Dicellophilus limatus, (WOOD, 1862)

Bonato, Lucio, Dányi, László & Minelli, Alessandro, 2010, Morphology and phylogeny of Dicellophilus, a centipede genus with a highly disjunct distribution (Chilopoda: Mecistocephalidae), Zoological Journal of the Linnean Society 158 (3), pp. 501-532 : 522-523

DICELLOPHILUS LIMATUS ( WOOD, 1862)

Mecistocephalus limatus Wood, 1862 . Original description: Wood, 1862: 42. Type locality: ‘California’ (no more precise locality given). Type material: three syntypes, sex and developmental stage unknown; originally deposited in the collections of the Smithsonian Institution, Washington, DC (code number 310), but current repository unknown; possibly lost.

= Mecistocephalus breviceps Meinert, 1886 . Original description: Meinert, 1886b: 214. Type locality: ‘Nantucket, Mass.’ [= Nantucket (Massachusetts, USA)]. Type material: holotype male, adult, in the Museum of Comparative Zoology, Cambridge, USA (code number 310). Synonymy by Chamberlin, 1920: 186.

Main references for morphology: Wood, 1862: 42 (original description); Wood, 1865: 177 (diagnosis); Meinert, 1886b: 214 (redescription as M. breviceps ); Chamberlin, 1912: 653 (redescription); Attems, 1929: 147 (diagnosis and key).

Diagnosis: A Dicellophilus species with 45 leg-bearing segments. Antennae about four times as long as the maximum width of the head, strongly tapering (width of the terminal article less than half of the width of article I); terminal article more than two times as long as wide, and less than 1.5 times as long as article XIII. The longest setae on the antennae are ~300-Mm long ( Fig. 4E ). Sensilla on the antennal tip usually with a crown-like projection at roughly mid-length. Head ( Fig. 4A ) ~1.5–1.6 times as long as wide. Lateral margins of the cephalic plate almost straight, evidently converging for most of their length. Frontal line ( Fig. 4C ) forming an angle pointing forwards. Clypeus: lateral margins converging backwards; a wide subtriangular posteromedial area without setae, but with a distinctly isolated posteromedian pair of setae. Non-areolate part of the buccae ( Fig. 4D ) extending forwards distinctly beyond the labrum. Mandible with between five and seven pectinate lamellae. Coxosternum of maxillae I ( Fig. 4B ) less than 3.0 times as wide as medially long. Medial projection of maxillae I more than two times as long as wide; distal hyaline part enlarged, subtriangular; hyaline scales present on the dorsal surface ( Fig. 4H ). Distal hyaline part of the telopodite of maxillae I distinctly longer than the basal chitinous part. Distal article of the telopodite of maxillae II subconical, tapering gradually along most of its length, ~1.5 times as long as wide ( Fig. 4B ). Condylar processes of the forcipular coxosternum ( Fig. 4I ) well developed. Forcipular article I 1.2–1.3 times as long as wide, the tubercle relatively large, and greatly projecting beyond the distal margin of the article ( Fig. 4F ). Forcipular tarsungulum with evident basal tubercle, the dorso-internal margin only weakly crenulated, with uniformly spaced notches. Sternum of the last leg-bearing segment ( Fig. 4G ) wider than long. Posterior end of coxopleura usually indistinctly pointed.

The main differential characters with respect to the other Dicellophilus species are presented in Table 3.

Notes on taxonomy: Originally included in the genus Mecistocephalus Newport, 1843 ( Wood, 1862), the species was separated in a distinct genus Dicellophilus by Cook (1896a), but this generic assignment has only been adopted universally since the 1950s. The name was occasionally misspelled as lineatus ( Wood, 1865: plate I; Saussure & Humbert, 1872; Verhoeff, 1902 –1925) or limitatus ( Kevan, 1983).

The syntypes of M. limatus were originally deposited in the Smithsonian Institution, Washington, DC ( Wood, 1862, 1865), but there is no evidence that they are still there (D. De Roche, pers. comm.).

Mecistocephalus limatus Wood, 1862 was listed as a synonym of Mecistocephalus melanonotus Wood, 1862 by Chamberlin (1912: 661), even though in the same paper, inconsistently, Chamberlin (1912: 653) treated M. limatus as a distinct, valid species, and also listed some of the localities noted for M. melanonotus for M. limatus . The synonymy was confirmed by Chamberlin (1946), but must be rejected, as M. melanonotus has subsequently been demonstrated as not belonging to the Mecistocephalidae ( Crabill, 1950) .

