AUSTRALIAN BIODIVERSITY RECORD - Calodema

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Australian Biodiversity Record, 2007 (8): 1-124Genus Hydrophis Sonnini and Latreille, 1802Hydrophis Sonnini de Manoncourt, C.S. and Latreille, P.A. (1802): Hist. Nat. Reptiles [p. 193].Type species: Hydrophis laticauda Sonnini and Latreille, 1802 by subsequent designation[see Smith, M.A. (1926). Monogr. Sea Snakes]Dolichodira Wall, F. (1921). Ophidia Taprobanica or the Snakes of Ceylon [p. 399]. Typespecies: Hydrophis diadema Günther, 1864 (= Hydrophis torquata Günther, 1864) bymonotypy.Polypholophis Wall, F. (1921). Ophidia Taprobanica or the Snakes of Ceylon. [p. 380]. Typespecies: Hydrophis neglectus Wall, 1906 (= Hydrophis stricticollis Günther, 1864) bymonotypy.Porrecticollis Wall, F. (1921). Ophidia Taprobanica or the Snakes of Ceylon. [p. 335]. Typespecies: Hydrophis obscurus Daudin, 1803 by monotypy.Diagnosis: A genus of small to moderate-sized Hydrophiid snakes with a small head notdistinct from the narrow cylindrical neck, and the anterior part of body usually much moreattenuate than the posterior which is robust, deep and highly compressed. Readilydistinguished from all other genera by the following combination of characters: head shieldsenlarged, symmetrical; less than 9 maxillary teeth following fang; in all but one species, theanterior part of maxilla is arched upwards, the tip of the longer fang on a line connecting thetips of the solid maxillaries (in the exception, Hydrophis elegans, the anterior part of maxillanot arched upwards, the tip of the fang projects slightly below a line connecting the tips of thesolid maxillaries); parietal bone not contacting prefrontal; valvular nostrils and lingual fossa;rostral normal, triangular, broader than high; 3rd and 4th supralabials contacting orbit; firstinfralabial normal, about as long as pregenial; nasal separated from preocular by high 2ndsupralabial; mental groove present and distinct; mental triangular, broader than long, and notpartially hidden in the shallow mental groove; anterior chin scales large, and usually borderingmental groove; body scales imbricate, with those on neck and posterior of body each with acentral tubercle or short keel; usually 25 or more scale rows on neck; mid-body scales in 35-50 rows; ventrals small, about 325-515; posterior ventrals distinct, mostly undivided, neverfoliform and barely wider than adjacent body scales; tail strongly compressed vertically,paddle-like; ovoviviparous. Etymology: The name Hydrophis means ‘water snake’, and isderived from the Greek ‘hydros’ - water, and ‘ophis’ - snake. Content: Hydrophis atricepsGunther 1864; Hydrophis bituberculatus Peters 1872; Hydrophis brooki Gunther 1872;Hydrophis elegans (Gray 1842); Hydrophis fasciatus (Schneider 1799); Hydrophis klossiBoulenger 1912; Hydrophis laboutei Rasmussen and Ineich 2000; Hydrophis lamberti Smith1917; Hydrophis lapemoides (Gray 1849); Hydrophis mcdowelli Kharin 1983; Hydrophismelanosoma Gunther 1864; Hydrophis obscurus Daudin 1803; Hydrophis parviceps Smith1935; and, Hydrophis vorisi Kharin 1984. Content in Australia: Hydrophis atriceps Gunther,1864; Hydrophis elegans (Gray, 1842); Hydrophis mcdowelli Kharin, 1984; Hydrophismelanosoma Gunther, 1864; Hydrophis vorisi Kharin, 1984.Hydrophis atriceps Gunther, 1864Hydrophis atriceps Günther, A. (1864): Reptiles of British India. [p. 371, pl. 25 fig. 1]. Typedata: syntypes BMNH 1946.1.2.62, BMNH 63.9.29.50. Type locality: Thailand.Hydrophis alcocki Wall, F. (1906): Mem. Asiat. Soc. Beng. 1: 277-299 [p. 288, pl. 15 fig. 3].Type data: holotype IM 14470 [see Smith, M.A. (1926). Monogr. Sea Snakes (Hydrophiidae)].Type locality: Puri, Orissa, India.Disteira cincinnatii van Denburgh, J. and Thompson, J.C. (1908): Proc. Calif. Acad. Sci. 3: 41-48 [42, pl. 1]. Type data: holotype CAS 15016. Type locality: 1 mi[les] NE of Cavite, ManilaBay, Philippines.Description: This species has a relatively small head which is barely distinct from the neck.The anterior part of body is much more slender than the posterior which is deep and highly36
