Paratympanic sinuses in juvenile Alligator

Abstract

Crocodylia has an extensive epithelial pneumatic space in the middle ear, paratympanic sinus system. Although fossil and extant crocodylian paratympanic sinus systems have been studied recently using the computed tomography (CT) and three‐dimensional (3D) reconstruction data, due to the soft tissue nature of the pneumatic system and presence of its surrounding soft tissue structures, some boundaries, and definitions of each extension remain ambiguous. We describe the comprehensive paratympanic sinus system in posthatched alligator using soft tissue enhanced CT data with 3D reconstructions. The data are compared to the available data to discuss the ontogenetic pattern in alligator. We introduce further divided entities of the pneumatic system based on their associated bony and soft tissue structures and epithelial membrane and clarify the pneumatic terminologies. We then re‐visit the potential homology of the paratympanic sinus in Archosauria. Epithelial boundaries of the ventral portion of the pneumatic system from the histological data suggest that the dual origin of the basioccipital diverticulum derived from the tympanic sinus and basicranial diverticulum medially. The presence of the epithelial boundary and pneumatic changes in ontogeny suggests that the middle ear may function differently in developmental stages. Lastly, a morphogenetic tree is constructed to help future work of comparative developmental studies of the paratympanic sinus system between crocodiles and birds.

Increasing the impact of vertebrate scientific collections through 3D imaging: The openVertebrate (oVert) Thematic Collections Network

“…Another obvious benefit is that a specimen may be used in different projects by multiple researchers at any given time. For example, during a 3-year period (2020–2022), more than 43 unique users downloaded the same data set of a gharial skull ( Gavialis gangeticus ; UF: Herp:118,998; https://doi.org/10.17602/M2/M39794 ), resulting in at least 10 publications from authors in seven countries (Hone et al 2020 , Bowman et al 2021 , Cowgill et al 2021 , 2022 , Pochat-Cottilloux et al 2021 , Serrano-Martínez et al 2021 , Iijima et al 2022 , Schwab et al 2022 a, 2022b, Tahara and Larsson 2022 ). These digital data grow the number of researchers able to interact with specimens, especially people from Low and Middle Income Countries lacking local collections or the resources to travel to other collections.…”

Neuroanatomy and pneumaticity of the extinct Malagasy “horned” crocodile Voay robustus and its implications for crocodylid phylogeny and palaeoecology

“…In V. robustus it is ellipsoidal in shape, has a mean height of 3.2 mm, and 6.2 mm in anteroposterior length. The fenestra ovalis communicates with the stipedial diverticulum of the middle ear (StiPR, Figure 11a,c; Tahara & Larsson, 2022). The perilymphatic foramen lies posteroventrally to the fenestra ovalis ; it links the endosseous labyrinth to the extracapsular portion of the perilymphatic sac (Kuzmin et al, 2021).…”

The anatomical basis of amphibious hearing in the American alligator (Alligator mississippiensis)

“…Earlier studies have examined the earflaps; testing for possible acoustic filtering (Wever & Vernon, 1957) or alteration of the impedance matching by trapping air bubbles (Higgs et al, 2002), but no significant auditory role has been found. The middle ear cavities of crocodilians are linked by dorsal and paired ventral paratympanic passages (e.g., Dufeau & Witmer, 2015; Tahara & Larsson, 2022). The ventral paratympanic passages open into the pharynx through a muscular valve (Owen, 1850); examination suggests that this valve does not play an auditory function (Young & Bierman, 2019).…”