The early Cambrian Carinachitidae, a family in the subclass Conulata, are intriguing and important small shelly fossils. Their gently tapering, tube-shaped skeletons consist of convex faces separated from each other by broad, deep corner sulci, and they exhibit triradial, pentaradial, or predominantly tetraradial symmetry. However, the morphology of the aperture and the modes of growth of carinachitid skeletons as well as the anatomy of their soft parts are unknown. Examination of a single new, exceptionally well-preserved specimen of tetramerous Carinachites spinatus Qian, 1977, collected from the lower Cambrian Kuanchuanpu Formation in South China, reveals: (1) that its aperture is connected to a small mass of relic soft tissue and (2) that the apertural end of each of the four faces is developed into a subtriangular lappet or oral lobe that is smoothly folded toward the long axis of the tube, partially closing the tube aperture. Similarities between thorn-like spines on the faces and the oral lobes indicate that the transverse ribs were periodically displaced from the perradial portion of the aperture during formation of new ribs. In addition, the tube walls may have undergone secondary thickening during growth. The growth pattern of the tube and the spatial relationships between the tube aperture and soft parts are analogous to those of co-occurring olivooids. These findings further strengthen the previously proposed hypothesis that coeval carinachitids, olivooids, hexangulaconulariids, and Paleozoic conulariids are closely related taxa within the subphylum Medusozoa. Finally, carinachitids most likely represent an evolutionary intermediate between olivooids and hexangulaconulariids.

Scalidophoran worms diversified in the Cambrian Fortunian, as indicated by recent reports from this stage, with two described species and two more unnamed forms exclusively from Orsten-type Lagerstätten yielding three-dimensionally phosphatized fossils. Here, we report new material of scalidophoran worms in Orsten-type preservation from the Cambrian Fortunian Xinli section in northern Sichuan Province, South China. At least five forms of scalidophoran worms were recovered from this location, including Eokinorhynchus rarus Zhang et al., 2015 and four unnamed taxa—Forms A, B, C, and D. Co-occurring disassociated spinose small shelly fossils might also be isolated cuticular elements of these early scalidophoran worms. The ontogeny of Eokinorhynchus rarus is revised. Forms A, C, and D are assigned to total-group Scalidophora to indicate their uncertain positions within Scalidophora, while Form B might be a close relative of Eokinorhynchus rarus. The current work highlights the significance of Orsten-type Lagerstätten in uncovering the morphology, ontogeny, and taxonomy of early Scalidophora and Cycloneuralia, made particularly available by the new finds in China.

The plesiosaur specimen NHMUK 36184 from the Lower Jurassic of Whitby, Yorkshire and kept in the Natural History Museum of London, comprises an almost entire skeleton with nearly complete skull. It was described as one of two syntypes of Plesiosaurus homalospondylus by Owen, and selected as the lectotype by Lydekker. Extensive preparation of the skull has revealed it as one of the most complete and best-preserved Jurassic plesiosaurian skulls known, and its description adds much-needed data to our knowledge of the cranial osteology of the Plesiosauria. The three-dimensional preservation permits a relatively reliable reconstruction of its form. Microcleidus homalospondylus displays an interesting combination of cranial characters present in Jurassic plesiosauroids and Cretaceous Elasmosauridea. Its snout presents a very distinctive sculpture; the first pair of premaxillae teeth are extremely reduced; the frontal is partially overlain by the premaxillae, contacts the pineal foramen but does not contact the temporal fenestra; the jugal does not contact the orbit nor the temporal fenestra; the squamosal contacts the postorbital but not the maxilla and presents a bulb; the postfrontal contacts the posterolateral orbit margin; the anterior interpterygoid vacuity is absent; the pterygoids meet posterior to the posterior interpterygoid vacuities and are pierced by a foramen at this level; the quadrate ramus of the pterygoid presents a ventromedial flange; the parasphenoid is crested; the epipterygoid contacts the parietal; the paroccipital process is spatulate distally; the prootic presents an anteroventral process; the mandibular symphysis is keeled and bears four pairs of teeth. Microcleidus appears very similar to Hydrorion and Occitanosaurus, and the three taxa share a great number of plesiomorphic characters with basal plesiosaurians and pliosauroids.

