Evolution of the Insects

CY501-C07[188-260].qxd 3/2/05 12:44 PM Page 188 quark11 Quark11:Desktop Folder:CY501-Grimaldi:Quark_files: 7 PPolyneopteraolyneoptera Laurentiaux-Vieira and Laurentiaux, 1986; Maples, 1989). NEOPTERA The antennae were long and filiform, and the legs were This group of winged insects appeared in the earliest Late unmodified, slender, and had five-segmented tarsi. Unfortu- Carboniferous (early Bashkirian) and subsequently radiated nately, the paoliids are poorly understood, with few body into every imaginable terrestrial and freshwater niche. Fea- characters known; fortunately, however, the wings are pre- tures of the Neoptera (discussed earlier, and briefly reiterated served. These insects had relatively broad, homonomous here) include wing flexion via special muscles attached to the wings with rich crossvenation that formed an archedictyon, third axillary sclerite (Figure 4.6), the formation of a median and the hind wing lacked an anal fan. The absence of an anal plate in the wing base, the radial vein never forking from the fan in most non-neopteran lineages suggests that this is a wing base, and the development of a gonoplac (i.e., the third primitive trait for Neoptera and that this feature may indeed “valvula”). support the monophyly of Polyneoptera (with several, inde- Why should this group have been so successful among the pendent reversals therein). Paranotal lobes were not present flying insects? The ability to flex the wings over the abdomen in paoliids, and the occurrence of these structures among when at rest is much more significant than it might at first some “Protorthoptera” families, particularly those allied to appear, and it is a remarkable quirk of nature that a few tiny the Plecoptera, may be a derived trait for those lineages muscles attached to a minute sclerite should be one of the as well (and convergent with the paranotal lobes in Palaeo- main reasons for the great success of insects. Wings are vital dictyoptera and Geroptera). Alternatively, but a less parsimo- means of dispersal and thus require protection; they need to nious explanation, is that paranotal lobes are primitive for all be stored when not in use and to minimize damage while the pterygotes (and homologous to the “protolobes” of Zygen- insect is moving amidst leaves, under bark or rocks, or in toma), in which case the loss of such lobes would have other tight spaces. The wings themselves can also serve to occurred independently in the Ephemeroptera lineage protect the abdomen, which is the function of leathery (including Lithoneura), in Holodonata, in Dicliptera ϩ forewings, or tegmina, in roaches and some orthopteridans, Diaphanopterodea Eumegasecoptera ϩ Protohymenoptera, and the entirely sclerotized earwig tegmina and beetle elytra. in Paoliidae, and in Eumetabola and frequently among The ability to adeptly control the wings when not aerial was polyneopterans. certainly a major innovation among the flying insects, as is Neoptera is generally divided into three major lineages: shown by the fact that when fossil neopterans appeared, they Polyneoptera, Paraneoptera, and Holometabola, the latter quickly outnumbered paleopterous insects. two being sister groups and each definitively monophyletic, Some of the earliest neopteran insects include members while strong support for a polyneopteran group is elusive. of the Carboniferous family Paoliidae (Figure 7.1). Paoliids were rare, large insects that have at times been placed in their The Polyneoptera, under one concept or another, have tradi- own order, Protoptera (e.g., Sharov, 1966). The group is char- tionally gone by the name of Paurometabola (exclusive of acterized by numerous primitive features, and they actually several orders), Orthopteroidea, or simply the orthopteroid lacked any derived traits (at least none observable in pre- insects. This is a disparate group of generalized and special- served specimens). This family is very likely a stem group to ized unlikely relatives, and indeed, the group is ill-defined all other Neoptera. Ten genera and 12 species are presently and may not be natural. Some superordinal groups appear recorded from the early Pennsylvanian of Europe and North well supported, particularly the Plecopterida, Orthopterida, America (e.g., Smith, 1871; Handlirsch, 1906a,b, 1919; and Dictyoptera (discussed later), while the orders Laurentiaux, 1950; Kukalová, 1958; Brauckmann, 1984, 1991; Dermaptera, Grylloblattodea, and