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Studies on the morphology and function of the skull in the boidae (Serpentes). Part II. Morphology and function of the jaw apparatus in Python sebae and Python molurus
Abstract
Heads of the boid snakes Python sebae and Python molurus were dissected and the arthrology, myology and dentition studied. Living specimens of these species were observed and their feeding behavior analyzed by means of high- and regular-speed motion pictures. Camera speeds of up to 400 frames per second permitted examination of the jaw movements during the striking and seizing of prey. Motion picture studies conducted at regular speeds provided information on cranial movements during the swallowing of prey. The morphology of the head was correlated with observed movements in an attempt to analyze the functional and adaptive implications of the jaw apparatus.
The cranial apparatus was discussed in terms of a linkage or kinematic chain whose constrainment and degrees of freedom were examined and compared with the jaw linkage of lizards. It was concluded that the very rigidly constrained mechanism in lizards is in remarkably sharp contrast to the very loose apparatus in snakes.
Motions of various cranial bones were analyzed with particular attention given the mechanical factors involved. In full protraction the maxillae and palatines are lifted and rotated outward about a longitudinal axis. These movements are important in orienting the teeth with respect to the prey and are related to seizing and swallowing.
... Canine teeth can also be straight or curved [5]. Curved claws and teeth have been associated with prey capture and retention in many animals, including birds, snakes, sharks and seals [11][12][13][14][15][16][17][18][19]. In predatory mammals, curved canines have been associated with shaking behaviours and are thought to act as hooks at the front of the mouth that prevent the prey from slipping out of grasp [5,13]. ...
... When biting into prey, the tip of the tooth makes initial contact with the food and a compressive force is directed along the long axis of the tooth to its base. However, the direction of force will vary depending on the angle that the tooth tip contacts prey [12,19], such as when biting into differently sized prey or biting in distinct ways (encircling the throat versus snapping at flanks). If the tooth is already embedded in the prey, the predator may pull away from the prey or begin shaking it [20,22]. ...
... 9: 220701 likely related to the size of the prey being bitten into or the approach angle of the predator to the prey. This has been investigated in snakes [12,73,74]; however, it requires further study in mammalian carnivores. ...
Canine teeth are vital to carnivore feeding ecology, facilitating behaviours related to prey capture and consumption. Forms vary with specific feeding ecologies; however, the biomechanics that drive these relationships have not been comprehensively investigated. Using a combination of beam theory analysis (BTA) and finite-element analysis (FEA) we assessed how aspects of canine shape impact tooth stress, relating this to feeding ecology. The degree of tooth lateral compression influenced tolerance of multidirectional loads, whereby canines with more circular cross-sections experienced similar maximum stresses under pulling and shaking loads, while more ellipsoid canines experienced higher stresses under shaking loads. Robusticity impacted a tooth's ability to tolerate stress and appears to be related to prey materials. Robust canines experience lower stresses and are found in carnivores regularly encountering hard foods. Slender canines experience higher stresses and are associated with carnivores biting into muscle and flesh. Curvature did not correlate with tooth stress; however, it did impact bending during biting. Our simulations help identify scenarios where canine forms are likely to break and pinpoint areas where this breakage may occur. These patterns demonstrate how canine shape relates to tolerating the stresses experienced when killing and feeding, revealing some of the form–function relationships that underpin mammalian carnivore ecologies.
... Booids and pythonoids together form one of the major groups of 'macrostomatan' snakes ( Fig. 1). Their upper and lower jaw complexes are both highly kinetic 86 , with the palatomaxillary arch bearing particularly strongly recurved teeth ( Fig. 7a-f). In booid-pythonoids, the ability to consume proportionally large prey items is achieved mainly via marked posterior elongation of the supratemporal throughout ontogeny, which shifts the jaw articulation posteriorly relative to the skull 35,43 . ...
... 5b, 6b; see also Refs. 1,84,86 ). ...
... In the latter case, we determined whether to score these elements as 'connected' or not based on the functional morphology of the bones in question (as informed by personal observations and/or anatomical studies; see references below, especially Refs. 83,84,86,91,[111][112][113], including the presence of features such as articulatory facets or processes. For example, in snakes, the palatine typically does not directly contact the maxilla, in contrast to the extensive osseous contact typical of non-snake lizards; however, these elements do typically come into close proximity, with one or both bones often bearing processes mediating this junction, which are then ultimately joined by soft-tissue. ...
Traditionally considered the earliest-diverging group of snakes, scolecophidians are central to major evolutionary paradigms regarding squamate feeding mechanisms and the ecological origins of snakes. However, quantitative analyses of these phenomena remain scarce. Herein, we therefore assess skull modularity in squamates via anatomical network analysis, focusing on the interplay between ‘microstomy’ (small-gaped feeding), fossoriality, and miniaturization in scolecophidians. Our analyses reveal distinctive patterns of jaw connectivity across purported ‘microstomatans’, thus supporting a more complex scenario of jaw evolution than traditionally portrayed. We also find that fossoriality and miniaturization each define a similar region of topospace (i.e., connectivity-based morphospace), with their combined influence imposing further evolutionary constraint on skull architecture. These results ultimately indicate convergence among scolecophidians, refuting widespread perspectives of these snakes as fundamentally plesiomorphic and morphologically homogeneous. This network-based examination of skull modularity—the first of its kind for snakes, and one of the first to analyze squamates—thus provides key insights into macroevolutionary trends among squamates, with particular implications for snake origins and evolution.
... The movement of the lower jaw, in contrast, is more independent of the neck and body (Akersten, 1985). This affects the forces and direction of contact between these teeth and food and influences how they are used as the teeth penetrate prey (Frazzetta, 1988(Frazzetta, , 1966Anderson, 2018;Antón et al., 2020). Where there are differences in the role played by upper and lower teeth, we would expect to see differences in their shape. ...
... Both these axes explained significant portions of the overall shape variance, determined by the broken stick method (veGan package; Oksanen et al., 2020). Robustness and curvature are morphologically important because they are likely to affect the ability of a canine tooth to puncture and hold onto prey (Frazzetta, 1966;Lucas & Luke, 1984;Van Valkenburgh & Ruff, 1987;Freeman & Lemen, 2006). According to Uyeda et al. (2015), PC scores can be used separately where there is a clear biological justification. ...
... This is probably associated with how closely the central axis of the tooth matches the direction of force when biting. In curved canines they do not match closely, producing an uneven distribution of both compressive and tensile stresses (Frazzetta, 1966;Gordon, 2009). However, in straight canines they are essentially parallel, which results in a roughly equal distribution of compressive stresses (Frazzetta, 1966;Gordon, 2009). ...
Often the first point of contact between predator and prey, mammalian canine teeth are essential for killing, dismembering and consuming prey. Yet despite their importance, few associations among shape, function and phylogeny are established. We undertook the first comprehensive analysis of canine tooth shape across predatory mammals (Carnivora, Didelphimorphia and Dasyuromorphia), integrating shape analysis with function of this fundamental feature. Shape was quantified using three-dimensional geometric morphometrics and cross-sectional sharpness. Canines vary in three main ways (sharpness, robustness and curvature) which vary with diet, killing behaviour and phylogeny. Slender, sharp canines are associated with carnivores such as felids that target the neck of their prey and primarily consume the ‘softer’ parts of a carcass. Robust, blunt canines are found in mustelids and dasyurids that typically consume ‘harder’ materials, such as bone, or bite into skulls. Differences in the killing behaviours of felids and canids probably result in more curved canines in the latter, which act as hooks to hold prey. We find functional specialization in the upper and lower canines of individuals and across the major mammalian clades. These patterns demonstrate how canine teeth are adapted to suit diverse diets and hunting styles, enabling mammals to become some of nature's most successful predators.
... However, while the information from these morphological works is no doubt valuable for understanding how different prey may be handled, none directly link the tooth morphology to the behavior of prey capture itself. Frazzetta (1966) described the shape of the teeth in Python molurus and Python sebae, two large pythons, and noted that the teeth in the upper jaws were quite curved. The working hypothesis was that the shape of the teeth allowed the python to stab its prey during a strike, so that the prey would be impaled by the teeth of both jaws simultaneously. ...
... For the occlusal third, the arm of the angle ran from the center of the base through the tip of the tooth. With these angles, we assigned teeth to three categories: curved, linear, and recurved (Frazzetta 1966;Wright et al. 1979;Deufel and Cundall 1999). We defined a curved tooth as a tooth where the angle of the occlusal third was smaller than the middle and basal thirds. ...
... There is a clear relationship between the shape of the teeth throughout the mouth of B. constrictors and their predatory strike behavior. As others have noted, the teeth in snakes function beyond stabbing the A B prey during a strike , assumed to be the role of the enlarged teeth for decades (Frazzetta 1966). The different teeth throughout the jaws function differently during the prey capture sequence, as is observed in fish (Cohen et al. 2020a(Cohen et al. , 2020b. ...
Synopsis
Snakes, with the obvious exception of the fangs, are considered to lack the regional specialization of tooth shape and function which are exemplified by mammals. Recent work in fishes has suggested that the definition of homodont and heterodont are incomplete without a full understanding of the morphology, mechanics, and behavior of feeding. We investigated this idea further by examining changes in tooth shape along the jaw of Boa constrictor and integrating these data with the strike kinematics of boas feeding on rodent prey. We analyzed the shape of every tooth in the skull, from a combination of anesthetized individuals and CT scanned museum specimens. For strike kinematics, we filmed eight adult boas striking at previously killed rats. We determined the regions of the jaws that made first contact with the prey, and extrapolated the relative positions of those teeth at that moment. We further determined the roles of all the teeth throughout the prey capture process, from the initiation of the strike until constriction began. We found that the teeth in the anterior third of the mandible are the most upright, and that teeth become progressively more curved posteriorly. Teeth on the maxilla are more curved than on the mandible, and the anterior teeth are more linear or recurved than the posterior teeth. In a majority of strikes, boas primarily made contact with the anterior third of the mandible first. The momentum from the strike caused the upper jaws and skull to rotate over the rat. The more curved teeth of the upper jaw slid over the rat unimpeded until the snake began to close its jaws. In the remaining strikes, boas made contact with the posterior third of both jaws simultaneously, driving through the prey and quickly retracting, ensnaring the prey on the curved posterior teeth of both jaws. The curved teeth of the palatine and pterygoid bones assist in the process of swallowing.
