Atractus emmeli (BOETTGER, 1888)
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|Higher Taxa||Colubridae (Dipsadinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)|
|Common Names||E: Emmel's Ground Snake|
Boettger's Ground Snake [boettgeri]
|Synonym||Geophis emmeli BOETTGER 1888: 192|
Atractus emmeli — BOULENGER 1894: 311
Atractus boettgeri BOULENGER 1896: 645
Atractus balzani BOULENGER 1898: 129
Atractus taeniatus GRIFFIN 1916: 173
Atractus emmeli — SCHMIDT & WALKER 1943
Atractus balzani — PETERS et al. 1970: 27
Atractus taeniatus — PETERS & OREJAS-MIRANDA 1970: 35
Atractus boettgeri — MCCOY 1971 (part.)
Atractus boettgeri — DA CUNHA & DO NASCIMENTO 1983: 122
Atractus paravertebralis HENLE & EHRL 1991
Atractus taeniatus — CEI 1993
Atractus occipitoalbus — FUGLER & CABOT 1995:45
Atractus taeniatus — PASSOS et al. 2005
Atractus emmeli — PASSOS & FERNANDES 2008
Atractus paravertebralis — BÖHME 2010
Atractus occipitoalbus — QUINTERO-MUÑOZ 2013: 76
Atractus balzani — WALLACH et al. 2014: 69
Atractus emmeli — WALLACH et al. 2014: 72
Atractus paravertebralis — WALLACH et al. 2014: 79
Atractus boettgeri — WALLACH et al. 2014: 69
Atractus taeniatus — WALLACH et al. 2014: 81
Atractus emmeli — PASSOS et al. 2019: 10
Atractus emmeli — NOGUEIRA et al. 2019
|Distribution||Bolivia (Beni, Santa Cru), Peru (Cusco, Junin, Loreto, Ucayali)|
Type locality: Río Mapiri, Dep. de La Paz, Bolivia
balzani: NW Bolivia (La Paz); Type locality: Missiones Mosetenes, NW Bolivia [15°47’S, 66°58’W, ca. 517 m elevation]
boettgeri: Bolivia (Cochabamba); Type locality: Yungas, Sierra de las Yungas, Dep. de Cochabamba, Bolivia
paravertebralis: S Peru; Type locality: “Peru; Departamento Madre de Dios; Baja Tambopata; in Sekundärwald” [= Río Tambopata, Madre de Dios Department, SE Peru, ca. 12°53’S, 69°25’W, elevation 225 m].
taeniatus: Bolivia (Santa Cruz), Brazil (Rio Grande do Sul, Paraná [HR 27: 216], Mato Grosso), Argentina (Entre Rios, Misiones, Corrientes ?); Type locality: Santa Cruz de la Sierra, Departamento de Santa Cruz, Bolivia.
|Types||Lectotype: SMF 19364 (designated by Mertens 1967) |
Holotype: MSNG 28873, a 400 mm specimen (L. Balzan, 1892) [balzani]
Holotype: BMNH 19220.127.116.11 [boettgeri]
Holotype: ZFMK 39705, no paratype [paravertebralis]
Holotype: CM 117, a 218 mm male (J. Steinbach) [taeniatus]
|Diagnosis||Diagnosis (emmeli). Atractus emmeli can be distinguished from all congeners by the following combination of characters: (1) smooth dorsal scale rows usually 15/15/15, lacking apical pits; (2) postoculars two; (3) loreal moderately long; (4) temporal formula 1þ2; (5) supralabials six to seven, third and fourth contacting orbit; (6) infralabials usually seven, first four scales in contact with chin shields; (7) maxillary teeth six to eight with posterior-most two teeth reduced in size; (8) gular scales in four series; (9) usually four preventrals; (10) ventrals in females 154–187, in males 147–169; (11) subcaudals in females 14–25, in males 20–31; (12) after preservation, dorsum of body light to dark brown or uniformly black, frequently with a broad white to pale brown parietal band most conspicuous in immature specimens, and occasionally (in the cases of lighter ground color) with irregular black blotches on paravertebral region; (13) after preservation, ventral surface of body and tail cream, usually heavily covered with variable black dots or spots, longitudinally along the midline of each ventral, laterally restricted to the anterior margins of each scale, irregularly distributed on venter or almost entirely darkening the belly and tail; (14) body size moderate, females reaching 382 mm, males reaching 304 mm SVL; (15) tail short in females (5.7– 9.6% SVL), moderately long in males (9.2–14.7% SVL); (16) hemipenis moderately bilobed, semicapitated, and semicalyculated [from Passos et al. 2019: 11].|
