rediscovery of atractus microrhynchus of the …

Herpetologica, 68(3), 2012, 375–392� 2012 by The Herpetologists’ League, Inc.

REDISCOVERY OF ATRACTUS MICRORHYNCHUS AND REAPPRAISALOF THE TAXONOMIC STATUS OF A. EMERSONI AND A. NATANS

(SERPENTES: DIPSADIDAE)

PAULO PASSOS1,5, DIEGO CISNEROS-HEREDIA

2, DANI ENRIQUE RIVERA3, CESAR AGUILAR

3,AND WALTER E. SCHARGEL

4

1Departamento de Vertebrados, Museu Nacional, Universidade Federal do Rio de Janeiro, Quinta da Boa Vista,Rio de Janeiro, RJ, 20940-040, Brazil

2Universidad San Francisco de Quito, College of Biological and Environmental Sciences, Avenida Interoceanica,Campus Cumbaya, Edifıcio Darwin, of. DW010A, Casilla Postal 17-12-841, Quito, Ecuador

3Departamento de Herpetologia, Museo de Historia Natural, Universidad Mayor de San Marcos, Avenida Arenales 1256,Jesus Maria, Apartado 14-0434, Lima, Peru

4Department of Biology, The University of Texas at Arlington, Arlington, TX 76019, USA

ABSTRACT: The species Rhabdosoma microrhynchum (now Atractus microrhynchus) was originallydescribed based on a single specimen collected by the Orton Expedition at ‘‘Guayaquil,’’ in the Guayasprovince on the Pacific coast of Ecuador. The holotype is currently lost and all specimens previously referredto this species were misidentified on the basis of material from Peruvian Amazonia. While examining museumcollections and conducting fieldwork in the Pacific lowlands of Ecuador and Peru, we found specimensassignable to A. microrhynchus. In this study, we report the morphological variation in these new specimensof A. microrhynchus and evaluate the taxonomic status of the Amazonian species previously confused with it.We restrict the concept of A. microrhynchus to the Pacific lowland populations from Ecuador and Peru, andwe designate a neotype for the species. Based on the examination of the types of A. emersoni and A. natansfrom Amazonia, we found that there is wide overlap in the internal and external characters of both taxa.Therefore, A. emersoni is relegated to the synonymy of A. natans. Furthermore, we compared A.microrhynchus with all congeners and discuss its affinities with the A. multicinctus species group based onshared, exclusive hemipenial features.

RESUMEN: La especie Rhabdosoma microrhynchum (ahora Atractus microrhynchus) se baso en un soloespecimen colectado por la Expedicion Orton en ‘‘Guayaquil,’’ provincia de Guayas, costa Pacıfica delEcuador. El holotipo esta actualmente perdido y todos los especımenes previamente referidos a esta especiefueron identificados erroneamente sobre la base de material de la Amazonıa Peruana. Durante la revision decolecciones de museos y la realizacion de trabajo de campo en las tierras bajas del Pacıfico de Ecuador yPeru, encontramos especımenes que se pueden asignar a A. microrhynchus. En este estudio, reportamossobre la variacion morfologica de estos nuevos especımenes de A. microrhynchus y evaluamos el estadotaxonomico de las especies Amazonicas previamente confundidas con esta. Restringimos el concepto de A.microrhynchus para las poblaciones de las tierras bajas del Pacıfico de Ecuador y Peru y designamos unneotipo para la especie. Basados en la revision de los tipos de A. emersoni y A. natans de la Amazonıa,encontramos que hay una amplia superposicion de las caracterısticas de ambos taxones. Por lo tanto, A.emersoni se coloca bajo la sinonımia de A. natans. Mas aun, comparamos A. microrhynchus con todos suscongeners y sus afinidades con el grupo-de-especies A. multicinctus son discutidos sobre la base de lascaracterısticas hemipenianas exclusivas compartidas.

Key words: Amazonia; Atractus multicinctus species group; Hemipenial features; Morphologicalvariation; Pacific lowlands; Species boundaries

THE DIPSADINE snake genus Atractus Wa-gler 1828, comprises small- to moderate-sizedsnakes that have secretive lifestyles and feedon earthworms, arthropods, and molluscs(Passos et al., 2010c). The genus is widelydistributed in the Neotropics from Panama toArgentina (Giraudo and Scrocchi, 2000;Myers, 2003); it occurs primarily on the

mainland from sea level to 4500-m elevationand occupies almost all South Americanbiomes (Passos et al., 2010c). Atractus is ahighly diverse genus that is closely related toAdelphicos Jan, 1862 and Geophis Wagler,1830 (Savage, 1960; Downs, 1967; Fernandes,1995; Zaher, 1999; Passos, 2008), comprisingapproximately 130 valid species, most of themknown to date only from their proper typespecimens (Passos and Fernandes, 2008;Prudente and Passos, 2008; Passos et al.,5 CORRESPONDENCE: e-mail, [email protected]

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2009b,c,d,e). Although many currently recog-nized species remain poorly evaluated, muchof our understanding of the taxonomy ofAtractus has been considerably improved inthe past 5 yr (Cisneros-Heredia, 2005; Passoset al., 2005; Zaher et al., 2005; Kok, 2006;Myers and Schargel, 2006; Prudente andSantos-Costa, 2006; Kok et al., 2007; Passoset al., 2007a,b; Passos and Fernandes, 2008;Prudente and Passos, 2008; Passos andArredondo, 2009; Passos et al., 2009a,b,c,d,e,2010a,c; Prudente and Passos, 2010). Even so,additional efforts must be made to addressproblems of morphological variation, geo-graphic ranges, sexual dimorphism, polymor-phism, and ontogenetic change of colorationfor many taxa or species complexes thatremain problematic (Passos et al., 2010a). Inthis sense, only by addressing all of theseaspects and, at the same time, rigorouslycomparing newly obtained samples with thelarge number of available names in theliterature can we clarify the species boundar-ies of this complex and poorly understoodgenus (Passos and Lynch, 2010).

Rhabdosoma microrhynchum (Cope, 1868)was described based on a single individualcollected by the Orton Expedition at Guaya-quil in the Pacific lowlands of Ecuador. Cope(1868), in the original description, suggestedthat this species was closely related to Atractusbadius (Boie, 1827). Subsequently, Cope(1870) reported R. microrhynchum fromPebas in the Peruvian Amazonia on the basisof new material from the same expedition.Boulenger (1894) redefined the genus Atrac-tus and proposed the synonymization of R.microrhynchum with A. badius. Savage(1960), although resurrecting A. microrhyn-chus, considered that the taxonomic status ofthis species could not be accurately assessedbecause the original description was brief andthe holotype was apparently lost. Savage(1960) also suggested the possibility that thetype locality could be wrongly labeled giventhat the Orton Expedition collected materialon both sides of the Andes and that noadditional specimens referable to A. micro-rhynchus had been collected in Guayaquil.Dixon and Soini (1977) proposed once againthe synonymy of A. microrhynchus with A.badius based on specimens from the Iquitos

region in Peru. Hoogmoed (1980) designatedthe lectotype of A. badius and did notconsider A. microrhynchus as a propersynonym of the latter species, restricting thedistribution of A. badius to the Guayanaregion. In light of the new definition of A.badius, Dixon and Soini (1986) reconsideredthe taxonomic status of their Iquitos speci-mens as Atractus cf. microrhynchus. In spiteof Hoogmoed’s work, some authors stillconsider A. badius to be a widespread taxondistributed in Amazonian and Andean regionsof Colombia and Peru (Perez-Santos andMoreno, 1988; Carrillo and Icochea, 1995)or even the junior synonyms (A. subbicinctus[Jan, 1862] and A. micheli Mocquard, 1904) tobe valid species (Claessen, 2002, 2003).