Mecistocephalus breviceps Meinert, 1886 was described by Meinert (1886b) from two specimens (holotype and paratype). The original description was incomplete, and no other specimens have been referred to this nominal species. Cook (1896a) included it in his new genus Dicellophilus , therefore recognizing that it was close to M. limatus . After examining both specimens, Chamberlin (1920) synonymized M. breviceps under D. limatus , followed by subsequent authors ( Attems, 1929; Kevan, 1983). Even though the original description of M. breviceps was obscure, and apparently inconsistent at some points with the morphology of D. limatus (particularly in the elongation of the forcipules, the putative presence of tubercles on the forcipular coxosternum, the width of the forcipular tergum, and the shape of the sternum of the last leg-bearing sternum), the provenance of the specimens is outside the known geographical range of D. limatus (see below), and the identity of D. limatus could have been misunderstood by R.V. Chamberlin (see above), after directly examining both the holotype and paratype, we can confirm that they are both fully consistent with D. limatus , in all characters recognized here as being diagnostic for the species, and therefore confirm that M. breviceps is actually a junior synonym of D. limatus .

Notes on morphology: In describing the three syntypes, the number of pairs of legs was given by Wood (1862, 1865) as ‘43–44’ and this value was subsequently interpreted by Chamberlin (1904) as 43. However, 45 pairs of legs are unambiguously recognizable in the only specimen illustrated by Wood (1865), and an invariant number of 45 pairs has been found in all other specimens examined so far ( Chamberlin, 1912; L. Bonato, pers. observ.), and has been maintained by all authors since then (e.g. Attems, 1929, 1947; Verhoeff, 1934). Worth noting is that H.C. Wood often gave approximate estimates of the number of leg pairs of geophilomorphs in his papers, usually not counting the last pair, which were often very distinct from the other pairs.

Distribution: The species occurs naturally in a restricted area in the south-western part of North America, along the Pacific Coast Range of central and southern California, in particular around the San Francisco Bay and close to Los Angeles ( Fig. 10 ). It has been recorded in at least half a dozen localities, namely Mill Valley, Sausalito, Berkeley, Stanford, Claremont ( Chamberlin, 1912), and Sonoma (L. Bonato, pers. obs.).

Notes on distribution: Dicellophilus limatus has been recorded from three localities in eastern North America ( Fig. 10 ), but no compelling evidence exists to indicate that the species actually lives outside of the restricted range in California. Wood (1862, 1865) stated that both the holotype and paratype of M. breviceps (actually identical to D. limatus ; see above) were collected from Nantucket Island, along the coast of Massachusetts, but such a locality is not reported on the labels associated with the specimens, and are only noted in a catalogue, and therefore the actual provenance of the specimens remain dubious, as already highlighted by Chamberlin (1920). Meyer (1937) reported to have collected several specimens of D. limatus at Cedar Glade, near Nashville, Tennessee, but the identification is possibly unreliable, as intimated by R.E. Hefner (see Notes on distribution, for Dicellophilus ) and no other specimens have been recorded in that or neighbouring states by other authors (e.g. Bollman, 1888; Chamberlin, 1921). A specimen preserved in the collections of the Smithsonian Institution, Washington, DC (USNM 2046777), and labelled as ‘ Florida: Miami (Chapman Field)’ has been examined by us, and found to be fully consistent with D. limatus in all characters here recognized as being diagnostic of the species; it is worth noting that an associated label documented that it had already been examined by R.E. Crabill, who indicated it as resembling D. limatus ; however, no other specimen of Dicellophilus has ever been collected in Florida, despite the relatively extensive sampling in that state (e.g. Mc Neill, 1887; Cook, 1899; Chamberlin, 1958; Corey, 1988; Corey & Stout, 1992).

Figures

Figure 4. Dicellophilus limatus. A, head, dorsal view. B, right part of the maxillary complex, ventral view (detached from head). C, anterior part of head, dorsal view. D, clypeus and labrum, ventral view (maxillae removed). E, left antennal articles III–V, dorsal view. F, internal margin of left forcipule, dorsal view. G, last leg-bearing segment of an adult female, ventral view. H, left telopodite and medial projection of maxillae I, dorsal view (detached from head). I, left condylar process of forcipular coxosternum, dorsal view (head removed). Microscopic photographs and line drawings: A, B, E, ♀, 49-mm long, from Berkeley, California; C, D, F–H, ♀, 68-mm long, from Berkeley, California; the detailed data for the specimens are presented in the Material and methods.

Figure 10. Geographical distribution and phylogenetic relationships of the species of Dicellophilus. The shaded areas indicate the established populations; stars indicate either occasional or dubious records. The dotted line indicates the 40 °N parallel of latitude.