Geophis bellus, MYERS, 2003

MYERS, CHARLES W., 2003, Rare Snakes-Five New Species from Eastern Panama: Reviews of Northern Atractus and Southern Geophis (Colubridae: Dipsadinae), American Museum Novitates 3391, pp. 1-48 : 30-38

Geophis bellus , new species

Figures 11–14 , 15C ; map 2

HOLOTYPE: KU 110703 (field no. CWM 3223 ), an adult male caught by C.W. Myers on December 13, 1964, at 700 m above sea

14 After reading the above discussion in manuscript, J. M. Savage kindly consulted Dunn’s notes in his possession and concurs that the ‘‘sabanas’’ records of Geophis and Trimetopon must be a cataloging error. Dunn’s notes contain no reference to specimens of either genus as having been part of the composite ‘‘sabanas’’ collection.

level near community of Altos de Pacora (east of Cerro Jefe ), Province of Panama´, central Panama. The type locality is a few km northeastward of the summit of Cerro Jefe, upper Río Pacora drainage, at roughly 9°15̍N, 79°22̍W .

ETYMOLOGY: The specific name bellus is a Latin adjective meaning ‘‘pretty’’ and ‘‘charming’’, referring to the appearance of this elegant little snake in life.

DIAGNOSIS: A small, slender member of the sieboldi group of Geophis distinguished from other members of the genus by the combination of (1) dorsal scales in 15 rows, smooth anteriorly but moderately keeled and striated on posterior part of body; (2) anterior temporal present or absent; (3) six supralabials; (4) eye small, going about 3.5–4 times into snout length; (5) dorsal and ventral surfaces uniformly dark (black in life) except for vivid white band across rear of head; and (6) hemipenis unicapitate, about one­fourth bilobed, nearly acalyculate, with calyces confined distally to lobes of the large capitulum.

The overall color pattern (fig. 11) alone distinguishes Geophis bellus from any other small colubrid in Panama. Other small Panamanian snakes having blackish or dark brown bodies, and heads partially or mostly white, are Enuliophis sclateri , Ninia atrata , and Tantilla albiceps —all of which have pale venters. See Comparisons for discussion and contrast with relevant congeners (including G. betaniensis , G. brachycephalus , G. nigroalbus , and G. talamancae ).

DESCRIPTION OF HOLOTYPE

Despite its small size and slender habitus, the male holotype is unambiguously sexually mature because (1) the hemipenial spines had hardened, (2) the relatively large testes (about as long as the snake’s head) are strongly tubular, (3) the slender vasa deferentia are convoluted, and (4) sperm were present in a small fragment of testis examined under a compound microscope. The anterior (right) testis is 6.8 mm long and the posterior is 6.5 mm long, both being about 2.1 mm wide as measured in situ.

PROPORTIONS AND SCUTELLATION: It is a very small, short­tailed snake, 201 mm total length, 32 mm tail length (tail 15.9% of to­ tal). Body quite slender, barely wider than high (at maximum of about 4.8 × 4.6 mm), rounded ventrolaterally. Dorsal scales in 15 rows throughout, smooth on anterior half of body, with rows 4–12 becoming moderately keeled and striated on posterior half; inconspicuous anal knobs present on lower lateral scales above cloaca; apical pits not detected at 40× magnification under reflected light. One preventral (undivided gular), 131 ventrals, undivided anal plate, 33 pairs of subcaudals.

Following description of head (fig. 12) after Downs’ format (1967, for G. brachycephalus ); see also table 2 for measurements: Head barely distinct from neck; snout long, bluntly pointed, projecting well beyond low­ er jaw; rostral well visible from above, where its length is about 23% of its distance to frontal, not projecting between internasals; internasals small, slightly wider than long, less than half as long as prefrontal suture; prefrontal suture 64% length of frontal plate; frontal broader than long, roughly rhomboidal in shape (strongly angular anteriorly); parietals the largest head plates, their median suture shorter than frontal plate; supraocular forming posterior two­thirds of upper eye margin.