Hoogmoed and Prudente (2003) describedA. natans on the basis of three individualsfrom extreme (west and east) portions ofBrazilian Amazonia (Uarini approximately1000 km east of Melgaco), but restricted theircomparisons to species distributed in CentralAmazonia and the Guiana Shield. Subse-quently, Silva (2004) described A. emersonibased on two specimens from BenjaminConstant in Brazil, and another individualfrom Leticia in Colombia, near the borderbetween Brazil and Peru. Despite the geo-graphic proximity of the type locality of A.emersoni to Iquitos (approximately 360 km byair), the author did not compare their putativenew taxon with Atractus cf. microrhynchus(sensu Dixon and Soini, 1986). Recently,Passos et al. (2009e) revised the taxonomicstatus of Pacific lowland species of Atractusand recognized 10 species distributed fromColombia to Ecuador. In that paper, theauthors recognized A. microrhynchus as validspecies and mentioned newly discoveredmaterial of the species apparently collectednear the type locality in Ecuador. AlthoughPassos et al. (2009e) pointed out that thespecimens examined by Dixon and Soini(1977, 1986) actually refer to A. natans bymistake, they cited both studies on thesynonymy list of A. microrhynchus. Therefore,the inclusion of such references in the list ofsynonymy of A. microrhynchus must beinterpreted as an error rather than anambiguity with respect to the status of thespecimens of the Iquitos Region.

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We redescribe A. microrhynchus based onnew specimens discovered in collections andin the wild. We report on the meristic,morphometric, hemipenial, and color-patterncharacters, and we propose a neotype for thespecies. In addition, we evaluate the taxonom-ic status of the Amazonian species that werepreviously confused with A. microrhynchus,and we discuss the affinities of A. micro-rhynchus on the basis of morphologicalcharacters.

MATERIALS AND METHODS

We examined specimens in the followinginstitutions: Brazil—Museu Paraense EmılioGoeldi (MPEG), Belem; Colombia—Institutode Ciencias Naturales (ICN), UniversidadNacional de Colombia, Bogota; Ecuador—Division de Herpetologıa del Museo Ecuator-iano de Ciencias Naturales (DHMECN),Quito; Peru—Museo de Historia Natural dela Universidad Mayor de San Marcos(MUSM), Lima; and United States—Ameri-can Museum of Natural History (AMNH),New York; National Museum of NaturalHistory (USNM), Smithsonian Institution,Washington DC; Texas Cooperative WildlifeCollections (TCWC), Texas A&M University,College Station. Geographic coordinates(based on the datum WSG84) of localitieswere recorded in the field, obtained frommuseum databases, or taken from geograph-ical gazetteers (Stephens and Traylor, 1983;Paynter and Traylor, 1991). Whenever possi-ble, we refined the coordinates obtained fromliterature with aid of the software GoogleEarth 6.2.

Characters used are based on meristics,morphometrics, maxillary dentition, and hem-ipenis morphology. Terminology for Atractuscephalic shields follows Savage (1960), where-as the method of counting ventral scalesfollows Dowling (1951). Terminology used todescribe the condition of the loreal scalefollows Passos et al. (2007b). We tookmeasurements with dial calipers to the nearest0.1 mm under an optical stereoscope, exceptfor snout–vent (SVL) and caudal lengths (CL);SVL and CL were measured with a flexibleruler to the nearest millimeter. The terminol-ogy for body and tail size follows Passos et al.(2009e). We took measurements for paired

cephalic shields only on the right side of thehead. Terminology for hemipenis descriptionsfollows Dowling and Savage (1960) and Zaher(1999). Techniques for hemipenis eversion ofpreserved specimens follow Pesantes (1994).Although all hemipenes have been completelyeverted, some of them are not fully inflated, asis common with preserved organs (Myers andCadle, 2003). We examined maxillae in situthrough a narrow lateromedial incision be-tween supralabials and the maxillary arch. Weremoved tissues covering the maxillary arch,and we counted teeth as well as emptysockets. Terminology for teeth and maxillaryconditions follow Passos et al. (2009e). Addi-tional specimens of Atractus examined arelisted in Passos et al. (2005; 2007a,b;2009b,c,d,e; 2010a,b,c), Passos and Arredondo(2009), Passos and Fernandes (2008), Passosand Lynch (2010), Prudente and Passos (2008,2010).

RESULTS

Atractus microrhynchus (Cope, 1868)(Figs. 1–3)

Rhabdosoma microrhynchum Cope, 1868;Proc. Acad. Nat. Sci. Philadelphia 1868:102.

Atractus badius Boulenger, 1894; Catalogueof the Snakes in the British Museum vol.2:308. (in part).

Atractus microrhynchus Savage, 1960;Misc. Publ. Mus. Zool. Univ. Michigan 112:2.

Atractus microrhynchus Passos et al.,2009e; Zootaxa 2293:19.

Holotype.—Unknown sex, California Acad-emy of Sciences (CAS 6693), from Guayaquil(028100S, 798540W, ca. 50 m above sea level[asl]), Guayas Province, Ecuador, collected bythe Orton Expedition in 1867–1868. Savage(1960) pointed out that the holotype wasmissing at the CAS, and it currently remainslost (N. Gilmore, personal observation).

Neotype.—Adult male, DHMECN 3008,collected March 2005 by Francisco Sornozaat Reserva Biologica Buenaventura (03838055 00

S, 79845050 00W, ca. 600 m asl), ParroquiaPinas, Canton Pinas, El Oro Province, Ecua-dor (by current designation; see Remarks).

Referred Specimens.—Juvenile male,AMNH 108943, collected April 1972 by RheaWarren at Rıo Palenque, 50 km N of Quevedo

September 2012] 377HERPETOLOGICA

(018020S, 798270W, ca. 110 m asl), Los RıosProvince, Ecuador. Adult males, MUSM22829–30, collected 5–10 May 2005 byRichard Cadenillas at Campo verde, Cerrosde Amotape National Park (between03850 023 00 S, 80809 059 00W, 799 m asl and03850044 00S, 80811011 00W, 570 m asl), Tumbesregion, Peru.

