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A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae)
Abstract
The brain morphology and the topography of the cranial nerves on an endocranial mold of the theropod dinosaur Tarbosaurus bataar (Tyrannosauridae) are examined. The brain of this dinosaur was constructed based on the reptile archetype, with a well-developed
specialized olfactory analyzer. In terms of development, the visual centers were superseded not only by the olfactory centers,
but also by the auditory centers. Comparative analysis of the brain structure of Tarbosaurus and Tyrannosaurus shows clear distinctions in the topography of roots of the accessory and trigeminal nerves.
... In CMN 8506 and TMP 2001.36.1, the dural peak is not markedly higher than the cerebral hemisphere or the olfactory bulb. This is similar to the endocast for Tarbosaurus (Saveliev and Alifanov 2007) and one specimen of Tyrannosaurus (AMNH 5117) (Witmer and Ridgely 2009). However, the endocasts each have a markedly distinct, dorsally projecting dural peak in other specimens of Tyrannosaurus (AMNH 5029; CMNH 7541; FMNH PR2081) and at least one specimen each of Alioramus (MPC-D 100/1844) and Gorgosaurus (ROM 1247) (Osborn 1912;Brochu 2000;Ridgely 2009, 2010;Bever et al. 2013). ...
... The trochlear nerve exits the endocranial cavity preoptically (directly above or anterior to the optic fenestra). In all other tyrannosaurid endocasts including that of TMP 2001.36.1, the trochlear nerve has its root in a postoptic position, dorsal to that of the oculomotor nerve (Osborn 1912;Brochu 2000;Saveliev and Alifanov 2007;Ridgely 2009, 2010;Bever et al. 2013). Despite this substantial anterior shift, the external trochlear foramina of CMN 8506 correspond in overall configuration to those of other tyrannosaurids. ...
... In both CMN 8506 and TMP 2001.36.1, the flocculus is tongue-like and compressed transversely in cross section. This condition is also observed in mature individuals of Tarbosaurus and Tyrannosaurus (Saveliev and Alifanov 2007;Witmer and Ridgely 2009). In smaller tyrannosaurids such as CMNH 7541 and Gorgosaurus, the flocculus is similarly tongue-like, but extends further posteriorly to the level of crus communis Ridgely 2009, 2010). ...
For sheer complexity, braincases are generally considered anatomically conservative. However, recent research on the braincases of tyrannosaurids have revealed extensive morphological variations. This line of inquiry has its root in Dale Russell’s review of tyrannosaurids in which he established Daspletosaurus torosus — a large tyrannosaurine from the Campanian of southern Alberta. In the wake of systematic revisions to tyrannosaurines previously assigned to Daspletosaurus, one potentially distinct species remains undescribed. This paper describes and compares a braincase referable to this species with that of the holotype for Daspletosaurus torosus using computerized-tomography-based reconstructions. The two braincases have numerous differences externally and internally. The specimen of Daspletosaurus sp. has a bottlenecked olfactory tract, short and vertical lagena, and a developed ascending column of the anterior tympanic recess. The holotype of Daspletosaurus torosus has many unusual traits, including an anteriorly positioned trochlear root, elongate common carotid canal, distinct chamber of the basisphenoid recess, asymmetry in the internal basipterygoid aperture, and laterally reduced but medially expanded subcondylar recess. This comparison also identified characters that potentially unite the two species of Daspletosaurus, including deep midbrain flexures in the endocasts. However, many character variations in the braincases are known in other tyrannosaurids to correlate with body size and maturity, or represent individual variations. Therefore, taxonomic and phylogenetic signals can be isolated from background variations in a more comprehensive approach by using additional specimens. New information on the two braincases of Daspletosaurus is consistent with the emerging view of tyrannosaurid braincases as highly variable, ontogenetically dynamic character complexes.