Nasal deeply grooved above naris, divided below, anterior and posterior parts subequal, their combined lengths four­fifths that of loreal; long loreal entering eye; no preocular; eye very small, contained about 4 times in snout (left eye 3.6×, right eye 4.1×), its length (and height) smaller than its distance from lip; supralabials 6, third and fourth in eye on left side, fourth only on right side; fifth supralabial largest and in contact with parietal on left side only; one postocular, higher than long, subequal in size to supraocular; temporals 0 + 1 on left side, 1 + 1 on right (first temporal the apparent result of a division of supralabial 5).

Chin tapered, anteriorly rounded; mental rounded, wider than long, separated from genials by first pair of infralabials, which are in medial contact; infralabials 7, pairs 1–4 in contact with anterior genials, 4–5 with posterior genials; posterior genials small and posteriorly rounded, in contact with each oth­ er; short posterior intergenial suture 33% the length of anterior intergenial suture; two median gulars and one preventral (gular wider than long) between posterior genials and first ventral. Tubercles sparsely present on some dorsal and ventral head plates, but these presumed sensory organs are minute and inconspicuous.

COLOR PATTERN: Color in life uniform glossy black above and below, with a conspicuous white band across rear of head (fig. 11). The white band anteriorly includes the posterior halves of supralabials 4 and the rear edges of the frontal plate, encroaching slightly on supraocular and postocular scales; the band extends posteriorly onto the nape for a distance of two scales behind the parietal plates; the rear lateral edges of the band an­

TABLE 2 Measurements (in mm) of an Adult Male Geophis bellus , New Species, and Juvenile Males of Geophis brachycephalus and Geophis negroalbus

gle anteroventrally under the head and extend to the posterior genials as a pair of whitish streaks. After some 20 years in alcohol the black parts of the dorsum and venter have faded to dark brown, and the front part of the head has differentially faded to a lighter brown than the body.

MAXILLO­ PALATO­ PTERYGOID ARCH: Right maxilla (fig. 13) extending slightly anterior to the suture between second and third supralabials (equal to anterior extension of palatine), bearing 10 rather stout, subequal teeth; anterior tip of maxilla pointed, toothless; posterior end of maxilla with slight ventral curve, tapering to blunt point; maxilla somewhat dorsoventrally compressed, bearing large palatine process. No maxillary process on palatine. Anterior end of ectopterygoid single, not expanded.

HEMIPENIS: Fully everted right hemipenis about 6.5 mm long, reaching to subcaudal 6. Following account based mainly on left everted organ, except for description of the lobes which is based on right organ 15: Moderately bifurcate (fig. 14), with lobes comprising about one­fourth of total length. Distinctly capitate, but on asulcate side the nude collar is almost interrupted medially by spines; capitulum comprising half the length of organ on asulcate side but nearly 70% on

15 The hemipenes were only half everted at time of preservation. Both were subsequently dissected out, soaked in glycerin, then in a saturated solution of trisodium phosphate, and inflated with carmine­dyed petroleum jelly. The right organ everted fully but is somewhat twisted, and many of the spines are evidently bent out of normal alignment. The left organ is straight and the spines are aligned more symmetrically, but owing to small tears the lobes could only be partially everted.

The above description therefore is based mainly on the left hemipenis, with recourse to the right organ for the distal parts of the lobes. The figure likewise is a composite.

sulcate side. Sulcus spermaticus divides below midpoint of hemipenis but well onto capitulum, where the branches diverge and distally curve slightly around to other side (a modified centrifugal configuration if the lobes are not abnormally twisted), terminating close to the apices of lobes.