The Mesoproterozoic is an important era for the development of eukaryotic organisms in oceans. The earliest unambiguous eukaryotic microfossils are reported in late Paleoproterozoic shales from China and Australia. During the Mesoproterozoic, eukaryotes diversified in taxonomy, metabolism, and ecology, with the advent of eukaryotic photosynthesis, osmotrophy, multicellularity, and predation. Despite these biological innovations, their fossil record is scarce before the late Mesoproterozoic. Here, we document an assemblage of organic-walled microfossils from the 1590–1270 Ma Dismal Lakes Group in Canada. The assemblage comprises 25 taxa, including 11 morphospecies identified as eukaryotes, a relatively high diversity for this period. We also report one new species, Dictyosphaera smaugi new species, and one unnamed taxon. The diversity of eukaryotic forms in this succession is comparable to slightly older assemblages from China and is higher than worldwide contemporaneous assemblages and supports the hypothesis of an earlier diversification of eukaryotes in the Mesoproterozoic.

Medusaceratops lokii Ryan, Russell, and Hartman, 2010 is an enigmatic taxon of ceratopsid represented by partial parietals from the Mansfield bonebed in the Campanian Judith River Formation, Montana. Originally, all ceratopsid material collected from this bonebed was referred to the centrosaurine ceratopsid Albertaceratops, but subsequently two parietals were designated the types of the chasmosaurine, M. lokii, in part, because they were interpreted to have three epiparietals bilaterally. Here we describe new material from the bonebed that allows a systematic revision of the taxon. A revised reconstruction of the frill, informed by newly discovered parietals, reveals that M. lokii had a broad midline ramus and at least five epiparietals (ep) around the margin of the frill, both traits that are characteristic of Centrosaurinae. From medial to lateral, the epiparietal ornamentation consists of a small, variably procurving epiparietal (ep 1), an anterolaterally curving pachyostotic hook (ep 2), a smaller pachyostoic process (ep 3), and two small triangular epiparietals (ep 4 and 5). A phylogenetic analysis of ceratopsids, which is the first to include Medusaceratops, indicates that M. lokii is a unique, early centrosaurine ceratopsid taxon that is more closely related to Centrosaurini and Pachyrhinosaurini than Nasutoceratopsini. No unequivocal chasmosaurine bones or diagnostic material from any other ceratopsid could be identified from the Mansfield bonebed, suggesting that it represents one of the oldest occurrences of a monodominant accumulation of a centrosaurine ceratopsid on record.

South China has become the most important area to establish a global stratigraphic framework of the Wuchiapingian Stage because complete Wuchiapingian sequences include the GSSPs for the base and top of the stage. As the markers of the Wuchiapingian GSSP, conodonts are the most important fossil group to establish the Wuchiapingian biostratigraphic framework. However, few documents have investigated in detail the conodont biostratigraphic succession through the entire Wuchiapingian Stage. Furthermore, the conodont taxonomy of several Wuchiapingian Clarkina species is still debated. Therefore, we here review all Wuchiapingian Clarkina species from South China and figure ontogenetic growth series from juvenile to adult individuals for each valid and important species in order to revise both Wuchiapingian conodont taxonomy and the biostratigraphic succession. Based on the Penglaitan, Dukou, and Nanjiang sections, seven conodont zones (Clarkina postbitteri postbitteri, C. dukouensis, C. asymmetrica, C. leveni, C. guangyuanensis, C. transcaucasica, and C. orientalis) are recognized. The Wuchiapingian Clarkina species lineage is also reviewed to confirm the conodont biostratigraphic framework. The Guadalupian-Lopingian boundary (GLB) interval represents a sequence boundary. The time framework of the pre-Lopingian extinction interval indicates that the beginning of the end-Guadalupian regression is in the upper part of the Jinogondolella postserrata Zone, and the beginning of the early Lopingian transgression is in the lower part of the Clarkina dukouensis Zone in South China.