Diagnosis.—Atractus microrhynchus is dis-tinguished from all congeners by the followingcombination of characters: (1) 17-17-17smooth dorsal scale rows; (2) two postoculars;(3) long loreal; (4) temporals 1þ2; (5) sevensupralabials, third and fourth contacting orbit;(6) seven infralabials, first three contacting

chinshields; (7) six to seven maxillary teeth; (8)three gular scale rows; (9) three preventrals;(10) 143–150 ventrals in males; (11) 32–35subcaudals in males; (12) dorsum brown tolight reddish brown, occasionally with pairedirregular white-bordered black blotches; (13)ventral ground color cream, heavily markedwith dark-brown dots, forming an irregularlyblotched belly; (14) small body size in males(reaching 293 mm SVL); (15) long tail inmales (18–18.1% of SVL); and (16) hemipenisstrongly bilobed, barely semicapitate, andsemicalyculate.

Comparisons.—Among all congeners, A.microrhynchus shares a strongly bilobedhemipenis with lobes of equivalent size orlonger than hemipenial body, sulcus sperma-ticus bifurcating on the basal region of theorgan, and intrasulcar region with enlarged,narrow hooked spines exclusively as withmembers of the A. multicinctus (Jan, in Janand Sordelli, 1865) species group (sensuPassos et al., 2009e). Atractus microrhynchusdiffers from all of them by having a stronglypigmented venter, with dark brown dotsirregularly distributed throughout (vs. ventercreamish white with dark spots, when present,only on posterior region of body). On the basisof external characters, A. microrhynchusshares a reddish brown to reddish light browndorsal ground color only with A. dunniSavage, 1955; A. echidna Passos, et al., 2009;A. ecuadoriensis Savage, 1955; A. iridescensPeracca, 1896; A. lasallei Amaral, 1931; A.lehmanni Boettger, 1898; A. loveridgei Ama-ral, 1930; and A. occidentalis Savage, 1955.Atractus microrhynchus differs from A. dun-ni, A. iridescens, and A. occidentalis in having143–150 ventrals in males, a single postdias-temal tooth, and a strongly bilobed andslightly semicapitate hemipenis, with fourenlarged hooked spines arranged in longitu-dinal series above the sulcus spermaticusbifurcation (vs. 131–143 ventrals in A. occi-dentalis; 128–144 in A. dunni, and 135–143 A.iridescens; two postdiastemal teeth in thethree species; a moderately bilobed and non-calyculate hemipenis with lateral projectionon the basal region of hemipenial body in A.iridescens, hemipenis having a thick intra-sulcar region with ca. 15 enlarged hookedspines disposed on transversal [2/3/4/3/2]

FIG. 1.—Dorsal (A) and ventral (B) views of theneotype of Atractus microrhynchus (DHMECN 3008),from Reserva Biologica Buenaventura, El Oro Province,Ecuador.


series in A. dunni and A. occidentalis); from A.echidna in having 17 dorsal scale rows (vs. 15);from A. ecuadoriensis in having venter heavilymarked with brown dots and six or sevenmaxillary teeth (vs. uniformly creamish whiteventer and eight maxillary teeth); from A.lasallei, A. lehmanni, and A. loveridgei inhaving 32–35 subcaudals in males, five or sixprediastemal teeth with a single postdiastemaltooth, and hemipenis strongly bilobed (vs. 20–27 in A. lasallei, 23–29 in A. lehmanni, and24–27 in A. loveridgei; seven to nine teethwith two postdiastemal teeth; hemipenismoderately bilobed). Other than differencesin color pattern (see above), A. microrhynchusdiffers from A. natans in having 32–34subcaudals in males, three infralabials con-tacting chinshields, six or seven (5þ1 or rarely6þ1) maxillary teeth, long tails in males, andhemipenis strongly bilobed with distinct

moderately hooked spines on the intrasulcarregion of the capitulum (vs. 23–31 subcaudalsin males, four infralabials contacting chin-shields, usually seven maxillary teeth [5þ2],moderate tail size in males, and hemipenismoderately bilobed lacking hooked spines onintrasulcar region).

Description of Neotype.—Adult male, 275mm SVL, 54 mm CL (19.6% of SVL); headrounded in dorsal view, flattened in lateralview, 10.2 mm long (3.7% of SVL), 6.6 mmwide; head not distinct from body; snoutrounded in dorsal view, fairly truncated inlateral view; rostrum–orbit distance 4.1 mm(40.2% of head length); nostril–orbit distance2.4 mm (23.5% of head length); intra-orbitaldistance 4.2 mm (63.6% of head width); bodysubcylindrical, body diameter 8.4 mm (3.1%of SVL); belly flattened; tail moderately long,with terminal spine rhomboid, slightly acumi-

FIG. 2.—Dorsal (left) and ventral (right) views of the Peruvian specimens of Atractus microrhynchus (A) MUSM22829 and (B) MSUM 22830.


nate, and conical; rostral subtriangular, wider(1.8 mm) than high (1.3 mm), visible fromabove; internasal longer (1.0 mm) than wide(0.8 mm wide); internasal suture sinistralregarding prefrontal median suture; prefrontallonger (2.5 mm) than wide (2.3 mm); frontaltriangular, approximately as wide (2.5 mm) aslong; supraocular irregularly trapezoidal, lon-ger (1.4 mm) than wide (1.1 mm); parietalapproximately twice as long (4.4 mm) as wide(2.6 mm); nasal divided; prenasal approxi-mately twice as high (0.7 mm) as long,contacting rostral, internasal, first supralabial,and postnasal; postnasal approximately twiceas high (1.0 mm) as long (0.5 mm), contactingprenasal, prefrontals, loreal, and second pairof supralabials; moderately long loreal (2.3mm long and 0.9 mm high); loreal contactingeyes, prefrontals, nasals, and second to thirdsupralabials; eye diameter 1.1 mm; pupilround; two postoculars, upper postocularpentagonal and slightly higher (0.8 mm) than

lower postocular, contacting eye, supraocular,parietal and anterior temporal, lower post-ocular slightly longer (0.7 mm) than upper,contacting eye, fourth and fifth supralabialand anterior temporal; 1þ2 temporals; anteri-or temporal longer (1.5 mm) than high (0.9mm), contacting parietal, fifth to sixth supra-labials, postoculars, and posterior temporals;upper posterior temporal elongate (3.4 mmlong), approximately four times longer thanwide; lower posterior temporals not fused andsimilar in size and shape to anterior temporal;seven supralabials, third and fourth contactingorbit; second supralabial higher than first andlower than third; sixth supralabial higher andseventh supralabial longer than remainingsupralabials; symphisial triangular, approxi-mately twice wider (1.3 mm) than long (0.4mm); seven infralabials, first three pairscontacting chinshields; first pair of infralabialsin contact behind symphisial, preventingsymphisial/chinshield contact; chinshields ap-proximately four times as long (3.6 mm) aswide (1.2 mm); 17-17-17 smooth dorsal scalesrows, lacking apical pits and supra-analtubercles; three gular scale rows between lastsupralabial and preventral; three preventralscales; 147 ventral scales; anal plate single; 36subcaudal scales. Maxilla arched in dorsalview, curved on anterior and flattened onmedian to posterior portion; maxillary archwith six prediastemal and single postdiastemalteeth; prediastemal teeth angular in crosssection, robust at base, narrower at apices,curved posteriorly; first five teeth large,moderately spaced, similar in size; sixthprediastemal tooth reduced in size; maxillarydiastema moderate, with space shorter thandistance between fifth and sixth teeth; post-diastemal tooth slightly smaller than sixthprediastemal one; lateral process of maxillapoorly developed.

