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The mastoid pneumatization in Gerbillidae, lateral view, schematically. A – Taterillus, B–F – Gerbilliscus: B–E – G. (Taterona); F – G. (Gerbilliscus), Dipodillus, G – Tatera; H – Progerbillurus; I – Gerbillurus; J – Desmodillus; K – Ammodillus; L – Brachiones, Desmodilliscus, Gerbillus, Meriones, Psammomys, Rhombomys; M – Pachyuromys. etme – выпячивание спереди из эпитимпанального кармана; pmc – задняя мастоидная камера; pme – впячивание изнутри заднего канала; другие обозначения как на рис. 1–3. etme – epitympano-mastoid extension; pmc – posterior mastoid cell; pme – posterior mastoid extension; others as in Fig. 1–3.
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The structure of the mastoid in the gerbillid genera Gerbilliscus and Taterillus with an initial stage of its pneumatization is analyzed. A hypothesis is empirically confi rmed that development of additional cavities in the mastoid is accomplished by penetration of the tympanic cavity in it. It is substantiated that position of the hole through whi...
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Citations
... The ear capsule of Gerbillinae has been studied quite fully in both the functional and phylogenetic aspects (Lay, 1972;Pavlinov, 1980Pavlinov, , 2001Pavlinov, , 2008Pavlinov et al., 1990;Potapova, 2016). The ways and methods of its pneumatization have been found. ...
... Based on numerous studies of the ear capsule of rodents (hamsters, gerbils, dormice, squirrels, burrowers, etc.), it has been shown that the phylogenetic component in the structure of its diversity, as a rule, is most clearly manifested at the generic level and above. However, the analysis of interspecific and intraspecific mastoid diversity in gerbils of the genus Gerbilliscus, with the initial stage of its pneumatization, showed the suitability of such studies for assessing interspecific relationships and studying geographic variability (Potapova, 2016). The data received turned out to be important for understanding the morphogenesis of the auditory capsule of gerbils and made adjustments to the existing ideas about mastoid semophilesis in this group. ...
... As expected, the nature and parameters of intraspecific variability of the mastoid in the great gerbil are different than in Gerbilliscus gerbils with the initial stage of mastoid pneumatization (Potapova, 2016). Interspecific and intraspecific variability in Gerbilliscus manifests itself in signs that determine the types of pneumatization of the mastoid in gerbils in general. ...
Abstract—The peculiarity and diversity of pneumatization mechanisms of the ear capsule in Rhombomys are
described. Its peculiarity is manifested in (a) a slight swelling of the tube of the external auditory canal, (b) the
absence of a premeatal cell, (c) a significant development of the lower mastoid chamber, and (d) the appearance
of a special mastoid–tympanic pocket in response to a reverse expansion of the mastoid cavity into the
tympanic bulla. The conditions for the formation of this pocket are a significant rearward displacement of the
tympanic ring dome and the presence of a wide tympano-mastoid septum. The diversity of pneumatization
mechanisms of the ear capsule is expressed in different size ratios of the cavities located in the epitympanic,
mastoid, and tympanic parts of the capsule. This is due to the different sequence and different degree of swelling
in these parts. Features are distinguished that, in different combinations, cover the complete range of this
diversity. A way to describe them is proposed. A preliminary assessment of variations shows that gerbils from
different geographic localities differ both in the size characteristics of the ear capsule and in the qualitative
parameters of its pneumatization. These variations seem to reflect the ecological differentiation of this species
and its history.
Keywords: gerbils, middle ear, intraspecific variations
DOI: 10.1134/S1062359022080179
... Morphological characteristics of auditory bullae in Ammodillus are advanced too. In comparison with the generalised state of this structure typical for Taterillus and characterised by the absence of the mastoid cavity (Pavlinov, 2008), mastoids of A. imbellis are completely pneumatised and possess some features that allow investigators to designate Ammodillus as one of branches of the initial radiation of gerbilline taxa (Potapova, 2016). Consequently, despite retaining several plesiomorphies, Ammodillus morphology is advanced rather than primitive and shows mostly an automorphic state. ...
