Adaptive problems and possibilities in the temporal fenestration of tetrapod skulls

Frazzetta, T. H.

doi:10.1002/jmor.1051250203

Cited by 55 publications

(67 citation statements)

References 10 publications

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“…The skull provides a structure for jaw and neck muscle attachment and should be rigid enough to withstand the forces these muscles apply, along with accompanying feeding and other forces [6]–[8]. Exactly how the skull responds to these forces in tandem with accommodating the brain and sense organs is not fully understood.…”

Section: Introductionmentioning

confidence: 99%

Functional Relationship between Skull Form and Feeding Mechanics in Sphenodon, and Implications for Diapsid Skull Development

et al. 2011

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The vertebrate skull evolved to protect the brain and sense organs, but with the appearance of jaws and associated forces there was a remarkable structural diversification. This suggests that the evolution of skull form may be linked to these forces, but an important area of debate is whether bone in the skull is minimised with respect to these forces, or whether skulls are mechanically “over-designed” and constrained by phylogeny and development. Mechanical analysis of diapsid reptile skulls could shed light on this longstanding debate. Compared to those of mammals, the skulls of many extant and extinct diapsids comprise an open framework of fenestrae (window-like openings) separated by bony struts (e.g., lizards, tuatara, dinosaurs and crocodiles), a cranial form thought to be strongly linked to feeding forces. We investigated this link by utilising the powerful engineering approach of multibody dynamics analysis to predict the physiological forces acting on the skull of the diapsid reptile Sphenodon. We then ran a series of structural finite element analyses to assess the correlation between bone strain and skull form. With comprehensive loading we found that the distribution of peak von Mises strains was particularly uniform throughout the skull, although specific regions were dominated by tensile strains while others were dominated by compressive strains. Our analyses suggest that the frame-like skulls of diapsid reptiles are probably optimally formed (mechanically ideal: sufficient strength with the minimal amount of bone) with respect to functional forces; they are efficient in terms of having minimal bone volume, minimal weight, and also minimal energy demands in maintenance.

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Section: Introductionmentioning

confidence: 99%

Functional Relationship between Skull Form and Feeding Mechanics in Sphenodon, and Implications for Diapsid Skull Development

et al. 2011

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“…The presence or absence of the lower temporal arch, which ventrally bounds the lower temporal fossa and is formed by a contact between jugal and quadratojugal, was usually treated as very important by systematists in the past (Frazzetta 1968;Rieppel and Gronowski 1981). The loss of the arch was formerly regarded as unique for squamates and, therefore, many early diapsids, e.g.…”

Section: Introductionmentioning

confidence: 99%

Early loss and multiple return of the lower temporal arcade in diapsid reptiles

Müller

2003

Naturwissenschaften

101

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The temporal arches of diapsid reptiles have received attention for several decades. In particular, it has been observed that the lower temporal bar at the ventral margin of the cheek is frequently reduced due to the absence of a contact between jugal and quadratojugal. The loss of the arcade was formerly considered to be of high systematic value, but is now often interpreted as being autapomorphic for the respective taxon, and the presence of both arcades is generally regarded as a plesiomorphic feature. Here I show, based on a cladistic analysis as well as on further anatomical evidence, that the lower temporal arcade was lost only once in diapsid evolution, and that the presence of the arch in "higher" diapsids is secondary, which is indicated by the different ratio between jugal and quadratojugal as well as by ontogeny. This result also sheds new light on the understanding of the cheek configuration of enigmatic taxa such as ichthyosaurs and turtles.