Coloration in Preservative of Neotype.—Dorsum of head uniform brown to posteriorregion of parietals; latero-posterior portion ofparietals and temporal region pale brown,forming a barely distinct incomplete lightband; head background brown to dorsalmargin of supralabials, except for pale brownspots on temporal region; anterior temporalwith pale brown spots; lower posterior tem-poral and posterior portion of seventh supra-

FIG. 3.—Dorsal (A), lateral (B), and ventral (C) views ofhead of the Atractus microrhynchus (MUSM 22829).


labial creamy, constituting dorsal limits ofdark postorbital stripe; supralabials mostlycreamy, with invasion of brown pigment onposterior suture between scales; brown post-orbital stripe crossing posterior region of sixthand mid portion of seventh supralabial,forming the descending portion of stripe;infralabials mostly creamy with brown dotstoward the center or posterior edges of somescales; mental region creamy with few browndots on anterior portion of chinshields; gularseries and preventrals with small irregularbrown marks; ventral ground color creamyscattered with dark brown marks; first 40ventrals predominantly creamy with fewbrown irregular dots disposed toward the sideof the scales; after that point dots concentrat-ed laterally forming irregular brown blotcheson lateral region of ventral scales, except forlateral-most edge of ventrals creamy; browndots concentrated toward posterior region ofbody; creamy paraventral margin evidentalong all of body; ventral surface of tail darkbrown suffused with few creamy dots concen-trated on margins of subcaudals. Dorsalground color light brown with 44 well-definedpaired dark brown blotches (one scale long);blotches with indistinct creamy borders anddisposed almost linearly on each side ofparavertebral region, extending from fourthto fifth or fifth to sixth dorsal scale rows; firstdorsal scale rows with invasion of creamypigment on each side of body (Fig. 1).

Color Variation.—The color pattern of theother Ecuadorian specimen is highly similar tothat of the neotype, except that the lowestdorsal blotches are closer to each other, atsome points forming a discrete lateral brokenline; also the posterior half of the venter isdarker, becoming almost completely darkbrown because of the accumulation of darkdots; and the ventral surface of tail iscompletely dark brown. Peruvian specimensof A. microrhynchus are similar to theneotype, with MUSM 22829 differing from itin the following aspects: distinct occipital lightband, with entire lateral portion of parietalsand first dorsal series pale brown; dark browndescending stripe and brown marks betweensupralabials and infralabials sutures moreconspicuous; first 30 ventral scales morescattered with brown dots; creamy paraventral

margin evident along all of body; posteriorregion of venter with more invasion of creamyblotches; creamy pigment on ventral surfaceof tail reaching median subcaudal sutures;dorsum with 44/46 (right and left sides,respectively) well-defined paired black blotch-es (two to three scales long and one to threescales high); blotches well spaced in the firsthalf of body (interspaces three to four scaleslong) and next to each other (interspaces oneto two scales long) in the posterior region;blotches pale brown bordered (half to onescale wide), covering five to seven dorsal scalerows (Figs. 2 and 3).

Hemipenial Variation.—Retracted organbifurcates at eighth and extends to the levelof 15th subcaudal. Hemipenis strongly bi-lobed, slightly semicapitate, and semicalycu-late; lobes clearly distinct from capitulum andlonger than hemipenial body on sulcate andsimilar in size to it on asulcate side; lobesattenuate, centrifugally oriented, with round-ed apices; left lobe longer than right; lobescovered with moderate alary spines on basalportion and concentrated spinulate calycesfrom the base increasing toward apices oflobes; lobes of asulcate side of hemipenisforming barely defined longitudinal crests;capitular groove indistinct on sulcate, evidenton lateral region, and barely distinct onasulcate side of organ; capitulum locatedabove bifurcation of sulcus spermaticus;capitulum entirely retracted on asulcate sideof hemipenis and longer than hemipenialbody on sulcate side; capitulum with inverted‘‘V’’ shape on sulcate to asulcate side; intra-sulcar region of capitulum with four enlarged,narrow, hooked spines disposed in longitudi-nal series; nonlobular portion of capitulumwith spinulate calyces and moderate alaryspines; sulcus spermaticus bifurcates on basalportion of hemipenial body; after sulcusspermaticus division three large hookedspines, on each side of sulcus spermaticusramus, delimit the proximal margin of capit-ular crotch; branches of sulcus spermaticuscentrolinearly oriented, running to tips oflobes; sulcus spermaticus margins stout andmoderately expanded before lobes divisionand widely expanded along each lobe; sulcusspermaticus bordered with spinules frombasal portion of organ to lobular region;


asulcate side of organ with two large hookedspines just above division of lobes; four largehooked spines disposed in inverted ‘‘V’’ shapedelimit the capitulum border on asulcate tolateral side of hemipenis; hemipenial bodysubelliptical, uniformly covered with moder-ate hooked spines; basal naked pocket absent;basal portion of hemipenis uniformly coveredwith longitudinal plicae. The hemipenis ofMUSM 22830 is very similar to that of MUSM22829, differing from it in the followingaspects: lobes with similar length; eightenlarged, narrow, hooked spines on intra-sulcar region; large hooked spines borderingcapitulum on lateral and asulcate side of organrelatively smaller (Fig. 4).

Quantitative Variation.—Ecuadorian andPeruvian specimens have seven supralabials,third and fourth contacting orbit; seveninfralabials, first three contacting chinshields;three gular scale rows; three preventrals; twopostoculars; and 1þ2 temporals. Variationoccurs in the number of maxillary teeth; thesecond Ecuadorian specimen has 6þ1 maxil-lary teeth on its left side, like the neotype, butit has 5þ1 maxillary teeth on its right side,similar to the Peruvian specimens. Juvenilemale (AMNH 108943): 146 mm SVL, 57 mmTL; 143 ventrals, 35 subcaudals. Adult male(MUSM 22829): 293 mm SVL, 53 mm TL; tail

18.1% of SVL, 150 ventrals, 34 subcaudals,retracted hemipenis extends to the level of15th subcaudal. Adult male (MUSM 22830):288 mm SVL, 52 mm TL; tail 18% of SVL, 146ventrals, 32/33 subcaudals, retracted hemi-penis extends to the level of 13th subcaudal.

