SEPTEMBER, 1982 17 REMARKS ON THE TYMPANIC CAVITY OF MALURUS, STIPITURUS AND AMYTORNIS (PASSERIFORMES, MALURIDAE) s. A. PARKER INTRODUCTION THE AVIAN TYMPANIC CAVITY Mayr & Amadon (1951) and Keast (1961) In mammals, the tympanic cavity or middle recognized the subfamily Malurinae for a group ear is usually more or less entirely enclosed by of Australasian wren- and warbler-like genera, bone to form the auditory bulla (see for instance including Malurus, Stipiturus, Todopsis, Cheno­ Novacek 1977). In birds, however, it is usually rhamphus, Clytomyias, Dasyornis, Amytornis, merely a shallow concavity in the skull, bounded Aphelocephala, Sericornis, Acanthiza and Gery­ posteriorly by the ala tympanica (tympanic gone. Harrison & Parker (1965), chiefly on wing), a lateral flaring of the os exoccipitale, behavioural evidence, restricted the subfamily and ventrally by a much smaller extension of to include only the first five genera and the the os parasphenoidale also termed the ala Fijian genus Lamprolia, and used the term tympanica (Baumel 1979: 82, 88). In the skull Acanthizinae to cover the remainder. Subse­ of the Common or American Crow Corvus quently, Harrison (1969) redefined the Malur­ brachyrhynchos (Baumel 1979: 109) and in the inae sensu stricto, including Amytornis and ex­ skulls of all five Australian species of Corvus cluding Lamprolia (which latter may actually (including the Little Crow C. bennetti, fig. 4b), be a monarchine flycatcher fide Olson 1980). the exoccipital tympanic wing is not well­ Schodde (1975) raised the Malurinae of developed, providing little more than a posterior Harrison to the rank of family, the Maluridae, wall to a' quite open tympanic cavity. In the a move that emphasizes the uncertainty concern­ skulls of other Australian passerines examined ing the group's taxonomic relationships. by me (including- Black-faced Cuckoo-shri~e Coracina nouaehollandiae, Southern Scrub-robin A character discovered by Harrison (1969) Drymodes brunneopygia, Cinnamon Quail­ in 'the Maluridae, and used by him in his re­ thrush Cinclosoma cinnamomeum (fig. 3a), definition of the group, ~s the gap in the inter­ Chestnut-crowned Babbler Pomatostomus rufi­ scapular zone of the spinal feather tract. In the ceps, Grey Shrike-thrush Coll1;lricin~la ~ar­ present paper, I draw attention to a second monica, Restless Flycatcher Myzagra znqul~ta, unusual feature, the previously unremark.ed Willie Wagtail Rhipidura leucophrys, Whlte­ incapsulation of the cavitas tympa/!zca mid~le browed Scrubwren Sericornis frontalis (fig. 3b), (tympanic cavity or ear). I.first noticed Shy Hylacola S. cautus (fig. 3c), White-throated this ieature in 1967, while preparmg as study Treecreeper Cormobates leuqophaea1 (fig. ~a) skins specimens of the Dusky Grasswren Amy­ and Singing Honeyeater Lichenostomus tnre­ tornis purnelli and Striated Grasswren A. scens) the tympanic wing is produce~ forwards striatus. In 1971 I noted it similarly in the Grey to enclose in varying but relatively slight degree Grasswren A. barbatus, in 1973 in the Thick­ the posterior and postero-ventral regions of the billed Grasswren A. textilis, and in 1976 in the tympanic cavity, . Eyrean Grasswren A. goyderi. In 1969 and 1970 while examining collections of mammals In the skulls of the Maluridae, however, the during the compilation of a checklist of the relative volume of the tympanic cavity is in­ mammals of the Northern Territory (Parker creased, less by any greater forward ~roduction 1973) I noticed that certain desert-living forms, of the tympanic wings than by extension of the e.g. L~goTchestes and B:ettongia spp., possessed cavity backwards, downwards and outwa:ds, considerably larger auditory bulla~ .than forms manifest as a bulla-like bulging of the postenor, inhabiting moister country. Enquiring of col­ postero-ventral and lateral walls. In the Superb leagues in mammal~gy, ~ learnt th.at a corre­ Fairy-wren Malurus cyan~us (fig. la) the bu~la­ lation between relative SIze of auditory bullae like effect is slight, increasing through the White­ win <Ted Fairy-wren M. leuco pterus (fig. 1b) , and aridity of habitat was well known and Sou~hern documented (e.g. Webster & Webster 1975, Emu-wren Stipiturus malach.urus (fig. Archer 1981). Below, I present some obser­ lc), Striated Grasswren Amytornis striatus (fig. vations from a preliminary study of this feature 2a) and Grey Grasswren A. barbatus (fig. 2b) in the Maluridae (grasswrens, emu-wrens and to an extreme development in the Thick-billed fairy-wrens), with reference to its occurrence Grasswren A. textilis (fig. 2c). and interpretation in mammals. 