A potential link between lateral semicircular canal orientation, head posture, and dietary habits in extant rhinos (Perissodactyla, Rhinocerotidae)

Schellhorn, Rico

doi:10.1002/jmor.20753

Cited by 16 publications

(24 citation statements)

References 47 publications

(94 reference statements)

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“…In contrast, Igarashi and Yoshinobu () report 2.5–2.75 turns, what is likely due to different starting points for the coil count. The orientation of the LSC within the skull described by the deviation of the LSC plane from the palatal plane (total range of sample: 25.2°–37.0°, Table b) fit the former published results of 32.42° (Blanks et al, ) and 34° [(Money, Johnson, & Corlett, ); compare also data on extant rhinos (Schellhorn, ) and xenarthrans (Coutier, Hautier, Cornette, Amson, & Billet, )].…”

Section: Discussionsupporting

confidence: 80%

Intraspecific variation in the domestic cat bony labyrinth revealed by different measurement techniques

Schellhorn

2017

Journal of Morphology

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The knowledge of intraspecific variation is important to make assumptions on an interspecific level. To study intraspecific variation in the bony labyrinth morphology of the domestic cat, eleven specimens of Felis silvestris catus and two additional subspecies (F. s. lybica, F. s. ornata) were investigated. The sample comprises skulls of adult males and females, as well as juvenile cats. Each bony labyrinth endocast was virtually reconstructed based on µCT scans. To estimate the radius of curvature of each inner ear semicircular canal, three different approaches were tested. The comparison of the different methods resulted in different absolute values for the measured radii. The assumed best structure to precisely characterize the size of a semicircular canal is the inner perimeter. Within the tested sample, the anterior semicircular canal is always the largest, while the posterior semicircular canal is the second largest and the lateral semicircular canal the smallest in most cases. The coefficient of variation lies below 10% for all bony labyrinth measurements within the sample. The inner perimeter values of each semicircular canal are similar within all investigated specimens, even though the skull length of adult cats is twice as long as that of juvenile cats. Thus, inner ear biometry of the domestic cat seems stable throughout growth series and can therefore be used for systematic and ecological studies and the inclusion of juvenile individuals is reasonable. It is noteworthy that the inner perimeter values of the semicircular canals do not vary as much as the values of the angles spanned between the three canals within the sample. The inner ear within the cat skull is oriented about 25° to 31° to the palate (angle between the plane anchored to the lateral semicircular canals (SC) and the plane anchored to the palate). The cochlea coils between 3.00 and 3.25 turns in the investigated sample.

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Section: Discussionsupporting

confidence: 80%

Intraspecific variation in the domestic cat bony labyrinth revealed by different measurement techniques

Schellhorn

2017

Journal of Morphology

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“…The lateral canal of C. lindoei is angled approximately −15.8° to the long axis of the skull, and the lateral canal of C. natator is angled approximately 13.3° to the long axis of the skull, a difference of approximately 29°. Previously, the angle of the lateral canal relative to the long axis of the skull has been used to reconstruct head posture in extinct taxa [99][100][101] , but some evidence suggests that the angle of the lateral canal is highly variable and does not accurately reflect head posture in some groups of animals (e.g., saurischians 16 ). The variation in the lateral canal of Champsosaurus supports the notion that the angle of the lateral canal can be highly variable, as Champsosaurus species are thought to have had similar ecologies and behaviour to one another 18 and are therefore unlikely to have had significantly different habitual head postures.…”

Section: Resultsmentioning

confidence: 99%

The internal cranial anatomy of Champsosaurus (Choristodera: Champsosauridae): Implications for neurosensory function

