Varanus louisiadensis, Weijola & Kraus, 2023
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publication ID |
https://doi.org/ 10.1080/00222933.2023.2218574 |
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DOI |
https://doi.org/10.5281/zenodo.8221620 |
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persistent identifier |
https://treatment.plazi.org/id/03EF87F6-9613-FFA3-5B9F-FE41FE40FE14 |
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treatment provided by |
Plazi |
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scientific name |
Varanus louisiadensis |
| status |
sp. nov. |
Varanus louisiadensis sp. nov.
( Figures 3–6 View Figure 3 View Figure 4 View Figure 5 View Figure 6 )
Holotype
ZMUT Sa 197 ( Figures 3 View Figure 3 , 4 View Figure 4 ) collected by Valter Weijola, 22 April 2013, at Bwagaoia , Misima Island, Milne Bay Province, Papua New Guinea.
Paratypes
Papua New Guinea: Milne Bay Province: AMNH 76828 View Materials , ZMUT Sa196, Sa198 (Misima Island), ZMUT Sa199 ( Figure 5 View Figure 5 )–200, AMNH 76755 View Materials (Rambuso, Sudest Island), ZMUT Sa201 ( Figure 6 View Figure 6 ), AMNH 76735–76737 View Materials (Saman [ ZMUT], Jinian [ AMNH], Rossell Island ) .
Etymology
The specific epithet refers to the Louisiade Archipelago of Milne Bay Province, Papua New Guinea, where this species is endemic.
Diagnosis
Varanus louisiadensis sp. nov. is a member of the subgenus Euprepiosaurus , which is defined by having the unique combination of an asymmetric sperm groove on the hemipenis and a laterally compressed tail ( Ziegler et al. 2007). Molecular phylogenetic analyses place it within the V. indicus species group defined by the unilateral paryphasmata ornamentation of the hemipenis and lack of blue pigmentation on the tail ( Ziegler et al. 2007; Weijola et al. 2019). It can be distinguished from all other species of Euprepiosaurus by its unique combination of: (1) dorsum black with more-or-less well-defined crossbands composed of yellow ocelli and/or dots, better defined in juveniles and subadults than adults; (2) tail black with distinct yellow bands, better defined in juveniles and subadults than adults; (3) tongue tines and a variable section of the mid-dorsal tongue surface dark grey, the remainder being pink; (4) pink-orange pigmentation usually present on cheeks and sides of neck; (5) venter pale yellow; (6) mid-body scale rows (S) 142–163; (7) mid-dorsal scale rows (XY) 139–169; (8) ventral scale rows (T) 101–113; (9) scales around neck (m) 101–118.
Comparisons. Varanus louisiadensis sp. nov. can be distinguished from V. doreanus and V. jobiensis (both present in Milne Bay Province but not in the Louisiade Archipelago) by the lack of blue pigmentation on the tail (vs present in V. doreanus and V. jobiensis ); and from V. chlorostigma by the presence of yellow dorsal ocelli (vs absent in V. chlorostigma ) and the bi-coloured pink/grey tongue (vs completely grey/blue in V. chlorostigma ).
Within the V. indicus group, Varanus louisiadensis sp. nov. is only likely to be confused with the remotely allopatric V. colei , V. douarrha , V. finschi , V. indicus or V. lirungensis , with which it shares a similar dorsal pattern composed of transverse bands of yellow ocelli. It is similar to V. colei in most scalational characters, but has slightly higher averages of S (153.5 vs 146) and m (109.6 vs 102.3) scale counts, and lacks the bright white gular region that characterises V. colei . It can be distinguished from V. douarrha by its uniformly yellow/ orange throat (vs marbled with dark grey in V. douarrha ) and its higher average S (153.5 vs 140.9), T (107.4 vs 96.9), XY (153.3 vs 136) and m (109.6 vs 100.7) scale counts. It can be distingushed from the more distantly related V. finschi by having a pink tongue with dark pigmentation on the distal part (vs a uniformly pink-white-yellow tongue in V. finschi ), and from V. indicus by the lack of a distinct yellow temporal band (vs present in V. indicus ). It can be distinguished from V. lirungensis by its average higher scale counts for characters Q (92.1 vs 83), S (153.5 vs 141.6), T (107.4 vs 97.5), XY (153.3 vs 139.8) and m (109.6 vs 97.8).
