The late Miocene Gatun Formation of northern Panama contains a highly diverse and well sampled fossil marine assemblage that occupied a shallow-water embayment close to a purported connection between the Pacific and Atlantic (Caribbean) oceans. However, the diverse chondrichthyan fauna has been poorly documented. Based on recent field discoveries and further analysis of existing collections, the chondrichthyan fauna from this unit comprises at least 26 taxa, of which four species are extinct today. The remaining portion of the total chondrichthyan biodiversity has affinities with modern taxa and is therefore comprised of long-lived species. Based on known records of the modern geographic distribution range of the Gatun chondrichthyans, the fauna has mixed biogeographic affinities suggesting that around 10 million yr ago, a connection likely occurred between the Pacific Ocean and the Caribbean Sea. Given the known habitat preferences for modern chondrichthyans, the Gatun fauna was primarily adapted to shallow waters within the neritic zone. Finally, comparisons of Gatun dental measurements with other faunas suggest that many of the taxa have an abundance of small individuals, in agreement with previous studies that proposed this area as a paleonursery habitat for the species Carcharocles megalodon.

The Asterozoa as traditionally recognized is monophyletic, although ancestry within the Echinodermata is unknown. The asterozoan class Somasteroidea is most readily recognized by presence of series of simple ossicles termed virgals that extend laterally from each ambulacral ossicle. Virgal series reduction to two or three together with ossicular specializations provide apomorphies of the class Stenuroidea (new ranking). Both asteroid-like and ophiuroid-like configurations as well as expressions less suggestive of those of the surviving classes emerged within stenuroids during an early period of diversification. The classes Ophiuroidea and Asteroidea are separate lineages marked by virgal series reduction to a single ossicle and other ambulacral column specializations. It is uncertain whether one or both surviving classes were derived directly from somasteroids or originated through stenuroids. All three of the derived asterozoan classes can be argued to be either monophyletic and thereby justifying class status, or alternatively either paraphyletic or polyphyletic and thereby indicative of multiple plesions; here, monophyletic class-level status is favored for all three.

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 first definitive fossil species of the rove beetle (Staphylinidae) subfamily Phloeocharinae is described and figured from a single individual preserved in Late Cretaceous (Turonian) amber from New Jersey. The species is representative of the extant genus Phloeocharis Mannerheim and is described as Phloeocharis agerata Chatzimanolis, Newton, and Engel, new species. The specimen was imaged using traditional light microscopy as well as synchrotron propagation phase contrast microtomography, permitting a detailed examination of otherwise difficult to observe features. Examination revealed remarkable homogeneity across many characters with those of extant relatives, highlighting considerable morphological stasis in the genus over the last 90 million years.

The genus Helicoprion (Chondricthyes, Euchondrocephali) is preserved primarily by a continuous spiral root that forms the base for more than 130 teeth. Helicoprion is found globally in Lower Permian marine rocks and at least 100 specimens exist in public collections worldwide. Ten species of the genus are reviewed in the context of new morphometric analyses conducted on dozens of specimens. Helicoprion whorls share a common inner spiral geometry that results in exponential growth of tooth and root dimensions. Novel growth equations permit calculation of whorl diameter, volution number and tooth count from incomplete specimens. The results of meristic and geometric analyses identify taxobases that distinguish three emended species concepts. Differentiation of form is evident among specimens only after the second volution or roughly the 85th tooth. Helicoprion davisii has widely spaced, stout teeth with tall cutting surfaces and is distinguished from H. bessonowi, which has narrow, closely spaced teeth with short cutting surfaces. Helicoprion ergassaminon is an intermediate form, having narrow, closely spaced teeth with tall cutting surfaces. Several large specimens in the study are too dissimilar to place in the new emended species concepts.

