It has been proposed previously that the northern Mississippi Valley Sunwaptan trilobite genus Dikelocephalus comprises 26 species. Morphometric analyses demonstrate that many of the criteria that had been used to define species of Dikelocephalus are invalid and additional analysis of biostratigraphically and biogeographically constrained collections is necessary before the taxonomic status of Dikelocephalus can be fully resolved. Our results indicate that infrageneric morphological variation in Dikelocephalus is continuous and lacks gaps that could be the basis for establishing multiple species. Many of the characters shown to be taxonomically insignificant in Dikelocephalus are also widely used in the definition of other trilobite taxa. This suggests that the species-level taxonomy of many trilobites may be substantially oversplit. Recognition of widespread oversplitting will have important consequences for biostratigraphic zonations, paleogeographic distributions, and estimates of taxonomic diversity.

A well-preserved highly diverse radiolarian fauna was discovered from the Upper Permian Dalong Formation in Guangxi, South China. A new genus and 19 species are described in this paper. Zhuangodiscus n. gen. belongs to the Family Relindellidae Kozur and Möstler. The 19 species include eight new species (Albaillella bialata, Neoalbaillella camarata, Neoalbaillella cephalota, Zhuangodiscus biacanthus, Zhuangodiscus orthacanthus, Zhuangodiscus pentacanthus, Tetratormentum nandanensis, Octatormentum yaoi) and 11 undetermined species. A new radiolarian assemblage, Neoalbaillella camarata Assemblage is proposed, which is located at the upper part of Neoalbaillella optima Assemblage Zone, corresponds well with the Albaillella yaoi Zone.

Fossil echinoderms are a rich source of information concerning biotic interactions. In this study we analyzed the premortem encrustation of the highly specialized Middle Devonian rugose corals Aspasmophyllum crinophilum and ?“Adradosia” sp. on camerate crinoid stems. Aspasmophyllum infested living crinoid stems by sclerenchymal outgrowth that formed a skeletal ring but ?“Adradosia” sp. encrusted the stems rapidly, without building a ring. These coral-crinoid biocoenoses indicate a settlement advantage for the rugose corals within densely populated communities of the lower Givetian. The corals could be interpreted as large epizoozoans that benefited as secondary tierers reaching relatively high tiering levels. It also suggests the ability for the affected crinoids to repel the coral by overgrowing the corallite with a local increased stereomic growth. Because the crinoid axial canals are not penetrated, the corals cannot be considered as predators or parasites of crinoids. Therefore, the described biocoenosis is interpreted as commensalism. The species A. crinophilum is redescribed, and a neotype is defined, because of the loss of the initial types. Two types of ichnofossils can be attributed to the premortem encrustation of both corals. They are described as Ostiocavichnus n. ichnogen. and are attributed to the stereomic response of the infested hosts. These swellings are characterized as either elliptical (Ostiocavichnus ovalis n. ichnogen. n. ichnosp. due to the assumed reaction of A. crinophilum) or subcircular concavities (O. rotundatus n. ichnogen. n. ichnosp. due to the reaction of ?“Adradosia sp.”).

Alphacrinus mansfieldi new genus and species from the Middle Tremadoc Series (Early Ibexian), near the base of the Ordovician, is the oldest known disparid crinoid. A new family, Alphacrinidae, receives this monospecific genus. Alphacrinus's character mosaic includes primitive traits unknown among other disparids, auguring for disparid origin from a more complexly plated, less standardized antecedent, and echoing the evolutionary progression documented for camerates and cladids. Disparids are diagnosed as those crinoids expressing an arm-like branch from the C ray. Morphologic progression indicates this distinctive trait evolved by modification of CD interray plates, not as an outgrowth from the C ray.

All previously known late Ordovician and Silurian trimerellides of Kazakhstan are reviewed and reillustrated, together with some recently discovered taxa, including the late Caradoc-Ashgill Palaeotrimerella medojevi new species from the Chu-Ili Range, the late middle Ashgill Gasconsia cf. worsleyi Hanken and Harper, and Silurian Dinobolus cf. hubeiensis Rong and Yang, both from Central Kazakhstan. Kazakhstanian terranes appear to contain the oldest-known trimerellide faunas from late Llandeilo to early Caradoc. The observed geographic distribution of Ordovician trimerellides may be explained as the result of two major migrations from the Kazakhstanian terranes: 1) during the early Caradoc, to Gondwana and North America; 2) during the late Caradoc, to Baltica and Angaria. All local trimerellide lineages in Kazakhstan became extinct just before the Hirnantian, and were replaced in the Llandovery by new forms, probably of Chinese origin.