Australian Biodiversity Record, 2007 (8): 1-124compressed. The head is black, even in adults, and sometimes has a yellow spot behind eyeand/or nostril. The base body colour is essentially pale ranging from yellow through variousshades of lighter brown. Young specimens are prominently marked with series of 50 to 70dark blackish transverse bands across the dorsum, with some completely encircling the body.However, this banding is less distinct with age, with adults having more of a blotched pattern.The ventrals are black anteriorly, but progressively becoming paler posteriorly to more of adark grey on the last third of the venter and tail. It is readily distinguished by the followingcombination of characters: head shields enlarged, symmetrical; anterior part of maxilla archedupwards, the tip of the longer fang on a line connecting the tips of the solid maxillaries; 5-6maxillary teeth following fang; parietal bone not contacting prefrontal; rostral normal,triangular, broader than high; 3rd and 4th supralabials contacting orbit; first infralabial normal,about as long as pregenial; nasal separated from preocular by high 2nd supralabial; mentalgroove present and distinct; mental triangular, broader than long, and not partially hidden inthe shallow mental groove; anterior chin scales large, and usually bordering mental groove;body scales imbricate, with those on neck and posterior of body each with a central tubercleor short keel; usually 25-30 scale rows on neck; mid-body scales in 35-49 rows; ventralssmall, about 320-515; posterior ventrals distinct, mostly undivided, never foliform and barelywider than adjacent body scales. A maximum total length of only around 1.2 m. is attained; atbirth the young are around 300mm in length. Females are sexually mature at around 650 mmin total length, and females tend to be somewhat larger than males and reach a longermaximum length. Males tend to have longer tails than females.Distribution: This species is known mainly from South East Asia - such as Singapore,Thailand, Vietnam and China - although it extends into the waters of Indonesia and thePhilippines to New Guinea and Australia. In Australian waters it is only known from theArafura Sea between the Northern Territory, Queensland and New Guinea.Habitat: Inhabits reefs in relatively shallow continental waters. It has been observed in wateraround 20 metres deep.Biology/Ecology: This is a fast swimming, essentially diurnal species that feeds on a variety ofsmall fishes such as eels near the bottom. When ascending to the surface to breath duringthe day, its movements are swift and direct to gain a quick breath of air before rapidlyreturning to the bottom. However, at night it has been observed casually swimming near thesurface. The reproductive biology various somewhat across this species enormous range,with oviducal young being present in the late Dry Season (May-August) to early Wet Season(July-December) in Indonesia. However, in the Philippines, oviducal young have beenrecorded in the early Dry season (January). This implies that young are born during the earlyWet Season to early Dry Season. Litter size ranges from 1 to 10 (usually 3 or 4).Toxicity: This species rarely attempts to bite under normal circumstances, but caution shouldnevertheless be exerted, because its venom is highly toxic to humans. Urgent medicalattention should always be sought in the event of a bite from this species.Survival Status: Protected under the Qld Nature Conservation Act (1992) and the TerritoryParks and Wildlife Conservation Act (1998). Listed as a Marine Protected Species under theAustralian Environmental Protection and Biodiversity Conservation Act (1999). Probably notunder threat, but its restricted distribution in Australian waters could potentially make itvulnerable in some parts of its range.Etymology: The name 'atriceps' means 'dull black head', and refers to the head colouration ofthe species.37
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AUSTRALIAN BIODIVERSITY RECORD - Calodema

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