... Given their burrowing lifestyle and slow-moving prey, it is unlikely that predatory striking behavior is needed or could even be employed in their subterranean environments (Cundall et al. 2007). To date, what we know about striking derives from alethinophidians, and particularly from booid (Frazzetta 1966;Cundall and Deufel 1999;Deufel and Cundall 1999;Cundall et al. 2007) and colubroid snakes (Van Riper 1954;Greenwald 1974Greenwald , 1978Janoo and Gasc 1992;Kardong and Bels 1998;LaDuc 2002;Herrel et al. 2011;). Most studies have addressed forward strikes in a terrestrial environment over a relatively narrow range of temperatures (ca. ...
... Kardong and Bels implied ballistic motion in feeding strikes by stating that adjustments to strike trajectory or in response to prey evasion are made after contact, not during forward movement. However, Frazzetta (1966) discussed a snake changing course during a strike. Some indirect evidence suggests that strikes may not be ballistic. ...
... Upon contact with prey, jaw closing marks the end of a strike (Cundall and Greene 2000). The mechanism of tooth engagement with prey is not well known and may involve snaring , downward or rearward stabbing (Frazzetta 1966;LaDuc 2002; but see Deufel and Cundall 1999), or other movements by both snake and prey. For many Fig. 14.4 ...
... Given their burrowing lifestyle and slow-moving prey, it is unlikely that predatory striking behavior is needed or could even be employed in their subterranean environments (Cundall et al. 2007). To date, what we know about striking derives from alethinophidians, and particularly from booid (Frazzetta 1966;Cundall and Deufel 1999;Deufel and Cundall 1999;Cundall et al. 2007) and colubroid snakes (Van Riper 1954;Greenwald 1974Greenwald , 1978Janoo and Gasc 1992;Kardong and Bels 1998;LaDuc 2002;Herrel et al. 2011;). Most studies have addressed forward strikes in a terrestrial environment over a relatively narrow range of temperatures (ca. ...
... Kardong and Bels implied ballistic motion in feeding strikes by stating that adjustments to strike trajectory or in response to prey evasion are made after contact, not during forward movement. However, Frazzetta (1966) discussed a snake changing course during a strike. Some indirect evidence suggests that strikes may not be ballistic. ...
... Upon contact with prey, jaw closing marks the end of a strike (Cundall and Greene 2000). The mechanism of tooth engagement with prey is not well known and may involve snaring , downward or rearward stabbing (Frazzetta 1966;LaDuc 2002; but see Deufel and Cundall 1999), or other movements by both snake and prey. For many Fig. 14.4 ...
Snakes are a diverse group of squamate reptiles characterized by a unique feeding system and other traits associated with elongation and limblessness. Despite the description of transitional fossil forms, the evolution of the snake feeding system remains poorly understood, partly because only a few snakes have been studied thus far. The idea that the feeding system in most snakes is adapted for consuming relatively large prey is supported by studies on anatomy and functional morphology. Moreover, because snakes are considered to be gape-limited predators, studies of head size and shape have shed light on feeding adaptations. Studies using traditional metrics have shown differences in head size and shape between males and females in many species that are linked to differences in diet. Research that has coupled robust phylogenies with detailed morphology and morphometrics has further demonstrated the adaptive nature of head shape in snakes and revealed striking evolutionary convergences in some clades. Recent studies of snake strikes have begun to reveal surprising capacities that warrant further research. Venoms, venom glands, and venom delivery systems are proving to be more widespread and complex than previously recognized. Some venomous and many nonvenomous snakes constrict prey. Recent studies of constriction have shown previously unexpected responsiveness, strength, and the complex and diverse mechanisms that incapacitate or kill prey. Mechanisms of drinking have proven difficult to resolve, although a new mechanism was proposed recently. Finally, although considerable research has focused on the energetics of digestion, much less is known about the energetics of striking and handling prey. A wide range of research on these and other topics has shown that snakes are a rich group for studying form, function, behavior, ecology, and evolution.
... Movements within the skull of reptiles have been the objective of intensive research ever since the publication of VERSLUYS' (1912) classic paper on the subject. Since then, a vast literature has accumulated, particularly on cranial kinesis in "lizards" (ARNOLD 1998;BRADLEY 1903;BORSUK-BIOLYNICKA 1985;CONDON 1987;DEVREE & GANS 1987a, b;FRAZZETTA 1962FRAZZETTA , 1983FRAZZETTA , 1986IORDANSKY 1970IORDANSKY , 1971IORDANSKY , 1990RrEPPEL 1978RrEPPEL a, 1979SMITH 1980SMITH , 1982SMITH & HYLANDER 1985;THROCKMORTON 1976THROCKMORTON , 1978THROCKMORTON , 1980THROCKMORTON & Clarke 1981), and in snakes (ALBRIGHT & NELSON 1959, BOLTT&EwER 1964CUNDALL 1983CUNDALL , 1987CUNDALL , 1995CUNDALL & GANS 1979; o. Rieppel and H. Zaher CUNDALL & IRISH 1989;CUNDALL & SHARDO 1995;DULLEMEIJER 1956DULLEMEIJER , 1959FRAZZETTA 1966;GANS 1961;KARDONG 1977KARDONG , 1986KARDONG & BERKHOUDT 1998;KARDONG et al. 1986). ...
... Movements within the skull of reptiles have been the objective of intensive research ever since the publication of VERSLUYS' (1912) classic paper on the subject. Since then, a vast literature has accumulated, particularly on cranial kinesis in "lizards" (ARNOLD 1998;BRADLEY 1903;BORSUK-BIOLYNICKA 1985;CONDON 1987;DEVREE & GANS 1987a, b;FRAZZETTA 1962FRAZZETTA , 1983FRAZZETTA , 1986IORDANSKY 1970IORDANSKY , 1971IORDANSKY , 1990RrEPPEL 1978RrEPPEL a, 1979SMITH 1980SMITH , 1982SMITH & HYLANDER 1985;THROCKMORTON 1976THROCKMORTON , 1978THROCKMORTON , 1980THROCKMORTON & Clarke 1981), and in snakes (ALBRIGHT & NELSON 1959, BOLTT&EwER 1964CUNDALL 1983CUNDALL , 1987CUNDALL , 1995CUNDALL & GANS 1979; o. Rieppel and H. Zaher CUNDALL & IRISH 1989;CUNDALL & SHARDO 1995;DULLEMEIJER 1956DULLEMEIJER , 1959FRAZZETTA 1966;GANS 1961;KARDONG 1977KARDONG , 1986KARDONG & BERKHOUDT 1998;KARDONG et al. 1986). ...
... Since then, a vast literature has accumulated, particularly on cranial kinesis in "lizards" (ARNOLD 1998;BRADLEY 1903;BORSUK-BIOLYNICKA 1985;CONDON 1987;DEVREE & GANS 1987a, b;FRAZZETTA 1962FRAZZETTA , 1983FRAZZETTA , 1986IORDANSKY 1970IORDANSKY , 1971IORDANSKY , 1990RrEPPEL 1978RrEPPEL a, 1979SMITH 1980SMITH , 1982SMITH & HYLANDER 1985;THROCKMORTON 1976THROCKMORTON , 1978THROCKMORTON , 1980THROCKMORTON & Clarke 1981), and in snakes (ALBRIGHT & NELSON 1959, BOLTT&EwER 1964CUNDALL 1983CUNDALL , 1987CUNDALL , 1995CUNDALL & GANS 1979; o. Rieppel and H. Zaher CUNDALL & IRISH 1989;CUNDALL & SHARDO 1995;DULLEMEIJER 1956DULLEMEIJER , 1959FRAZZETTA 1966;GANS 1961;KARDONG 1977KARDONG , 1986KARDONG & BERKHOUDT 1998;KARDONG et al. 1986). In spite of these efforts, the transition from kinetic inertial feeding characteristic of sclerog10ssan "lizards" (SCHWENK & THROCKMORTON 1989) to the unilateral feeding characteristic of snakes (GANS 1961) remains poorly understood. ...
A recently proposed scenario for the gradual evolution of snake feeding from mosasaur ancestors is examined with respect to internal consistency and the empirical evidence proposed in its support. The scenario is problematic on both counts.
... It has been proposed that each of these features provide a specific benefit in the prey apprehension and killing techniques of wild canids (Crofts et al., 2020;Pollock et al., 2021). The curvature may help with the retention of prey, preventing it slipping from the mouth as it attempts to pull away (Frazzetta, 1966;Pollock et al., 2021). The ellipticity may help distribute stress when shearing forces are applied (Goldschmidt et al., 2017). ...
... Straight canines are generally found in species that regularly bite into hard objects (head biters) and nape throat killers (felids) . When biting, the direction of force in straight teeth is parallel to the long axis of the tooth, which results in more even stress distribution around the central axis (Frazzetta, 1966;Pollock et al., 2021Pollock et al., , 2022. The highest curvature is found in the shake tear and shake toss killers [red fox (Vulpes vulpes), coyote (Canis latrans), jackal (Canis mesomelas), and civet (Viverra zibetha)] in which prey are torn, shaken or tossed until dead . ...
