The preservation of compounds of biological origin (nucleic acids, proteins, carbohydrates, lipids, and resistant biopolymers) in terrigenous fossils and the chemical and structural changes that they undergo during fossilization are discussed over three critical stratigraphic levels or “time slices.” The youngest of these is the archeological record (e.g., <10 k.y. B.P.), when organic matter from living organisms undergoes the preliminary stages of fossilization (certain classes of biomolecule are selectively preserved while others undergo rapid degradation). The second time slice is the Tertiary. Well-preserved fossils of this age retain diagenetically modified biomarkers and biopolymers for which a product-precursor relationship with the original biological materials can still be identified. The final time slice is the Carboniferous. Organic material of this age has generally undergone such extensive diagenetic degradation that only the most resistant biopolymers remain and these have undergone substantial modification. Trends through time in the taphonomy and utility of ancient biomolecules in terrigenous fossils affect their potential for studies that involve chemosystematic and environmental data.

Considerable numbers of exceptionally preserved conodont apparatuses with hyaline elements are present in the middle-upper Darriwilian (Middle Ordovician, Whiterockian) Winneshiek Konservat-Lagerstätte in northeastern Iowa. These fossils, which are associated with a restricted biota including other conodonts, occur in fine-grained clastic sediments deposited in a meteorite impact crater. Among these conodont apparatuses, the common ones are identified as Archeognathus primus Cullison, 1938 and Iowagnathus grandis new genus new species. The 6-element apparatus of A. primus comprises two pairs of archeognathiform (P) and one pair of coleodiform (S) elements. The 15-element apparatus of I. grandis n. gen. n. sp. is somewhat reminiscent of the prioniodinid type and contains ramiform elements of alate (one element) and digyrate, bipennate, or tertiopedate types (7 pairs). Both conodont taxa are characterized by giant elements and the preservation of both crowns and basal bodies, the latter not previously reported in Ordovician conodont apparatuses. Comparison of the apparatus size in the Winneshiek specimens with that of the Scottish Carboniferous soft-part-preserved conodont animals suggests that the Iowa animals were significantly larger than the latter. The apparatus of A. primus differs conspicuously from the apparatuses of the prioniodontid Promissum from the Upper Ordovician Soom Shale of South Africa although the apparatus architecture of I. grandis n. gen. n. sp. shows some similarity to it. Based on the Winneshiek collections, a new family Iowagnathidae in Conodonta is proposed.

A single specimen of a new species of the chasmataspidid Diploaspis Størmer, 1972 is described from the upper Silurian (Pridoli) Phelps Member of the Fiddlers Green Formation (Bertie Group) in Herkimer County, New York State, USA. Diploaspis praecursor sp. nov. is distinguished by the shape of the posterolateral margins of the buckler, which are drawn out into angular epimera, and by the lack of elongate tubercles on the postabdomen. This discovery increases the taxonomic diversity of the Bertie Group by extending the geographic extent of Diploaspididae into North America. D. praecursor pre-dates previously known species of Diploaspis by more than 10 million years.

Arthrophycus alleghaniensis is a well-known trace fossil common in the lower Silurian of the Appalachian Basin, eastern U.S.A. Despite the distinctive morphology of this trace, with few exceptions, hypotheses about the nature of the tracemaker have not extended beyond that of a long-bodied, segmented organism. A single organic compression of a long-bodied arthropod discovered in shale interbedded with sandstones containing A. alleghaniensis in the Silurian (Llandovery) Tuscarora Formation at Mann Narrows, Pennsylvania is described. The specimen preserves evidence of two trunk tagmata: an anterior tagma with tergites extending into broad, rectangular pleurae, and a posterior tagma bearing long, curved spines. Head and appendages are not preserved. The new arthropod, Pleuralata spinosa n. gen. n. sp., matches the size and general morphology required for an A. alleghaniensis tracemaker. Precise systematic affinities of this new arthropod could not be determined. This discovery supports the conclusion that the tracemakers of various Arthrophycus ichnospecies are likely poorly preserved, and presently unknown, members of the Ecdysozoa.

