Onset of maturity in trilobites is generally considered to occur when the last trunk segment is released into the thorax, marking the start of the holaspid stage. Here we describe striking morphological changes that occur within the holaspid ontogeny of Lonchopygella megaspina Zhou in Zhou et al., 1977, which include the effacement of dorsal furrows, the rapid and complete degeneration of pygidial lateral spines, and the increasing prominence of a pygidial axial spine. These notable changes, which are not coincident with the onset of the holaspid phase, emphasize that the onset of maturity in trilobites should be viewed on a character-by-character basis before assessing whether the exoskeleton as a whole can be described as mature. The holaspid pygidial condition in L. megaspina may represent an intermediate step in an evolutionary transition in the number, form, and allocation of segments in the tsinaniid trunk. Pygidial transition from a dynamically changing complement of segments in the meraspid phase to a static complement in the holaspid phase was accompanied by a marked change in the extent to which segment boundaries defined pygidial structure. Attaining this static complement allowed subsequent pygidial development to emphasize its structure as an integrated unit in which internal segmental boundaries became diffuse, a continuous margin to become prominent, and an elongated terminal spine, first evident at onset of epimorphic growth, to develop allometrically. Trilobite body development suggests that while the segmented construction placed constraints on how morphology varied, the influence of these constraints diminished following completion of thoracic segment construction. Selective premium for a distinct posterior tagma might favor the early ontogenetic acquisition of such a structure, and could have been a driver of the repeated trend toward caudalization witnessed among derived trilobite clades.

Additional specimens of the problematical rodent Pipestoneomys Donahoe, 1956, have allowed for recognition of a new family, Pipestoneomyidae. A new genus and species of pipestoneomyid is recognized from the late middle Eocene (Duchesnean North American Land Mammal Age; Bartonian), Argorheomys septendrionalis, which is morphologically more primitive than Pipestoneomys and demonstrates that this new family has been distinct since the Duchesnean. The Pipestoneomyidae share a number of derived characters with the Geomorpha, especially the two-part inner layer of incisor enamel of the Eoymidae. The Pipestoneomyidae differ from the Eomyidae in lacking the basic “omega” pattern of the cheek teeth of the former, so are in the Eomyoidea as a distinct family.

A new microconchid tentaculitoid, Microconchus utahensis new species, is described from the Lower Triassic (Spathian) Virgin Formation of two localities (Hurricane Cliffs and Beaver Dam Mountains) near St George, Utah. This small encrusting tubeworm, previously referred to erroneously as Spirorbis, has a laminated shell microstructure containing minute pores (punctae). The population from deeper water facies of the Beaver Dam Mountains is more abundant than that from Hurricane Cliffs and the tubes are significantly larger in size. Although represented by only one species (M. utahensis), microconchids are by far the most dominant component of the otherwise impoverished sclerobiont assemblage of the Virgin Formation, which also includes rare cemented bivalves and probable foraminifers. Whereas the remainder of the Virgin fauna is quite diverse, the low diversity of encrusters suggests a slow recovery from end-Permian mass extinctions. Indeed, more typically Mesozoic sclerobiont assemblages dominated by cyclostome bryozoans and serpulid polychaetes did not appear until the Late Triassic, probably Rhaetian.

The scorpionfly (Mecoptera) superfamily Panorpoidea underwent an Eocene radiation, replacing the extinct Mesozoic orthophlebiid grade and reaching its greatest family-level diversity: Panorpidae, Panorpodidae, Austropanorpidae, Holcorpidae, Dinopanorpidae, and a new family proposed here, the Eorpidae. Only the Panorpidae and Panorpodidae survived the Eocene and persist to the present day. This cluster of family extinctions is exceptional within Cenozoic insects. The Eorpidae includes at least one new genus and three new species described here from four localities of the early Eocene Okanagan Highlands of British Columbia, Canada, and Washington, U.S.A.: Eorpa ypsipeda n. gen. n. sp. (McAbee and possibly Falkland, BC, Canada; and Republic, WA, U.S.A.), Eorpa elverumi n. gen. n. sp. (Republic), and Eorpa jurgeni n. gen. n. sp. (Quilchena, BC). Some of the other fragmentary and poorly preserved specimens might represent further new species. We propose that the apex of Panorpoid family diversity ended by pressures from post-Eocene icehouse world climatic stress and the rise to ecological dominance of ants, some of which would have provided strong competition in scavenging for dead arthropods.

