Charniodiscus is a leaf-shaped Ediacaran (terminal Neoproterozoic) fossil with a worldwide distribution, but the scarcity of complete specimens has previously hindered evaluation of its taxonomy and ecology. The presence of hundreds of complete (fronds with stem and disc attached) Charniodiscus specimens from the Avalon Zone of Newfoundland has allowed for detailed morphometric analysis of Charniodiscus specimens and permits determination of characteristics which vary with growth (e.g., stem length, frond width, and disc diameter) versus those that reflect taxonomic differences (e.g., number of primary segments, presence of a distal spine, shape ratios). This has led to the recognition of three species of Charniodiscus in the Mistaken Point biota, including numerous specimens of two new taxa, C. procerus n. sp. and C. spinosus n. sp., and rare specimens of the Australian species C. arboreus. C. procerus n. sp. and C. spinosus n. sp. represent similar, yet ecologically distinct forms of upper-level filter feeders with diverging feeding strategies in order to reduce the competition for resources. Ratio plots and principal components analyses (PCAs) confirm the existence of five (possibly six) morphologically distinct species of Charniodiscus worldwide.

New collections from measured sections provide much of the material for this study. Holcocystis, Atopocystis, and Stummelasma are erected as new genera. Atopocystis mucronata and Stummelasma sulfurense are new species; Holcocystis flexa (Stumm), Stummelasma lonense (Stumm), and S. antelopense (Merriam) are new combinations. Revised coral ranges are integrated with the standard Nevada conodont zones and brachiopod-based faunal intervals. A range chart for 33 Rugosa emphasizes their value for correlation in Icriodus, or brachiopod-poor biofacies of the Great Basin. It also shows that full recovery from the end Lockhovian/early Pragian coral crisis in the region was delayed until the start of the middle Emsian gronbergi Zone. The recovery was accomplished principally by radiation of the Breviphyllidae and Papiliophyllidae, and by immigration of cyathophyllid and other genera.

Updated lists of Rugosa genera present in the Great Basin, Mackenzie, and Appohimchi provinces during the Pragian and early Emsian (kindlei-lenzi zones) and middle to late Emsian (gronbergi-serotinus zones) are given. Qualitative and quantitative data, the latter as Otsuka Coefficients, indicate that the Pragian Great Basin coral faunas can no longer be regarded as part of a temporary westward extension of the Eastern Americas Realm. Nor can they be considered part of the Mackenzie coral province. Genus absence/ presence data show that the Great Basin coral province began with a slow recovery of faunas after the late Lochkovian/early Pragian coral crisis, and ended with the arrival of typical Old World Realm families, including the Ptenophyllidae and Stringophyllidae, within the early Eifelian, costatus Zone. During this time faunas of the Mackenzie coral province were also distinct from those of the exotic Alexander and Farewell terranes of Alaska and British Columbia. The duration of the Devonian Great Basin coral province corresponds closely to the duration of a period of depressed seawater temperatures postulated from the distribution of gypidulinid brachiopods.

Stegerhynchus was perhaps the most common rhynchonellide brachiopod in the Early Silurian (Llandovery) postextinction brachiopod fauna of North America. In shell morphology, it closely resembles the Late Ordovician rhynchonellide Rhynchotrema in having a rostrate shell posterior and simple, strong costae. It differs internally from Rhynchotrema primarily in having a much-reduced septalium (=cruralium). Superficially Stegerhynchus has a conservative, typically simple, rhynchonellide morphology, but detailed biometric analysis of large samples from the >400 m-thick Llandovery (mid-Aeronian to mid-Telychian) tropical carbonate succession of Anticosti Island reveals that the genus underwent significant evolutionary and ecophenotypic changes over about five million years. The shell length/width ratios of Stegerhynchus peneborealis from sediments of a low-energy, muddy substrate tend to be lower than those of S. deltolingulatus new species from high-energy, reef or inter-reef settings. A wider shell and hingeline probably had a greater stability on the soft seafloor. Also a wider shell appears to be associated with a larger (relative to shell size) sulcus size at the anterior margin. The changes in relative sulcus size either represent ecophenotypic variation in response to environmental conditions, or a random effect of evolutionary selection through time. Both multivariate and single-character analyses demonstrate that two important biometric features, the apical angle and shell flank rib number, separate all forms of Anticosti Island Stegerhynchus (middle Aeronian to middle Telychian) from the widely cited European species Stegerhynchus borealis (latest Telychian-Wenlock) from the type area of Gotland, Sweden. The temporal changes of these two characters are interpreted to be evolutionary modifications.

Eleven athyridoid species are described and other related species are revised from the Lopingian (late Permian) of South China and Transcaucasia in southern Azerbaijan and northern Iran. The family Comelicaniidae Merla, 1930 is adopted. It includes six subfamilies, of which Araxathyriinae is proposed as a new subfamily. Comparisons of species based on detailed internal structures indicate that some previously commonly recorded species from South China and Transcaucasia actually belong to different genera. Araxathyris coexisted in the two regions. Comelicania, Gruntallina, Janiceps, Transcaucasathyris, and Comelicothyris are only found in the southern Alps, Hungary, and/or Transcaucasia; whereas Tongzithyris and Rectambitus are restricted to South China. Other new taxa are Transcaucasathyris n. gen., Araxathyris sinensis n. sp., Rectambitus xui n. sp., and R. spondomarginata n. sp.

