Cerberus rynchops (Schneider)

Murphy, John C., Voris, Harold K. & Karns, Daryl R., 2012, The dog-faced water snakes, a revision of the genus Cerberus Cuvier, (Squamata, Serpentes, Homalopsidae), with the description of a new species, Zootaxa 3484, pp. 1-34 : 14-17

Cerberus rynchops (Schneider)

Figure 7

Hydrus Rynchops Schneider 1799 , 1:246. [Based upon the illustration in Russell's Indian Serpents, 1: 23, pl. 17, 1796.] Type Locality: Ganjam, India (~ 19°22’N 85°03’E), is the locality given by Russell as the origin of the specimen in his drawing. There are at least two other localities on India’s east coast that contain the name “Ganjam:” Chinna Ganjam and Pedda Ganjam. Both of these are south of Ganjam, all three locations are coastal and within the range of this species. Here we restrict the type locality to Ganjam, India

Enhydris rynchops — Sonnini and Latreille 1801, 4:202.

? Boa moluroides Schneider 1801 , 1:279. Type Locality: none. Based upon our translation of Schneider’s descriptions it seems likely Boa moluroides is conspecific with rynchops based on the fact that it had 25 scale rows at midbody, but there is no type specimen, or type locality, making Boa moluroides a nomen dubium.

Hydrus cinereus Shaw 1802 , 3:567. Type Locality: Ganjam, India. Based upon Russell's Indian Serpents (1796) illustration 1:23, pl 17, and BMNH 1966.1.21.55–57.

Coluber cerberus Daudin, 1803c , 7:167. Based upon the illustration in Russell's Indian Serpents, 1: 23, pl. 17, 1796. Type locality: Ganjam India.

Coluber schneiderianus— Daudin 1803c, 7:170. “(d’apres la description du Boa moluroides de Schneider).”

Python molurus — Merrem 1820:89. Type Locality: none given. Merrem placed Daudin’s (7:170) “ Coluber scheinderianus ” in the synonymy of this name. The specimen has 144 ventrals and 57 subcaudals (P. m o l u r u s Linnaeus has more than 57 subcaudals and more than 240 ventral).

Python rhynchops ― Merrem 1820:90. “Bengala.” Note that the specimen was said to have 144 ventrals and 59 subcaudals.

Homalopsis cerberus — Fitzinger 1826:55.

Cerberus cerberus — Cuvier 1829, 2:81.

Cerberus grantii Cantor 1836:135 , [fide Smith 1943:393]. Type locality: “ India ”

Cerberus cinereus — Cantor 1839:54.. Based upon a colored sketch in the Bodleian Library, University of Oxford. Fide Smith 1943:393. Synonymized with rynchops by Günther (1864:341).

Homalopsis rhynchops ― Cantor 1847:941.

Cerberus rynchops ― Günther; 1864:279; Giebel 1861:109; Gunther 1864:279; Steindachner 1867:67; Gervais 1869:79; Anderson 1871a:34; Anderson 1871b:179; Günther 1872:590; Higgins 1873:34; Nicholson 1874:62; Theobald 1876:185; Müller 1878:605; Müller 1880:149; Murray 1886:381; Cope 1886:494; Keswall 1886:173; Murray 1886:49; Boulenger 1887:475; Boulenger 1890:374; Boettger 1892a:86; Boettger 1892b:124; Boettger 1893:3; Boulenger 1894a:85; Boulenger 1894b:616; Müller 1894:825; Boettger 1895:132; Boettger 1898:88; Bartlett 1896:101; Cardew 1896:595; Cope 1895:209; Boulenger 1896, 3:16; Boulenger 1897b:201; Boulenger, 1897:507; Bethencourt-Ferreira 1897:229; Boettger; 1898:88; Cope 1900:1115; Wall & Evans 1900:345; Werner 1900:501; Blanford 1901:382; Boettger 1901:326; Grijs 1901:33; Laidlaw 1901:578; Schenkel 1901:166; Wall & Evans 1901:612; Alcock & Rogers 1902:449; Boulenger 1903:175; Annandale, 1905:176; Rosén 1905:175; Wall 1905:307; Annandale 1907:398; Ambercrombie 1913:304; Annandale 1915:96; Phisalix & Caius 1918:939; Wall 1918:89; Annandale 1921:332; Wall 1921:257; Fejérváry 1923:167; Sarkar 1923:302; Werner 1923:162; Werner 1928:185; Haas 1931:401, Lloyd et al. 1933:19; Prater 1933:393; Smith 1943:393; Gharpurey 1944:87; Samuel 1947:133; Laurent 1948:8; Haas 1950:578; Forcart 1953:361; Smith et al. 1953:260, Deraniyagala 1955:65; Gharpurey 1962:75; Hundley 1964:21; Acharji & Mukherjee 1966:79; Dutt 1966:15; Hendrickson 1966:67; Minton 1966:143; Whitaker 1969:386; Gyi 1970:159; Singh et al. 1970:94; Murthy 1971:574; Minton 1975:22; Whitaker 1978: 44; De Silva 1980: 348; Supriatna 1982: 172; Daniel 1983: 105; Saha 1983a, b:4; Krishnan et al. 1985:119; Murthy & Rao 1986:620; Murthy 1987:10; Dowling & Jenner 1988:5; Jayne et al. 1988:1; Welch 1988:49; Dutta 1989:227; Price & Kelly 1989:247; Whitaker & Whitaker 1989:49; De Silva 1990:489; Gaulke 1990:18; Giesen 1993:265; De Silva 1994:15; Weinstein & Kardong 1994:1161; Murthy 1995:97; Brown et al. 1996:12; Whittin et al. 1996:406; Das 1998:46; Erdelen 1998:70; Gaulke 1998:140; Karns et al. 2000:391; Gayen 1999:18; Ferner et al. 2001:42; Khan et al. 2001:56; Porej 2001:27; Khan 2002:206; Fuchs & Fuchs 2003:232; Alfaro et al. 2004:1277; Murphy 2007:72; Alfaro et al. 2008:576.