The Middle Cambrian Spence Shale Member (Langston Formation) and Wheeler and Marjum Formations of Utah are known to contain a diverse soft-bodied fauna, but important new paleontological material continues to be uncovered from these strata. New specimens of anomalocaridids include the largest and smallest near complete examples yet reported from Utah. New material of stem group arthropods includes two new genera and species of arachnomorphs: Nettapezoura basilika and Dicranocaris guntherorum. Other new arachnomorph material includes a new species of Leanchoilia comparable to L. protogonia Simonetta, 1970; Leanchoilia superlata? Walcott, 1912; Sidneyia Walcott, 1911a; and Mollisonia symmetrica Walcott, 1912. L. protogonia from the Burgess Shale is confirmed as a separate species and is not a composite fossil. The first example of the trilobite Elrathia kingii preserving traces of the appendages is described. In addition, new material of the bivalved arthropods Canadaspis Novozhilov in Orlov, 1960; Branchiocaris Briggs, 1976; Waptia Walcott, 1912; and Isoxys Walcott, 1890 is described.

Most of the specimens of Myoscolex ateles Glaessner, 1979, the most abundant soft-bodied taxon in the Big Gully fauna from the Lower Cambrian Emu Bay Shale of South Australia, preserve only the phosphatized trunk muscles, in striking contrast to the organic residues that characterize other Burgess-Shale-type biotas. This is the oldest phosphatized muscle tissue and the first thus far reported from the Cambrian. The extent of phosphatization implies a source in addition to the animal itself, and this is reflected in high levels of phosphate in the Big Gully sequence compared to other shales. The apparent anomaly posed by the extensive preservation of labile muscle tissue as opposed to the more decay resistant cuticle is explained by the role of bacterial processes in the preservation of soft tissues. New specimens of Myoscolex reveal a variable number of trunk somites with possible tergites, and flap-like appendages. There is evidence for at least three eyes on the head, and a proboscis may have been present. An annelid affinity is rejected and Myoscolex is reinterpreted as an Opabinia-like animal with possible affinities with the arachnomorph arthropods.

A new synziphosurine (Chelicerata: Xiphosura) is described from the Late Llandovery (Silurian) Konservat-Lagerstätte of Waukesha, Wisconsin, USA. Venustulus waukeshaensis n.gen. and sp. is characterized by a semicircular carapace with a slightly procurved posterior margin lacking genal spines and an opisthosoma composed of 10 freely articulating segments, divided into a preabdomen of seven segments with blunt pleurae and a postabdomen of three segments lacking pleurae. The tail spine is short and styliform. This is the earliest known unequivocal synziphosurine, extending their fossil record from the Wenlock to the Llandovery, and only the second species to be described with prosomal appendages; the presence of six pairs (a pair of chelicerae and five pairs of walking legs) contrasts with the seven in the synziphosurine Weinbergina opitzi, but is comparable to the number in modern horseshoe crabs. V. waukeshaensis n. gen. and sp. is not assigned to a family here pending a wider revision, but it bears most resemblance to the Weinberginidae.

The exceptionally preserved Triassic (Anisian) Grès à Voltzia fauna from the Vosges of northeastern France is compared with four major Carboniferous Konservat-Lagerstätten. The problem of comparing faunas with different types of preservation and degrees of taxonomic determination is addressed with a newly devised similarity coefficient. This coefficient quantifies and combines data from different levels in the taxonomic hierarchy and allows comparisons between biotas in a consistent direction regardless of relative diversity. The rank order of similarity between the four Carboniferous Konservat-Lagerstätten and the Grès à Voltzia is as follows: 1. Mazon Creek (Westphalian D) of Illinois; 2. Glencartholm (Visean) of southern Scotland; 3. Bear Gulch (Namurian) of Montana; and 4. Blanzy-Montceau (Stephanian) of France. These occurrences represent conditions transitional between nearshore fully marine and fresh water. The Grès à Voltzia fauna is significantly closer to the Mazon Creek fauna than to the others; the taxonomic overlap with Blanzy-Montceau and Bear Gulch is limited.

Stratigraphic age has an insignificant influence on the result; indeed, the fauna closest in age to the Grès à Voltzia, that of Blanzy-Montceau, is least similar. Taphonomic factors are important in determining the range of organisms preserved. The Glencartholm fauna is represented only by forms with either mineralized or robust chitinous skeletons, implying a greater degree of decay prior to the onset of diagenetic mineralization than in the other Konservat-Lagerstätten. Environment, however, is the major control on similarity. The Mazon Creek biota, like that of Grès à Voltzia, represents settings transitional between terrestrial and marine-influenced delta. Groups common to both Konservat-Lagerstätten include medusae, brachiopods, polychaetes, bivalve and gastropod molluscs, limulids, scorpions, spiders, branchiopods, ostracodes, malacostracans, cycloids, euthycarcinoid and myriapod uniramians, insects, fish, and tetrapods. There is a striking continuity between the faunas of Carboniferous and Triassic transitional sedimentary environments. Groups that were adapted to fluctuating conditions (e.g., shifting salinity) show strong congruence at the family and lower levels and were little affected by Permian extinctions. The major taxonomic contrasts are in the eumalacostracans and insects: many of the groups represented in the Grès à Voltzia appeared in the Permian and radiated across the Permo-Triassic boundary as Paleozoic forms became extinct.