1 Removed from the genus Climacteris by Parker (1982) 18 SOUTH AUSTRALIAN ORNITHOLOGIST, 29 a (:l.t. b c FIGURE 1. Views of skull showing tympanic region (left, lateral, right, ventral, a.t. ala tym­ panica). (a) Malurus cyaneus, (b) M. leucopterus, (c) Stipiturus malachurus. SEPTEMBER, 1982 19 a 2 a.t. b c FIGURE 2. (Key as in Figure 1). (a) Amytornis striatus, (b) A. barbatus, (c) A. textilis. 20 SOUTH AUSTRALIAN ORNITHOLOGIST, 29 b c FIGURE 3. (Key as in Figure 1). (a) Cinclosoma ctnnamomeum, (b) Sericornis frontalis, (c) Sericornis cauius, SEPTEMBER, 1982 21 a 4 a.t. FIGURE 4. (Key as in Figure 1). (a) Cormobates leucophaea, (b) Corvus bennetti. DISCUSSION churus, of dense, usually wet, herbage and From the literature (e.g. Webster & Webster thickets, shows a degree of development in this 1975, Archer 1981) it seems that in terrestrial feature greater than that in Malurus leucop­ mammals there is, with some exceptions, a cor­ terus, relation between increasing relative size of As to why many desert animals show relatively auditory bullae and increasing aridity of habitat. enlarged auditory bullae, there is evidence Irom In the evidence presented here from Amytornis, mammals that larger bullae enhance sensitivity Stipiturus, Malurus, Cinclosoma and other Aust­ to low-frequency sounds such as those produced ralian songbirds there is likewise conformity and by the attack-flight of owls and the strike of exception to this trend. Amytornis, the species snakes; the selection pressure for such sensitivity of which are largely terrestrial, is one of the most to evolve would he particularly great for animals aridicolous of the Australian passerine genera living in areas with very little cover, where (Keast 1958, 1961, Parker et al. 1978). Simi­ sparse vegetation would both increase the need larly, M alurus leucopterus is also largely a to forage and decrease the protection (Webster species of the arid zone, whereas M. cyaneus & Webster 1975, Archer 1981 and references inhabits dense thickets in moister areas. Yet therein). Predators exerting such influences on Cinclosoma cinnamomeum, a terrestrial bird of the diurnal grasswrens might well include fal­ sparsely vegetated stony plains and sandhill cons, hawks, owls hunting at twilight, and large desert, shows a relatively slight development of snakes (of which last I have, while searching the tympanic wings, whereas Stipiturus mala- for nests of the Eyrean Grasswren in Sandhill 22 SOUTH AUSTRALIAN ORNITHOLOGIST, 29 Keast, J. A. 1958. Speciation in the genus Amytornis Canegrass Zygochloa paradoxa) encountered Stejneger (Passeres: Muscicapidae, Malurinae) in Aust­ several examples concealed well up within the ralia. Aust, J. Zool. 6: 33-52. 1961. Bird speciation on the Australian con­ tall dense tussocks). tinent. Bull, Mus. comp, Zool, 12'3: 305-495. ACKNOWLEDGEMENTS Mayr. E. and D. Amadon. 1951. A classification of recent For help in the preparation of this article I am indebted birds. Amer. Mus. Novit. 1496: 1-42. to the following: my col league Jenni Thurmer, who drew Novacek, M. J. 1977. Aspects of the problem of variation, the figores of skulls, Dr Patricia Vickers Rich of Monash origin and evolution of the eutherian auditory bulla. University. who assisted me with the nomenclature of {the Mammal Rev. 7 (3-4): 131-149. avian skull, and Dr Michael Archer of the University of Olson, S. L. 1980. Lamprolia as part of a South Pacific New South Wales and my' colleague Mr Peter Aitken, who radiation of monarchine flycatchers. Notomis 27: 7-10. introduced me to the literature on mammalian auditory bullae. Parker, S. A. 1973. An annotated checklist of the native REFERENCES land mammals of the Northern Territory. Rec, S. Aust. Archer, M. 1981. Results of the Archbold Expeditions, 104. Mus. 16 (11): I-57 Systematic revision of the marsuplal dasyurid genus ------ 1982. The relationships of the Australo-Papuan Sminthopsis Thomas. Bull, Amer, Mus. nat. Hiat, 168 (2): treecreeners and sintellaa. S. Aust. Om. 28: 197-200. 63-223. ------, I. A. May and W. Head. 1978. Some obser­ Baumel, J. J. (00.) 1979. Nomina Anatomlca Avium, Acad­ vations on the Eyrean Grasswren Amytornis goyderi emic Press: London, New York. (Gould, 1:875). Rec. S. Aust. Mus. 17 (2:4): 361-371. Harrison, C. J. O. 1969. The affinities of [the blue wren genus Malurus and related genera: with special reference Schodde, R. 1975. Interim List of Australian Songbirds. to the grass-wren genus Amvtornis, Emu 69: 1-8. Pasaerines. Melbourne: RAOU. Harrison, C. J. O. and S. A. -Parker, 1965. The behavioural Webster, D. B. and M. Wehster. 1975. Auditory systems of affinities of the blue wrens of the genus Malurus. Emu Heteromvidaet functional morphology and evolution of 65: 103-113 the inner ear. J. Morphol. 146: 343c376. S. A. Parker) South Australian Museum) Adelaide) South Australia) 5000. Accepted 6 August, 1982..