The middle ear of the skull of birds: the ostrich, Struthio camelus L.

Avian heads are characterized as having two extensive air‐filled systems lined with epithelia; the paranasal and paratympanic sinuses. Many diverticula derived from the paratympanic sinus system are known to reticulate with each other to form a single merged pneumatic space within the adult braincase. However, the development of these complex branching and reticulating epithelia has not been examined in detail. In this study, we describe the comprehensive developmental pattern of the paratympanic sinus and its associated soft tissues in a model bird, Japanese quail (Coturnix japonica). The data are derived from three‐dimensional reconstructions based on histological sections and soft tissue enhanced micro‐CT data. Those data provide the foundation of the complex hierarchical developmental pattern of the paratympanic sinus system. Moreover, associations with other tissues help establish key morphologies that identify each pneumatic entity. This study clarifies the developmental relationships of the ventral portions of the paratympanic sinus system, the siphoneal diverticulum and marginal sinus, based on the ligaments associated with the Eustachian tube. In addition, detailed histological pneumatic morphologies reveal hitherto unknown epithelial diversity, which may be indicative of equally complex developmental processes. We use the pneumatization of the quadrate as an example to support a close relationship with vascular growth and pneumatic epithelia invasion into ossified bone. We confirm pneumatic diverticula never enter into cartilages, possibly due to the absence of vasculature in these tissues. Lastly, we use the concept of a morphogenetic tree as a tool to help present the complex developmental pattern of the paratympanic sinus system and apply it toward inferring pneumatic morphologies in a nonavian theropod braincase.

mentioning

confidence: 99%

Development of the paratympanic pneumatic system of Japanese quail

Tahara

Larsson

2019

“…Macke (1969) focused on the development of the skull of the coot (Fulica atra) and gave only minor attention to the middle ear structures. Saiff (1981Saiff ( -1988 and most recently J.M. Starck (1995) presented specialized investigations in the paleognathous middle ear.…”

mentioning

confidence: 99%

Anatomy of the middle ear of the japanese crane Grus japonensis (gruidae: Aves)

Vörster

Starck

2003

Comparative anatomical studies of the avian middle ear provide structural data from which functional models can be derived. Subsequent phylogenetic analyses may reveal the phylogenetic history of taxon and the evolution of the functional model of the middle ear. We studied serial sections of a nestling of Grus japonensis. The microscopic anatomy of the middle ear (including skeletal parts, nerves, blood vessels, tendons, and tympanic recesses) was described with the help of a polystyrene plate reconstruction. These results were compared to those from skulls of adult cranes. Structural peculiarities of the crane middle ear are: 1) the ventral and anterior closure of the middle ear cavity by a dense plate of connective tissue, which ossifies during posthatching development; 2) the S-shaped infracolumellar process of the columella, of which the distal end forms a horizontal bar, and abuts against the ventral wall of the middle ear cavity; and 3) the absence of an intracolumellar hinge between the stapes and extracolumella. The crane middle ear shows the plesiomorphic pattern of middle ear structures of neognathous birds. We propose a one-lever-arm functional model for the middle ear of the crane, similar to that of paleognathous birds.

“…Nervus vagus and n. glossopharyngeus “are very closely related both topographically and functionally” (Akester, , p. 398), and in palaeognathous birds both nerves exit through a single foramen (Bourdon & Lindow, ; Elzanowski, ; Müller, ; Saiff, ). In most Neognathae, by contrast, there is a separate foramen for nervus glossopharyngeus, which is usually situated at the medial margin of the fossa parabasalis (Figure ).…”

Section: Introductionmentioning

confidence: 99%

“…Although detailed studies of the course of the cranial nerves were published for some galloanserines (Akester, 1979;Gheţie, 1976, fig. 325), Psittaciformes (Manogue & Nottebohm, 1982;Wild, 1981), Passeriformes (Conrad, 1915;Nottebohm & Nottebohm, 1976), as well as some Podicipediformes and Rallidae (Conrad, 1915), descriptions of the basicranial nerve foramina are sparse and scattered in the literature (e.g., Elzanowski & Galton, 1991;Saiff, 1974Saiff, , 1978Saiff, , 1981Saiff, , 1988Weber, 1990). Most previous authors described 2-3 foramina nervi hypoglossi (FNH) for neornithine birds, but as shown in the present study, there exists more variability in the number, size, and arrangement of these foramina than what is apparent from the literature.…”

mentioning

confidence: 99%

Size and number of the hypoglossal nerve foramina in the avian skull and their potential neuroanatomical significance

Mayr

2017

The cranial openings of nervus hypoglossus, the 12th cranial nerve, are for the first time studied across a broad range of higher avian taxa. This nerve plays an important role in the innervation of the syrinx and exits the skull through a variable number of foramina. Most previous authors described 2-3 foramina nervi hypoglossi (FNH) for neornithine birds, but the number, size, and arrangement of FNH is actually more variable than what is apparent from the literature. In the case of three foramina, there is usually a pair of caudal foramina and a rostral one, but even in closely related taxa, a great variability of the FNH pattern may exist. Many taxa of Neognathae exhibit a quadruple of symmetrically arranged FNH, in others four foramina are strung together in a line. A few taxa show more than four FNH, although in these cases the additional foramina are very small. Of particular interest is the occurrence of a very large caudal FNH in Trochilidae and many species of Passeriformes. This large foramen is suggestive of a correlation with the highly developed vocal capabilities of these birds and may transmit fibers from the tracheosyringeal portion of nucleus nervi hypoglossi, in which case it would be an osteological correlate of vocal capabilities. However, targeted neuroanatomical studies are required to determine how individual hypoglossal foramina relate to hypoglossal roots and their branches, and which of them receive fibers supplying axial, lingual, and syringeal muscles.