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Crania and endocranial casts from ornithopod dinosaurs of the families Dryosauridae and Hypsilophodontidae (Reptilia: Ornithischia)
... 42-46 ). To date, no digital endocasts have been generated for any putative thescelosaurids, whereas physical endocasts are either incomplete and provide limited information 47,48 or are known 48 from a probable juvenile 27 (the holotype of T. assiniboiensis 27 ). The latter is problematic, as ornithischian endocasts are known to vary considerably through ontogeny 49 . ...
... The preservation of each element was judged on evidence of deformation (cracks, warping, asymmetry), topological constraints defined by surrounding elements of the braincase, and comparisons to the osteology of related taxa (e.g. 48 ). The left prootic and laterosphenoid are both well-preserved but have become disarticulated: these were moved back into articulation. ...
... The orbitosphenoids were not ossified in Thescelosaurus, as typical for thescelosaurids and early-diverging ornithopods 74 . However, their original ventral extent is inferred to lie at the position of a boss on the anterolateral surface of the laterosphenoids 74 , as observed in some ornithopods 48 . As orbitosphenoids are unknown from phylogenetically proximate taxa, no attempt was made to reconstruct them here. ...
Ornithischian dinosaurs exhibited a diversity of ecologies, locomotory modes, and social structures, making them an ideal clade in which to study the evolution of neuroanatomy and behaviour. Here, we present a 3D digital reconstruction of the endocranial spaces of the latest Cretaceous neornithischian Thescelosaurus neglectus, in order to interpret the neuroanatomy and paleobiology of one of the last surviving non-avian dinosaurs. Results demonstrate that the brain of Thescelosaurus was relatively small compared to most other neornithischians, instead suggesting cognitive capabilities within the range of extant reptiles. Other traits include a narrow hearing range, with limited ability to distinguish high frequencies, paired with unusually well-developed olfactory lobes and anterior semicircular canals, indicating acute olfaction and vestibular sensitivity. This character combination, in conjunction with features of the postcranial anatomy, is consistent with specializations for burrowing behaviours in the clade, as evidenced by trace and skeletal fossil evidence in earlier-diverging thescelosaurids, although whether they reflect ecological adaptations or phylogenetic inheritance in T. neglectus itself is unclear. Nonetheless, our results provide the first evidence of neurological specializations to burrowing identified within Ornithischia, and non-avian dinosaurs more generally, expanding the range of ecological adaptations recognized within this major clade.
... We could, however, observe the olfactory tract in some of the studied specimens and infer some conclusions from it. The ancestral state is represented by a thin and long peduncle as observed in Hypsilophodon foxii, Tenontosaurus tilletti (Galton, 1989) and Lurdusaurus arenatus (Lauters, 2013). In Hadrosauridae, peduncles are relatively large like in Amurosaurus riabinini and Hypacrosaurus altispinus, Corythosaurus sp., Lambeosaurus sp. ...
... Edinger (1964) proposed that the size of the pituitary gland could be correlated to the size of the adult individual. A proportional relation can indeed be observed between the relative size of the pituitary gland to brain volume; small-bodied species display a small pituitary gland, whereas the gland is larger in very large species (Galton, 1989;Giffin, 1989;Nopsca, 1917;Sander et al., 2011;Sereno et al., 2007). A reduced pituitary gland represents the ancestral state, according to the fact that more primitive species were smaller than more derived taxa. ...
... The brain of most dinosaurs is marked by two flexures: the cranial flexure and the pontine flexure (Brochu, 2003;Galton, 1989;Hopson, 1979). These flexures are also apparent in crocodilians. ...
