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Fig. 5 in Differentiation of skull morphology and cranial kinesis in common toads

Fig. 5 The first and second principal components of average skull shape of 49 toad species. The shape changes are summarised by wireframe graphs along the axes. Recognised clades are the Atelopodina

Fig. 2 in Differentiation of skull morphology and cranial kinesis in common toads

Fig. 2 Variation in the degree of ossification of the parasphenoid and prootic in common toads. The arrows indicate the adjacent cranial bones for which character states ('connected' or 'unconnected') were scored as follows: prootic to exoccipital (P-E), prootic to squamosal (P-Sq), sphenethmoid to parasphenoid (Sp-Ps), sphenethmoid to palatine (Sp-Pa) and exoccipital to parasphenoid (E-Ps)

Fig. 4 in Differentiation of skull morphology and cranial kinesis in common toads

Fig. 4 The degree of bone connectedness in Bufo bufo skulls illustrated in ventral view. The individuals with different cranial kinesis scores(CK i) are shown as follows: left CKi= 1, middle CK i= 2 and rightCK i = 5. Arrows point to connected bones. The abbreviations are

Fig. 3 in Differentiation of skull morphology and cranial kinesis in common toads

Fig. 3 Bivariate plot on skull shape variables in Bufo bufo (blue symbols) and B. spinosus (red symbols) over the first (PC1) and second axes (PC2) of a principal component analysis, with females shown by solid symbols and males by open symbols. The amount of variation explained over the axes is shown within parentheses. The shape changes along PC axes are summarised by wireframe graphs depicting the dorsal (top row), posterior (middle row) and lateral (bottom row) skull shape. The images of 3D models showing mean skull shape were presented

opencc-zeroFeb 2022View details →

Cranial kinesis facilitates quick retraction of stuck woodpecker beaks

Much like nails that are hammered into wood, the beaks of woodpeckers regularly get stuck upon impact. A kinematic video analysis of pecking by black woodpeckers shows how they manage to quickly withdraw their beaks, revealing a two-phase pattern: first a few degrees of nose-down rotation about the nasofrontal hinge causes the tip of the upper beak to be retruded while its proximal end is lifted. Next, the head is lifted, causing nose-up rotation about the nasofrontal hinge while the lower beak starts retruding and initiates the final freeing. We hypothesise that these consecutive actions, taking place in about 0.05 s, facilitate beak retraction by exploiting the presumably low frictional resistance between the upper and lower beak keratin surfaces, allowing them to slide past each other. It also demonstrates the counter-intuitive value of maintaining cranial kinesis in a species adapted to deliver forceful impacts.

opencc-zeroNov 2022View details →

CT data for: Insight into the evolutionary assemblage of cranial kinesis from a Cretaceous bird

The independent movements and flexibility of various parts of the skull, called cranial kinesis, is an evolutionary innovation that is found in living vertebrates only in some squamates and crown birds and is considered to be a major factor underpinning much of the enormous phenotypic and ecological diversity of living birds, the most diverse group of extant amniotes. Compared to the postcranium, our understanding of the evolutionary assemblage of the characteristic modern bird skull has been hampered by sparse fossil records of early cranial materials, with competing hypotheses regarding the evolutionary development of cranial kinesis among early members of the avialans. Here, a detailed three-dimensional reconstruction of the skull of the Early Cretaceous enantiornithine Yuanchuavis kompsosoura allows for its in-depth description, including elements that are poorly known among early diverging avialans but are central to deciphering the mosaic assembly of features required for modern avian cranial kinesis. Our reconstruction of the skull shows evolutionary and functional conservation of the temporal and palatal regions by retaining the ancestral theropod dinosaurian configuration within the skull of this otherwise derived and volant bird. Geometric morphometric analysis of the palatine suggests that loss of the jugal process represents the first step in the structural modifications of this element leading to the kinetic crown bird condition. The mixture of plesiomorphic temporal and palatal structures together with a derived avialan rostrum and postcranial skeleton encapsulated in Yuanchuavis manifests the key role of evolutionary mosaicism and experimentation in early bird diversification.

publicFeb 2022View details →

Cranial kinesis facilitates quick retraction of stuck woodpecker beaks

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publicNov 2022View details →

CT data for: Insight into the evolutionary assemblage of cranial kinesis from a Cretaceous bird

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Data from: The roles of joint tissues and jaw muscles in palatal biomechanics of the Savannah monitor (Varanus exanthematicus) and their significance for cranial kinesis