... The present article forms part of a series dealing with the study of brain structure and the reconstruction of dinosaur biology from artificial and natural neurocranial endocasts. The authors have previously published data on tyrannosaurids (Saveliev and Alifanov, 2007), alvarezsaurs (Alifanov and Saveliev, 2007), and duck-billed dinosaurs (Saveliev et al., 2012). The present study deals with ankylosaurs. ...
... The present article forms part of a series dealing with the study of brain structure and the reconstruction of dinosaur biology from artificial and natural neurocranial endocasts. The authors have previously published data on tyrannosaurids (Saveliev and Alifanov, 2007), alvarezsaurs (Alifanov and Saveliev, 2007), and duck-billed dinosaurs (Saveliev et al., 2012). The present study deals with ankylosaurs. ...
Brain morphology and topography of cranial nerves of the armored dinosaur Bissektipelta archibaldi from the late Cretaceous of Uzbekistan are studied using an artificial endocranial cast. We reconstruct for the Bissektian ankylosaur well-developed olfaction, poor hearing and eyesight, good taste sensitivity, omnivorous diet as well as the ability to filter-feed. The brain structure of Bissektipelta archibaldi is archaic compared with other ankylosaurian species.
... As generic distinction of Tarbosaurus and Tyrannosaurus gives more room for the assessment of relationships of such specimens, it may be more appropriate to treat these genera as separate. After the description and naming of the taxon by Maleev (1955a), many additional specimens of Tarbosaurus bataar have been discovered Currie 2009Currie , 2013Currie , 2016Jerzykiewicz et al. 2021) and these have been the subjects of many anatomical studies Saveliev and Alifanov 2007;Tsuihiji et al. 2011). However, despite this wealth of material, little is known about the ontogeny of this Mongolian tyrannosaurid. ...
Tarbosaurus bataar is a sister taxon of the well-studied theropod dinosaur Tyrannosaurus rex, and numerous fossils of
this tyrannosaurid have been discovered in the Upper Cretaceous Nemegt Formation of Mongolia. Although specimens
of different sizes of Tarbosaurus bataar have been discovered since its initial description, few rigorous studies on its
growth changes have been done. Here we examine growth changes in the frontal bones of seven Tarbosaurus bataar
specimens using bivariate analyses and the Björk superimposition method to demonstrate trends in their ontogenetic
allometry. The width and depth of the frontal undergoes positive allometry during growth, whereas the length shows a
trend of negative allometry. The details of growth changes in Tarbosaurus bataar frontals are largely similar to those
of Tyrannosaurus rex. Furthermore, generic allometric trends of tyrannosaurid frontals, including those of Tarbosaurus
bataar, are shared with other large-bodied theropod clades and may represent a consequence of strengthening parts of
the braincase as an anchor for the jaw musculature.
... Although a fossilised, mummified lip fragment has been reported in one sauropod specimen, the almost ubiquitous presence of a cornified beak in ornithischians and intermeshing teeth in many basal pterosaurs casts some doubt on whether the presence of squamate-like lips was the primitive condition for Dinosauria (Morris, 1970;Hieronymus et al., 2009;Paul, 2018). In non-avian theropods, high dental replacement rates (D'Emic et al., 2019) and the size of the foramen for the glossopharyngeal nerve (IX) in Tarbosaurus and Tyrannosaurus, which is linked to salivary secretion (Saveliev and Alifanov, 2007), both suggest that teeth were quickly replaced and saliva was produced abundantly enough so that the enamel of the teeth could have withstood a dry environment. ...
