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Bite me: Biomechanical models of theropod mandibles and implications for feeding behavior
Abstract
A biomechanical approach is used to study feeding behavior in non-avian theropods. Mandibles can be modeled as beams undergoing bending loads during food ingestion. The bite force applied at any given point along the mandible should be proportional to the external dimensions of the mandibular ramus at that location. Thus, patterns of variation in these dimensions reflect the adaptation of the jaw to specific loads, which are related to the method of killing prey. These beam models were compared to those of the extant varanids Varanus komodoensis (Komodo dragon, an ambush predator with a slashing bite) and Varanus niloticus (Nile monitor, molluscivorous) to gain insight into the feeding behavior of theropods.
On the basis of our results, we identified five distinct theropod feeding categories: (1) the allosauroid "Antrodemus valens" and the abelisaurids Majungatholus atopus and Carnotaurus sastrei share the mandibular properties of the Komodo dragon, and these shared properties, combined with the similarity between the craniodental morphology of "Antrodemus" and Majungatholus and that of the varanid, suggest that they were probably large-prey hunters delivering slashing bites; (2) dromaeosaurids have mandibular properties reminiscent of those of V. komodoensis for slashing bites, but differences can be identified between Dromaeosaurus and velociraptorines, the former having a stronger bite than the latter, suggesting that it possibly relied more on its jaws to capture and kill prey; (3) Suchomimus tenerensis and Dilophosaurus wetherilli exhibit mandibular adaptations related to the capture of prey smaller than themselves, the former probably practicing a bite-and-hold strategy and the latter finishing its prey with slashing bites; (4) Ceratosaurus nasicornis, Allosaurus fragilis, Acrocanthosaurus atokensis, and Giganotosaurus carolinii demonstrate adaptations of the anterior extremity of the mandible for capturing prey and delivering powerful bites to bring down prey or deliver the final blow; and (5) tyrannosaurids, unlike other theropods, exhibit mandibular adaptations to resist high torsional stresses at the anterior of the mandible induced during prey capture, bone crushing, or both.
The mandibular models were also used to infer relative bite force in theropods. Velociraptorines appear to have had a maximum bite force similar to that of V. komodoensis, whereas that of Dromaeosaurus was three times as great. Suchomimus, Allosaurus, "Antrodemus," and Ceratosaurus were capable of exerting maximum bite forces as great as A. mississippiensis, and those of abelisaurids and Albertosaurus were twice as powerful. Among the largest theropods, Acrocanthosaurus and Giganotosaurus were surpassed by Daspletosaurus and Tyrannosaurus. The high estimates obtained for tyrannosaurids are consistent with previously published values that suggest bone-cracking abilities.
Growth series for Allosaurus fragilis, Albertosaurus sarcophagus, Gorgosaurus libratus, and Tyrannosaurus rex were also studied in order to determine whether mandibular properties changed during ontogeny. Significant changes were observed in Allosaurus, especially in bending rigidity, indicating that juveniles did not feed the same way as adults; juveniles probably delivered simple slashing bites. Unfortunately, the question of parental care in Allosaurus cannot be resolved in light of our results. The mandibular properties of tyrannosaurids were not found to vary significantly during ontogeny, other than in terms of bite force. This finding strongly suggests that juveniles were apt predators, capable of subduing their own prey rather than relying on carrion or parental care to survive.
... In this work, mandibular strength properties of various troodontid taxa are derived through employing the biomechanical modelling technique using the principles of beam theory (Therrien et al. 2005), which has been used on a variety of non-avian theropods (Therrien et al. 2005(Therrien et al. , 2021Jasinski 2011;Monfroy 2017;Yun 2024), to determine the patterns of resisting loads from vertical and horizontal directions along the lower jaw in these dinosaurs. Since the external dimensions of various points along the mandible reflect adaptation of the jaw to specific loads, they are likely related to the hunting and feeding methods of the animal, and can be used to infer behaviours of extinct taxa (Therrien et al. 2005). ...