Many vertebrates exhibit cranial kinesis, or movement between bones of the skull other than at the jaw joint. Many kinetic species possess a particular suite of features to accomplish this movement, including flexible cranial joints and protractor musculature. Whereas the skeletal anatomy of these kinetic systems is well understood, how these joints are biomechanically loaded, how different soft tissues affect joint loading and kinetic capacity, and how the protractor musculature loads the skull remain poorly understood. Here we developed a Finite Element Model of the savannah monitor, Varanus exanthematicus, a modestly kinetic lizard, to better elucidate the roles of soft tissue in mobile joints and protractor musculature on cranial loading. We described the 3D resultants of jaw muscles and histology of palatobasal, otic and jaw joints. We tested the effects of joint tissue types, bite point, and muscle loads to evaluate the biomechanical role of muscles have on the palate and braincase. We found the jaw muscles have significant mediolateral components and resultants that can impart stability across palatocranial joints. We found articular tissues affect the magnitude of strains experienced across the palatobasal and otic joints. We found that without protractor muscle loading, the palate, quadrate and braincase experience higher strains suggesting this muscle helps insulate the braincase and palatoquadrate from high loads. Finally, we found the cross-sectional properties of the bones of Varanus exanthematicus is well suited for performing under torsional loads. These findings suggest that torsion may be a significant driver in the evolution of cranial kinesis in lepidosaurs.

opencc-zeroAug 2019View details →

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Data from: Joint histology in Alligator mississippiensis challenges the identification of synovial joints in fossil archosaurs and inferences of cranial kinesis

Archosaurs, like all vertebrates, have different types of joints that allow or restrict cranial kinesis, such as synovial joints and fibrous joints. In general, synovial joints are more kinetic than fibrous joints, because the former possess a fluid-filled cavity and articular cartilage that facilitate movement. Even though there is a considerable lack of data on the microstructure and the structure–function relationships in the joints of extant archosaurs, many functional inferences of cranial kinesis in fossil archosaurs have hinged on the assumption that elongated condylar joints are (i) synovial and/or (ii) kinetic. Cranial joint microstructure was investigated in an ontogenetic series of American alligators, Alligator mississippiensis. All the presumably synovial, condylar joints found within the head of the American alligator (the jaw joint, otic joint and laterosphenoid–postorbital (LS–PO) joint) were studied by means of paraffin histology and undecalcified histology paired with micro-computed tomography data to better visualize three-dimensional morphology. Results show that among the three condylar joints of A. mississippiensis, the jaw joint was synovial as expected, but the otherwise immobile otic and LS–PO joints lacked a synovial cavity. Therefore, condylar morphology does not always imply the presence of a synovial articulation nor mobility. These findings reveal an undocumented diversity in the joint structure of alligators and show that crocodylians and birds build novel, kinetic cranial joints differently. This complicates accurate identification of synovial joints and functional inferences of cranial kinesis in fossil archosaurs and tetrapods in general.

opencc-zeroDec 2016View details →

Fig. 5 in Palatal Biomechanics and its Significance for Cranial Kinesis in Tyrannosaurus rex

Fig. 5. Heat maps depicting Von Mises strains in Gekko gecko (A–C), Psittacus erithacus (D–F), and Tyrannosaurus rex (G–I) in Left, Neutral; Middle, FAM; and Right, MLM postures of each taxon. Models are shown in left oblique (top), left lateral (middle), and ventral (bottom) views. Heat maps show strains in postural models with all muscles fired simultaneously. Areas of high strain appear in warmer colors; white areas are beyond the scales presented with the models. Cooler colors depict areas of low strain concentration. Bones of the left lateral dermatocranium (i.e., portions of the maxilla, jugal, lacrimal, postorbital, and quadratojugal bones) have been removed on heat maps of T. rex to show details of the palate, although all bones were in place for the analysis.

Fig. 3 in Palatal Biomechanics and its Significance for Cranial Kinesis in Tyrannosaurus rex

Fig. 3. Mapped attachments of jaw muscles used to load finite element models of (A) Gekko gecko; (B) Psittacus erithacus, and (C) Tyrannosaurus rex in Top: left oblique; Middle: left lateral; and Bottom: ventral views for each taxon. Muscle map colors follow same palate and hypotheses of homology as Holliday (2009).

Fig. 2 in Palatal Biomechanics and its Significance for Cranial Kinesis in Tyrannosaurus rex

Fig. 2. Comparisons of postures using overlays of each of the three models: Left, Gekko gecko; Middle, Tyrannosaurus rex; Right, Psittacus erithacus showing postural change in left lateral (A) and ventral (B) views and in rostral (C), lateral, (D), and ventral (E) views showing overlaid postural configurations used to model kinetic competency. Postures are overlaid using the jaw joint as the origin of the axes. Neutral models are represented in gray, FAM models in orange, and MLM models in blue. Angles of rotation/translation at the otic joint are shown using color-coded angle measurements in (A) and (B).