The study of the rostral neurovascular system using CT scanning has shed new light on phylogenetic and palaeobiological reconstructions of many extinct tetrapods. This research shows a detailed description of the rostral neurovascular canals of Tyrannosaurus rex including the nasal, maxillary (dorsal alveolar), and mandibular (ventral alveolar) canals. Extensive comparisons with published descriptions show that the pattern of these canals in Tyrannosaurus is not unusual for a non-avian theropod. As in the non-avian theropod Neovenator, the maxillary canal shows several anasto-moses of its branches. Differences from the plesiomorphic sauropsid condition are concentrated within the canal for the maxillary neurovasculature, which is primitively horizontal, tubular, and connected to a single row of supralabial foramina, whereas in Tyrannosaurus the main trunk of the canal is oriented more obliquely and dorsally dis-placed to give room to the deep tooth alveolae. As a result, the lateral branches that provide innervation and blood supply to the skin are dorsoventrally elongated com-pared to non-theropod taxa, and multiple rows of supralabial foramina are present. An overview of the literature suggests that the evolution of the trigeminal canals among sauropsids only weakly supports previous hypotheses of crocodile-like facial sensitivity in non-avian theropods (except, maybe, in semiaquatic taxa). More systematic studies of the rostral neurovascular canals in non-avian theropods may help answer the question of whether lips were present or not.
... Raptorex was initially described as a small adult approximately 5-6-year-old from lower Cretaceous Yixian Formation of China (Peixian et al. 1994;Sereno et al. 2009). However, the specimen is now considered a 3-6-year-old juvenile of much later, extensively studied tyrannosaurs (Fowler et al. 2011), such as Tarbosaurus bataar from the upper Cretaceous Nemegt Formation of Mongolia (Maleev 1965(Maleev , 1974Hurum and Currie 2000;Hurum and Sabath 2003;Saveliev and Alifanov 2007;Tsuihiji et al. 2011). ...
The tyrannosaurids are among the most well‐studied dinosaurs described by science, and analysis of their feeding biomechanics allows for comparison between established tyrannosaurid genera and across ontogeny. We used 3D finite element analysis (FEA) to model and quantify the mechanical properties of the mandibles (lower jaws) of three tyrannosaurine tyrannosaurids of different sizes. To increase evolutionary scope and context for 3D tyrannosaurine results, a broader sample of validated 2D mandible FEA enabled comparisons between ontogenetic stages of Tyrannosaurus rex and other large theropods. We found that mandibles of small juvenile and large subadult tyrannosaurs experienced lower stress overall because muscle forces were relatively lower, but experienced greater simulated stresses at decreasing sizes when specimen muscle force or surface area is normalized. Strain on post‐dentary ligaments decreases stress and strain in the posterior region of the dentary and where teeth impacted food. Tension from the lateral insertion of the looping m. ventral pterygoid muscle increases compressive stress on the angular but may decrease anterior bending stress on the mandible. Low mid‐mandible bending stresses are congruent with ultra‐robust teeth and high anterior bite force in adult Tyrannosaurus rex. Mandible strength increases with size through ontogeny in T. rex and phylogenetically among other tyrannosaurids, in addition to that tyrannosaurid mandibles exceed mandible strength of other theropods at equivalent ramus length. These results may indicate separate predatory strategies used by juvenile and mature tyrannosaurids; juvenile tyrannosaurids lacked the bone‐crunching bite of adult specimens and hunted smaller prey, while adult tyrannosaurids fed on larger prey.
... This is consistent with observations for basal tetanurans and ceratosaurs [e.g. 20,23,25,38,39 ]. Near the cephalic flexure, the endocast of SMNS 58022 shows a weakly developed dural peak (Fig. 2a). ...
Spinosauridae, a theropod group characterized by elongated snouts, conical teeth, enlarged forelimbs, and often elongated neural spines, show evidence for semiaquatic adaptations and piscivory. It is currently debated if these animals represent terrestrial carnivores with adaptations for a piscivorous diet, or if they largely lived and foraged in aquatic habitats. The holotype of Irritator challengeri, a nearly complete skull from the late Early Cretaceous Santana Formation of northeastern Brazil, includes one of the few preserved spinosaurid braincases and can provide insights into neuroanatomical structures that might be expected to reflect ecological affinities. We generated digital models of the neuroanatomical cavities within the braincase, using computer tomography (CT) data. The cranial endocast of Irritator is generally similar to that of other non-maniraptoriform theropods, with weakly developed distinctions of hindbrain and midbrain features, relatively pronounced cranial flexures and relatively long olfactory tracts. The endosseous labyrinth has a long anterior semicircular canal, a posteriorly inclined common crus and a very large floccular recess fills the area between the semicircular canals. These features indicate that Irritator had the ability for fast and well-controlled pitch-down head movements. The skull table and lateral semicircular canal plane are strongly angled to one another, suggesting a downward angling of approximately 45° of the snout, which reduces interference of the snout with the field of vision of Irritator. These neuroanatomical features are consistent with fast, downward snatching movements in the act of predation, such as are needed for piscivory.
