Contributions to the functional morphology of caudate skulls: kinetic and akinetic forms

Natchev, Nikolay; Handschuh, Stephan; Lukanov, Simeon; Tzankov, Nikolay; Naumov, Borislav; Werneburg, Ingmar

doi:10.7717/peerj.2392

Cited by 10 publications

(15 citation statements)

References 32 publications

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“…Kinesis of the skull not only refers to mobile joints between bones, but cranial kinesis can also be developed in skulls with immobile sutures by having relatively thin and elastic bones in gracile crania that eventually enable the same range of motion 21 . Cranial kinesis of tuatara is highly disputed.…”

Section: Discussionmentioning

confidence: 99%

Unique skull network complexity of Tyrannosaurus rex among land vertebrates

Werneburg

Esteve‐Altava

Bruno

et al. 2019

Sci Rep

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Like other diapsids, Tyrannosaurus rex has two openings in the temporal skull region. In addition, like in other dinosaurs, its snout and lower jaw show large cranial fenestrae. In T. rex, they are thought to decrease skull weight, because, unlike most other amniotes, the skull proportion is immense compared to the body. Understanding morphofunctional complexity of this impressive skull architecture requires a broad scale phylogenetic comparison with skull types different to that of dinosaurs with fundamentally diverging cranial regionalization. Extant fully terrestrial vertebrates (amniotes) provide the best opportunities in that regard, as their skull performance is known from life. We apply for the first time anatomical network analysis to study skull bone integration and modular constructions in tyrannosaur and compare it with five representatives of the major amniote groups in order to get an understanding of the general patterns of amniote skull modularity. Our results reveal that the tyrannosaur has the most modular skull organization among the amniotes included in our study, with an unexpected separation of the snout in upper and lower sub-modules and the presence of a lower adductor chamber module. Independent pathways of bone reduction in opossum and chicken resulted in different degrees of cranial complexity with chicken having a typical sauropsidian pattern. The akinetic skull of opossum, alligator, and leatherback turtle evolved in independent ways mirrored in different patterns of skull modularity. Kinetic forms also show great diversity in modularity. The complex tyrannosaur skull modularity likely represents a refined mosaic of phylogenetic and ecological factors with food processing being probably most important for shaping its skull architecture. Mode of food processing primarily shaped skull integration among amniotes, however, phylogenetic patterns of skull integration are low in our sampling. Our general conclusions on amniote skull integrity are obviously preliminary and should be tested in subsequent studies. As such, this study provides a framework for future research focusing on the evolution of modularity on lower taxonomic levels.

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Section: Discussionmentioning

confidence: 99%

Unique skull network complexity of Tyrannosaurus rex among land vertebrates

Werneburg

Esteve‐Altava

Bruno

et al. 2019

Sci Rep

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“…True salamanders, which after metamorphosis have an exclusively terrestrial feeding mode, possess a gracile skull architecture with thin but firmly fused bones of the skull roof (Natchev et al. ). The well‐ossified skull with a complete frontosquamosal arch as in spectacled salamanders and knobby, New World and Asian newts is also largely akinetic.…”

Section: Discussionmentioning

confidence: 99%

“…However, in Triturus ivanbureschi , a species with a partially reduced frontosquamosal arch, various types of skull kinetics, including a movable connection among the skull roof elements, were recently reported (Natchev et al. ). Therefore, the changes in the morphology of the frontosquamosal arch in the Pleurodelinae could be related to skull kinetics and be regarded as an independently acquired adaptation related to various feeding performances (Deban & Wake, ; Wake & Deban, ; Heiss & De Vylder, ).…”

Section: Discussionmentioning

confidence: 99%

“…In salamanders, the cranial skeleton undergoes significant changes in morphology during ontogeny, including changes from a highly kinetic cranial skeleton of larvae (which have suction feeding mode) to the largely akinetic cranial skeleton in adults (Marconi & Simonetta, 1988). True salamanders, which after metamorphosis have an exclusively terrestrial feeding mode, possess a Log centroid size gracile skull architecture with thin but firmly fused bones of the skull roof (Natchev et al 2016). The wellossified skull with a complete frontosquamosal arch as in spectacled salamanders and knobby, New World and Asian newts is also largely akinetic.…”