Canine tooth shape is known to vary with diet and killing behavior in wild animals and the relationship between form and function is driven in part by selective pressure. However, comparative investigation of the domestic dog (Canis lupus familiaris) is of interest. How do they compare to their wild counterparts? This study sought to quantify and characterize the morphology of the canine tooth in the domestic dog, and to provide a preliminary investigation into the variance in canine tooth morphology across individual dogs of varying breeds. Three-dimensional (3D) models generated from micro-computed tomography (µ-CT) studies of 10 mature maxillary canine teeth from the domesticated dog (Canis lupus familiaris) were used to quantify key morphological features and evaluate variance among dogs. Results show that, utilizing modern imaging and model building software, the morphology of the canine tooth can be comprehensively characterized and quantified. Morphological variables such as second moment of area and section modulus (geometrical parameters related to resistance to bending), as well as aspect ratio, ridge sharpness, cusp sharpness and enamel thickness are optimized in biomechanically critical areas of the tooth crown to balance form and function. Tooth diameter, second moment of area, section modulus, cross sectional area, tooth volume and length as well as enamel thickness are highly correlated with body weight. In addition, we found preliminary evidence of morphological variance across individual dogs. Quantification of these features provide insight into the balance of form and function of the canine tooth in wild and domesticated canids. In addition, results suggest that variance between dogs exist in some morphological features and most morphological features are highly correlated with body weight.
... The midpoint of the anterior margin of the prefrontal lateral lamina projects rostrally like the apex of a triangle ( Figure 6a). The orbital lamina is distinctly concave, and there is a horn-shaped mediodorsally curved projection jutting out from its ventromedial edge (Figure 6b-d), akin to a projection at the same site in pythons labeled as medial extension by Frazzetta (1966). A lacrimal foramen perforates the orbital lamina that finally opens anteriorly with a ventromedially widened foramen ...
... Various forms of connection between these two bones are found in "scolecophidians" (Chretien et al., 2019;Cundall & Irish, 2008) and in fossorial basal F I G U R E 2 5 Hypoptophis wilsonii (RBINS-VER-REP 9712a), ventral view of the premaxilla, nasals, prefrontals, and the frontal, showing the "central rod" (indicated with blue lines) -The primary loading stress-bearing axis consisting of the premaxilla, the medial vertical laminae of the nasals and the subolfactory processes, and the medial flanges of the frontals (as well as the "outer shell," indicated with ochre circles-a contact between the posteroventral process from the nasal horizontal laminae and the prefrontals alethinophidians (Cundall & Rossman, 1993;Comeaux et al., 2010;Olori & Bell, 2012;Frazzetta, 1999;Cundall & Irish, 2008;present study). Although pythons and boas also have the nasal in contact with the prefrontal, this contact is mediated by a well-developed dorsal lappet from the nasal (Cundall & Irish, 2008;Frazzetta, 1966), which does not appear to be adapted for burrowing. Nasal-prefrontal contact is noted in the stem snake Dinilysia patagonica too (Zaher & Scanferla, 2012), which might have a semifossorial-semiaquatic lifestyle like some homalopsids (Palci et al., 2017). ...
Fossoriality evolved early in snakes, and has left its signature on the cranial morphology of many extinct Mesozoic and early Caenozoic forms. Knowledge of the cranial osteology of extant snakes is indispensable for associating the crania of extinct lineages with a particular mode of life; this applies to fossorial taxa as well. In the present work, we provide a detailed description of the cranium of Hypoptophis wilsonii, a member of the subfamily Aparallactinae, using micro‐computed tomography (CT). This is also the first thorough micro‐CT‐based description of any snake assigned to this African subfamily of predominantly mildly venomous, fossorial and elusive snakes. The cranium of Hypoptophis is adapted for a fossorial lifestyle, with increased consolidation of skull bones. Aparallactines show a tendency towards reduction of maxillary length by bringing the rear fangs forward. This development attains its pinnacle in the sister subfamily Atractaspidinae, in which the rear fang has become the ‘front fang’ by a loss of the part of the maxilla lying ahead of the fang. These dentitional changes likely reflect adaptation to subdue prey in snug burrows. An endocast of the inner ear of Hypoptophis shows that this genus has the inner ear typical of fossorial snakes, with a large, globular sacculus. A phylogenetic analysis based on morphology recovers Hypoptophis as a sister taxon to Aparallactus. We also discuss the implications of our observations on the burrowing origin hypothesis of snakes.
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... This concavity is formed by a vertical ridge situated between the anterolateral edge and the stylohyal process, or confluent with the latter. M. adductor mandibulae posterior originates in this fossa and inserts on the entire prearticular crest (Frazzetta 1966;Haas 1973). Such a concavity is apparently lacking in Palaeo python schaali. ...
... Teeth near the posterior end of the maxillary facial process are more upright than in Palaeopython cadurcensis (Georgalis et al. 2021). Furthermore, the proximal shaft (sensu Frazzetta 1966) of the first preserved tooth of the paralectotype of P. cadurcensis, MNHN-QU 16321 (Georgalis et al. 2021), which is the 4 th , has an angle of about 22° to the horizontal, lower than in any species measured by Frazzetta (1966), consistent with the overall impression of highly recumbent teeth in that taxon. ...
... Linkage mechanisms such as four-bar mechanisms are common in animal joints, particularly in fish jaws [1], lizard jaws [2], snake jaws [3], bird wings [4] and mammalian limbs [5]. A comprehensive study of the linkage mechanisms in animal joints was carried out in 1996 by Muller [6]. ...
... For example, it has been found that the coupler link in the largemouth bass (see Section 3.2) stretches by around 5% at peak gape (mouth opening) [7]. The linkage mechanisms of snakes have also been found to be highly flexible [3]. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t 4 2 Limb and wing joints ...
This paper gives a review of biological mechanical linkage mechanisms. One purpose is to identify the range of kinematic functions that they are able to perform. A second purpose is to review progress in bioinspired designs. Ten different linkage mechanisms are presented. They are chosen because they cover a wide range of functionality and because they have potential for bioinspired design. Linkage mechanisms enable animal joints to perform highly sophisticated and optimised motions. A key function of animal linkage mechanisms is the optimisation of actuator location and mechanical advantage. This is crucially important for animals where space is highly constrained. Many of the design features used by engineers in linkage mechanisms are seen in nature such as short coupler links, extended bars, elastic energy storage and latch mechanisms. However, animal joints contain some features rarely seen in engineering such as integrated cam and linkage mechanisms, non-planar four-bar mechanisms, resonant hinges and highly redundant actuators. The extreme performance of animal joints together with the unusual design features makes them an important area of investigation for bioinspired designs. Whilst there has been significant progress in bioinspiration, there is potential for more, especially in robotics where compactness is a key design driver. Key words: four-bar mechanisms, mechanical advantage, kinematic amplification, multi-functioning.
... Lacerta viridis; Frazzetta, 1962), whereas in others it is a very loose ligamentous connection (e.g. snakes; Frazzetta, 1966; see also Evans, 2008). ...
... The quadrate of some basal alethinophidians is also characterized by the presence of a ventrolateral process or tuberosity in the area where the quadratomaxillary ligament and the m. retractor quadrati attach, just lateral to the mandibular condyle (Frazzetta, 1966). A tuberosity can be observed in Anilius and Cylindrophis (Fig. 6f,g), whereas a more pronounced triangular process can be observed in Aspidites, Morelia and Eunectes (Fig. 6j-l). ...
We examined the morphological diversity of the quadrate bone in squamate reptiles (i.e. lizards, snakes, amphisbaenians). The quadrate is the principal splanchnocranial element involved in suspending the lower jaw from the skull, and its shape is of particular interest because it is potentially affected by several factors, such as phylogenetic history, allometry, ecology, skull kinesis and hearing capabilities (e.g. presence or absence of a tympanic ear). Due to its complexity, the quadrate bone is also considered one of the most diagnostic elements in fragmentary fossil taxa. We describe quadrates from 38 species spread across all major squamate clades, using qualitative and quantitative (e.g. geometric morphometrics) methods. We test for possible correlations between shape variation and factors such as phylogeny, size, ecology and presence/absence of a tympanum. Our results show that the shape of the quadrate is highly evolutionarily plastic, with very little of the diversity explained by phylogenetic history. Size variation (allometric scaling) is similarly unable to explain much shape diversity in the squamate quadrate. Ecology (terrestrial/fossorial/aquatic) and presence of a tympanic ear are more significant, but together explain only about 20% of the diversity observed. Other unexplored and more analytically complex factors, such as skull biomechanics, likely play additional major roles in shaping the quadrates of lizards and snakes. We describe the morphological diversity of the quadrate bone in squamate reptiles, using both qualitative and quantitative methods. We found that ecology (especially fossorial) and the loss of a tympanic membrane are two important correlates of shape disparity.
... The traditional practice was to call the anterior-most, suas AEP (e.g. FRAZZETTA, 1966;McDOWELL, 1967;HAAS, 1973;CUNDALL, 1987). Anatomists, however, noted problems with this system (e.g. ...
... Whereas the tendinous origin of PTM does not usually reach ectopterygoid-maxilla junction in alethinophidians 'below' Caenophidia (e.g. FRAZZETTA, 1966;RIEPPEL, 1980;, it does so, albeit with exception, in caenophidians (e.g. McDOWELL, 1986;UNDERWOOD & KOCHVA, 1993;CUNDALL, 1986;DEUFEL & CUNDALL, 2003;present study) and this anterior shift in attachment site appears to be a derived state. ...
