et sp. nov.) that has several features suggestive of echolocation: a dense, thick and downturned rostrum; air sac fossae; cranial asymmetry; and exceptionally broad maxillae. Our phylogenetic analysis places Cotylocara in a basal clade of odontocetes, leading us to infer that a rudimentary form of echolocation evolved in the early Oligocene, shortly after odontocetes diverged from the ancestors of filter-feeding whales (mysticetes). This was followed by enlargement of the facial muscles that modulate echolocation calls, which in turn led to marked, convergent changes in skull shape in the ancestors of Cotylocara, and in the lineage leading to extant odontocetes.

Skeletogenesis in anurans: cranial and postcranial development in metamorphic and postmetamorphic stages of Leptodactylus bufonius (Anura: Leptodactylidae)

AbstractOsteological studies of anurans generally have focused on the descriptions of adults and larval chondrocrania, including developmental series of chondrocrania. Thus, the changes occurring during postmetamorphic stages have largely been overlooked. Herein, we describe cranial and postcranial skeletogenesis, and change in skull shape through the metamorphic and postmetamorphic development of Leptodactylus bufonius. Several elements, particularly those of the cranium, are already ossified at metamorphic climax; among these elements are the frontoparietals, prootics, premaxillae, maxillae, squamosals, pterygoids, neopalatines, angulosplenials, dentaries, mentomeckelians, and the mesosternum. Determining the exact timing of ossification of some elements is difficult because variation in their development may result from extrinsic factors. The otic region and that of the jaw closure undergo the greatest changes in shape, which may imply functional constraints. The development of many skeletal elements is still incomplete at metamorphosis; thus, the changes occurring postmetamorphically are crucial to achieving the configuration and function of an adult skeleton. María Laura Ponssa. CONICET. Instituto de Herpetología, Fundación Miguel Lillo. S. M. de Tucumán, c/p (4000), Argentina. E‐mail: mlponssa@hotmail.com.

DIETARY HARDNESS, LOADING BEHAVIOR, AND THE EVOLUTION OF SKULL FORM IN BATS

The morphology and biomechanics of the vertebrate skull reflect the physical properties of diet and behaviors used in food acquisition and processing. We use phyllostomid bats, the most diverse mammalian dietary radiation, to investigate if and how changes in dietary hardness and loading behaviors during feeding shaped the evolution of skull morphology and biomechanics. When selective regimes of food hardness are modeled, we found that species consuming harder foods have evolved skull shapes that allow for more efficient bite force production. These species have shorter skulls and a greater reliance on the temporalis muscle, both of which contribute to a higher mechanical advantage at an intermediate gape angle. The evolution of cranial morphology and biomechanics also appears to be related to loading behaviors. Evolutionary changes in skull shape and the relative role of the temporalis and masseter in generating bite force are correlated with changes in the use of torsional and bending loading behaviors. Functional equivalence appears to have evolved independently among three lineages of species that feed on liquids and are not obviously morphologically similar. These trends in cranial morphology and biomechanics provide insights into behavioral and ecological factors shaping the skull of a trophically diverse clade of mammals.

How We Got Here: Evolutionary Changes in Skull Shape in Humans & Their Ancestors

This activity uses inquiry to investigate how large changes in shape can evolve from small changes in the timing of development. Students measure skull shape in fetal, infant, juvenile, and adult chimpanzees and compare them to adult skulls of Homo sapiens, Homo erectus, and Australopithecus afarensis. They conclude by re-interpreting their findings in light of Ardipithecus ramidus.

Allometry in the distribution of material properties and geometry of the felid skull: Why larger species may need to change and how they may achieve it

