Dendrophidion clarkii DUNN, 1933
Can you confirm these amateur observations of Dendrophidion clarkii?
|Higher Taxa||Colubridae, Colubrinae, Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)|
|Common Names||E: Clark's Forest Racer|
|Synonym||Dendrophidion clarkii DUNN 1933: 78|
Dendrophidion dendrophis — TAYLOR 1951: 92 (part)
Dendrophidion nuchalis — SAVAGE 1973: 17 (part.)
Dendrophidion nuchale — SCOTT et al. 1983: 372 (part.)
Dendrophidion clarkii — MCCRANIE 2011
Dendrophidion clarkii — CADLE & SAVAGE 2012
Dendrophidion clarkii — WALLACH et al. 2014: 224
|Distribution||Costa Rica, Panama, Colombia (incl. Valle del Cauca), Ecuador; elevation <100-1800 m.|
Type locality: El Valle de Antón, Panama
|Types||Holotype: MCZ 34878|
|Diagnosis||Diagnosis. Dendrophidion clarkii is characterized by (1) Dorsocaudal reduction from 8 to 6 occurring posterior to subcaudal 25 (range, 27–65); (2) anal plate usually divided (single in 8 of 45 specimens, partially divided in 1); (3) subcaudal counts > 135 in males and females; (4) head and anterior body of adults bright green, grading to brown posteriorly; (5) blackish or dark brown nuchal collar present in adults (less distinct or absent in juveniles); (6) posterior body brownish and having dark crossbands with embedded pale ocelli; tail brown to deep reddish, and either uniform (without crossbands) or with crossbands similar in overall pattern to posterior body; (7) ventral scutes in adults marked with narrow dark brown transverse lines across the anterior edge of each scute (Fig. 4); (8) total number of enlarged spines on the hemipenis relatively few (< 60); spines in the distal row uniform in size and numbering 15 (10–15).|
No species of Dendrophidion except D. clarkii has a bright green head and anterior body combined with a black nuchal collar, so the adult coloration is diagnostic and distinguishes this species from all others. Dendrophidion clarkii differs from species of the D. percarinatum group in having a more distal dorsocaudal reduction (typically proximal to subcaudal 25 in the percarinatum group compared to > 25 in D. clarkii). Single anal plates occur in the D. percarinatum group only in some individuals of D. paucicarinatum. Three species in the D. percarinatum group (D. brunneum, D. bivittatum, and a new Ecuadorian species described by Cadle 2012b) can have a green head or anterior body but these lack a blackish nuchal collar and have different patterns on the posterior body (Cadle 2010, 2012b). Dendrophidion boshelli has 15 dorsal scale rows at midbody (17 in D. clarkii).
In addition to coloration, Dendrophidion clarkii differs from species of the D. dendrophis group as follows. The three species of the D. vinitor complex (D. vinitor, D. apharocybe, D. crybelum; Cadle 2012a) have distinct pale bands on the neck in adults and fewer subcaudals (< 130) than D. clarkii (> 135). Dendrophidion dendrophis has a longer tail (> 70% of SVL in adults) and more subcaudals ( 150) than D. clarkii (< 70% and usually < 160, respectively). Dendrophidion atlantica lacks a nuchal collar and is brown on the anterior body.
Dendrophidion clarkii has previously been confused with the two other species of the nuchale complex, D. nuchale and D. rufiterminorum. Dendrophidion nuchale is allopatrically distributed from D. clarkii and both species have a blackish nuchal collar. Dendrophidion nuchale differs from D. clarkii in color pattern (anterior body never bright green in D. nuchale) and usually has fewer ventrals than D. clarkii (Table 1). Lieb (1988) mentioned that D. nuchale differed from D. clarkii in having dorsal scale row 1 unkeeled on the posterior body; while true of some individuals, others have keels on all rows, as in D. clarkii. The ranges of D. clarkii and D. rufiterminorum overlap in Costa Rica. The last species lacks a nuchal collar, has a reddish head and tail, and lacks extensive bright green on the anterior body. The tail of D. clarkii is deep red in some individuals but seemingly never in combination with a red head.
The dark nuchal collar and ventral markings are less distinct or absent in juveniles of D. nuchale and D. clarkii, and the red head and tail of D. rufiterminorum are less distinct or absent in juveniles. Thus, juveniles of these three species can be easily confused. The head of juvenile D. rufiterminorum is usually reddish brown and paler than the adjacent portions of the body (see Fig. 17; the same individual is portrayed in Savage 2002: pl. 414 and Solórzano 2004: fig. 56); however, in photographs of D. rufiterminorum we have seen the tail is dull brown similar to the posterior body, lacking the reddish coloration and contrast seen in adults. The heads and tails of juvenile D. nuchale and D. clarkii are not differentiated in color (except greenish heads in D. clarkii). The dorsocaudal reduction of D. rufiterminorum is distal to subcaudal 45 (< 55 in D. nuchale and D. clarkii; Table 1) [from CADLE & SAVAGE 2012].
|Comment||Synonymy partly after CADLE & SAVAGE 2012.|
Distribution: Not in Honduras fide McCranie 2015 (checklist Honduras, snakes of Honduras). See maps in Figures 12, 13, 20 in Cadle & Savage 2012.
Habitat: partly arboreal (Harrington et al. 2018).
|Etymology||Dendrophidion clarkii is named after Herbert C. Clark, first director of the Gorgas Memorial Laboratory in Panama and overseer of the Panamanian Snake Census, which contributed immensely to knowledge of the snake fauna of Panama (see Dunn 1949, Myers 2003).|