Distribution.—Pacific lowlands from centralwestern Ecuador to northwestern Peru.Known from three localities in Ecuador:Guayaquil, Guayas Province; Rıo Palenque,Los Rıos Province; and Buenaventura, El OroProvince; and one locality in Peru: Cerros deAmotape National Park, Tumbes region, Peru.Atractus microrhynchus is apparently endem-ic to Seasonal Evergreen Forests in the WestEcuadorian Region, where it is known tooccur between 0- and 800-m elevation (Fig.5). The West Ecuadorian Region is a biogeo-graphic zone recently defined for the highlySeasonal Evergreen Forests that extend alongthe Pacific lowlands and foothills of theAndean Cordillera Occidental in westernEcuador and extreme northwestern Peru.Previously considered just as a transition zonebetween the Chocoan and Tumbesian biogeo-graphic regions, recent studies have revealedthat several endemic species of animals andplants are restricted to this region (Cisneros-Heredia, 2006, 2007; Cisneros-Heredia andYanez-Munoz, 2007). The West Ecuadorian

FIG. 4.—Sulcate (left) and asulcate (right) sides of the hemipenis of the holotype of Atractus microrhynchus (A)MUSM 22829 and (B) MUSM 22830.


Region was originally thought to be confinedto western Ecuador (see Cisneros-Heredia,2006), but it also includes the small areareported as Equatorial Dry Forests by Brack(1986) in the Tumbes area. The original typelocality of A. microrhynchus was reported byCope (1868) as Guayaquil, which seems to becorrect. At the time of the Orton Expedition,the port city of Guayaquil was surrounded byhills covered with Seasonal Evergreen For-ests. Guayaquil is between Rıo Palenque (190km away) and Buenaventura (150 km away);both Rıo Palenque and Guayaquil are locatedin the Guayas–Daule–Babahoyo rivers basin.

Remarks.—Unfortunately, the holotype ofA. microrhynchus is lost. To complicatematters, the original description provided byCope (1868) was brief, without any illustrationof the holotype, and no additional species ofAtractus other than A. multicinctus and A.paucidens Despax, 1910 have been reportedon the Pacific lowlands of Ecuador (Savage,1960; Passos et al., 2009e). That Cope (1870),in a subsequent study, reported a supposedspecimen of A. microrhynchus from Pebas inPeruvian Amazonia suggests that a populationwith a color pattern similar to that of A.

microrhynchus occurs in the upper Amazonbasin. Regrettably, this specimen from Pebaswas never catalogued in the Academy ofNatural Sciences of Philadelphia and is alsocurrently lost (N. Gilmore, personal observa-tion). Dixon and Soini (1977, 1986) indicatedthat 50% of the specimens they referred to A.cf. microrhynchus exactly match Cope’s orig-inal description. In this matter we disagree,and we quote Cope’s description of colorationfor later comparisons: ‘‘Coloration like that ofTantilla Baird and Girard, 1853. Above darkbrown, beneath pale brown, with a faint linealong the margins of the gastrosteges. Top ofhead blackish, brown behind; a partiallycomplete yellow collar, which widens at theangle of the jaws. A deep brown band fromeye to angle of mouth; upper labials yellowbrown edged.’’

Passos et al. (2009e) pointed out that theoriginal description of A. microrhynchus isinadequate to distinguish it from manyAtractus that have 17 scale rows and auniform body color pattern. Cope’s mentionof a dark brown cephalic cap with anincomplete yellow collar, nearly uniformdorsum, and belly with lines on lateral region

FIG. 5.—Geographical distribution of Atractus microrhynchus. The solid square represents the original locality of theholotype of A. microrhynchus from Cope (1868), and the open square represents the current type locality of the A.microrhynchus. Triangles represent the additional records of A. microrhynchus.


of ventral scales led Passos et al. (2009e) tospeculate that A. microrhynchus was perhapsmorphologically similar to A. collaris Peracca,1897 and other apparently related species (butsee Prudente and Passos, 2008, 2010). How-ever, all of these features in the specimensfound in the Pacific lowlands of Ecuador andPeru are only superficially similar to A. collaris(sensu stricto). In fact, A. microrhynchus asdefined herein differs from A. collaris andtheir relatives in several aspects (e.g., inlacking apical pits and supra-anal tuberclesin males, incomplete and conspicuous occip-ital white band, conspicuous lateral blackstripes on lateral portion of belly and distinctpostorbital stripe).

Ken Miyata and Frances Irish identified inJuly 1979 a specimen of Atractus (AMNH108943) collected on the Pacific coast ofEcuador as belonging to A. microrhynchus.Unfortunately, because of Ken Miyata’s death,they never published their discovery. In 2002,one of us (DC-H) examined that specimenand its accompanying notes written by K.Miyata and F. Irish; that specimen is clearlyconspecific with the specimens found recentlyin other localities of the Pacific lowlands ofEcuador and Peru. The examination ofrecently obtained specimens on the Pacificlowlands of Ecuador and Peru corroboratesCope’s description, and Miyata and Irish’sidentification allows us to associate them withA. microrhynchus. The specimens reportedherein have a dark brown cephalic capinterrupted on the parietal region by creamtransversal bands without contact in midlineand a more (DHMECN 3008, AMNH108943, and MUSM 22830) or less (MUSM22829) distinct paler band on the occipitalregion of the head; one of the individuals(MUSM 22829) has a nearly uniform palebrown dorsum, whereas the others havedistinct black blotches; all specimens havecream ventral ground color with well-definedirregular brown marks interrupted on thelateral portion of each ventral scale, formingbarely defined paraventral lines (better de-scribed as cream lateral area by interruptionof dark paraventral blotches) and a conspicu-ous postorbital black stripe reaching lastsupralabials (Figs. 2 and 3). The only featurein disagreement with the original description

is the number of infralabials contactingchinshields (three on the new specimens).Even though the holotype of A. microrhyn-chus might indeed be unusual among Atractusin having two infralabials in contact with thechinshields, we also are aware of the possibil-ity that Cope did not count the first pair ofscales behind the symphysial as infralabials (ausual Atractus feature; see Passos et al.,2009e). Because of the complex taxonomichistory of A. microrhynchus discussed aboveand the difficulties that many authors havehad in recognizing this species after itsoriginal description (including Cope), webelieve that a neotype designation is requiredto clarify the taxonomic status of the species.In doing so, we follow all qualifying conditionsof article 75.3 of the ICZN (1999), and weselect the specimen that is closest to the typelocality as the neotype of A. microrhynchus.

Atractus natans Hoogmoed and Prudente, 2003(Figs. 6–8; Table 1)

Atractus badius Dixon and Soini, 1977;Milwaukee Publ. Mus. Contrib. Biol. Geol.12:33.