The Tannuolinidae includes only two known genera—Micrina Laurie, 1986 and Tannuolina Fonin and Smirnova, 1967, both from the Lower Cambrian. They are phosphatic bimembrate small shelly fossils, consisting of two types of sclerites—the mitral and sellate sclerites. These sclerites show basal-internal accretional growth, spaced growth lamellae, carinae (in mitral sclerites of Tannuolina) or teeth (in mitral sclerites of Micrina), and unevenly distributed pores and canals. The scleritome of tannuolinids is poorly known because they are often preserved as disarticulated sclerites. Here we describe Micrina xiaotanensis new species and Tannuolina zhangwentangi Qian and Bengtson, 1989 from the Lower Cambrian Shiyantou and Yu'anshan formations (upper Meishucunian to Qiongzhusian stages) at Xiaotan, eastern Yunnan, South China. The new material not only extends the geographic range of Micrina, previously known only in Australia, but also includes two composite specimens of T. zhangwentangi: one with a pair of dextral and sinistral mitrals juxtaposed along the apertural margin of their decrescent sides, and the other with a smaller sellate ontogenetically merged with the sella of a larger sellate. Perhaps as a result of being contacting or imbricating surfaces, the decrescent, sella, and duplicature sides are also characterized by negative allometry (relative to other sides) and a sparse distribution of pores. The new fossils do not support reconstructions that place a sellate and a mitral sclerite, respectively, at the anterior and posterior end of the Tannuolina animal, in a way similar to Halkieria evangelista Conway Morris and Peel, 1995. Instead, they are consistent with the traditional view that the scleritome of Tannuolina consisted of four anterior–posterior files of sclerites: two opposing mitral rows flanked by two imbricated sellate series. The bimembrate Micrina may or may not have had a similar scleritome. If Tannuolina and Micrina form a monophyletic group outside the total group of brachiopods, then Micrina is likely to have had a multisclerite scleritome similar to that of Tannuolina. This implies that microstructural similarities between the tannuolinids and some linguliformean brachiopods are probably symplesiomorphic or convergent. Alternatively, Tannuolina and Micrina may represent stem groups leading to the linguliformeans while Halkieria represents a stem group leading to the calcareous brachiopods—a radical hypothesis that would imply that the two brachiopod groups independently evolved the bivalved body plan.

Two new species of gastropods belonging to the volutid genus Adelomelon Dall, 1906 are described from Tertiary strata of Patagonia, Argentina. Adelomelon posei n. sp. was found in the lower part of the Gran Bajo del Gualicho Formation (Río Negro Province), which is currently dated as Late Eocene through Middle Miocene in age. Adelomelon valdesiense n. sp. comes from the Puerto Madryn Formation (Chubut Province) of early Late Miocene age. Both species are characterized by angulated biconical teleoconch whorls and strongly developed rows of axial nodes, similar in shape to those of some Recent species of Adelomelon, but positioned differently. Discovery of two new species of the genus Adelomelon in the Tertiary of Patagonia significantly extends the known stratigraphic range of this genus from Late Eocene(?)–Miocene to Recent.

Cambrian ptychopariids have defied most attempts at higher classification. Even at the generic level, there is no consensus as to what constitutes identification criteria in these morphologically conservative trilobites. The problem is more acute when there is a lack of knowledge about the different sclerites of species, the presence of species with morphologies intermediate between two genera, the naming of genera where incompletely known or poor quality specimens were used for type species, and the use of character checklists to generate diagnoses for higher taxa. This study on the kochaspid trilobites (Lower to Middle Cambrian) uses several available representatives of each genus to alleviate or assess some of these problems. Successive reweighting of characters is used for the assessment of 70 characters among 66 taxa as to their importance in forming clades. Results of this study include five important points about ptychopariid classification: 1) knowledge about noncranidial sclerites is important for the proper placement of taxa that have generalized morphologies; 2) in contrast, taxa that have more derived cranidial morphology can be accurately placed within a clade; 3) intermediate morphologies illustrate a close link between genera, but these forms can present nomenclatural problems in their placement; 4) although genera defined by type species based on incompletely described or poorly preserved specimens can create nomenclatural nightmares, other species assigned to these genera are not dependent on their previous taxonomic assignment for their placement in the cladogram; and 5) checklists of morphological characters cannot be used to recognize ptychopariid groups, since the level of homoplasy is too high and there are too many reversals of character states within a clade. Instead, a list of character states that typify a taxonomic group is more useful and will lead to a more stable classification.