... In this work, mandibular strength properties of various troodontid taxa are derived through employing the biomechanical modelling technique using the principles of beam theory (Therrien et al. 2005), which has been used on a variety of non-avian theropods (Therrien et al. 2005(Therrien et al. , 2021Jasinski 2011;Monfroy 2017;Yun 2024), to determine the patterns of resisting loads from vertical and horizontal directions along the lower jaw in these dinosaurs. Since the external dimensions of various points along the mandible reflect adaptation of the jaw to specific loads, they are likely related to the hunting and feeding methods of the animal, and can be used to infer behaviours of extinct taxa (Therrien et al. 2005). ...
... In this work, mandibular strength properties of various troodontid taxa are derived through employing the biomechanical modelling technique using the principles of beam theory (Therrien et al. 2005), which has been used on a variety of non-avian theropods (Therrien et al. 2005(Therrien et al. , 2021Jasinski 2011;Monfroy 2017;Yun 2024), to determine the patterns of resisting loads from vertical and horizontal directions along the lower jaw in these dinosaurs. Since the external dimensions of various points along the mandible reflect adaptation of the jaw to specific loads, they are likely related to the hunting and feeding methods of the animal, and can be used to infer behaviours of extinct taxa (Therrien et al. 2005). Additionally, the results are compared with those of the previous biomechanical studies on other theropods, to test the likelihood that the ecology of troodontids differed from similarly-sized theropods (e.g. ...
Troodontids are small-bodied paravian theropod dinosaurs that are conspicuous for their close evolutionary relationship with modern birds and unique bauplan among Mesozoic non-avian theropods, part of which has been interpreted as suggestive of a distinctive ecological niche as highly cursorial predators who primarily hunted small prey items or of an increased portion of plant material in their diet compared to other theropods. Despite the increased interest in paleobiology of bird-like dinosaurs more recently, however, feeding biomechanics of troodontids remains largely uninvestigated. Here, the feeding and predatory behaviours of five troodontids are investigated, using beam theory on their mandibles. Mandibular strength profiles reveal that the anterior extremity of the jaws in troodontids, even in early-diverging forms, is better adapted to endure mediolateral and torsional loads compared to most other theropods such as dromaeosaurids. In later-diverging, relatively large-bodied taxa, the anterior half of the dentary is strengthened in terms of its mediolateral bending rigidity. Such unique profiles suggest the anterior part of the lower jaw played an important role in the life habits of troodontids. These results could be interpreted that the anterior region of the troodontid dentary was used to crop off plant material, or assisted in prey capture when the prey was subdued by the pes of an animal.
... Ceratosaurs are theropod dinosaurs that include two highly diverse clades, Noasauridae and Abelisauridae, which evolved and persisted until the mass extinction of non-avian dinosaurs [8][9][10]. These groups are diverse in their morphology [11][12][13][14], ecology [13,15,16], ornamentation [17] and body size [18]. Whereas, previous studies [18,19], have suggested that Abelisauridae followed Cope´s rule and Noasauridae decreased in body size towards the phylogeny, recent discoveries of new abelisaurids [11,[20][21][22] and the absence of a comprehensive analysis that include ecological, phylogenetic and socio-sexual factors make it necessary to reevaluate body size evolution in Ceratosauria under a modern phylogenetic comparative approach. ...
... "Ecology category" consists of two factors: Specialist feeding behavior (SFB) and Generalist feeding behavior (GFB). These level were based on previously published hypothesis that proposed that Late Cretaceous abelisaurids had a specialist predation strategy based on morphological features in skull and vertebrae [13,22,33] and biomechanical studies [15,16]. This specialized feeding strategy involved primarily the use of primarily the head for hunting, with a short distance sprint, and holding the prey during the kill [13,34]. ...
... Despite different feeding strategy were hypothesized for different abelisaurids (i.e. Majungasaurus and Carnotaurus) [15,16], all Late Cretaceous abelisaurids were classified as SFB due to their phylogenetic affinities and shared anatomical and functional traits. On the other hand, taxa lacking these specific features were grouped into the "generalist" level (GFS). ...