A detailed taxonomical description of scleractinian corals from the Maastrichtian of Mexico (Cardenas Formation) is given for the first time. the coral association comprises 16 taxa which belong to 9 families: Dictuophyllia conferticostata (Vaughan), Cladocora jamaicaensis Vaughan, Cladocora gracilis (d'Orbigny), Antiguastrea cellulosa (Duncan), Multicolumnastraea cyathiformis (Duncan), Placocoenia major Felix, Siderastrea vancouverensis Vaughan, Siderastrea adkinsi (Wells), Goniopora sp., Actinacis haueri Reuss, Actinacis parvistella Oppenheim, Actinhelia elegans (Goldfuss), Meandrophyllia oceani (de Fromentel), Dermosmiliopsis orbignyi Alloiteau, Trochoseris aperta Duncan, and Cyathoseris formosa d'Achiardi. the corals described herein were collected from mixed coral-rudist and coral-dominated assemblages in the Arroyo de la Atarjea, and one unnamed riverbed which lithologically correspond to the Arroyo de la Atarjea section, both of which belong to the upper member of the Cardenas Formation. On the genus level, 94% of the Mexican fauna corresponds to the Maastrichtian coral assemblages of Jamaica. Moreover, the Cardenas fauna shows close affinities to both Upper Cretaceous coral associations of central Europe and the Caribbean, as well as to Lower Tertiary faunas of Central America and the Caribbean. On the species level, 68.8% of the Cardenas corals are known from Lower Tertiary strata of Central America, the Caribbean, South America, Asia, European/Mediterranean region, and/or southeastern parts of the USA.

The axial rings of the thorax of seven Ordovician species of Illaenidae, and of the type species of the Silurian Cybantyx, all have the ring curved downward and forward, lacking the articulating furrow but traversed by a stout ventral ridge; the doublure similarly curves downward and forward. This type of axial ring is apparently unique among post-Cambrian trilobites. The axial ring in Scutelluidae is like that occurring in most post-Cambrian trilobites, having a convex ring, deep articulating furrow, and horizontal half ring and doublure. These and many other characters distinguish the Styginidae-Scutelluidae group from Illaenidae. Cybantyx is not an effaced scutelluid, but an illaenid. Upper Cambrian illaenid-like trilobites, which have the illaenid type of thoracic axial ring, deserve consideration as possible ancestors of post-Cambrian illaenids. The thorax is given considerable flexibility by the illaenid axial ring, enabling the body to have been flexed unusually strongly concavely dorsally, as well as to enroll. The musculature suggested omits dorsal longitudinal muscles. It is argued that many illaenids may have been vagrant benthos, particularly adapted for negotiating over irregular surfaces. The view that illaenids lived partly in a burrow is not supported by specimens preserved in such an attitude. The arrangement and varying strength of the terrace ridges on the exoskeleton of Cybantyx is consistent with their having had a sensory function; anastomosing caeca on the fixed cheek and the pleural region of the pygidium are described.

Fragmentary fossils from Late Devonian rocks, previously identified as phyllocarid arthropods, are referable to “Vermes.” Specimens identified as Dithyrocaris (=Mesothyra) sp. from the Chagrin Shale in northeastern Ohio are assigned to Sphenothallus cf. S. carbonarius (M'Coy). Thus, there are no records of rhinocaridid arthropods from the Chagrin. Fossils identified as “cercopods” of the echinocaridid, Echinocaris asiaticus Reed, from the Wetwin shales in Burma, are not arthropod remains, but are tubes produced by a gregarious worm. Echinocaris asiaticus is now represented only by a single partial carapace.

