Platypyga subpetrae, Wilson & Keable, 2002

Wilson, George D. F. & Keable, Stephen J., 2002, New Genera of Phreatoicidea (Crustacea: Isopoda) from Western Australia, Records of the Australian Museum 54 (1), pp. 41-70: 60-66

publication ID 10.3853/j.0067-1975.54.2002.1359

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scientific name

Platypyga subpetrae


Platypyga subpetrae   n.sp.

Figs. 15–22

Type material. HOLOTYPE Ƌ, WAM C 25053 View Materials , bl 15.7 mm (ethanol preserved) hand sieve, G.D.F. Wilson, 8 October 1998, WA-564   . PARATYPES: formalin preserved— AM P60537 View Materials , 53   ƋƋ, 1 indeterminate specimen, as for holotype except, 34°23.4'S 118°03.1'E, spring fed stream at base of scree slope, in silty gravel in pool on stream, hand sieves, pH 6.96, 11.0°C, G. Wilson , R GoogleMaps   . Wetzer & S. Keable, 9 September 1999, WA-603; AM P61460 View Materials   , Ƌ 15.8 mm (dissected for SEM), collection details as for AM P60537 View Materials ; WAM C 25054 View Materials   , Ƌ bl 18.2 mm, Ƌ bl 14.3 mm, Ƌ bl 13.9 mm, collection details as for AM P60537 View Materials   ; ethanol preserved— AM P60538 View Materials , 49   ƋƋ, 5 ♀♀, same collection details as holotype; AM P61457 View Materials   , Ƌ (dissected for SEM), same collection details as holotype; AM P61458 View Materials   , ♀ 7.4 mm (dissected for description, SEM and illustration of pleopods), same collection details as holotype; AM P61459 View Materials   , Ƌ 13.7 mm (dissected for description and also illustration of pleopods), same collection details as holotype; AM P61559 View Materials   , 1 specimen (whole mounted for SEM), same collection details as holotype; AM P60539 View Materials , 49   ƋƋ, collection details as for AM P60537 View Materials   .

Type locality. Spring below Toolbrunup Peak, Western Australia, Australia, 34°23.41'S 118°02.98'E ( GPS), 700m altitude, under rocks in sandy gravel, spring emerging at bottom of large scree slope GoogleMaps   .

Other material. WAM C 23271 View Materials , Ƌ bl 20 mm, Toolbrunup Peak, Stirling Range, Western Australia, 34°23.17'S 118°02.51'E, 1030m altitude (original data indicating Toolbrunup summit), from a southeast facing gully, S. Barrett, Department of Conservation and Land Management ( CALM) GoogleMaps   , 1996; AM P60540 View Materials , 9 ƋƋ, 5 ♀♀, 1 indeterminate specimen, spring in saddle on west side at head of stream running on south side of track, Bluff Knoll, Stirling Range , Western Australia, 34°22'S 118°15'E (map estimate), W.F. Ponder, January 1988 GoogleMaps   .

Etymology. The species name subpetrae   is a Latin genitive singular noun meaning “under a crag or pile of rocks”, referring to the type locality at the base of a scree slope.

and pleotelson; B, head, dorsal view; C,D, pleotelson, dorsal and posterior views. Scale bar 1 mm.

Diagnosis. See generic diagnosis.

Description based on male. Colouration colourless in life, colour variable in specimens preserved in 95% ethanol— from slate grey-brown mottled with white to almost pure white with only slight brown-yellow tinges, gut a translucent turquoise visible through cuticle and particularly through sternites.

Head ( Figs. 15A,B, 16A–C,E) length shorter than width in dorsal view; width 0.89–0.92 pereonite 1 width; lateral profile of dorsal surface smoothly curved; surface smooth and shiny; setae sparse, fine. Eyes bulging dorsolaterally (slight, the eye appears somewhat raised because of the strongly developed mandibular groove underneath it); maximum diameter 0.12–0.2 head depth; oval; orientation of longest axis vertical; ocelli not distinguishable as individual units, pigmentation dark and light (white background with variable black spots). Mandibular groove with acute indentation. Mandibular notch present. Clypeal notch present (weak). Antennal notch shallow, without posterior extension. Pereon ( Figs. 15A, 16A) narrow, width near head width; dorsal surface with scattered roughness and smooth; setae on dorsal surface scattered, fine. Pereonites 2–7 in dorsal view wider than long. Coxal

articulation of pereonites 2–4 nearly fused (lateral suture weak but complete), 5–7 free. Sternal processes absent.