Colonial rugose corals ranging in age from Carboniferous to Late Triassic and Early Permian (Cisuralian) fusulinids have been recovered from cobbles in a conglomerate in the Upper Triassic Brisbois Member of the Vester Formation in the Izee terrane in central Oregon. Early Permian (late Sakmarian or early Artinskian) fusulinids typical of those present in the Coyote Butte Limestone in the nearby Grindstone terrane (part of the allochthonous McCloud Belt) include Eoparafusulina, Pseudofusulinella, Chalaroschwagerina, and Schwagerina. The presence of these fusulinid genera and the Pennsylvanian coral Heritschioides?, which is mostly restricted to the McCloud Belt, suggest these particular cobbles were derived from limestone in that belt. The Early Permian fusulinids Changmeia bostwicki new species and Changmeia bigflatensis new species, and the Early Permian corals Yokoyamaella? oregonensis new species and Yokoyamaella? sp. 1, all of which have Tethyan affinities, occur rarely in other cobbles. The presence of definitive fossils from the two different realms in a conglomerate associated with beds containing Late Triassic ammonoids indicates that by Late Triassic time a fragment of a Tethyan terrane was close to or had been amalgamated with a terrane belonging to the McCloud Belt.

The orthidine brachiopod genera Plaesiomys and Hebertella are significant constituents of Late Ordovician benthic marine communities throughout Laurentia. Species-level phylogenetic analyses were conducted on both genera to inform systematic revisions and document evolutionary relationships. Phylogenetic analyses combined discrete and continuous characters, from which character states were determined using a statistical approach, and utilized both cladistic and Bayesian methodologies. Plaesiomys cutterensis, P. idahoensis, and P. occidentalis are herein recognized as distinct species rather than subspecies of P. subquadratus. Similarly, Hebertella montoyensis and H. prestonensis are recognized as distinct species separate from H. occidentalis, and H. richmondensis is recognized as a distinct species rather than a geographical variant of H. alveata. Hebertella subjugata is removed from its tentative synonymy with H. occidentalis and revalidated.

The development of species-level evolutionary hypotheses for Plaesiomys and Hebertella provides a detailed framework for assessing evolutionary and paleobiogeographic patterns of Late Ordovician brachiopods from Laurentia. The geographic range of Hebertella expanded throughout Laurentia during the Richmondian into both intracratonic and marginal basins. Plaesiomys subquadratus participated in the Late Ordovician Richmondian Invasion. The recovered phylogenetic topology for Plaesiomys suggests that P. subquadratus may have migrated into the Cincinnati region from a basin situated to the paleo-northeast.

The following stringocephalid brachiopods are formally described from upper Givetian (late Middle Devonian) strata of the Selennyakh Range (Northeast Asia): Omolonia antiqua Alekseeva (in Alekseeva and Nuzhdina, 1967) (subfamily Omoloninae), Geranocephalus inopinus Crickmay, 1954 and Geranocephaloides krivensis n. gen. n. sp. (subfamily Geranocephalinae), Newberria gigantea n. sp., and Rensselandioidea talyndzhaensis n. sp. (subfamily Rensselandinae). Broad paleobiogeographical connections between the seas of Northeast Asia, northwest Alaska, western Canada (Manitoba), Nevada, and also between the seas of Northeast Asia and South China are clearly established in the Givetian. In addition, two new stringocephalid-bearing communities are established: 1) the Omolonia Community in early Givetian strata of the Baird Group, northwestern Brooks Range, Alaska; and 2) the Omolonia-Geranocephaloides-Newberria-Rensselandioidea Community in late Givetian strata of the Lower Prianikskay Subsuite in the Selennyakh Range, Northeast Asia, Russia. Both of these communities occur in shallow, quiet-water, lagoonal carbonate platform environments.

