scholarly journals The limits of convergence: the roles of phylogeny and dietary ecology in shaping non-avian amniote crania

2021 ◽  
Vol 8 (9) ◽  
pp. 202145
Author(s):  
Keegan M. Melstrom ◽  
Kenneth D. Angielczyk ◽  
Kathleen A. Ritterbush ◽  
Randall B. Irmis
Keyword(s):  
Functional Morphology ◽  
Feeding Ecology ◽  
Cranial Morphology ◽  
Skull Shape ◽  
Morphological Convergence ◽  
Morphometric Methods ◽  
Central Regions ◽  
Dietary Ecology ◽  
Amniote Phylogeny ◽  
Cranial Shape

Cranial morphology is remarkably varied in living amniotes and the diversity of shapes is thought to correspond with feeding ecology, a relationship repeatedly demonstrated at smaller phylogenetic scales, but one that remains untested across amniote phylogeny. Using a combination of morphometric methods, we investigate the links between phylogenetic relationships, diet and skull shape in an expansive dataset of extant toothed amniotes: mammals, lepidosaurs and crocodylians. We find that both phylogeny and dietary ecology have statistically significant effects on cranial shape. The three major clades largely partition morphospace with limited overlap. Dietary generalists often occupy clade-specific central regions of morphospace. Some parallel changes in cranial shape occur in clades with distinct evolutionary histories but similar diets. However, members of a given clade often present distinct cranial shape solutions for a given diet, and the vast majority of species retain the unique aspects of their ancestral skull plan, underscoring the limits of morphological convergence due to ecology in amniotes. These data demonstrate that certain cranial shapes may provide functional advantages suited to particular dietary ecologies, but accounting for both phylogenetic history and ecology can provide a more nuanced approach to inferring the ecology and functional morphology of cryptic or extinct amniotes.

Cranial morphology of the Loxommatidae (Amphibia: Labyrinthodontia)

1977 ◽  
Vol 280 (971) ◽  
pp. 29-101 ◽  
Keyword(s):  
Functional Morphology ◽  
Cranial Morphology ◽  
Additional Material ◽  
Jaw Muscles ◽  
Skull Shape ◽  
New Family ◽  
The Family ◽  
Basal Articulation ◽  
First Time ◽  
Jaw Musculature

The labyrinthodont superfamily Loxommatoidea is now divided into two families. The highly aberrant Spathicephalus is placed in a new family, the Spathicephalidae, to be described elsewhere. The family Loxommatidae is retained for the remaining genera, Loxomma, Megalocephalus and Baphetes . Additional material and further preparation has made possible a redescription of the three loxommatid genera and new skull restorations have been produced for most species. In particular the loxommatid braincase and palatoquadrate are reconstructed for the first time; in many features their structure is more primitive than that hitherto described for any temnospondyl. Since an intertemporal bone is found to be a feature of Baphetes as well as Loxomma , these two genera have been separated on the basis of skull shape and on stratigraphical grounds. A specimen from the Communis zone, Westphalian A, is attributed to Loxomma , as L. rankini sp.nov., while ‘ Loxomma bohemicum ’ has been transferred to the genus Baphetes as B. bohemicus (Fritsch). A further specimen, originally associated with Macrerpeton , has also been referred to this genus as B. lintonensis sp.nov. The skull of Megalocephalus pachycephalus can be described in greater detail than that of any other loxommatid species and thus forms the basis for discussion of the functional morphology. Jaw muscles are reconstructed for this species and it is concluded that the antorbital vacuity, which characterizes the Loxommatoidea, evolved as a bulging hole for a large pterygoideus muscle associated with a piscivorous habit and a kinetic inertial system of jaw closure. Consideration of the mechanics of jaw closure sheds light on a further enigma, i.e. the function of the basipterygoid articulation in the primitive temnospondyl skull. The loxommatid skull is considered divisible into two units. The presence of a specialized cranial joint between the quadrate and quadratojugal allows potential for any movement at the basal articulation to be accommodated in the main at this site. It is suggested that the system described for loxommatids represents an alternative design to the mobile cheek region of anthracosaurs and that the articulations represent zones of elasticity, which accommodate the stresses on the skull caused by a powerful jaw musculature.

scholarly journals Heterochronic Shifts Mediate Ecomorphological Convergence in Skull Shape of Microcephalic Sea Snakes

2019 ◽  
Vol 59 (3) ◽  
pp. 616-624 ◽  
Author(s):  
Emma Sherratt ◽  
Kate L Sanders ◽  
Amy Watson ◽  
Mark N Hutchinson ◽  
Michael S Y Lee ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Shape Variation ◽  
Micro Computed Tomography ◽  
Trophic Specialization ◽  
Evolutionary Patterns ◽  
Dietary Specialization ◽  
Geometric Morphometric ◽  
Sea Snakes ◽  
Morphometric Methods ◽  
Cranial Shape

