Tylorida striata (Thorell, 1877)

Dimitrov, Dimitar, Álvarez-Padilla, Fernando & Hormiga, Gustavo, 2008, Until dirt do us apart: On the unremarkable palp morphology of the spider Sternospina concretipalpis Schmidt & Krause, 1993, with comments on the genus Prionolaema Simon, 1894 (Araneae, Tetragnathidae), Zootaxa 1698, pp. 49-56 : 51

Tylorida striata (Thorell, 1877)

( Fig. 1 A–D)

Meta striata Thorell, 1877b: 427

Meta striata Hasselt, 1882: 25 .

Argyroepeira bigibba Thorell, 1887: 140 .

Argyroepeira s. Thorell, 1887: 142.

T. striata Simon, 1894a: 737 , f. 809.

Argyroepeira s. Workman & Workman, 1894: 19, pl. 19. T. magniventer Bösenberg & Strand, 1906: 187 , pl. 15, f. 397. T. striata Bösenberg & Strand, 1906: 187 , pl. 15, f. 420. Sternospina concretipalpis Schmidt and Krause, 1993: 7 , f. 1. New synonymy N.B. See Platnick (2008) for complete list of citations.

Types. Tylorida striata: The location of the Thorell’s type is uncertain but most likely it is deposited in the Natural History Museum of the city of Geneva (Levi, unpublished notes) – not examined. Sternospina concretipalpis : male holotype from the Comoros Islands, Grande Comore, Boboni, 625 m, 28.xi.1983, R. Jocqué (RMCA 160.838, examined).

Justification of the transfer: Detailed study of the S. concretipalpis type shows that this specimen has all diagnostic characteristics of T. striata , including the shape of the conductor and embolus, the spermatic duct path, the shape of the paracymbium and the cymbium dorso-basal process ( Fig. 1 A–B). Although we did not examine the type of T. striata , there are numerous good illustrations of this species available in the literature to facilitate identification (e.g., Chrysanthus, 1963; 1975; Davies, 1998; Tanikawa, 2004). The palpal fusion mentioned by Schmidt and Krause (1993) proved to be a misinterpretation, probably as a result of the bad condition of the specimen. The two palps are not fused, but one of them lacks the cymbium together with the tegular and embolic divisions (see below). Based on these observations, we transfer S. concretipalpis to Tylorida and as a consequence the former genus becomes a junior synonym of Tylorida .

Another three species of Tylorida have distribution ranges close (or including) the Comoro Islands: T. ventralis (Thorell, 1877) , T. culta ( O. P.-Cambridge, 1869) and T. mornensis (Benoit, 1978) . The three of them, however, have very different spermatic duct paths. Additionally, T. culta differs in having an elongated and mostly cylindrical abdomen while T. mornensis has a distinctive dark marking on the abdomen.

In the original description of S. concretipalpis , the authors claim that both palps are fused; if true this would be unique among spiders, as such a remarkable morphological feature has never been described for a spider (or any other arachnid, for that matter). Detailed study of the only available specimen indicates that this statement was a misinterpretation. The right palp of the specimen is broken and is missing all sclerites distal to the tibia ( Fig. 1 C–D). The left palp is slightly damaged (the tegulum is partially broken) but all structures can be observed ( Fig. 1 A–D). Several cotton fibers were holding the remains of the right palp to the cymbium of the left one, thus superficially giving the impression that both are connected, but careful examination of the specimen after removing the cotton fibers demonstrated that the two palps are not more fused together than they are in any other spider species.

The record of T. striata on the Comoro Islands broadens considerably westwards the known distribution range for this species which is known from China to Australia. This distribution is quite unusual considering the fact that there are no records of this species from the Indian peninsula. The disjunction may be an artifact resulting from fragmentary knowledge of the real geographic distribution of T. striata .

Figures

FIGURE 1. Tylorida striata (Thorell, 1877), male palps (Schmidt and Krause’s S. concretipalpis holotype): A, left, ventral. B, left palp before separating it from the remains of the right palp, retrolateral. C, close up of right palp tibia, retrolateral (arrow points to the distal edge of the right tibia missing the cymbium). D, left palp, retrolateral (left femur labeled by right pointing arrow; femur of incomplete righ palp labeld by left pointing arrow). Scale bars 0.5.