The Dunleith Formation echinoderms lived on a shallow water carbonate platform (Benthic Assemblages outer 2 and 3 during the latter part of the Dunleith Regressive Cycle). The echinoderms were buried rapidly by storms or a volcanic ash bed in one example. The presence of complete specimens, entire crowns, attachment structures, and excellent preservation strongly suggests that these assemblages reflect in situ communities on the seafloor that have not been significantly mixed, transported, or concentrated in time. Most taxa are suspension feeders, namely 21 crinoids, one glyptocystitid rhombiferan, a paracrinoid, and two edrioasteroids, but a deposit feeding pleurocystitid rhombiferan is also common. Three assemblages are recognized and defined by their dominant taxa; in order of increasing depth, these are the Cotylacrinna sandra, Pleurocystites strimplei, and Cupulocrinus crossmani assemblages. Substrates ranged from hard- or firm-ground carbonates to soft carbonate and siliciclastic muds. Diverse attachment structures are recognized: the recumbent stems of calceocrinids, lichenocrinids on shells, small distal stem tips, and round to lobate calcite pads cemented to shells or the substrate, open distal stem coils directly on the seabed or coiled around soft objects thereon, and large conical and highly modified cirrus holdfasts on hard- or firm-grounds. The echinoderms were located at levels ranging from the seafloor to almost a meter above, with maximum diversity at about 50 mm above the seafloor. The size frequency distributions of food particles and the ranges of ambient current velocities for successful feeding by the juveniles and adults of the common crinoids are modeled using filtration theory. The food particle size distributions and the current velocities for feeding are correlated with the arm or filtration fan morphology of the crinoids. Differences between these parameters tend to partially separate the feeding ecologies of species located at the same elevation. Nevertheless, considerable overlap remains between species for small sized food particles and the lower ranges of ambient current velocities for feeding. Except for the Cotylacrinna sandra Assemblage, competition for space does not seem to have been important in regulating the ecological structure of the Dunleith crinoids. However, the deposit feeding pleurocystitids possibly competed for food and space in one example. The Dunleith assemblages are much more diverse with greater ecological complexity than seen in the relatively deep water fauna from the Upper Ordovician Trenton Group of the Walcott-Rust Quarry in New York (Benthic Assemblage 5).

Rhynchonellida is the stratigraphically oldest and phylogenetically most basal of the extant rhynchonelliform brachiopod orders, yet phylogenetic relationships among rhynchonellides are poorly known. The fourteen named rhynchonellide superfamilies (four of which have extant representatives) were defined primarily on the basis of features of the dorsal cardinalia, particularly crural morphology, but their homology and polarity have not been investigated rigorously. Superfamily monophyly is unclear, as is the evolution of several distinctive rhynchonellide morphological features, such as crura.

The purpose of this study is to investigate the phylogenetic relationships among extant rhynchonellide genera using skeletal characters, and to compare the results with the current classification, elucidating the evolution of morphological features in the process. We completed parsimony-based and Bayesian analyses using fifty-eight characters of the interior and exterior of the shell that vary among the nineteen extant genera. Our results are readily interpretable with respect to the classification, and indicate that Hemithiridoidea, Dimerelloidea, and (in some analyses) Pugnacoidea appear to be monophyletic. Species classified in Dimerelloidea and Pugnacoidea, and in certain cases Hemithiridoidea, each form derived subclades that evolve from within a paraphyletic Norelloidea at the base of each subclade. Raduliform crura appear to be the most basal, phylogenetically; five other crural morphologies evolve from the raduliform state. However, morphological characters currently uniting genera in rhynchonellide superfamilies are not clearly diagnostic and exhibit a relatively high degree of homoplasy overall, suggesting that consistency with the classification may be based on a false sense of confidence in rhynchonellide morphology to clearly elucidate evolutionary relationships. Published molecular phylogenetic hypotheses conflict with the morphological topologies, further supporting this possibility.

The evolutionary trends among diagnostic characters of Recent rhynchonellides appear to reflect successive juvenilization in adult morphology in several subclades, suggesting that heterochrony may have played an important role in the evolution of the group.