Extant members of the cat family (Felidae) have been considered behaviourally and morphologically conservative, i.e., despite great differences in size, there is relatively little variation in either the shape of the felid skull and dentition across species, or in the way in which these structures are used to kill and dismember prey. Consequently felids have been considered an appropriate focus for a number of investigations into the influence of allometry on craniomandibular mechanics and morphology. However, although previous treatments have considered the role of shape, they have not investigated the influence of differences in the distribution of relatively stiff cortical and more compliant cancellous bone on performance. Here, using models that incorporate material properties for both cortical and cancellous bone, we apply three-dimensional (3D) finite element analysis (FEA) to models representing the skulls of seven extant felid species. Our objectives being to determine allometric trends regarding both overall geometry and the relative distributions of cortical and cancellous bone tissue. We also more comprehensively assess variation in the efficiency with which muscular force is converted to bite force and the capacity to resist associated stresses. Our results show that the cheetah ( Acinonyx jubatus) may be exceptional regarding both the efficiency with which muscular force is converted to bite force and the distribution of stress. We found a negative allometric trend between cortical bone volume and total skull bone volume, and positive allometry between the total skull bone volume and skull surface area. Results gained from mathematical modelling of beam analogies suggest that these trends reflect a need for larger species to respond to physical challenges associated with increased size, and, that changes in skull shape, bone composition, or a combination of both may be required to accommodate these challenges. With geometrical scaling stress increases by the same factor, and displacement by the same factor squared, but the ultimate failure stress of the material is invariant. We find that as species become larger, overall skull bone volume relative to surface area increases by adding a higher proportion of less dense and more compliant cancellous bone. This results in an increased cross-sectional area and second moment of inertia, which acts to reduce the overall stresses. An overall saving in mass is a likely additional consequence. Although we do find evidence that skull stiffness does diminish with size, we also argue that this is at least in part mitigated through the influence of these allometric trends. We further suggest that these trends and the explanations for them may be universal for vertebrates.

Ontogeny of the cranial skeleton in a Darwin’s finch (Geospiza fortis)

Darwin's finches are a model system in ecological and evolutionary research, but surprisingly little is known about their skull morphology and development. Indeed, only the early beak development and external variation in adult beak shape has been studied. Understanding the development of the skull from embryo up to the adult is important to gain insights into how selection acts upon, and drives, variation in beak shape. Here, we provide a detailed description of the skeletal development of the skull in the medium ground finch (Geospiza fortis). Although the ossification sequence of the cranial elements is broadly similar to that observed for other birds, some differences can be observed. Unexpectedly, our data show that large changes in skull shape take place between the nestling and the juvenile phases. The reorientation of the beak, the orbit and the formation of well-developed processes and cristae suggest that these changes are likely related to the use of the beak after leaving the nest. This suggests that the active use of the jaw muscles during seed cracking plays an important role in shaping the adult skull morphology and may be driving some of the intra-specific variation observed in species such as G.fortis. Investigating the development of the jaw muscles and their interaction with the observed ossification and formation of the skull and lower jaw would allow further insights into the ecology and evolution of beak morphology in Darwin's finches.

Mosaic functionality in a transitional ecomorphology: skull biomechanics in stem Hyaeninae compared to modern South African carnivorans

Ecomorphologies are categories of ecological adaptation and function, although intermediates are not always available to shed light on functionality at the transitional stages between them. We examined an intermediate bone-cracking carnivoran ecomorphology, the stem hyaenine Ikelohyaena abronia, using finite element analysis. Skull models of Ikelohyaena, crown hyaenine Crocuta crocuta, and two other hypercarnivores were simulated with mastication and prey apprehension forces. The results obtained show that Ikelohyaena already possessed derived features in skull stress distribution and levels of strain energy, characteristic of the extant bone-cracking Crocuta; however, the estimated bite forces in Ikelohyaena were significantly lower. Prey apprehension simulations showed similar patterns; the low skull strain energy and low bite force of the Ikelohyaena mandible indicate a poor individual ability to take down large prey. The mosaic features of craniodental function in Ikelohyaena suggest that initial evolution of the hyaenid bone-cracking ecomorphology involved skull shape changes that increased stress dissipation, permitting incorporation of more hard food into the diet. Subsequent evolution of larger bite forces was then required to increase the size limit of bones that can be cracked and consumed. This mode of evolution would have allowed transitional hyaenid ecomorphologies to continuously increase the carcass processing ability both during competitive feeding and scavenging throughout their evolution. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 540–559.