Description of the holotype. Well-preserved juvenile with a small incision on left thigh from where tissue was removed. Dorsal ground colour of body, tail, head and limbs black, covered by distinct crossbands of yellow rosettes and dots. Habitus slender; total length 585 mm (SVL = 240 mm, F = 345 mm); tail 1.44 times as long as body, 36.3 times as long as high (9.5 mm) at midlength, round at base, becoming laterally compressed distally, and with mid-dorsal ridge two scales wide starting at about 30 mm from base. Thirteen discernible cream-coloured crossbands on distal ¾ of the tail. Venter cream yellow, marmorated with brown, with incomplete crossbands between hind legs and gular fold that are one scale row wide. Throat cream with scattered brown scales laterally. Ventral surfaces of limbs cream with narrow, pale-brown bands and dots. Under tail cream with interspersed brown scales at base of tail. Dorsal surfaces of limbs black with yellow dots, stripes, and ocelli composed of about 1–8 scales.
Head 1.82 times as long as wide, black with yellow dots and short stripes and with bright-yellow parietal scale. Well-defined temporal bands or postocular stripes lacking on both sides of head. Labial scales white at snout but each from below nostril to labial commissure with a brown dot. Nostrils oval, situated slightly nearer to snout than eye. Nasal capsules expanded, with shallow sagittal groove on rostrum.
Nuchal scales irregular in shape on anterior part of the neck, round on mid-neck, smaller and elongate on lower neck, all surrounded by granules. Dorsal scales somewhat irregular in size, elongate, keeled, each surrounded by few granules, most with single pit. Lateral caudal scales regular in size and shape, rectangular, flattened, usually with single posterior pit. Mid-ventral caudal scales twice as wide as mid-dorsal caudal scales, elongate, with sharp keel. Mid-ventral scales rectangular, flat, posterior margin rounded and bordered by row of granules. Scales on chest irregular in size, round to polygonal, each surrounded by few granules. Gular scales roundish to polygonal, each surrounded by granules. Mental scales elongate, rectangular to polygonal.
Infrafemorals and infratibials round, each surrounded by row of granules along lateral and posterior margins. Infracarpals and infratarsals round and highly domed, with brown traction pads on most scales. Subdigital scales domed, of irregular size and shape. Fourth toe with row of 11 (R) and 12 (L) enlarged scales along outer margin; third toe with four slightly enlarged scales along outer margin. Claws dark brown, sharp, and recurved.
Occipital scales flattened, relatively small, irregularly polygonal. Supraocular scales 8 (R) and 7 (L), enlarged, irregular in shape and size, each densely covered with pits. Scales of forehead and rostrum polygonal, flattened, larger than occipital scales. Supralabials pentagonal or rectangular, covered with pits. Infralabials of irregular size, pentagonal or polygonal. Tines of tongue blue, its trunk pink, except for thin, blue median line on both dorsal and ventral sides.
Scale counts. S: 157, XY: 155, DOR: 164, T: 103, VEN: 123, X: 43, m: 105, P: 42, Q: 93.
Measurements. SVL: 240 mm, F: 345 mm, TL: 585 mm, E: 135 mm, D: 84 mm, A: 40 mm, B: 22 mm, C: 15.5 mm, G: 10.5 mm, H: 8.5 mm, I: 21.5 mm.
Scale counts, measurements and proportion indices of the type series. See Table 3 View Table 3 .
Variation and colouration in life. Variation is mostly seen in the dorsal crossbands which can be composed of either spots and ocelli or spots only ( Figures 4–6 View Figure 4 View Figure 5 View Figure 6 ). Judging from the material at hand these also tend to become less distinct as the animals age. The extent of grey pigmentation on the tongue varies considerably between individuals, varying from colouring only the tines to encompassing the whole dorso-distal half of the trunk.
Range. Varanus louisiadensis sp. nov. has been recorded from coastal and lowland areas on all three major islands of the Louisiade Archipelago: Misima, Sudest, and Rossel ( Figure 7 View Figure 7 ). Considering the good dispersal abilities of monitors in the V. indicus group it can also be expected to occur on nearby smaller islands with suitable habitat, such as Paneati and Panatinane islands, but its presence on satellite islands of the Louisiade Archipelago has yet to be confirmed.
Natural history. Varanus louisiadensis sp. nov. does not appear to be particularly abundant on any of the larger islands in the Louisiades, and active searches on Misima, Sudest and Rossell by VW in 2013 resulted in a total of 16 sightings and five collected specimens over the course of three weeks. All of these observations were made around the coast in stands of mangrove or other coastal woodlands, often intermixed with coconut plantations.
Remarks
The molecular phylogeny of Euprepiosaurus published by Weijola et al. (2019) retrieved monophyly of the samples of V. louisiadensis sp. nov. from Misima, Sudest, and Rossel with high support. The samples from Misima and Sudest were genetically most similar and formed a sister group to those from Rossel. Varanus louisiadensis sp. nov. formed a sister lineage to V. chlorostigma ; that relationship was not well supported, but it is sensible on geographic grounds alone. The shortest ND4 (NADH dehydrogenase subunit 4) pairwise distances of V. louisiadensis sp. nov. are to V. chlorostigma (3.3%) and Varanus sp. from the Admiralty Islands (3.4%).
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