Diagnosis: This caecilian is large and heavy-bodied, with a body length about 30-35x the diameter. The stoutness distinguishes C. tentaculata from more attenuate caeciliids such as Caecilia disossea and Oscaecilia bassleri, which may have a body length of 80x the diameter. The dorsal surface is dark bluish gray, while the ventral surface is slightly paler. No pale markings are present on C. tentaculata, in contrast to the similar heavy-bodied species Microcaecilia albiceps and Siphonops annulatus, both of which have pale markings. The eye is usually visible as a dark spot beneath the skin (Duellman 1978).
Description (except where noted, from Taylor 1968, describing specimen AMNH 49961 from Río Copanza, Ecuador) : Caecilia tentaculata has a total body length of up to 631 mm according to Taylor (1968), and up to 987 mm according to Duellman (1978). The body is relatively thick and cylindrical. Eyes are in sockets and visible through the skin. Sensory tentacles are located in a depression below and slightly anterior to each nostril, and are not visible from above. The snout projects beyond the mouth and the nostrils are visible in dorsal view. Jaws contain two rows of teeth on top and one row on the bottom, with the second row on top being replacement teeth for the animal. Teeth are small and curve back to the rear of the mouth (Moore 1964). Two nuchal collars are located immediately following the head, fused and indistinct dorsally and lacking transverse grooves, but well defined ventrally and laterally. Primary annuli (122+) and secondary annuli (34+) are present and mostly incomplete, but tertiary annuli are lacking. The primary annuli are incomplete dorsally for the first 80% of the body, and are incomplete ventrally except on the posterior part of the body. Secondary annuli are short in the anterior part of the body, then fusing dorsally, and finally completing encirclement just preceding the vent. The skin is very smooth. Beginning at about the 20th primary annulus, one or two scales are located in well-defined tissue pockets within the folds of each primary annulus, with both the size and number of scales increasing gradually down the body. Subdermal scales are absent. The terminal area is flattened. The vent is transverse, with three denticulations preceding the vent, two lateral to it, and four denticulations posterior to it. Anal glands are lacking.
Caecilia tentaculata is slate-gray on the dorsum, light brown on the sides and outer part of the venter, and lighter gray in the middle of the venter. The annuli are darker in color, usually a grayish-black (Taylor 1968, describing specimen AMNH 49961 from Río Copanza, Ecuador). Duellman (1978) describes the color as dark bluish gray on the dorsal surface and lighter on the ventral surface, but does not mention any brown coloration or whether the annuli are darker.
Savage and Wake (2001) pointed out that earlier treatments of Caecilia tentaculata (Dunn 1942; Taylor 1968) had in fact combined more than one species under that name. Specimens from eastern Panama to northern Colombia that were formerly known as C. tentaculata (for example USNM 25188, MCZ 17376) have been referred to C. isthmica (Savage and Wake 2001). Another complication is that two Linnaean descriptions of Caecilia tentaculata (from 1749 and 1754) appear to come from two different species (Dunn 1942, p. 503; cited in Savage and Wake 2001).
Although it had been reported that Linné's type specimen was not extant (Savage and Wake 2001), it has since been ascertained that the type is located in the collection at his Uppsala home (M. H. Wake, pers. comm.).