Cosmocerca acanthurum n. sp. (Figures 2–7, and 8–13) Description: Medium size, stout nematodes. Prominent sexual dimorphism, males one-half length of females. Lateral alae present in both males and females. Cuticle transversely striated. Mouth with 3 small V-shaped lips, dorsal lip with 2 sessile papillae, each ventrolateral lip with 1 ventral sessile papilla, 2 amphids. Oesophagus with indistinct buccal cavity, short pharynx, cylindrical corpus and posterior bulb containing valves. Nerve ring not observed. Male: Based on 5 mature specimens. Length 2.18–2.38 mm (2.30 ± 0.09 mm, n=4 [2.50 mm]), width at midbody 111–180 (147 ± 31, n=4 [141]). Pharynx 6–15 (10 ± 5, n=4 [15]) long, oesophagus length 225–246 (237 ± 9, n=4 [258]), oesophageal bulb 39–45 (42 ± 2, n=2 [45]) long, 42–51 (45 ± 3, n=4 [51]) wide. Excretory pore at level of oesophageal bulb. Distance from excretory pore to anterior end 219–240 (232 ± 9, n=4 [252]). Lateral alae beginning 66–87 (74 ± 11, n=3 [66]) from anterior end and teminating 165–255 (212 ± 36, n=4 [228]) from posterior end. Tail flexed ventrally, 69–108 (89 ± 15, n=4 [117]) in length. Gubernaculum spoon shaped, tridentate, 75–90 (84 ± 6, n=4 [99]). Spicules equal, 51–66 (58 ± 6, n=4 [81]). The arrangement of caudal papillae is: 2 rows of somatic papillae, dorsolateral in position; 14 pairs of caudal papillae, in ventral position: 9 precloacal, 2 anterior most pair simple, followed by 5 pairs of rosette-like papillae on plectanes, 2 posterior most pair, also simple, 1 pair at level of cloaca, and 4 pairs postcloacal. Female: Based on 14 mature specimens. Length 3.43–4.91 mm (3.941 ± 0.454 mm, n=13 [5.026 mm]), width at midbody 210–490 (359 ± 69, n=13 [364]). Pharynx 9–21 (13 ± 5, n=12 [9]) long. Oesophagus length 315–447 (393 ± 38, n=13 [420]), oesophageal bulb 63–93 (74 ± 7, n=12 [78]) long, 72–96 (85 ± 7, n =12 [96]) wide. Excretory pore anterior to oesophageal bulb. Distance from excretory pore to anterior end 300–402 (357 ± 43, n=7 [378]). Lateral alae beginning 60–105 (80 ± 12, n=10 [135]) from anterior end and teminating 560– 756 (661 ± 52, n=13 [574]) from posterior end. Posterior end of body terminating in straight, stiff tail, 560– 714 (631 ± 45, n=13 [588]) long, possessing numerous cuticular spines of variable size. The anterior most pair robust and bifurcate. Tip of tail trifurcate. Vulva postequatorial, opening 1.62–2.39 mm (1.96 ± 0.26 mm, n = 8 [2.38 mm]) from caudal end. Eggs 81–120 (98 ± 9) long by 57–90 (68 ± 7) wide (in 49 eggs from 8 females); allotype 87–96 (94 ± 4) long by 60–81 (69 ± 5) wide. Type Material: Holotype No. 5723, Allotype (5724), Paratypes (5725), and vouchers (5726), deposited in the Colección Nacional de Helmintos, México City, Mexico (CNHE). Prevalence of infection and mean intensity: Llano Grande, Estado de México: P. leprosa: 6/11, 54.5% (3 worms per infected host); C. orculus: 1/4, 25% (2 worms per infected host). Texcalyacac, Estado de México: P. leprosa: 3/14, 21.4% (1.6 worms per infected host) Type-host: Pseudoeurycea leprosa (Cope, 1869) Other host: Chiropterotriton orculus (Cope, 1865) Site: Intestine. Type-locality: Llano Grande, Estado de Mexico, México (19°20’20”N, 98°43’14”W, altitude: 3230 masl). Other locality: Texcalyacac, Estado de Mexico, México (19°07’15”N, 99°29’45”W, altitude: 3091 masl). Etymology: The species name is from Greek (acanthi = spine + oura = tail) and refers to the unusual spined condition of the tail in females. Remarks: The genus Cosmocerca is currently composed by 24 species (Ricci, 1987; Bursey et al., 2005, 2006) and is characterized by possessing a variable number of plectanes in the caudal region of males. According to Bursey et al. (2005, 2006), species of Cosmocerca are distributed along 4 biogeographical regions with 6 in the Australian, 11 in the Neotropical, 1 in the Oriental and 6 in the Palaearctic (these authors did not recognize the validity of C. sardiniae described by Ricci, 1987 from the plethodontid Speleomantes supramontis from Sardinia, Italy). Most of the species currently allocated to Cosmocerca are parasites of frogs (14), toads (6), lizards (2) and salamanders (2). The new species most closely resembles C. novaeguinenae, C. cruzi, C. paraguayensis, C. parva, C. podicipinus, C. travassosi, C. banyulensis, C. japonica, and C. ornata by having 5 plectanes pairs, however, it differs from these species by the presence of a uniquely spined tail in the female, which is the single most diagnostic feature of the new species we described herein. Cosmocerca acanthurum n. sp. is the second congeneric species to have a plethodontid as definitive host. The other record correspond to C. sardiniae however, this species is clearly distinguished from C. acanthurum n. sp. by having spicules that are larger than the gubernaculum, and by having 4 plectanes pairs. Additionally, this species was described from the only plethodontid species occurring in the Palaearctic region, and the new species we describe herein is found in the State of Mexico, which lies in the Transmexican Volcanic Belt, in the transitional zone between the Nearctic and Neotropical regions.

Published as part of Falcón-Ordaz, J., Windfield-Pérez, J. C., Mendoza-Garfias, B., Parra-Olea, G. & León, G. Pérez-Ponce De, 2007, Cosmocerca acanthurum n. sp. (Nematoda: Cosmocercidae) in Pseudoeurycea leprosa and Chiropterotriton orculus from the Transmexican Volcanic Belt, Central Mexico, with a checklist of the helminth parasites of plethodontid salamanders, pp. 27-49 in Zootaxa 1434 (1) on pages 28-32, DOI: 10.11646/zootaxa.1434.1.2, http://zenodo.org/record/5077205