Figure 5 - available via license: Creative Commons Attribution 4.0 International
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Four views of the left bony labyrinth of SDSNH 47878. A, rostral view; B, lateral view; C, caudal view; D, medial view. Abbreviations: ASC, anterior semicircular canal; CC, common crus; Co, cochlea; LSC, lateral semicircular canal; PSC, posterior semicircular canal.
Source publication
Leptoreodon is a basal member of the Protoceratidae, an extinct group of artiodactyls variably allied with the Camelidae and the Ruminantia. The basicranial morphology of other protoceratids (Leptotragulus, Protoceras, Syndyoceras) is similar to that of ruminants, supporting the hypothesis that the two clades are closely related. However, study of...
Context in source publication
Context 1
... bony labyrinths of both ears are preserved. The left bony labyrinth is more nearly complete and is the primary basis of this description (Fig. 5). The cochlear canal makes approximately 2.5 turns (rotation of 900°). The vestibule, consisting of the saccule (spherical recess) and utricle (elliptical recess), could be partially reconstructed, but the shape is indistinct because of poor preservation. The vestibular aqueduct is a long and narrow channel that originates from the ...
Citations
Bats form a diverse group of mammals that are highly specialized in active flight and ultrasound echolocation. These specializations rely on adaptations that reflect on their morphoanatomy and have been tentatively linked to brain morphology and volumetry. Despite their small size and fragility, bat crania and natural braincase casts ("endocasts") have been preserved in the fossil record, which allows for investigating brain evolution and inferring paleobiology. Advances in imaging techniques have allowed virtual extraction of internal structures, assuming that the shape of the endocast reflects soft organ morphology. However, there is no direct correspondence between the endocast and internal structures because meninges and vascular tissues mark the inner braincase together with the brain they surround, resulting in a mosaic morphology of the endocast. The hypothesis suggesting that the endocast reflects the brain in terms of both external shape and volume has drastic implications when addressing brain evolution, but it has been rarely discussed. To date, only a single study addressed the correspondence between the brain and braincase in bats. Taking advantage of the advent of imaging techniques, we reviewed the anatomical, neuroanatomical, and angiological literature and compare this knowledge available on bat's braincase anatomy with anatomical observations using a sample of endocranial casts representing most modern bat families. Such comparison allows to propose a Chiroptera-scale nomenclature for future descriptions and comparisons among bat endocasts. Describing the imprints of the tissues surrounding the brain also allows to address to what extent brain features can be blurred or hidden (e.g., hypophysis, epiphysis, colliculi, flocculus). Furthermore, this approach encourages further study to formally test the proposed hypotheses.