Examination of ontogenetic changes in the septal angle of Late Cretaceous ammonoids (ten species representing seven superfamilies and four suborders) reveals four patterns: 1) a single abrupt change in septal angle; 2) two abrupt changes in septal angle; 3) cyclic fluctuations in septal angle throughout ontogeny; and 4) an almost constant septal angle throughout ontogeny. These various septal-angle patterns in Late Cretaceous ammonoids are in contrast with modern and fossil nautiloids, which have the common pattern displaying a single abrupt change in septal angles. Although the abrupt change of septal angles in nautiloids corresponds with the hatching event from the egg, change of septal angles in the examined ammonoids is hypothesized to correspond not to hatching but to the change from a planktic to a nektobenthic habit demarcated by the post-embryonic stage. Therefore, the variable patterns of septal angles within ammonoids suggest a diverse set of early life histories.

Gastropods are abundant in the Middle Ordovician (Whiterockian) Antelope Valley Formation of Nevada. Because Whiterockian rocks are absent in much of central and eastern North America, these Nevada gastropods play a significant role in understanding the Early to Middle Ordovician transition of the class. The shell and operculum of a new genus and species of macluritoid, Monitorella auricula, is described. New euomphaloid taxa include Walcottoma frydai n. gen. and sp., Rossospira harrisae n. gen. and sp., Barnesella measuresae n. sp., Helicotoma gubanovi n. sp., Lytospira yochelsoni n. sp., and Malayaspira hintzei n. sp.

The recovery of fully sclerotized specimens of the retiolitid Agastograptus robustus Obut and Zaslavskaya permits the recognition of the relationship between the sicula and thecae 11 and 12 for the first time, and demonstrates unequivocally that the ancora sleeve (the “clathria” of earlier literature) is not homologous with the outer wall of normal diplograptaceans, but is a structure unique to Silurian retiolitids. The study supports earlier proposals that Silurian retiolitids arose, cladogenetically, from Pattern I, ancorate diplograptaceans by distal extension of the ancora/corona, to form the ancora sleeve, but further suggests that the sclerotization of the original diplograptacean outer wall (corresponding to the inner wall of the retiolitid of this study) was suppressed.

The hyolithid species Hyolithes crebescens Resser and Endo, Hyolithes cybele Walcott, and Hyolithes delphus Resser and Endo from the Middle Cambrian of China are assigned respectively to the genera Nevadotheca Malinky, Novakotheca n. gen., family Hyolithidae, and Crestjahitus Syssoiev, family uncertain, all in the order Hyolithida. Recognition of Nevadotheca extends its geographic range from North America to China, and the occurrence of Crestjahitus in the Middle Cambrian of China increases its geographic and stratigraphic distribution from the Early Cambrian of the Soviet Union.

Poor preservation of the type specimens of Hyolithes? aliger Resser and Endo, H.? aplatus Resser and Endo, H.? cariniferus Resser and Endo, H.? daphnis Walcott, H.? delia Walcott, H.? endoi Howell (as H. ornatus Resser and Endo), H.? mantouensis Resser and Endo, and H.? tenuis Resser and Endo renders their generic identification uncertain. Hyolithes (Orthotheca) glabrus Resser and Endo is here transferred to the hyolith order Orthothecida Marek and referred with question to Decoritheca Syssoiev, family Novitatidae.

Morphology of the types of “Hyolithes” fuchouensis Resser and Endo, “H.” kuantungensis Resser and Endo, “H.” sondai Resser and Endo, “Orthotheca” daulis Walcott, and “O.” doris Walcott does not support assignment to the Hyolitha for these species; their phylogenetic affinity is uncertain.