Ornithopod dinosaurs were a successful group before they became extinct at the end of the Cretaceous. They were present on every continent, though they were rare in the Southern Hemisphere. We present the results of our work on the brain of these dinosaurs as an attempt to determine which evolutionary trends affected it. Old and new technologies allow us to peer into the skull of long extinct animals and retrieve information about their brain. First we provide a short description of the brain of ornithopod dinosaurs from Europe and Asia, then we sum up the characteristics that can be gathered from it. The presence of valleculae helps us to assess the actual size of the brain with more confidence. The olfactory peduncles are large and these animals had a good sense of smell. There is a trend toward an increase in the size of the cerebral hemispheres, and a more straight-lined brain. The latter can be the result of the ontogeny and the size achieved by the adult animal on the development of the brain. Other characteristics, like the development of the cerebral hemispheres and the encephalization quotient, allude to Hadrosauridae having had cognitive abilities more developed than previously assumed. This is in adequacy with other data from the physical characteristics (e.g., crests) and the social life (e.g., living in herds, communal nests) of these dinosaurs, which denote high and complex behaviors like care for their young, sexual courtship, and gregariousness.
... Thus, the presence of flocculus in theropods -and its apparent absence in most sauropods-was first related to bipedalism, the reason why bipedal ornithischians were expected to have an enlarged flocculus. However, this structure it is absent in most ornithischian clades and has been found only in a few taxa including the basal dryosaurid Dysalotosaurus (Galton 1989;Lautenschlager and Hübner 2013), and the quadrupedal ankylosaurs of the ankylosaurids family (Miyashita et al. 2011;Paulina-Carabajal et al. 2016b, 2018b, and stegosaurs (Galton 1988(Galton , 2001, making the paleobiological inferences of this structure, controversial at least. Recent works focused on bird brain evolution and the origins of flight assumed a positive relationship between floccular size and aerial maneuverability. ...
... This post-cerebral region (hindbrain) is similar to most other dinosaurs in the lack of detailed morphology due the presence of a large longitudinal sinus, thus suggesting that it was not closely related to the endocranial wall (Evans 2005). The floccular lobes are so small and superficial in ornithischians that they are not distinguished in most endocasts: So far, this structure has been reported in primitive iguanodontians of the dryosaurid family (Dryosaurus : Galton 1989;Lautenschlager and Hübner 2013), small ornithopods of the thescelosaurid family (Dysalotosaurus and Hypsilophodon : Galton 1989), in ankylosaurids -but not in nodosaurids- (Miyashita et al. 2011;Paulina-Carabajal et al. 2016b, 2018b, and in stegosaurs (Galton 1988(Galton , 2001. Within the latter group the flocculus is however not reconstructed in the digital rendering of Stegosaurus stenops made by Leahey et al. (2015), whereas the floccular recess is absent in the endocranial cavity of the specimen YPM 1853 (S. ungulatus at Yale Peabody Museum, APC pers. ...
... This post-cerebral region (hindbrain) is similar to most other dinosaurs in the lack of detailed morphology due the presence of a large longitudinal sinus, thus suggesting that it was not closely related to the endocranial wall (Evans 2005). The floccular lobes are so small and superficial in ornithischians that they are not distinguished in most endocasts: So far, this structure has been reported in primitive iguanodontians of the dryosaurid family (Dryosaurus : Galton 1989;Lautenschlager and Hübner 2013), small ornithopods of the thescelosaurid family (Dysalotosaurus and Hypsilophodon : Galton 1989), in ankylosaurids -but not in nodosaurids- (Miyashita et al. 2011;Paulina-Carabajal et al. 2016b, 2018b, and in stegosaurs (Galton 1988(Galton , 2001. Within the latter group the flocculus is however not reconstructed in the digital rendering of Stegosaurus stenops made by Leahey et al. (2015), whereas the floccular recess is absent in the endocranial cavity of the specimen YPM 1853 (S. ungulatus at Yale Peabody Museum, APC pers. ...
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.
... The ventral surface of the frontal possesses a prominent ventral ridge, the crisa cranii, inset medially from the orbit and running anteroposteriorly, as in Lesothosaurus (Porro et al., 2015). Anterior and medial to this ridge is the posterior end of the olfactory tract and posterior to the ridge lies a small portion of the cerebral fossa (Galton, 1989). The concave ventral surface between the orbital margin and ventral ridge is mediolaterally narrower in Haya than in Dryosaurus and Tenontosaurus (Galton, 1989; pm pm 5 mm Thomas, 2015). ...
