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Spondylurus semitaeniatus (WIEGMANN, 1837)

IUCN Red List - Spondylurus semitaeniatus - Critically Endangered, CR

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Higher TaxaScincidae, Mabuyinae, Scincoidea, Sauria, Squamata (lizards) 
Common NamesLesser Virgin Islands Skink 
SynonymEuprepes semitaeniatus WIEGMANN 1837:135
Gongylus (Eumeces) agilis — REINHARDT & LUETKEN, 1863:229 (part)
Euprepes semitaeniatus — PETERS 1864:50
E[uprepes] semitaeniatus — PETERS 1871:400 (part)
Mabuya sloanii — BOCOURT 1879:401 (part)
Mabuia sloanii — BOULENGER 1887:193 (part).
Mabuya semitaeniata — STEJNEGER 1904:610 (claimed as distinct species)
Mabuya sloanii — BARBOUR 1914:320 (part)
Mabuya sloanii — SCHMIDT 1928:121 (part)
Mabuya sloanii — BARBOUR 1930:105 (part)
Mabuya semitaeniatus — GRANT 1931:218
Mabuya mabouia — BARBOUR 1935:129 (part)
Mabuya mabouya sloanii — DUNN 1936:544 (part.)
Mabuya mabouia — BARBOUR 1937:147 (part)
Mabuya mabouya sloanei — SCHWARTZ & THOMAS 1975:141 (part)
Mabuya mabouya sloanei — MACLEAN et al. 1977:30–35 (part)
Mabuya mabouya sloanei — HEATWOLE et al. 1981:34 (part)
Mabuya mabouya sloanei — SCHWARTZ & HENDERSON 1988:151 (part)
Mabuya mabouya sloanei — SCHWARTZ & HENDERSON 1991:457 (part)
Mabuya bistriata — POWELL et al. 1996:82 (part)
Mabuya sloanii — MAYER & LAZELL 2000:883 (part)
Mabuya sloanii — MIRALLES 2005:49 (part)
Mabuya sloanii — HENDERSON & POWELL 2009:293 (part)
Spondylurus semitaeniatus — HEDGES & CONN 2012: 194 
DistributionUS and British Virgin Islands (incl. St. Thomas, Capella, Little Buck); British Virgin Islands (Fallen Jerusalem Ginger Island, Great Camanoe Island, Guana Island, Little Thatch Island, Mosquito Island, Necker Island, Round Rock, Salt Island, Tortola, Virgin Gorda)

Type locality: "America"  
TypesHolotype: ZMB 1238, from "America," ex. coll. Marcus Elieser Bloch (see HEDGES & CONN 2012); holotype clarified as ZMB 1238, same specimen as examined by Schneider (1801:181), for syntype of Scincus auratus; originally from collection of Bloch). ZMB 5290 has been erroneously listed as type by several authors. 
DiagnosisDiagnosis. Spondylurus semitaeniatus is characterized by (1) maximum SVL in males, 74.7 mm; (2) maximum SVL in females, 82.9 mm; (3) snout width, 1.99–3.27% SVL; (4) head length, 15.8–19.4% SVL; (5) head width, 11.9–16.2% SVL; (6) ear length, 0.953–2.27% SVL; (7) toe-IV length, 8.33–12.0% SVL; (8) prefrontals, two (98%), four (2%); (9) supraoculars, three (1%), four (99%); (10) supraciliaries, three (2%), four (98%); (11) frontoparietals, two; (12) supralabial below the eye, five (28%), six (72%); (13) nuchal rows, one (14%), two (80%), three (6%); (14) dorsals, 57–65; (15) ventrals, 59–70; (16) dorsals + ventrals, 119–134; (17) midbody scale rows, 31–34; (18) finger-IV lamellae, 10–15; (19) toe-IV lamellae, 13–19; (20) finger-IV + toe-IV lamellae, 23–33; (21) supranasal contact, Y (96%), N (4%); (22) prefrontal contact, N; (23) supraocular-1/frontal contact, Y (38%), N (62%); (24) parietal contact, Y (98%), N (2%); (25) pale middorsal stripe, Y; (26) dark dorsolateral stripe, Y; (27) dark lateral stripe, Y; (28) pale lateral stripe, Y; and (29) palms and soles, pale (Tables 3–5).

