Thamnophis atratus KENNICOTT, 1860
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Thamnophis atratus
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| Higher Taxa | Colubridae (Natricinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes) |
| Subspecies | Thamnophis atratus atratus (KENNICOTT 1860) Thamnophis atratus hydrophilus FITCH 1936 Thamnophis atratus zaxanthus BOUNDY 1999 |
| Common Names | E: Pacific Coast Aquatic Garter Snake, Santa Cruz Garter Snake atratus: Santa Cruz Garter Snake hydrophilus: Oregon (Gray) Garter Snake zaxanthus: Diabolo Garter Snake G: Santa-Cruz-Strumpfbandnatter |
| Synonym | Thamnophis atratus (KENNICOTT 1860: 296) Eutaenia atrata KENNICOTT in COOPER 1860 Thamnophis elegans aquaticus FOX 1951: 493 Thamnophis couchi atratus — STEBBINS 1985: 206 Thamnophis atratus — ROSSMAN & STEWART 1987 Thamnophis atratus — CROTHER 2000 Thamnophis atratus — CROTHER et al. 2012 Thamnophis atratus — WALLACH et al. 2014: 720 Thamnophis atratus atratus (KENNICOTT 1860) Eutaenia atrata KENNICOTT in COOPER 1860: 296 Thamnophis elegans atratus — FOX 1951 Thamnophis atratus atratus — CROTHER 2000 Thamnophis atratus atratus — CROTHER et al. 2012 Thamnophis atratus hydrophilus FITCH 1936 Thamnophis ordinoides hydrophila FITCH 1936 Thamnophis couchi hydrophilus Thamnophis atratus hydrophilus — ROSSMAN et al. 1996 Thamnophis atratus hydrophilus — CROTHER 2000 Thamnophis atratus hydrophilus — CROTHER et al. 2012 Thamnophis atratus zaxanthus BOUNDY 1999 Thamnophis atratus zaxanthus — CROTHER 2000 Thamnophis atratus zaxanthus — CROTHER et al. 2012 |
| Distribution | USA (coastal C California, SW Oregon) atratus: California; Type locality: "California." Listed as "San Francisco, California," by Fitch, 1940: 89, and Cochran, 1961: 181. hydrophilus: S Oregon, N California zaxanthus: Inner Coast Range from Napa and Solano to Santa Barbara counties, and the Santa Lucia Range. Type locality: 2 miles S Gilroy Hot Springs, Santa Clara County, California. |
| Reproduction | ovoviviparous. |
| Types | Lectotype: USNM 970, (R.D. Cutts, 1854), designated by Fitch, 1940: 89. Holotype: MVZ 207940 (adult female) [zaxanthus] Holotype: MVZ 48196 (adult male) [aquaticus] Holotype: MVZ 18127 (adult male) [hydrophilus] |
| Diagnosis | Diagnosis. A short, somewhat stout garter snake with pointed snout and remarkably uniform head scales: almost always 8 upper labials, 10 lower labials, 1 preocular, and 3 postoculars on each side (table 2). Internasals usually longer than broad, pointed anteriorly, and in narrow contact with rostral; sixth and seventh upper labials relatively large and taller than long, resembling'those of terrestrial races rather than those of other aquatic races, in which rows of upper labials are * practically straight (Fox 1951: 489) Coloration: Broad orange or orange-yellow dorsal stripe usually covers at least 0.66-1.66 rows of scales, frequently 3 full scale rows, and occasionally only central row involved. Lateral stripes absent in blue-black individuals from San Francisco peninsula, but elsewhere usually present and conspicuous pale yellow. Top of head usually olive, dark olive, or blue black; chin and throat bright lemon yellow, this color usually extending to or over lower labials; upperlabials generally pale yellow. Iris very dark, almost black except for loose silvery network in most specimens. Dorsal ground color blue black, black, or dark olive with distinct or indistinct black spots; no red spotting. Ventral surface varies froih deep blue to pale blue or green; in most specimens central part of each ventral scute irregularly blotched with Salmon-Orange or Capucine Orange. Blotching begins in anterior third'of body and increases posteriorly (Fox 1951: 490) Scalation: Maximum number of body scale rows, 19; always 19 at neck and thoracic regions; almost always 15 at posterior end of body, rarely 17. Ventral scutes range from 145 to 169 in males and from 138 to 167 in females; caudal scutes range from 70 to 89 in males and-64 to 82 in females (Fox 1951: 490) Comparisons: T. e. atratus intergrades with T. e. aquations and occupies parts of the ranges of T. e. terrestris and T. e. hammondii. For comparisons with aquaticus and terrestris, see sections dealing with these forms. In geographically overlapping atratus and hammondii color differences very distinct: dorsal stripe in atratus broad and brightly colored, in hammondii absent or confined to neck region; dorsal ground color black or olive drab in atratus, brown or olive gray in hammondii; dorsolateral blotches distinct and well represented in hammondii, obscure in atratus. Hammondii lacks lemon-yellow throat characteristic of atratus. Both races have pointed internasals longer than wide, a character common throughout the aquatic group. Sixth and seventh supralabials relatively large and taller than long in atratus, longer than tall in hammondii. Nineteen and 15 scale rows at thoracic region and posterior end of body, respectively, characteristic of atratus; 21 and 17 characteristic of hammondii. In hammondii, average numbers of gastrosteges and urosteges higher than in atratus. In hammondii, preoculars frequently divided and eyes large; in atratus, preoculars rarely divided, diameter of eye small (Fox 1951: 490) |
| Comment | Rossman and Stewart (1987) recommended against recognizing T. a. aquaticus. RODRIGUEZ-ROBLES e al. 2003 stated that aquaticus is a Thamnophis a. atratus x T. a. hydrophilus intergrade. |
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