Gould's Wonderful Life (1989) was a landmark in the investigation of the Cambrian radiation. Gould argued that a number of experimental body plans (“problematica”) had evolved only to become extinct, and that the Cambrian was a time of special fecundity in animal design. He focused attention on the meaning and significance of morphological disparity versus diversity, and provoked attempts to quantify disparity as an evolutionary metric. He used the Burgess Shale as a springboard to emphasize the important role of contingency in evolution, an idea that he reiterated for the next 13 years. These ideas set the agenda for much subsequent research. Since 1989 cladistic analyses have accommodated most of the problematic Cambrian taxa as stem groups of living taxa. Morphological disparity has been shown to be similar in Cambrian times as now. Konservat-Lagerstätten other than the Burgess Shale have yielded important new discoveries, particularly of arthropods and chordates, which have extended the range of recognized major clades still further back in time. The objective definition of a phylum remains controversial and may be impossible: it can be defined in terms of crown or total group, but the former reveals little about the Cambrian radiation. Divergence times of the major groups remain to be resolved, although molecular and fossil dates are coming closer. Although “superphyla” may have diverged deep in the Proterozoic, “explosive” evolution of these clades near the base of the Cambrian remains a possibility. The fossil record remains a critical source of data on the early evolution of multicellular organisms.

Cutan, a resistant non-hydrolyzable aliphatic biopolymer, was first reported in the cuticle of Agave americana and has generally been considered ubiquitous in leaf cuticles along with the structural biopolyester cutin. Because leaves and cuticles in the fossil record almost always have an aliphatic composition, it was argued that selective preservation of cutan played an important role in leaf preservation. However, the analysis of leaves using chemical degradation techniques involving hydrolysis to test for the presence of cutan reveals that it is absent in 16 of 19 taxa (angiosperm and gymnosperm), including many previously reported to contain cutan on the basis of pyrolysis data. Cutan is clearly much less widespread in leaves than previously thought, and its presence or absence does not exert any major bias on the preservation of leaves in the fossil record. In the absence of cutan, other constituents—cutin, plant waxes, and internal plant lipids—are incorporated into the geomacromolecule and contribute to the formation of a resistant aliphatic polymer by in situ polymerization during diagenesis.

A series of experiments was carried out to investigate the nature and controls (oxygen, microbial populations, agitation) on the degradation of soft tissues. Decay was monitored in terms of morphological change, weight loss, and change in chemical composition in the polychaete Nereis virens. Polychaetes include a range of tissue types of differing chemical composition and preservation potential: muscle, cuticle, setae, and jaws. Regardless of conditions, all the muscle had broken down and fluid loss through the ruptured cuticle had reduced the carcass to two dimensions within 8 days at 20°C. In most cases some cuticle, in addition to the jaws and setae, remained after 30 days. Where oxygen was completely eliminated, the rate of decay of the more volatile issues was significantly reduced. The degree of both osmotic uptake of water by the carcass and changes in water pH differed depending on whether the system was open or closed to oxygen diffusion. Autolytic and chemical processes are not sufficient to fully degrade the carcass in the absence of bacteria. Where internal bacteria are present, the presence or absence of water column bacteria made little difference to decay rate. Initial degradation (in the first 3 days) affects mainly the lipid fraction and the collagen of the cuticle. Later decay reduces the nonsoluble protein and increases the relative proportion of refractory structural components (tanned chitin and collagen) to more than 95% by day 30. Thus, only the sclerotized tissues are likely to survive beyond 30 days in the absence of early diagenetic mineralization. The sequence of degradation predicted from the relative decay resistance of macromolecules in the sedimentary record (protein → carbohydrate → lipid) is not, therefore, a consistent indicator of the preservation potential of structural tissues which incorporate them.