Irreversible microevolutionary changes in genotypic composition of sika deer Cervus nippon populations in response to vegetation degradation and food shortage

The present study deals with changes in important skull characteristics of the sika deer Cervus nippon Temminck, 1838 in response to changes in food supply. Moderate food shortage results mainly in a linear reduction in skull size, while severe food shortage results in changes in skull shape. In the deer that returned to habitats with sufficient food supply, some skull parameters recovered to, or even exceeded, normal values, whereas other parameters remained stressed resulting in retention or enhancement of skull distortions. Differences in skull parameters among the populations studied were comparable to those between some cervid species, eg, the Siberian roe deer Capreolus pigargus Pallas, 1771 and European roe deer Capreolus capreolus Linnaeus, 1758 and other deer subspecies. In the introduced sika deer populations, skull distortions were apparently caused by interspecific hybridization. Descendants of the escaped deer have not reverted to the normal phenotype, even over several generations, providing a recent case of true evolutionary changes. This occurred by a change in the ratio of different morphotypical groups, probably due to their different responses to food shortage. Thus sufficient food supply may account for changes in a population’s genotypic composition through selection of characteristics that favour passing on genetic material when food is limited.

The relationship between shape of the skull and bite force in finches

In finches husking time is non-linearly related to the ratio of seed hardness to maximal bite force. Fringillids produce larger bite force and husk relatively hard seeds faster than estrildids of similar size. This is at least partly explained by their relatively larger jaw muscle mass and a difference in husking technique. However, the effect of differences in skull geometry on bite force is unclear. In this study differences in skull morphology that may contribute to the difference in bite force between fringillids and estrildids are analyzed. The shape of the skull was described by the 3D coordinates of a set of landmarks and, after eliminating size, the effect of differences in the shape of the skull on bite force was determined using a static force model. EMG recordings of jaw muscles during seed cracking were used to validate assumptions about the muscle activation patterns used for the static bite force model. The analysis shows that most of the variation in skull geometry is related to differences in size. Although the shape of the skull is highly convergent between fringillids and estrildids, the shape of the skull differs significantly between the two groups. A principal component analysis of the landmark coordinates shows several patterns of allometric shape changes, one of which is expressed more strongly in estrildids than in fringillids. Three characters dominate the effect of shape changes on bite force. Bite force increases with a more caudal position of the quadrate, a more downward inclined beak and a relatively short jugal and palatine. A more downward inclined beak is typically found in estrildids. The height of the upper bill and a number of other changes in skull shape have little effect on bite force. An estimate of the relative contributions of jaw muscle size and skull geometry to the difference in bite force between fringillids and estrildids suggests that the contribution of muscle size is much larger than the contribution of skull geometry.

On the Cranial Osteology of Chiroptera. I. Pteropus (Megachiroptera: Pteropodidae)

Although detailed anatomical descriptions of skull morphology are available for representatives of many mammalian orders, no such descriptive work exists for bats, a group that comprises over 20% of extant mammalian species. In this paper, we provide a detailed description of the skull of Pteropus (Mammalia: Chiroptera: Megachiroptera: Pteropodidae) and establish a system of cranial nomenclature following the Nomina Anatomica Veterinaria. Based on a series of specimens of Pteropus lylei, we describe the skull as a whole and the morphology of external surfaces of 24 bones (7 rostral, 16 cranial, plus the mandible) and 17 teeth. We describe internal surfaces and additional bones of disarticulated skulls of Pteropus livingstonii and use material from the same species to describe the middle ear ossicles and the petrosal bone. We include a description of the hyoid apparatus and larynx based on Pteropus tonganus and a description of the deciduous dentition based on Pteropus hypomelanus. Using a sectioned fetus, we determine the content and homology of all cranial foramina present in the skull of Pteropus. We outline the ontogenetic changes from newborn pups to adults, considering changes in skull shape and the sequence of bone fusion and tooth eruption. Based on selected comparisons to other megabats, we discuss broad patterns of variation in general cranial shape, and interspecific variation in sutures, foramina, processes, and dentition. Overall, this work establishes a descriptive and nomenclatorial benchmark for chiropteran skull anatomy in line with similar works in other mammalian orders, with the aim of creating common ground for comparative, phylogenetic, and functional studies of the bat skull, including comparisons with other mammals.

Regression equations between body and head measurements in the broad-snouted Caiman (Caiman latirostris).

In the present study, regression equations between body and head length measurements for the broad-snouted caiman (Caiman latirostris) are presented. Age and sex are discussed as sources of variation for allometric models. Four body-length, fourteen head-length, and ten ratio variables were taken from wild and captive animals. With the exception of body mass, log-transformation did not improve the regression equations. Besides helping to estimate body-size from head dimensions, the regression equations stressed skull shape changes during the ontogenetic process. All age-dependent variables are also size-dependent (and consequently dependent on growth rate), which is possibly related to the difficulty in predicting age of crocodilians based on single variable growth curves. Sexual dimorphism was detected in the allometric growth of cranium but not in the mandible, which may be evolutionarily related to the visual recognition of gender when individuals exhibit only the top of their heads above the surface of the water, a usual crocodilian behavior.

