Cerberus australis (Gray)

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 : 9-13

Cerberus australis (Gray)

Figure 4

Homalopsis australis Gray 1842:65 . Type Locality: Port Essington N.T. (~ 12°28’S 130°54’E) Australia. Holotype: BMNH 1946.1.2.40.

Cerberus australis — Gray 1849:65; Krefft 1869:22; Boulenger 1896:18; Kinghorn 1926:74; Kopstein 1926:90; Kinghorn 1929:90; Barrett 1950:113; Glauert 1950:20; Kinghorn 1956:90; Karns et al. 2000:391; Wilson & Swan 2003:384; Alfaro et al. 2004:1277; Murphy 2007:65; Alfaro et al. 2008:576.

Cerberus rynchops — Boulenger 1890:375. Thompson 1914:394; Gow 1977:pl. 5; Parker 1982:11; Whitaker et al. 1982:50; Cogger et al. 1983:210; Wilson & Knowles 1988:702; Gow 1989:76; Shine 1991a:120; Shine 1991b:14; Greer 1997:122.

Cerberus rynchops australis — Loveridge 1948:389; Mitchell 1955:376; Worrell 1963:105.

Cerberus rynchops novaeguineae Loveridge 1948:388 . Type Locality: Merauke, Dutch New Guinea. Syntypes: MCZ 22818, BMNH 1965.642. Collector: P. T. L. Putman. [Placed in the synonymy of C. australis by Murphy 2007:65.] Gyi 1970:169; Gow 1989:77; O’Shea 1996:116.

Comment. Murphy (2007) synonymized C. r. novaeguineae Loveridge with C. australis based upon significant shared morphology summarized in Table 3 .

Distribution. Cerberus australis inhabits the Sahul Self on the north coast of Australia from near Derby, Western Australia (~ 17°15’S 123°41’E) westward along the north coast to the Cape York Peninsula in Queensland Australia (~ 11°03’S 142°09’E). The eastern edge of the distribution of this species is uncertain. Wilson and Swan’s (2003) and Cogger’s (2004) distribution maps show it present as far north as the tip of the Cape York Peninsula. The most eastern locality based upon museum specimens is the Edward River (~ 14º54’S 141º37’E) in Queensland. It is also present on the southern coast of New Guinea. Kopstein (1926) reported this snake in the Moluccas as well as C. rynchops . While this may be based on an aberrant specimen of C. schneiderii , or confusion of nomenclature, evidence that this Australian snake has colonized the Indonesian Archipelago is based upon a single museum specimen (WAM 101620), examined by us which was collected at Waingapu, Sumba Island, Indonesia (10º 02’S 119º 46’E). This specimen is the only documentation of C. australis off the Sahul Shelf that we are aware of, and combined with Kopstein’s observations suggests the species has been able to cross Weber’s Line.

Diagnosis. Cerberus australis can be distinguished from all other members of the genus by its 23 scales rows (range 21–25) at midbody, imbricate scales on the crown, lack of keeled scales on crown anterior to the angle of the jaw; lack of contact between first labial and loreal; horizontally divided last upper labial; and mottled venter Cerberus dunsoni has 23 scale rows at mid body, the first labial usually contacts the loreal; and the crown has rounded juxtaposed scales, the venter is a uniform black. Cerberus microlepis has 27–31 scale rows at mid-body. Cerberus rynchops has 25 scale rows at mid body (rarely 23); keeled scales on the crown anterior to the angle of the jaw, and the last two upper labials are horizontally divided. Cerberus schneiderii usually has 23 scale rows at mid-body (rarely 21 or 25), the first upper labial usually contacts the loreal.

Variation. The largest male measured had a total length of 665 mm, with a 117 mm tail. The largest female measured had a total length (TL) of 737 mm, and a 106 mm tail. Scales in the occipital region of the head and on the neck lack keels. Keels are present on most dorsal rows, except the first one (some individuals may also lack keels, or have very weak keels on scale rows 2 through 4). The loreal is usually single, rarely double; usually not in contact with the subocular (75%). Most (82%) specimens have the preocular scale in contact with the upper labials 3-5; however, the preocular scale did not contact the upper labials in all (n=3) of the specimens from the Edward River, Queensland population we examined (this same population also showed a horizontally divided postocular).