The experiments reveal five stages in the decay of polychaete carcasses; whole/shriveled, flaccid, unsupported gut, cuticle sac, jaws and setae. All are represented in the fossil record. This allows an estimation of how far decay proceeded before it was halted by the fossilization process. The most complete preservations occur in the Cambrian where the Burgess Shale preserves evidence of muscle tissues. Traces of the gut and cuticle are more widely preserved, as at Mazon Creek, Grès à Voltzia, Solnhofen, and Hakel. Preservation varies within Konservat-Lagerstätten. The most common whole body preservation includes only the more recalcitrant tissues, jaws (where present) and setae, with an impression of the body outline. The stage of decay can be used as a taphonomic threshold, to provide an indication of how significantly the diversity of an exceptionally preserved biota is likely to have been reduced by taphonomic loss.

An international conference on “Fossil Arthropods as Living Animals” was held at the Royal Society of Edinburgh on October 25–27, 1984. Major international conferences devoted to fossil arthropods are rare events. The previous one, which was held in Oslo in July 1973 as a NATO Advanced Study Institute, resulted in a volume on “Evolution and Morphology of the Trilobita, Trilobitoidea and Merostomata” (Martinsson 1975). Participants in the Edinburgh meeting heard 28 contributions covering all aspects of arthropod paleobiology. Most are published as a special issue of the Transactions of the Royal Society of Edinburgh: Earth Sciences (Waterston 1985). All four major arthropod groups are treated (trilobites, crustaceans, chelicerates, and uniramians), as well as trace fossils and some groups of problematic status.

Disparity is a measure of the range or significance of morphology in a given sample of organisms, as opposed to diversity, which is expressed in terms of the number (and sometimes ranking) of taxa. At present there is no agreed definition of disparity, much less any consensus on how to measure it. Two possible categories of metric are considered here, one independent of any hypothesis of relationship (phenetics), the other constrained within an evolutionary framework (cladistics).

The Early Cambrian radiation was clearly a period of significant morphologic and taxonomic diversification. However, we question the interpretation of its first generation products as numerous body plans at the highest level. Four phenetic and two cladistic measures have been used to compare disparity among Cambrian arthropods with that in the living fauna. Phenetic methods assessing character-state variability and the amount of morphological attribute space occupied yield similar results for Cambrian and Recent arthropods. Assessments of disparity within a taxonomic framework rely on the identification of particular characters that delineate higher level body plans. This requires a phylogenetic interpretation, a cladistic investigation of hierarchical structure in the data. Both sets of arthropods fall within the same major clades, and within this cladistic framework the amount of character-state evolution in the two groups is comparable. None of these methods identifies markedly greater disparity among the Cambrian compared with the Recent taxa.

Although measures of disparity are applied here to a consideration of the Cambrian radiation, the metrics clearly have a much wider potential for estimating macroevolutionary trends independently from existing taxonomic frameworks. Geometric morphometry is ideal for measuring morphological variety at lower taxonomic levels, but it requires the recognition of homologous landmarks in all the forms under comparison, or the identification of entire homologous structures. Conventional phenetics has much wider application as it can operate on data coded as discrete homologous character states (this facility is also a requirement of cladistics), which are a more appropriate basis for comparing disparity in markedly dissimilar forms.

A new genus and species of synziphosurine (Chelicerata) is described from the Silurian (Wenlock) Scotch Grove Formation Konservat-Lagerstätte in Clinton County, Iowa. Camanchia grovensis n. gen. n. sp. is characterized by a sub-triangular carapace, ten opisthosomal segments divided into a preabdomen of seven and a postabdomen of three, and a tuberculate ornament on the carapace and pleural margins. A single new specimen from the same location is assigned to Venustulus waukeshaensis, originally described from the Late Llandovery Waukesha Konservat-Lagerstätte of Wisconsin. A comparison of the musculature of C. grovensis with that of living Limulus polyphemus and the Jurassic Mesolimulus walchi from Nusplingen, Germany shows that it is much simpler, consistent with the status of synziphosurines as stem xiphosurids.

The Lower Permian (Late Wolfcampian) marginal marine facies of the Robledo Mountains Member (Hueco Formation) of the Robledo Mountains, New Mexico, contains a diverse ichnofauna dominated by vertebrate trackways. Four new arthropod ichnotaxa are described. Tonganoxichnus robledoensis new ichnospecies, consists of repeated small traces comprising imprints of anteriorly directed legs, an elongate tapering abdomen, and a thin tail. Hedriumichnus apacheensis new ichnogenus and ichnospecies consists of isolated small traces comprising imprints of laterally-directed legs, a broad tapering abdomen, and a short tail. Rotterodichnium major new ichnospecies is a large trace with imprints of the head and thorax, a long thin abdomen and three pairs of legs, increasing in length posteriorly. Quadrispinichna parvia new ichnogenus and ichnospecies consists of four diverging or sub-parallel linear or curvilinear imprints of approximately equal length.

