scholarly journals Crocodylomorph cranial shape evolution and its relationship with body size and ecology

2019 ◽  
Author(s):  
Pedro L. Godoy
Keyword(s):  
Body Size ◽  
Cranial Morphology ◽  
Shape Evolution ◽  
Shape Variation ◽  
Crown Group ◽  
Early Peak ◽  
Group Members ◽  
Phylogenetic Hypotheses ◽  
And Shifts ◽  
Cranial Shape

AbstractCrocodylomorpha, which includes living crocodylians and their extinct relatives, has a rich fossil record, extending back for more than 200 million years. Unlike modern semi-aquatic crocodylians, extinct crocodylomorphs exhibited more varied lifestyles, ranging from marine to fully terrestrial forms. This ecological diversity was mirrored by a remarkable morphological disparity, particularly in terms of cranial morphology, which seems to be closely associated with ecological roles in the group. Here, I use geometric morphometrics to comprehensively investigate cranial shape variation and disparity in Crocodylomorpha. I quantitatively assess the relationship between cranial shape and ecology (i.e. terrestrial, aquatic, and semi-aquatic lifestyles), as well as possible allometric shape changes. I also characterise patterns of cranial shape evolution and identify regime shifts. I found a strong link between shape and size, and a significant influence of ecology on the observed shape variation. Terrestrial taxa, particularly notosuchians, have significantly higher disparity, and shifts to more longirostrine regimes are associated with large-bodied aquatic or semi-aquatic species. This demonstrates an intricate relationship between cranial shape, body size and lifestyle in crocodylomorph evolutionary history. Additionally, disparity-through-time analyses were highly sensitive to different phylogenetic hypotheses, suggesting the description of overall patterns among distinct trees. For crocodylomorphs, most results agree in an early peak during the Early Jurassic and another in the middle of the Cretaceous, followed by nearly continuous decline until today. Since only crown-group members survived through the Cenozoic, this decrease in disparity was likely the result of habitat loss, which narrowed down the range of crocodylomorph lifestyles.

scholarly journals Evolutionary morphology of the rabbit skull

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2453 ◽  
Author(s):  
Brian Kraatz ◽  
Emma Sherratt
Keyword(s):  
Small Proportion ◽  
Phylogenetic Signal ◽  
Morphological Data ◽  
Shape Variation ◽  
Evolutionary Morphology ◽  
Crown Group ◽  
Size Change ◽  
Generalist Species ◽  
Facial Region ◽  
Cranial Shape

The skull of leporids (rabbits and hares) is highly transformed, typified by pronounced arching of the dorsal skull and ventral flexion of the facial region (i.e., facial tilt). Previous studies show that locomotor behavior influences aspects of cranial shape in leporids, and here we use an extensive 3D geometric morphometrics dataset to further explore what influences leporid cranial diversity. Facial tilt angle, a trait that strongly correlates with locomotor mode, significantly predicts the cranial shape variation captured by the primary axis of cranial shape space, and describes a small proportion (13.2%) of overall cranial shape variation in the clade. However, locomotor mode does not correlate with overall cranial shape variation in the clade, because there are two district morphologies of generalist species, and saltators and cursorial species have similar morphologies. Cranial shape changes due to phyletic size change (evolutionary allometry) also describes a small proportion (12.5%) of cranial shape variation in the clade, but this is largely driven by the smallest living leporid, the pygmy rabbit (Brachylagus idahoensis). By integrating phylogenetic history with our geometric morphometric data, we show that the leporid cranium exhibits weak phylogenetic signal and substantial homoplasy. Though these results make it difficult to reconstruct what the ‘ancestral’ leporid skull looked like, the fossil records suggest that dorsal arching and facial tilt could have occurred before the origin of the crown group. Lastly, our study highlights the diversity of cranial variation in crown leporids, and highlights a need for additional phylogenetic work that includes stem (fossil) leporids and includes morphological data that captures the transformed morphology of rabbits and hares.

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 A Total-Evidence Dated Phylogeny of Echinoids and the Evolution of Body Size across Adaptive Landscape

2020 ◽  
Author(s):  
Nicolás Mongiardino Koch ◽  
Jeffrey R. Thompson
Keyword(s):  
Body Size ◽  
Large Scale ◽  
Sea Urchins ◽  
Phylogenetic Signal ◽  
Total Evidence ◽  
Adaptive Landscape ◽  
Crown Group ◽  
Evolutionary Forces ◽  
Phylogenetic Hypotheses ◽  
Dated Phylogeny

