Dicellophilus anomalus, (CHAMBERLIN, 1904)

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 : 516-520

DICELLOPHILUS ANOMALUS ( CHAMBERLIN, 1904)

Mecistocephalus anomalus Chamberlin, 1904 . Original description: Chamberlin, 1904: 655. Type locality: ‘Pacific Grove, California’ [= Pacific Grove ( USA, California)]. Type material: holotype male, 22 mm long, in the Museum of Comparative Zoology, Cambridge, USA (code number 1042).

Main references for morphology: Chamberlin, 1904: 655 (original description); Chamberlin, 1912: 653 (redescription); Silvestri, 1919: 83 (redescription).

Diagnosis: A Dicellophilus species with 41 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 2 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. 2E ). Sensilla on the antennal tip usually with a crown-like projection at about mid-length. Head ( Fig. 2A ) ~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. 2C ) forming an angle pointing forwards. Clypeus ( Fig. 2D ): lateral margins converging backwards; a wide subtriangular posteromedial area without setae, but with a distinctly isolated posteromedian pair of setae. Posterior margin of each labral side piece usually also concave on its medial part. Non-areolate part of the buccae ( Fig. 2D ) extending forwards distinctly beyond the labrum. Mandible with between five and seven pectinate lamellae. Coxosternum of maxillae I ( Fig. 2B ) less than 3.0 times as wide as medially long. Medial projection of maxillae I more than 2.0 times as long as wide; distal hyaline part enlarged, subtriangular; hyaline scales present on the dorsal surface ( Fig. 2H ). 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. 2B ). Condylar processes of the forcipular coxosternum ( Fig. 2I ) well developed. Forcipular article I 1.2–1.3 times as long as wide, the tubercle relatively large, usually projecting beyond the distal margin of the article ( Fig. 2F ). 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. 2G ) wider than long. Posterior end of coxopleura usually distinctly pointed.

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

Notes on taxonomy: Originally included in the genus Mecistocephalus Newport, 1843 ( Chamberlin, 1904), the species was moved to Dicellophilus by Silvestri (1919), followed by subsequent authors. After the original description, additional specimens were only recorded by Chamberlin (1912) and Silvestri (1919).

Even though D. anomalus was maintained as a valid species by most authors, it was cited as a junior synonym of D. carniolensis by Attems (1929), followed by other authors ( Matic, 1972; Kevan, 1983; Mikoš 1991). Most probably Attems relied on the influential redescription provided by Silvestri (1919), where the number of leg-bearing segments was given erroneously as 43 instead of 41 (see below).

Worth noting is that the two specimens examined by us (see Material and methods) are topotypic, and were sent by R. V. Chamberlin as a gift to the French myriapodologist H. Ribaut. The holotype is currently preserved at the Museum of Comparative Zoology , Cambridge (L. Leibensperger, pers. comm.) .

D. anomalus D. carniolensis D. limatus D. pulcher

Antenna length/head width ~4 ~3 ~4

Antenna, width of article XIV/width <0.5 ~0.5 <0.5

of article I

Antenna, article XIV, length/width 2.2–2.4 1.7–2.0 2.2–2.4

Antenna, length of article XIV/length <1.5> 1.5 <1.5

of article XIII

Antenna, setae, maximum length ~300 Mm 150–200 Mm ~300 Mm

Antenna, apical sensilla, crown-like Usually present Absent Usually present projection

Cephalic plate, length/width 1.5–1.6 1.2–1.4 1.5–1.6

Cephalic plate, lateral margins, shape Almost straight, evidently Markedly convex, Almost straight, evidently converging for most of evidently converging converging for most of the length only for the posterior the length part

Cephalic plate, frontal line, shape Angle pointing forwards Uniformly rounded Angle pointing forwards Clypeus, lateral margins, shape Evidently converging Only slightly converging Evidently converging posteriorly posteriorly posteriorly

Clypeus, setae on a central triangular Absent Present Absent area

Clypeus, distinctly isolated Present Absent Present posteromedian pair of setae

Bucca, non-areolate part, anterior Evidently overreaching the Not or only slightly Evidently overreaching the extent labrum overreaching the labrum labrum

