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The phylogenetic position of the south-western Australian endemic, Lepidogalaxias salamandroides, has been controversial since its description by Mees in 1961. Some workers place this tiny fish with the galaxioids of the southern end of the Southern Hemisphere, one considered it to be an esocoid (a group otherwise restricted to the northern end of the Northern Hemisphere), while another hypothesises that it may be the sister group of the Neoteleostei. My study of the suspensorium and its muscles in associated euteleosts supports the hypothesis that the galaxioids are monophyletic and include Lepidogalaxias. Data from the bones and muscles of the suspensorium suggests the following pattern: ([Retropinnidae + Prototroctidae] + [Lepidogalaxias + (Galaxiidae + Aplochitonidae)]). Lepidogalaxias is the sister group of Galaxiidae + Aplochitonidae based particularly on synapomorphies of the adductor mandibulae. The suspensorium and its muscles in Lepidogalaxias and the other galaxioids are described in detail for the first time. I also critically evaluate competing hypotheses of galaxioid relationships and comment on paedomorphosis in the group. WILLIAMS, ROBERT R.G., 1997. Bones and muscles of the suspensorium in the galaxioids and Lepidogalaxias salamandroides (Teleostei: Osmeriformes) and their phylogenetic significance. Records of the Australian Museum 49(2): 139-166. The salmoniform fishes endemic to the Southern Hemisphere, the galaxioids, include the Retropinnidae, Prototroctidae, Galaxiidae, and Aplochitonidae (all sensu McDowall, 1969). Although the familial arrangement may vary, except for Rosen (1974) most recent workers consider the galaxioids to be monophyletic (e.g., McDowall, 1969, 1984; Nelson, 1972; Fink, 1984; Howes & Sanford, 1987; Williams, 1987; Begle, 1991; Nelson, 1994). In contrast, Rosen (1974) linked the Galaxiidae + Aplochitonidae (his Galaxiidae) with the Salmonidae, and the Retropinnidae + Prototroctidae (his Retropinnidae) with the Osmeridae + Plecoglossidae + Salangidae. Although most agree that the galaxioids are monophyletic, the phylogenetic position of the tiny galaxioid-like south-western Australian endemic, Lepidogalaxias salamandroides, is controversial. When Mees (1961) first described this highly unusual fish he 140 Records of the Australian Museum (1997) Vol. 49 placed it in its own genus within the Galaxiidae, but suggested that it might occupy a separate subfamily. Scott (1966) reviewed the features of Lepidogalaxias and compared them to the Galaxiidae. He tentatively left it in the Galaxiidae but suggested that it may belong in a new family. McDowall (1969), in a review of Southern Hemisphere salmoniforms stated that it was not a galaxiid. Frankenberg (1969) described the osteology and some soft anatomy of Lepidogalaxias. Although he noted that it shared several morphological similarities with the esocoids of the Northern Hemisphere, he concluded that the overall evidence favoured a galaxiid relationship. He placed it in its own family, Lepidogalaxiidae, and suggested dividing Galaxioidei (of Greenwood et al., 1966) into two superfamilies, one to contain Lepidogalaxias (Lepidogalaxioidea), and the other the remaining galaxioids (Galaxioidea). In a study of cephalic sensory canals and pit lines Nelson (1972: 38) concluded that "The relationships of Lepidogalaxias remain obscure" but noted that it shared similarities with both the Galaxiidae and Aplochitonidae (sensu McDowall, 1969) and the esocoid Dallia. Rosen (1973) placed the Lepidogalaxiidae in the suborder Salmonoidei of the order Salmoniformes, but did not discuss its relationship to the other salmonoids (Salmonidae, Galaxiidae, Aplochitonidae, Retropinnidae, Salangidae, Osmeridae, and Plecoglossidae). In a radical departure, Rosen (1974) presented evidence that Lepidogalaxias was an esocoid, and placed it in the Esocoidei as a separate superfamily, Lepidogalaxioidea, along with the Esocoidea (Esocidae + Umbridae). The Esocoidea are restricted to the northern part of the Northern Hemisphere. Fink & Weitzman (1982) were not convinced that Lepidogalaxias was an esocoid and recommended further study. Roberts (1984) hypothesised that Lepidogalaxias might be a highly specialised galaxiid or galaxioid derivative. Emphasising its uniqueness and uncertain phylogenetic position, in 1984 Nelson placed Lepidogalaxias in its own suborder, the Lepidogalaxioidei, within the order Salmoniformes (with the Esocoidei, Argentinoidei, and Salmonoidei). McDowall & Pusey (1983) provided a new description of Lepidogalaxias, briefly reviewed the controversy, but provided no new evidence concerning its relationships. Fink (1984) was also unconvinced of Rosen's (1974) hypothesis that Lepidogalaxias is an esocoid, and using new characters, placed it, the Salmonidae, and the Neoteleostei in an unresolved trichotomy. He noted, however, that (p. 205) "more work remains to be done before we can be really confident in [its] phylogenetic placement." Apparently because of the uncertainty, Rosen (1985) excluded