Patterns of body size evolution in dinosaurs are relevant for understanding the evolutionary trends that have shaped the disparity of phenotypes observed in the fossil record. In this sense, previous studies have suggested that Abelisau-ridae followed Cope´s rule and Noasauridae exhibited a phylogenetic trend towards decreasing body size. However, the absence of a comprehensive analysis including ecological, phylogenetic and socio-sexual factors make it necessary to reevaluate body size evolution in Ceretatosauria under a modern phylogenetic comparative approach. Therefore, we aimed to test whether body size evolved in Ceratosauria in accordance with Cope´s rule, evaluate what factors best explain differences in body size within Ceratosauria and examine what patterns of evolution rates, selection strength and constrain explain the diversification body size in Ceratosauria. Differences in body size were found between specialized taxa (= Late Cretaceous abelisaurids) and "generalized taxa" (= Outgroups + Noasauridae). This results suggested that the presence of a specialized feeding strategy in Late Cretaceous abelisaurids was associated with differences in body size, regardless of the phylogenetic topology and evolutionary model used. Additionally, the low levels of morphological disparity, low evolutionary rates for taxa with a specialist feeding behavior in Brown-ian motion model and the fossil record suggest that the evolution of body size in Late Cretaceous abelisaurids was constrained. The cursorial abilities suggested for abelisaurids joined with the specialized predation strategy could have constrained the increase in body size in Late Cretaceous abelisaurids after the extinction of carcharodontosau-rids. On the other hand, Noasauridae exhibited a phylogenetic trend towards decreased body size, likely to avoid niche overlap with medium size theropods and minimize structural and maintenance cost while living in stressful environments and having a generalist diet. Understanding how the dynamics of dinosaur communities, such as competition and predator-prey interactions, operated in South America during the Late Cretaceous is crucial for reconstructing the evolutionary and ecological processes that shaped its unique faunal assemblage. Futures works should be focus on process-based community-evolution model and species distribution modeling to further understand the macroevolution dynamics of South America dinosaur community.
... Many distinctive cranial and postcranial traits characterize abelisaurids and set them apart from other theropod groups 12 . Their skull is typically tall, short, and ornamented, with a highly kinetic intramandibular articulation 3,13,14 . Some anatomical and biomechanical studies of the skull and vertebral column, especially in the cervical area, suggest that Late Cretaceous abelisaurids had a specialized predatory strategy 3,13,14 . ...
... Their skull is typically tall, short, and ornamented, with a highly kinetic intramandibular articulation 3,13,14 . Some anatomical and biomechanical studies of the skull and vertebral column, especially in the cervical area, suggest that Late Cretaceous abelisaurids had a specialized predatory strategy 3,13,14 . This specialized feeding strategy involved primarily the use of the head for hunting, with a short distance sprint, and holding the prey during the kill 3,15 . ...
... This specialized feeding strategy involved primarily the use of the head for hunting, with a short distance sprint, and holding the prey during the kill 3,15 . This strategy has been attributed to taxa with the following features: (1) high bit force, (2) short, broad, and tall skull, (3) short hindlimbs, (4) tendency towards hypermineralization and fusion of skull elements, (5) expanded occiput and neck musculature, and 6) skull resistance to torsional bending 13,14 . On the other hand, a generalist feeding strategy involves strike and tear bites to generate fatal bounds, gradually wearing down the prey to death 3,15 . ...