Organ entirely spinose (but spines distad from base of capitulum rather flexible, seeming less or not calcified): Proximal part of hemipenis with spinules and small spines, then two fairly large spines that are widely separated, one on each side of sulcus spermaticus. Midsection with a few dozen moderate­sized hooked spines that are most concentrated on asulcate side. Capitulum rather sparsely covered with small spines (or spinelike papillae, see above); in lateral view, the spines proximal and lateral to the sulcus branches are seen to be aligned in oblique rows, but between the branches of the sulcus spermaticus and on the lobes the arrangement is one of vague horizontal rows; tips of lobes spinose. Capitulum acalyculate, except for indication of weak calyces on lobes, these calyces being formed by elongated low tissue ridges connecting bases of some spines. An elongated lateral naked pocket on basal fourth of organ; from the perspective of the asulcate side, the nude pocket is on the lefthand side of the left organ and the right­hand side of the right organ.

COMPARISONS

Geophis bellus is a member of Downs’ (1967: 137) sieboldi species group, with which it generally agrees in features of scutellation, small eye, long projecting snout, and, especially, in the simple (unforked, unexpanded) distal end of the ectopterygoid process and in maxillary features. Pertinent maxillary characters include a small number of subequal teeth, dorsal and ventral flattening of the maxilla, a toothless anterior projection, and a ventrally curved, bluntly point­ ed posterior end (compare fig. 13 with that of G. brachycephalus [ Downs, 1967: 26]). The presence of an anterior temporal plate— on the right side of the holotype of G. bellus —is a rare condition in the sieboldi group. It seems quite clearly to have arisen by division of the fifth supralabial (compare lateral views of head in fig. 12), thus providing a clue to the method of original loss of the primary temporal in the sieboldi group (see Downs, 1967: 14).

The single specimen of Geophis bellus was shown to F. L. Downs shortly after he had completed his monograph of the genus. It is the specimen mentioned in a footnote ( Downs, 1967: 146) as leading him ‘‘to doubt that my inclusion of G. nigroalbus Boulenger in the synonymy of G. brachycephalus is justified.’’ Downs (1967: 152) had not seen the Colombian type of Boulen­ ger’s nigroalbus , but direct comparison of the holotypes of bellus and nigroalbus convinces me that they are different species (see below). I also closely compared the type of bellus with the only central Panamanian specimen of brachycephalus , which probably was collected within a few kilometers of the former. Measurements of these specimens are given in table 2, with further comparisons following.

Geophis bellus is a much smaller snake than the Colombian G. nigroalbus , in which males attain a total length of at least 370 mm, and the slender bellus is relatively less robust. The juvenile holotype of G. nigroalbus , although 67 mm shorter than the adult holotype of G. bellus , nonetheless has a slightly larger head (figs. 15A, 16, and table 2). The holotype of nigroalbus resembles bellus in having a dark body and a similarly positioned and vivid pale band across the head and nape (absent or vestigial in other specimens of nigroalbus seen), but differs in the uniformly pale venter (adult nigroalbus may acquire dark transverse banding ventrally). 16

Although the adult male holotype of G. bellus is essentially identical in total length to the nearly sympatric juvenile male of G. brachycephalus , the latter specimen (figs. 15B, 18) is a more robust snake with a longer and wider head and noticeably larger eye;

16 Unfortunately, I have seen too few Colombian specimens to be able to fully characterize Geophis nigroalbus , or even to conclude that but a single species is represented. The juvenile holotype (134 mm total length) from Pavas in Valle de Cauca is the most distinctive of five specimens because of its broad, welldemarcated nape band. A smaller juvenile (116 mm total), from Santa Rita in Antioquia, has a less extensive, poorly defined nape band that is dorsally incomplete, and this specimen has a relatively larger eye (but ontogenetic change in relative eye size is not uncommon). Three adults, one with a faint trace of a nape band, differ from the two juveniles in having dark bands across the ventrals .