A Lower Tithonian cavity-dwelling community from pelagic carbonate platform deposits of the Czorsztyn Unit, Western Carpathians, represents a succession of mostly solitary coelobite organisms, dominated by scleractinian corals and small-sized serpulids during the initial recruitment stage, and by serpulids during the following recruitment stages. These bioconstructors were accompanied with other suspension feeders: thecideidine brachiopods, oysters, bryozoans, sponges, crinoids and sessile foraminifers. The boundary between the first and the second recruitment stage represents an interval of aggregate growth interruption, when a thin sheet of cyclostome bryozoans developed. Corals and serpulids Neovermilia and Vermiliopsis are primary bioconstructors; all other associated organisms profited from the free spaces between the serpulid tubes. The aggregates were already bioeroded, mineralized and encrusted during their growth. Serpulid larvae show a special recruitment pattern. Their tubes were observed attached on the inner surfaces of adult serpulid tubes only. Possible causes of such a larval behaviour involve several physical, biological or chemical factors. Except for the first recruitment stage, the rest of the succession seems to be physically controlled by the gradual infilling of cavities.

The early Late Carboniferous rocks of the Guandacol Formation in western Argentina preserve the glacial to postglacial transition. In the study area, this unit has been divided in three intervals: 1) a lower diamictitic interval; 2) a middle interval chiefly composed of mudstone, and 3) an upper sandstone-dominated interval. The lower interval records infill of a fjord incised into the underlying Ordovician limestone. The middle and upper intervals reflect postglacial sedimentation. Four ichnotaxa, occurring as both discrete and compound trace fossils, are documented from the lower and middle intervals of the Guandacol Formation. Diplopodichnus biformis and Cruziana diplopoda n. isp. occur in the thinly bedded stratified diamictite in the upper section of the lower interval. These deposits record sedimentation from debris flows with dropstones reflecting overprinting of ice-rafting and rain-out processes. Cruziana cf. problematica and Rusophycus carbonarius are present in very-fine to fine-grained sandstone layers interbedded with dropstone-bearing mudstone in the lower section of the middle interval. These deposits record the interplay of suspension fall-out sedimentation, ice-rafting, rain-out processes, and storm waves. The presence of linguliformean brachiopods in coeval beds nearby strongly suggests marine influence and that brackish-water conditions prevailed during the early phase of the transgression. Harsh paleoenvironmental conditions may explain the small size of the trace fossils and the low ichnodiversity in comparison to that expected in fully marine environments. The morphology of the trace fossils as bilobate ridges and furrows ornamented with scratch marks indicates that the structures were produced by arthropods, most likely trilobites and/or notostracans. Although the possibility that different ichnotaxa have resulted from changes in burrowing behaviors can not be completely disregarded, the fact that distinct Cruziana ichnospecies display non-overlapping facies distribution may suggest their production by different arthropods.

Utatsusaurus hataii, an Early Triassic ichthyosaur from Japan, is represented by exceptionally well preserved materials but is poorly known because of incomplete preparation. Further preparation of the holotype and one of the paratype specimens has revealed nearly complete forefins that are pentadactyl, with no more than five phalanges in any of the digits. The first digit is not well developed, and the fifth distal carpal appears to be absent. The phalanges along the fin margin tend to be lunate; others are flattened cylinders. These findings indicate that the relationship of Utatsusaurus with other Early Triassic ichthyosaurs must be reconsidered.

Among the equid species named from the Cypress Hills Formation (Eocene to Miocene) of Saskatchewan, Mesohippus westoni and M. propinquus are documented from the early Chadronian Calf Creek local fauna, and M. westoni is also known from the earlier Southfork local fauna and from other Chadronian and Orellan deposits of western North America. Teeth possibly referable to Miohippus assiniboiensis are found in association with Whitneyan or early Arikareean assemblages. Miohippus grandis, not M. assiniboiensis, is the correct reference for larger Chadronian equids from Calf Creek and other local faunas. Archaeohippus stenolophus (new combination) is preserved in latest Arikareean or early Hemingfordian beds of the Cypress Hills, and occurs in faunal assemblages that show strong resemblances to the Runningwater assemblage of Nebraska.