The nomenclatorial history of the ichnogenera Lockeia and Pelecypodichnus has been confused by duality during the past 20 years. Many authors presume Pelecypodichnus is correct because Lockeia is a nomen oblitum. This presumption is rejected on both objective and subjective grounds. First, Lockeia is not a nomen oblitum. Two major gaps in the citational history of Lockeia exist, the first one of 35 years duration and the second of 43 years duration. Thus, no 50-year gap exists in the valid use of the name Lockeia. Second, the Committee on Zoological Nomenclature was not petitioned to declare Lockeia a nomen oblitum during the period of time that the nomen oblitum concept was in effect. Third, the name Pelecypodichnus implies a specific trace-maker for the trace—a practice we, and others, judge should be avoided. Fourth, topotype specimens and the lectotype of Lockeia are available for study. Fifth, even many of those authors who use Pelecypodichnus instead of Lockeia commonly note the existence of Lockeia as a synonymous generic name. Thus, use of Lockeia by numerous authors in the past 20 years results in no confusion or destabilization of the generic-level taxonomy. Lockeia, the senior synonym of Pelecypodichnus, has been used by numerous authors, is well understood, and therefore should be used instead of Pelecypodichnus.

The Upper Devonian (Frasnian) conodont fauna of the Lime Creek Formation of north-central Iowa is dominated by species of Polygnathus. Patterns of species composition and abundance are consistent with the Polygnathus biofacies described from the Frasnian of the Northwest Territories of western Canada. Consequently, the standard Frasnian conodont zones, defined on sequences developed in the Palmatolepis biofacies, are not applicable to the Lime Creek sequence. The Lime Creek conodont sequence correlates with Zones 4, 5 and Faunal Interval 7 of the Frasnian conodont sequence in the Alberta Rockies and with similar sequences in the southwestern United States. The Pb elements of Palmatolepis semichatovae Ovnatanova and Ancyrognathus? deformis (Anderson) are described and illustrated for the first time.

In the Lime Creek Formation of north-central Iowa, brachiopods of the lowermost part of the Nervostrophia thomasi Zone of Day (1989a) occur in Zone 4, brachiopods of most of the N. thomasi, Douvillina arcuata, and Cyrtospirifer whitneyi Zones span conodont Zone 5, and the Elita inconsueta and Iowatrypa owenensis Zones occur in Faunal Interval 7. Species of the ammonoid Manticoceras and of the gastropods Floyda, Turbonopsis, and Westerna are restricted to Faunal Interval 7. Species of the calcareous foraminifer Nanicella first occur in Zone 5, and are joined by species of Multiseptida high in Zone 5.

Two leaves of Quercus simulata Knowlton from the Miocene of Oregon each show a new type of cynipid gall. Antronoides cyanomontanus n. sp. is described from six elongate and narrowly spindle-shaped galls, 7.0 mm long, and 2.0 mm wide tapering to a narrow tip. They have expanded rim-like bases with most galls scattered throughout the midsection adjacent to or partially straddling a secondary vein. Antronoides oregonensis n. sp. is known from 20 galls, 4.0-5.0 mm long, 1.8-2.0 mm wide and weakly clavate, appearing C-shaped with a rounded apex and circular to oval-shaped base. Galls occur primarily in the basal third of the leaf in a single file along each side of the midrib. Contrary to previous studies, we found A. schorni Waggoner and Poteet, A. polygonalis Waggoner, and A. cyanomontanus to be morphologically closer to Cynips cornifex Hartig on Q. pubescens (European white oak), whereas the new gall A. oregonensis most closely resembles X. clavuloides. The presence of Antronoides indicates the evolution and dispersal of Cynipini wasps was well underway in western North America by the Miocene. However, the new galls leave open the possibility that X. clavuloides and related species may have evolved during the Paleogene in higher-latitude mesic forests of western North America, rather than in the southern Great Basin as suggested by Kinsey and Waggoner and Poteet.

A newly discovered assemblage of archaeocyathans, dominated by the unusual genus Retilamina, occurs in outcrops of the upper Harkless Formation in Esmeralda County, Nevada. These rock units have been correlated with the Saline Valley Formation in the Bonnia–Olenellus Zone (late Early Cambrian) of eastern California, making this the youngest known occurrence of archaeocyathans in the White–Inyo region.

