Although oribatid mites are essential for decomposing plant tissue in modern temperate forests by helping to convert primary productivity into soil organic matter, little is known about their paleoecological history. In contrast, the known fossil body record of oribatid mites begins during the Middle Devonian, but does not reappear until the Early Jurassic, by which time the mite taxa are modern in appearance. There has been no comprehensive community-wide synthesis of fossil evidence for the role of oribatid mites in the decomposition of plant material, with the exception of recent studies of Quaternary environments, summarized in Ehas (1994).
Finally, oribatid mites and other microarthropods and macroarthropods are crucial in the vertical translocation of organic matter downward in the soil column (Saichuae et al., 1972), partly as an effect of ecological guild succession during the decomposition process. Many oribatid mites feed in decomposing structural material of plants (Seastedt, 1984; Ramani and Haq, 1991), and inhabit both hving and dead fungal fruiting bodies and -hchens (Bellido, 1Ô79,1990). Kühnelt (1976) characterized oribatid mites as endophages, which exist in internal plant tissues or ectophages, as external feeders.
The first panel (literature sources 1 to 16) represents the body fossil data of oribatid mites {Krlvolutsl^ and Druk, 1986; Krivolutsky et al., 1990). Fossils of oribatid mites occur in three forms: as compact and unaltered cuticle, permineraliza-. Rare examples of oribatid mites are known from compressions and impressions in mudstones (Baker and Wighton, 1984; Pérez, 1988).
Oribatid mites are the only group of arachnids with a respectable record of body fossils (Appendix 1) and trace fossils (Figs. 1-12).
330 LABANDEIRA ET AL
After the demise of lycopsid-dominated forests in late Middle Pennsylvanian, Psaronius tree ferns became the dominant vegetation in equatorial Eurasian wetlands until the Early Permian. In fact, Psaronius and other ferns are responsible for 64.3 percent of plant biomass, and 76.7 percent of borer feeding tracks. Seed ferns rank second (24.2 percent) in total biomass and contribute 15.1 percent of detritivore feeding tracks.
Note the hollow areas in the distal part of some leaf pads and the replacement by clusters of small, isodiametric coprolites. h) Enlargement of the distal leaf-cushion region in (g), showing the distribution of rollte groups at the edge of the central gallery. Slide No. 22,726 {peel 28729-Btop), (i) Tunnel containing microcophelites in secondary xylem of cordaite root, Amyelan. En la rg ment of the region outlined in (c), showing the layered frass. e) Transverse section of a leaf memtier of the Filicalean fern, Botryoptehs, showing in the outer ground tissue a tunnel containing a group of coprolites. f) A cluster of coprolites in a tunnel occurring within a macrocoprolite.
These are (1) coprolite size, (2) coprolite shape, (3) coprolite surface texture, (4) coprolite content, and (5) surrounding plant tissue of the coprolite. Some smaller adult insects are wood borers (Frost, 1959; Hickin, 1975; Eaton and Hale, 1993), but do not produce faecal droppings in the small size range of the roaches described here. Although many pods were present in the late Paleozoic (Almond, 1985) and although some species are often found in decaying wood (Wallwork, 1976), it is unlikely that myuipeds produced any of the tracks observed in our study.
In contrast, many subadult insects, especially larvae of the endopterygote Coleóptera, Díptera, Lepidoptera and Hymenoptera, are wood borers and produce large quantities of faecal pellets containing particles of wood and other hardened plant tissues (Hickin, 1975; Mamaev, 1977). ; Crowson, 1981; Eaton and Hale, 1993). Virtually all textual and photographic documentation of wood boring by modern oribatid mites in history refers to phthiracaroids and euphtfracaroids, especially the prominent genera Phthiracarus and Steganacarus of the Phthiracaridae and Oribotritia of the Oribotritüdae (Jacot Riha, 1951; Schuster, 1956; Wallwork, 1957). ; Haq, 1982; Ponge, 1988; Soma, 1990). In one of the few studies of site-specific oribatid mite communities occurring in wood, Wallwork (1957) documented the presence of tritrophic interactions.
From this window of fossil pits on plants, modern patterns of tissue wear are indistinguishable from those of the Pennsylvanian fossil record of coal swamp plants. These two dense occurrences result from the different geologic and taphonomic settings of the mite and oribatid insect track fossils, as well as the relative duration and, thus, greater likelihood of stratigraphic completeness of the insect track record. For the Early and Middle Pennsylvanian, until the disappearance of the lycopsid-dominated coal swamps in the late Middle Pennsylvanian (PhUhps et al. 1974, Phillips and Peppers, 1984), the real evidence supports detritivity as the basis for consumption not only of hard plant tissues such as wood, bark and sclerenchyma, but also most sofl^r tissues.
This transition occurred when Psoronia tree ferns achieved ecological dominance in lowland wetlands across large parts of the Euramerican equatorial belt. From available fossil deposits and modern ecological studies, we have determined some of the ecological roles that oribatid mites served in the decomposition of plant tissue in Paleozoic coal swamps.
We thank David Grimaldi of the Department of Entomology at the American Museum of Natural History, Eandi Hansen of the Institute of Ecology at the University of Georgia, David Headrick of the Department of Entomology at the University of California, and Francis Hueber of the Department of Paleobiology at the National Museum of Natural History for providing comments from unpublished data. Part of this work was done while CCL was at the University of Illinois at Urbana-Champaign as a postdoctoral fellow. 41 from the Evolution of Terrestrial Ecosystems Consortium at the National Museum of Natural History. mes, Oribatei) fitnin Upper Cretaceous of Taymyr Paleonto-k^cal Journal, v.
