Saturday, March 26, 2016

Trans-Fly Mangrove Snake, Djokoiskandarus annulatus (de Jong, 1926)

Cantoria annulata de Jong, 1926: 304. Holotype: ZMA 11065. Type locality: Prins Frederik Hendrik Island, New Guinea.

Djokoiskandarus annulatus Murphy, 2011: 233.

Distribution: Southern coast of New Guinea, Trans-Fly region (Murphy, 2011).

Diagnosis:  Mostly smooth scales but some posterior dorsal scales keeled; dorsal scales in 21 rows at mid-body reduced to 19 rows posteriorly; internasal separates prefrontal and nasals scales, frontal contacts internasal.

Size: A single male measured had a total length of 578 mm and a 108 mm tail; and four females were 277 - 548 mm in total length. Parker (1982) measured a juvenile from Bobo Island as 289 mm total length, with a 44 mm tail, and a female from Daru Island had a total length of 568 mm, with an 80 mm tail. The single male had a tail that was 18.7% of the SVL; the females had tails that were 16 - 17.8% of the SVLs.

External Morphology:The head is depressed and slightly distinct from neck. The body is cylindrical and elongate. The eyes are dorsolateral and are round. The lower jaw is not countersunk.
On the head the rostral scale is pentagonal and is about twice as wide as high . The nasal scale may be divided or semi-divided, and the nasal cleft may touch the first or second labial and the internasal. The internasal scale separates the nasal scales and the prefrontal scales completely (in one specimen, MCZ 31057, the prefrontals are separated by a combination of the internasal and frontal) this is the only homalopsid known with this character state. The internasal may be asymmetrical, fragmented, or partially divided in some specimens. The frontal and the prefrontal scales contact the loreal; the frontal is hexagonal, broad, and about as wide as it is long. Parietals are large, and are about 1.5 times as long as the greatest length of the frontal. The loreal is single and in contact with upper labials 2 - 3 or 3 - 4; in one specimen (MCZ R129169) the loreal enters the orbit on the left side. The supraocular is quadrangular or pentagonal. There are two preocular scales; in one specimen the loreal covers a portion of the second preocular. The postocular scales number two, with the lower one sometimes extending under the orbit to separate the orbit from the upper labials. Subocular scales are absent. The temporal formula is 1 + 2, with the primary temporal being exceptionally large. There are 6 - 9 upper labials; the fourth labial enters the orbit and the largest varies from 4-8. Head scales have some very small tubercles.
             On the chin lower labials number 7 - 8, usually eight. The first three lower labials are in contact with the first pair of chin shields. There are two pair of enlarged chin shields that form the mental groove. Four or five gulars separate the chin shields from the first ventral scale.
            On the body dorsal scales on the neck and at midbody are in 21 rows, mostly ovate, smooth, and lack ornamentation (weak striations may be present). The dorsal scales at the posterior body are in 19 rows and tend to be ovate and smooth, except in the first three or four rows which are weakly keeled in females and juveniles and strongly keeled in males. The ventral scales are broad, smooth, round, and lack ornamentation. They are as wide as the height of five or six nearby dorsal scales. The single male had 182 ventral scales; three females had 167 - 178 ventral scales. The anal plate is divided; two specimens show a row of 5 - 6 scales bordering the posterior side of the vent.
            On the tail the dorsal scales are ovate and smooth. The 40 - 54 subcaudal scales are divided. A single male had 54 subcaudal scales; females had 40 – 45 subcaudal scales. At the base of the tail the width is 75% of the height.
            Color and Pattern. The dorsum has 62 - 68 narrow white bands less than one scale wide with alternating dark bands that are 1.5 - 2 scale rows wide. The head has a white nasal stripe extending onto the labials and white temporal spots. The chin is mottled. Each ventral has scattered pigment that gives the belly a mottled appearance, this continues onto the ventral surface of the tail.
            Sexual Dimorphism. A male (MCZ R129160) has strongly keeled dorsal scales on rows 1 - 3 starting about 21 ventrals anterior to vent. A female of similar size (CAS 133812) has scales in this region that are weakly keeled. Two juveniles also have weakly keeled scales in this region. The single male measured had a tail that was 22.9% of the SVL, while five females had tails that were 13.0 - 17.9% of their SVL. Thus, males have longer tails, and this character will probably be shown to be sexually dimorphic.

Natural History:  Little is known about the natural history of D. annulata. Parker (1982) reported specimens from Abam in mangrove and Nipa palm habitats. He (Parker, 1982) also reported a 568 mm (total length) female with five eggs. The Trans-Fly region is a mosaic of freshwater marshes and swamps as well as monsoon and mangrove forests.

Djokoiskandarus annulatus. JCM

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