Micrurus surinamensis (Cuvier, 1817)

Passos, Paulo & Fernandes, Daniel S., 2005, Variation and taxonomic status of the aquatic coral snake Micrurus surinamensis (Cuvier, 1817) (Serpentes: Elapidae), Zootaxa 953, pp. 1-14 : 3-9

Micrurus surinamensis (Cuvier, 1817)

Elaps surinamensis Cuvier, 1817 , Regne Animal, ed. 1, 2: 84 Micrurus surinamensis — Beebe, 1919, Zoologica, 2: 216

Micrurus surinamensis surinamensis — Schmidt, 1952, Fieldiana, Zoology, 34, 29

Lectotype: Museum National d’ Historie Naturelle, Paris, number 3926, a male from Suriname, collected by Levaillant; originally syntype, designated as lectotype by Schmidt (1952) [not examined].

Diagnosis: Distinguished from other species of the genus by frontal scale narrower than supraoculars; only one supralabial (4th) contacting the eye; head flattened with nostrils and eyes directed upwards; process pseudocoronoid extremely developed; distinguished from M. nattereri by having 156–174 (instead of 180–195) ventrals in males and 169–187 (instead of 193–215) ventrals in females; supratemporals extending well beyond exoccipitals rather than reaching only the posterior portion of exoccipitals in M. nattereri ; posterior portion of parietal bone with a conspicuous sharp projection which is blunter in M. nattereri .

Description: Rostral scale broader than high, with a triangular shape in frontal view and visible from above; internasals less than half of the length of prefrontals, which do not enter the orbit; frontal longer than broad; supraoculars approximately as broad as the prefrontal; parietals about twice longer than wide; nasal divided; 1 preocular, longer than high; 2 postoculars; fourth supralabial enters the orbit; first pair of infralabials contacts behind symphysial; 1–4th pairs of infralabials contact first pair of genials; 4th or 4–5th pairs of infralabials contact second pair of genials; 2 pairs of genials; gulars generally 4; 15 dorsal scales rows, smooth, without reduction; anal plate divided.

Color in preservative: Dorsum of the head predominantly yellowish, with posterior margins of cephalic shields black bordered; supralabials, infralabials, and gular scales uniformly yellowish, generally with a posterior black border; the first black ring arises behind the parietals, crossing the posterior infralabials and gular region; black rings in triads, the central one wider than the outers; narrow yellow portions separate the black rings; triads are separated by broad red rings with scales bearing black pigmentation in the posterior edge; triads formula generally 3 / 2 / 6 / 2 / 3, consisting of a central wide black ring separated from the lateral narrow ones on each side by slender yellow portions, which are separated by broad red rings as interspaces; black rings become narrower laterally until reach the belly; dorsum and belly show the same pattern of triad; interspaces dorsally bearing black pigmentation in the posterior edge of scales.

Hemipenis (Fig. 1–2): Extends to the level of 8–10th subcaudal (everted organ), with subcylindrical shape; organ stout and bilobed, lobes somewhat distinct from the base; each lobe with a narrow tip; lobes become narrower to the tip, displaying some series of spines and spinules concentrated mainly on the lateral portions; sulcus spermaticus bifurcates just before the division of the lobes, about two­thirds the distance from the base of the organ; branches have centripetal orientation terminating on the distal region of the lobe; basal portion of the hemipenial body with a basal pocket moderately developed, which shows a medial and lateral folds; medial portion of the hemipenis bearing large spines (ca. 60) in the asulcate side, arranged in several rows; sulcate side with spines also concentrated in the medial portion; both sides with spinules mostly concentrated on the basal portion of the hemipenial body.

Hemipenis of Micrurus surinamensis (IBSP 68050), from Pontes e Lacerda state of

Mato Grosso, Brazil. 1, sulcate; 2, asulcate side. Scale bar 5 mm.

