Pilbarascutigera, Edgecombe, Gregory D. & Barrow, Lauren, 2007

Edgecombe, Gregory D. & Barrow, Lauren, 2007, A new genus of scutigerid centipedes (Chilopoda) from Western Australia, with new characters for morphological phylogenetics of Scutigeromorpha, Zootaxa 1409, pp. 23-50 : 25-26

Pilbarascutigera n. gen.

Type species: Allothereua incola Verhoeff, 1925

Diagnosis: Thereuonemine with predominantly orange-brown pigmentation; anterior tergal plates having scattered setiform bristles (Stachelborsten sensu Verhoeff 1925) and slender, needle-like bristles (Tastborsten sensu Verhoeff) but lacking spines; TT5–7 (and TT 3–4 in some specimens) with numerous spines, each paired with a Tastborste, along each side of midline, on stoma saddles, and on lateral parts of tergal plates; tergal spicula short, triangular, relatively sparse; anterior projection of cephalic sutures short, parallel; stoma saddles weakly vaulted; sinus between inner margins of mesarthron of female gonopod broad, parabolic to almost rectangular; margins of metarthron relatively straight in ventral view; female subanal plate drop-shaped, with blunt, rounded distal end; spines in lateral cluster on clypeal part of epipharynx uniformly elongate, slender.

Etymology: Compounding Pilbara , and the usual scutigeromorph suffix - scutigera .

Discussion: Allothereua incola Verhoeff, 1925 , differs from other species of Allothereua in having relatively sparse, short spicula ( Verhoeff 1925, pl. 1, fig. 8), slender, needle-like bristles paired with the spines on the tergal plates (especially TT5–7), and a relatively wide sinus between the inner margins of the mesarthron of the female gonopod ( Verhoeff 1925, pl. 1, fig. 1). Verhoeff (1925) distinguished the fine bristles in paired association with a spine as “Tastborsten” ( Figs. 42, 44 , 68 ), in contrast to the thicker bristles described by Verhoeff as “Stachelborsten” that are paired with a spine in Allothereua ( Edgecombe & Giribet 2006, fig. 4B). In Allothereua from southern parts of Australia, the spicula are variably setiform ( Edgecombe & Giribet 2006, fig. 4B), as in Parascutigera from New Caledonia ( Edgecombe & Giribet 2006, fig. 4D), rather than short and triangular as in Pilbarascutigera ( Figs. 42, 43 ).

The female gonopod of the types of Pilbarascutigera incola ( Verhoeff 1925, pl. 1, fig. 1) is matched by many specimens from the Pilbara region ( Fig. 62 ). However, the parabolic sinus between the mesarthron inner margins in these specimens is at one end of a range of variation found in the Pilbara samples, and other specimens, irrespective of size, have a relatively wider sinus with an angular ( Fig. 61 ) or almost transverse ( Fig. 63 ) proximal part that significantly differs from the narrow, parallel-sided sinus in species of Allothereua and Parascutigera . As was recognized in Verhoeff’s (1925, p. 8) key to genera of Thereuoneminae, the wider sinus is shared with Thereuopoda and Thereuopodina , two genera that also occur in northern Australia.

Distinction of Pilbarascutigera and Thereuopoda is straightforward, the former having weakly (versus strongly) vaulted stoma saddles, much shorter spiracles, an absence of spines on the anterior tergal plates (consistent absence on T1; usually absent on T2 and sometimes absent on T3 and T 4 in P. incola ), and the first appearance of spines on the stoma saddle of TT3, 4 or 5 (versus first appearance on TT1 or 2 in Thereuopoda , with consistent abundance on T2). Pilbarascutigera has shorter cephalic sutures ( Figs. 3, 4 , 21 ) than the two valid species of Thereuopoda fide Würmli (1979), and the sutures lack an outward kink (cf. Verhoeff 1937, pl. 20, fig. 48; Verhoeff 1939, figs. 1, 5; Würmli 1979, fig. 25). Pilbarascutigera has relatively elongate setae on the ventral side of the leg 15 tarsus, in contrast to the short, spine-like setae in this position in Thereuopoda ( Murakami 1971, fig. 3G). Pilbarascutigera also lacks spines that are found on the proximal half of the first antennal flagellum in Thereuopoda ( Murakami 1971, fig. 3C; Figs. 64, 65 herein). The metarthron of the female gonopod in Pilbarascutigera is less curved than in Thereuopoda (see, e.g., Verhoeff 1943, fig. 4; Unsöld & Melzer 2003, fig. 2G–I for T. longicornis ) or Thereuopodina . The subanal plate of the female has a blunt, rounded distal end in Pilbarascutigera ( Fig. 53 ), less elaborate than the variably pointed ( Fig. 66 ) or projecting end in Thereuopoda (see Würmli 1979, figs. 13–22 for variability in shape of the subanal plate in Thereuopoda ).

