scholarly journals Sex‐specific ontogenetic patterns of cranial morphology, theoretical bite force, and underlying jaw musculature in fishers and American martens

2020 ◽  
Vol 237 (4) ◽  
pp. 727-740
Author(s):  
Chris J. Law
Keyword(s):  
Bite Force ◽  
Cranial Morphology ◽  
Jaw Musculature ◽  
American Martens

Ontogenetic scaling of cranial morphology and bite-force generation in the loggerhead musk turtle

2009 ◽  
Vol 280 (3) ◽  
pp. 280-289 ◽  
Author(s):  
J. B. Pfaller ◽  
N. D. Herrera ◽  
P. M. Gignac ◽  
G. M. Erickson
Keyword(s):  
Bite Force ◽  
Force Generation ◽  
Cranial Morphology

Cranial kinesis in geckoes: functional implications

2000 ◽  
Vol 203 (9) ◽  
pp. 1415-1423 ◽  
Author(s):  
A. Herrel ◽  
P. Aerts ◽  
F. De Vree
Keyword(s):  
Bite Force ◽  
Power Stroke ◽  
Factors Associated ◽  
Jaw Opening ◽  
Joint Forces ◽  
Kinetic System ◽  
Functional Implications ◽  
Cranial Kinesis ◽  
Negative Factors ◽  
Jaw Musculature

Although it is generally assumed that cranial kinesis is a plesiomorphic characteristic in squamates, experimental data tend to contradict this hypothesis. In particular, coupled kinesis (i.e. streptostyly and mesokinesis) presumably arose independently in only a limited number of highly specialised groups. In this study, we investigated cranial kinesis in one of the most specialised of these groups: geckoes. On the basis of cineradiographic and electromyographic data, the fast opening and the slow closing/power stroke phases were modelled to elucidate possible functions of the observed kinesis. The results of these analyses show that the retraction of the muzzle unit during crushing is a self-reinforcing system that increases bite force and reduces the joint forces; the active protraction of the kinetic system during jaw opening, in contrast, enhances opening speed through the coupling of the intracranial units. It can be argued that cranial kinesis in geckoes is probably not an adaptive trait as such but, instead, a consequence of the ‘Bauplan’ of the cranial system in these animals. Presumably as a result of constructional constraints on the size of the jaw musculature and eyes, the supratemporal and postorbital bars were lost, which resulted in enormous mobility in the skull. To counteract the potential negative factors associated with this (decrease in bite force, skull damage), the kinetic system may have become coupled, and thus functional.

Cranial morphology and bite force in Chamaeleolis lizards – Adaptations to molluscivory?

Zoology ◽  
2008 ◽  
Vol 111 (6) ◽  
pp. 467-475 ◽  
Author(s):  
Anthony Herrel ◽  
Veronika Holanova
Keyword(s):  
Bite Force ◽  
Cranial Morphology

Functional analysis of sabertooth cranial morphology

Paleobiology ◽  
1980 ◽  
Vol 6 (3) ◽  
pp. 295-312 ◽  
Author(s):  
Sharon B. Emerson ◽  
Leonard Radinsky
Keyword(s):  
Functional Analysis ◽  
Functional Significance ◽  
Bite Force ◽  
Cranial Morphology ◽  
Biomechanical Models ◽  
Morphological Differences

Elongate canines evolved independently at least four times among mammalian carnivores, and each time skulls were modified in similar ways. We have compared the cranial morphology of sabertooths to that of their non-sabertoothed relatives, living and extinct, and applied simple biomechanical models to elucidate the functional significance of the morphological differences. Our analysis suggests that (1) sabertooth morphology represents modification for wider gape with retention of a powerful bite force at the carnassial; (2) sabertooths probably used a throat or ventral neck slash to kill prey; and (3) elongate canines and retractile claws may have facilitated the exploitation of relatively larger prey by sabertooths compared to non-sabertooth carnivores.

Bite force, diet, and cranial morphology of fossil hominids

1988 ◽  
Vol 17 (7) ◽  
pp. 657-670 ◽  
Author(s):  
Brigitte Demes ◽  
Norman Creel
Keyword(s):  
Bite Force ◽  
Cranial Morphology ◽  
Fossil Hominids

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.

Additional Dermal Ossifications in the Anuran Skull: Morphological Novelties or Archaic Elements?

2011 ◽  
Vol 4 (1) ◽  
pp. 17-27 ◽  
Author(s):  
Sergei V. Smirnov
Keyword(s):  
Common Ancestor ◽  
The State ◽  
Cranial Morphology ◽  
Anterior Portion ◽  
Bombina Orientalis ◽  
Common Event ◽  
Rostral Portion ◽  
Morphological Novelties ◽  
Dermal Bones

Examination of the cranial morphology in Bombina orientalis (Anura: Discoglossidae) revealed the occurrence of additional dermal bones lying: a) between the nasals and frontoparietals, b) between frontoparietals, and c) on the tectum synoticum behind the frontoparietals. The presence of similar bones as well as extra ossifications lying in the midline in the rostral portion of skull was shown to be a rather common event among anurans. Based on the occurrence of bones with similar topology in crossopterygians and different stegocephalians, it was concluded that extra ossifications sporadically appearing in anurans are more likely to be ancient cranial elements than neomorphs. Additional dermal bones found in the anterior portion of the anuran skull are homologous to the postrostrals of crossopterygians; extra ossifications lying between the frontoparietals correspond to the bones with similar topology sporadically appearing in crossopterygians and stegocephalians; and extra bones situated behind the frontoparietals are homologous to the lateral extrascapulars (postparietals of stegocephalians) and the median extrascapular of crossopterygians. These extra bones were proposed to be inherited from the presumed common ancestor of all Gnathostomes and retained in anurans in the state of latent capacities. The sporadic appearance of these bones in anurans results from the phenotypical realization of these latent capacities.

From Phenotype to Genotype And Back Again

2019 ◽  
Author(s):  
J. Richtsmeier ◽  
K.M. Lesciotto
Keyword(s):  
Human Evolution ◽  
Evolutionary Change ◽  
Cranial Morphology ◽  
Phenotypic Trait ◽  
Critical Feature ◽  
Developmental Mechanism ◽  
Experimental Approaches ◽  
Physical Forces ◽  
Collaborative Efforts ◽  
Current Emphasis

Traditionally, anthropologists study evolutionary change throughmorphological analysis of fossils and comparative primate data. For the analysis of the genotypephenotype continuum, the current emphasis on genes is misplaced because genes don’t make structure. Developmental processes make structure through the activity of cells that use instructions specified by genes. A critical mechanism underlying any phenotypic trait is the genetically guided change in developmental events that produce the trait. But even when a developmental mechanism is identified, the links between genetically guided instructions and phenotypic outcome are lengthy, complicated, flexible, and sensitive to physical forces of functioning organs. We use the study of craniofacial phenotypes of craniosynostosis (premature closure of sutures) to demonstrate how patterns produced by the covariation of cranial traits cannot always reveal mechanism. Next we turn to encephalization, a critical feature of human evolution that covaries with cranial phenotypes, and show how experimental approaches can be used to analyze mechanism underlying this well-documented pattern in human evolution. With the realization that no single line of evidence can explain the dramatic changes in cranial morphology that characterize human evolution come fundamental changes in the way we conduct anthropological inquiry - collaborative efforts from scientists with diverse expertise will continue to push the field forward.

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