... So far, several analyses led to complete reconstructions of the cranial endocast and inner ear in different groups of non-avian theropods, including basal neotheropods Xing et al., 2014), coelophysoids (Raath, 1977, fig. 21), ceratosaurs (e.g., Paulina-Carabajal and Filippi, 2018;Succar, 2015, Sanders andSmith, 2005;Sampson and Witmer, 2007), allosauroids (e.g., Franzosa and Rowe, 2005;Larsson, 2001;Paulina-Carabajal and Canale, 2010;Paulina-Carabajal and Currie, 2012;Rogers, 1998), megaraptorids (Paulina-Carabajal and Currie, 2017;Paulina-Carabajal and Porfiri, 2018), tyrannosaurids (e.g., Bever et al., 2011, and references therein;Saveliev and Alifanov, 2005;Witmer and Ridgely, 2009) and more derived coelurosaurs (e.g., Balanoff et al., 2018;Lautenschlager et al., 2012). ...
The endocranial morphology of the abelisaurid Carnotaurus sastrei, from the Upper Cretaceous of Patagonia, is studied using X-ray Computed Tomography (CT). The CT scans provided information that allowed the first reconstruction of the brain, inner ear and braincase pneumaticity for this South American taxon. The endocranial morphology confirms that abelisaurids share an overall conformation of the brain and inner ear. However, some traits, such as the height of the dorsal sinuses and the length of the flocculus in the cranial endocast, and a large subsellar recess in the basicranium, appear to characterize the South-American abelisaurids only. Moreover, the olfactory acuity of Carnotaurus resembles that reported for other abelisaurids (e.g., Majungasaurus, Viavenator), suggesting that the sense of smell had an important role. However, some attributes of the endocranial features of Carnotaurus (i.e. development and orientation of the olfactory bulbs and tracts) may imply particular olfactory capacities when compared with other abelisaurids.
... So far, several analyses led to complete reconstructions of the cranial endocast and inner ear in different groups of non-avian theropods, including basal neotheropods Xing et al., 2014), coelophysoids (Raath, 1977, fig. 21), ceratosaurs (e.g., Paulina-Carabajal and Filippi, 2018;Succar, 2015, Sanders andSmith, 2005;Sampson and Witmer, 2007), allosauroids (e.g., Franzosa and Rowe, 2005;Larsson, 2001;Paulina-Carabajal and Canale, 2010;Paulina-Carabajal and Currie, 2012;Rogers, 1998), megaraptorids (Paulina-Carabajal and Currie, 2017;Paulina-Carabajal and Porfiri, 2018), tyrannosaurids (e.g., Bever et al., 2011, and references therein;Saveliev and Alifanov, 2005;Witmer and Ridgely, 2009) and more derived coelurosaurs (e.g., Balanoff et al., 2018;Lautenschlager et al., 2012). ...
The endocranial morphology of the abelisaurid Carnotaurus sastrei, from the Upper Cretaceous of Patagonia, is studied using X-ray Computed Tomography (CT). The CT scans provided information that allowed the first reconstruction of the brain, inner ear and braincase pneumaticity for this South American taxon. The endocranial morphology confirms that abelisaurids share an overall conformation of the brain and inner ear. However, some traits, such as the height of the dorsal sinuses and the length of the flocculus in the cranial endocast, and a large subsellar recess in the basicranium, appear to characterize the South-American abelisaurids only. Moreover, the olfactory acuity of Carnotaurus resembles that reported for other abelisaurids (e.g., Majungasaurus, Viavenator), suggesting that the sense of smell had an important role. However, some attributes of the endocranial features of Carnotaurus (i.e. development and orientation of the olfactory bulbs and tracts) may imply particular olfactory capacities when compared with other abelisaurids.