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“…The positive allometries of the bones of the lower adductor chamber of B. elegans , therefore, may reflect greater resistance for a more robust musculature of m. adductor mandibulae internus and m. adductor mandibulae posterior in response to higher forces created by external adductors. Besides, these muscles also play the main role in feeding, as proposed for aquatic feeders (Frazzetta, 1968; Werneburg, 2012), in addition to a larger area between the two tips of the maxilla (i.e., SMX a = 0.70) and a flattened skull.…”

Section: Discussionmentioning

confidence: 93%

“…9B), which originate at the quadrate, prootic, pterygoid, palatine, postorbital and the descending process of the parietal (Schumacher, 1973; Werneburg, 2011), are important during the jaw-closure phase. The importance of these muscles has been debated for early tetrapods with flat skull and aquatic lifestyle (e.g., Temnospondyli and Lepospondyli; Frazzetta, 1968), in which the internal muscle might have assumed the main function of closing the jaw (Werneburg, 2012). This also occurs in turtles with flat skulls and with poorly developed crista supraoccipitalis (e.g., Chelidae; Werneburg, 2011; Werneburg, 2012).…”

Section: Discussionmentioning

confidence: 99%

Intra-specific variation and allometry of the skull of Late Cretaceous side-necked turtleBauruemys elegans(Pleurodira, Podocnemididae) and how to deal with morphometric data in fossil vertebrates

Mariani

Romano

2017

PeerJ

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BackgroundPrevious quantitative studies on Bauruemys elegans (Suárez, 1969) shell variation, as well as the taphonomic interpretation of its type locality, have suggested that all specimens collected in this locality may have belonged to the same population. We rely on this hypothesis in a morphometric study of the skull. Also, we tentatively assessed the eating preference habits differentiation that might be explained as due to ontogenetic changes.MethodsWe carried out an ANOVA testing 29 linear measurements from 21 skulls of B. elegans taken by using a caliper and through images, using the ImageJ software. First, a Principal Components Analysis (PCA) was performed with 27 measurements (excluding total length and width characters; =raw data) in order to visualize the scatter plots based on the form variance only. Then, a second PCA was carried out using ratios of length and width of each original measurement to assess shape variation among individuals. Finally, original measurements were log-transformed to describe allometries over ontogeny.ResultsNo statistical differences were found between caliper and ImageJ measurements. The first three PCs of the PCA with raw data comprised 70.2% of the variance. PC1 was related to size variation and all others related to shape variation. Two specimens plotted outside the 95% ellipse in PC1∼PC2 axes. The first three PCs of the PCA with ratios comprised 64% of the variance. When considering PC1∼PC2, all specimens plotted inside the 95% ellipse. In allometric analysis, five measurements were positively allometric, 19 were negatively allometric and three represented enantiometric allometry. Many bones of the posterior and the lateral emarginations lengthen due to increasing size, while jugal and the quadratojugal decrease in width.DiscussionImageJ is useful in replacing caliper since there was no statistical differences. Yet iterative imputation is more appropriate to deal with missing data in PCA. Some specimens show small differences in form and shape. Form differences were interpreted as occuring due to ontogeny, whereas shape differences are related to feeding changes during growth. Moreover, all outlier specimens are crushed and/or distorted, thus the form/shape differences may be partially due to taphonomy. The allometric lengthening of the parietal, quadrate, squamosal, maxilla, associated with the narrowing of jugal and quadratojugal may be related to changes in feeding habit between different stages of development. This change in shape might represent a progressive skull stretching and enlargement of posterior and lateral emargination during ontogeny, and consequently, the increment of the feeding-apparatus musculature. Smaller individuals may have fed on softer diet, whereas larger ones probably have had a harder diet, as seen in some living species of Podocnemis. We conclude that the skull variation might be related to differences in feeding habits over ontogeny in B. elegans.

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Adaptive problems and possibilities in the temporal fenestration of tetrapod skulls

Cited by 55 publications

References 10 publications

Functional Relationship between Skull Form and Feeding Mechanics in Sphenodon, and Implications for Diapsid Skull Development

Functional Relationship between Skull Form and Feeding Mechanics in Sphenodon, and Implications for Diapsid Skull Development

Early loss and multiple return of the lower temporal arcade in diapsid reptiles

Intra-specific variation and allometry of the skull of Late Cretaceous side-necked turtleBauruemys elegans(Pleurodira, Podocnemididae) and how to deal with morphometric data in fossil vertebrates

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