Abelisauridae is a clade of theropods distinguished by short, ornamented skulls and strongly reduced forelimbs. They represented the most abundant predatory dinosaurs in Gondwana during the Cretaceous. Bolstered by biomechanical studies, the morphology of the skull and vertebral column of abelisaurids, have led researchers to hypothesize that Late Cretaceous forms were “specialized hunters.” Here, we use the morphology of the abelisaurid maxilla to test the inclusion of the Lower Cretaceous Spectrovenator within the specialized hunter category. Additionally, we analyze the diversity and disparity of the abelisaurid maxilla in a macroevolutionary context. We quantified the maxillary shape in 17 taxa using 2D geometric morphometrics and analyzed different evolutionary scenarios and trends with phylogenetic comparative methods. The results of all the analyses (phylogenetic ordination methods, Z, and R² comparison in phylogenetic generalized least squares, model selection, and estimated taxa-removal analysis) suggest that the hunter specialization appeared during the Early Cretaceous, revealing that Cretaceous abelisaurids can be considered specialist hunters. High levels of morphological disparity in the maxilla occurred shortly after the Cenomanian-Turonian faunistic turnover, which involved drastic changes in the South American terrestrial faunal assemblages. Moreover, the high evolutionary rates of the maxillary shape change in Abelisauridae support a shift in ecological pressures or socio-sexual mechanisms, which were the main drivers of the evolution of the clade rostrum. Our study invites to analyze more osteological elements of the abelisaurid skull under a quantitative macroevolutionary framework to test our results more comprehensively.
... The principles of beam theory, which assume the mandible as a solid beam that undergoes loads during biting of food ingestion, are able to derive mandibular force profiles that can provide information related to the hunting and feeding behaviour of a predator (e.g., Therrien et al., 2005Therrien et al., , 2021Jasinski, 2011;Monfroy, 2017;Yun, 2024). The biomechanical modelling of the mandible through the principles of beam theory is advantageous in being relatively simple and efficient, as it requires only several external dimensions of the lower jaw and therefore, does not require complex, expensive and timeconsuming computer programs that are used in other biomechanical methods such as finite element analyses (e.g., Therrien et al., 2021). ...
... Furthermore, the results of beam theory modelling are largely consistent with those of other more complex methods (e.g., FEA or finite element analysis) and potentially provide more accurate bite force estimates than those yielded from jaw muscle architecture measurements in some cases (Therrien et al., 2016(Therrien et al., , 2021. Based on such advantages, the beam theory method has been applied to a variety of theropod dinosaurs, including dromaeosaurids (e.g., Therrien et al., 2005Therrien et al., , 2021Jasinski, 2011;Monfroy, 2017;Yun, 2024). Therrien et al. (2005) derived mandibular force profiles of four dromaeosaurid taxa (Deinonychus antirrhopus-YPM 41147, Dromaeosaurus albertensis-AMNH 5356, Saurornitholestes langstoni-TMP 88.121.39, ...
... Based on such advantages, the beam theory method has been applied to a variety of theropod dinosaurs, including dromaeosaurids (e.g., Therrien et al., 2005Therrien et al., , 2021Jasinski, 2011;Monfroy, 2017;Yun, 2024). Therrien et al. (2005) derived mandibular force profiles of four dromaeosaurid taxa (Deinonychus antirrhopus-YPM 41147, Dromaeosaurus albertensis-AMNH 5356, Saurornitholestes langstoni-TMP 88.121.39, Velociraptor mongoliensis-Utah Geological Survey cast of privately owned specimen) and found, while they were only capable of delivering weak and fast slashing bites, the bite force of Dromaeosaurus albertensis was relatively, and absolutely, higher compared to others. ...
Acheroraptor temertyorum is a dromaeosaurid theropod, probably a saurornitholestine, found in the upper Maastrichtian Hell Creek Formation of Montana. This enigmatic dromaeosaurid is known from only a partial maxilla and dentary, as well as referred isolated teeth, making even the general aspects of its palaeobiology largely elusive. In this work, beam theory is applied to the lower jaw of Acheroraptor temertyorum to document the biomechanical properties of the mandible of this taxon and to infer the feeding mechanism of this dinosaur. This work suggests the lower jaw of Acheroraptor temertyorum is mainly adapted to produce rapid, slashing bites, as previously inferred for other dromaeosaurids. Intriguingly, despite having a closer phylogenetic affinity with Saurornitholestes langstoni, overall biomechanical properties of the lower jaw of Acheroraptor temertyorum are found to be weaker than the former taxon, but rather comparable to Asian velociraptorines. Such results may indicate Acheroraptor temertyorum preyed on smaller animals compared to other saurornitholestines, and suggest diets or predation methods of saurornitholestine dromaeosaurids might have been more diverse than previously assumed.
