A New Species of Sibon (Reptilia, Serpentes, Colubridae) from Belize, Central America

Abstract

Sibon neilli sp. nov. is described from the outskirts of Belize City, Belize (formerly British Honduras). It differs from all of its congeners except S. sanniola in having a high number of supralabials and exclusion of the loreal from the orbit by two preoculars. S. neilli differs from S. sanniola in number of ventrals, number of caudals and color pattern. During the course of studies on the herpetofauna of Belize (formerly British Honduras) the second author discovered an undescribed species of Sibon occupying a jar in a Belize City pharmacy. This new snake is described below. We are pleased to name it in honor of Wilfred T. Neill in recognition of his many contributions to herpetology, and to the herpetology of Belize in particular. Sibon neilli sp. nov. Holotype.-Milwaukee Public Museum (MPM) 8929, a male from the vicinity of Belize City, Belize District, Belize, collected July 1974 by Ernest Smith. Diagnosis.-S. neilli differs from all other Sibon, except S. sanniola, in not having the loreal enter the orbit and in the high number of supralabials. It differs from male S. sanniola in having a slightly higher number of ventrals and subcaudals and is strikingly different in color pattern. S. neilli has 34 dark brown body bands whereas S. sanniola has a middorsal row of spots. In addition, S. neilli has the 7th supralabial in contact with the lower postocular and primary temporal, but not in contact with the secondary temporal. This condition occurs occasionally in S. sanniola, but in no other species of Sibon. Description of holotype.-Rostral broader than deep; internasals two-thirds as long as prefrontals; frontal longer than broad; interparietal suture equal to length of frontal; nasal semidivided; loreal higher than long and not entering orbit; 2 preoculars; 2 postoculars; no suboculars; temporals 1 + 2; upper labials 9 with 4th, 5th, and 6th entering the orbit, 7th slightly enlarged and in contact with the lower postocular and primary temporal, 8th larger than 7th and in contact with primary temporal and lower secondary temporal; 10 lower labials, none in contact behind postmental and 4 in contact with anterior chin shield, 7th enlarged and in contact with 2nd and 3rd chin shields; 3 pairs of chin shields, anteriormost longest, posterior tips of 3rd pair separated by an azygous gen,ial; postmental 3 times larger than mental. Ventrals 162; subcaudals 88; anal entire; dorsal scale rows 15-15-15; vertebral scale row not enlarged. Maxillary teeth about 15. Snout-vent length 236 mm; tail length 104 mm. Hemipenis (examined in situ) 11 subcaudals long, basally spinose and with long papillae distally, an abrupt demarcation between the two kinds of ornamentation occurring at level of subcaudal 5. Dorsal ground color pale tan with 34 dark brown bands on body and 23 on tail, body bands 2.5 scales long at vertebral scale row and becoming narrower laterally; bands extending to edges of ventrals and are wider than tan interspaces dorsally, but laterally interspaces longer;