Ramphotyphlops adocetus, Wynn, Addison H., Reynolds, Robert P., Buden, Donald W., Falanruw, Marjorie & Lynch, Brian, 2012

Wynn, Addison H., Reynolds, Robert P., Buden, Donald W., Falanruw, Marjorie & Lynch, Brian, 2012, The unexpected discovery of blind snakes (Serpentes: Typhlopidae) in Micronesia: two new species of Ramphotyphlops from the Caroline Islands, Zootaxa 3172, pp. 39-54 : 41-45

Ramphotyphlops adocetus sp. nov.

( Figs. 2 , 7 A)

Holotype. USNM 529971, an adult male from Pasa Island, Ant Atoll, Caroline Islands ( Federated States of Micronesia), collected by Otto Sirom on 15 July 1999.

Paratypes. USNM 558284–558299, Pasa Island, Ant Atoll, Caroline Islands ( Federated States of Micronesia), collected by Brian Lynch and Donald W. Buden on 30 August 2008.

Diagnosis. Ramphotyhlops adocetus can be distinguished from other Indoaustralian and Philippine typhlopids by the combination of 22 scale rows over the length of the body; the wedge-shaped snout, without a keratinized keel; and its broad, pyriform rostral.

Description of holotype. Male, total length 373 mm, tail length 20.1 mm, midbody diameter 9.8 mm, body diameter at vent 8.3 mm, diameter near midpoint of tail 7.2 mm. Middorsal scale rows 461 (not including intercalary scales), 476 (including intercalary scales—12 on left, 3 on right). Middorsocaudal scales 32 (not including two intercalary scales). Twenty-two scale rows around head (beginning about three transverse scale rows posterior to fourth supralabial) and continuing for length of body to about 4 mm anterior to vent, where paramidventral row on left divides at eight transverse rows anterior to vent, and paramidventral row on right divides at six transverse rows anterior to vent, with 24 scale rows around body from there to vent. Head tapered with rounded anterior tip when viewed from above; dorsal surface of snout sloped giving head a wedge shape in lateral profile; a keratinized beak absent ( Fig. 2 ). Eyes distinct, ca. 0.4 mm in diameter, lying beneath unpigmented windows in ocular scales.

Details of the head scalation can be seen in Fig. 2 . Salient features are: superior internasal suture short, incompletely dividing the nasal scale, extending forward obliquely from the nostril and extending under the rostral freeedge (but not penetrating the gland row under the rostral free edge), an underlying gland row not clearly visible; inferior internasal suture extending from the nostril to the second supralabial, with an underlying gland row. Rostral strongly pyriform viewed from above, 3.1 mm in width at its broadest (52% head width), then tapering to a rounded posterior tip. Four supralabial scales, increasing in size from first to last, with the third and fourth nearly equal in size and much larger than the first and second. The first supralabial (not visible in Fig. 2 ) is overlapped by the prenasal and overlaps the second supralabial. The second supralabial is about twice the size of the first, overlapped by the prenasal, postnasal, and preocular, and overlaps the third supralabial. The third supralabial extends dorsally to the level of the nostril, is overlapped by the preocular and overlaps the ocular and fourth supralabial. The fourth supralabial also extends dorsally to the level of the nostril, and is overlapped by the ocular. There are three postoculars on each side.

The dorsum is covered with dark brown melanophore pigmentation. On the head, this pigmentation covers the entire dorsal surface of the rostral, extending anteriorly and ventrally around the tip of the snout to the anteriormost ventral surface of the rostral; the prefrontal, frontal, interparietal, supraoculars, and parietals; the postnasals dorsal to the nostrils; the dorsal half of the right preocular, and all but the ventralmost left preocular; the oculars surrounding the unpigmented eye-windows; and the anterior edge and dorsal apex of the left fourth supralabial, and anterior- and dorsalmost edge of the right fourth supralabial. Immediately posterior to the fourth supralabial, dorsal pigmentation extends ventrally as a band of pigmented scales, three to five transverse scale rows in width, around the head to the ninth longitudinal row, with a gap of three unpigmented ventral rows (the midventral and two paramidventral scale rows).