... Anterior and medial to this ridge is the posterior end of the olfactory tract and posterior to the ridge lies a small portion of the cerebral fossa (Galton, 1989). The concave ventral surface between the orbital margin and ventral ridge is mediolaterally narrower in Haya than in Dryosaurus and Tenontosaurus (Galton, 1989; pm pm 5 mm Thomas, 2015). The frontals interlock with one another via anterodorsally directed ridges and grooves on the median sutural surface. ...
... It is roughly pyramidal. The supraoccipital forms most of the dorsal margin of the foramen magnum, as is typical of basal neornithischian taxa other than Thescelosaurus, in which its contribution is reduced (Galton, 1989;Brown et al., 2011), and iguanodontians (except for dryosaurids, Rhabdodon, and Camptosaurus) in which it is completely excluded (Norman, 2004;Hübner and Rauhut, 2010). Its dorsal process is mediolaterally narrower, with a more pointed dorsal edge in posterior view than those of Lesothosaurus, Orodromeus, Thescelosaurus, Tenontosaurus, Dryosaurus and Dysalotosaurus (Galton, 1983;Scheetz, 1999 Sues, 1980) is present on the supraoccipital as in many early-diverging neornithischians, though it is reduced or absent in Orodromeus (Scheetz, 1999). ...
Haya griva is an early-diverging neornithischian (“hypsilophodontid”) dinosaur known from several well-preserved skulls and articulated postcranial skeletons, in addition to dozens of partial or isolated finds from the Upper Cretaceous Khugenetslavkant and Zos Canyon localities (Javkhlant Formation and equivalent beds) in the Gobi Desert of Mongolia. Collectively, nearly the entire skeletal anatomy of Haya is known, including partial growth series of skulls and femora. Detailed description and comparisons with other ornithischians, including novel anatomical information about the palate and braincase gleaned through high-resolution x-ray microcomputed tomography, reveals a wealth of osteological data for understanding the growth and relationships of this key taxon. Though the Haya specimens span a wide size range, bone histology reveals that all are likely perinatal to subadult individuals, with specimens of intermediate age the most common, and skel- etally mature specimens absent. Phylogenetic analyses place Haya as one of the few Asian members of Thescelosauridae, an important noncerapodan neornithischian group of the Late Cretaceous.
... In Ornithopoda, the endosseous labyrinth followed similar evolutionary patterns, in that early-diverging taxa have a higher and longer anterior semicircular canal and the angle between the anterior semicircular canal and posterior semicircular canal in late-diverging hadrosaurs becomes obtuse (Fig. 6). The semicircular canals of early-diverging ornithopods (e.g., Jeholosaurus) are Galton (1989) and Button and Zanno (2023). Dysalotosaurus from Lautenschlager and Hübner (2013). ...
Ceratopsian dinosaurs underwent great changes, including a shift of locomotion mode, enlarged horns and frills, and increased body size. These changes occur alongside the evolution of endocranial morphology and physiology such as the size and shape of the flocculus, hearing range, olfactory ratio, and the reptile encephalization quotient (REQ). However, the evolution of endocranial structures in early ceratopsians is still unclear because of a lack of information on the earliest ceratopsians. Here, we reconstructed the endocasts of three early-diverging ceratopsians including the Late Jurassic Yinlong , and the Early Cretaceous Liaoceratops and Psittacosaurus . These ceratopsians display obvious flocculi, large and separate olfactory bulbs, long and high anterior semicircular canals, and relatively long cochlear ducts. In the evolution of the earliest ceratopsians to early neoceratopsians, changes include the increasing size of the flocculus (which is reduced or absent in late-diverging ceratopsids), the attenuation of the semicircular canals, and the heightening of the anterior semicircular canal (which is shortened in late-diverging ceratopsids). The endocranial structures suggest early-diverging ceratopsians had a higher olfactory acuity and were adapted to hearing higher frequencies than late-diverging ceratopsians. Furthermore, the REQ suggests that Yinlong and Psittacosaurus were more highly encephalized than late-diverging ceratopsians and most extant reptiles. The angle of the lateral semicircular canal suggests that heads in ceratopsians display a transition from a forward posture to a more downward posture. Our new findings are significant for understanding the physiological changes during ceratopsian evolution and also have implications for the evolution of physiology in extant tetrapods.
