[dinosaur] Protoichthyosaurus skull roof

Ben Creisler
[email protected]

A new paper:

Dean R. Lomax, Judy A. Massare and Mark Evans (2019)
New information on the skull roof of Protoichthyosaurus (Reptilia:
Ichthyosauria) and intraspecific variation in some dermal skull elements.
Geological Magazine (advance online publication)
DOI: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1017_S0016756819001225&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=XBNm0irdTwzsuZ-2344-XTZ7t_i7C2YQ2YNrWNk3ezs&s=vjvECujOWcDwABgbjazD94aAmftjeKRaNNFsXpouBtM&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.cambridge.org_core_journals_geological-2Dmagazine_article_new-2Dinformation-2Don-2Dthe-2Dskull-2Droof-2Dof-2Dprotoichthyosaurus-2Dreptilia-2Dichthyosauria-2Dand-2Dintraspecific-2Dvariation-2Din-2Dsome-2Ddermal-2Dskull-2Delements_6E2C7E156C080136B37C5A7363DC63AE&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=XBNm0irdTwzsuZ-2344-XTZ7t_i7C2YQ2YNrWNk3ezs&s=Ga0SmK2YRfkCHTdVFFeeISMlDIbABb0gdGIkMz_gY0Q&e= 

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https://urldefense.proofpoint.com/v2/url?u=https-3A__www.cambridge.org_core_journals_geological-2Dmagazine_article_new-2Dinformation-2Don-2Dthe-2Dskull-2Droof-2Dof-2Dprotoichthyosaurus-2Dreptilia-2Dichthyosauria-2Dand-2Dintraspecific-2Dvariation-2Din-2Dsome-2Ddermal-2Dskull-2Delements_6E2C7E156C080136B37C5A7363DC63AE_share_bc38c7d563777237bf58ac158bfdb1fd1c56eb30&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=XBNm0irdTwzsuZ-2344-XTZ7t_i7C2YQ2YNrWNk3ezs&s=ChJrOgZgX0dLcsoFFqt7y1rMenOzyvBl6hKfGAB-E_E&e= 


A previously unrecognized specimen of Protoichthyosaurus prostaxalis, LEICT
G142.1991, from the Lower Jurassic of Barrow-upon-Soar, Leicestershire, UK,
includes an almost complete three-dimensional skull that provides new
information on the configuration of the skull roof. The position of the
pineal foramen (between the frontals and the parietals) and an elongated
internasal foramen in a depression along the midline of the nasals are
clearly shown. The maxilla makes up a significant portion of the external
naris ventral margin, an unusual character for the genus/species. This
reflects intraspecific variation, not evidence of a new taxon. The specimen
enables comparisons of skull roof morphology with Ichthyosaurus and
Stenopterygius, two common Early Jurassic taxa. In particular, the position
of the pineal foramen is similar to Stenopterygius, but distinguishes
Protoichthyosaurus from Ichthyosaurus. The lack of a frontal–prefrontal
contact and the posteriorly wide nasals distinguishes Protoichthyosaurus
from Stenopterygius. We also present a revised reconstruction of the skull
roof morphology of Ichthyosaurus. Three additional specimens of
Protoichthyosaurus are referred to the genus: another partial skull,
referred to P. prostaxalis, and two isolated forefins, identified by their
unique morphology.