Posterior to this band, the body has a dark brown longitudinal stripe 13 scale rows wide (the middorsal and six lateral scale rows on either side), with the scales in the middorsal and five lateral rows to either side continuously pigmented for the length of the body, but with scattered unpigmented scales occurring in the sixth lateral row, giving the stripe a ragged-appearing edge. Outside of this stripe, a few pigmented scales are scattered along the seventh lateral row, and two pigmented scales are present in the eighth row (both scales on the right side). The dorsal stripe increases in width to include most scales in the seventh lateral row approximately 4 mm anterior to the vent, and the proportion of pigmented scales in the eighth lateral row increases at the level of the vent. Beyond the vent, the dorsal stripe continues as a nearly straight-edged stripe, 17 rows wide for the first 5 mm posterior to the vent, after which the eighth row lateral to the middorsal becomes intermittently pigmented, but the seventh row remains continuously pigmented to near the tail tip, where loss of the scale row to either side of the middorsal reduces the width of the stripe from 15 rows to 13 rows in width. The terminal scale is pigmented. Other scales on the ventral head, body, and tail lack melanophore pigmentation.

Although sharply demarcated from the unpigmented scales on the venter, the dorsal stripe is darkest middorsally and gradually becomes paler laterally due to decreasing pigment density in the scales. In the lateralmost rows, the extent of pigmentation also decreases in the posterior and ventral portion of the scales, with pigmentation found in only the anterior half or less of many scales in the sixth row, and the anterior half or less in the pigmented scales in the seventh row from the middorsal.

The tail tapers only slightly for the first three-quarters of its length posterior to the vent, after which it tapers more abruptly to the tail tip; the terminal scale is cone shaped with a sharp keratinized spine.

A rectal caecum is not present. Retrocloacal sacs are present, both left and right extending into the body cavity for about 8 mm anterior to the level of the vent (about 2% of the body length). Exposed by dissection of the tail, the left inverted hemipenis is straight for its proximal half followed by two major coils in its distal half.

Variation. Total length 154–390 mm, middorsal scales 447–474. Tail length appears to be sexually dimorphic. Although there is no obvious difference in the number of middorsocaudals between males and females, males tend to have relatively longer tails (Table 1, Fig. 3 ). In addition, all males have tails with little taper through most of their length and with an abruptly tapered tip. In contrast, all females have tails that taper gradually through their length. Three postoculars on both sides were found in all specimens except two. One (USNM 558287) has four postoculars (three fully contacting the posterior edge of the ocular, the fourth wedged between the dorsalmost two of these three, and with only partial contact with the ocular) on the left side of the head, and the other (USNM 558286) has two postoculars on the left side of the head, the dorsalmost postocular spanning the width of the second and third longitudinal scale rows lateral to the middorsal, apparently resulting from fusion of the two postoculars corresponding to these two rows. The superior internasal suture extends under the rostral free edge (but does not penetrate the gland row at the edge of the rostral scale) in 12 paratypes. In the remaining four specimens, all in shedding condition, the superior internasal suture ends before the rostral free edge. Although no gland was clearly seen underlying the superior internasal suture in the holotype, a small round or oval gland could be seen underlying the superior internasal suture near its terminus under the rostral free edge in nine of the paratypes. All specimens have 22 scale rows around the body posterior to the head until just anterior to the tail where the paramidventral scale rows divide five to seven transverse rows anterior to the vent in 15 specimens, 10 rows in one specimen, to increase the number of rows around the body to 24. The color pattern of all paratypes (except four specimens in shedding condition, in which some details of the color pattern cannot be clearly discerned) is similar to that of the holotype. Five of the paratypes have pigmentation (in the dorsal and/or anterior portion of the scale) in one or both of the third supralabials, in addition to pigmentation in the fourth supralabials. All specimens also have a dorsal stripe that is 13 longitudinal rows in width on the body, with the sixth lateral row varying from being completely pigmented (no unpigmented scales in the row) to having scattered unpigmented scales in the row. A few pigmented scales are also scattered along the seventh lateral row in all paratypes, as in the holotype, except for two specimens. USNM 558288 has an approximately equal number of pigmented and unpigmented scales in the seventh row, and USNM 558291 has an approximately equal number of pigmented and unpigmented scales anteriorly in the row, but fewer unpigmented scales posteriorly in the row. Most specimens also have a few pigmented scales scattered along the eighth lateral row on one or both sides (as many as 12, but usually four or fewer). Tail coloration is similar to the holotype in all specimens, the dorsal stripe expanding to 17 rows in width near the level of the vent, then continuing either 15 or 17 rows in width to near the tip, where the width is reduced by longitudinal scale row loss. In addition to the holotype, a rectal caecum was searched for, but not found, in one other specimen (USNM 558295).