This cladistic analysis of kochaspid trilobites indicates that 64 of the 70 characters were useful in the formation of clades. Fifty-six cranidial, librigenal, thoracic, and pygidial characters were useful in typifying larger and smaller clades. The analysis also indicates that Eokochaspis, Nyella, and Onchocephalus are polyphyletic. Reassignments based on the cladistic analysis include Schistometopus collaris to Caborcella, and Syspacephalus obscurus to Mexicella.

The oldest known thrips, order Thysanoptera, are described from the Late Triassic of Virginia and Kazakhstan: Triassothrips virginicus Grimaldi and Fraser, new genus and species (Cow Branch Formation: Carnian), and Kazachothrips triassicus Shmakov, new genus and species (Tologoy Formation: Carnian–Norian). Prior to this the oldest definitive thysanopterans were from the Late Jurassic of Kazakhstan (Kimmeridgian), some 80 My younger. Well-preserved, relatively complete, wing venation indicates the Triassic thrips are phylogenetically the basalmost thysanopterans, and their venation even allows identification and homologizing the highly reduced veins in Recent thrips. Another basal thrips is described from mid–Cretaceous (Turonian) amber of New Jersey, Cretothrips antiquus Grimaldi, new genus and species, which is similar to several Recent genera of Aeolothripidae. A phylogenetic hypothesis of basal relationships in Thysanoptera based on wing venation supports a basal relationship for Aeolothripidae and derived position for Phlaeothripidae among Recent families.

Application of new preparation techniques for cleaning and study of fossil crabs to Dromiopsis rugosa (Schlotheim, 1820), from the late middle Danian limestone in the Fakse quarry, Denmark, has revealed remarkable detail of the carapace surface and epibionts infesting inner and outer surfaces of the carapace. Epibionts, identified as clionid sponges, scleractinian corals, cheilostome and ctenostome bryozoans, serpulid worms, and brachiopods, are interpreted as having attached to molted carapaces after the molted carapace had been released.

Epibionts on both living and fossil decapod crustaceans may serve as valuable proxies for paleoecological factors such as behavior and environment. Prevalence of epibionts, as observed primarily on the carapaces of fossil brachyurous decapod crustaceans, appears to be less than observed on living crabs, based upon observations in the literature, and from the study of a limited preserved biological and fossil collection. Among these factors, the three most important are that many extant epibionts do not possess skeletal structures and, therefore, are unlikely to be preserved; the epicuticle upon which epibionts attach to living brachyurans is lightly calcified and tends to be lost readily as a result of taphonomic processes; and the most common mode of preservation of fossil brachyurans is in concretions which tend to break open and leave a layer of cuticle on the counterpart, thus obscuring the potential surface of attachment of epibionts. Other factors such as the life habits of the crab, whether burrowing, burying, or remaining above the substrate; lifestyle, whether benthic or pelagic; and duration of the intermolt phase of the organism also play important roles in potential prevalence of epibionts. Careful preparation of part and counterpart remains of brachyurans as well as reference to the occurrence of epibionts in systematic studies will enhance knowledge of the host and epibiont.

This paper offers a preliminary description of a plesiosaur (Reptilia: Sauropterygia) from the Lower Toarcian Posidonienschiefer near the village of Holzmaden in Baden-Württemberg, Germany, and discusses its phylogenetic relevance. This new taxon, Plesiopterys wildi new genus and species, is remarkable in its retention of several plesiomorphic features. A phylogenetic analysis places Plesiopterys as the sister group of the Plesiosauroidea, and as such the taxon is the most basal taxon yet known on the branch leading to this major clade. Plesiopterys possesses a high count of cervical vertebrae and a relatively small head, yet the limbs and limb girdles are plesiomorphic in proportion. The skull displays a mosaic of features, reminiscent of both Thalassiodracon and the rhomaleosaurids in some characters, yet similar to Plesiosaurus in others. The basicranium is plesiomorphic and resembles that of nothosaur-grade sauropterygians in several respects. A faunal comparison between Holzmaden and the Lower Toarcian deposits on the Yorkshire coast of England concludes that the Holzmaden fauna is more plesiomorphic than the roughly coeval Yorkshire fauna in two of three plesiosaur subclades.

We present a rank-free phylogenetic nomenclature for 25 well-established ancient clades of living turtles. This is the first attempt to document fully the nomenclatural history of a clade with the intent of proposing a coherent nomenclatural system to replace the traditional rank-based nomenclature. Because of the imperative to retain connectivity to the literature for information retrieval, due consideration is given to balancing the desire to develop a consistent system against the desire to conserve traditional associations between names, taxa (i.e., clades), and characters. Novel issues and problems that emerged during this review include: the unclear name/clade association of traditional names; the creation of synonymy lists from which to choose a name; difficulties associated with selecting a single criterion for choosing among multiple ‘subjectively synonymous’ names; identifying authorship for a converted traditional name; and the potential loss of nomenclatural information due to ‘functional homonyms.’ This work may provide a useful road map to those intent on converting their traditional rank-based nomenclatures to explicitly phylogenetic nomenclatures under the precepts of the PhyloCode.