CALL, V.B., og TIDWELL, W,D• 1988, Fossil wood from the Miocene of Wall Canyon, Northwestern Nevada: American Journal of Botany, v. 1991, Fossil evidence for plant-arthropod interactions in the Palaeozoic and Me - sozoisk: Philosophical Transactions of the Royal Society of London, V.333B, s. CiCHAN, MA., og TAYLOR, T.N., 1982, Wood-borings in Premnoxy- Ion: Plant-animal interactions in the Carboniferous: Palaeogeography, Palaeoklimatology, Palaeoecology, v.
COHEN, A.D., and SPACKMAN, W., 1977, Oi^anic phytogenic sediments and sedimentary environments in the Everglades-mangrove complex: Palaeontographica, v. (Acari; Oribatida); Journal of Natural History, vol. CROSS, A.T., and PHILLIPS, T.L., 1990, Coal-forming plants through time in North America; International Journal of Coal Geology, v, 16, p.
EDWABDS, D., SELDEN, P.A, RICHARDSON, J.B., ken AX, L• 1995, Coprohtes a kas ebidensia para kadagiti panagtitinnulong ti mula-animal kadagiti Siluro-De-vuian a terrestrial nga ekosistema; Nakaparsuaan, v. GJELSTRUP, P., ken S0CHTIG, U., 1979, Dagiti Cyptostigmatid a tukak (Aca- riña) a nainaig iti RaTnulina silicpjosa (lichens) idiay Bomholm idiay Baltiko: Pedobiology, v. 1979 nga; GoLOSOVA, L.D., DRUK, AY., KARPPINEN, E., ken KISELYOV, S.V., 1985, Subfosil nga oribatid a tukak (Acariña, Oribatei) ti amianan a Siberia; AnnalesEntoinolohia Fennici, v.
GOTO, H.E, 1972, On the structure and function of the mouthparts of the soU-dwelling coUembolan Folsomia candida: Biological Journal of the Liimean Society, v, 4, p. GEIMSTONE, AV• MULLINGER, AM., and RAMSEY, JA, 1968, Further studies on the rectal complex of the mealworm: Philosophical Transactions of the Royal Society of London, v. HAMILTON, W.D., 1978, Evolution and diversity under bark : Symposium of Royal Entomological Society of London, no.
346 LABANDEIRA ET AL
MATTHEWS, J.V., JR., og OVENDEN, L.E., 1990, Late Tertiary Plant Roacrofossils from localities in Arctic/Subarctic North America: A review of the data: Arctic, v. MICHAEL, AD., and GEORGE, CF., 1879, Et bidrag til viden om British Oïibatid•: Journal of the Royal Microscopical Society, v. MITCHELL, M.J. og PARKINSON, D., 1976, Fungal feeding of oribatid mites (Acari: Cryptostigmata) in an aspen woodland sou : Økologi V.
NICHOLSON, PB., BOCOCK, KL• and HEAL, O.W., 1966, Studies on the decomposition of the faecal granules of a centipede (Ghmeris marginata [Villers]): Journal of Ecology, v. PANDE, Y.D., and BEHTHET, P. , 1973, Studies on the food and feeding habits of soil Oribatei in a black pine plantation: Oecologia, v. 1974, Fossil plants and coal: Patterns of change in Pennsylvanian coal swamps of the Illinois Basin: Science, v.
POOLE, T.B., 1959, Dagiti panagadal iti panagtaraon ti Collembola iti maysa a plantasion ti abeto ti Douglas: Proceedings ti Zoological Society ti London, v. 1959 nga; REEVES, R., 1992, Dagiti Carabodes ti akindaya nga Estados Unidos ken ti kabangibang a Kanada (Acari: Oribatida: Carabodidae): Canadian Journal of Zoology, V, 70, p. SAICHUAE, P• GEKSON, U., ken HENIS, Y., 1972, Dagiti panagpalpaliiw iti panagtaraon ken Ufe a pakasaritaan ti mite MJíAíTíS biciliaius (Koch): Biolohia ti Daga ken Biokemistri, v. 1972 nga;
SCOTT, AC, CHALONER, W.G., and PATEHSON, S., 1985, Evidence of pteriophyte-arthropod interactions in the fossil record: Proceedings of the Royal Society of Edinburgh, v. ScoTr,AC., STEPHENSON.J., and CHALOKER, W.G., 1992, Interaction and co-evolution of plants and arthropods during the Paleozoic and Mesozoic: Philosophical Transactions of the Royal Society of London, v. SiMEONE, J.B., 1965, The frass of northeastern United States powder posting beetles: Procef International Con-.
STEFANIAK, 0., en SENICMK, S., 1976, The microflora of the alimentaiy canal ofAchipteria coleopterata (Acariña, Oribatei): Pedobiology, V. TlDWELL,W.D., and ASH, S.R• 1990. stemifer- manophyion en sy spesies van Colorado en Utah, VSA; Pa- laeontographica, v. WALTER, D.E., OT)OWD, D., en BARNES, V., 1994, The forgotten ar- thropods: Foliar mites in the forest canopy; Memoires van die Queensland Museum, v.