We studied jaw adductor muscles in eighteen species of South Asian colubroid snakes and presented a comparative account of their anatomy. The deepest layer of external adductor appears to be a composite of adductor mandibulae externus medialis and profundus fibres and
caenophidians are characterized by an attenuation of the former muscle which may be correlated with the development of a derived type
of mandible. Our observations further suggest that, though highly reduced, fibres homologous to adductor mandibulae externus medialis
may be present in at least some colubroids with a bodenaponeurosis. Some hitherto unreported features pertaining to levator anguli oris and
pterygomandibularis of some studied elapid, colubrine colubrid and ahaetuliine colubrid genera are also described.
... 18) that meets the frontal laterally in an articulation reminiscent of the booid condition. However, the frontal of booids forms an anterior, transversely oriented preorbital ridge (Frazzetta, 1966) for the suspension of the medially expanding dorsal lamina of the prefrontal. By contrast, the prefrontal meets the frontal along its lateral margin in an essentially longitudinally oriented articulation in Haasiophis (Figs. 3, 4;cf. ...
... The inner orbital lobe of the prefrontal (Frazzetta, 1966) is distinct on both sides of the skull, a notch in its medial margin probably indicating the passage of the lacrimal duct (Figs. 3, 4;cf. Tchernov et al., 2000, fig. ...
The fossil snake species Haasiophis terrasanctus Tchernov, Rieppel, Zaher, Polcyn, and Jacobs, 2000, from the early Upper Cretaceous of the Middle East, is described and illustrated, following a review of the current debate on snake relationships and origins. The description and discussion presented here adds important detail to the knowledge of this taxon and its phylogenetic significance beyond the limited account presented in the original description of Haasiophis . The species is remarkable in that it shows the skull of a relatively advanced (i.e., macrostomatan) snake, yet preserves well-developed hind limbs. The hind limb includes a femur, tibia, fibula, astragalus, calcaneum, distal tarsal four, and remains of four metatarsals and two phalanges. Haasiophis cannot be considered a juvenile specimen of Pachyrhachis . The implications of the presence of well-developed hind limbs in Haasiophis, Pachyrhachis , and Podophis for the cladistic analysis of the phylogenetic interrelationships of these fossil snakes is discussed. The presence of well-developed hind limbs in Pachyrhachis and Haasiophis also creates methodological problems for the cladistic analysis of the phylogenetic relationships of these fossil snakes. Scenarios of snake origins are reviewed and found to be deficient in the absence of a well-corroborated hypothesis of snake relationships within Squamata.
... However, such head realignment and fang adjustment occurred only after contact with the prey. Unlike pythons (Frazzetta, 1966), we observed no abrupt change in the trajectory of the head of the snake during the extend stage of a strike. This suggests that, during a single strike, adjustments in response to prey evasive action or inaccurate targeting are made only during the contact stage, not during the extend stage. ...
... Rattlesnake fangs are long, curved teeth. If their tips strike the surface of the prey obliquely, then penetration of the integument becomes mechanically more difficult (Frazzetta, 1966). Rarely do erected fangs stab the prey (sensu Van Riper, 1953). ...
The predatory behavior of rattlesnakes includes many distinctive preparatory phases leading to an extremely rapid strike, during which venom is injected. The rodent prey is then rapidly released, removing the snake's head from retaliation by the prey. The quick action of the venom makes possible the recovery of the dispatched prey during the ensuing poststrike period. The strike is usually completed in less than 0.5 s, placing a premium on an accurate strike that produces no significant errors in fang placement that could result in poor envenomation and subsequent loss of the prey. To clarify the basis for effective strike performance, we examined the basic kinematics of the rapid strike using high-speed film analysis. We scored numerous strike variables. Four major results were obtained. (1) Neurosensory control of the strike is based primarily upon sensory inputs via the eyes and facial pits to launch the strike, and upon tactile stimuli after contact. Correction for errors in targeting occurs not by a change in strike trajectory, but by fang repositioning after the jaws have made contact with the prey. (2) The rattlesnake strike is based upon great versatility and variation in recruitment of body segments and body postures. (3) Forces generated during acceleration of the head are transferred to posterior body sections to decelerate the head before contact with the prey, thereby reducing impact forces upon the snake's jaws. (4) Body acceleration is based on two patterns of body displacement, one in which acute sections of the body open like a gate, the other in which body segments flow around postural curves similar to movements seen during locomotion. There is one major implication of these results: recruitment of body segments, launch postures and kinematic features of the strike may be quite varied from strike to strike, but the overall predatory success of each strike by a rattlesnake is very consistent.
... the strong reduction of the basipterygoid processes ( Figure 2). This fibrous connection allows far greater mobility of the pterygoids, especially anteroposteriorly (Frazzetta, 1966). Red arrows indicate gaps bridged by ligaments; dashed lines indicate additional highly mobile joints. ...
The vertebrate head serves a diversity of functions, from energy intake to interactions with the biotic and abiotic environment. The loss of limbs in snakes placed additional selective pressures on the head as it must compensate for the functions that were fulfilled by the limbs such as manipulation, locomotion, or defense against other organisms. Rather than limiting snake diversification, selective pressures inherent to specific functions of the head allowed them to innovate, permitting the exploration of new anatomical and behavioral strategies. This chapter aims to highlight the richness in form, function, and adaptations of the head of snakes from an integrative and comparative perspective, in the light of their evolution and ecology. First, we discuss the defining features of the snake skull, followed by a review of what fossils can tell us about how snakes acquired their unique skull anatomy and the ecological origins of snakes. Next, we explore the macroevolution of skull diversity in extant snake species in the light of their ecology. From a functional perspective, * marion.segall@live.fr. § herrel@mnhn.fr. Marion Segall, Alessandro Palci, Phillip Skipwith et al. 2 we review data on the morphology and biomechanics of the head. We will then explore the relationships between external, osteological, and endocranial morphology and the sensory ecology of snakes. Finally, we will examine novel or unexplained shapes and behaviors involving the head and propose questions for future investigations.
... The crowns of Keichousaurus are ornamented with apicobasal ridges (Figures 3G,H). These ridges, also present in other sauropterygians (e.g., Pliosaurus and Helveticosaurus) and some crocodylomorphs (Young et al., 2012(Young et al., , 2014a, might help pierce slippery or scaly struggling prey, facilitate blood drain, and prevent the prey from escaping (Frazzetta, 1966;Wright et al., 1979;Vaeth et al., 1985;Kardong and Young, 1996;Massare, 1997;Young et al., 2014b;McCurry et al., 2019). Plicidentine manifested as apicobasal ridges externally (Figures 3H, 5A,C; Tomes, 1878;Maxwell et al., 2012;Macdougall et al., 2014;McCurry et al., 2019) is regarded as a functional property of large predators (Scanlon and Lee, 2002;Modesto and Reisz, 2008). ...
The small-sized sauropterygian Keichousaurus hui was one of the most abundant marine reptiles from the Triassic Yangtze Sea in South China. Although Keichousaurus has been studied in many aspects, including the osteology, ontogeny, sexual dimorphism, and reproduction, the dentition of this marine reptile was only briefly described in external morphology. In this study, we provide new information on Keichousaurus tooth implantation, histology, and replacement based on a detailed examination of well-preserved specimens collected in the past decades. The tooth histology has been investigated for the first time by analyzing cross-sections of premaxillary teeth and the tooth attachment and implantation have been further revealed by X-ray computed microtomography. We refer the tooth replacement of Keichousaurus to the iguanid replacement type on the basis of the observed invasion of small replacement tooth into the pulp cavity of the functional tooth. Given the resemblance to other extinct and modern piscivorous predators in the morphology and structure of teeth, Keichousaurus might mainly feed on small or juvenile fishes and some relatively soft-bodied invertebrates (e.g., mysidacean shrimps) from the same ecosystem.
... Defensive strikes usually involve larger gape angles in which the teeth stab the offender and the head is quickly retracted (Cundall and Greene, 2000). From a predation perspective, early work revealed that some snakes may be able to modify their strike trajectories mid-strike to compensate for moving prey (Frazetta, 1966). More recent work indicates that many snake strikes are ballistic in nature and are not modified once initiated (Young and Kardong, 2007;Catania, 2009). ...
Prior to both offensive and defensive striking, snakes can display notable differences in prestrike behaviors between offensive and defensive contexts. However, few studies have investigated strike movements during the different scenarios with which snakes are faced. To better understand how snakes strike, we measured the strikes of Western Ratsnakes (Pantherophis obsoletus; N = 11) presented with two different targets: one simulated predator (a gloved human hand) and one prey (pre-killed mice). For each strike, we recorded strike distance, duration, velocity (average and peak), acceleration (average and peak), and time to start mouth gape. In both encounters, ratsnakes displayed similar time to the initiation of a mouth gape while all peak performances were significantly different between strike types with performances being higher in defensive strikes. Defensive strikes took longer (mean = 122 ± 13 ms), reached greater distances (mean = 15.1 ± 1.7 cm), had higher maximum velocities (mean = 1.80 ± 0.11 ms⁻¹), and maximum accelerations (mean = 101.4 ± 15.2 ms⁻²). Offensive strikes had much shorter durations (mean = 49 ± 5 ms), distances (mean = 4.3 ± 0.6 cm), maximum velocities (mean = 1.06 ± 0.10 ms⁻¹), and maximum accelerations (mean = 81.4 ± 18.9 ms⁻²). The results for average performance measurements are similar to those for the maximum performance comparisons. Our results show that snakes can recognize and differentiate prey from threats and respond differently in each situation. Our results also show that predatory and defensive strikes are quantitatively and situationally distinct, should be treated as separate behaviors, and therefore should be evaluated and analyzed separately from one another.