AbstractSeveral unique properties of echinoids (sea urchins) make them useful for exploring macroevolutionary dynamics, including their remarkable fossil record that can be incorporated into explicit phylogenetic hypotheses. However, this potential cannot be exploited without a robust resolution of the echinoid tree of life. We revisit the phylogeny of crown group Echinoidea using both the largest phylogenomic dataset compiled for the clade, as well as a large-scale morphological matrix with a dense fossil sampling. We also gather a new compendium of both tip and node age constraints, allowing us to combine phylogenomic, morphological and stratigraphic data using a total-evidence dating approach. For this, we develop a novel method for subsampling phylogenomic datasets that selects loci with high phylogenetic signal, low systematic biases and enhanced clock-like behavior. Our approach restructure much of the higher-level phylogeny of echinoids, and demonstrates that combining different data sources increases topological accuracy. We are able to resolve multiple alleged conflicts between molecular and morphological datasets, such as the position of Echinothurioida and Echinoneoida, as well as unravelling the relationships between sand dollars and their closest relatives. We then use this topology to trace the evolutionary history of echinoid body size through more than 270 million years, revealing a complex pattern of convergent evolution to stable peaks in macroevolutionary adaptive landscape. Our efforts show how combining phylogenomic and paleontological evidence offers new ways of exploring evolutionary forces operating across deep timescales.

scholarly journals Inter- and intraspecific variation in the Artibeus species complex demonstrates size and shape partitioning among species

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11777
Author(s):  
Brandon P. Hedrick
Keyword(s):  
Species Complex ◽  
Niche Partitioning ◽  
Fruit Size ◽  
Interspecific Variation ◽  
Cranial Morphology ◽  
Foraging Strategies ◽  
Shape Variation ◽  
Size And Shape ◽  
Ecological Resources ◽  
Artibeus Lituratus

Neotropical leaf-nosed bats (family Phyllostomidae) are one of the most diverse mammalian families and Artibeus spp. is one of the most speciose phyllostomid genera. In spite of their species diversity, previous work on Artibeus crania using linear morphometrics has uncovered limited interspecific variation. This dearth of shape variation suggests that differences in cranial morphology are not contributing to niche partitioning across species, many of which are often found in sympatry. Using two-dimensional geometric morphometric methods on crania from eleven species from the Artibeus species complex, the current study demonstrates substantial cranial interspecific variation, sexual size and shape dimorphism, and intraspecific geographic variation. The majority of species were shown to have a unique size and shape, which suggests that each species may be taking advantage of slightly different ecological resources. Further, both sexual size and shape dimorphism were significant in the Artibeus species complex. Male and female Artibeus are known to have sex specific foraging strategies, with males eating near their roosts and females feeding further from their roosts. The presence of cranial sexual dimorphism in the Artibeus species complex, combined with previous work showing that different fruit size and hardness is correlated with different cranial shapes in phyllostomids, indicates that the males and females may be utilizing different food resources, leading to divergent cranial morphotypes. Additional field studies will be required to confirm this emergent hypothesis. Finally, significant geographical shape variation was found in a large intraspecific sample of Artibeus lituratus crania. However, this variation was not correlated with latitude and instead may be linked to local environmental factors. Additional work on ecology and behavior in the Artibeus species complex underlying the morphological variation uncovered in this study will allow for a better understanding of how the group has reached its present diversity.

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.

scholarly journals The impact of allometry on vomer shape and its implications for the taxonomy and cranial kinesis of crown-group birds

2020 ◽  
Author(s):  
Olivia Plateau ◽  
Christian Foth
Keyword(s):  
Anterior Part ◽  
Correct Identification ◽  
Temporal Region ◽  
Shape Variation ◽  
Crown Group ◽  
Multivariate Statistical ◽  
Morphological Differences ◽  
Cranial Kinesis ◽  
The Impact ◽  
Shape Data

AbstractCrown birds are subdivided into two main groups, Palaeognathae and Neognathae, that can be distinguished, among others, by the organization of the bones in their pterygoid-palatine complex (PPC). Shape variation to the vomer, which is the most anterior part of the PPC, was recently analysed by Hu et al. (2019) with help of geometric morphometrics to discover morphological differences between palaeognath and neognath birds. Based on this study, the vomer was identified as sufficient to distinguish the two main groups (and even more inclusive neognath groups) and their cranial kinetic system. As there are notable size differences between the skulls of palaeognaths and neognaths, we here investigate the impact of allometry on vomeral shape and its implication for taxonomic classification by re-analysing the data of the previous study. Different types of multivariate statistical analyses reveal that taxonomic identification based on vomeral shape is strongly impaired by allometry, as the error of correct identification is high when shape data is corrected for size. This finding is evident by a great overlap between palaeognath and neognath subclades in morphospace. The correct identification is further influenced by the convergent presence of a flattened vomeral morphotype in multiple neognath subclades. As the evolution of cranial kinesis has been linked to vomeral shape in the original study, the existing correlation between shape and size of the vomer across different bird groups found in the present study questions this conclusion. In fact, cranial kinesis in crown birds results from the loss of the jugal-postorbital bar in the temporal region and ectopterygoid in the PPC and the combination of a mobilized quadrate-zygomatic arch complex and a flexible PPC. Therefore, we can conclude that the vomer itself is not a suitable proxy for exploring the evolution of cranial kinesis in crown birds and their ancestors.

Long-term declines in body size and shifts in run timing of Atlantic salmon in Ireland

2006 ◽  
Vol 68 (6) ◽  
pp. 1713-1730 ◽  
Author(s):  
T. P. Quinn ◽  
P. McGinnity ◽  
T. F. Cross
Keyword(s):  
Body Size ◽  
Atlantic Salmon ◽  
And Shifts ◽  
Run Timing
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