Atractus cf. microrhynchus Dixon andSoini, 1986; Milwaukee Public Museum.

Atractus sp. Bartlett and Bartlett, 2003: Fig.205B (photograph of a specimen in life).

Atractus natans Hoogmoed and Prudente,2003; Zool. Med. Leiden 77:428.

Atractus emersoni Silva, 2004; Rev. Acad.Col. Cien. Exa. Fis. Nat. 108:423. Newsynonymy.

Holotype.—Adult female, MPEG 18836,collected on 1 August 1994 by M. S.Hoogmoed and T. C. Avila-Pires near conflu-ence of Apara and Mamiraua rivers (038020S,648510W, sea level), Estacao Ecologica deMamiraua, Melgaco, state of Para, Brazil(specimen examined).

Paratypes.—Juvenile female (MPEG18838), same data as holotype; adult female(RMNH 35530), sand bank on the left marginof Rio Mamiraua (03804 0S, 64848 0W, sealevel), Estacao Ecologica de Mamiraua,Melgaco; adult female (MPEG 20213), Esta-ao Cientıfica Ferreira Penna (01843 0S,518320W, sea level), FLONA de Caixuana,Rio Curua, Melgaco (all specimens examinedexcept RMNH 35530).


Referred specimens.—Adult females, ICN10097 (holotype of A. emersoni) and ICN10098 (paratype of A. emersoni) collected May2001 at locality of Boa Vista, Municipality ofBenjamin Constant (048250S, 708020W, ca. 65m asl), Brazil; adult male ICN 10099 (para-type of A. emersoni) collected at Quebrada delos Lagos, Municipality of Leticia (048130S,69856 0W, ca. 83 m asl), Colombia; andsubadult ICN not catalogued, from unknownlocality, but apparently donated by J. S. Haadfrom Colombian Amazonia (J. D. Lynch,personal observation). Sixteen specimens allfrom department of Loreto in Peru: Iquitos(03844 053 00S, 73814 050 00W, ca. 100 m asl):TCWC 39063; Zona Reservada Allpahuayo-

Mishana (ca. 038530S, 738270W, 100 m asl):TCWC 42792–801, 47803–04, MCZ 151769;Moropon (ca. 038270S, 738320W, ca. 100 masl): TCWC 39064; Rıo Maniti: TCWC 52502.

Diagnosis.—Atractus natans is distin-guished from all congeners by the followingcombination of characters: (1) 17-17-17smooth dorsals; (2) usually two postoculars;(3) moderately long loreal; (4) temporals 1þ2;(5) usually seven supralabials, third and fourthcontacting orbit; (6) usually seven infralabials,first four contacting chinshields; (7) five or sixmaxillary teeth; (8) four gular scale rows; (9)usually four preventrals; (10) 154–163 ventralsin females, 136–152 in males; (11) 18–26subcaudals in females, 23–31 in males; (12)dorsum dark brown to black generally withdistinct irregular black blotches on flanks,juveniles and subadults with cream occipitalband; (13) venter mostly black, with lateralregion of ventral scales paler (beige tocreamish brown); (14) moderate body size infemales (390 mm SVL), small (250 mm SVL)in males; and (15) short tail in females (8.8–10.6% of SVL), moderate long (13.5–15.2% ofSVL) in males.

Comparisons.—Among all congeners, A.natans shares just with A. tamessari Kok,2006 ca. 154–163 ventrals in females, fourinfralabials contacting chinshields, dorsumdark brown to black with dots or blotches onthe flanks, venter mostly black, and five to sixmaxillary teeth. Atractus natans differs fromA. tamessari in having 17 dorsal scale rows,

FIG. 6.—Dorsal (A) and ventral (B) views of thespecimen of Atractus natans (TCWC 42800) fromMishana, department of Loreto, Peru.

FIG. 7.—Dorsal view of the holotype of Atractus emersoni (ICN 10097).


seven supralabials, paler occipital band injuveniles and subadults, dorsum usually withdistinct dorsal blotches white bordered (vs. 15dorsal scale rows, usually eight supralabials,lacking paler occipital band, dorsum generallyuniform black, occasionally scattered withirregular red dots).

Description.—Head approximately twice aslong as wide, flattened in lateral view androunded in dorsal view; slightly distinct frombody; snout truncate in lateral view, slightlyrounded in dorsal view; rostral subtriangularin frontal view, visible in dorsal view, approx-imately twice as wide as high; internasal widerthan long; internasal suture sinistral withrespect to prefrontal suture; prefrontal ap-proximately as long as wide; supraocularsubrectangular, approximately twice as longas wide; frontal pentagonal or subtriangular,as long as wide; parietal approximately twicelonger than wide; nasal divided; nostril locatedbetween prenasal and postnasal; prenasal twoor three times as high as long, contactingrostral, internasal, first supralabial, and post-nasal; postnasal as long as wide, contactingprenasal, prefrontals, loreal, and second pairof supralabials; moderately long loreal; lorealcontacting eyes, prefrontals, nasals, and sec-

ond to third supralabials; pupil round; usuallytwo postoculars; upper postocular slightlylonger, and lower slightly higher; temporals1þ2; anterior temporal twice as long as high,contacting parietal, fifth to sixth supralabials,postoculars, and posterior temporals; upperposterior temporals fused, shield four timeslonger than wide; seven supralabials, third andfourth contacting orbit; second supralabialhigher than first and smaller than third; sixthhigher and seventh longer than remainingsupralabials; symphisial semicircular, approx-imately six times as wide as long; seveninfralabials, first four pairs contacting chin-shields; first pair of infralabials in contactbehind symphisial, preventing symphisial/chinshield contact; chin shields twice as longas wide; four gular scale rows; usually fourpreventrals; 17-17-17 dorsal scale rows, lack-ing apical pits and supra-anal tubercles;caudal spine moderately long, conical, andslightly acuminate. Maxilla arched in dorsalview, with four or five prediastemal and twopostdiastemal teeth; prediastemal teeth angu-lar in cross section, robust at base, narrower atapices, curved posteriorly; first five teethlarge, moderately spaced, decreasing gradual-ly in size posteriorly; maxillary diastema short,

FIG. 8.—Dorsal (A) and ventral (B) views of the paratype of Atractus emersoni (ICN 10098).

TABLE 1.—Variation in the meristic characters of the Atractus natans. Samples referred below as Atractus emersoni andAtractus natans represent the type series for each taxon respectively, and specimens from the Iquitos region, previouslyidentified as A. badius (Dixon and Soini, 1977) or A. cf. microrhynchus (Dixon and Soini, 1986), also are A. natans as

defined here.