... So far, relatively complete bones that comprise the snout or anterior half of the mandible, which would have been used in hunting and feeding, are only known in Australovenator wintonensis and Megaraptor namunhuaiquii among derived megaraptorans (Hocknull et al., 2009;Porfiri et al., 2014;White et al., 2015b). For this reason, biomechanical analyses on craniomandibular bones, which are important for assessing feeding function or hunting behavior and were frequently performed in other theropods (e.g., Rayfield, 2005;Therrien et al., 2005Therrien et al., , 2021Rowe & Snively, 2021;Johnson-Ransom et al., 2024), have not been performed in megaraptorans. Since the ungual bone generally operates as a thirdclass lever, the ratio of in-lever length to out-lever length (Mechanical Advantage) can be used as a proxy for structural strength of the claw (e.g., Ostrom, 1966;Tsogtbaatar et al., 2018;Kobayashi et al., 2022;Kubota et al., 2024). ...
... Considering that the flexor tubercle serves as an attachment point of the flexor digitorum longus, the values of Mechanical Advantage (=proxy for the size of the tubercle) can be used as indicators of the output force applied on the tip of the ungual (e.g., Tsogtbaatar et al., 2018;Kobayashi et al., 2022;Kubota et al., 2024). The principles of beam theory, which requires only external dimensions on some aspects of the mandible, can be used to derive mandibular force profiles from the complete lower jaw, or even from the isolated dentary of a theropod (Therrien et al., 2005(Therrien et al., , 2021Jasinski, 2011;Monfroy, 2017;Yun, 2024). This technique is relatively simple, less time-consuming, does not require expensive, complex computer analysis programs, and has been shown to yield results compatible with the more complex Finite Element Analysis (FEA) (e.g., Therrien et al., 2005Therrien et al., , 2016Therrien et al., , 2021. ...
... The principles of beam theory, which requires only external dimensions on some aspects of the mandible, can be used to derive mandibular force profiles from the complete lower jaw, or even from the isolated dentary of a theropod (Therrien et al., 2005(Therrien et al., , 2021Jasinski, 2011;Monfroy, 2017;Yun, 2024). This technique is relatively simple, less time-consuming, does not require expensive, complex computer analysis programs, and has been shown to yield results compatible with the more complex Finite Element Analysis (FEA) (e.g., Therrien et al., 2005Therrien et al., , 2016Therrien et al., , 2021. A medium-sized megaraptoran dinosaur from Australia, Australovenator wintonensis, provides an optimal opportunity to study mandibular biomechanic profiles in order to infer feeding and hunting behavior, as well as bite force of this lineage. ...
Megaraptoran theropods represent an enigmatic and unusual lineage of theropod dinosaurs that are characterized by their unique bauplan including a low, elongated skull and robust forelimbs with enlarged claws. Such an unusual morphology has led to speculations that these theropods primarily used forelimbs instead of jaws in prey capture or feeding, but biomechanical studies regarding in-depth evaluations of the functions of their claws or jaws have been scarce. In this work, mandibular force profiles of Australian megaraptoran Australovenator wintonensis are constructed through the principle of beam theory, and mechanical advantages of first manual unguals of various megaraptoran taxa are evaluated using third-class lever model. Mandibular force profiles reveal that the lower jaw of Australovenator wintonensisbehaved as a simple lever, suitable for delivering slashing bites, and likely unable to produce a high bite force. Biomechanical modeling of the first manual unguals of megaraptorans suggests a decrease in Mechanical Advantage in derived taxa, which indicates the claws became more adapted to hook-and-pull function during the course of evolution in this clade. Such results imply megaraptorans like Australovenator wintonensis mainly preyed on relatively small-sized animals, or relied more on their forelimbs to hunt large prey items through hooking the claws onto the victim and pulling them, tearing or slicing the flesh.
... The bite force applied at any point on the mandible reflects its external dimensions in each location. Then, the variation of these dimensions indicates the ability of the mandible to resist different loads, which reflects the feeding behaviour (Therrien 2005a, b;Therrien et al. 2005Therrien et al. , 2016. ...
