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61 results for “head shape”
Linking shape conspicuous asymmetry with shape covariation patterns and performance in the insect head and mandibles
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How head shape and substrate particle size affect fossorial locomotion in lizards
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Data from: Does diet drive the evolution of head shape and bite force in chameleons of the genus Bradypodion?
The head is a complex integrated system that is implicated in many vital functions. As such, its morphology is impacted by different and sometimes conflicting demands. Consequently, head shape varies greatly depending on the environment and dietary ecology of an organism. Moreover, given its role in territory defence and mating in lizards, it is also subjected to strong sexual selection in these animals. We investigated the relationships between head shape, bite performance and diet in 14 of the 17 extant Bradypodion species to determine whether variation in diet can explain the observed diversity in bite force and head shape in this genus. We also evaluate differences between sexes in terms of the relationships between head shape, bite force and diet and predict tighter relationships in females given that the head in this sex is principally under natural selection. Our results show that there is indeed a correlation between head shape, diet and bite force, but the direction and magnitude are sex-dependent. Whereas we observed a correlation between absolute bite force and head shape in both sexes, size-corrected bite force was correlated with mandible and quadrate shape in females only. Despite strong correlations between bite force and prey hardness, and between prey hardness and head shape, we did not find any relationship between head shape and prey evasiveness. These data suggest that the cranial system in chameleons of the genus Bradypodion evolves under natural selection for the ability to eat large or hard prey. Moreover, significant differences in the ecomorphological relationships between the two sexes suggest that sexual selection plays a role in driving the evolution of bite force and head shape. These data suggest that ecomorphological relationships may be sex-dependent.
Head-Shaped Fountain (A.D.1770) .::RAWscan::.
Text reads: **IOHANNES POTENZIANI REATINUS PRAECEPTOR ORD°S°SPIRITUS IN SAXIA MONTIS ROMANI AMANTISSIMUS SALUBERRIMIS ACCERSITIS AQUIS AD USUM COMMODUMQUE PUBLICUM FONTEM FACIUNDUM CURAVIT A°D° MDCCLXX** Photogrammetry scan Source: Objaverse 1.0 / Sketchfab
Figure 2 in Using geometric morphometrics for integrative taxonomy: an examination of head shapes of milksnakes (genus Lampropeltis)
Figure 2. The eleven landmarks used for geometric morphometric analyses (A) and the Procrustes superimpostition consensus of the landmarks averaged across all specimens (B).
Figure 4 in Using geometric morphometrics for integrative taxonomy: an examination of head shapes of milksnakes (genus Lampropeltis)
Figure 4. Thin-plate splines of each species warped from the Procrustes consensus alignment of all species.
Figure 1 in Using geometric morphometrics for integrative taxonomy: an examination of head shapes of milksnakes (genus Lampropeltis)
Figure 1. Representatives of the six milksnake species used in the present study; A, Lampropeltis triangulum. B, Lampropeltis gentilis. C, Lampropeltis elapsoides. D, Lampropeltis polyzona. E, Lampropeltis abnorma. F, Lampropeltis micropholis.
Fig. 2. Head sculpture and femora shapes. A, C in A revision of the Afrotropical species of the Dorylinae ant genus Aenictus (Hymenoptera: Formicidae) based on the worker caste
Fig. 2. Head sculpture and femora shapes. A, C, Aenictus guineensis (CASENT0876634). B, Aenictus xegi sp. nov. (NHMUK012849243). D, Aenictus susanae sp. nov. (CASENT0406729).