... Cranial kinesisintracranial movements in the vertebrate skull that are unrelated to the jaw joint, the middle ear or the hypobranchial skeletonis found in several groups of extant Sauropsida, including birds within the Archosauria (Bock, 1964;Zusi, 1993;Zweers, 1982), as well as ophidians (snakes) and non-ophidian squamates (lizards) within the Lepidosauria (Frazzetta, 1962(Frazzetta, , 1966Gans, 1961;Kardong, 1977;Metzger, 2002;Rieppel, 1993). Considerations on cranial kinesis in lizards go back to the works of Versluys early in the 20th century (Versluys, 1910(Versluys, , 1912(Versluys, , 1936, and since then this topic has received considerable interest. ...
Cranial kinesis refers to intracranial movements in the vertebrate skull that do not concern the jaw joint, the middle ear or the hypobranchial skeleton. Different kinds of cranial kinesis have been reported for lizards, including mesokinesis, metakinesis, amphikinesis (simultaneous mesokinesis and metakinesis) and streptostyly. Streptostyly is considered relatively widespread within lizards, whereas mesokinesis has been documented only for geckos, varanids and anguids. The present study investigated cranial kinesis in the miniaturised scincid Ablepharus kitaibelii by integrating morphological and experimental data. Based on micro computed tomography, we provide a description of skull osteology. Cranial joints were studied with histology, which results in the first detailed description of cranial joint histology for a member of the Scincidae. Taken together, the morphological data indicate a high potential for amphikinesis and streptostyly, which was also corroborated by skull manipulations. High-speed cinematography demonstrated that mesokinesis occurs during food uptake, processing and intraoral transport cycles. Bite force measurements showed prolonged and reasonably hard biting even at large gape angles. Based on these data, we formulate a model of the amphikinetic A. kitaibelii skull mechanism, which provides an extension of Frazzetta's quadric-crank model by placing a special emphasis on metakinesis. According to this model, we hypothesise that metakinetic intracranial movements may provide a means for reducing strain in jaw adductor muscles. Presented hypotheses can be addressed and tested in future studies.
... Moving the incisors to a lateral position or suppressing them entirely (as in a midline cleft) could lead to a wider effective gape, thus allowing easier capture of large insects. A similar advantage might be achieved by the sagittal mobility of the anterior palate and dental arch produced by the paramedian cleftperhaps an instance of cranial kinesis in mammals (Frazzetta, 1966). All bats with either cleft type are animalivorous (Figs 3 and 6), although there are many species of animalivorous bats lacking clefts entirely. ...
A normal feature of the facial anatomy of many species of bat is the presence of bony discontinuities or clefts,
which bear a remarkable similarity to orofacial clefts that occur in humans as a congenital pathology. These
clefts occur in two forms: a midline cleft between the two premaxillae (analogous to the rare midline
craniofacial clefts in humans) and bilateral paramedian clefts between the premaxilla and the maxillae
(analogous to the typical cleft lip and palate in humans). Here, we describe the distribution of orofacial
clefting across major bat clades, exploring the relationship of the different patterns of clefting to feeding
mode, development of the vomeronasal organ, development of the nasolacrimal duct and mode of emission of
the echolocation call in different bat groups. We also present the results of detailed radiographic and soft
tissue dissections of representative examples of the two types of cleft. The midline cleft has arisen
independently multiple times in bat phylogeny, whereas the paramedian cleft has arisen once and is a
synapomorphy uniting the Rhinolophidae and Hipposideridae. In all cases examined, the bony cleft is filled in
by a robust fibrous membrane, continuous with the periosteum of the margins of the cleft. In the paramedian
clefts, this membrane splits to enclose the premaxilla but forms a loose fold laterally between the premaxilla
and maxilla, allowing the premaxilla and nose-leaf to pivot dorsoventrally in the sagittal plane under the
action of facial muscles attached to the nasal cartilages. It is possible that this is a specific adaptation for
echolocation and/or aerial insectivory. Given the shared embryological location of orofacial clefts in bats and
humans, it is likely that aspects of the developmental control networks that produce cleft lip and palate in
humans may also be implicated in the formation of these clefts as a normal feature in some bats. A better
understanding of craniofacial development in bats with and without clefts may therefore suggest avenues for
research into abnormal craniofacial development in humans.
... A predatory lifestyle is typically accompanied by specialized adaptations to aid in prey capture and subjugation; however, these adaptations are not without constraints. For example, the highly kinetic skulls of snakes allow many of them to consume large prey, but also impose constraints on feeding behaviors (Frazzetta, 1966). In many snakes, fragile skull elements necessitate the use of the trunk and tail to aid in subduing larger and more dangerous prey upon capture (Greene, 1983). ...
We studied the effects of relative prey mass and experience on prey-handling behaviors of 16 ingestively naïve Corn Snakes (Pantherophis guttatus) feeding on different categorical sizes of live House Mice (Mus musculus) over 11 feeding trials. We randomly assigned hatchlings to two categories of prey mass, relative to snake mass (small = 20–40% and large = 41–60%), and analyzed the effects of prey mass on capture position, prey-handling method, time to subdue prey, condition of prey at ingestion, direction of ingestion, and duration of ingestion. Prey mass significantly affected prey-handling behaviors. As snakes experienced larger prey, they used more complex prey-handling behaviors (hairpin loops and constriction). Snakes that had prior large-prey experience maintained constant subduing times across feeding trials, whereas snakes that had prior experience with small prey showed an increase in subduing time across trials. Snakes feeding on large prey took longer to ingest prey than snakes feeding on small prey; however, as snakes gained feeding experience, they maintained relatively constant ingestion times across trials. All snakes employed complex prey-handling behaviors prior to the point at which the prey could vigorously defend themselves, suggesting an advantage to employing complex behaviors before they are necessary. When prey reached a certain absolute size, all were constricted and killed, regardless of prior experience or relative prey size.
... Evaluation of Burmese pythons and African rock pythons (Python sebae) revealed 2 important features regarding jaw mechanics associated with prey capture. 4 First, the skull of boids is very flexible, and protraction of the palatomaxillary arches results in lateral expansion of the maxilla and a medial pterygoid shift that clinches the palatine teeth. Second, the premaxillary and rostral maxillary teeth are the most important for initial prey seizure, especially for larger prey items. ...
CASE DESCRIPTION A 1-year-old reticulated python ( Python reticulatus ) was evaluated because of a 2-week history of wheezing and hissing.
CLINICAL FINDINGS Rostral facial cellulitis and deep gingival pockets associated with missing rostral maxillary teeth were evident. Tissues of the nares were swollen, resulting in an audible wheeze during respiration. Multiple scars and superficial facial wounds attributed to biting by live prey were apparent. Radiographic examination revealed bilateral, focal, rostral maxillary osteomyelitis.
TREATMENT AND OUTCOME Wound irrigation, antimicrobials, and anti-inflammatory drug treatment resulted in reduced cellulitis. A 3-week regimen that included empirical antimicrobial treatment and improved husbandry resulted in resolution of the respiratory sounds and partial healing of bite wounds, but radiographic evaluation revealed progressive maxillary osteomyelitis. Microbial culture of blood yielded scant gram-positive cocci and Bacillus spp, which were suspected sample contaminants. Bilateral partial maxillectomies were performed; microbial culture and histologic examination of resected bone confirmed osteomyelitis with gram-positive cocci. Treatment with trimethoprim-sulfamethoxazole was initiated on the basis of microbial susceptibility tests. Four months later, follow-up radiography revealed premaxillary osteomyelitis; surgery was declined, and treatment with trimethoprim-sulfamethoxazole was reinstituted. Eight months after surgery, the patient was reevaluated because of recurrent clinical signs; premaxillectomy was performed, and treatment with trimethoprim-sulfamethoxazole was prescribed on the basis of microbial culture of bone and microbial susceptibility testing. Resolution of osteomyelitis was confirmed by CT 11 months after the initial surgery.
CONCLUSIONS AND CLINICAL RELEVANCE Focal maxillectomies and premaxillectomy were successfully performed in a large python. Surgical management and appropriate antimicrobial treatment resulted in a good outcome.
... This cranial and postcranial disparity exceeds the morphological variation observed between congeneric species of extant snakes. The paucity of morphological differences in the skull anatomy of congeneric species of booid snakes is strikingly shown by Frazzetta's (1966) exhaustive comparisons of species of Python. He compared Python molurus (Linnaeus, 1758) and Python sebae (Gmelin, 1788), and found very few differences between them. ...
We provide a detailed anatomical description of the skull of the fossil minute boas Messelophis variatus Baszio, 2004 and Messelophis ermannorum Schaal & Baszio, 2004 from the Middle Eocene Messel Formation (Germany), as well as a cladistic analysis to infer their phylogenetic relationships. Reanalysis of new and known specimens of both species demonstrates previously unrecognized anatomical characters in the skull of these fossil snakes. Both morphological and combined (morphology plus DNA) analyses place both species of Messelophis within a clade composed of boine, ungaliophiine, and erycine taxa. Cranial features that support this systematic arrangement include a well-developed medial foot process of the prefrontal, an expanded lateral flange of the prefrontal, and a well-developed surangular crest of the compound bone, among others. As a result of the incompleteness of some crucial cranial regions, such as the basicranium, their exact relationships within this clade are currently unre-solved. Messelophis species display several contrasting traits that greatly exceed the morphological disparity found among extant genera of snakes. This cranial and postcranial anatomical variation between M. variatus and M. ermannorum demonstrates that this last species should be allocated to a new genus. Rieppelophis gen. nov. is therefore erected for the species Rieppelophis ermannorum comb. nov.