Skull ( Figs. 3–9 ): Premaxilla transversally expanded on its anterior portion, constituting the paired lateral projections (processus transversus) that are elongate and become narrower distally; the basis of each projection is ventrally pierced by a small foramen; ascending process of the premaxilla narrow, dorsally contacting the median portion of nasals; posteriorly, premaxilar bears the nasal process and palatine process, the later having two ramus contacting the septomaxilla dorsally and, generally, extending up to the anterior tips of the vomers; nasals round with a descending lamina contacting the septomaxillaries sagital and posteriorly; a projection of the nasals contacts frontals medially; septomaxillaries anteriorly concave with a lateral ascending projection curled backward; in its posterior edge, septomaxillaries show a straight and narrow projection in lateral view and slants posterolaterally in ventral view; vomer hemispherical, concave dorsally; posteriorly, in ventral view, shows a reduced alar process; prefrontals subtriangulars in dorsal view, contacting the frontals in the posterior edge; the anterolaterals expansions comprise the anterior portion of the orbits and have an articular surface with the prefrontal process of the maxillaries; lachrimal foramen circular and crosses the anterior portion of prefrontals; frontals semitriangulars in dorsal view, with a descending expansion that comprises the inner portion of the orbit; foramen orbitali intermedium to the lateroventral edges between frontals and parietal bones; parietal comprises the anterior region of the braincase, with the anteriormost portion forming the posterior portion of the orbits; anterolaterally, parietal bears two reduced projections and generally has a dorsal sagital crest; the posterior edge of parietal has a conspicuous sharp projection, contacting prooptics laterally and supraocciptal posteroventrally; ventrally, parietal contacts basisphenoid and frontals in their anteriormost portion, forming the naso­frontal joint; prooptics have a irregular form constituting the lateroposterior portion of the braincase, and bear the foramens prooptic and facial in the region that laterosphenoid is indistinctly fused to them; prooptics contact parietal anteriorly, supraoccipital dorsally, exoccipitals posteriorly, and basisphenoid anteroventrally; supraoccipital positioned between parietal and exoccipitals, with a sagital crest dividing it into two ramus that laterally reach the dorsal portion of prooptics; supratemporals flattened extending well beyond exoccipitals, and having a posterior rotation in the point of articulation with quadrate; exoccipitals comprise the dorsolateral edge of the foramen magnum and the dorsal portion of condilus occipitalis; exoccipitals also bear the foramen jugularis; basioccipital comprises the posteroventral portion of the braincase and laterally contacts exoccipitals, the anterior portion of basisphenoid, and, posteriorly, bears a bilobed process (processus basioccipitalis); basisphenoid comprises the anterior basis of the braincase, laterally contacting the prooptics and parietal; basisphenoid has a flat and narrow anterior projection that dorsally contacts the frontals in their anteriormost portion; maxillaries rounded with paired fangs positioned at the level of the lateral process of the septomaxilla; maxillary bears the prefrontal process of the maxilla, articulating with the distal portion of prefrontals, and the ectopterygoid process that articulates with pterygoids posteriorly; maxillaries also bear a lateral projection articulating with the maxillary process of the palatines; palatines with a dorsal projection toward vomers, contacting the palatine process, and a maxillary process that laterally articulates with maxillaries; palatines have seven teeth located ventrally, and contacts pterygoids posteriorly; ectopterygoids are cylindrical and slight bones, that anteriorly articulates with maxillaries and posteriorly with the lateral portion of pterygoids; pterygoids moderately curled backward articulating with quadrates, constituting the articulation palate­quadrate; the pterygoids contact palatines in the anteriormost portion, and contain about 15 teeth; quadrates robust having a dorsal portion flattened where contact supratemporals and constitute a surface of articulation with mandibles; quadrates, in the inner surface, with a rounded projection that articulates with stapes; mandibles are constituted by dentaries and a compound bone; dentaries with a uniform width and 11 teeth; in the outer portion, dentaries have a mental foramen and a division in the posterior portion, originating a conspicuous ventral projection; compound bone comprises prearticular, articular, surangular, angular, and splenial bones; articulars are fused to prearticular and surangular bones, and constitute the posteriormost portion of the mandibles; articulars have a ramified cavity that articulates with quadrates; prearticulars and surangulars are ventrally fused and the dorsal depression between them constitute the fossa mandibularis; surangular bone has a conspicuous pseudocoronoid process with a foramen (surangular foramen) piercing the anterior basis; cuneiform angulars positioned ventrally to the prearticulars and limited anteriorly by splenials, which are slender and contact the ventral portion of dentaries; the angle formed by the point of articulation of the dentary with surangular is of approximately 10o.

Mandibles of Micrurus surinamensis from state of Amazonas, Brazil. 6, inner face;

7, outer face. Scale bar 5 mm.

Variation: Largest male 890 mm SVL, 141 mm TL; largest female 1245 mm SVL, 145 mm TL. Characters that showed sexual dimorphism will be presented separately for males and females, while other data represent variation in both sexes. Ventrals 160–172 (x = 166.1; SD = 2.97; N = 26) in males; 169–182 (x = 175.6; SD = 3.17; N = 23) in females; subcaudals 31–40 (x = 35.0; SD = 2.37; N = 22) in males; 29–34 (x = 31.4; SD = 1.71; N = 22) in females; supralabials 7–8 (x = 7.2; SD = 0.38; N = 47); infralabials 6–8 (x = 7.0; SD = 0.29; N = 47); temporals 1+2 (N = 46 sides), 1+1 (N = 22 sides); number of triads 6–10 (x = 8.3; SD = 0.9; N = 35); width of the central ring at the level of the midbody 5–10 scales (x = 7.33; SD = 1.19; N = 33); width of interspaces 4–11 scales (x = 7.86; SD = 1.94; N = 29); hemipenis (in situ) extends 9–15 subcaudal scales (x = 10.6; SD = 1.71; N = 10), and the retractor muscle extends 13–22 subcaudal scales (x = 16; SD = 2.94; N = 7); pterygoidal teeth 13–16 (x = 14.40; SD = 1.14; N = 5); parietal crest may be present or absent.

Distribution (fig. 10): Distributed along Equatorial forest in South America in the Guiana’s region, Colombia, eastern of Ecuador, Peru, Bolivia and central Brazil. In Brazil, occurs in the states of Acre, Amazonas, Roraima, Rondônia, Pará, Maranhão, Tocantins, and Mato Grosso.

Figures

FIGURE 3 – 5. Skull of Micrurus surinamensis from state of Amazonas, Brazil. 3, dorsal view; 4, ventral view; 5, lateral view. Scale bar 5 mm.

FIGURE 8 – 9. Maxillas of Micrurus surinamensis from state of Amazonas, Brazil. 8, inner face; 9, outer face. Scale bar 5 mm.