These character states were also seen in specimens from other populations. Upper labials 2–4 contact the loreal; the upper labial under the orbit of the eye (and subocular scales) is usually 5 (64%), or 5–6 (25%), rarely are they 4, 4+5, or 6. The posterior upper labials are horizontally divided; the first divided upper labial ranged from 5 to 8, with 7 (54%) and 8 (39%) being the most frequent in 28 sides examined. The number of divided upper labials posterior to the eye ranges from 1–3, with one being the most frequent (39%), and 2 being the second most frequent (32%). Lower labials in contact with the anterior pair of chin shields 1–3 (11%) or 1–4 (89%) in 28 sides examined. Largest remaining fragment of the frontal scale usually longer than the supraocular; it was shorter than the supraocular in two (14%) specimens (SAM 2260, SAM 6651). The nasal cleft usually touches the second upper labial (82% of 28 sides), occasionally the first upper labial (14% of 28 sides), and rarely the loreal (3% of 28 sides). The internasal contacts the loreal in 57% of the 28 sides examined. Scale rows at midbody are usually 23 (71%) or 25 (21%), rarely 21 (8%). Two primary temporal scales vary greatly in size and shape. However, of 28 sides examined the dorsal scale was larger than the ventral scale in 27 (96%) instances. Three pairs of chin shields present in 11 (79%) specimens, two pairs of chin shields present in 3 (21%) specimens. Ventral scales in males 146–154 (n=5) and in females 142–153 (n=9). The divided subcaudal scales numbered 53–57 in males (n=5) and 47–51 (n=9) in females. The pattern is usually distinct; eye stripes were present in six specimens examined and absent in eight specimens; dorsum is gray with irregular dark cross bands or bars 2–3 scales long; these may be expressed as spots. Lateral blotches involving scale rows 1–3 have that pigment fused with darker pigment on the ventral surface.

Cerberus australis has several color and pattern morphs, individuals can be: a uniform red or gray or have partial transverse bands that may alternate sides, a mid-dorsal row of spots that may extend onto the tail; many specimens have a postocular stripe. The venter may be cream, yellow or salmon with mottling or blotches.

Cerberus rynchops rynchops (in part) Gyi, 1970:160.

Cerberus rynchops — Dunson & Dunson 1979: 661. Crombie & Pregill 1999:64; Murphy 2007:72.

Holotype. A female, AMNH 116021 from Micronesia: Palau Islands: Arakabesang (formerly Ngerekebesang) Island (~ 7°20’N 134°27’E).

Paratypes. Micronesia, Palau: AMNH: Oreor Island (~ 7°19’N 134°28’E) 70651; Arakabesang (formerly Ngerekebesang) Island (~ 7°20’N 134°27’E) 116020–21; UMMZ 65857; Babeldaob Island, Ulimang village (~ 7º 29’N 134º34’E) USNM 507563, Oreor Island, Ngesaol village 531967.

Diagnosis. Cerberus dunsoni can be distinguished from all other members of the genus with 23 scales rows at midbody by its rounded, juxtaposed, plate-like scales on the crown; these scales appear to be thickened compared to the scales of other Cerberus species. The 9th upper labial is horizontally divided. These characters, combined with large parietal scale fragments and its uniform black venter, make this a very distinctive species. The large, plate-like fragments of the parietals may fuse with the temporal scales. The parietal scales in other Cerberus are usually fragmented into small scales similar to other scales on the crown. The scales on the crown anterior to the level of the angle of the jaw usually lack keels; all other Cerberus with the exception of C. australis have scales with keels anterior to the level of the angle of the jaw. Crown scales are distinctly rounded and juxtaposed; in other Cerberus these scales tend to be sharp-edged and slightly imbricate. Light pigment forms an irregular ventrolateral stripe involving scale rows 1–2; this stripe involves rows 1–3 or 1–4 in other Cerberus with the exception of C. microlepis which has 27–29 scale rows at midbody. The ventral pattern is uniform black or dark brown in preserved C. dunsoni , while all other species have a mottled ventral surface, or one with an irregular central stripe of dark pigment. This species tends to have a broader, more robust head than the other species in the genus and it lacks the dorsolateral pattern of bars or incomplete cross bands.