Thereuopoda resembles Pilbarascutigera in having Tastborsten paired with the spines on the posterior tergal plates ( Fig. 68 for Thereuopoda longicornis ; Murakami 1971, fig. 3A for T. clunifera ). Thereuopodina (e.g., T. queenslandica : Fig. 69 ) resembles Thereuonema ( Würmli 1975, figs. 5, 15; Edgecombe & Giribet 2006, fig. 2F) and Allothereua in having relatively thicker bristles paired with the spines, as is also shared by non-thereuonemines such as Scutigera ( Edgecombe & Giribet 2006, fig. 2E). The triangular shape of the spicula in Pilbarascutigera is shared by Thereuopoda ( Verhoeff 1937, pl. 23, fig. 64) and Thereuopodina ( Fig. 69 ). Thereuopodina also has more vaulted stoma saddles than does Pilbarascutigera , approaching the condition seen in Thereuopoda .

Pilbarascutigera and Thereuopoda unite to the exclusion of other scutigeromorph taxa in the distribution of sensilla coeloconica on the metarthron of the female gonopod. In Pilbarascutigera incola these sensilla are scattered two-deep along the ventral surface of the metarthron ( Fig. 58 ). Likewise, in Thereuopoda sensilla are arranged two-deep ( Verhoeff 1937, pl. 22, figs. 56, 58, 60; Verhoeff 1939, fig. 2; Fig. 70 herein) along most or all the length of the metarthron or are even more densely scattered ( Verhoeff 1943, fig. 4). In contrast, in Thereuonema , the sensilla are arranged in a single row along the length of the metarthron ( Verhoeff 1936, fig. 5; Fig. 71 herein), and this single-row arrangement can be confirmed in Allothereua ( Fig. 73 ) and Thereuopodina ( Fig. 72 ), as well as non-thereuonemines such as Scutigera ( Fig. 74 ) and members of the Scutigerinidae ( Fig. 75 ). All scutigeromorphs examined also have a row of sensilla along the outer margin of the metarthron ( Fig. 72 ). These data suggest that a single row of sensilla on the ventral surface is plesiomorphic relative to the proliferation of sensilla in Pilbarascutigera and Thereuopoda .

A distinctive morphology of spines on the clypeal part of the epipharynx is seen in P. i n c o l a. The spines in the lateral cluster are uniformly elongate and slender ( Fig. 15 ), in contrast to the condition in Thereuopoda , Thereuopodina and Allothereua , in which a group of elongate, slender spines grades into a larger cluster of shorter, conical spines ( Edgecombe & Giribet 2006, fig. 3D for Thereuopoda longicornis ). Other scutigeromorphs have more uniformly conical spines (e.g., Prothereua annulata: Koch & Edgecombe 2006 , fig. 7d).

Figures

FIGURES 37 – 44. Pilbarascutigera incola (Verhoeff, 1925). Tergal prominences. 37, 38, 44, WAM T 69858, female. 37, Tastborsten on lateral part of T 1, scale 10 μm; 38, isolated Tastborste on T 1, scale 2 μm; 44, spine and Tastborste on T 7, scale 3 μm. 39 – 43, WAM T 69859, male. 39, lateral part of T 3, scale 30 μm; 40, medial part of T 5, scale 20 μm; 41, T 6, scale 100 μm; 42, medial part of T 6, showing spines (s), Tastborsten (T) and spicula (sc), scale 10 μm; 43, margin of T 6, scale 10 μm; 44, spine and Tastborste on T 7, scale 3 μm.