... Each section has its shape and can present hollows on the surface, such as the Meckelian window or the abduc-tor fossa, and, above all, inside. Therefore, besides beam theory (Biknevicius and Ruff 1992;Therrien 2005a, b;Therrien et al. 2005Therrien et al. , 2016Organ et al. 2006), other biomechanical approaches have been developed, such as jaw musculature reconstruction (Christiansen and Adolfssen 2005;Christiansen and Wroe 2007;Wroe et al. 2007) and finite element analysis (FEA) Rayfield 2007;Fry et al. 2009;Slater et al. 2009Slater et al. , 2010Tseng and Binder 2010;Tseng and Wang 2010;Tseng et al. 2011;Fortuny et al. 2012;Tseng 2013;Figueirido et al. 2014;Konietzko-Meier et al. 2018;Rowe and Snively 2022). However, the mandibular force profile method, based on beam theory, remains the simplest, because it does not require computer tomography (CT) or scanners; its results are quite similar to the ones of FEA and it can be used to substitute or integrate other techniques as well (Metzger et al. 2005;Walmsley et al. 2013;Therrien et al. 2016;Rowe and Snively 2022). ...
... The mandibular force profile method is mainly used with crocodilians (Busbey 1995;Metzger et al. 2005;McHenry et al. 2006;Walmsley et al. 2013) and theropods (Therrien et al. 2005;Snively et al. 2006;Cuff and Rayfield 2013) to examine the adaptation of the skull and mandible to stress in biting, shaking and twisting. In this work we do not investigate the possibility of Metoposaurus performing lateral or rotational movements; we just apply the method to biting to verify if it can be useful to understand the differences among specimens or add information about the general functioning of the mandible. ...
Amphibians, due to their ecological plasticity, are some of the best environmental indicators among vertebrates nowadays and in the fossil record. One such example is the extinct family Metoposauridae Watson, 1919. Metoposaurids were abundant amphibians in Late Triassic Pangea. The remains of the genus Metoposaurus Lydekker, 1890 have been found in Germany, Poland and Portugal with three species, respectively Metoposaurus diagnosticus (Meyer, 1842), Metoposaurus krasiejowensis Sulej, 2002 and Metoposaurus algarvensis Brusatte, Butler, Mateus and Steyer, 2015. Since the majority of studies concern the skull and the pectoral girdle, in this work M. krasiejowensis has been analysed through a morphometric study of the mandible. This was made possible by the high abundance of fossils found in Krasiejów (SW Poland) in the last 20 years. The characteristics considered are the morphology of the mandible corpus and its most relevant bones, the adaptation to stress during biting and the dermal ornamentation. The results reveal that not only do these characters have great intraspecific variability, but that at least two groups of a single population of M. krasiejowensis probably had different lifestyles, one more aquatic and the other more terrestrial.
... At present, however, no quantitative evidence has been provided for this hypothesis, such as the biomechanical modelling of the jaws like that performed for other tyrannosaurids (e.g. Therrien et al. 2005Therrien et al. , 2021Rowe & Snively 2021;Johnson-Ransom et al. 2023). ...
... The principles of beam theory can be applied to mandibles in order to derive lower jaw force profiles, which can evaluate mandibles regarding their ability to resist bending loads imposed during biting, and provide information related to the feeding behaviour and bite force of an animal (e.g. Therrien et al. 2005Therrien et al. , 2021. This method uses the external dimensions of the mandible to model it as a solid, elliptical beam that went through bending loads during ingestion (Therrien et al. 2005(Therrien et al. , 2016(Therrien et al. , 2021, and while it was argued that this approach may underestimate the bite force in order to produce tooth marks left in bone (Gignac et al. 2010), a work of Therrien et al. (2016) demonstrated that biomechanical modeling using the beam theory yields very similar results or estimations regarding the pattern of change in biomechanical properties along the lower jaw and bite forces to those of other methods, using carnivoran mammals. ...