... This cranial and postcranial disparity exceeds the morphological variation observed between congeneric species of extant snakes. The paucity of morphological differences in the skull anatomy of congeneric species of booid snakes is strikingly shown by Frazzetta's (1966) exhaustive comparisons of species of Python. He compared Python molurus (Linnaeus, 1758) and Python sebae (Gmelin, 1788), and found very few differences between them. ...
We provide a detailed anatomical description of the skull of the fossil minute boas Messelophis variatus Baszio, 2004 and Messelophis ermannorum Schaal & Baszio, 2004 from the Middle Eocene Messel Formation (Germany), as well as a cladistic analysis to infer their phylogenetic relationships. Reanalysis of new and known specimens of both species demonstrates previously unrecognized anatomical characters in the skull of these fossil snakes. Both morphological and combined (morphology plus DNA) analyses place both species of Messelophis within a clade composed of boine, ungaliophiine, and erycine taxa. Cranial features that support this systematic arrangement include a well-developed medial foot process of the prefrontal, an expanded lateral flange of the prefrontal, and a well-developed surangular crest of the compound bone, among others. As a result of the incompleteness of some crucial cranial regions, such as the basicranium, their exact relationships within this clade are currently unresolved. Messelophis species display several contrasting traits that greatly exceed the morphological disparity found among extant genera of snakes. This cranial and postcranial anatomical variation between M. variatus and M. ermannorum demonstrates that this last species should be allocated to a new genus. Rieppelophis gen. nov. is therefore erected for the species Rieppelophis ermannorum comb. nov.
... The articular surfaces of the articular bones of typical snakes are saddle-shaped, the preglenoidal processes are absent, and the lower jaw displays a certain intramandibular mobility (streptognathy). The muscles of the jaw apparatus of snakes have also undergone a considerable reorganization: the first dorsal constrictor is differentiated into up to five muscles that directly control palatal movements; the external jaw adductor is divided into three independent muscles (see, e.g., Haas, 1931;Nelson, 1959a, 1959b;Gans, 1961;Frazzetta, 1966;Iordansky, 1990b). ...
The pygopod Lialis possesses the most developed cranial kinesis as compared to that in the other lizards studied. The morphological base for intensifying the cranial kinesis in Lialis was changes in the position of palatal arches and basipterygoid processes that caused alterations in palate movements. The latter allowed to increase essentially the amplitude of the cranial mechanism motions. Lialis preserved the amphikinetic skull and jaw muscle construction that is inherent for all Gekkota lizards. On the contrary, the intensification of cranial kinesis in snakes proceeded due to the profound rearrangement of skull (substitution of amphikinesis for prokinesis) and jaw musculature. Probably, these distinctions resulted from the different initial construction of the jaw apparatus in ancestors of pygopods and snakes. In the process of evolution of snakes, the consolidation of the braincase might precede the intensification of the intracranial mobility. The ways of intensifying organ functions are discussed.
The skull of vipers is a highly kinetic anatomical structure involved in envenomating and consuming of prey. Morphological knowledge about the viperid skull is based on studies on some groups of species, but information on its variation within the whole family and its functional morphology is still scarce. In this study, we aimed to explore variation in skull morphology among species of the three subfamilies of Viperidae, and test whether that variation correlates with macrohabitat and diet. We performed quantitative analyses of the viperid skull based on broad taxonomic sampling and two methodological approaches: linear and geometric morphometrics. The results of both approaches showed that much of the variation lies in differences of shape and relative size of the premaxilla, the nasals, the frontals, and the parietals. The results indicated that phylogeny and size influence the shape of the skull, but we also found evidence of morphological differentiation between arboreal and terrestrial species and in species with mammal specialist diet. Our findings imply that, besides evolutionary allometry and phylogenetic signal, demands of particular diets coupled with use of certain habitats have in part shaped morphological evolution of the viperid skull.
Snakes comprise nearly 4,000 extant species found on all major continents except Antarctica. Morphologically and ecologically diverse, they include burrowing, arboreal, and marine forms, feeding on prey ranging from insects to large mammals. Snakes are strikingly different from their closest lizard relatives, and their origins and early diversification have long challenged and enthused evolutionary biologists. The origin and early evolution of snakes is a broad, interdisciplinary topic for which experts in palaeontology, ecology, physiology, embryology, phylogenetics, and molecular biology have made important contributions. The last 25 years has seen a surge of interest, resulting partly from new fossil material, but also from new techniques in molecular and systematic biology. This volume summarises and discusses the state of our knowledge, approaches, data, and ongoing debates. It provides reviews, syntheses, new data and perspectives on a wide range of topics relevant to students and researchers in evolutionary biology, neontology, and palaeontology.
Five unrelated adult Colombian boas (Boa imperator) presented with a 1- to 3-mon history of unilateral rostral swelling of the maxilla associated with a chronic rubbing against the enclosure's walls. Moderate to severe gingival inflammation and ulceration of the labial mucosa were present at the level of the swelling with tenderness to the touch. Radiography revealed osteolytic or proliferative lesions of the maxillary bone. Chronic maxillary osteomyelitis was diagnosed. Unilateral maxillectomy was performed on each animal under general anesthesia. Local anesthesia was also achieved by infiltrating lidocaine along the medial and lateral aspect of the maxillary gingiva and at the level of the maxillo-ectopterygoid joint. Using a lateral gingival approach, the maxillo-prefrontal, maxillary-palatine, and maxillo-ectopterygoid attachments were transected, and the maxillary bone removed. Histologic examination revealed pyogranulomatous stomatitis and osteomyelitis in all snakes, and presence of intralesional bacteria (n = 3 snakes). Gram-negative bacteria (Chryseobacterium indologenes and Proteus mirabilis) were cultured from the resected tissue of two snakes. One snake suffered from wound dehiscence 5 d postoperatively. All snakes were fed 15 d postoperatively and ingested dead mice without apparent difficulties. One snake was examined 2 mon and 1 yr after surgery, with no evidence of soft tissue or osseous infection and only minor facial scaring; all other snakes were lost to follow-up 15 d after surgery. Unilateral maxillectomy was performed in a cohort of five Colombian boas suffering from maxillary osteomyelitis. This surgical technique should be considered as an alternative to medical treatment in boid snakes.
Snakes comprise nearly 4,000 extant species found on all major continents except Antarctica. Morphologically and ecologically diverse, they include burrowing, arboreal, and marine forms, feeding on prey ranging from insects to large mammals. Snakes are strikingly different from their closest lizard relatives, and their origins and early diversification have long challenged and enthused evolutionary biologists. The origin and early evolution of snakes is a broad, interdisciplinary topic for which experts in palaeontology, ecology, physiology, embryology, phylogenetics, and molecular biology have made important contributions. The last 25 years has seen a surge of interest, resulting partly from new fossil material, but also from new techniques in molecular and systematic biology. This volume summarises and discusses the state of our knowledge, approaches, data, and ongoing debates. It provides reviews, syntheses, new data and perspectives on a wide range of topics relevant to students and researchers in evolutionary biology, neontology, and palaeontology.
Recent phylogenetic analyses differ in their interpretations of the origin and interrelationships of snakes, resulting in polarized views of snake ecology, habit and acquisition of features associated with wide-gaped feeding (macrostomy). Here, we report a new specimen of the Late Cretaceous nest predator Sanajeh indicus that helps to resolve the origin of macrostomy. The new specimen preserves an ossified upper temporal bar and a posteriorly expanded otooccipital region that lacks a free-ending supratemporal bone and retains a lizard-like palatomaxillary arch that allows limited movements during swallowing. Phylogenetic analyses of a large-scale total evidence dataset resolve Sanajeh near the base of Pan-Serpentes, as the sister group of Najash, Dinilysia and crown-group Serpentes. The Cretaceous Tetrapodophis and Coniophis represent the earliest-diverging members of Pan-Serpentes. The Cretaceous hindlimbed pachyophiids and Cenozoic Australian 'madtsoiids' are inside crown Alethinophidia, whereas mosasaurs are recovered invariably within anguimorphs. Our results suggest that the wide-gape condition in mosasaurs and snakes might have evolved independently, as functionally distinct mechanisms of prey ingestion. The intermediate morphology preserved in Sanajeh indicates that ingestion of large prey items (macrophagy) preceded wide-gaped, unilateral feeding (macrostomy), which appeared 35 Myr later, in the common ancestor of pachyophiids, Cenozoic Australian 'madtsoiids' and alethinophidians.
Soft Robotics offers an opportunity to fabricate more adapt-
able systems to be used outside industrial areas. For practical applications of soft robots, their active parts should achieve high forces and considerable displacements, keeping the structures lightweight, modular, and easy to fabricate. Consequently, robust and predictable motion actuators with easy manufacture are required. This paper applies the origami concept to address a 3D printed low-weight modular soft pneumatic linear actuator denoted ORI-Structure. The presented structure has a high
contraction rate (up to 52.5%) and can lift 1161.64x its weight. Additionally, we present a more complex module with 3 DOF formed with the ORI-Structure. The module can displace linearly with a high-contraction rate (up to 52.5%), and it can rotate in two axes up to 42°. In both cases, the module exhibits high-lifting capabilities (611.53x its weight). In both cases, simulation and experiments are introduced to describe the design parameters and their performances.
