Anatomy of the premaxilla of Tylosaurus nepaeolicus (Squamata: Mosasauroidea) and its implications in the sensoriality of aquatically adapted squamates

JIMENEZ-HUIDOBRO, P.; PAULINA CARABAJAL, A.; CALDWELL, M.

Cairns

Congreso; International Congress of Vertebrate Morpohology; 2023

International SOciety for Vertebrate Morphology

Mosasauroidea represent a unique body plan within Squamata: elongated body with amodification of the pelvic girdle and reduction of limb bones to form paddle-like appendages. Adaptations of mosasaurs to aquatic environments have been mostly studied from the perspective of anatomical modifications at a postcranial level. In contrast, little is known about cranial adaptations, including skeletal and soft parts, which have been mostly focused on middle and inner ear. It is widely accepted that there is a relationship between the vestibular apparatus and functional aspects of the animal’s biology, but other neurological and sensory aspects of the skeleton have not been studied in Mesozoic aquatic squamates. Here, we analysed the premaxilla of a juvenile Tylosaurus nepaeolicus from the Cretaceous of Kansas using mCT scanning. The obtained images show the correlation of the neurovascular system on the wall of the nasal cavity, in accordance with the high density of foramina observed in the external side of the premaxilla and maxillae. The relative development of different regions of the nasal cavity might affect the olfaction, respiration, and ultimately the thermoregulation of mosasauroids. Innervation and irrigation of the premaxilla are discussed in relation to possible sensory adaptations to the aquaticenvironment. The obtained anatomical information shed light on the sensory mechanisms in the evolution and success of one of the most specialised groups in the history of Squamata.