... The supraoccipital forms the dorsal margin of the foramen magnum, and roofs the endocranial cavity posterodorsally. The participation of the supraoccipital in the dorsal margin of the foramen magnum is a plesiomorphic feature that Manidens shares with Lesothosaurus (Sereno, 1991;Porro et al., 2015), Heterodontosaurus (Norman et al., 2011), basally branching ornithopods (Galton, 1989;Norman et al., 2004b), stegosaurids (Gilmore, 1914), and protoceratopsids (Brown & Schlaikjer, 1940). In iguanodontians (Norman, 2004), hadrosaurids (Horner et al., 2004), and ceratopsids , the exoccipitals contact each other dorsomedially, excluding the supraoccipital from the dorsal margin of the foramen magnum. ...
Heterodontosauridae is a clade that appears early in the ornithischian fossil record, and includes small-bodied, highly specialized species characterized by an unusual heterodont dentition. Although known from relatively few taxa, the early representation of the clade and unsolved phylogenetic relationships within heterodontosaurids and among early ornithischians implies that novel information has a marked effect on broader phylogenetic hypotheses and our understanding of early diversification patterns within Ornithischia. This paper describes the cranial osteology of the heterodontosaurid Manidens condorensis based on computed micro-tomographic scans of MPEF-PV 3211 and MPEF-PV 3809. This enabled more detailed descriptions of previously recognized bones, corrections to the literature, and the identification of undescribed elements. We present a new skull reconstruction and propose an emended diagnosis in light of novel anatomical information. Areas of jaw muscle attachment were identified and compared with Heterodontosaurus and Lesothosaurus, and mandibular function among heterodontosaurids is discussed. Our results indicate that diverse skull morphologies and functions existed among Early Jurassic ornithischians, with Manidens being intermediate between the plesiomorphic cranial shape and function associated with a generalist diet in ornithischians such as Tianyulong and Lesothosaurus, and the more derived cranial construction specialized for herbivory identified in heterodontosaurids from South Africa such as Heterodontosaurus.
... 7, 10, 18), Owenodon sp. (Galton 2009 : Fig. 19), Tenontosaurus tilletti (Galton 1989 : Fig. 4), Tenontosaurus dossi (Winkler et al. 1997: figs. 6, 7, 8), and an indeterminate iguanodontian from Australia (Bell et al. 2018: Fig. 8). ...
The hadrosauroid Telmatosaurus and the rhabdodontid Zalmoxes were the first and second dinosaur taxa that were described in detail from the famous Upper Cretaceous continental deposits of the Haţeg Basin by Franz Baron Nopcsa at the beginning of the twentieth century. Although they are among the most common and best-known dinosaurs discovered from these deposits, there are still many open questions as to their taxonomy and anatomy. Here, we re-describe two partial braincases from the uppermost Cretaceous of the Haţeg Basin that have been recently referred to the rhabdodontid Zalmoxes and re-assign them to hadrosauroids, possibly to Telmatosaurus . These specimens both exhibit basicranial features that are characteristic of derived hadrosauroids but are absent in more basal iguanodontians. These include an antero-posteriorly short basioccipital lacking a distinct neck, the presence of two well-developed sphenoccipital tubercles on the ventral aspect of the braincase and that are directly positioned anterior to the basioccipital, as well as a deep depression on the ventral aspect of the braincase between the sphenoccipital tubercles. The comparison provided herein demonstrates several important differences between the basicranium of hadrosauroids and that of rhabdodontids, which allows for the confident identification of even isolated and incomplete specimens. Moreover, the removal of the only basicranium that has been referred to Zalmoxes shqiperorum prompts a revised diagnosis of that species.
... For much of its history, paleoneurology was dependent on either fortuitous findings or potentially destructive methods (Buchholtz & Seyfarth, 1999;Edinger, 1938Edinger, , 1941Edinger, , 1975Edinger, 1975;Gaffney, 1977;Galton, 1989Galton, , 2001Hopson, 1979;Jerison, 1973;Newton, 1888;Osborn, 1912;Radinsky, 1968;Stensiö, 1963). Recently, technological advances in computed tomography (CT) scanning have fomented a huge increase in paleoneurological knowledge. ...