Fig. 1 in Palatal Biomechanics and its Significance for Cranial Kinesis in Tyrannosaurus rex

Fig. 1. Postural Kinetic Competency modeling workflow followed in this study. Microcomputed Tomography data (A) are segmented to build 3D models by segmenting individual bones (or bony segments; e.g., beak, braincase) as separate elements (B). 3D models are reconstructed in kinetic postures with individual elements realistically articulated (C). The resulting models are imported into Strand7 as stereolithographical files and are meshed using 4-node tetrahedra (D). Meshed models are prepared for finite element analysis (FEA) by mapping muscles on the surface and eliminating tetrahedra in joint areas (E1). Beams are attached to the facing sides of joint surfaces and are given material properties reflecting capsular or sutural ligaments (E2). The resulting finite element model is loaded using distributed muscle forces via the BoneLoad MATLAB program and Strand7 FEA software (F).

Fig. 10 in Palatal Biomechanics and its Significance for Cranial Kinesis in Tyrannosaurus rex

Fig. 10. Illustration of Tyrannosaurus skull in left lateral (top) and ventral (bottom) views with key functional characteristics of the feeding apparatus. Numerous features of the skull of Tyrannosaurus suggest it was not capable of substantial cranial kinesis.

Fig. 9 in Palatal Biomechanics and its Significance for Cranial Kinesis in Tyrannosaurus rex

Fig. 9. Comparison of neutral postures of Tyrannosaurus rex and Psittacus erithacus in left rostrolateral view showing effects of protractor muscle activation, constraints, and sutural materials on the behavior of models. Jaw joint constraints with activated (A) and deactivated (B) protractor muscles reveal few differences in strains in the model. Occipital constraints with activated (C) and deactivated (D) protractor muscles reveal significant differences in strain distribution in the palate. Regions of models with hatching represent areas that have been cut away to allow for better visualizations of internal structures. Psittacus erithacus is presented to show differences between using rodent sutural properties (E) and canine sutural properties (F). Rodent sutural properties were used in Psittacus and Gekko and canine sutural properties were used in Tyrannosaurus. Sutural properties were considered based on taxon size.

Fig. 8 in Palatal Biomechanics and its Significance for Cranial Kinesis in Tyrannosaurus rex

Fig. 8. Strains of regions of interest in the palatal elements of Tyrannosaurus rex. Regions of interest and scatter plots showing individual sample points as well as median strains (color-coded by sampling region) are represented. Otic, middle, and ventral regions correspond to sampling of the quadrate whereas Rostral, middle, and caudal regions correspond to sampling areas of the palatine and pterygoid. Each sampling region consists of 50 tetrahedra sampled randomly from the surface of the skeletal element. Horizontal lines representing the median value of the neutral posture are shown in red in each region of the palatal bones to facilitate comparison across postures.

Fig. 7 in Palatal Biomechanics and its Significance for Cranial Kinesis in Tyrannosaurus rex

Fig. 7. Strains of regions of interest in the palatal elements of Psittacus erithacus. Regions of interest and scatter plots showing individual sample points as well as median strains (color-coded by sampling region) are represented. Otic, middle, and ventral regions correspond to sampling of the quadrate whereas Rostral, middle, and caudal regions correspond to sampling areas of the palatine and pterygoid. Each sampling region consists of 50 tetrahedra sampled randomly from the surface of the skeletal element. Horizontal lines representing the median value of the neutral posture are shown in red in each region of the palatal bones to facilitate comparison across postures.

Fig. 4 in Palatal Biomechanics and its Significance for Cranial Kinesis in Tyrannosaurus rex

Fig. 4. The relationship between fiber length, pennation angle, and force in muscle physiology and its application to reconstructing function in fossil taxa using recent case studies. PCSA is a function of pennation angle and fiber length and is mapped as a heatmap with contour lines. We replotted the regression line from Bates and Falkingham, 2018 (labeled "B&F 2018") showing the classic prediction that increasing pennation in order to accommodate shorter muscle fibers increases PCSA. PCSA values from recent studies, Gignac and Erickson, 2017 (labeled "G&E 2017") and Bates and Falkingham, 2018, of Tyrannosaurus cranial biomechanics are also plotted to show similarities in approaches.

Fig. 6 in Palatal Biomechanics and its Significance for Cranial Kinesis in Tyrannosaurus rex

Fig. 6. Strains of regions of interest in the palatal elements of Gekko gecko. Regions of interest and scatter plots showing individual sample points as well as median strains (color-coded by sampling region) are represented. Otic, middle, and ventral regions correspond to sampling of the quadrate whereas rostral, middle, and caudal regions correspond to sampling areas of the palatine and pterygoid. Each sampling region consists of 50 tetrahedra sampled randomly from the surface of the skeletal element. Horizontal lines representing the median value of the neutral posture are shown in red in each region of the palatal bones to facilitate comparison across postures.