The holotype of G. nigroalbus and three other Colombian specimens (BMNH 98.10.27.3, FMNH 43727, 54882) examined by me are listed in Downs (1967: 153) under the name brachycephalus . The fifth specimen examined is LACM 136675, one of a series reported by Restrepo and Wright (1987) from Betania in Valle de Cauca. The specimens with data are from roughly 1500– 1700 m in the Cordillera Occidental, but Downs also listed one (not seen by me) from the Cordillera Oriental (Landázuri [900 m fide Medem, 1965: 342], Depto. Santander).

most of the various head plate and suture measurements are smaller in bellus , except for slightly longer internasals and parietals. The central Panamanian specimen of brachycephalus also differs from the probably sympatric bellus in having a pale­spotted dorsum and a pale venter (fig. 18).

Comparisons of the holotype of G. bellus with specimens of G. brachycephalus from western Panama lead to similar conclusions: Geophis bellus is a much smaller, more slen­ der species. The striking nape band of bellus seems to be a retention of a variably presentor­absent juvenile feature in brachycephalus and nigroalbus . Downs (1967: 150) noted that a pale collar, if present, is usually lost in brachycephalus by 150 mm SVL (adult ho­

1906.4.30.71), a juvenile male 134 mm total length, shown ×1.7.

lotype of bellus = 169 mm SVL), with traces of the collar only occasionally persisting to a larger size. According to Downs, brachycephalus attains a maximum total length of 418 mm in males and 460 mm in females.

I also compared the holotype of Geophis bellus directly with the Costa Rican holotype of G. talamancae Lips and Savage (1994) , which is similar in size, relative tail length, and in numbers of ventrals and subcaudals. 17 The juvenile female holotype (the only re­

17 The holotype of Geophis talamancae is now cataloged as LACM 147196. My own scale counts and measurements for this specimen include 133 ½ ventrals, 32 pairs of subcaudals, 212 mm total length, 33 mm tail length (15.6% of total). It is a juvenile female (said to be an adult in the original description), with inactive ovaries containing a few tiny ova and with flat, nonconvoluted oviducts.

ported specimen) of G. talamancae , is 11 mm longer than the adult male specimen of bellus , but it obviously is a more robust snake, with a much stockier body and a relatively larger head (greatest body width in talamancae = 7.2 mm vs. 4.8 mm in bellus ; greatest head width × head length to end of parietals in talamancae = 6.0 × 8.5 mm vs. 4.5 × 7.0 mm in bellus ). Geophis talamancae appears to be close to G. brachycephalus and perhaps G. nigroalbus . Extent of keeling probably does not distinguish it from brachycephalus as thought by Lips and Savage (1994: 411), but the ventral color pattern (dark pigmentation across bases of ventrals causing a fuzzy pattern of alternating dark and white cross­bands) distinguishes talamancae at least from Panamanian G. brachy­ cephalus and Geophis , species inquirenda. This type of ventral pattern (suggested in one case to mimic noxious millipedes [ Leonard and Stebbins, 1999]) is approached in some specimens of the Colombian G. nigroalbus (FMNH 54882, LACM 136675). Although I do not suggest conspecificity, it needs noting that G. nigroalbus is not distinguished from talamancae by separation of postocular and supraocular by an anterior projection of the parietal ( Lips and Savage, 1994: 411). 18

Finally, a word on the Colombian Geophis betaniensis Restrepo and Wright (1987) , which is known from two specimens col­

18 This character comes from Restrepo and Wright (1987: 195), who evidently observed the condition in one population of Geophis nigroalbus (I have seen LACM 136675 from their sample; the parietal extends to the eye above exceedingly small postoculars), but the condition does not pertain to the holotype nor to the few other nigroalbus that I have seen (footnote 16).