Hurria rynchops ― Stejneger 1907:302; Stejneger 1910:105; Taylor 1922:111; Barbour 1912:123; Prater, 1923:159; Sworder 1923:66; Wall 1923:37; Sworder 1924:20; Wall 1924:86, 1925:817; Smith 1925:5; Raj 1927:183; Cochran 1930:30; Mertens 1930:210, 1957:30, 1959:9; Alcala 1986:143.

Cerberus rynchops ― Smith 1930:61.

[ Cerberus rynchops ] rynchops — Loveridge 1948:388.

Cerberus rynchops rynchops ― Gyi, 1970:160.

Diagnosis. Cerberus rynchops can be distinguished from all other members of the genus by its 25 (rarely 23) scale rows at midbody, the imbricate plate-like scales on the crown have a flat, thin appearance and are keeled anterior to angle of jaw; the last two upper labial are horizontally divided; the venter is mottled. Cerberus australis has 23 scale rows at mid-body, and the first upper labial does not contact the loreal (it usually does so in all other Cerberus species). Cerberus dunsoni has 23 scale rows at mid body, rounded juxtaposed scales on the crown, and a uniform black venter. Cerberus schneiderii usually has 23 scale rows at mid-body (rarely 21 or 25), the last upper labial is horizontally divided (as opposed to two in C. rynchops ), and the venter is mottled.

Variation. Largest male 777 mm TL with a 135 mm tail; largest female 886 mm TL with a 124 mm tail. Head is elongated, distinct from the neck and depressed; eyes are dorsal and slightly protruding. Many of the smaller head scales anterior to the angle of the jaw have keels. Rostral as tall as broad and pentagonal; nasal may be divided, undivided or semi divided; the nasal cleft may touch labial, internasal, or loreal; internasal divided (rarely single or semi-divided); and usually in broad contact with loreal posterior to the nasals. Frontal fragmented with one or two large anterior fragments and smaller posterior fragments; in most specimens largest remaining fragment shorter than supraocular; parietals fragmented into numerous small scales. Loreal may be single or double, contacts upper labials 1–3 or 1–4 (rarely 2–3 or 2–4). Supraocular single (rarely double); preocular single or double, usually one; subocular scales 1–3 (usually two), but may be completely absent with 5th or 6th upper labial entering the orbit. Upper labials 8 –10, usually 9, largest upper labial usually 6 (88% of 96 sides); the last two upper labials horizontally divided. Primary temporal scales may number 1–3, usually two. Lower labials 8–11, usually 9; first four contact anterior chin shields; largest is usually 7, but it can be 6 or 8; chin shields 2 or 3 pairs, anterior pair largest. Gular scales 5–8, usually 6–7.

Dorsal scale rows on anterior body 23–27; midbody scale rows 21–25, usually 23 or 25; posterior rows 16–20, usually 19. Specimens from India and Sri Lanka tend to have 23 midbody dorsal rows, while specimens from Myanmar tend to have 25 rows. Dorsal scales keeled and striated, except first row that shows no trace of keels; scales in first row are larger and more ovate than the rows toward the vertebral line. Ventrals rounded and wide; in males I35 — I52 (n=3 O, x = I44 •8), females I35 — I52 (n= 2I, x = I42 •8)• Anal plate điviđeđ• Subcauđals in males 56—67 (n= 2I, x =62•5), anđ 48—59 (n= I9, x =53•7) in females• Τail length̸SvL in males 2I—29 % (n=2 O, x=25•5%)﹔ females I7—25 % (n= I9, x = 2I •6%)•

In alcohol, dorsal surface of head uniform brown or gray with light upper and lower labials and a darker postocular stripe; dorsum gray or brown with a series of dark cross bands that extend onto the tail; belly yellow or cream, sometimes extending onto the first 2–3 dorsal rows; belly may be uniform or more often has a series of blotches or is mottled.

Distribution. Cerberus rynchops ranges from the vicinity of Mumbai, India along the Indian coast to coastal Bangladesh and Myanmar southward to a point north of Phuket, Thailand. It also occurs in the Andaman and Nicobar Islands. Exactly where its distribution stops and C. rynchops distribution starts is unknown, and we have not found a locality where both species co-exist. An old record from the Sind coast may be an error (see Murphy 2007).

Figures

FIGURE 7. The Karoo Bockadam, Cerberus rynchops. Photos by Aaron Lobo.