Data and code from Wang et al. "An evaluation of sexual dimorphism in head size and shape in Red Salamanders (Pseudotriton ruber)"
<p>Data and code from Wang et al., "An evaluation of sexual dimorphism in head size and shape in Red Salamanders (<em>Pseudotriton ruber</em>)"</p>
Head and mandible shapes are highly integrated yet represent two distinct modules within and among worker sub-castes of the ant genus Pheidole
<p>Ants use their mandibles for a wide variety of tasks related to substrate manipulation, brood transport, food processing, and colony defence. Due to constraints involved in colony upkeep, ants evolved a remarkable diversity of mandibular forms, often related to specific roles such as specialized hunting and seed milling. Considering these varied functional demands, we focused on understanding how the mandible and head shape vary within and between <em>Pheidole </em>sub-castes. Using x-ray microtomography and 3D geometric morphometrics, we tested if these structures are integrated and modular, and how ecological predictors influenced these features. Our results showed that mandible and head shape of majors and minor workers tend to vary from robust to slender, with some more complex changes related to the mandibular base. Additionally, we found that head and mandible shapes are characterized by a high degree of integration, but with little correlation with feeding and nesting habits. Our results suggest that a combination of structural (allometric) constraints and the behavioural flexibility conferred by caste dimorphism might largely buffer selective pressures that would otherwise lead to a fine-tuning between ecological conditions and morphological adaptation.</p>
lateral pronotum fan-like on broad setae on) i setae (clove-shaped sericeous pronotum)) and b e ((head pronotum setae on setae on clove-shaped setae sericeous and clove-shaped sericeous and fan-like and with) h (sericeous pronotum setae) fan-like a (and australis head and) d sericeous Morbora (hirtula.) with setae a-c (Morbora dorsum fan-shaped species)) g d-f (= (Morbora fs scutellum schoutedeni; of setae vestiture on Morbora clove-shaped setae of) fan-like g-i = (cs micrographs: short scutellum) Abbreviations c (electron pronotum on setae. Scanning of clove-shaped scutellum: on 13 projections. setae Fig) f ( in Jewel Bugs of Australia (Insecta, Heteroptera, Scutelleridae)
lateral pronotum fan-like on broad setae on) i setae (clove-shaped sericeous pronotum)) and b e ((head pronotum setae on setae on clove-shaped setae sericeous and clove-shaped sericeous and fan-like and with) h (sericeous pronotum setae) fan-like a (and australis head and) d sericeous Morbora (hirtula.) with setae a-c (Morbora dorsum fan-shaped species)) g d-f (= (Morbora fs scutellum schoutedeni; of setae vestiture on Morbora clove-shaped setae of) fan-like g-i = (cs micrographs: short scutellum) Abbreviations c (electron pronotum on setae. Scanning of clove-shaped scutellum: on 13 projections. setae Fig) f (
Head and mandible shapes are highly integrated yet represent two distinct modules within and among worker sub-castes of the ant genus Pheidole
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Data from: Does diet drive the evolution of head shape and bite force in chameleons of the genus Bradypodion?
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Data from: Effects of environmental disturbance on phenotypic variation: an integrated assessment of canalization, developmental stability, modularity and allometry in lizard head shape
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Data from: Getting a head in hard soils: convergent skull evolution and divergent allometric patterns explain shape variation in a highly diverse genus of pocket gophers (Thomomys)
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nkx3.2 mutant zebrafish accommodate jaw joint loss through a phenocopy of the head shapes of Paleozoic jawless fish
The vertebrate jaw is a versatile feeding apparatus. To function, it requires a joint between the upper and lower jaws, so jaw joint defects are often highly disruptive and difficult to study. To describe the consequences of jaw-joint dysfunction, we engineered two independent null alleles of a single jaw-joint marker gene, <i>nkx3.2</i>, in zebrafish. These mutations caused zebrafish to become functionally jawless via fusion of the upper and lower jaw cartilages (ankylosis). Despite lacking jaw joints, <i>nkx3.2</i> mutants survived to adulthood and accommodated this defect by: a) remodeling their skulls; and b) altering their behavior from suction feeding to ram feeding. As a result, <i>nkx3.2</i> mutants developed skull shapes superficially similar to those observed in two lineages of ancient jawless vertebrates (anaspids and furcacaudiid thelodonts), including: a fixed open gape, reduced snout, and enlarged branchial region. However, no homology exists in individual skull elements between these taxa, and most of the modified elements in the mutant zebrafish occur outside known expression domains of <i>nkx3.2</i>. Therefore, we interpret the adult <i>nkx3.2</i> phenotype not as a reversal to an ancestral state, but as convergence due to similar functional requirements of feeding without moveable jaws. This remarkable convergence strongly suggests that jaw movements themselves dramatically influence the development of jawed vertebrate skulls. Thus, these mutants provide a unique model with which to: a) investigate adaptive responses to perturbation in skeletal development; b) re-evaluate evolutionarily inspired interpretations of phenocopies generated by gene knockdowns and knockouts; and c) gain insights into feeding mechanics of the extinct agnathans.