FIGURES 64 – 69. Thereuoneminae. 64, 65, Thereuopoda clunifera (Wood, 1862). Two articles from first flagellum of antenna, showing pair of spines, scales 20 μm, 10 μm. 66, 68, Thereuopoda longicornis (Fabricius, 1793). 66, female subanal plate, scale 100 μm; 68, T 7 stoma saddle, showing spines (s) paired with Tastborsten (T), scale 20 μm. 67, 69, Thereuopodina queenslandica Verhoeff, 1925, female subanal plate, scale 100 μm; 69, medial part of T 7, showing spines (s) paired with Stachelborsten (St), and spicula (sc), scale 20 μm.

FIGURES 61 – 63. Pilbarascutigera incola (Verhoeff, 1925). Female gonopods, scale for all 200 μm. 61, WAM T 69862; 62, WAM

FIGURES 3 – 4. Pilbarascutigera incola (Verhoeff, 1925). Pigmentation of head and T 1. 3, WAM T 75216, female; 4, WAM T 69865, male. Scales 100 μm.

FIGURES 21 – 28. Pilbarascutigera incola (Verhoeff, 1925). WAM T 69858, female, except 21, 27, WAM T 69859, male. 21, cephalic sutures, scale 100 μm; 22 – 26, mandible. 22, gnathal edge, scale 30 μm; 23, fringe of pectinate bristles, scale 3 μm; 24, mandibular teeth, scale 10 μm; 25, 26, Haarpolster, with molar plate (m. p.), scales 10 μm; 27, eye and Tömösváry organ (T. O.), scale 20 μm; 28, brush-like setae on inner margin of distal article of telopodite of first maxilla, scale 4 μm.

FIGURES 53 – 60. Pilbarascutigera incola (Verhoeff, 1925). WAM T 69858, female, except 60, WAM T 69859, male. 53, subanal plate, scale 100 μm; 54, 55, setae and hairs on subanal plate, scales 20 μm; 56, syntelopodite of gonopod, showing depression, Grube (G), scale 40 μm; 57, distal end of mesarthron, scale 20 μm; 58, metarthron, scale 30 μm, inset shows sensillum coeloconica on mesarthron, scale 1 μm; 59, sensilla coeloconica on metarthron, scale 2 μm. 60, male gonopods, scale 30 μm.

FIGURES 70 – 75. Ventral surface of metarthron of female gonopod, showing arrangement of sensilla coeloconica. 70, Theureuopoda longicornis (Fabricius, 1793), scale 10 μm; 71, Thereuonema turkestana Verhoeff, 1905, scale 10 μm; 72, Thereuopodina queenslandica Verhoeff, 1925, scale 10 μm; inset shows detail of a sensillum, scale 1 μm; 73, Allothereua maculata (Newport, 1844), scale 20 μm; 74, Scutigera coleoptrata (Linnaeus, 1758), scale 10 μm; 75, Madagassophora hova (Saussure & Zehntner, 1902), scale 30 μm.

FIGURES 13 – 20. Pilbarascutigera incola (Verhoeff, 1925). 13, 14, 16 – 18, WAM T 69858, female. 13, field of branching spines on clypeal part of epipharynx, scale 10 μm; 14, cluster of sensilla on medial clypeal part of epipharynx, scale 2 μm; 16, branching bristles beside median excavation on hypopharynx, scale 6 μm; 17, 18, lateral and distal views of hypopharynx, scales 30 μm, 60 μm; inset shows sensilla on distal tip, scale 1 μm. 15, 19, 20, WAM T 69862, female. 15, lateral cluster of spines on clypeal part of epipharynx, scale 20 μm; 19, distal part of first flagellum of antenna, scale 20 μm; 20, hairs and a single trichoid seta on two articles from proximal part of second antennal flagellum, scale 10 μm.