Comparisons. Among all congeners, Atractus emmeli shares only with A. albuquerquei Cunha and Nascimento 1983, A. caete Passos, Fernandes, Be ́rnils and Moura-Leite 2010 and A. reticulatus the following combination of morphological characters: smooth dorsal scale rows 15/15/15; frontal shield broader than long; nostril longer than prenasal; maxillary bone with a well-developed lateral process and no projection at the level of the last teeth; maxillary teeth 6–8; hemipenis moderately bilobed, semicapitate, and semicalyculate; and dorsal ground color brown to uniformly black (see Discussion). Atractus emmeli differs from A. albuquerquei and A. reticulatus by usually having a conspicuous pale parietal band, belly frequently heavily pigmented with black marks, usually seven upper and lower labial scales, absence of naked pocket on the hemipenis, and 154–187 ventrals in females and 147–169 in males, 14–25 subcaudals in females and 20–31 in males (vs. absence of parietal band, venter frequently uniformly cream, usually six upper and lower labial scales, presence of naked pocket on the proximal region of hemipenis, and 192–211 ventrals in females and 170–184 in males, 27–38 subcaudals in females and 37–44 in males of A. albuquerquei; and venter uniformly cream, infralabials, 27–38 subcaudals in females and 37–44 in males of A. reticulatus). Atractus emmeli differs from A. caete by having four gular scale rows and conspicuous parietal band (vs. three gular scale rows and absence of parietal band).
Atractus emmeli also differs from the Amazonian species A. occipitoalbus, with which it was previously confused (see Remarks), by having nostril usually longer than prenasal, six to seven suparalabials, two postoculars, tail in females 5.7– 9.4% SVL in males, 9.2–14.7% SVL, hemipenis with capitular groove barely defined on the asulcate side (vs. nostril shorter than prenasal, usually eight supralabials, usually single postocular in females, tail with 4.4–6.9% SVL in females and 9.6–14.1% in males, and hemipenis with capitular groove indistinct on the asulcate side of hemipenis). Atractus emmeli differs from all valid congeners with vouchered records in Bolivia (i.e., A. bocki Werner 1909, A. latifrons Gu ̈nther 1868, A. major Boulenger 1893, A. snethlageae Cunha and Nacimento 1983, and A. torquatus Dume ́ril, Bibron, and Dumeril 1854) by having usually 15/ 15/15 dorsal scale rows and dorsal ground color brown to uniformly black (vs. 17/17/17 and coloration variable but never brown to uniformly black) [from Passos et al. 2019: 12].
Description (balzani): snout-vent length (SVL, hereafter) 354 mm; midbody diameter 8.4 mm (2.37% SVL); tail length 51 mm (14.4% SVL); head length 11.3 mm (3.19% SVL); head width 6.91 mm (61.1% head length). Head arched in lateral view; snout rounded in dorsal view; canthus rostralis poorly defined. Interocular distance 4.3 mm; snout-orbit distance 4.0 mm; rostral 1.2 mm high, 2.1 mm wide, visible in dorsal view; internasal 1.9 mm long, 0.9 mm wide, internasal suture sinistral with respect to prefrontal suture; prefrontal 3.2 mm long, 2.1 mm wide; supraocular subtrapezoidal, 1.2 mm long, 1.0 mm wide; frontal subpentagonal, 2.8 mm long, 3.1 mm wide; parietal 4.7 mm long, 2.9 mm wide; nasal divided, nostril restricted to anterior nasal; anterior nasal 0.65 mm long, 0.95 mm high; posterior nasal 1.1 mm long, 1.1 mm high; loreal long (2.3 mm long, 0.7 mm high); second and third supralabials contacting loreal; eye diameter 1.5 mm; pupil rounded; one small postocular (0.4 mm long, 1.2 mm high); temporals 1+2; anterior temporal 2.1 mm long, 1.1 mm high; anterior temporal in contact with parietal, postocular, and fourth–fifth supralabials; lower posterior temporal longer than upper posterior temporal; upper posterior temporal 2.0 mm long, 1.0 mm high; lower posterior temporal 2.4 mm long, 1.0 mm high; supralabials 6/6, third–fourth with orbit; second supralabial higher than first supralabial, and similar in size to third and fourth; fifth supralabial higher and sixth longer than remaining supralabials; symphysial damaged; infralabials 7 (right side) and damage in the right side, first four infralabials contacting chinshields; chinshields 1.9 mm long, 1.3 mm wide; ventrals 164; subcaudals 32; dorsal scale smooth in 14/17/16 rows; maxillary teeth 6/6. Dorsum of head dark brown; dorsal ground color of body reticulate dark brown, except for the first dorsal scale row mostly pale brown; dorsal scales with the center of each scale lighter (pale brown) and edges darker (dark brown); belly cream with few dispersed, small brown dots along body; dots concentrated on the lateral portion of ventral scales anteriorly to midbody; small brown dots on the posterior third of the body; tail creamish white heavily pigmented with dark brown spots on its ventral surface with yellowish cream background (Fig. 1A).