Mantophasmatodea are 188 CY501-C07[188-260].qxd 3/2/05 12:44 PM Page 189 quark11 Quark11:Desktop Folder:CY501-Grimaldi:Quark_files: POLYNEOPTERA 189 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 7.1. Kemperala (Paoliidae) from the mid-Carboniferous of Germany. anal veins (Figure 7.2), apparently secondarily reduced in Paoliids, which occurred from the mid- to Late Carboniferous, were Zoraptera ϩ Embiodea and unknown for the apterous orders among the earliest known winged insects, but they also folded their Grylloblattodea and Mantophasmatodea. Interestingly, recent wings over their backs and may have been the earliest neopterans. Photo: C. Brauckmann. molecular studies have also supported the Polyneoptera to some extent (e.g., Wheeler et al., 2001). Additional traits unit- ing polyneopterans may also be present in the neu- difficult to place into or near any one of these lineages. Even roanatomy and other internal organs (e.g., Ali and Darling, though our understanding of relationships among hexapods 1998; Pass, 2000). is congealing, the ancient origins and relationships among Reductions of various structures commonly obscure early polyneopterans has been difficult to interpret. The homologies in the Polyneoptera, but fortunately fossils help polyneopterans may represent the first major radiation of to clear some of the confusion. For example, three- neopteran insects (note here that we say “neopterans,” not segmented (trimerous) tarsi occur in some Orthoptera, one “neopterous,” because neopterous insects appeared conver- lineage of Phasmatodea (Timema), extant Dermaptera, gently within the superorder Palaeodictyopterida, i.e., the extant Plecoptera, and Embiodea. By examining solely Diaphanopterodea). The polyneopteran radiation began in Recent species one might unite these groups on this distinc- the Paleozoic; however, the origination of what we recognize tive trait (e.g., Grimaldi, 2001). However, fossils of stem-group as the modern polyneopterous orders did not occur until Plecoptera and stem-group Dermaptera all primitively later as a second, post-Permian radiation. retained five-segmented tarsi while also having features Polyneopterans stem from the late Paleozoic and are most shared with each of their crown groups. In other words, the widely known by the heterogeneous assemblage of Paleozoic reduction to three-segmented tarsi has occurred indepen- families united into the “Protorthoptera.” At present, the dently within each of these orders. It is imperative that a “Protorthoptera” are a cloud of genera and families, among paleontological perspective be applied when attempting to which all other orders of Polyneoptera have arisen. Thus, resolve the relationships of highly modified survivors of an “protorthopterans” have been a receptacle for any Paleozoic ancient radiation, in this instance, ones that were Early or Early Mesozoic polyneopterous insect not readily assigned Mesozoic or latest Paleozoic in origin (Gauthier et al., 1989). to one of the modern orders; it is a polyphyletic conglomera- For the moment, three groups are readily definable within tion of unrelated families that retained traits primitive not the Polyneoptera. These are the superorders Plecopterida only for Polyneoptera but in many cases for Neoptera as a (stoneflies, webspinners, and zorapterans), Orthopterida whole. The recognition of this problem is not new; even (walking sticks, crickets, grasshoppers, wetas, and their rela- Tillyard (1928d) recognized that the “Protorthoptera” were an tives), and Dictyoptera (roaches, mantises, and termites) “omnium gatherum.” The most fruitful work on these extinct (Figure 7.3). Dictyopteran monophyly and internal relation- insects will clarify phylogenetic relationships for the families ships are elaborated upon later. The earwigs (Dermaptera), and genera of “Protorthoptera.” Basal Neoptera diversified African rock crawlers (Mantophasmatodea), and ice crawlers during the Late Paleozoic, and soon after the end of the Per- (Grylloblattodea) remain difficult to place within Poly- mian, the Polyneoptera appear to have coalesced into those neoptera. Grylloblattodea and Mantophasmatodea are prob- clades we recognize today. Thus, most of the polyneopterous ably basal orthopteridans, but the loss of wings in both of CY501-C07[188-260].qxd 3/2/05 12:45 PM Page 190 quark11 Quark11:Desktop Folder:CY501-Grimaldi:Quark_files: 190 EVOLUTION OF THE

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