This chapter aims to provide an overview of the state of knowledge on non-avian dinosaur paleoneurology, throughout the history and synthesis of recent advances in the field. Today, the endocranial morphology of approximately 150 dinosaur taxa has been described using natural or artificial cranial endocasts. They represent all major clades, although there is a bias towards Cretaceous -and more derived- forms. From this sample more than a half of the publications were made in the last 20 years, hand in hand with the use of non-invasive technologies. This larger amount of anatomical data opened the door to more comprehensive analyses (quantitative methods), allowing us to better understand the evolution of the dinosaur brain pattern and sense biology through deep time.
Tyrannosaurus rex and other tyrannosaurid dinosaurs were apex predators during the latest Cretaceous, which combined giant size and advanced neurosensory systems. Computed tomography (CT) data have shown that tyrannosaurids had a trademark system of a large brain, large olfactory bulbs, elongate cochlear ducts, and expansive endocranial sinuses surrounding the brain and sense organs. Older, smaller tyrannosauroid relatives of tyrannosaurids developed some, but not all, of these features, raising the hypothesis that tyrannosaurid‐style brains evolved before the enlarged tyrannosaurid‐style sinuses, which might have developed only with large body size. This has been difficult to test, however, because little is known about the brains and sinuses of the first large‐bodied tyrannosauroids, which evolved prior to Tyrannosauridae. We here present the first CT data for one of these species, Bistahieversor sealeyi from New Mexico. Bistahieversor had a nearly identical brain and sinus system as tyrannosaurids like Tyrannosaurus, including a large brain, large olfactory bulbs, reduced cerebral hemispheres, and optic lobes, a small tab‐like flocculus, long and straight cochlear ducts, and voluminous sinuses that include a supraocciptal recess, subcondyar sinus, and an anterior tympanic recess that exits the braincase via a prootic fossa. When characters are plotted onto tyrannosauroid phylogeny, there is a two‐stage sequence in which features of the tyrannosaurid‐style brain evolved first (in smaller, nontyrannosaurid species like Timurlengia), followed by features of the tyrannosaurid‐style sinuses (in the first large‐bodied nontyrannosaurid tyrannosauroids like Bistahieversor). This suggests that the signature tyrannosaurid sinus system evolved in concert with large size, whereas the brain did not. Anat Rec, 2020. © 2020 American Association for Anatomy
The theropod family Tyrannosauridae (Dinosauria) is composed of four genera and seven species. All taxa are known from nearly complete skeletons and/ or skulls, thus making it one of the best documented large theropod families. The stratigraphic and palaeobiogeographic distribution of the Tyrannosauridae extends from the lower Campanian to upper Maastrichtian of North America, and to the Campanian-Maastrichtian
of Asia.
The holotype of Microvenator celer Ostrom, 1970 (AMNH 3041) is a partial skeleton of a small maniraptoran theropod from the Lower Cre-taceous Cloverly Formation of Montana. We present a detailed redescription of this specimen, emphasizing those features that are of interest for discovering the phylogenetic relationships of Mi-crovenator. Based on several postcranial features, especially the lack of fusion of the neurocentral sutures, we consider AMNH 3041 a juvenile individual. Reexamination of the holotype revealed the presence of several autapomorphies that provide the basis for a revised diagnosis of Micro-venator celer. Diagnostic characters include posterior dorsal and caudal vertebrae 'that are wider than high, the presence of a deep depression on the proximomedial part of the pubis, and an accessory trochanteric ridge below the lesser fem-oral trochanter. Phylogenetic analysis places Mi-crovenator either among Oviraptorosauria, or as the sister group to the Oviraptorosauria. Among the characters diagnostic for the Oviraptorosauria, anteriorly concave pubes, a proximodorsal tuber-cle on the manual unguals, and possibly an eden-tulous dentary with a pronounced symphysis are present in Microvenator. M. celer is the earliest known oviraptorosaurian or oviraptorosaur-like theropod represented by diagnostic skeletal remains .