Passos et al. 2018 performed detailed comparisons between the holotype of A. balzani (Fig. 1; Table 1) and two species reported as occurring in the Yungas region of Bolivia, Atractus emmeli (Boettger 1888) and A. major Boulenger 1894 (Boulenger 1896: 645; Fig. 3). We can distinguish A. balzani from A. major by having an inconspicuous canthus rostralis, six supralabials, and the first four infralabials contacting chinshields (vs. very conspicuous canthus rostralis, seven supralabials, and first three infralabials contacting chinshields). By contrast, there is no feature in external morphology that unequivocally distinguishes A. balzani from A. emmeli, and Boulenger (1898) based his description of A. balzani mainly on its general color pattern, the presence of one postocular and 17 dorsal scales rows (supposedly counted on the midbody). Although inconsistent in the A. emmeli populations, all these features are polymorphic certainly in the Bolivian and Peruvian samples (Figs. 1–2; Table 1). In addition, the taxonomy of the Atractus emmeli complex was recently reassessed through an integrated approach (P. Passos et al. in prep.), with a considerable increase of the phenotypic variability range previously reported for the nominal species (e.g., McCoy 1971; Salazar-Bravo et al. 2010). Nonetheless, in the aforementioned studies, the authors were not able to examine the holotype of A. balzani, but now, with new data made available from its holotype, it is possible to infer the taxonomic status of the species. The only apparent difference distinguishing both species is the number of dorsal scale rows at midbody, being 15 in A. emmeli and 17 in A. balzani. However, Peters & Orejas-Miranda (1970: 25) reported one individual female of A. emmeli—from an unknown origin—with 17 dorsal scale rows, seven supralabials, two postoculars, 188 ventrals and 22 subcaudals. Additionally, we also corroborated the presence of polymorphic dorsal scale rows counts in A. emmeli based on two other specimens from Peru (MUSM 2313 provenance unknown and MUSM 27402 from Trompeteros, department of Loreto), which retained 17/17/17 and 15/17/17 dorsal scales, respectively. The A. balzani holotype is also polymorphic with respect to its dorsal scale rows, displaying 14/17/16. In addition, the differences in color pattern between the A. balzani holotype, the lectotype of A. emmeli (Fig. 1) and additional specimens of A. emmeli from Bolivia, being the pale occipital band, a dorsum which is uniformly black and belly which is almost fully cream are also polymorphic in the Bolivian populations of A. emmeli (Fig. 2). Thus, it is not possible to distinguish both species based on any of the traits mentioned above, and they conclude that the best taxonomic decision to be made at this time is to place A. balzani in the synonymy of A. emmeli.
|Comment||Synonymy: mostly after Passos et al. 2019. Passos et al. 2018 synonymized A. balzani with A. emmeli. Passos et al. 2019 synonymized A. boettgeri, A. paravertebralis, and A. taeniatus with A. emmeli based on quantitative (meristics and morphometrics) and qualitative (pholidosis, color pattern, and hemipenis) analyses of morphological characters, in combination with ecological niche modeling and niche overlapping.|
Abundance: Boulenger (1898) described A. balzani based on a single specimen and no other specimens have been collected since then (Passos et al. 2018).
|Etymology||Named after Ferdinand Emmel sent two specimens of this snake to Naturmuseum Senckenberg, Frankfurt.|
A. boettgeri was named after Oskar Boettger (1844-1910), herpetologist at the Senckenberg Museum in Frankfurt am Main.
A. balzani was named after Dr. Luigi Balzan (1865-1893), an Italian naturalist and collector of the holotype.
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