Within the Genus Spondylurus, S. semitaeniatus differs from all other species except S. anegadae sp. nov., S. culebrae sp. nov., S. lineolatus, S. monae sp. nov., and S. sloanii by having a higher dark dorsolateral stripe width/ middorsal stripe width ratio (1.54–3.36 versus 0.115–1.27 in those other species; Fig. 79). From S. anegadae sp. nov., it differs by having a narrower, longer nostril (Fig. 58). It is separated from S. culebrae sp. nov. by having a shorter length of combined head scales (Fig. 62A). It is distinguished from S. lineolatus by having a longer head (head length 15.8–19.4% SVL versus 12.9–14.4% SVL in S. lineolatus) and by having two dark lateral stripes and two dark dorsolateral stripes (versus 10 dark stripes in S. lineolatus). From S. monae sp. nov., S. semitaeniatus differs by having a shorter rostral scale (Fig. 61).
Additionally, Spondylurus semitaeniatus is distinguished from other species in the genus except S. anegadae sp. nov. and S. lineolatus by having a middorsal stripe that is similar in color to the pale dorsolateral stripes (versus a middorsal stripe that is darker in those other species; Figs. 55 and 73). It is separated from S. fulgidus by having a higher number of supraciliaries (3–4 versus five in S. fulgidus), fewer total digital lamellae (178–215 versus 238 in S. fulgidus), and nearly non-overlapping dorsals + ventrals (119–134 versus 108–120 in S. fulgidus). It differs from S. macleani (Fig. 55G) by having longer dark dorsolateral stripes. It is distinguished from S. monitae sp. nov. (Fig. 73A) by having straighter dark dorsolateral stripes (versus dark dorsolateral stripes that bow inward on the parietal scales in S. monitae sp. nov.). There are frequency differences that also separate Spondylurus semitaeniatus from other species. From S. caicosae sp. nov., it differs by having a higher number of midbody scale rows (31–34 in 94% of specimens versus 27–30 in 92% of specimens belonging to S. caicosae sp. nov.). It differs from S. martinae sp. nov. by having fewer ventral scales (59–67 in 88% of specimens versus 68–71 in S. martinae sp. nov.).
The molecular phylogeny (Fig. 5) shows that Spondylurus sloanii is closer, genetically, to S. culebrae sp. nov., S. macleani, and S. monitae sp. nov. than it is to S. semitaeniatus. However, the greatest confusion in identification of S. semitaeniatus will likely be with S. sloanii because the two species appear superficially similar and occur in close proximity and sympatry in the Virgin Islands. The most reliable character in separating these two species is the width of the dark dorsolateral stripes compared with the pale middorsal stripe as measured at the forelimbs instead of the normal location for this measurement, at the ears (Fig. 80A). In both species, the dark dorsolateral stripes taper posteriorly until they eventually disappear. However, in S. sloanii, the dark dorsolateral stripes start tapering more quickly, before the forelimbs (e.g., compare pattern in Fig. 78E with that in Fig. 81F). The dark dor- solateral stripe/middorsal stripe ratio (at the forelimbs) is 1.25–2.68 in S. semitaeniatus versus 0.43–1.08 in S. sloanii. A second useful character in separating the two species, although not 100% diagnostic in itself, is prefron- tal separation (length of frontonasal-frontal suture). Spondylurus semitaeniatus has > 0.3% separation of prefron- tals whereas more than two thirds of S. sloanii have contact between prefrontals, or are within 0.3% SVL of contact (Figure 80B). In other aspects of pattern, adult S. semitaeniatus usually differ from S. sloanii in having a pale mid- dorsal stripe that is the same color as the pale dorsolateral stripes (darker than the pale dorsolateral stripes in S. sloanii), a dorsum that does not appear braided (versus dorsum with dark-edged scales giving a braided appearance in S. sloanii), and a pale lateral stripe (absent or barely evident in S. sloanii). Both species have been described as bronze or coppery, but the color of living and preserved S. semitaeniatus appears to be less so (more tan) than that of S. sloanii [HEDGES & CONN 2012].
CommentSynonymy: after HEDGES & CONN 2012 who revived this species from synonymy. For instance, Dunn, 1936:544 and Schwartz & Thomas, 1975:141 placed Euprepes semitaeniatus in the synonymy of Mabuya mabouya sloanii.

Distribution: erroneously reported from Culebra and Mona.

Conservation status: endangered (Adkins-Giese et al. 2014). 
EtymologyNot provided in the original description. However, the species name (semitaeniatus) is a feminine singular adjective derived from the Latin semi (half) and taenia (ribbon, stripe), hence half-striped, referring quite accurately to the dorsal pattern of this species, although such a pattern is shared with most other species in the Genus Spondylurus. 
  • Grant, C. 1931. Reestablishment of a scincid lost since 1837. J. Dept. Agric. Puerto Rico 15 (3): 217-218
  • Grant, C. 1932. Herpetological notes from the Puerto Rico area. J. Dept. Agric. Puerto Rico 16 (1): 161-165
  • Hedges, S.B. & Conn, C.E. 2012. A new skink fauna from Caribbean islands (Squamata, Mabuyidae, Mabuyinae). Zootaxa 3288: 1–244 - get paper here
  • Wiegmann, A. F. A. 1837. Herpetologische Notizen. Archiv für Naturgeschichte 3: 123-136 - get paper here
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