A comprehensive, high resolution stratigraphic database of fusulinoidean foraminifers reveals that this group of protists suffered extreme losses during the Guadalupian extinction. Most species (88%) were eliminated gradually over the course of 9 myr during the Wordian and Capitanian ages. A pulse of greatly elevated per capita extinction frequency occurred during the last million years of the Capitanian (260–259 Ma). Contrary to prevailing opinion, the end-Capitanian event did not preferentially eliminate large, morphologically complex species in the families Schwagerinidae and Neoschwagerinidae, because most species in those families were already extinct. Rather, 69 percent of the species eliminated at the end of the Capitanian were small, morphologically conservative representatives of the Ozawainellidae, Schubertellidae and Staffellidae. Survivors from these families comprised the low-diversity association of Wuchiapingian fusulinoideans. Schubertellids, and to a lesser extent ozawainellids, diversified in the late Wuchiapingian and Changhsingian ages before the final demise of fusulinoideans during the end-Permian mass extinction. The Wordian–Capitanian fusulinoidean attrition might have been caused by photosymbiont loss and habitat reduction stemming from an interval of global cooling termed the Kamura event (∼265–259.5 Ma), although the onset of fusulinoidean diversity decline predates geochemical evidence for the beginning of the Kamura event by ∼3 myr. The end-Capitanian extinction pulse might reflect environmental deterioration from the combined effects of global cooling, Emeishan effusive volcanism and sea-level lowstand.

Six species of conulariids, assigned to four genera, were recovered from the type locality of the Cat Head Member of the Red River Formation in southern Manitoba, Canada. These are middle Katian (Late Ordovician) in age. The most abundant conulariid species from this locality, Conularia porcella, is new, and is represented by 21 specimens. Additionally, 28 three-dimensionally preserved micromorphic conulariids, assigned to Eoconularia aff. loculata, were recovered using acetic acid preparation from limestone samples of late Katian (Late Ordovician) age. These samples had been collected from Churchill, northern Manitoba, by the Geological Survey of Canada's J. B. Tyrrell in 1894. These taxa are unusually abundant for conulariids, which are normally represented by only a few specimens from any given locality, and this abundance may be a reflection of the exceptional preservation at these two localities.

Pywackia baileyi Landing in Landing et al., 2010, from the upper Cambrian Yudachica Member of Oaxaca State, southern Mexico, consists of small, phosphatic, proximally tapering cylindrical rods covered by shallow polygonal calices. The bryozoan-like morphology of this fossil prompted its interpretation as the first bryozoan known from the Cambrian. However, restudy of some of the original material, employing scanning electron microscopy for the first time, questions the assignment of Pywackia to the Bryozoa. Striking similarities between Pywackia and the modern pennatulacean octocoral Lituaria lead to an alternative hypothesis interpreting Pywackia an early fossil octocoral. While Pywackia is probably not a true pennatulacean, a group with a definitive fossil record stretching back only to the Late Cretaceous, it can be envisaged as having had a similar skeletal structure and ecology to Lituaria, the rods representing mineralized axes of tiny colonies that lived with their proximal ends buried in the sediment and distal ends covered by feeding polyps. Landing et al. (2010) considered the phosphatic composition of Pywackia specimens to be the result of diagenetic replacement, but the evidence is equivocal. If Pywackia had a primary phosphatic skeleton, this would support the hypothesized existence of phosphatic biomineralization early in the evolutionary history of Cnidaria, as well as providing further evidence that Pywackia is not a bryozoan.

We report the oldest fossil occurrence of freshwater potamolepid sponges (Demospongiae, Spongillina, Potamolepidae) to date, originating from middle Eocene lake sediments accumulated in the Giraffe kimberlite maar, northern Canada. Sponges are represented by strongyle spicules that are gemmuloscleres. These are described herein as belonging to a new species, Potamophloios canadensis. Because the most similar extant potamolepid sponges inhabit subtropical to tropical water bodies, these observations provide further evidence of biogeographic reorganizations in response to warm high-latitude Eocene paleoclimates.