Protruded hemipenes (right, left, or both) are present in six males, for a total of ten hemipenes; nine appear to be fully protruded and one is clearly incompletely protruded. Of the nine fully protruded hemipenes, one was not measured due to its desiccated condition and one is too contorted to accurately measure. Six of the seven remaining hemipenes have helical coils and hairpin loops to varying degrees that make accurate measurement difficult, and the resulting measurements are probably underestimates of their lengths. These six vary in length from 30 to 40 mm and from 1.5 to 2.2 times the tail length. One protruded hemipenis (USNM 558297) ( Fig. 4 ) is fully straight and 47 mm in length, 2.4 times the length of the tail. All hemipenes are slender, solid awns (sensu McDowell 1974), less than 1 mm in diameter, that taper slightly along their length to a slightly constricted neck about 1 mm from the tip, which is followed by an expanded head with a bluntly pointed tip. For example, USNM 558297 has a diameter of about 0.8 mm at its base, tapers to 0.5 mm diameter just before the constricted neck, which is 0.8 mm from its tip, then expands in diameter to 0.5 mm before tapering to a rounded tip. A sulcus spermaticus runs the length of the hemipenes, ending at the tip. These hemipenes differ in two respects from the hemipenes of other Ramphotyphlops that we are familiar with. First, in both R. acuticaudus (USNM 558274 and 558282) and R. cumingii (National Museum of the Philippines /Cincinnati Museum of Natural History Philippine Biodiversity Inventory H-1547), the proximal portion of the protruded hemipenis is an expanded, fleshy base that appears to be everted, with a long, slender awn extending from a depression in its tip. In contrast, all hemipenes of R. adocetus are an awn extending directly from the vent, without an everted base. Although this differs from the hemipenes that we have observed in R. acuticaudus and R. cumingii , it is similar to the hemipenis of R. ligatus described and illustrated by Robb (1960: fig. 22; 1966: fig. 1). Second, in R. acuticaudus and R. cummingii the awn tapers gradually to a pointed tip, without the constricted neck or blunt, cone-like head at the tip of the awn observed in R. adocetus .

Etymology. The specific name adocetus is derived from the Greek adoketos meaning “unexpected or surprising,” in reference to the unexpected discovery of this species on a remote Pacific atoll.

Figures

FIGURE 2. Dorsal (top) and left lateral (bottom) views of the head of the holotype of Ramphotyphlops adocetus (USNM 529971). The illustration of the scale pattern on the left is based on the free edge of the scale plates. The scale bar represents three millimeters.

FIGURE 3. The relationship between relative tail length (tail length / total length) and the number of middorsocaudal scales in male and female specimens of Ramphotyphlops adocetus and R. hatmaliyeb.

FIGURE 4. The left protruded hemipenis of Ramphotyphlops adocetus, USNM 558297. The inset shows the tip of the hemipenis.

FIGURE 7. Radiographs of the head of Ramphotyphlops adocetus: (A) lateral view of USNM 529971, (B) dorsal view of USNM 558296; and the head of R. hatmaliyeb: (C) lateral view of USNM 558300, (D) dorsal view of USNM 558303. The arrows indicate the anterior projection of the premaxilla.