Extremely well-preserved specimens of the species Rennensismilia complanata and Aulosmilia cuneiformis occur in Santonian (Upper Cretaceous) strata of the Lower Gosau beds, near Gosau, Austria. Two of these, here reported, have aragonitic skeletal mineralogy and skeletal structures that are typical for their families, and, in addition, show distribution of trace elements (Sr and Mg above all) that confirm the biogenic origin of structures observed. R. complanata also has proteinaceous matrix preserved within its skeleton, which, seen here for the first time in electron micrographs of living or fossil corals, forms sheaths of organic matrix surrounding bundles of skeletal crystallites. Matrix is most abundant along the axial plane of septa, which also is the first-formed part of each septum. Although A. cuneiformis lacks observable organic matrix materials, its skeletal structure and its distribution and amount of trace elements are analogous to that seen in R. complanata and also in modern corals.

The Lower Cambrian Shuigoukou Formation of Xichuan, Henan province, China, yielded phosphatized instars belonging to the protolenid Ichangia ichangensis Chang, 1957, and two undetermined taxa. With relatively simple body plans, the three larval forms resemble each other to some extent, and protaspides of I. ichangensis show general similarities to those of the ellipsocephalid Palaeolenus lantenoisi Mansuy. However, their early ontogenetic processes exhibit subtle yet distinct differences. One group of unassigned protaspides possesses a sagittal glabellar furrow and protomarginal spines with branching extremities. The other unassigned protaspides bear especially long genal and protomarginal spines. The detailed preservation of these larvae reveals delicate structural variations that help provide a framework for evaluating relationships among Early Cambrian trilobites.

New Middle Cambrian fossils demonstrate unusual tagmosis within the Arthropoda. Rare specimens from the Spence Shale of northern Utah are assigned to Meristosoma paradoxum n. gen. and sp. One specimen from the Marjum Formation of west-central Utah is assigned to Meristosoma sp. These taxa are further assigned to the new family Meristosomatidae. Meristosoma, which reached 17 cm in length, is characterized by a short anterior shield, a long thorax with 36 or more articulating segments, and a posterior shield with as many as 11 fused segments. Its short anterior shield and long, multisegmented thorax have a myriapodan aspect, but Meristosoma differs from all myriapods by its posterior tagmosis. In dorsal view, its posterior shield is most like that of some macropygous trilobites, but Meristosoma differs from all trilobites by having a shorter anterior shield, ringed thoracic segments without trilobation, and no ventral doublure. Phylogenetic analysis indicates that Meristosoma is a primitive and basal arthropod. A more precise taxonomic assignment is hampered by a lack of information about its limb morphology.

Moderately well-preserved Middle Triassic radiolarians were recovered from bedded limestone exposed at about 3 km west of Kefamenanu, West Timor, Indonesia. This limestone probably from the Aitutu Formation is considered to be an allochthonous block and is embedded in the Neogene Bobonaro Complex. The radiolarian fauna in this limestone is characterized by abundant radiolarians of typical Tethyan forms and is identical to that of the early Fassanian (early Ladinian) of European Tethys and other related faunas reported from the Philippines, Russian Far East, and Japan. The Aitutu Formation is thought to be deposited in an ocean environment dominated by a warm-water current system originating from the low latitude Tethyan realm. Fifty-nine species belonging to 34 genera, including five unidentified genera, are systematically treated, among them, five new species; Parentactinia suparkai, Pseudostylosphaera timorensis, Cryptostephanidium? megaspinosum, Tetrarchiplagia compacta, and Planospinocyrtis kefaensis.

The Early Permian (Asselian) Euramerican plant Padgettia readi Mamay is reassigned to Odontopteris Brongniart, as O. readi (Mamay) Stull et al. n. comb. Distinctive elongate structures on neuropteroid pinnules of this plant, previously interpreted as fructifications, are herein reinterpreted as foliar histoid galls, structurally analogous to blister or vein galls, and probably induced by an early lineage of hemipterans or mites. These distinctive features are assigned to the new gall ichnogenus Ovofoligallites Labandeira, n. ichnogen. n. ichnosp, as O. padgetti Labandeira. The Early Permian association between an Odontopteris host and Ovofoligallites gallers probably originated during the Middle Pennsylvanian as a similar, antecedent association between Macroneuropteris scheuchzeri (Hoffmann) Cleal, Shute, and Zodrow and the maker of U-shaped surface features long known as a distinctive, unattributed damage type, but now recognizable as a likely gall. The persistence of this association between the galler and certain medullosan pteridosperms into the Permian adds to the morphological richness of the Permian galler insect fauna. The Permian ecological expansion of galling insects resulted in colonization of new host plants, primarily through a shift from the consumption of entire, mostly pteridophyte axial organs during the Pennsylvanian to the partitioning of seed plant tissues in leaves and small branches in the Permian. The Ovofoligallites galler was part of a diverse Permian galler guild involving a variety of plant taxa, organs and tissues that overwhelmingly targeted multiple lineages of seed plants.

