Skolomystax, Suter & Webb & Gattolliat, 2023

Suter, P. J., Webb, J. M. & Gattolliat, J. - L., 2023, Skolomystax, a new genus for the Australian species formerly included in Centroptilum Eaton (Ephemeroptera: Baetidae), Memoirs of Museum Victoria (Mem. Mus. Vic.) 82, pp. 1-48 : 44-45

Key to nymphs of Skolomystax from Australia

1 Legs with spine-like setae on the outer (dorsal) margins of tibiae and tarsi (figs. 3a, 5c, 20g) 2

1’ Legs lacking spine-like setae on the outer margin of tibiae and usually on the tarsi, very rarely with one or two present (figs. 7c, 9a, 11f, 13c, 15a, 18d, 22c, 24c) 4

2(1) Dark brown markings on head, mandibles and labrum (figs. 4e, 5d); sternite spines on distal margin of abdominal segments V–IX conical with bases contiguous (fig. 4j; spines on distal margin of tergites long and widely spaced at base (fig. 4i) S kolomystax brevis

2’ Head, mandibles and labrum without distinct brown markings; sternite spines on distal margin of abdominal segments II–IX or III–IX, tergites and sternite spines long with alternating shorter spines (figs. 2f–g, 19f–g) 3

3(2) Labrum with notch with margins angled, notch depth>25% of total length (figs. 2a, b); segment I of maxillary palp long, extending to apical third of galealacinia, segments I+II length extends beyond apex of galealacinia (fig. 2c); fore femur with <25 setae on outer margin and <35 on inner margin; mid-tibia with <20 setae on outer margin and <25 setae on inner margin; hind tarsus with <25 spines on the inner margin Skolomystax elongatus

3’ Labrum with notch margins parallel (square notch), notch depth <22% of total length (figs. 19a, b); segment I of maxillary palp long, extending to mid-third of galealacinia, segments I+II length extends to apex of galealacinia (fig. 19c); fore femur with>35 setae on outer margin and>35 on inner margin; mid-tibia with>25 setae on outer margin and>25 setae on inner margin; hind tarsus with>30 spines on the inner margin Skolomystax paschei

4(1) Body with numerous small dark spots (figs. 18c, 25h–j); canines of maxillae distinctly broader than lacinial setae; left mandible with inner margin of outer incisors with 1–3 small indistinct spines (figs. 14h, 17h); northern Australia 5

4’ Body lacking numerous small dark spots (figs. 25d–g, 25l–m); canines of maxillae similar to lacinial setae; left mandible with inner margin of outer incisors with 2–5 distinct spines (figs. 6g, 8g, 10g, 12g, 21g, 23g), southern Qld, southeast mainland Australia, and Tas. 6

5(4) Maxillary palp long, with apex of segment II extending beyond apex of galealacinia (fig. 14c); sternite spines on abdominal segments IV–IX Skolomystax hawkingi

5’ Maxillary palp short, with apex of segment II not extending beyond apex of galealacinia (fig. 17c); sternite spines on abdominal segments V–IX Skolomystax leichhardti

6(4) Sternite spines on distal margin of abdominal segments VI–IX or VII–IX 7

6’ Sternite spines on distal margin of abdominal segments IV–IX or V–IX 8

7(6) Femora with distinct elongate sub-apical spot; maxillary palp segment II equal in length to segment III (fig. 10c); left mandible with inner margin of outer incisor with two teeth (fig. 10g), sternite spines on distal margin of abdominal segments VI–IX Skolomystax gippslandicus

7’ Femora without distinct sub-apical spot; maxillary palp segment II shorter than segment III (fig. 8c); left mandible with inner margin of outer incisor with four teeth (fig. 8g), sternite spines on abdominal segments VI–IX or VII–IX Skolomystax dyarrbi

8(6) Tergite X tinged dark; tergite spines long but with occasional short spines; left mandible with outer incisor with three teeth on inner margin (fig. 12g) Skolomystax goorudensis

8’ Tergite X light; tergite spines all long (figs. 7e, 22e, 24e); left mandible outer incisor with 3–5 teeth on the inner margin (figs. 6g, 21g, 23g) 9

9(8) Maxillary palp segment II longer than segment III (fig. 6c) with segment I extending nearly to apex of galealacinia; left mandible with base of inner incisors rugose (fig. 6g); labial notch angle <100 o (fig. 6a) Skolomystax chionotos

9’ Maxillary palp segment II shorter than segment III (figs. 21c, 23c) with segment I extending no more than to the apical third of galealacinia; labial notch angle>100 o (figs. 21a, 23a) 10

10(9) Maxillary palp segment II shorter but almost equal to segment III (fig. 23c); left mandible with base of inner incisors smooth (fig. 23g); Australian mainland Skolomystax vulgaris

10’ Maxillary palp segment II shorter than segment III (fig. 21c); left mandible with base of inner incisors rugose (fig. 21g); endemic to Tasmania Skolomystax tasmaniensis