Pza

38 The monophyletic nature of the Planoneoptera is now widely supported [e.g., see

Boudreaux (1979), Hennig (1981), Kristensen (1981,1989), Kukalova-Peck (1991), and Kukalova-Peck and Brauckmann (1992)]. However, there is still some argument as to whether the Pliconeoptera constitutes its sister group (i.e., is monophyletic) or is a polyphyletic assemblage. In Martynov's view the features uniting the pliconeopteran orders included chewing mouthparts, a large anal lobe in the hind wing that folds like a fan along numerous anal veins, complex wing venation (typically including many crossveins) that differs between fore and hind wings, presence of cerci, numerous Malpighian tubules, and separate ganglia in the nerve cord. However, except for the first two, these features are no longer considered to be synapomorphic. The proposed sister-group relationship of the Paraneoptera and Oligoneoptera (i.e., the unity of the Pliconeoptera) has been given strong support by the extensive analysis of Wheeler et al. (2001). Kukalova-Peck (1991) and Kukalova-Peck and Brauckmann (1992) presented a new scheme for relationships among the Neoptera (Figure 2.5D), claiming several potential synapomorphic features of wing venation between plecopteroids and orthopteroids (implying a sister-group relationship). Yet, they found no apomorphies shared by orthopteroids and blattoids. Rather, the latter have possible synapomorphies with the Paraneoptera; that is, the two may be sister groups.

Generally included in the plecopteroids are the fossil orders Protoperlaria (Upper Carboniferous-Permian) and Paraplecoptera (Upper Carboniferous-Jurassic) [both of which are considered to be Protorthoptera by Carpenter (1992)], and the extant order Plecoptera (Permian-Recent). However, members of the two fossil orders are included in the Grylloblattodea by Storozhenko (1997) (and see below). The Protoperlaria may have been the ancestors of the P1ecoptera. Early plecopteroids had well formed prothoracic winglets, chewing mouthparts, and long cerci. In some species there was no metamorphic final juvenile instar. In some species the young nymphs were semiaquatic, with articulated thoracic winglets and nine pairs of abdominal gills (Figure 2.7A). Older juveniles may have been terrestrial and able to fly. The Plecoptera (stoneflies) appear to have separated from the

FIGURE 2.7. (A) Early Permian plecopteroid nymph, Gurianovaella silphidoides; and (B) The most primitive hemipteran, a member of the Archescytinidae, feeding on a cone of an Early Permian gymnosperm. [From A. P. Rasnitsyn and D. L. J. Quicke (eds.), 2002, History of Insects. @ Kluwer Academic Publishers, Dordrecht. With kind permission of Kluwer Academic Publishers and the authors.]

FIGURE 2.7. (A) Early Permian plecopteroid nymph, Gurianovaella silphidoides; and (B) The most primitive hemipteran, a member of the Archescytinidae, feeding on a cone of an Early Permian gymnosperm. [From A. P. Rasnitsyn and D. L. J. Quicke (eds.), 2002, History of Insects. @ Kluwer Academic Publishers, Dordrecht. With kind permission of Kluwer Academic Publishers and the authors.]

remaining plecopteroids early and even by the time at which fossil stoneflies appear, some 39

of these are assignable to extant families (Wootton, 1981).

A ,, 1- ^ /TT r-u-f r, \ ' a • 11 " i INSECT DIVERSITY

As noted earlier, the Protorthoptera (Upper Carboniferous-Permian) is a mixed bag of fossils, almost certainly a polyphyletic group. Not surprisingly, it has often been suggested as the group from which the remaining orthopteroid orders evolved. The major difficulty in clarifying relationships within the group is that some 80% of Carboniferous protorthopter-ans are known only from fore wings or wing fragments. Permian forms are generally more completely preserved and superficially may resemble other groups (e.g., Plecoptera and Dictyoptera), though are obviously "too late" to be their ancestors (Wootton, 1981). A recent re-examination of the Protorthoptera by Kukalova-Peck and Brauckmann (1992) indicated that the majority of protorthopterans are primitive hemipteroids, though the group also includes plecopteroids, orthopteroids, blattoids, and even endopterygotes! The order Miomoptera (Upper Carboniferous-Permian) was erected to include a group of small, chewing insects with homonomous wings, simple venation, and short, distinct cerci, that were originally included in the Protorthoptera. The position of this order remains debatable; some authors (e.g., Carpenter, 1992) suggested that miomopterans may be hemipteroid, perhaps close to the Psocoptera, while others (e.g., Kukalova-Peck, 1991) believe that they may be endopterygotes, possibly close to the panorpoid-Hymenoptera stem group. Unfortunately, the immature stages are unknown. Another Upper Carboniferous-Permian group, the Caloneurodea, is also problematical. The chewing mouthparts seen in some fossils, short cerci, and wing venation led Carpenter (1977, 1992) to place them close to the Protorthoptera. Shear and Kukalova-Peck (1990) and Kukalova-Peck (1991), on the basis of the inflated clypeus (housing the sucking apparatus) and the chisellike laciniae, consider them hemipteroids, while some Russian paleontologists have suggested they are plecopteroids or even endopterygotes, perhaps close to the base of the neuropteroids and Coleoptera (Storozhenko, 1997).

The orthopteroid orders include the Orthoptera, Phasmida, Dermaptera, Gryll-oblattodea, probably the Mantophasmatodea, and possibly the Embioptera and Zoraptera. Orthoptera were widespread by the Upper Carboniferous, being easily recognizable by their modified hindlegs and particular wing venation. Early in the evolution of this order a split occurred, one line leading to the Ensifera (long-horned grasshoppers and crickets), the other to the Caelifera (short-horned grasshoppers and locusts). Indeed, Kevan (1986) and others have strongly urged that the two groups each be given ordinal status, an arrangement supported by those who claim, on the basis of dubious paleontological evidence, that the Caelifera and Phasmida (stick insects) may be sister groups. However, in addition to the two features already noted, the laterally extended pronotum covering the pleuron, the horizontally divided prothoracic spiracle, and the hind tibia with two rows of teeth appear to be synapomorphies confirming the unity of the Orthoptera. The fossil record of the Phasmida is poor, though specimens are known from the Upper Permian onward. Kamp's (1973) phenetic analysis of extant forms indicated that the phasmids are closest to the Dermaptera and Grylloblattodea, the three orders forming a natural group. Boudreaux (1979), on the other hand, listed a number of possible synapomorphies that would render the Phasmida and Orthoptera sister groups, (a view supported by Wheeler et al.'s (2001) study). Authorities still disagree on the affinities of the Dermaptera (earwigs), which do not appear in the fossil record until the Lower Jurassic. Some have placed them close to the Plecoptera, Orthoptera, Embioptera, and even the endopterygote Coleoptera, while others considered them to be only distantly related to any of the extant orthopteroid groups. Giles' (1963) comparative morphological study and the combined morphological-molecular analysis by Wheeler et al.

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