Section: Discussionmentioning

confidence: 99%

“…Such a robust skull morphology occurs in the predominantly aquatic Pachytriton brevipes, as well as in semi-aquatic or more terrestrial newt species such as N. viridescens and Tylototriton verrucosus. However, in Triturus ivanbureschi, a species with a partially reduced frontosquamosal arch, various types of skull kinetics, including a movable connection among the skull roof elements, were recently reported (Natchev et al 2016). Therefore, the changes in the morphology of the frontosquamosal arch in the Pleurodelinae could be related to skull kinetics and be regarded as an independently acquired adaptation related to various feeding performances Heiss & De Vylder, 2016).…”

Section: Discussionmentioning

confidence: 99%

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Evolution of skull shape in the family Salamandridae (Amphibia: Caudata)

Ivanović

Arntzen

2017

Journal of Anatomy

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We carried out a comparative morphometric analysis of 56 species of salamandrid salamanders, representing 19 out of 21 extant genera, with the aim of uncovering the major patterns of skull shape diversification, and revealing possible trends and directions of evolutionary change. To do this we used micro-computed tomography scanning and three-dimensional geometric morphometrics, along with a well-resolved molecular phylogeny. We found that allometry explains a relatively small amount of shape variation across taxa. Congeneric species of salamandrid salamanders are more similar to each other and cluster together producing distinct groups in morphospace. We detected a strong phylogenetic signal and little homoplasy. The most pronounced changes in the skull shape are related to the changes of the frontosquamosal arch, a unique feature of the cranial skeleton for the family Salamandridae, which is formed by processes arising from the frontal and squamosal bones that arch over the orbits. By mapping character states over the phylogeny, we found that a reduction of the frontosquamosal arch occurs independently in three lineages of the subfamily Pleurodelinae. This reduction can probably be attributed to changes in the development and ossification rates of the frontosquamosal arch. In general, our results are similar to those obtained for caecilian amphibians, with an early expansion into the available morphospace and a complex history characterizing evolution of skull shape in both groups. To evaluate the specificity of the inferred evolutionary trajectories and Caudata-wide trends in the diversity of skull morphology, information from additional groups of tailed amphibians is needed.

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Evolution of the temporal skull openings in land vertebrates: A hypothetical framework on the basis of biomechanics

Werneburg,

Preuschoft

2024

The Anatomical Record

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The complex constructions of land vertebrate skulls have inspired a number of functional analyses. In the present study, we provide a basic view on skull biomechanics and offer a framework for more general observations using advanced modeling approaches in the future. We concentrate our discussion on the cranial openings in the temporal skull region and work out two major, feeding‐related factors that largely influence the shape of the skull. We argue that (1) the place where the most forceful biting is conducted and (2) the handling of resisting food (sideward movements) constitute the formation and shaping of either one or two temporal arcades surrounding these openings. Diversity in temporal skull anatomy among amniotes can be explained by specific modulations of these factors with different amounts of acting forces which inevitably lead to deposition or reduction of bone material. For example, forceful anterior bite favors an infratemporal bar, whereas forceful posterior bite favors formation of an upper temporal arcade. Transverse forces (inertia and resistance of seized objects) as well as neck posture also influence the shaping of the temporal region. Considering their individual skull morphotypes, we finally provide hypotheses on the feeding adaptation in a variety of major tetrapod groups. We did not consider ligaments, internal bone structure, or cranial kinesis in our considerations. Involving those in quantitative tests of our hypotheses, such as finite element system synthesis, will provide a comprehensive picture on cranial mechanics and evolution in the future.

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Contributions to the functional morphology of caudate skulls: kinetic and akinetic forms

Cited by 10 publications

References 32 publications

Unique skull network complexity of Tyrannosaurus rex among land vertebrates

Unique skull network complexity of Tyrannosaurus rex among land vertebrates

Evolution of skull shape in the family Salamandridae (Amphibia: Caudata)

Evolution of the temporal skull openings in land vertebrates: A hypothetical framework on the basis of biomechanics

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