Large constrictor snakes, referred to the genera Palaeopython and Paleryx, are an ecologically prominent part of the fauna of Europe during the Paleogene. Most species were named over a century ago and their taxonomy is largely based on isolated vertebrae. Furthermore, the majority of named taxa originate from imprecisely known localities within the Phosphorites du Quercy, in southern France, and thus their exact age is not known. We critically review and re-diagnose these genera based on personal examination of all existing type material, an array of new specimens, and a detailed literature review. We consider Palaeopython and Paleryx to be valid and propose vertebral characters to distinguish them. We recognize three valid species of Palaeopython , i.e. Palaeopython cadurcensis (type species) from the Phosphorites du Quercy, Palaeopython ceciliensis from Geiseltal, and Palaeopython helveticus from Dielsdorf (Switzerland), and one valid species of Paleryx , i.e. Paleryx rhombifer (type species) from Hordle Cliff (England). Four other species, which were previously treated as members of Palaeopython and Paleryx , i.e. “Palaeopython” filholii and “Palaeopython” neglectus from the Phosphorites du Quercy, “Palaeopython” fischeri from Messel, and “Paleryx” spinifer from Geiseltal, are also considered as valid but pertain to other genera. Among these four taxa, “Palaeopython” fischeri has been recently assigned to its own genus, Eoconstrictor . A new genus, Phosphoroboa gen. nov. is established to accommodate “Palaeopython” filholii . We designate a lectotype for Palaeopython cadurcensis and establish that the paralectotype maxilla and dentary are reasonably referred to this species. New material attributed to Palaeopython cadurcensis is described from the old collections of the Phosphorites du Quercy. Paleryx cayluxi , another species established from the old collections of the Phosphorites du Quercy, is synonymized here with Palaeopython cadurcensis . We further clarify important errors in the original description and figures of Paleryx cayluxi , identify the exact specimens that comprise the type series, and designate a lectotype. Much new material is described for Palaeopython ceciliensis from its type area in Geiseltal and intracolumnar variation is considered. We describe additional vertebral and cranial material of Paleryx rhombifer from its type area in Hordle Cliff. Based on this cranial material, we suggest non-booid affinities for Paleryx rhombifer. We designate a lectotype for Paleryx depressus and agree with its previous suggested synonymy with Paleryx rhombifer . We re-describe the lectotype and paralectotypes of “Palaeopython” neglectus and refer and describe new material of this species from the Phosphorites du Quercy, paying special attention to intracolumnar variation; we also defer a decision on its generic relations until more abundant and complete material can be studied. We describe new vertebral material of the booid Eoconstrictor cf. fischeri from Geiseltal; similar material was previously known only from Messel and Dielsdorf. We determine that Eoconstrictor fischeri contains two distinct and unrelated species and describe intracolumnar variation in the nominotype. We clarify certain issues regarding the type series of Paleryx spinifer , designate a lectotype, and report previously unrecognized cranial material associated with the latter specimen; we transfer this species to Eoconstrictor based on cranial features and recombine it as Eoconstrictor spinifer comb. nov. We finally describe much new vertebral and cranial material of Phosphoroboa filholii comb. nov. from the Phosphorites du Quercy (both from the old collections but also from the late Eocene localities of Escamps A and C), paying special attention to intracolumnar variation. Based on this cranial material from Escamps, we identify Phosphoroboa gen. nov. as a booid. An analytical approach is undertaken in many isolated remains in order to quantify vertebral structures and assess intracolumnar variation, as well as associating isolated cranial elements to vertebral-based taxa. 3D models of the type material of the Geiseltal and Messel taxa are presented. The importance of vertebrae in the taxonomy of fossil Constrictores is addressed, although it is acknowledged that it is cranial material that can afford the most reliable phylogenetic conclusions. The diversity, distribution, biogeographic origins, and final demise and extinction of large Constrictores in the Paleogene of Europe are discussed.
Chironius is one of the most speciose genera of the South American colubrid snakes. Although the genus represents a well-known radiation of diurnal racers, its monophyly, affinities with other Neotropical colubrid genera, and intrageneric relationships are open questions. Here, we present a phylogenetic analysis of Chironius based on a data matrix that combines one nuclear (c-mos) and two mitochondrial (12S and 16S rRNA) genes with 37 morphological characters derived from scutellation, skull, and hemipenial features. Phylogenetic relationships were inferred using maximum parsimony (MP) and maximum likelihood (ML). Our combined morphological and molecular analyses strongly support the monophyly of the genus Chironius and its sister-group relationship with a clade formed by the genera Dendrophidion and Drymobius. Phylogenetic relationships within the genus Chironius is still controversial, although five clades are retrieved with medium to strong support. © 2014 The Linnean Society of London
The Dissection of Vertebrates provides students with a manual combining pedalogical effective text with high-quality, accurate, and attractive visual references. Using a systemic approach within a systematic framework for each vertebrate, this book covers several animals commonly used in providing an anatomical transition sequence. Seven animals are covered: lamprey, shark, perch, mudpuppy, frog, pigeon and cat. New to this edition: - Revision of the systemic section of the introductory chapter to maintain currency - Corrections to several parts of the existing text and images - New comparative skull sections included as part of the existing vertebrates - Companion site with image bank * Winner of the NYSM Jury award for the Rock Dove Air Sacs, Lateral and Ventral Views illustration * Expertly rendered award-winning illustrations accompany the detailed, clear dissection direction * Organized by individual organism to facilitate classroom presentation * Offers coverage of a wide range of vertebrates * Full-color, strong pedagogical aids in a convenient lay-flat presentation * Expanded and updated features on phylogenic coverage, mudpuppy musculature and comparative mammalian skulls.
Snakes mostly prey on living animals which are swallowed whole. Snakes kill prey by biting (sometimes with envenomation) or by constriction, which causes asphyxiation. The dentitions are homodont and consist of very sharp, recurved teeth firmly ankylosed to the jaw bones. The cranium is robustly constructed and has no mobile intracranial joints as in lizards. However, the upper jaw bones display considerable mobility and are connected by ligaments. The posterior elements of the lower jaw are fused but the jaw rami are separable at the symphysis. These properties facilitate swallowing of prey, which is often large in relation to the gape. Most snakes are nonvenomous but some employ venom to kill or immobilize prey. The venom is produced by modified salivary glands and is delivered by way of enlarged teeth (fangs) which possess grooves on the external surface, or are even hollow, and hence provide conduits for venom.
The Atheriniformes is an order of teleost fish which consists of the Atherinoidei (sand smelts etc.), Cyprinodontoidei (tooth‐carps) and Exocoetoidei (halfbeaks etc.). Some of its members have protrusible upper jaws and some do not. Photographs have been taken of two species of Cyprinodontoidei feeding, to discover how they use their jaws, which are protrusible. The anatomy and mechanisms of the jaws of these and of various other Atheriniformes have been studied. The terminology of the kinematics of machines is used in a general discussion of the mechanisms of teleost jaws. Anatomical similarities between the jaws of Acanthopterygii, Cyprinoidei and Atheriniformes are noted and discussed.
The academic world is full of people with rich personalities, brilliant minds, and eclectic interests. Thomas (T. H.) Frazzetta certainly was a special one of these. He passed away on New Year's Eve 2015, following several months of ill health. Ironically, New Year's Eve was one of his favorite holidays, only exceeded by Halloween. Sadly, he was unable to celebrate either in his final year.
We compared the head skeleton (skull and lower jaw) of juvenile and adult specimens of five snake species [Anilios (=Ramphotyphlops) bicolor, Cylindrophis ruffus, Aspidites melanocephalus, Acrochordus arafurae, and Notechis scutatus] and two lizard outgroups (Ctenophorus decresii, Varanus gilleni). All major ontogenetic changes observed were documented both qualitatively and quantitatively. Qualitative comparisons were based on high-resolution micro-CT scanning of the specimens, and detailed quantitative analyses were performed using three-dimensional geometric morphometrics. Two sets of landmarks were used, one for accurate representation of the intraspecific transformations of each skull and jaw configuration, and the other for comparison between taxa. Our results document the ontogenetic elaboration of crests and processes for muscle attachment (especially for cervical and adductor muscles); negative allometry in the braincase of all taxa; approximately isometric growth of the snout of all taxa except Varanus and Anilios (positively allometric); and positive allometry in the quadrates of the macrostomatan snakes Aspidites, Acrochordus and Notechis, but also, surprisingly, in the iguanian lizard Ctenophorus. Ontogenetic trajectories from principal component analysis provide evidence for paedomorphosis in Anilios and peramorphosis in Acrochordus. Some primitive (lizard-like) features are described for the first time in the juvenile Cylindrophis. Two distinct developmental trajectories for the achievement of the macrostomatan (large-gaped) condition in adult snakes are documented, driven either by positive allometry of supratemporal and quadrate (in pythons), or of quadrate alone (in sampled caenophidians); this is consistent with hypothesised homoplasy in this adaptive complex. Certain traits (e.g. shape of coronoid process, marginal tooth counts) are more stable throughout postnatal ontogeny than others (e.g. basisphenoid keel), with implications for their reliability as phylogenetic characters.
Die Nahrung der Vertebraten reicht von mikroskopisch kleinen Diatomeen oder Algen bis zu sehr großen Beutetieren, von passiven Pflanzen oder beinahe passiver Beute (die meisten Mollusken) bis zu sehr aktiver, von nährstoffreichen Insekten oder Würmern zu nährstoffarmen Halmen, von verteidigungslosen Lebewesen zu geschützten, und von im Überfluss vorhandenen bis zu hochgradig begrenzten Ressourcen (z. B. der Nektar von nur ganz bestimmten Blüten). Die Nahrung kann saisonal oder immer zur Verfügung stehen, sie kann zahlreich sein oder selten, und es kann Nahrungskonkurrenz bestehen oder auch nicht. Es ist also nicht verwunderlich, dass die Wege, auf denen die Wirbeltiere ihre Nahrung lokalisieren und gewinnen, extrem variabel sind.