Crinoid faunas from the Lower Devonian of South America are poorly known. Two new taxa are described from the Emsian Icla Formation at Cerro Kochis in the Cochabamba Department: the rhodocrinitid, Lutocrinus boliviaensis n. gen. n. sp. and Griphocrinus pirovanoi n. sp. Two additional camerates are reported from the Emsian Belèn Formation of the Altiplano region in the La Paz Department, including Ctenocrinus branisai n. sp. and Boliviacrinus isaacsoni McIntosh, 1988. In addition, a specimen of the blastoid, Pachyblastus dicki Bremier and Macurda, 1972, was recovered from the Altiplano region. These crinoids and material previously collected by Leonardo Branisa, including specimens of C. branisai n. sp., Apurocrinus sucrei McIntosh, 1981, B. isaacsoni McIntosh, 1988, and L. boliviaensis n. sp., are described and revised. The specimens give new insights into the Lower Devonian Malvinokaffric Realm of Bolivia, a relatively new frontier in crinoid paleontology.

Discovery of well-preserved specimens from the Nanba section in Yiyang, Hunan Province, in combination with a literature review, enabled us to re-evaluate and revise the graptolite genus Ancoragraptus. This is a genus of biradiate, multiramous anisograptids with horizontal to reclined rhabdosomes and free lower part of the metasicula and slightly isolated autothecal apertures. According to the revised definition, two species are included in Ancoragraptus, i.e., Ancoragraptus bulmani (Spjeldnæs, 1963) and Ancoragraptus psigraptoides Cho, Kim, and Jin, 2009. It is the first time that A. bulmani has been reported from China. The occurrences of Ancoragraptus reported worldwide are reviewed in the present study and found to be restricted to the lower upper Tremadocian. The restriction of Ancoragraptus in stratigraphical distribution makes it a taxon with a high potential for precise biostratigraphical correlation at both regional and global scale.

A partial skeleton of a pelagornithid bird found in latest Oligocene or earliest Miocene marine strata in Oregon consists of a pelvis fragment, thoracic vertebrae, and leg bones of a single individual. It is the most completely preserved pelagornithid from the late Oligocene/early Miocene, and one of the few bony-toothed birds from this time period in general. The new fossil is from the Nye Mudstone and shows some previously unknown features that contribute to a better understanding of the osteology of pelagornithids. Because Paleogene and late Neogene pelagornithids differ in several osteological features and the temporally intermediate forms are poorly known, it further bridges a gap in our knowledge of character evolution in pelagornithids. The interrelationships within Pelagornithidae are still poorly resolved, but we detail that a clade of Neogene species, which the Oregon pelagornithid is not part of, can be supported by a derived morphology of the femur. To ease description of Neogene pelagornithids, we synonymize Palaeochenoides Shufeldt, 1916 and Tympanonesiotes Hopson, 1964 with Pelagornis Lartet, 1857, and suggest classification of all Neogene pelagornithids in the latter taxon.