Gap-coding permits the use of continuous metric characters in cladistic analyses. Character means are converted to integer equivalents by placing character state divisions in the locations of phenetic breaks between specimen clusters, under the assumption that these breaks represent the locations of bottlenecks in character distributions. Similarities and differences between specimens from closely related species of cystoporate bryozoans were evaluated for the first time by converting continuous morphometric measurements into gap-coded binary and multistate characters and analyzing them cladistically, rather than just phenetically, across multiple species of Strotopora, Cliotrypa ramosa and Fistulipora compressa.

Our results demonstrate that cladistic analysis of gap-coded morphological characters can be effective in resolving phylogenetic relationships at low taxonomic levels (within and among genera) while objectively highlighting both the morphological features that specimens (taxa) share and those characteristics that differentiate them. Differences in cystiphragm abundances and sizes, especially in the proximal portions of colonies, discriminate between species of Strotopora. Colony size and growth form, abundances and lengths of hemiphragms, and sizes of cystopores discriminate between Strotopora and the closely related genus Cliotrypa. Cladistic patterns indicate that Strotopora foveolata Ulrich is a valid species with Strotopora dermata as its junior subjective synonym. Fistulipora compressa is reassigned to the genus Strotopora whereas a decision on the taxonomic status of Cliotrypa ramosa requires a broader cladistic analysis of fistuliporine genera.

Two amphibian taxa are reported for the first time from the lower to middle Miocene shallow-marine Calvert Formation. These are Batrachosauroides aff. B. dissimulans (a large proteoid salamander) and cf. Notophthalmus robustus (a small newt). Four kinds of identifiable nonmarine turtles were reported previously from this formation. These are Bairdemys miocenica (a pleurodire), Kinosternon sp. (a musk turtle), Hesperotestudo ducateli and Hesperotestudo wilsoni (tortoises). Four additional taxa reported here are Chrysemys isoni n. sp. (a painted turtle), Trachemys sp. (a pond turtle), Floridemys hurdi n. sp. (a small tortoise), and Apalone lima (a softshell turtle). Most of these taxa are known from elsewhere in the Atlantic and Gulf Coastal Plains from New Jersey to Texas. The regional widespread occurrence of many of these taxa indicates that they represent a modestly diverse community of amphibians, fresh water turtles, and land turtles that were endemic to the Atlantic and Gulf coastal regions of the United States during the late early and early middle Miocene. Their pattern of distribution is similar to that of eastern American land mammals during this time interval, indicating that the Atlantic and Gulf coastal plains of the southeastern United States then lay within a single climatic zone that constituted a distinctive and long-lived faunal province throughout the early and middle Miocene (Hemingfordian through Barstovian land mammal ages).

The Sesong Formation is a member of the Taebaek Group, Korea, which extends from late Cambrian Series 3 to middle Furongian in age. Recent studies on the trilobites of the Sesong Formation have contributed significantly to the revision of the biostratigraphy. However, trilobites in the lower part of the formation, which may include the “Stephanocare Zone”, have remained essentially overlooked since the establishment of the biozone, making it difficult to correlate with the equivalent biozones of North China. Here we report trilobite faunas from the lower part of the Sesong Formation in two different sections, the Seokgaejae and the Jikdong sections, which yield two species of Jiulongshania among other species. Species of Jiulongshania have been known to occur successively in North China, so are useful for detailed correlation. Specimens of Stephanocare richthofeni are fragmentary and rarely occur in association with Jiulongshania regularis, while Jiulongshania species occur throughout the studied intervals. Accordingly, it is reasonable to extend the previously established Jiulongshania Zone of the uppermost part of the underlying Daegi Formation into the lower part of the Sesong Formation. By doing so, the Jiulongshania Zone is correlated with the Blackwelderia Zone of North China with confidence. The lowermost part of the Sesong Formation in the Jikdong section yields a fauna including J. regularis, which implies that the boundary between the Daegi and Sesong formations is diachronous within the Taebaeksan Basin. The Daegi/Sesong formation boundary in Korea is comparable to the Zhangxia/Gushan boundary in North China in that it displays an abrupt change from a carbonate-dominant facies to a shale-dominant facies. The correlation employing the Jiulongshania species indicates that the facies shift occurred significantly earlier in Shandong, North China than in the Taebaeksan Basin, Korea.

