Stenotaenia romana, (SILVESTRI, 1895)

Bonato, Lucio & Minelli, Alessandro, 2008, Stenotaenia Koch, 1847: a hitherto unrecognized lineage of western Palaearctic centipedes with unusual diversity in body size and segment number (Chilopoda: Geophilidae), Zoological Journal of the Linnean Society 153 (2), pp. 253-286 : 272-273

STENOTAENIA ROMANA ( SILVESTRI, 1895)

Geophilus romanus Silvestri, 1895: 194 (original description). Attems, 1903: 221 (in key); 1929a: 161 (in key), 179 (redescription); 1947: 112 (in key). Minelli, 1983a: 8 (redescription).

Geophilus (Notadenophilus) silvestrii Verhoeff, 1928: 269 (original description), figs 28–29. Nesogeophilus silvestrii: Attems, 1929a: 359 (redescription). Syn. nov.

Type locality: ‘ Roma ( Villa Pamphyli )’ = Villa Doria Pamphili, in Rome ( Italy) .

Type material: Syntypes (number unknown), of both sexes, up to 16-mm long; held in the Museo civico di Storia naturale, Genova, without catalogue number.

Diagnosis: A Stenotaenia species of small body size (total length not reaching 2 cm); c. 43–49 leg-bearing segments; labrum with about one or two tubercles; first maxillae without distinct lappets on both the coxosternum and the telopodites; chitin lines of the forcipular coxosternum not reaching the anterior condyles; anterior margin of the forcipular coxosternum angulated; forcipular intermediate articles distinct; sternal pore areas in the anterior part of the trunk oval, longer than wide, and placed on the posterior half of each sternum; each coxopleuron with one anterior pouch with pores and one posterior single pore or a pouch with very few pores (see also Table 3).

Taxonomic history: After the original description by Silvestri (1895) the true identity of this species remained uncertain until Minelli’s (1983a) account, based upon the examination of the type material. Geophilus romanus was recorded from other Italian localities ( Minelli, 1983a, 1992; Minelli & Zapparoli, 1985, 1992), but its assignment to the genus Geophilus was never questioned.

Assignment to Stenotaenia: It is assigned confidently to Stenotaenia (comb. nov.), based on the original description, as emendated by Minelli (1983a) (Table 2), as well as on the examination of representative specimens from throughout the known range ( Figs 3 , 5 ). This species shares all major diagnostic characters of the genus, including the shape of the labrum, the features of the maxillary complex and the mandibles, the general shape of the forcipular segment, the pattern of sternal pore areas and of the coxal pores, and the features of the legs of the last pair. It is worth noting that Silvestri’s (1895) original description was inaccurate in recognizing only a single pore on the internal ventral side of each coxopleuron, whereas an anterior pouch is also invariantly present, as demonstrated by Minelli (1983a) in the type material, and confirmed by our original observations in other specimens. The affinity between S. romana and S. linearis was already acknowledged ( Silvestri, 1895; Minelli, 1992), and indeed S. romana was even suspected by Verhoeff (1928) to represent just a juvenile stage of S. linearis .

Validity: It is recognized here as a very distinct species: distinguished from all other known species of Stenotaenia for the smaller body size, the lower number of trunk segments, the apparent incompleteness of the chitin lines, and the presence of an anterior pouch of coxal glands and a posterior single large pore on each coxopleuron, even in full grown specimens, which is possibly a paedomorphic trait ( Table 3).

Remarks on synonyms

Geophilus (Notadenophilus) silvestrii Verhoeff, 1928 . Geophilus silvestrii was described by Verhoeff (1928) from a single male from near Rome, and another specimen was later identified by the same author from Mt Argentario, along the Tyrrhenian coast ( Verhoeff, 1934a). Its possible synonymy under S. romana has already been claimed ( Minelli, 1983a; Foddai et al., 1995). According to the detailed original description, G. silvestrii agrees fully with S. romana , especially in body size, the number of trunk segments, and other major traits in the forcipular segment, the sternal pore areas, the coxal pores, and the last pair of legs. Furthermore, the type localities of the two nominal species are only a few kilometres apart. The only putative diagnostic difference is in the elongation of the head, but the length-to-width ratio given by Verhoeff for G. silvestrii is hardly correct, as it is outside the known range of all Geophilus or Stenotaenia species. Therefore, we are confident in recognizing G. silvestrii as a junior synonym of S. romana .

Distribution: It occurs mainly along the Italian Peninsula, most frequently on the Tyrrhenian side from Liguria to Campania, including some minor islands, namely Elba, Giglio, and Ischia (new localities, see Appendix; M. Zapparoli, pers. comm.). It also occurs in Sardinia ( Minelli, 1983a), in the western Alps ( Minelli & Zapparoli, 1992), on the Euganean Hills (Minelli, 1992), and on Mt Conero along the Adriatic coast (new localities, see Appendix) ( Fig. 3 ).

Figures

Figure 3. Geographical distribution of Stenotaenia frenum, Stenotaenia romana, and Stenotaenia sturanyi. Both previously published and new records have been plotted upon a grid of 30′ latitude ¥ 30′ longitude.

Figure 5. Microscopic images of a female specimen of Stenotaenia romana (Silvestri, 1895) from Isola del Cantone near Genova (Italy: Liguria) (12-mm long, with 47 leg-bearing segments; 5-XI-1978 Gardini lg, collection A. Minelli): (a) head, ventral; (b) clypeus and maxillary complex, ventral; (c) sternum of leg-bearing segment X; (d) forcipular segment, ventral.