The venomous function of Squamates plays an important role in the capturing and the retaining of their preys, and the digestion of them by means of enzymatic destruction. The biting apparatus contains the following components: Poison glands which are derived from serous salivary glands belonging to the labial group and in some cases there is a muscular compressing mechanism to facilitate the emptying of these glands. Jaws and a tooth arrangement with a more or less specialised function (fangs that may be solid, splined or canaliculate). A possible peri-oral skeleton structure (cranial kinetics) and protractor and retractor maxillopalatine muscles.
Inspired by the bite and swallowing function of a snake’s mouth, a robot end‐effector grabbing mechanism was designed. The grabbing movement is realized by the ‘bite’ function of the bionic snake mouth actuator, and the ‘swallowing’ function insures a continuous grip on the object. To implement the continuous grip function of the new robot end‐effector, the complex motion of a snake’s mouth is simplified into three basic movements based on the anatomy of a snake’s mouth and with a combination of bionics and engineering. The upper jaw consists of a double four‐bar linkage mechanism and the lower jaw mechanism implementing a lateral expansion function are the two elements of the robot end‐effector. The relationship model and the corresponding curves of the actuating force and gripping force are necessary to implement an open‐loop control of the robot end‐effector. Through analysis and simulation, linkage parameters are determined to implement the desired motion.
SYNOPSIS. Most snakes ingest and transport their prey via a jaw ratcheting mechanism in which the left and right upper jaw arches are advanced over the prey in an alternating, unilateral fashion. This unilateral jaw ratcheting mechanism differs greatly from the hyolingual and inertial transport mechanisms used by lizards, both of which are characterized by bilaterally synchronous jaw movements. Given the well-corroborated phylogenetic hypothesis that snakes are derived from lizards, this suggests that major changes occurred in both the morphology and motor control of the feeding apparatus during the early evolution of snakes. However, most previous studies of the evolution of unilateral feeding mechanisms in snakes have focused almost exclusively on the morphology of the jaw apparatus because there have been very few direct observations of feeding behavior in basal snakes. In this paper I describe the prey transport mechanisms used by representatives of two families of basal snakes, Leptotyphlopidae and Typhlopidae. In Leptotyphlopidae, a mandibular raking mechanism is used, in which bilaterally synchronous flexions of the lower jaw serve to ratchet prey into and through the mouth. In Typhlopidae, a maxillary raking mechanism is used,, in which asynchronous ratcheting movements of the highly mobile upper jaws are used to drag prey through the oral cavity. These findings suggest that the unilateral feeding mechanisms that characterize the majority of living snakes were not present primitively in Serpentes, but arose subsequently to the basal divergence between Scolecophidia and Alethinophidia.
Constriction is a prey-immobilization technique used by many snakes and is hypothesized to have been important to the evolution and diversification of snakes. However, very few studies have examined the factors that affect constriction performance. We investigated constriction performance in ball pythons (Python regius) by evaluating how peak constriction pressure is affected by snake size, sex, and experience. In one experiment, we tested the ontogenetic scaling of constriction performance and found that snake diameter was the only significant factor determining peak constriction pressure. The number of loops applied in a coil and its interaction with snake diameter did not significantly affect constriction performance. Constriction performance in ball pythons scaled differently than in other snakes that have been studied, and medium to large ball pythons are capable of exerting significantly higher pressures than those shown to cause circulatory arrest in prey. In a second experiment, we tested the effects of experience on constriction performance in hatchling ball pythons over 10 feeding events. By allowing snakes in one test group to gain constriction experience, and manually feeding snakes under sedation in another test group, we showed that experience did not affect constriction performance. During their final (10th) feedings, all pythons constricted similarly and with sufficiently high pressures to kill prey rapidly. At the end of the 10 feeding trials, snakes that were allowed to constrict were significantly smaller than their non-constricting counterparts. J. Exp. Zool. 9999A:XX-XX, 2016. © 2016 Wiley Periodicals, Inc.
To realize open bite and swallows movements of the snake mouth. Bionic snake mouth mechanism was designed based on the anatomy of snake mouth and the combination of bionics and engineering, and the motion of snake mouth was divided into three basic movements. Mechanism kinematic analysis was made and linkage parameters were determined for implementing the motion of snake mouth. Then the virtual model was made and the desired motion was realized.
Studies of previous authors on snake skull embryogenesis have been performed on embryos obtained from eggs after oviposition. The aim of this study was to investigate the initial stages of chondrocra-nium development in Grass snake Natrix natrix Linnaeus, 1758, embryos before oviposition. Natrix natrix embryos at early developmental stages (24–27 according to the table of normal development by D. Zehr (1962)) were obtained by means of caesarean section. At developmental stages 25–27, previously undescribed structures were found in the region of future skull formation. These structures exist during one or two stages and then disappear. Therefore, we call them “temporary structures.” The assumption about the nature of these structures is based on their topography and comparison with the structures of developing or fully formed chondrocranium in other vertebrates. It is hypothesized that the temporary structures in Natrix natrix chon-drocranium are vestiges of primary chondrocranium of ancestral vertebrate forms, and they indicate the exist-ence of several variants in the formation of chondrocranium in the historical vertebrates’ development.
Snakes are a highly derived group of squamates, and unlike many other tetrapods, intraoral transport of prey does not involve the tongue. Using a general model of tetrapod feeding as a reference, we sought to identify which features of feeding were conserved and which modified in snakes. Three basic sets of predictions were made for muscle activity, jaw kinematic profiles, and hyoid displacement. These predictions were then tested using electromyography, direct measurement of the gape, and cineradiography in the reticulated python. In pythons, feeding is commonly unilateral, where left and right jaws move independently. We found that activity of cranial and cervical muscles includes some conservative components (depressor mandibulae), but also some departures from the general tetrapod model (adductors, cervical). The jaw kinematic profile is also modified during the open phase, but conserved during the close phase. The hyoid exhibits no significant anteroposterior displacement correlated with jaw open phase. We conclude, and formally present in a model of snake feeding, that intraoral transport of prey is highly derived in snakes. Modifications within snake jaw muscles, kinematics, and hyoid displacement are correlated with the absence of tongue use in prey transport and to the unilateral pattern of jaw advance.
The hyolingual system of Squamata is a highly versatile system used in different feeding, drinking, chemoreception, and social behaviors. In each of these activities, either the entire hyolingual system or one of its elements is used. For instance, in the majority of lizards, the tongue acts as the main element for liquid uptake, intraoral food and liquid transport, and in chemoreception, whereas the hyoid apparatus plays a major role during social interactions by acting on the ventral floor of the throat. In varanids, the hyoid apparatus is involved in both deglutition of foods and liquids, and during social displays.
Body elongation and limblessness have evolved significantly within Tetrapoda, typically associated with aquatic, fossorial, crevice dwelling, or grass-swimming lifestyles. Some lineages of secondarily elongate vertebrates (for example, limbless skinks) have solved the concomitant problem of reduction in size of the feeding apparatus by eating many tiny items, whereas others (for example, some caecilians) shear ingestible chunks out of large prey. Many advanced snakes achieved a third solution by radically restructuring their heads and feeding infrequently on large items; perhaps not coincidentally. Among limbless squamate reptiles, only Serpentes has achieved substantial adaptive radiation and high species richness. More than 2,500 species of living snakes inhabit most temperate and tropical land masses, and they often are prominent predators in terrestrial, arboreal, fossorial, aquatic, and even marine faunas. Snakes eat prey as different as onycophorans, fish eggs, centipedes, cormorants, and porcupines; many species commonly consume individual items weighing 20% of their own mass, and some venomous species occasionally subdue and eat prey that exceed their own mass by as much as 50%. This chapter first briefly surveys snake diversity and then examines in detail the functional and morphological aspects of capturing, swallowing, and processing prey that generally characterize relatively derived subgroups. It only touches on sensory aspects of feeding.
Anatomie de l'appareil de la morsure chez “Eunectes murinus” (Boidae). Osteologie, myologie, vaisseux et nerfs
- Anthony J.
Herpetological results of the Vernay Angola expedition
- Bogert C. M.
Field notes on some Gold Coast snakes
- Cansdale G. S.
Mémoire sur les caractères tirés de l'anatomie pour distinguer les serpens venimeux des serpens non venimeux
- Duvernoy M.
Versuch einer functionellen Analyse des Giftbisses und Schlingaktes von Lachesis gramineus
- Haas G.
Über die Schädelmechanik und die Kiefermuskulatur einiger Proteroglypha
- Haas G.
The head muscles of the genus Causus (Ophidia, Solenoglypha) and some remarks on the origin of the Solenoglypha
- Haas G.
Die Kiefermuskeln der Schlangen und ihre Beziehungen zu den Speicheldrüsen
- Hager K. P.
Osteologie des Schlangenkopfes
- Radovanovic M.
Particularites anatomiques de l'appareil de la morsure chez “Constrictor constrictor” et chez “Epicrates crassus” (Boidae)
- Anthony J.
Der Giftapparat der Schlangen mit besonderer Berüchsichtigung der Naja tripudians
- Radovanovic M.
The herpetology of Southern Rhodesia. Part I. Snakes
- Broadley D. G.
Beschreibung des Muskelsystems eines Python bivittatus
- D'Alton E.
The feeding habits of serpents
- Ditmars R. L.
Studies on the morphology and function of the skull in the Boidae (Serpentes). Part I. Cranial differences between Python sebae and Epicrates cenchris.
- Frazzetta T. H.
Mechanik des Bisses der Solenoglyphen Giftschlangen
- Katheriner L.
Anatomische studien am Schlangenkopf
- Radovanovic M.