Paranasal sinus system and upper respiratory tract evolution in Mesozoic pelagic crocodylomorphs

Resource type
Journal article
Creator (person)
Cowgill, Thomas
Young, Mark T
Schwab, Julia A
Walsh, Stig
Witmer, Lawrence M
Herrera, Yanina
Dollman, Kathleen N
Choiniere, Jonah N
Brusatte, Stephen L
Date published
August 16, 2021
Abstract
Thalattosuchians were a predominately marine clade of Mesozoic crocodylomorphs, including semi-aquatic teleosauroid and obligately pelagic metriorhynchid subclades. Recent advances in our understanding of thalattosuchian endocranial anatomy have revealed new details of the evolutionary transition from terrestrial to marine to pelagic taxa. Paranasal sinuses, however, have received little attention. Herein, we investigate the evolution of the paranasal sinus system and part of the upper respiratory system (nasopharyngeal ducts) in Thalattosuchia, by reconstructing the nasal and paranasal anatomy in CT scans of seven thalattosuchian skulls: one teleosauroid, two basal metriorhynchoids and four metriorhynchids. Our outgroups were: three extant crocodylian species (including adult and subadult skulls) and the basal crocodyliform Protosuchus. We found thalattosuchians exhibit exceptionally reduced paranasal sinus systems, solely comprising the antorbital sinus, as has been previously proposed. The semi-aquatic basal thalattosuchians Palgiopthalmosuchus gracilirostris and Pelagosaurus typus both have an antorbital sinus partially located medial to a reduced external antorbital fenestra and broadly communicating with the dorsal alveolar canal. In pelagic metriorhynchids, the antorbital cavity is more extensive than in basal taxa and possibly had an active function associated with a hypothesized accessory suborbital diverticulum, but our reconstructions are insufficient to confirm or reject the presence of such a diverticulum. The nasopharyngeal ducts of metriorhynchids are dorsoventrally enlarged, possibly enabling stronger ventilation. The sequence of acquisition of craniofacial adaptations show a mosaic pattern and appears to predate many skeletal adaptations, suggesting these changes occurred early in the thalattosuchian marine transition.
Funder
Funder nameAwards
Leverhulme Trust
RPG†2017†167
Agencia Nacional de Promocià³n Cientà­fica y Tecnolà³gica
2016†0267
Journal title
The Anatomical Record
Publisher
Wiley
ISSN
1932-8486
eISSN
1932-8494
Official URL
Rights statement
In Copyright
DOI