Sample Sex Ventrals Subcaudals Supralabials Infralabials Infralabials contacting chinshields Maxillary teeth

A. natans Male n ¼ 1 136 23 7 7 4 5–6Female n¼2 158–163 19–21

A. emersoni Male n ¼ 1 146 29 7 7 4 5Female n ¼ 2 155–156 21–23

Iquitos region Male n ¼ 10 144–152 25–31 7 7 4 5–6Female n ¼ 6 159–162 18–26


with space equivalent to size of fifth predias-temal tooth; postdiastemal teeth half size offifth prediastemal tooth; lateral process ofmaxilla poorly developed.

Juvenile Color in Preservative.—Dorsum ofhead dark brown to black, except for snout(rostral, internasals, and anterior portion ofprefrontals) and occipital band (usually com-plete) cream to light brown; large occipitalband, reaching anterior region of parietals,posterior temporals, and occipital scales;background of head dark brown to black withsnout region (rostral, nasals, and loreal) creamto light brown; anterior supralabials (first andsecond) cream, remaining supralabials mostlyblack with cream dots concentrated onanterior portion of each scale; infralabialsand chinshields usually black, with littleinvasion of pale pigment (creamish yellow tobrown); gular region creamish yellow scat-tered with black dots; venter usually creamanteriorly, scattered with disperse dark browndots or blotches; mid to posterior region ofbelly tends to become uniformly black bycollapsing black blotches on median region ofventral scales; ventral surface of tail uniformlyblack; dorsal ground color of body dark brownwith 40–60 irregular black blotches pale(cream to light brown) on flanks; irregularblotches (one or two scales long) covering fifthto sixth dorsal scale rows; first three dorsalscale rows occasionally with dispersed blackdots (half or one scale long); first dorsal scalerow beige to pale brown, usually withreticulate pattern of cream below black dots.

Adult Color in Preservative.—Adults withsnout and occipital pale regions of headdarker than juvenile (beige to dark brown);belly mostly black, except at lateral margin ofventral scales creamish brown to beige;dorsum usually uniformly black or with poorlydistinct blotches along body.

Color in Life.—Dorsal ground color of bodyblack to dark reddish brown, usually withblack pale (light reddish) bordered blotches;mental region cream, with pale reddish brownirregular blotches; belly mostly black, withlateral margins of ventral scales pale brown(beige); median to posterior region of bellyuniformly black.

Hemipenis.—Retracted organ bifurcates atsixth and extends to level of seventh sub-

caudal. Hemipenis moderately bilobed, barelysemicapitate, and semicalyculate; lobes dis-tinct and restricted to distal region of capit-ulum; lobes approximately conical, withdistinct length; right lobe (same side of nakedpocket) always longer than left; lobes slightlysmaller than proximal region of capitulum;capitulum uniformly covered with concentrat-ed spinulate calyces; capitular crotch evidenton both sides of hemipenis, more developedon asulcate and barely defined on sulcate sideof organ; capitulum located below sulcusspermaticus bifurcation, delimited on proxi-mal region by moderate hooks; capitulumslightly retracted on median region of asulcateside and equivalent to hemipenial body onsulcate side of hemipenis; sulcus spermaticusdivides on middle of organ above distalportion of hemipenial body; sulcus spermati-cus branches centrifugally oriented, reachesapices of lobes; margins of sulcus spermaticusnarrow and stout, bordered with spinules frombase to tip of lobes; hemipenial body sub-cilindrical, uniformly covered with small tomoderate hooked spines; largest spines con-centrated on lateral region of sulcate andmedial portion of asulcate side adjacent tocapitulum; basal naked pocket located in theright side of organ, extending to proximalregion of hemipenial body; basal region ofhemipenis with longitudinal plicae and dis-persed spinules.

Quantitative Variation.—Largest males 250mm SVL, 38 mm TL; largest female 385 mmSVL, 41 mm TL; tail 13.5–15.2% (n ¼ 2) ofSVL in males, 8.8–10.6% (X¼9.8, SD¼0.75; n¼ 4) of SVL in females; 136–152 (X ¼ 144.5,SD¼ 6.6; n¼ 4) ventrals in males, 154–163 (X¼ 158.1, SD¼ 3.4; n¼ 7) in females; 23–31 (X¼ 27.2, SD ¼ 3.6; n ¼ 4) subcaudals in males,18–26 (X¼ 21.5, SD¼ 2.7; n¼ 7) in females; 7(n¼ 44 sides) or 8 (n¼ 2 sides) supralabials; 7(n¼ 44 sides) or 8 (n¼ 2 sides) infralabials; 1(n¼ 4 sides) or 2 (n¼ 42 sides) postoculars; 3(n¼ 1) or 4 (n¼ 6) preventrals; 6–9 (X¼ 7.9,SD¼0.7; n¼ 14 sides) dorsal scale rows at thelevel of second subcaudal; 5 (n¼11 sides) or 6(n ¼ 3 sides) maxillary teeth; retracted hemi-penis extends to the level of sixth or seventhsubcaudal (n ¼ 2).

Distribution.—Amazon rainforest south tothe Amazon River, from Mishana (038470S,


738300W) department of Loreto, Peru, east toMelgaco (018470S, 508440W), state of Para,Brazil. Atractus natans occurs from sea levelto 100-m elevation (Fig. 9).

Remarks.—Although Cope’s description ofA. microrhynchus was brief, there are notabledifferences between it and characteristics ofthe specimens from Iquitos previously re-ferred to Atractus badius (Dixon and Soini,1977) or Atractus cf. microrhynchus (Dixonand Soini, 1986). Most notably, Cope (1868)did not mention any pattern overlaid on thebrown dorsal coloration of A. microrhynchus.That he described the coloration of A. micro-rhynchus as ‘‘like that of Tantilla’’ mayindicate as well that the dorsal coloration ofthe holotype of A. microrhynchus was uniformbrown (with a black cephalic cap) as in manyspecies of Tantilla. However, the presence ofblack blotches on the flanks is variable (moreor less conspicuous) among the specimensherein referred to A. microrhynchus, and alsoin the Amazonian populations of A. natans(Hoogmoed and Prudente, 2003) and A.emersoni (Silva, 2004; present study). As such,there are two possibilities: (1) the holotype ofA. microrhynchus also would have barelydistinct dorsal blotches as in MUSM 22829(Fig. 2A) or (2) the specimen reported byCope (1870) was uniformly dark brown or

black, as are many individuals of A. natans andA. emersoni (Hoogmoed and Prudente, 2003;Fig. 7). This last possibility of melanisticindividuals in the Amazon basin better ex-plains why Cope (1870) referred anotherspecimen to A. microrhynchus if the laterwas apparently not blotched.