Although the assemblage contains a variety of different organisms (including the alga Renalcis, trilobite and echinoderm debris, bivalves?, and Chancelloria spines), it is dominated by archaeocyathans. Diplocyathellus, a conical form with a complex inner wall, is the only genus of regular archaeocyathan in the assemblage. The irregular archaeocyathans Arrythmocricus and Metaldetes exhibit dendroid branching and cylindroconical morphologies, respectively. A third irregular, Retilamina debrennei n. sp., is an atypical archaeocyathan with a sheetlike or shallow convex dome morphology. Retilamina formed natural cavities that sheltered cryptobionts. Unlike coelobiont communities reported from other Lower Cambrian cavities where the diversity of the supported biota is relatively high, the Harkless cavities contain only the alga Renalcis. While the undersurfaces of Retilamina are consistently encrusted by Renalcis, the upper, exposed surfaces typically lack epibionts. Similar morphologies and associations for Retilamina have been reported from bioherms and biostromes from southern Labrador and western Newfoundland. Unlike most archaeocyathans, Retilamina had a solitary, free-lying life habit. Retilamina's broad base and low profile provided stability in episodically turbulent conditions or on biologically disturbed substrates.

This occurrence demonstrates that the disappearance of archaeocyathans from the stratigraphic record of the southern Great Basin in the late Early Cambrian is a paleoecological artifact. Archaeocyathans were extant in the region in the late Early Cambrian but the habitats conducive to archaeocyathan growth or preservation are, for the most part, not represented in the preserved strata.

Two new species of dinoflagellate are described from the upper Cenozoic of the North Atlantic region. They are assigned to the goniodomacean genus Capisocysta Warny and Wrenn, 1997 emend., whose archeopyle uniquely forms by the extensive and exclusive dissociation of hypocystal plates. Capisocysta lata new species is recorded from the upper lower Pliocene Coralline Crag Formation of eastern England, the lower and upper Pliocene of the subsurface Great Bahama Bank, and as a living cyst from Phosphorescence Bay, Puerto Rico. Capisocysta lyellii new species is reported from the Coralline Crag Formation of eastern England. Capisocysta provides the only unambiguous example of a hypocystal archeopyle in the order Gonyaulacales and the only example of a hypotractal archeopyle in the division Dinoflagellata.

The spherical, proximate cysts have pre-formed lines of weakness that occur exclusively on the hypocyst, where they follow plate boundaries. Upon excystment, these sutures facilitate the separate release of plates 2–6″′, ps, 1p, and 1″″. Sulcal plates 1s and rs and postcingular plate 1″′ typically remain attached to the epicyst, forming a distinctive hyposulcal tab. The single antapical plate in C. lata is represented in C. lyellii by two plates (left and right first antapical homologues) that are released separately.

Capisocysta has a tropical to warm temperate distribution today. It thrived and perhaps formed blooms in tropical carbonate platform environments of the Bahamas during the Pliocene, and might prove to be a useful indicator of very warm intervals within the Pliocene of higher latitude regions including the southern North Sea basin.

To facilitate discussion of Capisocysta, several morphological terms have been modified or newly introduced. These terms more precisely describe archeopyle position and extent in dinoflagellates.

The central muscle scar field of the beyrichioidean palaeocopid ostracodes includes an adductor muscle scar composed of many polygonal scars, a long mandibular scar composed of eight individual scars, and an oval frontal muscle scar. Probably, as in the extant ostracodes, the muscle scars served as attachment points for the closing muscles as well as for the muscles and chitinous supporting structures from the appendages. the fulcral depression, on which the dorsal apex of the mandible pivots in recent ostracodes, has also been recognized in the Early Carboniferous beyrichiids and paraparchitids.

The pore systems of the beyrichioideans are more advanced than assumed so far, and they include, documented for the first time, the secretory (‘exocrine’) pores and ‘marginal’ pores in Paleozoic beyrichioideans. It seems likely that the development of these pores, was related to the transition of beyrichioideans from shallow marine into unstable, possibly brackish, water paleoenvironments.

The partially calcified inner lamella and the ‘marginal’ pore canals are apomorphies of some Early Carboniferous beyrichioideans. Internal features of the paraparchitids confirm their beyrichioidean affinity. the adductor and mandibular scars are plesiomorphic in the Beyrichiidae and Paraparchitidae. the presence of mandibular scars and fulcral depressions may indicate that these ostracodes were actively feeding bottom crawlers.

