[dinosaur] Mesozoic stem therian inner ear (free pdf)

Ben Creisler
[email protected]

A new paper:


Free pdf:

Tony Harper & Guillermo W. Rougier (2019)
Petrosal morphology and cochlear function in Mesozoic stem therians.
PLoS ONE 14(8): e0209457
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1371_journal.pone.0209457&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=pe9aHuVi7TA1uwLPDj3zTrdZoE_l7nwduHVUmuv_7Rs&s=nzIcRW7IfzfD5ZsVXZWbZtqvmoTGYWoalCaG1Nsr8cU&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.plos.org_plosone_article-3Fid-3D10.1371_journal.pone.0209457&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=pe9aHuVi7TA1uwLPDj3zTrdZoE_l7nwduHVUmuv_7Rs&s=LYnAFScS5dHYY1p5p0XWLBQ5CRAHGUWi2U6JE-0EKiE&e= 

Free pdf:
https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.plos.org_plosone_article_file-3Fid-3D10.1371_journal.pone.0209457-26type-3Dprintable&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=pe9aHuVi7TA1uwLPDj3zTrdZoE_l7nwduHVUmuv_7Rs&s=7l5Yw5KHY6RklWH5111UA6veV67gmWUpYxMVfPrvOaA&e= 


Here we describe the bony anatomy of the inner ear and surrounding
structures seen in three plesiomorphic crown mammalian petrosal specimens.
Our study sample includes the triconodont Priacodon fruitaensis from the
Upper Jurassic of North America, and two isolated stem therian petrosal
specimens colloquially known as the Höövör petrosals, recovered from
Aptian-Albian sediments in Mongolia. The second Höövör petrosal is here
described at length for the first time. All three of these petrosals and a
comparative sample of extant mammalian taxa have been imaged using
micro-CT, allowing for detailed anatomical descriptions of the osteological
correlates of functionally significant neurovascular features, especially
along the abneural wall of the cochlear canal. The high resolution imaging
provided here clarifies several hypotheses regarding the mosaic evolution
of features of the cochlear endocast in early mammals. In particular, these
images demonstrate that the membranous cochlear duct adhered to the bony
cochlear canal abneurally to a secondary bony lamina before the appearance
of an opposing primary bony lamina or tractus foraminosus. Additionally,
while corroborating the general trend of reduction of venous sinuses and
plexuses within the pars cochlearis seen in crownward mammaliaforms
generally, the Höövör petrosals show the localized enlargement of a portion
of the intrapetrosal venous plexus. This new vascular feature is here
interpreted as the bony accommodation for the vein of cochlear aqueduct, a
structure that is solely, or predominantly, responsible for the venous
drainage of the cochlear apparatus in extant therians. Given that our
fossil stem therian inner ear specimens appear to have very limited
high-frequency capabilities, the development of these modern vascular
features of the cochlear endocast suggest that neither the initiation or
enlargement of the stria vascularis (a unique mammalian organ) was
originally associated with the capacity for high-frequency hearing or
precise sound-source localization.

==