Galaxioids

Williams, R. 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), pp. 139-166 : 154-155

Galaxioids (Retropinnidae + Prototroctidae + Lepidogalaxias + Galaxiidae + Aplochitonidae)

(1) Autopalatine small (shared with most Salmonidae , Dallia , and Umbra ). Primitively, it is somewhat large with expanded ends.

(2) Palatoquadrate cartilage at posterior end of autopalatine reduced or absent. Primitively it expands dorsally towards the lamina orbitonasalis.

(3) Ventral limb ofpreoperculum as long as, or longer than, dorsal limb (shared with Dallia , Salangidae , and Argentinoidea). Primitively, the dorsal limb is longer than the ventral limb.

Figure 13 presents the galaxioid relationships suggested by the data from the suspensorium and its muscles. The

(4) Supramaxillae and supramaxillary ligament absent (shared with adult Plecoglossus , some Salangidae , and Argentinoidea). Primitively in Teleostei there are two supramaxillae, and a supramaxillary ligament extends from the anterior tip of the posterior one to the lower jaw.

(5) Origin of adductor mandibulae includes most of lateral surface of preoperculum anterior to lateral sensory canal (shared with Esocoidei and Argentinoidea). Primitively, the adductor mandibulae originates only along the anterolateral edge of the preoperculum.

(6) Mandibular branch of trigeminal nerve passes medial to anterior end of section A2 of adductor mandibulae before running medial to lower jaw (shared with Argentinidae and Bathylagidae ). The assumption is that a reversal has occurred in Retropinna since it has the primitive state. Primitively, the nerve passes lateral to the anterior end of section A2 before running medial to the lower jaw (e.g., Figs 7 , 14). Most lower teleosts (e.g., Chanos , Clupea , Hiodon , Elops ) and primitive neoteleosts (e.g., Diplophos , Vinciguerria, Aulopus ) have this state. Although the nerve technically passes medial to the anterior end of section A 2 in Umbra limi and U. pygmaea this is related to a feature uniting them: the anterolateral fibres of section A2 converge onto a unique tendon (Fig. 15: L.A2) extending to the angulo-articular. The nerve rests lateral to the anterior end of section A2 at the division of sections A2 and Aw, as in all other esocoids, but is medial to the new tendon and the anterolateral fibres of section A2 that converge onto it. Hence it occupies the same relative position as the other esocoids and is the primitive state (compare Fig. 15 of U. limi with Fig. 16 of U. krameri , the sister species of U. limi + U. pygmaea ; Wilson & Veilleux, 1982).

Retropinnidae + Prototroctidae

(7) Ectopterygoid fused with palatine ( Fig. 13: 7A). Dallia questionably shares this state. It can be argued that in Dallia the ectopterygoid is lost, and the dermopalatine is greatly expanded posteriorly to nearly touch the anterodorsal corner of the quadrate (see also Wilson & Veilleux, 1982). However, even if the ectopterygoid and palatine are fused in Dallia , the socalled fused bone is unlike the one in the Retropinnidae and Prototroctidae because it is more robust, the teeth are larger and more numerous, and its posterior end does not overlap the quadrate. Primitively, palatine and ectopterygoid are separate. Galaxiidae and Aplochitonidae are united because they share an ectopterygoid that is greatly reduced or absent and largely or completely replaced by a prominent ligament ( Fig. 13: 7B).

(8) Lateral foramen for hyomandibular branch offacial nerve anterior to middle oflateral strut ofhyomandibular ( Fig. 13: 8A). A lateral foramen at the ventral end of the lateral strut unites Lepidogalaxias , Galaxiidae , and Aplochitonidae ( Fig. 13: 8B). A lateral strut is absent in Lovettia . Primitively, it is posterior to the dorsal half of the strut (see also Williams, 1987).

(9) Lateral strut of hyomandibular convex anteriorly as it arches posterodorsally from ventral to opercular arm ( Fig. 13: 9A). A robust, shelf-like lateral strut, somewhat similar to the above, unites Galaxiidae and Aplochitonidae ( Fig. 13: 9B). A lateral strut is absent in Lovettia . Primitively, the strut is concave anteriorly and inclined vertically between the ventral arm and the base of the head.

(10) Large cartilage at posterodorsal corner of metapterygoid. Primitively this cartilage is either small or lacking (usually).

(11) Symplectic prominently bent, with broad posterior expansion, and large anterior cartilaginous knob. Primitively it has a slight bend, a slightly expanded posterior end, and a small anterior cartilage.

(12) Adductor hyomandibulae (AH) present (shared with Esocidae , Dallia , some osmerids [ Spirinchus and Thaleichthys ], and most Alepocephaloidea). Primitively there is no AH (see also Winterbottom, 1974).

Figures

Fig. 7. Lateral view of external muscles of left suspensorimn in Retropinna retropinna (UAMZ 4606, 77.0 mm). On Figs 㝾ㄲⰠ 14~16, 18, and 19 muscles are indicated by closely spaced parallel lines; ligaments and tendons are short, closely spaced dashes; bones are outlined or stippled.

Fig. 16. Lateral view of external muscles of left suspensorium in Umbra krameri (UAMZ 3727, 63.3 mm).