Vetulata, or Oniscigaster/fg1

(Panephemeroptera Euephemeroptera Euplectoptera Anteritorna pm.Tridentiseta
 - Vetulata)

Nomen hierarchicum: Oniscigaster/fg1 [f:1917; g:1873] (incl. Tasmanophlebia)  

Nomen circumscribens: Vetulata McCafferty 1991a: 349. 

In circumscription fits:

— subtribus Oniscigastrina Lameere 1917: 62

— subfam. Oniscigastrinae: Edmunds & Traver 1954a: 237

— fam. Oniscigastridae: Landa 1973: 156

— infraordo Vetulata McCafferty 1991a: 349

— Vetulata = Oniscigaster/fg1: Kluge 2004: 110

References. Edmunds & Allen & Peters 1963: *; – Koss & Edmunds 1974: *; – Edmunds 1975: ; – Kluge & al 1995: * * *; – Kluge 2004: * * *.

Autapomorphies of Vetulata.

(1) Larval abdominal tergum I has posterior margin elevated; tergalii I are rounded-triangular, without anal-proximal lobe [unlike tergalii of next pairs – see (2)] and are specialized as gill opercula. In Tasmanophlebia/fg1 they cover the rest tergalii (Kluge 2004: Fig.33:A), while in Oniscigaster/fg2 they are not larger than other tergalii and do not cover them, but also have operculate specialization: anal margin, being directed anteriorly, is inserted under a hanging posterior margin of abdominal tergum I (Kluge 2004: Fig.32:A). Unique apomorphy: in some other mayfly groups gill opercula are also present, but these are tergalii not of the first pair, but of second, third or forth pair.

(2) Tergalii of next pairs (II–IV or II–VI) with projected anal-proximal lobe (having different structure in Oniscigaster/fg2 and Tasmanophlebia/g1 – see below) (Riek 1973: Fig.3). Ribs of tergalii are reduced, only weakly developed costal rib in proximal part of costal margin can be present (non-unique apomorphy – see Index of characters [1.3.27–29]).

(3) In larva at least anteriormost abdominal terga (I–IV) have median projections (Eaton 1883-1888: Pl.51:1; Edmunds 1975: Fig.29-31, photos ). Non-unique apomorphy (see Index of characters [1.3.3]).

(4) Larval abdomen with wide lateral lobes, thus tergalii lie dorsally (not by sides) (Eaton 1883-1888: Pl.51:1; Edmunds 1975: Fig.29-31, photos ). Non-unique apomorphy.

(5) In larva portion of frons between antennae bases is elevated and bordered by a pair of longitudinal keels (Eaton 1883-1888: Pl.51:1-5). Head retains hypognathous position. 

Characters of Vetulata of unclear phylogenetic status.

(6) Imaginal and subimaginal furcasternal protuberances are not contiguous, furcasternal median impression is parallel-sided, not widening posteriorly; metathoracic nerve ganglion is situated in posterior part of furcasternum (Kluge 2004: Fig.32:D). Non-unique apomorphy (see Index of characters [2.2.23]); among Tridentiseta the same in other Amphinotic groups – Nesameletus/f2=Metamonius/g2, Ameletopsis/fg1 and Rallidens.

(7) Larval paraproct with a spine on inner-apical margin (Kluge 2004: Fig.33:F). The same in Siphlonurus/fg2, Metretopus/fg1, Siphluriscus and Rallidens.

Plesiomorphies of Vetulata. Larva retains features of primary swimming siphlonuroid specialization: abdomen is large; caudalii are not long, paracercus is well-developed, primary swimming setae are dense, secondary swimming setae on lateral margins of cerci are usually absent (photo ), rarely present (in Tasmanophlebia/g1 sp.V1 from Australia). Mouth apparatus is non-specialized (Eaton 1883-1888: Pl.51:7-12); maxilla with 3 canines and 3 dentisetae [see Anteritorna (2)] (Kluge 2004: Fig.32:E), setae of its apical-ventral row are from simple to pectinate; maxillary palp is 3-segmented; labial palp is 3-segmented. Larval (and adult) patella-tibial suture is developed on middle and hind legs only. Larval claws are slightly curved, with very small irregular denticles only. Tergalii [see (1)] retain ability of rhythmical respiratory movements(see Index of characters [1.3.30]); this was observed for ventilans [Siphlonella], whose tergalii I form immovable gill opercula and only tergalii II–IV are able to make respiratory movements [see below, Tasmanophlebia/g1 (2)].

In imago and subimago: Mesonotal suture is more or less transverse (Kluge 2004: Fig.32:B, 33:D-E, photo ). Paracoxal suture is complete (Kluge 2004: Fig.32:C-D, photo ) (unlike Rallidens and some Bidentiseta). Subimaginal lateral sclerotized pigmented area of mesonotum is small, bifurcates posteriorly in such a manner, that one its branch stretches along lateroparapsidal suture, and another branch – along lateral scutal suture (Kluge 2004: Fig.32:B) (see Index of characters [2.2.14]). In cubital field of fore wing several (5–9) veins go from CuA to basitornal margin (photos ) [see Anteritorna (1)]; hind wing is well-developed, as long as 0.45 of fore wing length (photos ). Imaginal and subimaginal tarsi are 5-segmented, 1st segment is non-shortened and fused with tibia (photo ). All claws of imago and subimago are ephemeropteroid. Gonostylus with 2 distal segments.

Size.  Fore wing length 10–20 mm.

Distribution.  Notogea: Australia, New Zealand and Chile-Patagonian Region of South America.

Systematic position of Vetulata. A relationship between Vetulata and Furcatergaliae was assumed, in connection with this there was established a suborder Rectracheata McCafferty 1991 (uniting Vetulata, Furcatergaliae and Posteritorna). This assumption is not grounded, the taxon Rectracheata is polyphyletic (Kluge 1998).

The taxon Vetulata (or Oniscigaster/fg1) is divided into:

1. Oniscigaster/fg2

2. Tasmanophlebia/fg1 (incl. Siphlonella)