Geophis, Wagler, 1830

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 : 38-41

Geophis , species inquirenda

[ G. brachycephalus , auctorum] Figures 19 , 20B

MATERIAL: Bocas del Toro: About 3 km W Almirante, 40 m ( KU 110701) ; La Loma ( MCZ 19325–19326 ) ; Río Changena , 830 m ( KU 110702) ; Río Changena ( FMNH 130969 ) . Chiriquı´: Upper Río Chiriquı´, Fortuna Dam Site , 1000 m ( AMNH 114317– 114319 ) ; south slope Quebrada de Arena , 1120 m ( AMNH 124015 ) .

COMMENTARY

The earliest specimens, from La Loma in Bocas del Toro, were collected and identified as Geophis brachycephalus by Dunn (1942: 4). Downs (1967: 154) had no additional specimens from Bocas del Toro, but he did mention a few small Costa Rican samples lacking blotches. I have not seen these, but I have collected and examined additional Panamanian specimens that may be conspecific with the La Loma specimens and distinct from brachycephalus .

These specimens are uniformly black or brown in preservative (not bluish as in some albeit not all preserved G. brachycephalus ) and all lack pale spots or partial ringlike markings (a vague pale nape band present or absent). The hemipenis of an Atlantic­versant specimen differs from that of a highland specimen of G. brachycephalus in having a relatively long, slender capitulum with no trace of bilobation (fig. 20). However, part of the difference (especially relative slenderness—but not relative length—of the capitulum) conceivably might be an artifact of eversion technique (see comment under Methods of Study).

Several of the newer specimens are from low and intermediate elevations (40–830 m) in Bocas del Toro, but four are from a collection that I made in the highland valley of the Río Chiriquí in Chiriquí Province (1000– 1120 m). This valley may be considered as delimiting the eastern end of the Cordillera de Talamanca and the western end of the Serranía de Tabasara´. This high Pacific­side valley is influenced by moisture­laden air spilling southward over the low continental divide, providing access to animals and plants from the Caribbean versant (the herpetofauna

TABLE 3 Comparison of Segmental Counts between the Boquete Population of Geophis brachycephalus and Combined Samples of Geophis , species inquirenda in Western Panamaa

also has a strong Talamancan component, but only two of 50 species collected have primarily Pacific­drainage distributions [ Myers and Duellman, 1982: 14]). Unfortunately , the Geophis collected in the valley of the upper Chiriquí are all females, and their assignment to the Atlantic­versant population is based on segmental counts and absence of pale spots or partial rings in all four specimens .

There is a pronounced difference in numbers of ventrals and subcaudals between Panamanian populations with color polymorphism ( brachycephalus ) and those apparently without (species inquirenda). For purposes of comparison, I calculated population statistics from the counts given by Slevin (1942: 474–476) for his large collection of Geophis brachycephalus from the vicinity of Boquete, where it was the most abundant snake in the cafetals. As shown in table 3, Boquete specimens of brachycephalus have significantly higher numbers of ventrals and subcaudals in both sexes. There is no overlap in female ventral counts. Overlap in male ventrals and subcaudals is caused by one brachycephalus ( CAS 78983) with exceptionally high counts of 142 + 46, without which the Boquete ranges would be 121–129 ventrals and 37– 41 subcaudals. The high ventral count, however, was confirmed by Downs (1967: 148), who gave 140 ventrals for this specimen. The differences are maintained when adjustments are made for somewhat dissimilar methods of counting ventrals. 19

Downs (1967: 148) remarked that ventral counts are somewhat lower in Panamanian G. brachycephalus from Finca Lérida to the west of Boquete , and that both these Panamanian populations have considerably lower counts than in Costa Rican populations. The ranges and means for all his Costa Rican specimens combined were given as 131–148 (138.5) in 54 males and 135–145 (140.7) for 70 females. These ranges encompass those for species inquirenda in Panama, but little more can be said without detailed examination of the situation in Costa Rica, from where considerably more material is now available. See Remarks below .

COLOR IN LIFE

In life, the dorsa are uniformly black; preserved specimens ( MCZ 19325–19326, KU

19 There is, as noted under Methods of Study, a difference in methods of counting ventrals, with Slevin’s counts expected to average probably one or a few ventrals more. Downs (1967: 148) recounted Slevin’s material and determined sex of some specimens (e.g., juveniles) left unsexed by Slevin. Downs, whose counting method was closer to the one I used, gave the following ranges and means for the Boquete sample of Geophis brachycephalus : 34 males, 119–140 (mean, 124.9), 28 females, 123–132 (mean, 127.1). Adding the ‘‘preventrals’’ to my counts for Geophis , species inquirenda yields 2 males, 134–140 (mean, 137.0 ± 4.24), 7 females, 138–144 (mean, 140.4 ± 2.07).

somewhat bluish because it was about to shed.

110701 [see below]) may fade to brown with the head becoming lighter than the body. Two specimens from the Río Changena ( FMNH 130609, KU 110702) in preservative have pale but vague nape bands, which may have been more pronounced in life (grayish white in KU 110702). My field descriptions for several specimens follow:

KU 110701: Shining black above and on tip of chin and infralabials. Venter immaculate white except subcaudals heavily marked with black. [Specimen has faded to brown in preservative, with the head becoming paler than the body.]