A fusulinoidean taxonomic study of the Gurkovo and Kalinovo sections allows us to refine the biostratigraphy of the poorly studied Myachkovian (upper Moscovian) strata of the “N” Formation in the Donets Basin. Three fusulinid biozones, Hemifusulina graciosa–Fusiella spatiosa, Fusulina cylindrica–Fusulinella pseudobocki, and Fusulinella ? kumpani, are proposed in the interval from the top of Limestone M10 to the base of N3, and they are correlated with coeval strata in the historical type area of the Moscow Basin. A total of 33 fusulinid species and subspecies belonging to eight genera are described, including three new species: Hemifusulina gurkovensis n. sp., Beedeina innaeformis n. sp., and Fusulina sosninae n. sp. The main evolutionary trend in fusulinoidean morphology in the late Moscovian is the appearance of massive secondary deposits in the limestone of the “N” Formation.

Specific temporal and distributional patterns of the Middle Pennsylvanian fusulinoidean assemblages indicate variations in sea level stand. Variations are cyclic, with periods ∼600,000–1,000,000 years. A Hemifusulina-association indicates the beginning of transgression; the late transgression–high sea level stand is designated by the Beedeina–Neostaffella–Ozawainella–Taitzehoella assemblage which is successively replaced by the most diverse Fusulinella-dominant association, which occupied a progressively shallowing sea.

The similarity of fusulinoidean assemblages in the Moscow and Donets Basins and their cognate evolution trends reveal a connection between both regions at least during Podolskian–Myachkovian time.

To clarify the systematic positions of the important gonyaulacacean genera Operculodinium Wall, 1967 emend. Matsuoka et al., 1997 and Protoceratium Bergh, 1881, we present in detail the tabulation of the Oligocene–Pleistocene, thermophilic, cyst-defined species Operculodinium bahamense Head in Head and Westphal, 1999 emend., and the extant, cosmopolitan, theca-defined species Protoceratium reticulatum (Claparède and Lachmann, 1859) Bütschli, 1885. Both species have a sexiform hyposomal tabulation, and L-type (Protoceratium reticulatum) or modified L-type (Operculodinium bahamense) ventral organization. Protoceratium reticulatum has dextral torsion of the hypotheca, requiring assignation of the genus to the subfamily Cribroperidinioideae Fensome et al., 1993, whereas Operculodinium bahamense has neutral torsion requiring assignation to the subfamily Leptodinioideae Fensome et al., 1993. The stratigraphic range of this subfamily is now extended upwards to the lower Pleistocene. Paradoxically, Protoceratium reticulatum produces a cyst whose morphology is circumscribed by the cyst-defined genus Operculodinium, either implying polyphyletic origins for this genus or that combinations of ventral organization and torsion used to subdivide the family Gonyaulacaceae cannot always be applied rigidly. In detail, Operculodinium bahamense is shown to have an unusual ventral tabulation in which the first apical plate contacts the apical pore complex but not the sulcus. The new term “episert” is proposed to describe this plate relationship, which appears to have evolved independently in several lineages of the suborder Gonyaulacineae.