The Cenomanian hexactinellid assemblages are relatively rare and are known only from England and France. The phosphatized sponges from the Pokuttian Podillia in western Ukraine seem to be taxonomically the most diverse Cenomanian hexactinellid assemblage known from Europe and the world. Several new hexactinellid taxa (Class Hexactinellida) are described from the Cenomanian of Pokuttian Podillia: Myliusia rakovensis n. sp., Verrucocoelia regularis n. sp., Tretochone cretacea n. sp., Heterochone boguckii, Dunikowskiella nezvyskensis n. gen. n. sp., and Moretiella foliacea n. sp. A new lychniscosidan genus Dunikowskiella is established within the family Callodictyonidae. Until now, genus Moretiella was reported only from the Aptian of Spain and the Albian of France. The extant genera Heterochone and Myliusia are also rare as fossils. Heterochone was known from the Campanian of Germany. Myliusia, noted in the Miocene of Spain, is well documented in Late Cretaceous for the first time. Tretochone was known only from recent times. The sponges studied lived in the shelf sea, shallower than most recent hexactinellids occur.

Samples from outcrops of the Miocene Solimões and Barreiras formations from the central and coastal Amazon regions of Brazil were analyzed palynologically. Assemblages of fossil fungi were identified, and are described herein, and their relevance to paleoenvironmental and paleoclimatic studies in tropical regions discussed. The fungal assemblage comprises four spore groups, 19 species belonging to 12 genera. Additionally, two new species are proposed. The samples from the Solimões Formation contain the following taxa: Mediaverrunites elsikii, Mediaverrunites mulleri, Monoporisporites sp., Fusiformisporites crabbii, and Multicellites cingulatus. The presence of these suggests river channel margins colonized by freshwater vegetation, where seasonal fluctuations of water table and rainfall produce wetter substrates. The samples from the Barreiras Formation showed higher species and generic diversity than those from the Solimões Formation with Hypoxylonites minutus, Hypoxylonsporites ater, Hypoxylonites sp., the new species Inapertisporites multiporus n. sp., Pluricellaesporites regularis, Lacrimasporonites levis, Monoporisporites annulatus, Spirotremesporites simplex, Dyadosporites novus, Dyadosporites sp., and Multicellaesporites attenuates. All of these correspond to parasitic fungi from a range of from tropical wetlands. Spegazzinites sp. and Dicellaesporites aculeolatus, good indicators of marine influence and mangrove presence, were also identified in the samples from the Barreiras Formation. Furthermore, the fungal spore taxa Inapertisporites multiporus, Mediaverrunites elsikii, Mediaverrunites mulleri, Pluricellaesporites regularis, and Spirotremesporites simplex serve as stratigraphic indicators when combined with miospore index taxa such as Crassoretitriletes vanraadshooveni, Grimsdalea magnaclavata and Fenestrites longispinosus indicating a Miocene age for these sediments in the Amazon region.

The Late Ordovician tropidodiscid gastropod Alaskadiscus, known only in two areas in Alaska, was named by Rohr, Frýda, and Blodgett (2003). Peter Wagner and Stephen K. Donovan have pointed out to us that the name was previously used for a Cambrian trilobite, Alaskadiscus Zhang, 1980. We propose the new name Alaskodiscus with the same type species, A. donensis Rohr, Frýda and Blodgett, 2003. We feel the similarity in names is not likely to cause undue confusion since the taxa are widely separated by phyla and age.

A new arthropod, Kootenichela deppi n. gen. n. sp., is described from the Stanley Glacier exposure of the middle Cambrian (Series 3, Stage 5) Stephen Formation in Kootenay National Park (British Columbia, Canada). This taxon possesses a number of primitive arthropod features such as an elongate, homonomous trunk (consisting of at least 29 segments), poorly sclerotised trunk appendages, and large pedunculate eyes associated with an anterior (ocular) sclerite. The cephalon encompasses a possible antenna-like appendage and enlarged raptorial appendages with a bipartite peduncle and three spinose distal podomeres, indicative of megacheiran (“great-appendage” arthropod) affinities. The relationships of megacheirans are controversial, with them generally considered as either stem-euarthropods or a paraphyletic stem-lineage of chelicerates. An extensive cladistic analysis resolved Kootenichela as sister-taxon to the enigmatic Worthenella cambria from the middle Cambrian (Series 3, Stage 5), Burgess Shale Formation in Yoho National Park (British Columbia), which is herein reinterpreted as a megacheiran arthropod. Based on their sister-group relationship, both taxa were placed in the new family Kootenichelidae, to which Pseudoiulia from the Chengjiang biota is also tentatively assigned. All of these taxa possess an elongate, multi-segmented body and subtriangular exopods. This family occupies a basal position within a paraphyletic Megacheira, the immediate outgroup of Euarthropoda (crown-group arthropods). The resultant topology indicates that analyses that have resolved megacheirans as stem-chelicerates have done so because they have rooted on inappropriate taxa, e.g., trilobitomorphs and marrellomorphs.