Abstract Morphological variation among the viviparous sea snakes (Hydrophiinae), a clade of fully aquatic elapid snakes, includes an extreme “microcephalic” ecomorph that has a very small head atop a narrow forebody, while the hind body is much thicker (up to three times the forebody girth). Previous research has demonstrated that this morphology has evolved at least nine times as a consequence of dietary specialization on burrowing eels, and has also examined morphological changes to the vertebral column underlying this body shape. The question addressed in this study is what happens to the skull during this extreme evolutionary change? Here we use X-ray micro-computed tomography and geometric morphometric methods to characterize cranial shape variation in 30 species of sea snakes. We investigate ontogenetic and evolutionary patterns of cranial shape diversity to understand whether cranial shape is predicted by dietary specialization, and examine whether cranial shape of microcephalic species may be a result of heterochronic processes. We show that the diminutive cranial size of microcephalic species has a convergent shape that is correlated with trophic specialization to burrowing prey. Furthermore, their cranial shape is predictable for their size and very similar to that of juvenile individuals of closely related but non-microcephalic sea snakes. Our findings suggest that heterochronic changes (resulting in pedomorphosis) have driven cranial shape convergence in response to dietary specializations in sea snakes.

Constraint and adaptation in the evolution of carnivoran skull shape

Paleobiology ◽  
2011 ◽  
Vol 37 (3) ◽  
pp. 490-518 ◽  
Author(s):  
Borja Figueirido ◽  
Norman MacLeod ◽  
Jonathan Krieger ◽  
Miquel De Renzi ◽  
Juan Antonio Pérez-Claros ◽  
...  
Keyword(s):  
Morphological Plasticity ◽  
Shape Space ◽  
Cranial Morphology ◽  
Skull Morphology ◽  
Skull Shape ◽  
Olfactory Sense ◽  
History Of ◽  
Proximate Source ◽  
Brain Processing ◽  
Iterative Evolution

The evolutionary history of the Order Carnivora is marked by episodes of iterative evolution. Although this pattern is widely reported in different carnivoran families, the mechanisms driving the evolution of carnivoran skull morphology remain largely unexplored. In this study we use coordinate-point extended eigenshape analysis (CP-EES) to summarize aspects of skull shape in large fissiped carnivores. Results of these comparisons enable the evaluation of the role of different factors constraining the evolution of carnivoran skull design. Empirical morphospaces derived from mandible anatomy show that all hypercarnivores (i.e., those species with a diet that consists almost entirely of vertebrate flesh) share a set of traits involved in a functional compromise between bite force and gape angle, which is reflected in a strong pattern of morphological convergence. Although the paths followed by different taxa to reach this “hypercarnivore shape-space” differ because of phylogenetic constraints, the morphological signature of hypercarnivory in the mandible is remarkably narrow and well constrained. In contrast, CP-EES of cranial morphology does not reveal a similar pattern of shape convergence among hypercarnivores. This suggests a lesser degree of morphological plasticity in the cranium compared to the mandible, which probably results from a compromise between different functional demands in the cranium (e.g., feeding, vision, olfactory sense, and brain processing) whereas the mandible is only involved in food acquisition and processing. Combined analysis of theoretical and empirical morphospaces for these skull data also show the lower anatomical disparity of felids and hyaenids compared to canids and ursids. This indicates that increasing specialization within the hypercarnivorous niche may constrain subsequent morphological and ecological flexibility. During the Cenozoic, similar skull traits appeared in different carnivoran lineages, generated by similar selection pressures (e.g., toward hypercarnivory) and shared developmental pathways. These pathways were likely the proximate source of constraints on the degree of variation associated with carnivoran skull evolution and on its direction.

scholarly journals Ecomorphometric analysis of diversity in cranial shape of pygopodid geckos

2021 ◽  
Author(s):  
George P Gurgis ◽  
Juan D Daza ◽  
Ian G Brennan ◽  
Mark Hutchinson ◽  
Aaron M Bauer ◽  
...  
Keyword(s):  
Small Sample Size ◽  
Taxonomic Diversity ◽  
Small Sample ◽  
Cranial Morphology ◽  
Level Variation ◽  
Generic Level ◽  
Geometric Morphometric ◽  
Geometric Morphometric Analysis ◽  
Components Analysis ◽  
Cranial Shape

