Common Name
Gill's Whalefish
Year Described
Goode & Bean, 1895
Identification
Dorsal Fin: 16-19
Anal Fin: 16-19
Pectoral Fin: 16-21
Lateral Line Pores: 17-19
Gill Arches: 3.5
Genus diagnosis after Paxton (1989) for females:
Upper jaw length 32% SL. Predorsal Length 77% SL. Body rather elongated with a huge mouth (third of body length). Snout rounded. Eye tiny. Nasal organ small. Jaws slightly concave. Free gill arches number three with a short slit behind the fourth. Gill tooth plates contiguous. Lateral line conspicuous with large round pores inside a channel with raised rim. No vertical rows of papillae on lateral line. Dermal flaps absent to moderate. Lateral line system continues onto head as a series of pores and sensory openings. Additional pores on lower jaw and snout. Jaw teeth tiny in several irregular, diagonal rows. Vomerine tooth patch round or oval. Dorsal and anal fins located far back on body, with bases slightly elevated. Cavernous tissue located around the anus and the anterior anal fin base to ray 11. None around dorsal fin or caudal peduncle. Caudal fin with less than 17 principle rays. Pelvic fin absent. Pectoral fin small and inserted low on body. Body flabby and scaleless except for large, diagnostic scales associated with the lateral line canals.
Males and juveniles unknown.
Color
Preserved specimens are uniformly dark brown.
Size
Ranges from 80-140mm SL, with the majority under 90mm SL.
Habitat
Adults common under 1000m at bathypelagic depth. Small adults found in shallower water.
Range
The most commonly encountered genus member: found off the northeastern U.S. (Moore et al., 2003), off Bermuda (Harry, 1952), the Gulf of Mexico (McEachran & Fechhelm, 1998), and off Uruguay.
References
Harry, R.R. 1952. Deep-sea fishes of the Bermuda oceanographic expeditions. Families Cetomimidae and Rondeletiidae. Zoologica, Scientific Contributions of the New York Zoological Society v. 37 (pt 1, no. 5): 55-72, Pl. 1.
Maul, G.E. 1969. On the genus Cetomimus (Cetomimidae) with the description of a new species. Bocagiana. Museu Municipal do Funchal (História Natural) No. 18: 1-12.
McEachran, J.D. & J. D. Fechhelm. 1998. Fishes of the Gulf of Mexico. Volume 1: Myxiniformes to Gasterosteiformes. Univ. of Texas Press, Austin. 1-1112.
Moore, J.A., K.E. Hartel, J.E. Craddock & J.K. Galbraith. 2003. An annotated list of deepwater fishes from off the New England region, with new area records. Northeastern Naturalist v. 10 (no. 2): 159-248.
Paxton, J.R. 1989. Synopsis of the whalefishes (family Cetomimidae) with descriptions of four new genera. Records of the Australian Museum v. 41: 135-206.
Paxton, J.R., T. Trnski & G.D. Johnson. 2016. Cetomimidae (Pp. 2173-2181). In: Carpenter & De Angelis (eds.). 2016. The living marine resources of the Eastern Central Atlantic. vol. 3.
Tolley, S.G., J.V. Gartner, Jr. & T.M. Lancraft. 1989. Whalefishes (Beryciformes: Cetomimoidei) of the Gulf of Mexico. Bulletin of Marine Science v. 45 (no. 3): 671-677.
Other Notes
The only Cetomimus in the region that lacks cavernous tissue around the dorsal fin. This is present in both C. compunctus and C. hempeli, which share the character of a short slit behind the third gill arch (Maul, 1969; Paxton et al., 2016).
There is a relatively large spread of meristics and morphology in specimens identified as Cetomimus gillii from around the world, with some appearing to lack the gill slit behind the third arch, having no lappets on lateral pores, and extent of cavernous tissue. There are several undescribed species reported in Paxton (1989) and Paxton et al. (2016) that may eventually key to these aberrant specimens.