The feather-shaped Plumalina Hall, 1858 is revised on the basis of new and reexamined specimens from New York. Previously described from Givetian through Famennian deposits, a single compression of P. tenera n. sp. from the Rochester Shale extends the range into the Wenlock, and provides new information regarding Plumalina's biology. We assess the utility of morphologic characters in diagnoses of taxa, and present the first quantitative analysis of fossil hydroids to distinguish P. brevis n. sp. (Frasnian) from other Devonian species.

Plumalina has been compared to plants, graptolites, and octocorals. Some interpretations have proposed affinities among hydrozoans based on colony form and the presence of putative polyp bases. Our analysis shows that, like extant thecate hydrozoans, Plumalina had a delicate, chitinous hydrocaulus with weakly articulated hydrocladia. An assemblage of in situ specimens, steeply inclined relative to the bedding plane in an Ithaca Formation (Frasnian Stage) turbidite, indicates that Devonian species produced sessile, erect colonies attached to a hard substrate, comparable to extant hydroids that feed in currents. Morphometric comparisons between putative Plumalina polyp bases and polyp bases of modern analogues reveal similarities to hydroids in the superfamily Plumularioidea McCrady, 1859. Plumalina is the most abundant fossil hydroid so far reported, and is pertinent to interpretations of the hydrozoan record.

Simojovelhyus pocitosense is based on a lower jaw fragment with three molars from the late Oligocene amber mine deposits near the village of Simojovel, Chiapas Province, Mexico. It is the oldest fossil mammal known from Central America. It was described by Ferrusquia-Villafranca in 2006 as a helohyid, a group of primitive artiodactyls known from the Bridgerian and Uintan (older than 49–42 Ma), yet it comes from early Arikareean deposits about 25–27 Ma, suggesting that it was a very late helohyid living more than 10 m.y. after their apparent Uintan extinction. We re-examined the specimen, and compared it to the large collection of recently described peccaries from the Chadronian (Perchoerus minor) and Orellan (Perchoerus nanus) and Bridgerian helohyids (Helohyus sp.). Once the range of variation of characters in helohyids and peccaries is accounted for, Simojovelhyus shows derived similarities to early peccaries, especially in the bunodont molars with inflated cusps and the configuration of cristids and accessory cuspulids, and none of the incipient lophodonty and primitive morphology seen in helohyids. In fact, the only real similarity other than symplesiomorphies between Simojovelhyus and helohyids is its small size, but it is close to the size range of the tiny Chadronian peccary P. minor. Thus, based on both derived tooth characters and its age, it is much more parsimonious to regard Simojovelhyus as a tiny Mexican peccary from the Arikareean, not a very late helohyid. This removes the anomalously late occurrence of helohyids from the mammalian fossil record, and forces a re-examination of our view of mammalian evolution in Central America.

