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

publication ID	https://doi.org/ 10.5281/zenodo.175540
DOI	https://doi.org/10.5281/zenodo.5618796
persistent identifier	https://treatment.plazi.org/id/B2530A1A-FFE7-FFB5-C7C0-166EFA391E9A
treatment provided by	Plazi
scientific name	Pilbarascutigera
status	gen. nov.

Treatment

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 View FIGURES 37 – 44 , 68 View FIGURES 64 – 69 ), 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 View FIGURES 37 – 44 ).

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 View FIGURES 61 – 63 ). 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 View FIGURES 61 – 63 ) or almost transverse ( Fig. 63 View FIGURES 61 – 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 View FIGURES 3 – 4 , 21 View FIGURES 21 – 28 ) 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 View FIGURES 64 – 69 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 View FIGURES 53 – 60 ), less elaborate than the variably pointed ( Fig. 66 View FIGURES 64 – 69 ) or projecting end in Thereuopoda (see Würmli 1979, figs. 13–22 for variability in shape of the subanal plate in Thereuopoda ).

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

Pilbarascutigera and Thereuopoda View in CoL 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 View FIGURES 53 – 60 ). Likewise, in Thereuopoda View in CoL sensilla are arranged two-deep ( Verhoeff 1937, pl. 22, figs. 56, 58, 60; Verhoeff 1939, fig. 2; Fig. 70 View FIGURES 70 – 75 herein) along most or all the length of the metarthron or are even more densely scattered ( Verhoeff 1943, fig. 4). In contrast, in Thereuonema View in CoL , the sensilla are arranged in a single row along the length of the metarthron ( Verhoeff 1936, fig. 5; Fig. 71 View FIGURES 70 – 75 herein), and this single-row arrangement can be confirmed in Allothereua View in CoL ( Fig. 73 View FIGURES 70 – 75 ) and Thereuopodina View in CoL ( Fig. 72 View FIGURES 70 – 75 ), as well as non-thereuonemines such as Scutigera View in CoL ( Fig. 74 View FIGURES 70 – 75 ) and members of the Scutigerinidae View in CoL ( Fig. 75 View FIGURES 70 – 75 ). All scutigeromorphs examined also have a row of sensilla along the outer margin of the metarthron ( Fig. 72 View FIGURES 70 – 75 ). 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 View in CoL .

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 View FIGURES 13 – 20 ), in contrast to the condition in Thereuopoda View in CoL , Thereuopodina View in CoL and Allothereua View in CoL , 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 View in CoL ). Other scutigeromorphs have more uniformly conical spines (e.g., Prothereua annulata: Koch & Edgecombe 2006 View in CoL , fig. 7d).