A 1901 report by the Smithsonian Custodian of Paleozoic Plants noted that the nonbiomineralized taxa Buthotrephis divaricataWhite, 1901, B. newliniWhite, 1901, and B. lesquereuxiGrote and Pitt, 1876, from the upper Silurian of the Great Lakes area, shared key characteristics in common with the extant green macroalga Codium. A detailed reexamination of these Codium-like taxa and similar forms from the lower Silurian of Ontario, New York, and Michigan, including newly collected material of Thalassocystis striataTaggart and Parker, 1976, aided by scanning electron microscopy and stable carbon isotope analysis, provides new data in support of an algal affinity. Crucially, as with Codium, the originally cylindrical axes of all of these taxa consist of a complex internal array of tubes divided into distinct medullary and cortical regions, the medullary tubes being arranged in a manner similar to those of living Pseudocodium. In view of these findings, the three study taxa originally assigned to Buthotrephis, together with Chondrites verusRuedemann, 1925, are transferred to the new algal taxon Inocladus new genus, thereby establishing Inocladus lesquereuxi new combination, Inocladus newlini new comb., Inocladus divaricata new comb., and Inocladus verus new comb. Morphological and paleoecological data point to a phylogenetic affinity for Inocladus n. gen. and Thalassocystis within the Codium-bearing green algal order Bryopsidales, but perhaps nested within an extinct lineage. Collectively, this material fits within a large-scale pattern of major macroalgal morphological diversification initiated in concert with the Great Ordovician Biodiversification Event and apparently driven by a marked escalation in grazing pressure.

The late Ediacaran (Nama) Fossil Assemblage from the Kushk Series in the Kushk and Chahmir areas of Central Iran highlights a diverse community of globally distributed, soft-bodied (non-skeletonized) Ediacara biota coexisting with skeletonized tubular forms of likely metazoan affinities. Several biostratigraphically and biogeographically important taxa are reported (i.e., erniettomorphs, rangeomorphs, cloudinomorphs, kimberellomorphs, Chuaria, Corumbella), including Convolutubus dargazinensis new genus new species, a new organic-walled tubular organism, allowing for paleoecological studies to be performed. This study highlights the need for continued investigations into the late Ediacaran of Iran, and suggests a biosphere in transition, with a shift in diversity and abundance from large Ediacara biota to organic-walled and skeletonized tubular organisms at the dawn of the Cambrian Explosion.

Eight bryozoan species are described from the Hanchiatien Formation (lower Silurian, Telychian) of southern Chongqing, South China. Four species are new: the trepostomes Asperopora sinensis n. sp., Trematopora jiebeiensis n. sp., and Trematopora tenuis n. sp., and the fenestrate Moorephylloporina parvula n. sp. One species, the cystoporate Hennigopora sp. indet., is described in open nomenclature. Moorephylloporina parvula n. sp. is eurytopic, occurring in all types of facies within the bioherms. Erect MoorephylloporinaBassler, 1952, TrematoporaHall, 1852, and LeioclemaUlrich, 1882 formed pioneering communities on weakly cemented substrata, whereas encrusting FistuliporaM‘Coy, 1849, HennigoporaBassler, 1952, and AsperoporaOwen, 1969 occurred on hardgrounds and formed densely compact framestones. Robust branched Trematopora and Leioclema tend to occur out of the reef core (framework) where they could have formed reef-flank thickets in more agitated conditions. The generic composition of the studied fauna correlates with other localities in South China, and they show general paleobiogeographic relations to Siberia and Indiana, USA.

Cribrilinid bryozoans originating from Pleistocene deep-water sediments from two localities near Messina (Sicily, Italy)—Capo Milazzo (Gelasian) and Scoppo (Calabrian)—were examined. Five cribrilinid species were found, three in each locality and time interval, with only one species shared. Three species, Cribrilaria profunda n. sp., Glabrilaria transversocarinata n. sp., and Figularia spectabilis n. sp., are new to science. Of the two remaining species, Figularia figularis was already known from local fossil associations, whereas Glabrilaria pedunculata, a present-day Mediterranean species, is recorded for the first time as a fossil. New combinations are suggested for two species previously assigned to Puellina, Cribrilaria saldanhai (Harmelin, 2001) n. comb. and Cribrilaria mikelae (Harmelin, 2006) n. comb. The diagnosis of the genus Figularia was amended to include an erect growth morphology in addition to the encrusting form, and the occurrence of ooecia formed by the distal kenozooid. Following a literature revision of all species currently assigned to Figularia, the new combinations Vitrimurella capitifera (Canu and Bassler, 1929) n. comb. and Hayamiellina quaylei (Powell, 1967a) n. comb. are suggested, and problematic species are listed and briefly discussed.

