Varanus bennetti, Weijola & Vahtera & Koch & Schmitz & Kraus, 2020

Weijola, Valter, Vahtera, Varpu, Koch, André, Schmitz, Andreas & Kraus, Fred, 2020, Taxonomy of Micronesian monitors (Reptilia: Squamata: Varanus): endemic status of new species argues for caution in pursuing eradication plans, Royal Society Open Science 7 (5), pp. 1-28 : 61-66

3.5. Varanus bennetti sp. nov. figures 8–12

3.5.1. Holotype

USNM 507504 ( figure 8 a, b ), collected by Ronald Crombie, south of Ngaramasch village , Ngeaur Island, Palau, 31 July 1996 .

3.5.2. Paratypes

USNM 514125 , 521719 , Ngeaur Island , Palau . USNM 495369–70 , Palau. Commonwealth of the Northern Mariana Islands: Sarigan Island ( USNM 212494 ); Federated States of Micronesia: Losiep Island ( USNM 122560), Yap Island ( AMNH 00624–25 , BMNH 98.5 .27.1, SMF 32808–09 , USNM 130186, ZMB 17520–22 , 7619 and ZMH R-4727 ); Palau: Koror Island ( AMNH 70652–53 ), Ngcheangel Atoll ( USNM 495369 ) .

3.5.3. Diagnosis

Varanus bennetti can be distinguished from all other members of Euprepiosaurus by its unique combination of (i) dorsum black and evenly speckled with yellow scales, sometimes arranged in small groups of yellow scales, (ii) tongue dark blue/grey, (iii) venter cream coloured with pale grey crossbands, (iv) tail exceptionally long (F/SVL mean = 1.76, range = 1.60–1.89), high XY scale counts (148–160), (v) a clear yellow temporal stripe present in about half of the studied specimens, and (vi), in life, peach colouring on the throat.

3.5.4. Comparisons with other members of Euprepiosaurus

Varanus bennetti can be distinguished from V. caerulivirens , V. colei , V. doreanus , V. finschi , V. jobiensis , V. juxtindicus , V. melinus , V. obor , V. semotus and V. yuwonoi by having a fully dark blue/grey tongue rather than a (at least partly) pink or yellow tongue; from V. cerambonensis by the absence of dorsal cross-bands and its comparatively longer tail (F/SVL: 1.60–1.89 in V. bennetti versus 1.32–1.61 in V. cerambonensis ); from V. douarrha by the absence of dorsal ocelli and its comparatively longer tail (F/SVL = 1.60–1.89 versus 1.32–1.61); from V. indicus by the presence of a yellow temporal stripe in much of the population, generally higher scale counts (X: 41–48 versus 28–42 in V. indicus , XY: 148–160 versus 109–158 in V. indicus ), longer tail (F/SVL = 1.60–1.89 versus 1.22–1.70 in V. indicus ) and dark pigmentation on the lower part of the throat (versus dark pigmentation on throat normally absent in V. indicus ); from V. lirungensis by the absence of dorsal cross-bands and lower scale counts (P: 31–40 versus 38–47 in V. lirungensis , Q: 54–74 versus 79–88 in V. lirungensis , S: 101–126 versus 134–151 in V. lirungensis ); from V. rainerguentheri by its longer tail (F/SVL = 1.60–1.89 versus 1.36–1.47 in V. rainerguentheri ), higher average scale counts of all measured characters (table 4) and the peach color of the throat (versus cream in V. rainerguentheri ); and from V. tsukamotoi by its longer tail (F/SVL 1.60–1.89 (1.76) versus 1.33–1.73 (1.58) in V. tsukamotoi ), higher scale counts of all measured characters (table 4), and the peach colour of the throat of live animals (versus yellow in V. tsukamotoi ).

3.5.5. Description of the holotype

Subadult specimen of undetermined sex, total length 775 mm (SVL: 275 mm, F: 500 mm). Well preserved, without degradation or loss of keratin layer. There is a 25 mm long incision on the upper abdomen. Tail muscular, long, slender (F/SVL = 1.82, 38.46 times as long as high at midlength), round at base, becoming increasingly laterally compressed and gaining a double dorsal scale ridge distal to 45 mm posterior to vent. Dorsum of trunk and limbs black with scattered yellow scales in groups of one to four. Tail black with yellow marbling, without distinctive cross-bands. Venter cream with ca 20 moreor-less complete grey cross-bands. Throat cream with scattered brown scales laterally and near gular fold. Head various shades of brown, with a yellow post-ocular stripe. Tongue blue dorsally and pink ventrally except for a slightly darker median line. Teeth pointed and recurved.

Nuchal scales on anterior half of neck round to slightly oval, flattened or slightly domed, bordered by row of enlarged granules along lower and sometimes lateral margins. Interstitial skin covered by smaller granules. Nuchal scales on posterior half of neck elongate, keeled. Dorsal scales oval to elongate, keeled, becoming rectangular and increasingly elongate distal to base of tail. Suprabrachials and antebrachials elongate, keeled, surrounded by one or more rows of granules. Suprafemorals and tibials small, elongate, keeled, surrounded by numerous small granules. Subbrachials, antebrachials, femorals and tibials polished, round to slightly oval, with row of larger granules along posterior margin.