Data from: Head-turning morphologies: evolution of shape diversity in the mammalian atlas-axis complex
Mammals flex, extend, and rotate their spines as they perform behaviors critical for survival, such as foraging, consuming prey, locomoting, and interacting with conspecifics or predators. The atlas-axis complex is a mammalian innovation that allows precise head movements during these behaviors. While morphological variation in other vertebral regions has been linked to ecological differences in mammals, less is known about morphological specialization in the cervical vertebrae, which are developmentally constrained in number but highly variable in size and shape. Here, we present the first phylogenetic comparative study of the atlas-axis complex across mammals. We used spherical harmonics to quantify 3D shape variation of the atlas and axis across a diverse sample of species, and performed phylogenetic analyses to investigate if vertebral shape is associated with body size, locomotion, and diet. We found that differences in atlas and axis shape are partly explained by phylogeny, and that mammalian subclades differ in morphological disparity. Atlas and axis shape diversity is associated with differences in body size and locomotion; large terrestrial mammals have craniocaudally elongated vertebrae, while smaller mammals and aquatic mammals have more compressed vertebrae. These results provide a foundation for investigating functional hypotheses underlying the evolution of neck morphologies across mammals.
Data from: The role of bite force in the evolution of head shape and head shape dimorphism in Anolis lizards
1. Patterns of convergent evolution in head shape, combined with performance measures, provide ideal opportunities to understand the processes driving its evolution. Anole lizards represent an excellent subject to test this, as recurrent habitat specialists or ecomorphs evolved independently across different islands. 2. We show that phenotypic similarity corresponds to both phylogenetic similarity and similarity in habitat, indicating that there is convergent evolution in head shape among ecomorphs. Moreover, we show that the evolution of tall, wide heads correlates with the evolution of higher bite forces, driving head shape variation among and within ecomorphs. 3. In addition, the processes affecting head shape variation can differ between sexes, leading to sexual head shape dimorphism. These processes might, however, still depend on the habitat. Consequently, there could also be convergent evolution in head shape dimorphism among ecomorphs. 4. We found no evidence for convergent evolution in sexual head shape dimorphism. Moreover, the sexual head shape dimorphism correlates poorly with bite force, suggesting that intersexual head shape differences are related to other functions. Different processes are thus driving the evolution of head shape and head shape dimorphism.
Data from: Head shape modulates diversification of a classic cichlid pharyngeal jaw innovation
Functional innovations are often invoked to explain the uneven distribution of ecological diversity. Innovations may provide access to new adaptive zones by expanding available ecological opportunities and may serve as catalysts of adaptive radiation. However, diversity is often unevenly distributed within clades that share a key innovation, highlighting the possibility that the impact of the innovation is mediated by other traits. Pharyngognathy is a widely recognized innovation of the pharyngeal jaws that enhances the ability to process hard and tough prey in several major radiations of fishes, including marine wrasses and freshwater cichlids. We explored diversification of lower pharyngeal jaw shape, a key feature of pharyngognathy, and the extent to which it is influenced by head shape in Neotropical cichlids. While pharyngeal jaw shape was unaffected by either head length or head depth, its disparity declined dramatically with increasing head width. Head width also predicted the rate of pharyngeal jaw evolution such that higher rates were associated with narrow heads. Wide heads are associated with exploiting prey that require intense processing by pharyngeal jaws that have expanded surfaces for the attachment of enlarged muscles. However, we show that a wide head constrains access to adaptive peaks associated with several trophic roles. A constraint on the independent evolution of pharyngeal jaw and head shape may explain the uneven distribution of ecological diversity within a clade that shares a major functional innovation.
Data from: Covariation between human pelvis shape, stature, and head size alleviates the obstetric dilemma
Compared with other primates, childbirth is remarkably difficult in humans because the head of a human neonate is large relative to the birth-relevant dimensions of the maternal pelvis. It seems puzzling that females have not evolved wider pelvises despite the high maternal mortality and morbidity risk connected to childbirth. Despite this seeming lack of change in average pelvic morphology, we show that humans have evolved a complex link between pelvis shape, stature, and head circumference that was not recognized before. The identified covariance patterns contribute to ameliorate the "obstetric dilemma." Females with a large head, who are likely to give birth to neonates with a large head, possess birth canals that are shaped to better accommodate large-headed neonates. Short females with an increased risk of cephalopelvic mismatch possess a rounder inlet, which is beneficial for obstetrics. We suggest that these covariances have evolved by the strong correlational selection resulting from childbirth. Although males are not subject to obstetric selection, they also show part of these association patterns, indicating a genetic–developmental origin of integration.
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
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