Morphology of the Middle Ear in Three Species of Armadillos (Dasypodidae, Xenarthra) from Argentina

Abstract

. Morphology of the middle ear in three species of armadillos (Dasypodidae, Xenarthra) from Argentina. Int. J. Morphol., 30(4):1500-1507, 2012. SUMMARY:Middle ears of adult Chaetophractus villosus, C. vellerosus and Zaedyus pichiy were studied for qualitative and quantitative comparisons. A great similarity in the overall shape of the middle ear structures was observed in the three species. The well-developed auditory bulla was formed by the intimate fusion of the tympanic and entotympanic. Internally, a recessus meatus and a wide epitympanic recess extending dorsally into an epitympanic sinus were recognized. The petrosal promontorium, nearly triangular, was the most salient feature in the tympanic cavity. The auditory ossicles corresponded to the transitional middle ear type. The m. tensor tympani and the m. stapedius were conspicuous. The lack of a stapedial artery was confirmed in all cases. The tympanic area and middle ear ossicles were relatively larger in C. vellerosus than in the other two species. It is hoped that the results of the present paper coupled to the bullar hypertrophy found in a previous work will provide a significant basis for future functional studies on the hearing capabilities in the dasypodids.

The middle ear of the pink fairy armadillo Chlamyphorus truncatus (Xenarthra, Cingulata, Chlamyphoridae): comparison with armadillo relatives using computed tomography

“…Our findings regarding the morphology of the middle ear of C. truncatus and its relatives are broadly in agreement with previous descriptions in the literature (Doran, ; Fleischer, ; Segall, ; Novacek & Wyss, ; Patterson et al , ; Sidorkewicj & Casanave, ). We begin by comparing our results to these published descriptions.…”

“…It was clear from our scans and reconstructions that the stapes instead articulates directly with the flattened, spatulate end of the incudal long process. We suspect that previous descriptions of a lenticular apophysis in armadillos (Fleischer, ; Sidorkewicj & Casanave, ) were based either on interpreting the flattened articulation facet on the long process of the incus as the apophysis, or on specimens in which the stapes head had broken from the stapes body and remained in articulation with the incus. The lack of a pedicellate lenticular apophysis is highly unusual among mammals but has previously been documented in monotremes, cetaceans and sirenians (Fleischer, , ).…”

“…Finally, Sidorkewicj & Casanave () found a small pars flaccida in the Euphractinae. This membrane could not be seen directly in the prepared skulls examined.…”

“…Segall’s illustrations of the malleus show an ossicle completely lacking an anterior process, which he described as ‘short’, but our CT scans revealed the presence of a long anterior process, as noted by Fleischer (). Detachment of the malleus from the ectotympanic in armadillos usually involves the breakage of the anterior process (see also Sidorkewicj & Casanave, ; pers. obs.).…”

Ecomorphological correlates of inner and middle ear anatomy within phyllostomid bats

“…Several features of the inner and middle ear are believed to impact sound transmission, including the size, shape, and stiffness of the ossicular chain (Malkemper et al, 2020; Mason, 2013, 2016; Nummela, 1995) and the spirality of the cochlea (Manoussaki et al, 2008). Accordingly, the anatomical diversity of the auditory apparatus has been explored in numerous mammalian lineages, including rodents (Argyle & Mason, 2008; Farr & Mason, 2008; Mason, 2013; Wilkins et al, 1999), carnivorans (Gürbüz et al, 2019; Martonos et al, 2022; Wible & Spaulding, 2012) and xenarthrans (Sidorkewicj & Casanave, 2012). Ossicular morphology has also been explored in numerous extinct taxa with reference to their living relatives (e.g., Dickinson et al, 2022; Orliac & Billet, 2016; Stoessel et al, 2016).…”