The ventral coloration of A. microrhynchus,as described by Cope (1868), also differs fromthat observed in the specimens from theAmazon basin. In the latter specimens, theventer is usually black in the middle, with acream lateral area or with dispersed blotcheson the anterior region of belly (Figs. 6–8),whereas A. microrhynchus has a cream venterwith irregular pale brown marks not collapsedin the middle of the belly at least on theanterior and mid portions of the body (Figs.1–3). Although the specimens from theAmazon basin often have some dark spots orblotches in the postocular region, these spotsnever form a stripe as described by Cope in A.microrhynchus (Figs. 6–8), which was likelyconspicuous and well defined to be noted byCope in his brief description. Based on theabove-mentioned observations, we considerthe specimens from Iquitos, herein referred toA. emersoni or A. natans (see below), to bedifferent from A. microrhynchus. The lesslikely possibilities that Cope’s description of

FIG. 9.—Geographical distribution of Atractus natans. Open squares represent the type locality of the species.


A. microrhynchus is inaccurate in terms ofcoloration, and that the type locality is in error(as has apparently been noted with othermaterial from the Orton expedition), are notsupported (see Passos et al., 2009e, foradditional comments in this respect).

The examination of the type series andadditional specimens of A. emersoni and A.natans revealed that all meristic, morphomet-ric, color pattern, and hemipenial featureslargely overlap; the variation in these speciesalso overlaps that of the specimens previouslyreported by Dixon and Soini (1977, 1986)from the Iquitos region (Table 1). Whereasmature individuals of A. natans usually displaya melanistic pattern with barely distinctblotches that differ from the holotype of A.emersoni (a subadult specimen), a paratype ofA. emersoni (ICN 10099) shows poorlydistinct blotches on the dorsum like those onthe holotype of A. natans (Hoogmoed andPrudente, 2003; Figs. 6–8). Although Silva(2004) did not describe a pale occipital bandin the juvenile specimens of A. emersoni,examination of the type series of the speciesrevealed the presence of a darker pale (beige)band on the occipital region and also conspic-uous pale blotches on the snout region of A.emersoni (Figs. 6–8); both characteristics areevident in most individuals of A. natans (seeHoogmoed and Prudente, 2003). Apparently,the minor or major contrast between theoccipital band and ground color is correlatedwith ontogenetic changes of coloration ormelanism (this question cannot be addressedwith the available sample). Even so, accordingto our sample, adults of both species tend tobecome darker in the course of their ontog-eny. Furthermore, the hemipenis descriptionof A. emersoni provided by Silva (2004: Fig.23) was not accurate with respect to capitationstructures. The examination of this organrevealed that it is in fact semicapitate andsemicalyculate (sensu Zaher, 1999), as wasdescribed by Hoogmoed and Prudente (2003:434, 436) for A. natans. Finally, as found formost Amazonian congeners (Hoogmoed,1980; Cunha and Nascimento, 1983; Martinsand Oliveira, 1993; Passos and Fernandes,2008; Prudente and Passos, 2008), A. natansalso has a wide range of distribution along thebiome (see Hoogmoed and Prudente, 2003).

Therefore, for the reasons discussed, A.emersoni is herein relegated to the synonymyof A. natans.

DISCUSSION

Passos et al. (2009e) proposed the A.multicinctus species group to accommodatePacific lowland Atractus that share a uniquecombination of morphological characters forthe genus. They pointed out that the stronglybilobed hemipenis and the basal bifurcation ofthe sulcus spermaticus might constitute de-rived character states in the evolution ofcertain species of the ‘‘goo-eaters’’ clade ofthe Dipsadini (P. Passos, personal observa-tion). Atractus microrhynchus shares bothhemipenial conditions, as well as the presenceof narrow, enlongated, hooked spines in theintrasulcar region, with members of the A.multicinctus species group (A. boulengeriiPeracca, 1896; A. clarki Dunn and Bailey,1939; A. medusa Passos, et al., 2009e; and A.multicinctus). However, in terms of externalmorphological characteristics (meristic, mor-phometric, and color pattern traits), A. micro-rhynchus is most similar to the Andean A.dunni, A. ecuadoriensis, and A. occidentalis,and to the Pacific lowland A. echidna and A.iridescens (last two from the lowland A.paucidens species group).

In fact, using the key for Pacific lowlandAtractus provided by Passos et al. (2009e), A.microrhynchus falls at the sixth step in thekey. However, A. microrhynchus differs fromA. iridescens and A. paucidens (alternativesteps in that dichotomy) in the number ofventral scales; however, see the comparisonssection of this study for additional diagnosticcharacters among these taxa. Although A.microrhynchus is morphologically most simi-lar to the Andean A. dunni, A. ecuadoriensis,and A. occidentalis, the taxonomic status ofthe latter forms will be discussed in asubsequent paper. Most of the externalmorphological characters shared by A. micro-rhynchus and the aforementioned taxa arewidespread and likely homoplastic features(e.g., color pattern and relative tail size) thatmay occur individually or in some combina-tion in several other species or species groupsin the genus. Because a robust phylogenetichypothesis is still lacking for Atractus, at this


moment we prefer to use the hemipenialfeatures to infer the putative affinities of A.microrhynchus. Therefore, we allocate A.microrhynchus to the A. multicinctus speciesgroup on the basis of shared unusual hemi-penial characters such as strongly bilobedorgan; basal bifurcation of the sulcus sperma-ticus; and the presence of elongated, narrow,hooked spines in the intrasulcar region.Finally, because there are ongoing taxonomicstudies on the Amazonian species of Atractus,we refrain from allocating A. natans to thecurrently proposed species groups.

Acknowledgments.—We are deeply indebted to N.Gilmore (ANSP) for information about the holotype ofR. microrhynchum and about specimens collected by theOrton Expedition in Amazon basin. We thank F. Sornozaand the Jocotoco Foundation for collecting the neotype ofthe A. microrhynchus and allowing access to theBuenaventura reserve; H. Yanez-Munoz for sharinginformation on the type locality; and R. Cadenillas andV. Pacheco for collecting the Peruvian specimens of A.microrhynchus and sharing field data. We thank threeanonymous reviewers for commentaries and suggestionson an early version of the manuscript. We thank thefollowing curators (in alphabetical order) for allowingexamination of specimens under their care: J. Cordova(MUSM), J. Dixon and L. Fitzgerald (TCWC), J. Lynch(ICN), A. Prudente (MPEG), and M. H. Yanez-Munoz(DHMECN). For financial support, PP is grateful toConselho Nacional de Desenvolvimento Cientıfico eTecnologico (CNPq), Pro-Reitoria de Pos-Graduacao ePesquisa da Universidade Federal do Rio de Janeiro (PR-2/UFRJ), Fundacao de Amparo a Pesquisa do Estado deSao Paulo (FAPESP; process 2011/50313-0), and Funda-ao Carlos Chagas de Amparo a Pesquisa do Estado do Riode Janeiro (FAPERJ) for financial support; and DC-H isgrateful to Ma. Elena Heredia, Laura Heredia, theResearch Training Program/Smithsonian Women’s Com-mittee of the National Museum of Natural History(Smithsonian Institution), and the Russell E. TrainEducation for Nature Program of the World WildlifeFund.

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Accepted: 17 May 2012Associate Editor: Christopher Raxworthy


rediscovery of atractus microrhynchus of the …

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