Description of Holotype. A female, 687 mm SVL, 126 mm tail (tail incomplete). Head distinct from neck, body cylindrical, head dorsolaterally compressed. Rostral pentagonal, about as broad as tall; nasal scales divided, nasal groove contacts the first labial and internasal; internasal scale divided and makes narrow contact with loreal; prefrontal scales slightly smaller than nasals; frontal small, about the same size as the prefrontals, length less than the supraocular scale. Ocular ring consists of one supraocular, one preocular, two suboculars, and two postoculars on the left, one on the right. Loreal single, in contact with upper labials 1–4 (third upper labial on the left crowded out by the others and does not touch the loreal). Upper labials 10/11, ninth horizontally divided, 5–7 contact the suboculars. Lower labials 13, with 1–4 contacting anterior chin shield. Three pairs of chin shields, first pair is the largest, third pair smallest and barely distinguishable from the gulars. Dorsal scales keeled and striated; first dorsal row lacks keels; rows on anterior body 25, rows at midbody 23, rows at posterior body 17. Ventrals 147, rounded; subcaudals divided 44/45, tail tip missing (subcaudal counts incomplete).

Color and Pattern. In alcohol: head and dorsal coloration uniform dark brown, lower labials have some yellow pigment extending onto ventral surface of lower jaw. Belly uniform dark brown to black, on dorsal scale rows 1–2 light pigment forms an indistinct stripe. Ventral surface of the tail with a wide, dark medial stripe.

Variation in Referred Material. All specimens examined are females and similar to the holotype with the following exceptions: AMNH 116020 has 146 ventrals, 52/52 subcaudals, 1/2 postoculars, internasal does not contact the loreal, lower labials 13/14. AMNH 70651 has 18 scale rows anterior to the vent, 146 ventrals, 52/51 subcaudals, 14/15 lower labials. UMMZ 65857 has internasal divided into three parts, three suboculars on the right side, two post oculars on the right side, 50/51 subcaudals, and 19 scale rows anterior to the vent. SVL ranges from 228 to 687 mm; four complete tails range from 59–152 mm, and are 21–26% of the SVL. Dorsal scale rows 25 on neck, 23 at midbody, 17–19 at posterior body. Scales in the first row lack keels. Ventral scales in five females 144– 147. Subcaudals in five females: 50–54.

Distribution. Cerberus dunsoni is known only from the Palau Islands, Federated States of Micronesia. The type specimen and the paratype AMNH 116020 are from Arakabesang Island. AMNH 70651 is from Koror Island, now Oreor Island (~ 7°19’N 134°28’E) see Crombie and Pregill (1999). UMMZ 65857 is from Micronesia, Caroline Islands, Palau with no specific locality. Crombie and Pregill (1999) reported this species from Babeldaob (~ 7°29’N 134°34’E), Arakabesang (=Ngerekebesang) (~ 7º18”N 134º26’E), and Oreor islands. These are locations in the central and northern portions of the island group and suggest the species is probably widespread in the Palau Islands wherever appropriate habitat (mangroves and mud flats) can be found. The nearest Cerberus populations are found about 850 km west in the Philippines and about 830 km northwest of New Guinea and the Moluccas.

Etymology. This species is named in honor of William A. Dunson for his pioneering work in osmoregulation in reptiles.

Figures

FIGURE 4. The Australian Bockadam, Cerberus australis. Two color morphs from the Northern Territory, vicinity of Darwin. JCM.

Tables

TABLE 3. A comparison of C. australis and two of the paratypes of C. r. novaeguineae Loveridge suggesting that the two are conspecific.

Characteristics	australis	novaeguineae
N= (m/f)	5/9	1/1
Midbody dorsal scale rows	21–25	21–23
Ventrals males	146–154	153
Ventrals females	142–151	150
Subcaudals males	53–57	46+
Subcaudal females	47–51	43+
Labials contacting the loreal	2–4	2–4
Number of divided upper labials	1–3	3
Scales keeled anterior to jaw	no	no
Cerberus dunsoni sp. nov. Figure 5