Sabella acrophthalmos Grube, 1878 Megalomma acrophthalmos Knight-Jones, 1997: 316 Review of the Genus Megalomma (Polychaeta: Sabellidae) in Australia with Description of Three New Species, New Records and Notes on Certain Features with Phylogenetic Implications Capa, María Murray, Anna Records of the Australian Museum 2009 2009-11-25 61 2 201 224 (Grube, 1878) Grube 1878 [822,1392,1684,1710] Insecta Carabidae Megalomma Animalia Coleoptera 7 208 Arthropoda species acrophthalmos   Figs 4C–D, 5B, 6     Sabella acrophthalmos Grube, 1878: page 258, 259.   Megalomma acrophthalmos Knight-Jones, 1997: 316fig. 2.   Material examined.   Western Australia. AMW35477, ( 1 spec.), Stn WA621, north west of West Lewis Island, Dampier Archipelago, 20°33'31"S 116°38'13"E, intertidal, coll. P.Hutchings,  26 Jul.2000.  MAGNTW14008, Roebuck Bay, Broome, 19°04'00"S 122°16'59"E, coll.  R. J. Hanleyand M. Jebb,  29 Aug. 1991( 1 spec.on SEM stub, AM 499).  Figure 4. Drawings to scale of thoracic and abdominal uncini.  Megalomma phyllisae n.sp.: ( A) thoracic uncinus; ( B) abdominal uncinus.  Megalommacf. acrophthalmos: ( C) thoracic uncinus; ( D) abdominal uncinus.  Megalomma interrupta n.sp.: ( E) thoracic uncinus; ( F) abdominal uncinus.  Megalomma inflata n.sp.: ( G) thoracic uncinus; ( H) abdominal uncinus.   Megalommasp. 1: ( I) thoracic uncinus; ( J) abdominal uncinus.  Megalomma suspiciens: ( K) thoracic uncinus; ( L) abdominal uncinus. Scale: 0.1 mm.   Description. Largest specimen AM W35477, 30 mm long, 4 mmwide with eight thoracic and 108 abdominal chaetigers (smallest has eight thoracic and 53 abdominal chaetigers). Crown longer than thorax, 9 mmlong, with 25 pairs radioles (15 pairs in the small specimen). Outer surface of radioles quadrangular at the base ( Fig. 6B) and rounded distally, with tips shorter than pinnules. Radiolar skeleton composed of 15–20 cells in transverse section ( Fig. 5B). Most radioles with subdistal eyes, dorsalmost four pairs appear spiral, and lateral ones large and becoming smaller more ventrally, lacking or missing in 1–2 pairs ventralmost radioles. Dorsal lips with radiolar appendages as long as two thoracic chaetigers, pinnular appendages absent. Caruncle absent. Low smooth keel (thickened and non-lamellate) projecting ventrally between dorsal lips, arising from raised triangular mound situated mid dorsal to dorsal lips. Ventral lips rounded and well developed; ventral parallel lamellae and sacs present. Posterior peristomial collar fused mediodorsally to the faecal groove; dorsal lappets present, elongate and spatulate-shaped distally, as long as lateral collar margins, and with dorsolateral U-shaped indentations on both sides forming pockets, reaching to level of second chaetiger ( Fig. 6A); lateral collar margins smooth ( Fig. 6B), and ventrally forming overlapping lappets with rounded anterior margins, with a complete midventral incision ( Fig. 6C). Ventral shields rectangular, all separate from the neuropodial tori ( Fig. 6C), all similar in width. First ventral shield longer than the rest, with m-shaped anterior margin. First chaetiger with superior and inferior elongate narrowly hooded notochaetae; superior longer than inferior ( Fig. 6D). Rest of thoracic chaetigers with two rows of superior elongate narrowly hooded and two rows of inferior broadly hooded notochaetae with progressively tapering tips ( typeB) ( Fig. 6E); lamella-like lobe present between superior and inferior notochaetal fascicles. Uncini with around 7–10 rows of small, similarly sized teeth above main fang ( Fig. 6F,G), well developed breast, handle long, three times the length of the distance from breast to main fang ( Fig. 4C). Companion chaetae with asymmetrical membrane ( Fig. 6H). Abdominal neuropodia with slender broadly hooded chaetae ( Fig. 6I). Abdominal uncini similar to thoracic uncini, with similarly-sized teeth over the main fang but covering more surface area ( Fig. 6J) and with shorter handle ( Fig. 4D). Pygidium with four small lobes, scattered eyespots laterally.  Colour pattern. Three regular transverse pigment bands on branchial radioles plus other less regular pigment on pinnules distally. Brown pigment present on anterior dorsum of body and with dark regular patches dorsolaterally on anterior margins of first seven thoracic segments.   Remarks. Of the species recorded in the Indo-Pacific, these described specimens most closely resemble  M. multioculatumand  M. phyllisae n.sp.in the presence of subdistal eyes on most radioles and with dorsal margins of collar fused to the faecal groove. However,  M. cf. acrophthalmoshas conspicuous elongated dorsal collar lappets which are absent in  M. multioculatumand  M. phyllisae n.sp.These three features (pattern of distribution of radiolar eyes, fusion and shape of collar dorsal margins), are shared with the type material described from the Philippines( Grube 1878) and restudied and drawn by Knight-Jones (1997). The chaetae and uncini of specimens from both localities also show similarities: the inferior thoracic chaetae are broadly hooded but with a progressively-tapering hood (type B) and the thoracic uncini have long handles, exceeding twice the distance of main fang to breast. The only specimen available from the type locality (most probably the holotypeaccording to Knight-Jones [1997]) is not in good condition. Because of this reason, identification should be confirmed with additional material from the type locality. However, it is quite possible that the species has a southeast Asian distribution. This species has also been recorded in Sri Lanka( Willey, 1905) as  Branchiomma acrophthalmosbut this identification has not been confirmed. Other species in the genus described as possessing well developed dorsal lappets are  M. fauchaldi( Giangrande et al., 2007)from Belize,  M. vesiculosumfrom England, and  M. mushaenseand  M. nechamaefrom the Red Sea, all of which also possess radiolar eyes on most radioles, collar fused to the faecal groove and pockets present, although this last feature was not interpreted as such by Knight- Jones (1997). The shape and size of the lappets and the margin of the collar of  M. acrophthalmosare all different in shape and size to these four species, and their geographical distributions are discrete and separated widely enough to also separate them as different species. W35477 2000-07-26 AM Stn WA & Dampier Archipelago & P. Hutchings -20.55861 West Lewis Island 21 116.63694 7 208 1 Western Australia W14008 MAGNT -19.066668 Broome 21 122.28306 Roebuck Bay 7 208 1 Western Australia 1991-08-29 R J. Hanley & M. Jebb 7 208 AM 499 1 Western Australia