Mandible, pectinate lamellae, number 5–7 3–5 5–7

maxillae I, coxosternum, 2.6–3.0 3.3–3.5 2.6–3.0

width/medial length

Maxillae I, medial projection, length/ 2.0–2.5 0.5–1.5 2.0–2.5

width

Maxillae I, medial projection, distal Evidently enlarged Only slightly enlarged Evidently enlarged hyaline part, shape distally, subtriangular distally, not distally, subtriangular subtriangular

~3

<0.5

2.2–2.4

<1.5

150–200 Mm

Usually present

1.2–1.4

Markedly convex, evidently converging only for the posterior part

Uniformly rounded

Evidently converging posteriorly

Absent

Absent

Evidently overreaching the labrum

5–7

2.6–3.0

2.0–2.5

Evidently enlarged distally, subtriangular Maxillae I, medial projection, dorsal Present Absent Present hyaline scales

Maxillae I, telopodite, length of the ~1.5 ~1.0 ~1.5

distal hyaline part/length of the basal chitinous part

Maxillae II, telopodite, distal article, Subconical, tapering Subcylindrical for most Subconical, tapering shape gradually along most of of the length, gradually along most of the length tapering abruptly in the length the distal part

Maxillae II, telopodite, distal article, 1.3–1.6 1.8–3.5 1.3–1.6

length/width

Forcipular segment, coxosternum, Well developed Virtually lacking Well developed condylar processes

Forcipular segment, 1.2–1.3 1.2–1.3 1.2–1.3 trochanteropraefemur, length/width forcipular segment, Large, greatly projecting Small, not or only Large, greatly projecting trochanteropraefemur, distal tubercle, beyond the distal slightly projecting beyond the distal relative size in respect to the article margin of the article beyond the distal margin of the article margin of the article

Forcipular segment, tarsungulum, basal Well developed Virtually lacking Well developed tubercle

Forcipular segment, tarsungulum, Weak, uniformly spaced Weak, uniformly spaced Weak, uniformly spaced marginal crenulation, shape notches notches notches

Leg-bearing segments, number 41 43 45

Last leg-bearing segment, sternum, 0.8–0.9 1.0–1.2 0.8–0.9

length/width

Last leg-bearing segment, coxopleuron, Usually distinctly pointed Rounded Usually slightly pointed posterior end, shape

Present

~1.5

Subconical, tapering gradually along most of the length

1.3–1.6

Well developed

1.0

Small, not or only slightly projecting beyond the distal margin of the article

Well developed

Evident, variably spaced notches

41

1.0–1.2

Usually slightly pointed Notes on morphology: The number of leg-bearing segments was reported as 43 by Silvestri (1919), but this was probably a mistake, as suggested by the fact that Silvestri (1919) did not comment upon this discrepancy, even though the number had been reported consistently as being invariantly 41 for the species ( Chamberlin, 1904, 1912), and intraspecific invariance in the number was taken for granted for all mecistocephalid species at that time (Bonato et al., 2002).

Apart from the number of trunk segments, two other characters were listed as being different between D. anomalus and D. limatus , namely body size ( D. anomalus was described as being smaller than D. limatus , according to Chamberlin, 1904) and antennal length (shorter in D. anomalus than in D. limatus , according to Chamberlin, 1912). However, Chamberlin’s evaluation of the body size of D. limatus was obviously based on a single specimen that was not fully grown, as suggested by the pattern of coxal pores described. Furthermore, our morphometric analyses of representative specimens of both species did not confirm any significant difference in the elongation of the antennae in respect to the head, nor in the elongation of the articles ( Table 3). Also, the body colour was described as slightly different between the species ( Chamberlin, 1904, 1912), but it is expected to be obviously affected by the condition of preservation and the treatment of the specimens, as acknowledged for D. limatus by Wood (1862, 1865).

Distribution: The species occurs in a restricted area in the south-western part of North America, between the Pacific Coast Ranges and the Cascade Range and Sierra Nevada, from central California to Oregon ( Fig. 10 ). It has been recorded in only a few localities, in particular around Monterey Bay, near Pacific Grove, California ( Chamberlin, 1904, 1912), at Oroville, California ( Chamberlin, 1912), and at Lebanon, Oregon ( Silvestri, 1919).

Figures

Figure 2. Dicellophilus anomalus. 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: ♀, 45-mm long, from Pacific Grove, California; the detailed data for the specimen 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.