Abstract Pygopodids are elongate, functionally limbless geckos found throughout Australia. The clade presents low taxonomic diversity (∼45 spp.), but a variety of cranial morphologies, habitat use, and locomotor abilities that vary between and within genera. In order to assess potential relationships between cranial morphology and ecology, CT scans of 29 species were used for 3D geometric morphometric analysis. A combination of 24 static landmarks and 20 sliding semi-landmarks were subjected to Generalized Procrustes Alignment. Disparity in cranial shape was visualized through Principal Components Analysis, and a MANOVA was used to test for an association between shape, habitat, and diet. A subset of 27 species with well-resolved phylogenetic relationships was used to generate a phylomorphospace and conduct phylogeny-corrected MANOVA. Similar analyses were done solely on Aprasia taxa to explore species-level variation. Most of the variation across pygopodids was described by PC1 (54%: cranial roof width, parabasisphenoid and occipital length), PC2 (12%: snout elongation and braincase width), and PC3 (6%: elongation and shape of the palate and rostrum). Without phylogenetic correction, both habitat and diet were significant influencers of variation in cranial morphology. However, in the phylogeny-corrected MANOVA, habitat remained weakly significant, but not diet, which can be explained by generic-level differences in ecology rather than among species. Our results demonstrate that at higher levels, phylogeny has a strong effect on morphology, but that influence may be due to small sample size when comparing genera. However, because some closely related taxa occupy distant regions of morphospace, diverging diets and use of fossorial habitats may contribute to variation seen in these geckos.

scholarly journals Ecological correlates to cranial morphology in Leporids (Mammalia, Lagomorpha)

2014 ◽  
Author(s):  
Brian P Kraatz ◽  
Nicholas Bumacod ◽  
Emma Sherratt ◽  
Mathew J Wedel
Keyword(s):  
Cranial Morphology ◽  
Form And Function ◽  
Postcranial Morphology ◽  
Ecological Correlates ◽  
The Subject ◽  
And Function ◽  
The Relationship ◽  
Cranial Shape

The mammalian order Lagomorpha has been the subject of many morphometric studies aimed at understanding the relationship between form and function as it relates to locomotion, primarily in postcranial morphology. The leporid cranial skeleton, however, may also reveal information about their ecology, particularly locomotion and vision. Here we investigate the relationship between cranial shape and the degree of facial tilt with locomotion (cursoriality, saltation, and burrowing) within crown leporids. Our results suggest that facial tilt is more pronounced in cursors and saltators compared to generalists. However cranial shape does not differ significantly among these locomotor groups, nor does it differ significantly between species that burrow and those that do not.

scholarly journals Trophic divergence despite morphological convergence in a continental radiation of snakes

2014 ◽  
Vol 281 (1787) ◽  
pp. 20140413 ◽  
Author(s):  
Michael C. Grundler ◽  
Daniel L. Rabosky
Keyword(s):  
North America ◽  
Feeding Ecology ◽  
North American ◽  
Foraging Mode ◽  
Full Spectrum ◽  
Form And Function ◽  
The North ◽  
Biogeographic History ◽  
Morphological Convergence ◽  
Phenotypic Convergence

Ecological and phenotypic convergence is a potential outcome of adaptive radiation in response to ecological opportunity. However, a number of factors may limit convergence during evolutionary radiations, including interregional differences in biogeographic history and clade-specific constraints on form and function. Here, we demonstrate that a single clade of terrestrial snakes from Australia—the oxyuranine elapids—exhibits widespread morphological convergence with a phylogenetically diverse and distantly related assemblage of snakes from North America. Australian elapids have evolved nearly the full spectrum of phenotypic modalities that occurs among North American snakes. Much of the convergence appears to involve the recurrent evolution of stereotyped morphologies associated with foraging mode, locomotion and habitat use. By contrast, analysis of snake diets indicates striking divergence in feeding ecology between these faunas, partially reflecting regional differences in ecological allometry between Australia and North America. Widespread phenotypic convergence with the North American snake fauna coupled with divergence in feeding ecology are clear examples of how independent continental radiations may converge along some ecological axes yet differ profoundly along others.

scholarly journals Trophic convergence drives morphological convergence in marine tetrapods

2015 ◽  
Vol 11 (1) ◽  
pp. 20140709 ◽  
Author(s):  
Neil P. Kelley ◽  
Ryosuke Motani
Keyword(s):  
Feeding Ecology ◽  
Convergent Evolution ◽  
Ecological Niches ◽  
Trophic Groups ◽  
Functional Constraints ◽  
Tooth Morphology ◽  
Marine Life ◽  
Morphological Convergence ◽  
Dietary Data

Marine tetrapod clades (e.g. seals, whales) independently adapted to marine life through the Mesozoic and Caenozoic, and provide iconic examples of convergent evolution. Apparent morphological convergence is often explained as the result of adaptation to similar ecological niches. However, quantitative tests of this hypothesis are uncommon. We use dietary data to classify the feeding ecology of extant marine tetrapods and identify patterns in skull and tooth morphology that discriminate trophic groups across clades. Mapping these patterns onto phylogeny reveals coordinated evolutionary shifts in diet and morphology in different marine tetrapod lineages. Similarities in morphology between species with similar diets—even across large phylogenetic distances—are consistent with previous hypotheses that shared functional constraints drive convergent evolution in marine tetrapods.