Typhlosole absent, gut round in cross section; hindgut caecae absent. Pleonites ( Figs. 15A, 16A) in dorsal view 2–4 respective lengths more than half the length of pleonite 5, 1–4 relative lengths subequal, 1–4 width 0.85 composite length in dorsal view. Pleotelson ( Figs. 15A,C,D, 21A–C) lateral length 0.11 body length, 0.94 depth; dorsal length 1.2 width; depth 1.48 pereonite 7 depth. Posterior margin without irregular denticulations; median lobe width 0.69 pleotelson width, greatest length 0.05 pleotelson total length; lateral lobes absent; median lobe with 2 robust sensillate setae on one of the cleft pair. Dorsal uropodal ridge terminating at pleotelson margin above uropods (implicit character state: short, weak); without setae. Ventral margin anterior to uropods with robust setae, setae smooth, 3 altogether, posterior seta smaller than anterior adjacent setae (thicker but shorter). Antennula ( Fig. 16C,D) length 0.11 body length, with 12 articles. Tiny aesthetascs on articles 9, 11, 12. Terminal article distally oblique, with 2 or more groups of aesthetascs, length subequal to penultimate article length. Penultimate article length approximately subequal to length of other articles. Distal articles circular. Antenna ( Figs. 15A, 16A,E–G) length 0.37 body length. Flagellum length 0.62 total antenna length, with 18 articles. Propodal article 1 absent. Article 5 longer than article 4, article 6 shorter than articles 4 and 5 combined. Mouthfield ( Figs. 15A, 16B) clypeus consisting of broad bar rounded at mandibular fossae, somewhat asymmetrical, broader on left side and with concave lateral margin, width 0.53 head width. Labrum ventrally semicircular in anterior view, somewhat asymmetrical. Paragnaths ( Fig. 18A) with distolaterally rounded lobes, having medial and lateral setal rows and thickened medial base covered with cuticular spinules. Mandible ( Fig. 17) palp length 0.64 mandible length. Left spine row with 12 spines, 9 of which are bifurcate. Right spine row with 14 spines, 9 of which are bifurcate. Molar process length subequal to width; with 1 tooth. Maxillula ( Fig. 18B,C) medial lobe length 0.82 lateral lobe length; width 0.68 lateral lobe width; with 4 pappose setae; with 2 “accessory” setae, one on distolateral margin and one between central pappose setae, “accessory” setae simple; short weakly setulate seta on distal tip absent. Lateral lobe distal margin with 9 denticulate robust setae, with 5 smooth robust setae; ventral face with 2 plumose setae. Maxilla ( Fig. 18D,E) medial lobe width 1.4 outer lateral lobe width; proximal portion distinctly angled to distal portion; proximal and distal setal rows continuous. Outer lateral lobe length subequal to inner lateral lobe, wider than inner lateral lobe. Maxilliped ( Fig. 18F,G) epipod distal tip truncate. Endite medial margin with 5 coupling hooks on left side, 4 on right side; dorsal ridge with 17 large distally denticulate plumose setae (approximately, very weakly denticulate distally). Pereopod I ( Fig. 19A–D) dactylus length subequal to palm; ventrodistal margin with row of thin scale-like spines, along 0.46 total length; with 1 distal accessory claw; distal accessory spines absent. Propodus dorsal margin proximal region protruding beyond distodorsal margin of carpus. Propodal palm convex to straight, spine-like projections absent; cuticular fringe weakly developed; stout denticulate setae absent; stout robust simple setae basally inflated, 8 altogether (SEM); with 6 elongate broad based setae. Merus dorsal margin projection shelf-like and U-shaped, with numerous elongate simple setae and with 1 or 2 robust simple setae. Pereopods II–III ( Fig. 20A,B) dactylus without spines on ventral margin; with 1 distal accessory claw. Propodus articular plate present. Basis dorsal ridge in cross section angular and produced but not forming distinct plate. Pereopod IV ( Fig. 19E,F) subchelate with major hinges on dactylus-propodus (weakly). Dactylus shorter than propodal palm, or longer than propodal palm (shorter when measured on specimen, longer in SEM). Propodus with 1 broad based seta on ventral margin, shorter than dactylar claw (shorter when measured on specimen, subequal in SEM). Basis dorsal ridge in cross section angular and produced but not forming distinct plate. Pereopods V–VII ( Fig. 20C–F) dactylus with 1 distal accessory claw; spines absent. Propodus articular plate on posterior side of limb present. Basis dorsal ridge not distinctly separated from basis shaft, in cross section angular on pereopod V, produced and forming distinct plate on pereopods VI–VII. Pereopod VII ischium dorsal ridge flange absent. Penes ( Fig. 20E) curved posteriorly; length 0.19 body width at pereonite 7, extending past midline and onto pleonite 1; smooth, lacking setae, distally tapering (broadest medially); distal tip rounded. Pleopod ( Figs. 21E,F, 22) exopods lateral proximal lobes on II–V, medial proximal lobes on II–V. Endopods I–V without setae on margins. Protopods II–V with small medial projections, III–V with lateral epipods; 3–4 coupling hooks on I; lateral margin I with simple and lightly plumose setae, lateral margin II without setae, lateral epipods III–V with simple and lightly plumose setae; medial margin I without slender setae, medial margin/epipods II–V with simple setae.