... For much of its history, paleoneurology was dependent on either fortuitous findings or potentially destructive methods (Buchholtz & Seyfarth, 1999;Edinger, 1938Edinger, , 1941Edinger, , 1975Edinger, 1975;Gaffney, 1977;Galton, 1989Galton, , 2001Hopson, 1979;Jerison, 1973;Newton, 1888;Osborn, 1912;Radinsky, 1968;Stensiö, 1963). Recently, technological advances in computed tomography (CT) scanning have fomented a huge increase in paleoneurological knowledge. ...
Knowledge on crocodyliform paleoneurology has significantly improved with development of computed tomography. However, studies so far have been able to reconstruct brain endocasts based only on single specimens for each taxon. Here for the first time, we reconstructed brain endocasts for multiple fossil specimens of the same crocodyliform taxon (Baurusuchus), consisting of complete skulls of two medium sized specimens, one large adult, and a late juvenile. In addition, we were able to reconstruct the inner ear anatomy of a fragmentary skull using microtomography. We present estimates of brain size using simple models, based on modern Crocodylia, able to adapt brain to endocranial cavity ratios to expected ontogenetic variation instead of using fixed ratios. We also analyzed relative brain sizes, olfactory ratios, facial sensation, alert head posture, best hearing frequencies, and hearing range. The calculated endocranial volumes showed that they can be greatly altered by taphonomic processes, altering both total and partial endocranial volumes. Reconstructed endocasts are compatible with different degrees of occupation along the endocranial cavity and some of their characteristics might be useful as phylogenetic characters. The relative brain size of Baurusuchus seems to be small in comparison to modern crocodilians. Sensorial abilities were somewhat similar to modern crocodilians and hearing ranges and best mean frequencies remarkably similar to modern taxa, whereas olfactory ratio values are a little higher. Differing from its modern relatives, Baurusuchus hypothesized alert head posture is compatible with a terrestrial habit.
Thescelosaurines are a group of early diverging, ornithischian dinosaurs notable for their conservative bauplans and mosaic of primitive features. Although abundant within the latest Cretaceous ecosystems of North America, their record is poor to absent in earlier assemblages, leaving a large gap in our understanding of their evolution, origins, and ecological roles. Here we report a new small bodied thescelosaurine—Fona herzogae gen. et sp. nov.—from the Mussentuchit Member of the Cedar Mountain Formation, Utah, USA. Fona herzogae is represented by multiple individuals, representing one of the most comprehensive skeletal assemblages of a small bodied, early diverging ornithischian described from North America to date. Phylogenetic analysis recovers Fona as the earliest member of Thescelosaurinae, minimally containing Oryctodromeus, and all three species of Thescelosaurus, revealing the clade was well‐established in North America by as early as the Cenomanian, and distinct from, yet continental cohabitants with, their sister clade, Orodrominae. To date, orodromines and thescelosaurines have not been found together within a single North American ecosystem, suggesting different habitat preferences or competitive exclusion. Osteological observations reveal extensive intraspecific variation across cranial and postcranial elements, and a number of anatomical similarities with Oryctodromeus, suggesting a shared semi‐fossorial lifestyle.
Southern polar biotas of the Early Cretaceous (Valanginian-early Albian) of south-central Victoria, Australia, contain > 150 taxa of plants, invertebrates, and vertebrates, including dinosaurs, fish, possibly a labyrinthodont amphibian, turtles, lepidosaurs, pterosaurs, freshwater plesiosaurs, theropods, and birds, but thus far no crocodiles or mammals. The fossil-producing sediments are the Otway and Strzelecki Groups, which some authors combine into one unit, the Korumburra Group. They represent volcanogenic clays, silts, and sands deposited in several different facies of braided river systems that occupied a down-dropped graben created when Australia and Antarctica began to separate in the late Mesozoic. Periodicity in the sedimentation regime may have been related to meltwater floods in the austral spring. Invertebrates, plants, and geochemistry suggest that a cool, humid climate prevailed. paleomagnetic studies on the Otway Group indicate that southern Victoria was situated at a high latitude, between 70 and 85° south, in the late Early Cretaceous. -from Authors