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7.1. Kemperala (Paoliidae) from the mid-Carboniferous of Germany. Paoliids, which occurred from the mid- to Late Carboniferous, were among the earliest known winged insects, but they also folded their wings over their backs and may have been the earliest neopterans. Photo: C. Brauckmann.

difficult to place into or near any one of these lineages. Even though our understanding of relationships among hexapods is congealing, the ancient origins and relationships among early polyneopterans has been difficult to interpret. The polyneopterans may represent the first major radiation of neopteran insects (note here that we say "neopterans," not "neopterous," because neopterous insects appeared conver-gently within the superorder Palaeodictyopterida, i.e., the Diaphanopterodea). The polyneopteran radiation began in the Paleozoic; however, the origination of what we recognize as the modern polyneopterous orders did not occur until later as a second, post-Permian radiation.

Polyneopterans stem from the late Paleozoic and are most widely known by the heterogeneous assemblage of Paleozoic families united into the "Protorthoptera." At present, the "Protorthoptera" are a cloud of genera and families, among which all other orders of Polyneoptera have arisen. Thus, "protorthopterans" have been a receptacle for any Paleozoic or Early Mesozoic polyneopterous insect not readily assigned to one of the modern orders; it is a polyphyletic conglomeration of unrelated families that retained traits primitive not only for Polyneoptera but in many cases for Neoptera as a whole. The recognition of this problem is not new; even Tillyard (1928d) recognized that the "Protorthoptera" were an "omnium gatherum." The most fruitful work on these extinct insects will clarify phylogenetic relationships for the families and genera of "Protorthoptera." Basal Neoptera diversified during the Late Paleozoic, and soon after the end of the Permian, the Polyneoptera appear to have coalesced into those clades we recognize today. Thus, most of the polyneopterous orders we are familiar with today are Early Mesozoic in origin. Once the true relationships of many of the protorthopteran lineages are elucidated, it will be necessary to resurrect many of Handlirsch's and Tillyard's orders, such as Cnemi-dolestodea. Interesting groups are already recognizable from "Protorthoptera," which provide insight into the earliest differentiation of higher groups within the insects, but relationships remain veiled by unnatural, classificatory edifices (e.g., Rasnitsyn and Quicke, 2002).

WHAT ARE POLYNEOPTERA?

Fundamental to our understanding of relationships within Polyneoptera is the question surrounding their monophyly. The defining feature for the group is the expansion of the anal region in the hind wing by the addition of numerous anal veins (Figure 7.2), apparently secondarily reduced in Zoraptera + Embiodea and unknown for the apterous orders Grylloblattodea and Mantophasmatodea. Interestingly, recent molecular studies have also supported the Polyneoptera to some extent (e.g., Wheeler et al., 2001). Additional traits uniting polyneopterans may also be present in the neuroanatomy and other internal organs (e.g., Ali and Darling, 1998; Pass, 2000).

Reductions of various structures commonly obscure homologies in the Polyneoptera, but fortunately fossils help to clear some of the confusion. For example, three-segmented (trimerous) tarsi occur in some Orthoptera, one lineage of Phasmatodea (Timema), extant Dermaptera, extant Plecoptera, and Embiodea. By examining solely Recent species one might unite these groups on this distinctive trait (e.g., Grimaldi, 2001). However, fossils of stem-group Plecoptera and stem-group Dermaptera all primitively retained five-segmented tarsi while also having features shared with each of their crown groups. In other words, the reduction to three-segmented tarsi has occurred independently within each of these orders. It is imperative that a paleontological perspective be applied when attempting to resolve the relationships of highly modified survivors of an ancient radiation, in this instance, ones that were Early Mesozoic or latest Paleozoic in origin (Gauthier et al., 1989).

For the moment, three groups are readily definable within the Polyneoptera. These are the superorders Plecopterida (stoneflies, webspinners, and zorapterans), Orthopterida (walking sticks, crickets, grasshoppers, wetas, and their relatives), and Dictyoptera (roaches, mantises, and termites) (Figure 7.3). Dictyopteran monophyly and internal relationships are elaborated upon later. The earwigs (Dermaptera), African rock crawlers (Mantophasmatodea), and ice crawlers (Grylloblattodea) remain difficult to place within Poly-neoptera. Grylloblattodea and Mantophasmatodea are probably basal orthopteridans, but the loss of wings in both of

GrylloblattodraProtorthoptera

7.2. Wings of representative living polyneopterous insects, showing the diversity of wing venation. Not to same scale.

TABLE 7.1. Significant Characters in Polyneopteran Phylogeny0

7.3. Phylogeny and the evolution of diets of polyneopterous insects, with significant characters indicated (see Table 7.1). The thick lines indicate the known extent of the fossil record. From various sources (see text).

1. Hind wing with expansive, fanlike anal lobe

2. Head prognathous

3. Ovipositor lost

4. Nymphs aquatic, with filamentous tracheal gills on thorax/abdomen, or both

5. Anal lobe of hind wing lost

6. Cercus reduced to one to two segments

7. Wings dehiscent

8. Hind femora enlarged, with distinctive musculature

9. Communal behavior

10. Secrete silk with enlarged fore basitarsus having numerous silk glands

11. Wing veins lie in blood sinuses that inflate

12. Distinctive, reduced wing venation

13. Asymmetrical male terminalia

14. Highly reduced, distinctive venation

15. Wingless, blind morphs; winged, eyed morphs

16. Hind femur with thick spines

17. Ovipositor highly reduced

18. Forewings tegminous, short (hemeltyra)

19. Hind wings with unique folding mechanism, very large anal fan

20. Cerci modified into sclerotized, unsegmented forceps

21. Ocelli lost

22. Apterous (all individuals, not as morphs) + molecular characters

23. Pronotum large, with cryptopleuron

24. Saltatorial hind legs, large hind femur

25. Prothoracic defensive glands

26. Male with vomer (tenth sternite, used in mating)

a Numbers correspond to those on phylogeny, Figure 7.3.

7.3. Phylogeny and the evolution of diets of polyneopterous insects, with significant characters indicated (see Table 7.1). The thick lines indicate the known extent of the fossil record. From various sources (see text).

these groups, perhaps in the common ancestor of both, obscures their relationship. Similarly, the placement of earwigs is contentious, and rightly so, with much of the debate centering on an extinct group known as the Protelytroptera. Molecular studies suggest an affinity of earwigs with the Dictyoptera (e.g., Wheeler et al., 2001) but the only morphological support for this is the enlargement of the coxae; the overlapping sternites referred to by Hennig (1981) is likely plesiomorphic.

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