lected in sympatry with the similar­sized G. nigroalbus . It is a distinctive species, separated from nigroalbus at a glance by dark ventrolateral stripes that sharply confine and set off the pale midventral area. Geophis betaniensis may be more closely related to G. nigroalbus than initially thought. Restrepo and Wright (1987: 191) provisionally assigned G. betaniensis to the championi species group, but Lips and Savage (1994: 414) later moved it to the sieboldi group based on ‘‘a complete concordance’’ in head shape and scutellation. Cursory examination of the paratype of G. betaniensis shows that it lacks certain derived maxillary characteristics shared by most members of the sieboldi group; the maxilla is not ventrolaterally compressed and lacks a toothless anterior projection (the first tooth springs from the anterior tip of the bone). Nonetheless, a Costa Rican member of the sieboldi group— Geophis zeledoni —also lacks a ‘‘distinct toothless tip’’ on the maxilla, which is dorsoventrally flattened only along its posterior half (fide Downs, 1967: 145, 175). But the maxilla of Geophis betaniensis is relatively high and I see no sign of dorsoventral compression even posteriorly (right maxilla examined in situ). Tentatively accepting Lips and Savage’s (1994: 414) reassignment of betaniensis (as a species with presumably plesiomorphic maxillary features) makes the sieboldi group of Geophis the only one known from South America.

Geophis betaniensis was described as having ‘‘a small tentacle­like projection from the posterior margin of the nostrils’’ ( Restrepo and Wright, 1987: 191–192, fig. 3). A photograph shows the ‘‘hair­like ‘tentacle’’’ on the right side of the holotype. A tentacle was said to be present only in the left nostril of the paratype (LACM 136189), but I could see no sign of it when I examined the specimen in early 2002. My own guess is that these structures, initially present in three of four nostrils, were foreign to the two snakes—perhaps defensive arthropod urticating hairs that might glance off the snakes’ head scales but temporarily lodge in their nostrils.

It is of course impossible to determine at this time whether there is significant color and size variation in Geophis bellus , but its specific status, as first suggested by the striking coloration and small adult size, is strongly corroborated by hemipenial differences: In G. bellus the hemipenis (fig. 14) is bilobed for about a fourth of its length, with weak calyces only on the distal lobes; the large capitulum otherwise is sparsely covered with small spines (or large papillae). In G. nigroalbus (fig. 17) and G. brachycephalus (fig. 20) the organ is barely or not bilobate and the entire capitulum is covered with well­developed calyces.

REMARKS

I found the unique specimen of Geophis bellus at night, while walking on a muddy road through cut­over evergreen seasonal forest, at 700 m above sea level. The type locality is on the ‘‘Piedras­Pacora Ridge’’, the low continental divide that separates the watershed of the Río Pacora (Pacific versant) from that of the upper Río Chagres (Atlantic). Geophis bellus shares the Piedras­Pacora Ridge with G. brachycephalus and G. hoffmanni (see below), and also with the new species Atractus depressiocellus and A. imperfectus of this paper. The one new species of Geophis and two new Atractus are known only from single specimens collected over a period of 29 years. The two previously named species of Geophis seem to be just as rare on the Piedras­Pacora Ridge (although common in other parts of their ranges), since each is known there from a single specimen, as follows.

Geophis brachycephalus (Cope)

Figures 15B , 18 , 20A ; map 2

A RANGE EXTENSION: I assign to Geophis brachycephalus a GML specimen from ‘‘ Cerro Azul’ ’ on the Piedras­Pacora Ridge in central Panama; it was collected for the Gorgas Memorial laboratory by A. Herrera in October 1965. It is a juvenile male with uncalcified hemipenial spines, 202 mm in total length. It has 15–15–15 rows of dorsal scales that are smooth on the neck, becoming striated and weakly keeled by ventral 13 and then progressively more strongly keeled posteriorly; the posterior half of the body and proximal half of the tail are quite strongly keeled, with the keels becoming weak and disappearing toward the end of the tail; however, the fine striations of the dorsal caudal scales continue up to the terminal spine. Supraocular present; no preocular; one postocular; 0 + 1 temporals; six supralabials (3–4 in eye); seven infralabials (1–4 touching anterior genials, 4–5 touching posterior genials); 138 ventrals, undivid­ ed anal, 50 pairs of subcaudals; see table 2 for measurements. The dorsal color is blue in alcohol, with 11 pale dorsal rings or paired spots on the posterior body and several on the tail (fig. 18) .