Pleopod I exopod broadest proximally, distal margin rounded, lateral margin rounded, dorsal surface lacking setae. Pleopod II endopod appendix masculina shaft proximal half ventral shape in cross section concave, not forming tube; basal musculature pronounced; distal tip acutely rounded; with 31 setae on margin, occurring laterally and medially; length 0.5 pleopod length, distal tip extending near to distal margin of endopod. Uropod ( Fig. 21B–D) total length 1.21 pleotelson length. Protopod length 0.51 uropod total length; dorsomedial ridge not produced, margin setae robust and simple; with 1 robust simple seta on distoventral margin. Rami cross-sectional shape flattened on dorsal surface only. Endopod subequal to protopod length, straight-curving dorsally; dorsal margin robust setae placed midlength, 6 robust setae (3 medially, 3 laterally). Exopod length 0.88 endopod length; exopod dorsal margin with 1 robust seta.

Sexual dimorphism, female differences from male. Antennula length 0.1 body length, with 10 articles. Antenna length 0.35 body length; flagellum length 0.65 total antenna length, with 16 articles. Pereopod I dactylus ventrodistal

margin with row of sharp spines, along 0.53 total length; propodus dorsal margin proximal region not protruding beyond distodorsal margin of carpus, propodal palm with stout serrate setae, 8 altogether; stout robust simple setae absent; with 2 elongate broad based setae. Pereopod IV propodus with 2 broad based setae on ventral margin. Uropod total length 1.16 pleotelson length; endopod with 7 robust setae (4 medially, 3 laterally); exopod length 0.72 endopod length.

Remarks. Females of Platypyga subpetrae   n.gen., n.sp. in our two samples (WA-564, WA-603) are rare and smaller than males. These specimens are smaller than the males from WAM C 23271 View Materials or AM P60540 View Materials (Bluff Knoll specimens, W. Ponder collection). The latter collection has larger individuals (greater than 20 mm), with an increased number of robust setae on the terminal lobes of the pleotelson, than the WAM C 23271 View Materials specimen. These larger specimens also differ from the type material in having the uropodal endopod longer than protopod. This feature, however, is not readily discernible without careful measurements. Until further evidence is available, we assume that all material examined is conspecific.

General distribution and habitat. Stirling Range National Park, Western Australia; rocky spring-fed streams flowing from south-facing slopes of the highest peaks of the Range.


Western Australian Museum


Australian Museum


Departamento de Geologia, Universidad de Chile