New cranial and postcranial material of the baenid turtle Neurankylus from the Paleocene Nacimiento Formation (Torrejonian NALMA) of northwestern New Mexico represents a new species, Neurankylus torrejonensis. The material consists of a fragmented but mostly complete skull, a partial carapace and plastron, portions of both humeri, a partial pelvis, a complete right femur, and a distal phalanx. The small, undivided cervical scale, wide vertebrals, complete ring of marginals, and large size (carapace length 520 mm) diagnose the new taxon as belonging to Neurankylus. The narrow fifth vertebral scale and scalloped posterior shell margin reveal affinities with Neurankylus baueri Gilmore, 1916, which is known from Campanian sediments in New Mexico and Utah. The holotype of Neurankylus torrejonensis is the youngest known specimen of the Neurankylus lineage, which is known to reach at least back to the Late Cretaceous (Santonian). A nearly complete species-level analysis of baenids confirms the basal placement of Neurankylus outside of Baenodda and the split of Baenodda into two primary subclades, herein named Palatobaeninae and Eubaeninae.

The Germig Formation of the Tethyan Himalaya of southern Tibet contains an exceptionally abundant bivalve fauna which has been found in association with choristoceratid and psiloceratid ammonoids and spans the Triassic/Jurassic boundary. The bivalve fauna consists of 25 species, including four new species: Newaagia lanonglaensis, Persia hallami, Liostrea tibetica, and Ctenostreon newelli. The fauna comprises three biostratigraphically controlled bivalve assemblages: 1) an upper Rhaetian Palaeocardita–Krumbeckiella Assemblage including seven species; 2) a high diversity transitional Rhaetian-Hettangian Persia–Plagiostoma Assemblage with many as 19 species; and 3) a low diversity lower Hettangian Liostrea–Chlamys Assemblage containing three species. The transitional Rhaetian-Hettangian Assemblage is dominated by cementing species and exhibits a high degree of endemism. A large proportion of lower latitude and cementing taxa from the lower two levels may indicate that they inhabited shallow subtidal tropic or subtropic paleoenvironments.

A new morphological type of Paleozoic calcareous alga is represented by Calcipatera cottonwoodensis n. gen. and sp., a codiacean species found in the Cottonwood Limestone Member, Lower Permian, of eastern Kansas. The new species, as reconstructed from serial sections of weathered out, in situ, intact specimens, had a broadly obconical, cup-like membranous thallus. The internal structure of the membrane as seen in cross section consisted of a medulla with mosaic sparry calcite and bilateral cortices with calcite packets forming utricular molds similar to those of other known membranous algae. The sparry calcite apparently replaced the lightly calcified or uncalcified intercoenocytic spaces in the medulla and the calcite crystals replaced the interutricular aragonite. The organism had previously been identified as Anchicodium Johnson.

Sigournea multidentata n. gen. and sp., an early tetrapod, is described from the Late Mississippian Delta locality of southern Iowa, USA. The holotype and only known specimen, a right mandible, is unique in the structure of the symphysial region, and in addition has a unique combination of characters that are shared with other tetrapods. The free ventral border of the single exomeckelian fenestra is formed by infradentary bones. Its visible portion shows several arch bases, separated by notched or straight intervals. This morphology is interpreted as indicating that the arch bases and intervals between them reflected a series of Meckelian fenestrae that were partly exo- and partly endoskeletal, due to the fact that the exoskeletal arch bases continued dorsally in Meckelian cartilage. We suggest that this may exemplify a stage in the evolution of exomeckelian fenestrae, in at least some lineages of early tetrapods. The relations of Sigournea are indeterminate. That it is a tetrapod is indicated by the presence of pit and ridge ornamentation, an open lateral line sulcus, a dorsally directed glenoid, a single elongate exomeckelian fenestra, absence of intercoronoid fossae, absence of coronoid fangs, a single row of marginal teeth on the dentary, and an absence of dentition on the prearticular. It is at present impossible to determine its relationship with other early tetrapods, and we conclude that Sigournea is best considered as an early tetrapod incertae sedis.