We describe two new genera of Triassic Aviculopectinoidea: Cristaflabellum n. gen., which is biconvex and has a strongly plicate shell, and Globodiscus n. gen., which is equiconvex and externally smooth or nearly so. Globodiscus contains the new species G. kiliani n. gen. n. sp. and G. vinzenti n. gen. n. sp. In order to make the taxonomic concept of the superfamily Aviculopectinoidea more consistent with that of its sister group Pectinoidea (scallops), we use tribes rather than families or subfamilies for accommodating the new taxa. Cristaflabellum is placed in the tribe Antijanirini (previously family Antijaniridae), whereas Globodiscus is made the type genus of the new tribe Globodiscini. Both tribes are placed within the family Aviculopectinidae, which is revised to include both equiconvex and inequiconvex taxa. We suggest that tribes are a more appropriate taxonomic rank for many of the previously erected species-poor families and subfamilies of Aviculopectinoidea.

In order to maximize the utility of future studies of trilobite ontogeny, we propose a set of standard practices that relate to the collection, nomenclature, description, depiction, and interpretation of ontogenetic series inferred from articulated specimens belonging to individual species. In some cases, these suggestions may also apply to ontogenetic studies of other fossilized taxa.

Here we report and describe a new assemblage of Thylacocephala (Crustacea) from the late Spathian (Early Triassic) of Chaohu, Anhui Province, South China. The assemblage consists of at least three species from different genera: the small-sized Microcaris rectilineatus n. sp. appears the most abundant, while the large-sized Ankitokazocaris sp. and Diplacanthocaris chaohuensis n. gen. n. sp. are rare. A morphometric analysis of the carapace outline separates Diplacanthocaris chaohuensis n. gen. n. sp. from other genera. Along with Ankitokazocaris chaohuensisJi et al., 2017 and Kitakamicaris sp. from the horizon 28 m above this assemblage, four different genera of Thylacocephala occur in the Chaohu Fauna. With additional materials reported from Japan and North America, the Early Triassic is now known as the period when Thylacocephala reached their highest diversity and widest geographical distribution. Thylacocephala quickly diversified shortly after the Permian–Triassic mass extinction, probably because of their ability to survive in a relatively low-oxygen environment. Thylacocephalan fossils from Chaohu are found in dense concentrations, suggesting they might have constituted a food source for the fishes and marine reptiles in the Chaohu Fauna.

A variety of pits representing symbiotic embedments, sometimes associated with pathological deformation in the host, are known from the skeletons of Paleozoic stalked echinoderms. These structures are well known from multiple genera of crinoids and a limited number of blastozoans but have not previously been described in detail from the skeletons of rhombiferans. This is surprising given the abundance of rhombiferans in certain deposits, the co-occurrence of rhombiferans with frequently infested taxa, including diploporitans, in multiple assemblages, and the morphological similarity between certain rhombiferan taxa and coeval infested crinoids. The common hemicosmitid rhombiferan CaryocrinitesSay, 1825 is widespread throughout the middle Silurian of eastern North America and is herein reported to contain symbiotic (potentially parasitic) embedment structures. Specimens were collected from the lower portion of the mudstone lithofacies of the Massie Formation (Wenlock, Sheinwoodian) at the Napoleon quarry of southeastern Indiana, USA. Strong host specificity is indicated by the absence of pits in C. ornatusSay, 1825 and exclusive infestation of a smaller co-occurring species of Caryocrinites. Thecae with embedment structures are consistently smaller than thecae without such structures, with pitted specimens being restricted to a narrow range of thecal heights (20–24 mm). All embedment structures are present only on the proximal portion of thecae, with individual specimens containing between one and 30 pits. No elevated rims or significant swelling were observed on any specimens, and all pits are relatively small (∼1 mm in diameter). The presence of symbiotic embedment structures represents an additional example of a crinoid-like aspect to the ecology of Caryocrinites.