Infracarpals and infratarsals round, domed, dark brown in centre. Claws dark brown, sharp, recurved. Gulars yellow, enlarged, rectangular or irregular toward the snout, quickly decreasing in size ventrally to level of eyes. Towards the gular fold gulars round or slightly oval, bordered by row of granules along posterior and lateral margins, with one to three darker pits. Chest scales cream or grey, irregular in shape. Ventrals cream or grey, rectangular, with rounded posterior corners and small central keel. Subcaudals cream or yellow with brown anterior margin, rectangular, elongate, with sharp central keel. Lateral caudal scales half as long as subcaudals, elongate rectangular, with central keel and pit at posterior end.

Occipital scale roundish. Enlarged supraocular scales seven on each side. Four scale rows separate mouth and naris; nine dorsal scales between the nares. Enlarged supralabials 24 on each side. Rostral pentagonal; temporals small and irregular.

3.5.6. Scalation

S 138, XY 158, DOR 173, T 100, VEN 118, X 47, m 109, P 45, Q 90 and R 64.

3.5.7. Measurements

SVL 275 mm, F 500 mm, TL 775 mm; A 44.5 mm, B 25.5 mm, C 17 mm, G 13 mm, H 11.5 mm.

3.5.8. Molecular evidence

Varanus bennetti sp. nov. is resolved as a well-supported monophyletic lineage (JF 99, BS 99, syn 6) in both parsimony and likelihood-based phylogenies. The closest evolutionary relatives of the species are V. tsukamotoi (1.5/0.3% difference in ND4/16S) and V. lirungensis (1.4/0.3% difference), but the evolutionary affinities among these three species remain unresolved ( figures 3 and 4 ).

3.5.9. Variation and coloration in life

The light (probably cream coloured to yellow in life) temporal stripe is apparent in only part of the examined material. Some specimens lack tail bands altogether, whereas others show discernible bands. Crombie and Pregill [ 3] noted that live animals are black with prominent yellow dorsal rosettes and other irregular markings, and they have a vivid peach-coloured throat ( figures 9–12, and fig. 188 in [ 5]). They also noted the large size (up to 180 cm) attained by V. bennetti in Palau, which is

exceptional within the subgenus Euprepiosaurus . Fourteen specimens measured in the field on Sarigan had total lengths of 67–142 cm, tail/SVL of 1.69–1.88 and weights of 200–2180 g [ 54].

3.5.10. Etymology

The specific epithet is a genitive singular patronym in commemoration of the late Dr Daniel Bennett, 1966–2020, and his life-long commitment to the study and conservation of monitor lizards in Africa and Southeast Asia. As a vernacular name we suggest ‘Bennett’ s long-tailed monitor’.

3.5.11. Distribution

We have examined specimens of V. bennetti from Koror, Ngeaur and Ngcheangel islands in the Palau archipelago, from Yap and Losiep islands in the Federated States of Micronesia ( FSM), and from Sarigan Island in the Commonwealth of the Northern Mariana Islands ( CNMI) ( figure 1 ). Crombie & Pregill [ 3] also list this species (as Varanus cf. indicus ) from an additional two islands in the Palau group: Ngeriungs and Babeldaob.

3.5.12. Ecology

Crombie & Pregill [ 3] remarked that the monitors on Palau are decidedly terrestrial and prefer, when possible, to take refuge in terrestrial refuges rather than in trees. On Ngeaur, they are reportedly most common in the rugged limestone interior of the island [ 3]. Both features are atypical for species in the V. indicus Group, which usually seek refuge in trees and attain their highest densities in coastal habitats [ 55]. On Sarigan Island, the most common food items found in dissected lizards (n = 16) were

rats ( Rattus exulans ), insects and lizards [ 54]. In addition, that author found a high proportion of males among the specimens examined by him: only four of 16 specimens were females.

Figures

Figure 1. Map of the Pacific region showing the distribution of Varanus tsukamotoi (white dots), V. bennetti sp. nov. (red dots), V. lirungensis (yellow dot) and V. rainerguentheri (green dot).

Figure 3. Strict consensus of the nine most-parsimonious trees resulting from the TNT analysis. Jackknife resampling values greater than 50% are shown above, and the numbers of synapomorphies shared by each clade are shown below the nodes in parentheses. Branch lengths represent the number of optimized character-state changes.

Figure 4. Optimal maximum-likelihood tree resulting from the RAxML analysis. Bootstrap support values greater than 50% are shown on the nodes. Scale bar corresponds to the mean number of nucleotide substitutions per site.

Figure 8. (a) Dorsolateral and ventral aspects of the holotype (USNM 507504) of Varanus bennetti sp. nov. (b) Lateral profile of the head of the holotype (USNM 507504) of Varanus bennetti sp. nov.