Crotalus polisi, Meik & Schaack & Flores-Villela & Streicher, 2018

Meik, Jesse M., Schaack, Sarah, Flores-Villela, Oscar & Streicher, Jeffrey W., 2018, Integrative taxonomy at the nexus of population divergence and speciation in insular speckled rattlesnakes, Journal of Natural History 52 (13 - 16), pp. 989-1016 : 1003-1005

Crotalus polisi sp. nov.

( Figure 5 ; Table 3)

Crotalus mitchellii, Grismer 2002a , Murphy and Aguirre-Léon 2002, Meik et al. 2012a, in part. Crotalus pyrrhus, Meik et al. 2015 , in part.

Description

A diminutive insular species of speckled rattlesnake with overall dusky appearance; background colouration is medium grey with a series of 36–48 indistinct and irregularly shaped dorsal body blotches, usually slate to charcoal grey in colour, only slightly darker than background; tail with 5–8 bands, last several are black with cream interspaces. The head is similar in colour to the body, with dark lateral suffusion and often with a faint postocular stripe and parietal blotches. Pattern is heavily punctated with black specks; blotches are usually wider than long, and merge with secondary lateral series to form muted crossbands on the posterior half of the body. A single row of nasorostral scales precludes contact between rostral and prenasal scales. Variation in selected phenotypic characters is presented in Table 3.

Diagnosis

The presence of nasorostral scales distinguishes the new species from all congeners except for species of the C. mitchellii complex. From C. mitchellii the new species differs in typically having more tail bands (range of mode or median between males and females of each species is presented for all comparisons: 5–6 vs 3–4), more dorsal body blotches (40–42.5 vs 32–34), fewer dorsal scale rows (23 vs 25), shorter ultimate supralabial scale (slightly longer than high vs twice as long as high), fewer supralabials (14 vs 16), fewer ventral scales in females (169 vs 180), fewer temporal scale rows (7 vs 8), colour pattern (mostly uniform colour pattern of slate or charcoal grey with indistinct blotches vs variable colour pattern), and smaller adult body size. From mainland populations of C. pyrrhus the new species differs in having typically more dorsal body blotches (40–42.5 vs 33–34), fewer dorsal scale rows (23 vs 25), fewer ventrals (168–169 vs 176), fewer temporal scale rows (7 vs 8), fewer supralabials (14 vs 16), colour pattern (mostly uniform colour pattern of slate or charcoal grey with indistinct blotches vs extremely variable), and smaller adult body size. From C. angelensis the new species differs in having typically fewer dorsal scale rows (23 vs 27), more supralabials (14 vs 13), fewer ventrals (168–169 vs 182–188), colour pattern (colour pattern of slate or charcoal grey with indistinct blotches vs buff or pink ground colour with grey to russet hexagonal blotches), and smaller adult body size. From C. thalassoporus , the new species differs in having more tail bands (5–6 vs 3–4), more dorsal body blotches (40–42.5 vs 31–32), more interrictals (25–26 vs 22–23), more prefrontals (21–27.5 vs 18–20), and colour pattern (colour pattern of slate or charcoal grey with indistinct blotches vs fawn, pinkish or beige ground colour with indistinct rust-brown blotches).

Holotype

Adult female, MZFC-26408, field number JMM-642, collected on 18 March 2010 by Jesse M. Meik, Sarah Schaack and Matthew J. Ingrasci. Rostral plate slightly broader than high (2.5 × 2.2 mm). Head scalation highly irregular, making some scale designations ambiguous. Rostral-prenasal contact precluded by 3/3 nasorostral scales; two internasals contact rostral; distinct canthal scales absent, but approximately 29 knobby scales of variable size and shape in prefrontal area; interocular distance spans a minimum of six scales; loreal scales 4/4, irregularly shaped; preocular scales 2/2, upper prefoveal scales irregular, lower prefoveal scales large and broadly contact first three supralabial scales on both sides; subocular scales separated from supralabials by three scales at midpoint of eye; supralabial scales 14/14; infralabial scales 15/15; interrictal scales 25; dorsal scale rows at midbody 23; ventrals 168 (exclusive of one preventral); subcaudal scales 17, undivided; rattle fringe scales 12; rattle segments 6, button present.

Measurements. Snout–vent length (SVL), 445 mm; tail length, 23 mm; head length (rostral plate to articulation of mandible with quadrate), 20.7 mm; head width (at widest point just anterior to articulation with mandible), 19.9 mm; proximal rattle segment width, 8.5 mm.

Colouration and pattern in preservative. Head with diffuse black speckling; lateral surfaces of head dusky with faint postocular stripe; labial scales with cream blotches (appearing as ‘blotch negatives’ against surrounding ground colour); ventral surface of head cream with faint black specks on periphery, ventral surface of body also cream with diffuse black specks, becoming more prominent on posterior one fourth of body; 38 dusky grey body blotches with narrow (0.5–2 scales long) cream interspaces; blotches indistinct with ill-defined borders, all wider than long, fusing with faint lateral blotch series over posterior third of body to form crossbands; five tail bands, distal four black and only one to two scales long.

Type locality

Cabeza de Caballo Island , Municipality de Ensenada, Baja California, Mexico . Coordinates: N 28.971 W 113.479 ( Figure 5 ).

Type deposition

Holotype at MZFC-UNAM; paratypes at MZFC-UNAM ( MZFC 26407 , MZFC 26409 ) and at UTAARDRC (UTA R-59763, UTA R-59764, UTA R-59765).

Etymology

The specific name is a patronym honouring the late Gary A. Polis of the University of California Davis, a renowned arachnologist and desert food-web ecologist, who died at sea on 27 March 2000 when his research vessel capsised in a gale while returning to Bahía de Los Angeles from an expedition to Cabeza de Caballo Island. In addition to Polis, four other researchers, including postdoctoral fellow Michael D. Rose of UC Davis, and Takuya Abe, Masahiko Higashi and Shigero Nakano of Kyoto University, Japan, perished on that day. Four other UC Davis researchers and students survived the tragedy, and by their accounts, the deceased heroically gave their lives to help ensure their survival.

Figures

Figure 5. Type localities and specimens photographed in situ for new species described herein. Piojo Island in foreground with Angel de la Guarda Island in the distance (upper left); western slope of Cabeza de Caballo Island in foreground with Ventana Island and peninsular mainland in the distance (upper right); paratype of C.thalassoporus (UTA R-59767) basking on a rock outcrop in the intertidal zone (lower left); holotype of C. polisi (MZFC-6248) coiled among boulders near the crest of the island (lower right).