A new species of carcineretid crab, Carcineretesplanetarius, is described from the Upper Cretaceous (lower Maastrichtian) Barton Creek Dolomite at Albion Island, Belize. The age is based on the stratigraphic range of associated nerineid gastropods and correlation with nannoplankton, benthic foraminifera, and the other known congeneric species of crab found in Jamaica. Confirmation of this age aids in constraining the timing of ejecta deposits of the Chicxulub impact found at the top of Barton Creek Dolomite exposed on Albion Island. Paleoenvironmental and paleoecological analyses suggest that these crabs were swimmers in lagoonal settings, capable of burrowing a few centimeters into the mud for protection.

The Merchantville Formation of New Jersey, Maryland, and Delaware yields a distinctive assemblage of upper lower Campanian ammonites: Pachydiscus (Pachydiscus) sp., Pseudoschloenbachia cf. P. chispaensis Adkins, 1929, Placenticeras placenta (DeKay, 1828), Texanites (Texanites) sp., Menabites (Delawarella) delawarensis (Morton, 1830c), M. (D.) vanuxemi (Morton, 1830c), Menabites (Bererella) sp., Submortoniceras punctatum Collignon, 1948, S. uddeni Young, 1963, Cryptotexanites paedomorphicus n. gen. and sp., Glyptoxoceras sp., Chesapeakella nodatum n. gen. and sp., Baculites haresi Reeside, 1927, and Scaphites (Scaphites) hippocrepis (DeKay, 1828) III of Cobban, 1969. Elements of the fauna occur in the Gulf Coast and Western Interior regions of the United States, in Western Europe, and in Madagascar and provide a basis for correlation at this level.

Vase-shaped microfossils (VSMs) occur in dolostone clasts within conglomerates, breccias, and diamictites of the Neoproterozoic Urucum Formation, Jacadigo Group, southwest Brazil. Although their taphonomic history is distinct from those of other VSM assemblages, morphometric comparison of Urucum fossils with five others described previously from North America and Europe show that two of the Urucum species—the long-necked Limeta lageniformis Morais, Fairchild, and Lahr in Morais et al., 2017 and the funnel-necked Palaeoamphora urucumense Morais et al., 2017—occur in the Kwagunt and Callison Lake assemblages, as does Pakupaku kabin Riedman, Porter, and Calver, 2017 recently described from the Togari Group, Tasmania. Obelix rootsii (Cohen, Irvine, and Strauss, 2017) new combination, previously known only from the Callison Lake Formation, is documented here from the Kwagunt Formation. In addition, Trigonocyrillium horodyskii (Bloeser, 1985) and Bonniea dacruchares Porter, Meisterfeld, and Knoll, 2003, first described from the Kwagunt assemblage, have now been found in the Urucum Formation. In light of this survey, 16 of the 18 validly described VSM species are now known to occur in the Kwagunt Formation and 13 in the Callison Lake Formation, with 12 of them shared by both formations. The fact that the Urucum VSM assemblage exhibits six of seven species in common with the Kwagunt Formation—L. lageniformis, P. urucumense, Cycliocyrillium simplex Porter, Meisterfeld, and Knoll, 2003, C. torquata Porter, Meisterfeld, and Knoll, 2003, B. dacruchares Porter, Meisterfeld, and Knoll, 2003, and T. horodyskii (Bloeser, 1985)—and all but the last of these in common with the Callison Lake Formation supports correlation of these three assemblages and indicates that the source of the fossiliferous clasts within the Urucum Formation may well have been a now-vanished late Tonian carbonate platform.

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