The development of the trilobite pygidium involves both an articulation process at the frontal part and the formation of new segments at the rear end, and hence the development of the meraspid pygidium entails complicated morphological changes. This study deals with the ontogeny of the Furongian (late Cambrian) ptychaspidid trilobite, Quadraticephalus elongatus (Kobayashi, 1935), from the Hwajeol Formation of the Taebaek Group, Taebaeksan Basin, Korea, with a special focus on the segmentation process during the meraspid pygidial development. Compared to the ontogeny of a ptychaspidid trilobite, Asioptychaspis subglobosa (Sun, 1924), which is assumed to be an ancestral species of Q. elongatus, the convexity of the cranidium of Q. elongatus increased in a slower rate; the yoked free cheek of Q. elongatus splits to form a ventral median suture in a later developmental stage; and, a rim-like ridge, which disappeared in the early holaspid pygidium of A. subglobosa, was maintained in the late holaspid period of Q. elongatus. These morphological changes with growth imply that paedomorphosis was involved in the evolution of Q. elongatus. Eleven stages are recognized for the meraspid pygidial development, which began with an accumulation phase during which the number of segments increased from three to seven, followed by an equilibrium phase with seven segments, and ended up with a depletion phase during which the number of segments within the pygidium decreased to four. During the depletion phase, the pygidial length did not increase or even slightly decreased. The onset of the epimorphic phase, in which the total number of trunk segments does not increase anymore, precedes the onset of the holaspid period, demonstrating that the developmental mode of Q. elongatus is protomeric.

Rangea is the type genus of the Rangeomorpha, an extinct clade near the base of the evolutionary tree of large, complex organisms which prospered during the late Neoproterozoic. It represents an iconic Ediacaran taxon, but the relatively few specimens previously known significantly hindered an accurate reconstruction. Discovery of more than 100 specimens of Rangea in two gutter casts recovered from Farm Aar in southern Namibia significantly expands this data set, and the well preserved internal and external features on these specimens permit new interpretations of Rangea morphology and lifestyle. Internal structures of Rangea consist of a hexaradial axial bulb that passes into an axial stalk extending the length of the fossil. The axial bulb is typically filled with sediment, which becomes increasingly loosely packed and porous distally, with the end of the stalk typically preserved as an empty, cylindrical cone. This length of the axial structure forms the structural foundation for six vanes arranged radially around the axis, with each vane consisting of a bilaminar sheet composed of a repetitive pattern of elements exhibiting at least three orders of self-similar branching. Rangea was probably an epibenthic frond that rested upright on the sea bottom, and all known fossil specimens were transported prior to their final burial in storm deposits.

Marrella, a well-known and important component of the Burgess Shale, was only previously found in the Burgess Shale and in the Kaili Biota. An exoskeleton attributed to Marrella is described herein from the lower part of the Balang Formation (Cambrian Series 2) in Paiwu, northwestern Hunan Province, China. It represents not only the third locality where the genus is found, but also the oldest known occurrence of this taxon.

We present here the first report based on phylogenetic analyses of small subunit (SSU/18S) and large subunit (LSU/28S) ribosomal DNA (rDNA) sequences from a wider-than-token sample of rhynchonellide articulate brachiopods, with data from 11 of ∼20 extant genera (12 species) belonging to all four extant superfamilies. Data exploration by network and saturation analyses shows that the molecular sequence data are free from major aberrations and are suitable for phylogenetic reconstruction despite the presence of large deletions in four SSU rDNA sequences. Although molecular sequence analyses cannot directly illuminate the systematics of fossils, the independent, genealogical evidence and phylogenetic inferences about extant forms that they make possible are highly relevant to paleontological systematics because they highlight the limitations of evolutionary inference from morphology. Parsimony, distance, maximum likelihood (no clock) and Bayesian (relaxed-clock) analyses all find a tree topology that disagrees strongly with the existing superfamily classification. All tested phylogenetic reconstructions agree that the taxa analyzed fall into three clades designated A1, A2, and B that reflect two major divergence events. The relaxed-clock analysis indicates that clades A and B diverged in the Paleozoic, while clades A1 and A2 reflect Permo-Triassic (and later) events. Morphological homoplasy and possible gene co-option are suggested as the main sources for the discord between the morpho-classification, the results of cladistic analyses of morphology, and the relationships reconstructed from molecular sequences. The origin, function and evolutionary implications of the deletion-bearing rhynchonellide SSU rDNA sequences are briefly discussed in relation to pseudogenes and concerted evolution in the rDNA genomic region.