... Therrien et al. 2005Therrien et al. , 2021. This method uses the external dimensions of the mandible to model it as a solid, elliptical beam that went through bending loads during ingestion (Therrien et al. 2005(Therrien et al. , 2016(Therrien et al. , 2021, and while it was argued that this approach may underestimate the bite force in order to produce tooth marks left in bone (Gignac et al. 2010), a work of Therrien et al. (2016) demonstrated that biomechanical modeling using the beam theory yields very similar results or estimations regarding the pattern of change in biomechanical properties along the lower jaw and bite forces to those of other methods, using carnivoran mammals. Furthermore, the beam theory model produces more accurate bite force measurements to those derived from jaw muscle architecture measurements (Therrien et al. 2016), and feeding behaviours reconstructed via this method are congruent with those obtained from using finite element analysis (e.g. ...
Alioramin theropods, a unique lineage within the clade Tyrannosauridae, are characterized by relatively diminutive size and longirostrine skull with increased tooth counts. Based on this unusual morphology, it has been suggested that alioramins had a unique ecological niche for tyrannosaurids, primarily hunting small prey items. However, there has been no quantitative evidence suggested for this claim. In this work, mandibular force profiles of the alioramins Alioramus altai and Qianzhousaurus sinensis are examined. The bending strength of the symphyseal region is found to be stronger than the middentary in both taxa, as in other tyrannosaurids. However, the relative mandibular force at the symphyseal region in alioramins is significantly higher, suggesting this region went through significantly less torsional stresses compared to non-alioramin tyrannosaurids. This may also suggest they used shearing, slashing bites more frequently in hunting and feeding than other tyrannosaurids. Additionally, the bending force at the middentary, which is a valid proxy for a bite force in theropods, of alioramins is found to be both relatively and absolutely lower than other tyrannosaurids, or even non-tyrannosaurid theropods of similar mandibular length. Such results strongly imply alioramins were unsuited for delivering powerful bites and enduring high torsional loads, and are consistent with the previous hypothesis that alioramins mainly fed on small prey that did not require a strong bite force or mandibular symphysis capable of resisting high tor-sional stresses to capture and manipulating.
... The most likely interpretation of this mode of function of the jaw apparatus is that ornithosuchids were mainly adapted to hunt and rapidly kill large, not very mobile prey (Sennikov, 2024). The high bite force of ornithosuchids (Baczko, 2018), resembling modern mammalian carnivores (Wroe et al., 2005;Christiansen and Wroe, 2007), short-snouted crocodiles (Endo et al., 2002) or tyrannosaurids (Meers, 2002;Therrien et al., 2005) should suggest large prey size. At the same time, the slow, powerful bite of ornithosuchids is completely unsuitable for seizing small, agile terrestrial tetrapods and fast-swimming amphibians or fish. ...
Ornithosuchidae differ from other carnivorous archosaurs in the unique morphology of the jaw apparatus and postcranial skeleton. Various, often opposite, points of view have been expressed regarding their trophic adaptations-from carnivory and scavenging to piscivory. The most reasonable hypothesis seems to be that ornithosuchids were medium sized hyperanisodont carnivorous macrophages. Moreover, there are some analogies between ornithosuchids and saber-toothed therapsids and mammals.
Among the early archosaurs, various ecological types are represented – from predators to herbivores, from terrestrial to semi-aquatic forms. A special place among them is occupied by the family Ornithosuchidae, which are traditionally considered as active predators. The unique structure of the jaw apparatus and the morphology of the postcranial skeleton of Ornithosuchidae indicate the formation in them the only special ecological type among archosaurs – a hyperanisodont macrophagous predator. At the same time, some analogies can be noted between ornithosuchids and saber-toothed therapsids and mammals.
