[dinosaur] Arthropterygius thalassonotus, new ichthyosaur species from Late Jurassic of Argentina

Ben Creisler
[email protected]

A new paper:

Arthropterygius thalassonotus sp. nov.

Lisandro Campos, Marta S. Fernández &  Yanina Herrera (2019)
A new ichthyosaur from the Late Jurassic of north-west Patagonia
(Argentina) and its significance for the evolution of the narial complex of
the ophthalmosaurids.
Zoological Journal of the Linnean Society, zlz095 (advance online
publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1093_zoolinnean_zlz095&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=jssInAbC69smWrlvwGOONMJHDuWfvVgkJSzoFZ9S-zs&s=4QlyP7lSuvrl3OLTEPpUlXbXk3bju-w8hS7ULI3m-4Y&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__academic.oup.com_zoolinnean_advance-2Darticle-2Dabstract_doi_10.1093_zoolinnean_zlz095_5602983&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=jssInAbC69smWrlvwGOONMJHDuWfvVgkJSzoFZ9S-zs&s=oqDHNyTv9AE_h4_IGxfGnGCE-vTypd2gt3ZK3wns7hM&e= 



Ophthalmosaurids were highly derived and the youngest clade of
ichthyosaurs. Their evolutionary history comprises ~76 Myr (from the early
Middle Jurassic to the final extinction of the group at the
Cenomanian–Turonian boundary). Fossil records indicate that soon after they
emerged they achieved a widespread geographical distribution. Analyses of
disparity based on craniodental morphologies, and the co-occurrence of
different bone histology and microstructure among the members of the group,
indicate that ophthalmosaurids are not only taxonomically but also
ecologically diverse. A region of the skull that is particularly complex
among ophthalmosaurid taxa is the external nares and surrounding areas, but
there have been few attempts to explore this topic. We describe a new
ophthalmosaurid from the Late Jurassic of Patagonia (Argentina) in the
genus Arthropterygius and analyse its phylogenetic relationships. A
detailed exploration of the skull, using computed tomography, reveals the
division of the external nares by means of a stout bony pillar. This
condition was previously known only in some Cretaceous forms and, within a
phylogenetic framework, its distribution among ophthalmosaurids indicates
that this morphology was the result of convergent evolution. Based on
available data on extant (and some extinct) forms, we explore putative soft
structures involved in the narial region. We propose that the division of
the external nares (complete or partly osseous) was related functionally to
the separation of the air passage from the outlet of nasal salt glands in
such a way that the salt glands could be evacuated underwater, while the
air passage could be closed by a valvular system.