As remarked under Atractus depressiocellus , the ‘‘ Cerro Azul’ ’ of GML field parties is equivalent to Cerro Jefe , the 980 m high point on the Piedras­Pacora Ridge about 37 km NE of downtown Panama City. Specimens so labeled might have been taken anywhere from about 5 km southwestward of Cerro Jefe to about 5 km to the north, most likely in an elevational range of about 200– 800 m.

The distribution of Geophis brachycephalus is partly clarified earlier in this paper (under Records Excluded from Central Panama). The present specimen is the only one known to me from central Panama. It appears to mark the eastern and southern limit of the range, where brachycephalus seems very rare compared with its abundance in the highlands of Costa Rica and western Panama. As already mentioned, South American records of this species are tentatively assigned to the Andean Geophis nigroalbus .

TAXONOMIC COMMENT

Downs (1967: 149) commented that ‘‘The color pattern is the most perplexing variable in G. brachycephalus , and is at least partly responsible for the lengthy synonymy’’. Some populations appear to be highly polymorphic in color pattern, as exemplified in Panama by Slevin’s (1942: 474–476) description of a large population sample from the vicinity of Boquete in the Chiriquí highlands:

26 specimens show reddish spots, blotches or short stripes,

23 specimens are uniform in color,

2 specimens show a white collar and no lateral spots,

2 specimens show a white collar and red lateral spots.

Such populations, as well as the single specimen (fig. 18) from central Panama, seem to fit in with the original descriptions of Colobognathus [= Geophis ] brachycephalus and its simultaneously described synonym C. dolichocephalus ( Cope, 1871: 211–212) .

However, I strongly suspect that some snakes with uniformly dark dorsa from along the Atlantic versant of western Panama (and Costa Rica?) are currently masquerading in collections under the name Geophis brachycephalus . Although I am not prepared to give adequate attention to this problem, it may be helpful to call attention to it by segregating the possible sibling species as follows.

Figures

Fig. 11. Geophis bellus, new species. The holotype (KU 110703) shown approximately two times life size.

Fig. 12. Head scutellation of Geophis bellus, new species (holotype), ×6. Fifth supralabial and posterior temporal shown in gray in lateral views.

Fig. 13. Right maxilla of Geophis bellus, new species (holotype), shown in lateral and ventral views.

Fig. 14. Hemipenis of Geophis bellus, new species. Everted organ of holotype shown in sulcate and asulcate views, ×10. The drawing is a composite, based on left hemipenis except that the lobes are added from right organ (see footnote 15). The relatively large capitulum is nearly acalyculate, with weak calyces being confined to the small lobes.

Fig. 15. Heads of Geophis, all ×4.5. A. Colombian holotype of G. nigroalbus, juvenile male 134 mm total length (see fig. 16 for whole body). B. Central Panamanian specimen of G. brachycephalus (GML), juvenile male 202 mm total length (see fig. 18 for whole body). C. Central Panamanian holotype of G. bellus, new species, an adult male 201 mm total length (pale lateral streak behind head band is reflected light; body uniform black above and below, as seen in fig. 11).

Fig. 18. Geophis brachycephalus (Cope), a juvenile male from the Piedras­Pacora Ridge in central Panama (GML specimen, 202 mm total length; see fig. 15B for lateral view of head).

Fig. 20. Hemipenes of Geophis. Right­side organs shown at same scale (×6.7) in sulcate and asulcate view. A. Geophis brachycephalus, from a highland population with pattern polymorphism (UMMZ 57958; Boquete, western Panama). B. Geophis, species inquirenda, from Atlantic­versant population apparently lacking pattern polymorphism (La Loma, western Panama; MCZ 19326).