Tonganoxichnus, previously known from the Upper Carboniferous of eastern Kansas, is interpreted as produced by a jumping monuran (an extinct group of wingless insects). Hedriumichnus, known only from the Robledo Mountains, is interpreted as the resting trace of a nymph of a primitive Ephemeroptera or Plecoptera. Rotterodichnium, previously known from the Lower Permian of Germany, is interpreted as the resting trace of a large dragonfly-like form (Protodonata, Odonata, or Megasecoptera). Quadrispinichna, previously recorded but not named, from the Lower Permian Ecca succession of South Africa, is interpreted as a resting trace of a crustacean. These rare traces increase our understanding of the diversity and behavior of nonmarine arthropod communities in the Lower Permian.

The morphology of Tuzoia is reinterpreted in the light of abundant new specimens from the Middle Cambrian Burgess Shale (British Columbia, Canada) and Kaili (Guizhou, China) Lagerstätten. Tuzoia was a very large (up to 180 mm long) bivalved arthropod with a nonmineralized domelike carapace strengthened by prominent pointed features and often flanked by a lateral ridge bearing a spiny frill. The reticulate pattern of Tuzoia is comparable with that of present-day crustaceans (e.g., myodocope ostracods) and is interpreted as a structural compromise between exoskeletal lightness and high resistance to mechanical stress. Tuzoia had a pair of large, stalked, spherical, possibly compound eyes facing forward. Flagella-like antennae protruded through the anterior notch. No other appendages are known except possible filamentous setae underlying the carapace. Tuzoia typically occurs as laterally (lc) or dorsoventrally (dvc) compacted carapaces or single valves. Each type (lc or dvc) emphasizes particular aspects of the morphology (e.g., spiny lateral ridge, ventral margin) that were often interpreted as specific differences by previous authors. A revision of Tuzoia validates only 7 of the 23 named species. Tuzoia is placed tentatively within a group of large bivalved arthropods along with Isoxys and the possible ancestors of Thylacocephala (Lower Cambrian–Upper Cretaceous). In the Middle Cambrian, Tuzoia occurs across Laurentia, South and North China, and the Perigondwanan area (Bohemia) within a relatively narrow subtropical belt, indicating a high dispersal capability and possible latitudinal control on its distribution. Functional morphology, taphonomy, and the distributional pattern indicate that Tuzoia was a free-swimming arthropod.

Since Dolf Seilacher coined the term Konservat-Lagerstätten in 1970, these deposits have migrated from the margins to the mainstream of paleontological research. With greater understanding of the controls on their occurrence, new examples of exceptional preservation continue to be discovered. They provide critical data for phylogenies and stratigraphic ranges. Together with molecular data, they calibrate the history of many infrequently preserved taxa. Ostracods, tiny crustaceans with a biomineralized carapace, illustrate the importance of recent discoveries in Konservat-Lagerstätten. The rare examples with fossilized appendages are preserved in a diversity of ways, organically or through authigenic mineralization. They confirm that ostracods were present at least by the late Ordovician, provide evidence of relationships obscured by the morphology of the routinely preserved valves, and extend the stratigraphic range of particular groups. They reveal extraordinary features of the soft-tissue anatomy of ostracods, including reproductive morphology and strategy. While other taxa would provide equally compelling examples of research progress, it is clear that the concept of exceptional preservation is expanding. Future discoveries and new analytical methods will match the reconstruction of coloration in feathered dinosaurs, for example, for unexpected novelty.

We consider the reinterpretation of Bethia by Bassett et al. (2008) to be flawed in several regards. Details of the pedicle rootlets and wrinkles strongly imply a soft-tissue structure rather than calcified sheath. The ornament is unusual, but equally so under either an orthide or a plectambonitoidean model. The reinterpretation of the ‘deltial plates’ as ‘chilidial plates’ is likely correct, but argues against a plectambonitoidean affinity by implying that the pedicle emerges between the valves. Other arguments presented in favour of a plectambonitoidean affinity are also discussed; we consider them unpersuasive. Finally, we contend that Bethia is sufficiently well characterised to deserve a taxonomic name.