Skull shape variation in extant and extinct Testudinata and its relation to habitat and feeding ecology

2016 ◽  
Vol 98 (3) ◽  
pp. 310-325 ◽  
Author(s):  
Christian Foth ◽  
Márton Rabi ◽  
Walter G. Joyce
Keyword(s):  
Feeding Ecology ◽  
Shape Variation ◽  
Skull Shape

scholarly journals Hominoid intraspecific cranial variation mirrors neutral genetic diversity

2018 ◽  
Vol 115 (45) ◽  
pp. 11501-11506 ◽  
Author(s):  
Julia M. Zichello ◽  
Karen L. Baab ◽  
Kieran P. McNulty ◽  
Christopher J. Raxworthy ◽  
Michael E. Steiper
Keyword(s):  
Genetic Diversity ◽  
Homo Sapiens ◽  
Population History ◽  
Cranial Morphology ◽  
Shape Variation ◽  
Evolutionary Processes ◽  
Cranial Variation ◽  
History Of ◽  
Fossil Hominin ◽  
Cranial Shape

Natural selection, developmental constraint, and plasticity have all been invoked as explanations for intraspecific cranial variation in humans and apes. However, global patterns of human cranial variation are congruent with patterns of genetic variation, demonstrating that population history has influenced cranial variation in humans. Here we show that this finding is not unique toHomo sapiensbut is also broadly evident across extant ape species. Specifically, taxa that exhibit greater intraspecific cranial shape variation also exhibit greater genetic diversity at neutral autosomal loci. Thus, cranial shape variation within hominoid taxa reflects the population history of each species. Our results suggest that neutral evolutionary processes such as mutation, gene flow, and genetic drift have played an important role in generating cranial variation within species. These findings are consistent with previous work on human cranial morphology and improve our understanding of the evolutionary processes that generate intraspecific cranial shape diversity within hominoids. This work has implications for the analysis of selective and developmental pressures on the cranium and for interpreting shape variation in fossil hominin crania.

scholarly journals Geometric morphometrics of mandibles for dietary differentiation of Bovidae (Mammalia: Artiodactyla)

2021 ◽  
Author(s):  
Bian Wang ◽  
Miriam Zelditch ◽  
Catherine Badgley
Keyword(s):  
Geometric Morphometrics ◽  
Functional Morphology ◽  
Feeding Ecology ◽  
Cross Validation ◽  
Correct Classification ◽  
Correct Classification Rate ◽  
Linear Measurements ◽  
Classification Rate ◽  
Geometric Morphometric ◽  
Morphometric Analyses

Abstract The mammalian family Bovidae has been widely studied in ecomorphological research, with important applications to paleoecological and paleohabitat reconstructions. Most studies of bovid craniomandibular features in relation to diet have used linear measurements. In this study, we conduct landmark-based geometric-morphometric analyses to evaluate whether different dietary groups can be distinguished by mandibular morphology. Our analysis includes data for 100 species of extant bovids, covering all bovid tribes and two dietary classifications. For the first classification with three feeding categories, we found that browsers (including frugivores), mixed feeders, and grazers are moderately well separated using mandibular shape. A finer dietary classification (frugivore, browser, browser-grazer intermediate, generalist, variable grazer, obligate grazer) proved to be more useful for differentiating dietary extremes (frugivores and obligate grazers) but performed equally or less well for other groups. Notably, frugivorous bovids, which belong in tribe Cephalophini, have a distinct mandibular shape that is readily distinguished from all other dietary groups, yielding a 100% correct classification rate from jackknife cross-validation. The main differences in mandibular shape found among dietary groups are related to the functional needs of species during forage prehension and mastication. Compared to browsers, both frugivores and grazers have mandibles that are adapted for higher biomechanical demand of chewing. Additionally, frugivore mandibles are adapted for selective cropping. Our results call for more work on the feeding ecology and functional morphology of frugivores and offer an approach for reconstructing the diet of extinct bovids.

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