The Nunn Member (early Osagean) of the Lake Valley Formation of New Mexico is known for its abundance and diversity of crinoids. Although crinoids were first reported in the late 1800s, no comprehensive study of the crinoids has been conducted and a complete list of the crinoid taxa does not exist. All subclasses of crinoids occur in the Lake Valley, but the camerates are by far the dominant group. Study of the Macurda collection from the University of Michigan, the Laudon collection from the University of New Mexico, and new collections provided more than 7000 specimens, 4,500 of which were identifiable camerates. Sixty-one species of camerates are recognized in the Nunn Member, including five new species: Blairocrinus macurdai, Iotacrinus novamexicanus, Agaricocrinus alamogordoensis, Uperocrinus kuesi, and Collicrinus laudoni. This camerate fauna is very similar to that of the lower Burlington Limestone of the Mississippi Valley. An update of the crinoid taxa in the Lake Valley Formation allows for a better understanding of the temporal and geographic relationships of crinoid faunas across North American during the Early Mississippian when camerates were at their global diversity maximum. The majority of the camerates come from the western New Mexico outcrops where the Nunn Member is thicker and the marine shelf was shallower, but several also occur in association with the deep-water Waulsortian mounds.

Isolated teeth from the Middle Permian (early Guadalupian) Kaibab Formation of Arizona are described as a new species of the xenacanth shark genus Bransonella. Bransonella tribula n. sp. is a small tooth in which the intermediate cusp is 65% of the length of the principal cusps and the cristae on the labial face extend down over the base, covering it, and bifurcating to form distinctive double crested ridges. Fin spines from the same localities in the Kaibab Formation show the characteristic xenacanth feature of a double row of large thorn-like denticles along the posterior margin. Bransonella tribula n. sp. is the only xenacanth shark known from the Kaibab Formation at present, however, due to the lack of articulated material the fin spines are attributed to ?Bransonella tribula n. sp. The ecomorphology of Bransonella suggests a primitive, small, gracile, marine xenacanth that fed near the sea floor like the modern catsharks (Scyliorhinidae).

A thalattosaur taxon, Concavispina biseridens, was recently named and briefly described. It is described here in detail and compared with other thalattosaurs, especially Xinpusaurus. Concavispina is characterized by a long skull, measuring approximately half the length of presacral portion of the vertebral column, two rows of blunt teeth on the anterior part of the maxilla, and neural spines that have convex anterior or posterior margins and V-shaped notches in their dorsal margins. Concavispina differs from all thalattosaurs except Xinpusaurus in that the anterior end of the maxilla is curved dorsally, less than five cervical vertebrae are present, and the proximal end of the humerus is wider than the distal end. Phylogenetic analysis of 40 characters suggests that Miodentosaurus occupies a basal position within Askeptosauridea, Paralonectes is the basalmost member of Thalattosauridea, Concavispina may form a clade with Xinpusaurus, and Chinese thalattosaurs do not have a close relationship with eastern Pacific forms as suggested by previous studies. Concavispina may have been similar to Xinpusaurus in overall locomotor style, but probably had a poorer swimming ability. Concavispina likely differed from Xinpusaurus in diet, for example by depending on softer food.

A Maastrichtian rudist fauna composed of the radiolitids Biradiolites aguilerae Böse, B. Cárdenasensis Böse, Huasteca ojanchalensis (Myers), Tampsia floriformis Myers, and Trechmannites rudissimus (Trechmann), the hippuritids Caribbea muellerriedi (Vermunt) and Praebarrettia sparcilirata (Whitfield) sensu lato, and the plagioptychids Coralliochama gbohemi Böse and Mitrocaprina tschoppi (Palmer) is described from the Cárdenas Formation in San Luis Potosí State, Mexico. Abundant fossil material and excellent preservation of a number of specimens allowed observation of both the internal and external shell characters and their ontogenetic and eco-phenotypic variability. The description of some hitherto insufficiently known species has been enhanced and/or completed, making easier their subsequent identification and allowing their unequivocal generic assignation. Two new genera, Huasteca and Trechmannites, are proposed for two already known species of radiolitids. The Cárdenas Formation exhibits a continuously exposed sequence in the vicinity of Cárdenas. Thus, precise stratigraphic location of all fossil localities and their rudist associations, ranging from the early to the early late Maastrichtian, has been possible.