This literature review aims to gain a deeper understanding of the anatomy behind the jaw strength of Tyrannosaurus rex and analyze how these features contribute to its predatory behavior. This review will examine various studies and fossil excavations, exploring ideas such as the bite force of T. rex and its variations across different life stages. This will be obtained from numerous biomechanical models of both juvenile and adult Tyrannosaurus rex, as well as reference animals and dinosaurs for comparison. To provide additional information behind T. rex’s hunting techniques, we will also discuss the fauna of herbivorous dinosaurs that were part of T. rex’s diet. Furthermore, we will explore how mandibular stress concentration can vary between ages, a crucial topic in determining what T. rex could consume at certain stages of its life. Finally, we obtain a well-evidenced analysis of the various aspects of Tyrannosaurus rex’s hunting strategies throughout its lifetime.
We describe the osteology of the new small theropod dinosaur Masiakasaurus knopfleri, from the Late Cretaceous Maevarano Formation of northwestern Madagascar. Approximately 40% of the skeleton is known, including parts of the jaws, axial column, forelimb, pelvic girdle, and hind limb. The jaws of Masiakasaurus are remarkably derived, bearing a heterodont, procumbent dentition that is unknown elsewhere among dinosaurs. The vertebrae are similar to those of abelisauroids in the reduction of the neural spine, lack of pleurocoelous fossae on the centrum, and extensively pneumatized neural arch. The limb skeleton is relatively gracile and bears numerous abelisauroid synapomorphies, including a rounded humeral head, peg-and-socket iliac-pubic articulation, prominent femoral medial epicondyle, expanded tibial cnemial crest, and double-grooved pedal unguals. The femora and tibiae show evidence of dimorphism. More specific features shared between Masiakasaurus, the Argentine Noasaurus, and the Indian Laevisuchus suggest that these taxa form a clade (Noasauridae) within Abelisauroidea. This is supported by a cladistic phylogenetic analysis of 158 characters and 23 theropod taxa. Additionally, Ceratosauria is rendered paraphyletic in favor of a sister-taxon relationship between Neoceratosauria and Tetanurae that is exclusive of Coelophysoidea. The unique dental and jaw specializations of Masiakasaurus suggest deviation from the typical theropod diet. Finally, the distribution of noasaurids further supports a shared biogeographic history between South America, Madagascar, and India into the Late Cretaceous.
Individual variation for the large theropod Tyrannosaurus rex may be seen in the maxilla, dentary and ischium. The maxilla is variable in its depth, the size and shape of the maxillary and antorbital fenestrae, and the size and shape of the lacrimal and jugal processes. Even the left and right maxillae of the same skull show variation. Sexual dimorphism is suggested by the presence of two morphs, one more robust than the other. The angle between the ischia and caudals of the robust morph is greater than in the slender morph, and would provide ample space for the passage of eggs. On this basis, the robust morph is considered the female. -Author
In recent years dinosaurs have captured the attention of the public at an unprecedented scale. At the heart of this resurgence in popular interest is an increased level of research activity, much of which is innovative in the field of palaeontology. For instance, whereas earlier palaeontological studies emphasized basic morphologic description and taxonomic classification, modern studies attempt to examine the role and nature of dinosaurs as living animals. More than ever before, we understand how these extinct species functioned, behaved, interacted with each other and the environment, and evolved. Nevertheless, these studies rely on certain basic building blocks of knowledge, including facts about dinosaur anatomy and taxonomic relationships. One of the purposes of this volume is to unravel some of the problems surrounding dinosaur systematics and to increase our understanding of dinosaurs as a biological species. Dinosaur Systematics presents a current overview of dinosaur systematics using various examples to explore what is a species in a dinosaur, what separates genders in dinosaurs, what morphological changes occur with maturation of a species, and what morphological variations occur within a species.
Organisms must contend with the physical characteristics of their environment as they carry out a wide range of physiological and mechanical functions. Particular structural solutions must be evolved to meet particular biological demands, both within and external to theorganism. The application of engineering principles to living (and fossil) organisms, and to the materials of which they are built, represents an important interdisciplinary approach that can facilitate and help to open new insights into our understanding of organismal design and function. An understanding of this relationship is also important in terms of how organisms respond and adapt to changes in their physical environment. Although biomechanics has seen a recent growth in a number of fields within the biological sciences, the approach has had a long history (1, 2).