Paedogenesis in European newts (Triturus: Salamandridae): Cranial morphology during ontogeny

ABSTRACT A cross-sectional analysis using different ontogenetic stages (larvae, juveniles, paedotypic, and metamorphic adults) of the smooth newt, Triturus vulgaris, and the alpine newt, T.alpestris, revealed a broad spectrum of perennibranchiation influences on cranial ontogeny in European newts, more pronounced than previously thought. These influences included marked variation in ossification levels, pronounced morphometric variability of many cranial elements, and considerable skull shape changes in the transition from larvae to the adult stage. In comparison with metamorphosed individuals, paedotypic newts had a higher level of variability in both individual cranial traits and cranial shape changes. Sexual size difference of the skull traits was mostly negligible, especially in comparison to the influence of paedogenesis. The main changes in cranial shape of the European newts occurred during metamorphosis. Cranial morphological organization in the majority of examined paedotypes corresponds to cranial organization at late larval stages prior to metamorphosis or at the onset of metamorphosis. J. Morphol. 243:127–139, 2000 © 2000 Wiley-Liss, Inc.

Paedogenesis in European newts (Triturus: Salamandridae): Cranial morphology during ontogeny

A cross-sectional analysis using different ontogenetic stages (larvae, juveniles, paedotypic, and metamorphic adults) of the smooth newt, Triturus vulgaris, and the alpine newt, T.alpestris, revealed a broad spectrum of perennibranchiation influences on cranial ontogeny in European newts, more pronounced than previously thought. These influences included marked variation in ossification levels, pronounced morphometric variability of many cranial elements, and considerable skull shape changes in the transition from larvae to the adult stage. In comparison with metamorphosed individuals, paedotypic newts had a higher level of variability in both individual cranial traits and cranial shape changes. Sexual size difference of the skull traits was mostly negligible, especially in comparison to the influence of paedogenesis. The main changes in cranial shape of the European newts occurred during metamorphosis. Cranial morphological organization in the majority of examined paedotypes corresponds to cranial organization at late larval stages prior to metamorphosis or at the onset of metamorphosis.

Obstetrical factors governing the etiopathogenesis of lambdoid synostosis.

Lambdoid synostosis results in skull deformities of varying degrees characterized by occipital flattening over the involved suture and other compensatory changes in skull shape. Such changes include contralateral occipital bossing, contralateral frontal flattening, ipsilateral frontal bossing, and ipsilateral anteroinferior displacement of the pinna (ear shearing). These deformities tend to worsen during the first year of life. The etiology has been attributed to genetic factors and primary disorders of bone growth, in addition to secondary effects of other diseases and modulators of the in utero environment. To determine causal factors in the development of lambdoid synostosis, the authors reviewed medical records of the mothers of 13 children with lambdoid synostosis who were treated at the University Medical Center of the State University of New York at Stony Brook. Pre- and perinatal events, prior obstetrical, gynecological, medical, social, and family histories were considered. Births of normal infants immediately prior to and just after the affected babies were born were selected as controls. There is a significant association between increased duration of the first stage of labor and the development of lambdoid synostosis. Furthermore, our results indicate that this condition has a predilection toward male infants, and may be associated with preterm labor.

Relative warp analysis of skull shape across the hybrid zone of the house mouse (Mus musculus) in Denmark.

The changes in skull shape that occur in the hybrid zone between the two European subspecies of the house mouse (Mus musculus musculus and M. m. domesticus) were studied by relative warp analyses. Landmarks observed on the ventral view of the skulls of 269 mice sampled in 18 localities in Denmark were analysed. Each population was also characterized by a hybrid index estimated from allozymic data. Although no clear pattern of within‐population variability of shape could be established across the hybrid zone, the shape changes among the 18 populations were found to be correlated with the allozymic introgression but not with geographical location. Finally, the cline obtained for skull shape seems to be steeper than that corresponding to the average allozyme hybrid index which suggests that skull development could be slightly perturbed in hybrids.