Tyrannosaurids are a well-supported clade of very large predatory dinosaurs of Late Cretaceous Asiamerica. Traditional dinosaurian systematics place these animals within the infraorder Carnosauria with the other large theropods (allosaurids, megalosaurids). A new cladistic analysis indicates that the tyrannosaurs were in fact derived members of the Coelurosauria, a group of otherwise small theropods. Despite certain gross cranial similarities with the large predators of the Jurassic and Early Cretaceous, the Late Cretaceous tyrannosaurids are shown to be the sister group to ornithomimids and troodontids, which share a derived condition of the metatarsus. This clade is found to be nested within Maniraptora, which is a more inclusive taxon than previously recognized. The atrophied carpal structure found in tyrannosaurids and ornithomimids is derived from a maniraptoran condition with a large semilunate carpal, rather than from the plesiomorphic theropod morphology.
The taxa “Carnosauria” and “Deinonychosauria” (Dromaeosauridae plus Troodontidae) are shown to be polyphyletic, and the Late Jurassic African form Elaphrosaurus is found to be the sister taxon to Abelisauridae rather than a primitive ornithomimosaur. Purported allosaurid-tyrannosaurid synapomorphies are seen to be largely size-related, present in the larger members of both clades, but absent in smaller members of the Tyrannosauridae. The remaining giant tetanurine theropods (Megalosaurus and Torvosaurus) were found to be progressively distant outgroups to an allosaurid-coelurosaur clade. The inclusion of the Tyrannosauridae within Maniraptora suggests a major adaptive radiation of coelurosaurs within Cretaceous Asiamerica comparable to contemporaneous radiations in various herbivorous dinosaurian clades.
An isolated premaxillary tooth of tyrannosaurid from the Lower Cretaceous section of the Tetori Group, Central Honshu, Japan, complements Siamotyrannus, which is based upon an incomplete postcranium for existence of tyrannosaurids in the Early Cretaceous of Asia. The occurrence of a tyrannosaurid tooth in the Japanese early Early Cretaceous further supports the possibility that tyrannosaurids originated during the Early Cretaceous in Asia and migrated to North America when the two continents were connected via a land bridge during the early Late Cretaceous. Thickening of the premaxillary teeth might have predated the increase in body size in tyrannosaurid evolution.
Tyrannosauroids are among the most distinctive and best known of Mesozoic theropods. Diagnostic skeletal material for Tyrannosauridae is at present limited to the last part of the Late Cretaceous of eastern and central Asia (China and Mongolia) and North America; the more inclusive Tyrannosauroidea includes taxa from the Late Jurassic of Europe and North America and the Early Cretaceous of Europe and Asia. Tyrannosaurids include some of the largest known theropod taxa (up to 13 m long and weighing six or more tonnes). The five most completely known species (Tyrannosaurus rex, Tarbosaurus bataar, Daspletosaurus torosus, Albertosaurus sarcophagus, and Gorgosaurus libratus) are all represented by individuals with femora more than 100 cm in length, reaching 138 cm in the largest Tyrannosaurus rex.
The preceding chapters of this work have presented a survey of our present knowledge of the structural organisation of the CNS of the various groups of vertebrates. This last chapter will highlight some of the major features revealed by our survey and offer some final comments.
Fragmentary theropod remains from the Upper Jurassic (Kimmeridgian) of Guimarota, Portugal, represent a new taxon of theropod dinosaurs, Aviatyrannis jurassica gen. et sp. nov. Together with Stokesosaurus from the Morrison Formation of North America, Aviatyrannis represents the oldest known tyrannosauroid, indicating that tyrannosauroid origins may be found in the Middle-Late Jurassic of Europe/North America. Furthermore, current evidence suggests that early tyrannosaurs were rather small animals, which is in general accordance with their origin amongst the generally rather small coelurosaurs.