Lepidogalaxias from his cladogram of clupeocephalan relationships, and stated only that evidence supporting either a neoteleost, galaxiid or esocoid relationship was available. More recently, Begle (199l) presented a cladistic analysis of the lower euteleosts. He hypothesised that Lepidogalaxias is the sister group of a clade made up of (Salangidae + [Lovettia + (Aplochiton + Galaxiidae)]) and that Retropinnidae + Prototroctidae is the sister group of these five taxa. In Nelson's (1994) current classification Lepidogalaxias is placed in its own family, Lepidogalaxiidae, within superfamily Galaxioidea of the suborder Osmeroidei (with superfamily Osmeroidea) within the order Osmeriformes (with suborder Argentinoidei). Most recently, Johnson & Patters on (1995, 1996) hypothesise that Aplochiton and Galaxiidae are sister taxa, that Lovettia and Lepidogalaxias are sister taxa, and that the sister group of these two clades is the Retropinnidae (Retropinna + Stokellia + Pro to troctes ). I examined the galaxioids and Lepidogalaxias as part of a comprehensive study of the suspensorium and its muscles in the salmoniforms and their relatives (Williams, 1987). This study yielded considerable new osteological and myological information. Some of this information constitutes evidence bearing on galaxioid intrarelationships and the phylogenetic position of Lepidogalaxias. In the present paper I describe in detail the suspensorium and its muscles in the galaxioids and Lepidogalaxias, and discuss the phylogenetic relationships that are suggested by the new data on bones and muscles of the suspensorium. The suggested phylogeny should not be considered definitive since it is based on data from a single character complex. Evidence from other anatomical systems as well as from other sources such as molecular sequences will have to be considered before a definitive hypothesis emerges. Nevertheless, the suspensorium provides critical new information potentially helpful for solving the riddle of galaxioid relationships. Materials and methods Specimens were cleared and stained for cartilage and bone using Taylor & Van Dyke's (1985) method. Radiographs of some fish were taken using a "Torrex 150 Radiographic-Fluoroscopic System." Dissections and drawings were made using a Wild M7 A stereomicroscope equipped with a camera lucida. The standard length of each specimen was measured with Helios needle-pointed dial callipers. Osteological nomenclature follows Norden (1961) and Harder (1975). Muscle nomenclature follows Winterbottom (1974). The term tendon is frequently synonymised with ligament, not because they are difficult to distinguish, but because they are often homologous. The term endochondral refers to an ossification having a cartilaginous precursor. On cleared and stained specimens this is seen as a thickened bone (red) with a cartilaginous (blue) core. A dermal ossification does not arise from cartilage and is stained only red. The palatine has an endochondral component (the autopalatine) and a dermal component (the dermopalatine). The metapterygoid, quadrate, symplectic, and hyomandibular are endochondral but can have membranous laminae that are stained only red. The ectopterygoid, mesopterygoid, and preoperculum are dermal bones. Unless noted, in the following text I use the name Salmoniformes in its traditional way (sensu Nelson, 1984) because of the prevalent usage of this name in the literature, and because the relationships of its members are still controversial. In Nelson's (1994) new classification Salmoniformes refers only to the family Salmonidae. Otherwise names of taxa follow Nelson 1994 except that: Esocoidei = Esocidae + Umbridae; Salangidae = Salangidae + Sundasalangidae; osmeroids = Osmeridae (Hypomesus + Mallotus + Allosmerus + Osmerus + Spirinchus + Thaleichthys + Plecoglossus) + Salangidae; and Retropinnidae (Retropinna + Stokellia) , Prototroctidae (Pro to troctes) , Galaxiidae, and Aplochitonidae (Aplochiton + Lovettia) are each sensu McDowall (1969). Contrary to Nelson (1994) I do not use the term Esociformes (= my Escoidei) nor Osmeriformes (= Argentinoidei + my osmeroids + my galaxioids which include Lepidogalaxias). I evaluated galaxioid intrarelationships as part of a larger study involving all Salmoniformes (Williams, 1987). The cladistic relationships of galaxioids were studied using evidence from the bones and muscles of the suspensorium. Characters were selected, their states were documented, and outgroup analysis was used to decide polarity. The traditional galaxioids (Retropinnidae + Prototroctidae + Galaxiidae + Aplochitonidae, all sensu McDowall, 1969) + Lepidogalaxias were considered to be the ingroup. Monophyly is supported by Williams (1987), Begle (1991), and Iohnson & Patterson (1995, 1996). The monophyly of the galaxioids excluding Lepidogalaxias is supported by numerous earlier workers (e.g., McDowall, 1969, 1984; Nelson, 197

records of the australian museum

Bones and muscles of the suspensorium in the galaxioids and Lepidogalaxias salamandroides (Teleostei: Osmeriformes) and their phylogenetic significance