Data from: Morphology of the petrosal and stapes of Borealestes (Mammaliaformes, Docodonta) from the Middle Jurassic of Skye, Scotland

\We describe, in unprecedented detail, the petrosals and stapes of the docodont Borealestes from the Middle Jurassic of Scotland, using high resolution μCT and phase‐contrast synchrotron imaging. We describe the inner ear endocast and the vascularized interior structure of the petrosal, and provide the first endocranial view of a docodontan petrosal. Our study confirms some similarities in petrosal and stapedial morphology with the better known Haldanodon of the Late Jurassic of Portugal, including: (1) the degree of curvature of the cochlea; (2) multiple features related to the highly pneumatized paroccipital region; (3) the shape of lateral trough, the fossa of the M. tensor tympani, and the ridge on the promontorium; (4) the round shape of the fenestra vestibuli; and (5) overall morphology of the stapes. But Borealestes differs from Haldanodon in having a bony ridge that separates the tympanic opening of the prootic canal, the secondary facial foramen and the hiatus Fallopii, from the fenestra vestibuli. We identify two new vascular structures: the anterior and posterior trans‐cochlear sinuses, which traverse the pars cochlearis around the cochlear nerve (VIII). These trans‐cochlear sinuses have not been observed in previous docodont specimens, and could be an autapomorphy of Borealestes, or apomorphic for this clade. We also establish the anatomical relationship of the circum‐promontorium plexus to the inner endocast. The high quality of our scans has made these structures visible for the first time.

Usage Notes:
NMS G.1992.47.121.1 R. petrosal reconstruction with Stapes
The right petrosal of Borealestes, NMS G.1992.47.121.1 with broken fragments of promontorium reconstructed, and stapes placed in life position. Digital reconstruction based on synchrotron scan data. Part of more complete skeleton NMS G.1992.47.121.1.
NMS G.1992.47.121.1_R.petrosal.recon.wStapes.stl
NMS G.1992.47.121.1 R. petrosal of Borealestes
The right petrosal of Borealestes, NMS G.1992.47.121.1, as preserved. Digital reconstruction based on synchrotron scan data. Part of more complete skeleton NMS G.1992.47.121.1.
NMS G.1992.47.121.1_R.petrosal.stl
NMS G.1992.47.121.1 R.stapes of Borealestes
The right stapes of Borealestes, NMS G.1992.47.121.1. Digital reconstruction based on synchrotron scan data. Part of more complete skeleton NMS G.1992.47.121.1.
NMS G.1992.47.121.1_R.stapes.stl
NMS G.1992.47.121.2 L. petrosal reconstruction with Stapes
The left petrosal of Borealestes, NMS G.1992.47.121.2, with fragments reconstructed into life position, and stapes in position. Digital reconstruction from microCT scan data. Part of more complete skeleton NMS G.1992.47.121.1.
Left_petrosal_alltogether.stl
NMS G.1992.47.121.2 L. petrosal of Borealestes
The left petrosal of Borealestes, NMS G.1992.47.121.2. Digital reconstruction from microCT scan data. Part of more complete skeleton NMS G.1992.47.121.1.
Left_petrosal.stl

Panciroli, Elsa; Schultz, Julia A.; Luo, Zhe-Xi (2019). Data from: Morphology of the petrosal and stapes of Borealestes (Mammaliaformes, Docodonta) from the Middle Jurassic of Skye, Scotland [Dataset]. Dryad. https://doi.org/10.5061/dryad.07934k0