Dudgeon

Maddin

Evans

et al. 2020

Sci Rep

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Although isolated Champsosaurus remains are common in Upper cretaceous sediments of north America, the braincase of these animals is enigmatic due to the fragility of their skulls. Here, two wellpreserved specimens of Champsosaurus (CMN 8920 and CMN 8919) are CT scanned to describe their neurosensory structures and infer sensory capability. the anterior portion of the braincase was poorly ossified and thus does not permit visualization of a complete endocast; however, impressions of the olfactory stalks indicate that they were elongate and likely facilitated good olfaction. the posterior portion of the braincase is ossified and morphologically similar to that of other extinct diapsids. The absence of an otic notch and an expansion of the pars inferior of the inner ear suggests Champsosaurus was limited to detecting low frequency sounds. comparison of the shapes of semicircular canals with lepidosaurs and archosauromorphs demonstrates that the semicircular canals of Champsosaurus are most similar to those of aquatic reptiles, suggesting that Champsosaurus was well adapted for sensing movement in an aquatic environment. this analysis also demonstrates that birds, non-avian archosauromorphs, and lepidosaurs possess significantly different canal morphologies, and represents the first morphometric analysis of semicircular canals across Diapsida.Palaeoneurology, the study of the brain in the fossil record and how it has changed through time 1 , provides some of the best evidence for how extinct animals behaved and interacted with their environment. The behaviour and sensory abilities of extinct taxa are inferred based on the morphology of regions of the brain that are directly responsible for processing sensory information and forming behaviour. Other neural structures are often included in palaeoneurological studies, such as the cranial nerves and membranous labyrinth, which transmit sensory and motor information to and from the brain, and facilitate the sensation of movement and orientation, respectively. Estimations of sensory ability and behaviour based on the morphology of the brain are made possible by the principle of proper mass, which states that the size of a brain region dedicated to a specific function is directly correlated with the amount of processing power required to complete that function 2 . Therefore, regions of the brain that require more processing power tend to be larger to accommodate a greater number of neurons.This correlation allows hypotheses to be made about the sensory ability of extinct animals based on the morphology of the brain; 3,4 however, the brain endocast is not a perfect reflection of the brain in life, as it also represents other soft-tissue structures housed within the endocranial cavity that did not fossilize, such as the dura matter and vascular tissue 5 . Despite this, a description of the endocranial cavity of an extinct animal provides data that can be used to infer its neurosensory capabilities by comparison to closely related extant taxa, which allows for the formation o...

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“…occipital position) (Sereno et al . ; Neenan & Scheyer ; Schellhorn ). If LSC orientation does show a behavioural and/or ecological signal, the range of LSC orientations recorded in the two specimens of P. fergusi indicate an upturned head posture and could be interpreted as an adaption to semi‐aquatic life.…”

Section: Discussionmentioning

confidence: 99%

Endocranial anatomy and life habits of the Early Triassic archosauriformProterosuchus fergusi

et al. 2019

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Proterosuchids are an important group of carnivorous basal archosauriforms characterized by a bizarre and enigmatic downturned premaxilla that overhangs the lower jaw. They are particularly significant because they radiated in the immediate aftermath of the Permian–Triassic mass extinction and represent one of the best known ‘disaster taxa’ following that event. While traditionally considered to be semi‐aquatic, recent histological studies and geological data have suggested that it is more likely that they inhabited terrestrial environments. By using computed tomographic (CT) data, we virtually reconstruct the brain endocast and endosseous labyrinths of two adult specimens of Proterosuchus fergusi from the earliest Triassic of South Africa, in an attempt to understand its life habits within the context of basal archosauriform evolution. Endocasts reveal that the brain cavity is tubular in shape and the endosseous labyrinths are highly pyramidal. The angle of the lateral semicircular canal suggests that P. fergusi naturally held its head upwards ~17°, while the length of the cochlear duct suggests its auditory abilities were specialized towards low‐frequency sounds. Furthermore, beam theory analysis suggests that the rostrum of P. fergusi is highly resistant to both bending and torsion when compared to modern crocodilians, although this resistance is neither enhanced nor reduced by the overhanging premaxilla. Comparative anatomical analyses suggest P. fergusi was probably a semi‐aquatic, generalist apex predator capable of surviving the harsh environmental perturbations of the Early Triassic.

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A potential link between lateral semicircular canal orientation, head posture, and dietary habits in extant rhinos (Perissodactyla, Rhinocerotidae)

Cited by 16 publications

References 47 publications

Intraspecific variation in the domestic cat bony labyrinth revealed by different measurement techniques

Intraspecific variation in the domestic cat bony labyrinth revealed by different measurement techniques

The internal cranial anatomy of Champsosaurus (Choristodera: Champsosauridae): Implications for neurosensory function

Endocranial anatomy and life habits of the Early Triassic archosauriformProterosuchus fergusi

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