Paramitraceras tzotzil Cruz-López & Francke, 2013, sp. nov.
Creators: name: Cruz-López, Jesús A.
name: Francke, Oscar F.
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Opiliones
Stygnopsidae
Paramitraceras
Paramitraceras tzotzil

description: Paramitraceras tzotzil sp. nov.
(Figures 2, 11–17, 31–36)
Paramitraceras granulatus (partim): Goodnight and Goodnight (1953a): 25 (San Cristóbal de las Casas and Cruz Quemada specimens), misindentification.
Type material: male holotype (CNAN-0732) [December/17/2011; G. Contreras, J. Mendoza, E. Hijmensen & E. Goyer], (lat 16.63202º lon -92.53393º), MEXICO: Chiapas: San Cristóbal de las Casas, parada Flores Magón. One male and one female paratypes (CNAN-0733). Same data. Two females paratypes (AMNH). Same data.
Other material examined: one male (AMNH) [July/14/1950; C. & M. Goodnight], (lat 16.73666º lon 92.63833º), MEXICO: Chiapas: San Cristóbal de las Casas. One female (AMNH [July/12/1950; C. & M. Goodnight]). Same data (juvenile mentioned by Goodnight and Goodnight not found). One male and two females (AMNH) [July/24/1950; C. & M. Goodnight], (lat 16.90722º lon -92.09611º), MEXICO: Chiapas: Ocosingo, Cruz Quemada (there is not one juvenile, as Goodnight and Goodnight mentioned).
Etymology: The specific epithet refers to the “ Tzotzil ”, a Mexican people who live mainly in central Chiapas; it is used as noun in apposition.
Diagnosis: Differs to P. femorale, P. hispidulum and P. veracruz in having a bigger cheliceral hand. Similar to P. granulatum and P. pickardcambridgei sp. nov., but it can be differentiated by the apex shape of the eye mound, wich is rounded in the new species; middle tooth of the cheliceral movable finger semi-triangular, pointing to distal portion of the fixed finger; basal tooth of fixed finger absent, middle notch inconspicuous; basal bulge of the mesodistal tubercle of the pedipalpal tibia developed, appearing as a bifurcated tubercle; many spiniform setae on the mesal margin of pedipalpal tarsus; pars distalis rectangular, distal margin projected in the middle, lateral setae arranged in single row with more than 14 setae; with one pair of microdorsal setae.
Description. Male holotype: Measurements: Scutum length: 5.3, scutum width: 4.3.
Dorsum: Densely covered with uniform, small rounded tubercles; dorsal setae small, similar in size throughout; eye mound conical, strong and straight; ornamentation similar to the dorsum, with few setae (Fig. 14).
Venter: Ornamentation similar to dorsum. Sternum very short, with lateral margins inconspicuous between fourth coxae.
Chelicera: Scutum /cheliceral hand ratio: 1.28. Movable finger with medium tooth slightly displaced towards basally; rounded apex pointing to distal portion of the fixed finger; fixed finger without basal tooth; middle notch almost absent; median tooth rounded, barely visible (Fig. 15, 16).
Pedipalps: Measurements: 2.55/1.05/1.85/1.80/1.00. Femur with six rounded, scattered tubercles, similar in size; ectodistal tubercle of the tibia shallow, thin, rounded; mesodistal tubercle strong, spiniform, with rounded bulge close to apex, appearing almost bifurcated. Tarsus semi-conical, middle area not thickened, mesal margin with numerous spiniform setae, mostly grouped in distal portion (Figs. 11–13).
Legs: Measurements: I:2.70/1.00/2.00/2.20, II: 3.50/1.25/2.75/2.50, III: 2.95/1.00/2.32/2.80, IV: 3.50/1.25/ 3.30/3.70. Ornamentation similar to that on the body, femur III with ventral row composed of slightly longer tubercles, unlike the others. Leg VI with ectodistal tubercles of femur and tibia barely discernible (Fig. 17).
Genitalia: Pars distalis rectangular, compressed dorso-ventrally, distal edge medially pronounced, with rounded notch and two apices lateral to medium projection; bilobular projection swollen, with rounded lobes, apex rounded. Lateral setae arranged in one irregular row, with more than 14 semispatulate setae, distal seta separated from the rest, close to ventral microsetae; spiniform projections hidden, but barely visible. With a pair of dorsal microsetae, laterally to median portion of follis (Figs. 31–36).
Female: Very similar to male, with the following differences: considerably smaller chelicera, eye mound base reduced and distal tubercles on the femur and tibia IV smaller.
Distribution. Known only from central portion of Chiapas (San Cristóbal de las Casas and Ocosingo), Mexico.
Natural history. The type series was collected under and inside of decomposing trees. At the time of the capture, specimens showed thanatosis behavior, similar to that described for Paramitraceras veracruz Cruz-López and Francke, 2012 (Cruz-López and Francke, 2012).
