[dinosaur] Jurassic euharamiyidan mammaliaform auditory and hyoid bones

Ben Creisler
[email protected]

A new paper:


Jin Meng, Fangyuan Mao, Gang Han, Xiao‐Ting Zheng, Xiao‐Li Wang  & Yuanqing
Wang (2019)
A comparative study on auditory and hyoid bones of Jurassic euharamiyidans
and contrasting evidence for mammalian middle ear evolution.
Journal of Anatomy (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_joa.13083&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=nvWIuny0UBqQ0m8ucvUD85LM-N834IQv8jXVrFevLzA&s=CmG4q6f0-kBvyCuogzyxQonuhOJiG4SmgzC_vDGbmSk&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1111_joa.13083&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=nvWIuny0UBqQ0m8ucvUD85LM-N834IQv8jXVrFevLzA&s=BZmmw8O12yAEfCiNnDLE9Y9Rz9s2vmPQ5KLz2IJTCT4&e= 


The holotypes of euharamiyidan Arboroharamiya allinhopsoni and
Arboroharamiya jenkinsi preserve the auditory and hyoid bones,
respectively. With additional structures revealed by micro‐computerized
tomography (CT) and X‐ray micro‐computed laminography (CL), we provide a
detailed description of these minuscule bones. The stapes in the two
species of Arboroharamiya are similar in having a strong process for
insertion of the stapedius muscle. The incus is similar in having an
almond‐shaped body and a slim short process, in addition to a robust
stapedial process with a short lenticular process preserved in A.
allinhopsoni. The plate‐like ectotympanic in the two species of
Arboroharamiya is similar and comparable to that of Qishou jizantang. The
surangular in the two species has a fan‐shaped body and a needle‐shaped
anterior process. The malleus, ectotympanic, and surangular are fully
detached from the dentary and should have functioned exclusively for
hearing. All the auditory bones of Arboroharamiya display unique features
unknown in other mammaliaforms. Moreover, hyoid elements are found in the
two species of Arboroharamiya and co‐exist with the five auditory bones in
the holotype of A. allinhopsoni. The element interpreted as the stylohyal
is similar to the bone identified as the ectotympanic in Vilevolodon. We
reconstruct the auditory apparatus of Arboroharamiya and compare it with
that of Vilevolodon as well as those in extant mammals and basal
mammaliaforms. The comparison shows diverse morphological patterns of the
auditory region in mammaliaforms. In particular, those of Vilevolodon and
Arboroharamiya differ significantly: the former has a mandibular middle
ear, whereas the latter possesses a definitive mammalian middle ear. It is
puzzling that the two sympatric and dentally similar taxa have such
different auditory apparatuses. In light of the available evidence, we
argue that the mandibular middle ear reconstructed in Vilevolodon
encounters many problems, and the so‐called ectotympanic in Vilevolodon may
be interpreted as a stylohyal; thus, the dilemma can be resolved.

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