AMNH 114317–114319 [see fig. 19]: Uniform shining black above [one bluish, see below]; lower, posterior edge each scale white in scale row 1. Venter greenish white, turning black on chin and under tail. Iris dark, appears black. Tongue pale gray to base of fork, tips of fork unpigmented.

AMNH 124015: Black above (with slight grayish white tinge on lower side of neck behind jaw), white below, turning grayish black under tail. Iris dark. Tongue pale gray becoming white (unpigmented) on tips of fork.

W.E. Duellman noted one to be gray dorsally and subcaudally—but this specimen (KU 110702) is black in preservative and probably was preparing to shed—with a creamy white belly and a grayish white nuchal collar. Similarly, I noted that a specimen in the series AMNH 114317–114319 above was

NATURAL HISTORY

The habitat is lowland and lower montane rain forest and cloud forest in an elevational range of 40–1120 m. One (KU 110702) was under a log by day. I found a lowland specimen (KU 110701) as it was crawling on a log across a rocky forest steam, at night in the rain. The highest elevation specimen (AMNH 124015) was active at night, on the ground in cloud forest, at the edge of a small seepage pool in which Hyla graceae was calling. Three specimens (AMNH 114317– 114319) from the area of the Fortuna Dam site were found on a second­growth hillside; a workman found one, I caught another at night on a trail near the river, and I found the third by day—on the ground near a rocky stream, at about 10 a.m. on a sunny morning.

REMARKS

A satisfactory resolution of the taxonomic problem presented by this species inquirenda is outside the scope of the present paper, which I had intended to confine to problems in eastern Panama. Costa Rican specimens and names currently in the synonymy of Geophis brachycephalus will need to be considered. There especially needs to be examination of more hemipenes to determine if the differences seen in figure 20 are correlated with presence or absence of color­pattern polymorphism.

Geophis hoffmanni (W. Peters) Map 2

Downs (1967: 155) gave the range of this species as ‘‘low and moderate elevations in Honduras... and Nicaragua, southward along both Caribbean and Pacific versants of Costa Rica into Panama’’. This little snake evidently is common in parts of Costa Rica and has long been known to occur in extreme western Panama; Downs’ easternmost station in Panama was El Valle de Antón in Coclé Province, based on AMNH 76016; a second specimen (KU 116902) has subsequently been collected there. El Valle de Antón, an old volcanic crater, is shown as the westernmost station in map 2.

As listed below, two additional specimens extend the range eastward in Panama from El Valle to the central lowlands and thence to the Piedras­Pacora Ridge (map 2), and a third specimen indicates the occurrence of G. hoffmanni in Colombia. All three specimens are dark brown above, whitish below, with dorsal scales smooth or mostly smooth, in 15–15–15 rows, supralabials 5 (3–4 in eye); temporals absent (see Remarks); infralabials 6 (1–3 in contact with first genials) .

MADDEN FOREST: The late Howard W. Campbell collected a specimen (AMNH 113561) of Geophis hoffmanni in the former Canal Zone in July 1968. It was found on ‘‘Madden Forest Rd. 20 yds. N George Green Pk.’’ It is a male 200 mm in total length, including 29 mm (14.5%) tail length, with 125 ventrals and 29 pairs of subcaudals. In addition to the presence of anal ridges, the dorsal scales are weakly keeled at the end of the body and are striated on the rear of the body and tail.

As discussed elsewhere ( Cadle and Myers,

2003),

The Madden Forest Preserve (formerly in the Canal Zone, now in Prov. Panama´) straddles Madden Road, a paved highway between Summit and Madden Dam. The roughly rectangular Preserve, about 3 × 5 km, lies across the very low continental divide, which swings close to the Pacific coast and seldom exceeds 200 m above sea level on this part of the isthmus. The northerly (Atlantic) drainage via the upper Río Chilibre system flows into the Chagres below Madden Dam; the southerly (Pacific) drainage adds to the Canal waters via the Río Pedro Miguel. The vegetation is lowland monsoon rain forest.

The surprising thing about this specimen is that it is the only verifiable specimen of Geophis from the central lowlands, which, however, are not as well known as might be expected, nor is the lowland fauna as uniformly distributed as might be expected (for a recent contribution, see Ibáñez et al., ‘‘1995’’ [1997]). The poorly collected Madden Forest has several snakes that are not found on the well­known Barro Colorado Island only about 24 km to the northwestward, including Dipsas nicholsi and Dipsas viguieri ( Cadle

Figures

Fig. 19. Geophis, species inquirenda? A specimen (AMNH 114317♀) collected in 1976 near the Fortuna Dam Site (prior to construction), 1000 m, upper valley of the Río Chiriquí (Chiriquí Province, western Panama). Although it is Pacific drainage, the highland valley has a climate comparable to that of the Atlantic versant. Pending further investigation, four female Geophis from the area are tentatively associated with unicolored specimens from the Atlantic versant of western Panama.

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).