Remarks. Mendes and Kury (2007) illustrated the dorsal view of pars distalis of Paramitraceras granulatum from a specimen with not specific locality in Mexico; from where a pair of dorsal microsetae is observed. Paramitraceras tzotzil sp. nov. is the only species known in the genus with a pair of dorsal microsetae in that position, so it seems that, the drawing illustrated by Mendes and Kury (2007) could be a specimen of P. tzotzil sp. nov.
Discussion
Paramitraceras granulatum, P. pickardcambridgei sp. nov. and P. tzoltzil sp. nov. exhibit remarkable sexual dimorphism in the dentition and size of the chelicerae (scutum /cheliceral hand ratio: 1.36, 1.37 and 1.28 respectively), unlike the other three known species in the genus, which lack such dimorphism. Furthermore, the two new species are easily distinguished from Paramitraceras femorale Goodnight and Goodnight, 1953 by the absence of the ventral mesodistal apophyses on femur IV in males. The two new species differ from P. veracruz in the margins and tubercles on the pedipalpal tibia.
Goodnight and Goodnight (1944, 1953a) mentioned additional distribution records for P. granulatum, providing the following explanation for their variation paragraph: “The animals from Las Casas and Cruz Quemada, for example, had much blunter eye tubercles. The male from Pichucalco had the spines at the ends of the third and fourth femora and the fourth tibia much larger. Also the entire body was somewhat more hairy than in those animals from the other localities”. They also emphasized that the material of Finca Guatimoc, Municipo Cacahoatán (wich we examined) was quite similar to the type material of P. granulatum. These specimens, along with the other material examined from Tapachula, Chiapas, are the true P. granulatum (Fig. 43).
Paramitraceras granulatum has the following distinct characters: eye mound notably pronounced apically, spiniform; dorsum with granulations, sparsely covered with setae (Fig. 21); mesal margin of the pedipalpal tibia convex; mesodistal tubercle without basal bulge; setae ornamentation of the tarsus (Figs. 18–20); and cheliceral dentition different from the two new species described herein. Furthermore, the penis of P. granulatum, is very distinct from P. pickardcambridgei sp. nov. and P. tzotzil sp. nov.: the lateral setae are arranged in two rows with (basal and lateral), more 14 big spiny slightly spatulate setae (more than on P. pickardcambridgei sp. nov.), and the twin apices of the bilobular projection are turned distally, making a “W” shape (Figs. 37–42). Male genitalia of P. granulatum are more similar to P. veracruz but differ in the number of lateral setae, the distal margin of pars distalis and the shape of the bilobular projection. The presence of one pair of dorsal microsetae on the penis is known only in P. t z o t z i l sp. nov. The male genitalia of P. pickardcambrigei sp. nov. are similar to Paramitraceras hispidulum Pickard-Cambridge, 1905 from Chiapas (illustrated by Šilhavý, 1974) but with fewer lateral setae and differing in the shape of the distal margin (concave in P. hispidulum).
The habitus of Paramitraceras species are very uniform, which, coupled with the unarmed pedipalps and typical pars distalis of male genitalia, makes the genus easy to recognize within Stygnopsidae. Recognition of its six known species depends on the following characters: 1) shape, ornamentation and sexual dimorphism in the eye mound, 2) the scutum/ cheliceral hand ratio and sexual dimorphism of cheliceral size and dentition, 3) dorsal tubercles, shape, development and density, 4) distal armature and margins of the pedipalpal tibiae, along with setae armature on margins of the pedipalpal tarsus, 5) sexual dimorphism of the ventral tubercles or apophyses in fourth legs, 6) shape of the pars distalis and distal margin of the male penis, 7) arrangement, shape, and density of the lateral setae on the the pars distalis, 8) bilobular projection shape and 9) presence/absence of dorsal microsetae.
The genus most similar to Paramitraceras is Sbordonia Šilhavý, 1977, differing by its smaller size, paler color, presence of setiferous tubercles on pedipalps (armature), and distinct sexual dimorphism of leg IV. Regarding the male genitalia, the only available information is a dorsal drawing of the penis of Sbordonia armigera Šilhavý, 1977 (the type species), which is very similar to the general pattern of the Paramitraceras species. The two described species of Sbordonia are found in Chiapas Mexico, also a undescribed species from Honduras (Mendes and Kury, 2007). Hitherto, the limits of both genera are unknown; unarmed pedipalps are very distinctive in Paramitraceras, but that character is apparently the only difference between those two genera. In the future, a cladistic analysis including characters of the male genitalia should clarify the relationships between Paramitraceras and Sbordonia.
description: Published as part of Cruz-López, Jesús A. & Francke, Oscar F., 2013, Two new species of the genus Paramitraceras Pickard-Cambridge, 1905 (Opiliones: Laniatores: Stygnopsidae) from Chiapas, Mexico, pp. 481-490 in Zootaxa 3641 (4) on pages 4-8, DOI: 10.11646/zootaxa.3641.4.13, http://zenodo.org/record/219410