Conopsis megalodon Taylor and Smith 1942

Conopsis megalodon (Taylor and Smith, 1942)

Toluca megalodon Taylor and Smith, 1942:338.

Toluca conica Taylor and Smith, 1942:340 –343. nov. sin.

Type specimen: EHT­HMS 23640.

Type locality: Cerro San Felipe, Oaxaca.

Diagnosis: This snake is characterized by the following combination of characters: fused prefrontals and internasals; 3 upper labials before eye; brown or reddish dorsal coloration with a vertebral line of hexagonal spots, and tessellated sides. Ventrally it is yellowish with no spots or marks. It differs from C. nasus, the only species with which it could be mistaken, by the reddish­brown dorsal coloration, its smaller body size (SVL: 107–250 mm in C. megalodon, and 100–320 mm in C. nasus), and by its distributional range, restricted to the highlands of the Sierra Madre del Sur in Guerrero and Oaxaca, which does not overlap with C. nasus.

Description: A species with fused prefrontals and internasals; loreal scale present or not; a pointed rostral; nasal pierced by nostril on each side of head; a preocular and two postoculars; hexagonal frontal, contacting internasals; temporal formula 1+2; 7 or 6 upper labials and 6 lower labials; 3 or 2.5 upper labials before eye; genial shields separated by one scale; or fused; a mean of 122.9 (118–135) and 33.9 subcaudals (29–49); 17 rows of smooth scales at midbody; dorsum reddish­brown, with vertebral line of hexagonal spots, sides of body tessellated; venter yellowish, with a series of paired dots on each ventral scale.

Measurements: Adult specimens of Conopsis megalodon average 192.6 mm snoutvent length (107–250 mm), 229.1 mm in total length (130–292 mm), body diameter 6.6 mm.

Variation: This species generally shows fused prefrontals and internasals (94.2% of examined specimens), or divided (5.8%). Loreal scale absent (66.2 %), or present (33.8 %). Upper labials 7 (56.4%), but some have 6 (32.1%), or 7/6 (11.5%). Upper labials before eye from 2.5 (54.4%) to 3 (45.6%). Lower labials from 6 (63.2%), 7 (16.2%), 6/5 (11.8%), to 5 (8.8%). First pair of genial shields in contact (47.2%) or separated by one (52.4%), or two scales (1.4%). Dorsal coloration is brown­reddish (77.9%), cinnamon (7.35%), beige (7.35%), gray (4.4%), or amielistic (2.45%), with a line of hexagonal vertebral spots (38.5%) or elongated hexagonal spots (33.8%) or any of these with sides of body tessellated (18.5%), or no pattern (1.5%). Ventral coloration creamy (69.2%), yellow (17%), yellow­orange (3%), whitish (7.7%), or gray (3.1%). The venter has a row of paired dots (58%), dots at edges of scales (24. %), a medial row of dots (6.4%), or immaculate (6.5%).

Distribution: Conopsis megalodon in the Sierra Madre del Sur (fig. 6); it has been collected in the states of Guerrero and Oaxaca from 1730 to 3200 m, in pine, oak forest and deciduous forest. It is usually under rocks, logs, stumps, and on dirt roads, from April to December, being more abundant from July to August.