Gerbillinae is the second largest subfamily (after Murinae) in the Muridae family comprising ~16 genera and more than a hundred species. Phylogenetic relationships among the main taxa of gerbils are still not fully understood. In particular, a major issue is the phylogenetic position of the monotypic genus Ammodillus (endemic to the Horn of Africa), which according to morphological data may be one of the earliest offshoots from the gerbilline stem; however, its precise affiliations have been unknown due to the lack of genetic data. Here, by means of a multilocus dataset including one mitochondrial and five nuclear markers, we for the first time elucidated phylogenetic placement of Ammodillus and provided the most complete tribal phylogeny of Gerbillinae to date. Phylogenetic reconstructions robustly supported Ammodillus as a sister taxon to all other living gerbillines and suggested that the separation of the ammodile lineage dates back to the Middle/Late Miocene boundary (~11.7 Mya). The results are consiste nt with subdivision of the subfamily into four tribes: monotypic Ammodillini, Gerbillini (including Taterillus), Desmodilliscini (including Pachyuromys) and Gerbillurini. In the light of the new data, we discuss possible scenarios of Gerbillinae origin, highlight Ammodillus as a relatively ancient—albeit morphologically advanced—lineage that has never gained diversity and propose the term ‘ancient singleton’ for a taxon with a persistently low diversification rate.
... Among the rodents, the diversity of the auditory capsule has been most fully studied in representatives of Gerbillidae (Lay, 1972;Pavlinov, 1980Pavlinov, , 2008Pavlinov et al., 1990;Potapova, 2016), Muroidea (Lange et al., 2004;Potapova, 2005;Mason, 2012), Dipodoidea (Potapova, 1998), Heteromyidae (Webster, 1966(Webster, , 1975Webster, M., 1975, 1980), Gliroidea (Wahlert et al., 1993;Potapova, 2001Potapova, , 2007Rossolimo et al., 2001;Farr and Mason, 2008), and Ctenochystrica (Schleich and Busch, 2004;Mason, 2004;Mason et al., 2016;etc.). A large number of works have been carried out on fossorial rodents (Mason, 2001;Potapova and Vorontsov, 2004;Argyle and Mason, 2008;Mason et al., 2010;and many others). ...
Abstract—Specific features of the sciurid auditory capsule have been analyzed based on 63 species from
20 genera. Its morphological specificity is characterized by a peculiar combination of primitive and advanced
features stable within the group. They are (1) a rounded and inflated bulla with internal septa and a primitive
attachment of the tympanic ring to the inner tympanic wall; (2) a transverse position of the bulla relative to
the axis of the promontorium, resulting in the presence of deep petrosal fossae in front of and above the promontorium
which are not covered by the tympanic bone; (3) a fully formed osseus facial canal and a developed
bone tube of the stapedial artery; (4) the presence of a meato-cochlear bridge connecting the promontorium
to the posterior wall of the acoustic duct which, in a fully developed form, does not occur in any other recent
rodents; (5) pneumatization of the mastoid due to the expanding of the epitympanic chamber both anteriorly
and posteriorly, with the formation of a premeatal pocket and a large epitympano-mastoid chamber divided
into parts. The sciurid auditory capsule can generally be considered as morphologically advanced. Its diversity
within the family concerns functionally significant features and is manifested in the structure of the external
acoustic meatus, the size of the tympanic membrane, the length of the processes of auditory ossicles, and,
most importantly, the degree of pneumatization of the auditory capsule. This is associated with quantitative
variations of the characters and does not affect its structural plan, as a rule.
Keywords: sciurid, Sciuridae, morphological specificity, auditory capsule, middle ear
DOI: 10.1134/S1062359019070094
