CLADOENDESIS OF EPHEMEROPTERA
Anteritorna (or Ephemera/fg4)
(Panephemeroptera Euephemeroptera Euplectoptera - Anteritorna)
Nomen hierarchicum: Ephemera/fg4 [f:1810; g:1758] (sine Prosopistoma; incl. Baetis)
Nomen circumscribens: Anteritorna Kluge 1993b: 35; as manuscript name: Kluge 1992d, 1992e.
In circumscription fits:
— "Larves nudibranches": Lestage 1917: 244
— subordo Anteritorna (as manuscript name): Kluge 1992d: 10; 1992e: 24
— subordo Anteritorna Kluge 1993b: 35
— Anteritorna = Ephemera/fg4: Kluge 2000: 247
References. Kluge 1993b: *; – Kluge & Studemann & Landolt & Gonser 1995: * – Kluge 1998: * *; – Kluge 2004: * * *.
Autapomorphies of Anteritorna.
(1) Tornus of fore wing is situated between apices of veins CuA and CuP; thus CuP usually terminates at basitornal margin of wing far from tornus (Kluge 2004: Fig.7:C), and only in Ametropus – close to tornus (Kluge 2004: Fig.24:C) (unlike Posteritorna, where tornus is situated behind apex of CuP).
The difference in tornus position between Posteritorna and Anteritorna does not depend on size of hind wings, as Anteritorna include species with hind wings either well-developed, or vestigial, or completely lost. In the cases when the hind wing is vestigial or lost, the tornus of fore wing is usually transferred proximally (Kluge 2004: Fig.90:A-B), becomes obtuse or disappears (Kluge 2004: Fig.100:A-B), but never changes its position relatively to terminations of the longitudinal veins, being in Anteritorna always between CuA and CuP.
In connection with presence of tornus between CuA and CuP, a field between these veins, named cubital field, is modified: only in proximal part it is bordered posteriorly by CuP, while in distal part its posterior border is made by basitornal wing margin; in this part, instead of usual crossveins, cubital field has peculiar veins filling the space between CuA and basitornal margin (while in Posteritorna cubital field is a simple narrow field bordered posteriorly by CuP up to tornoapical wing margin, and bearing the same venation as in fields anteriad of it).
Various Anteritorna have different venation of the cubital field. We proceed from an assumption that initial type of cubital field venation is siphlonuroid one: several sigmoid veins go from CuA to basitornal margin (Kluge 2004: Fig.7:C). In mayflies with such venation hind wing usually retains greatest length (up to 1/2 of fore wing length); correspondingly to this, basitornal margin of fore wing is also long, CuA passes along it at some distance, so the cubital field is long and narrow all over its length. This type of cubital field is present in Siphlonurus/fg1, Ameletus/fg2, Nesameletus/f1=Metamonius/g1, Vetulata, Ameletopsis/fg1, Rallidens, and Coloburiscus/fg1. In the past, on the base of wing venation, these taxa were united in a family Siphlonuridae, which was surely paraphyletic, because at least Ameletus/fg2 and Coloburiscus/fg1 belong to the phylogenetic branches, which other representatives have different wing venation.
In many other mayflies cubital field venation is modified, and the same several types of its venation are repeated in non-related taxa (see Index of characters [2.2.51] and [2.2.52]). Cubital field can be wider, and veins arising from CuA can be bifurcate (Kluge 2004: Fig.40:A, 68:A) or multibranched. These veins can be substituted by intercalaries going parallel to CuA. The cubital intercalaries can originate either as elongation of middle portions of the sigmoid veins (in this case the posteriormost intercalaries are the longest), or as anastomoses between the initial sigmoid veins. There are intermediate forms between the typical siphlonuroid sigmoid veins and the intercalaries, so the types of venation used in the taxa characteristics below, are rather arbitrary.
In some cases venation of cubital field provides a regular alternating of concave and convex veins, like that on the rest part of the wing; while vein alternating in general is an ancient primitive feature of Ephemeroptera, such alternating in cubital field is most probably secondary, independently evolving in several non-related groups of Anteritorna. In some taxa cubital field has intercalaries arranged in pairs (see Index of characters [2.2.52]), where each pair consists of a convex and a concave vein, alternating with convex CuA and concave CuP. Bifurcate veins arising from CuA, can have hind branch convex and fore branch convex, providing the same effect. In Isonychia/fg1 two proximalmost veins going from CuA to basitornal margin, are usually non-branched (Kluge 2004: Fig.40:A), the proximalmost is convex (like CuA), and the next is concave. In some taxa CuA and the proximalmost vein arising to basitornal margin (often called "CuA2") together form a strong bifurcate convex vein; a concave intercalary is present between its branches (Kluge 2004: Fig.75:A) (see Index of characters [2.2.50]); most probably, this structure is secondary, in spite of the fact that it resembles a triad of CuA characteristic for permoplectopteran mayflies Protereisma (Carpenter 1979: Fig.1; Kluge 2004: Fig.14:B) and Palingeniopsis (Martynov 1932: Pl.I:2), and triads initial for many other veins of mayflies.
A hypothesis was suggested, that Posteritorna and Anteritorna independently originated from Permoplectoptera; their hind wings shortened independently, and in connection with this, their fore wings got tornus independently, at two different places (Edmunds & Traver 1954b); this idea does not contradict the known data (Kluge 1998). It was also assumed that Anteritorna originated from Protereisma-like ancestor, which had a primitive triad of CuA; thus, some authors regard the presence of triad of CuA in recent mayflies to be a plesiomorphy (Edmunds & Traver 1954b). However, this triad is present only in a few short-living mayflies with highly modified venation – Behningia/fg2 (but not in Protobehningia) and some representatives of Anagenesia/fg1 (but not other Palingenia/f2=g1), and thus, most probably, it is a secondary one. Triad of CuA is present also in extinct Hexagenites/fg1, which is regarded to be primitive only because of its Mesozoic age; however, wing venation of Hexagenites/fg1 is unique and undoubtedly modified.
(2) Maxilla has no more than 3 dentisetae; number of dentisetae is determinate, in different representatives it can be three (Kluge 2004: Fig.3:E), two, one, or none (see Index of characters [1.1.37]); a single known exception is made by Coloburiscus/fg1, where number of dentisetae can vary individually from 2 to 3.
Size. Fore wing length 2–40 mm.
Age and distribution. Jurassic (see Eusetisura INCERTAE SEDIS, Fossoriae INC.SED. and Anteritorna INC.SED.) – recent; world-wide.
The taxon Anteritorna (or Ephemera/fg4) is divided into:
1. plesiomorphon Tridentiseta (or Baetis/fg1)
2. Bidentiseta (or Ephemera/fg5)
2.1. Branchitergaliae (or Heptagenia/f1=Oligoneuria/g1)
2.2. Furcatergaliae (or Ephemera/fg6)
Some extinct taxa and some insufficiently described species have uncertain systematic position - see Anteritorna INCERTAE SEDIS