Twelve specimens of EumorphocystisBranson and Peck, 1940 provide the basis for new findings and a more informed assessment of whether this blastozoan (a group including eocrinoids, blastoids, diploporites, rhombiferans) constitutes the sister taxon to crinoids, as has been recently proposed. Both Eumorphocystis and earliest-known crinoid feeding appendages express longitudinal canals, a demonstrable trait exclusive to these taxa. However, the specimen series studied here shows that Eumorphocystis canals constrict proximally and travel within ambulacrals above the thecal cavity. This relationship is congruent with a documented blastozoan pattern but very unlike earliest crinoid topology. Earliest crinoid arm cavities lie fully beneath floor plates; these expand and merge directly with the main thecal coelomic cavity at thecal shoulders. Other associated anatomical features echo this contrasting comparison. Feeding appendages of Eumorphocystis lack two-tiered cover plates, podial basins/pores, and lateral arm plating, all features of earliest crinoid ‘true arms.’ Eumorphocystis feeding appendages are buttressed by solid block-like plates added during ontogeny at a generative zone below floor plates, a pattern with no known parallel among crinoids. Eumorphocystis feeding appendages express brachioles, erect extensions of floor plates, also unknown among crinoids. These several distinctions point to nonhomology of most feeding appendage anatomy, including longitudinal canals, removing Eumorphocystis and other blastozoans from exclusive relationship with crinoids. Eumorphocystis further differs from crinoids in that thecal plates express diplopores, respiratory structures not present among crinoids, but ubiquitous among certain groups of blastozoans. Phylogenetic analysis places Eumorphocystis as a crownward blastozoan, far removed from crinoids.

A new taxon of sphenodontian reptile, Micromenodon pitti new genus new species is described from the Upper Triassic (Carnian) Vinita Formation of the Richmond basin of the Newark Supergroup in Virginia. It is diagnosed by a dorsoventrally deep facial process of the maxilla that extends for almost the entire anteroposterior length of the bone and by obtusely conical, strongly ribbed additional teeth in the maxilla that comprise a greatly enlarged tooth followed by smaller teeth posteriorly. Phylogenetic analysis found Micromenodon pitti n. gen. n. sp. as an early-diverging sphenodontian with fully acrodont tooth implantation. The maxillary dentition appears functionally suited for processing hard arthropod exoskeletons and snail shells.

The sparse record of Cretaceous crocodyliforms in Australia comprises only three species, all within the genus Isisfordia. Isisfordia duncaniSalisbury et al., 2006 is from the Albian–Turonian Winton Formation of Queensland, and both Isisfordia molnariHart et al., 2019 and Isisfordia selaslophensisEtheridge, 1917 have been described from opalized material from the Cenomanian Griman Creek Formation of New South Wales. Here, we describe new cranial and postcranial material, including the most complete crocodyliform skeleton from the Cretaceous of New South Wales, which is assigned to Isisfordia cf. I. selaslophensis. We also reappraise previously described crocodyliform material from the same locality. We find that much of this material displays features that are consistent with Isisfordia.

Although the fossil record of the Late Cretaceous eastern North American landmass Appalachia is poor compared to that from the American West, it includes material from surprisingly aberrant terrestrial vertebrates that may represent relictual forms persisting in relative isolation until the end of the Mesozoic. One intriguing question is to what extent eastern and western North American faunas interspersed following the closure of the Western Interior Seaway during the Maastrichtian Stage of the Late Cretaceous ca. 70 Ma. Isolated remains from the Atlantic Coastal Plain in New Jersey have been preliminarily identified as the bones of crested lambeosaurine hadrosaurids, a derived clade known from the Cretaceous of Asia, western North America, and Europe, but have not been formally described. We describe the partial forelimb of a large hadrosaurid from the late Maastrichtian New Egypt Formation of New Jersey. The ulna preserves multiple deep scores identifiable as shark feeding marks, and both bones show ovoid and circular marks attributable to invertebrates. This forelimb is very similar to another partial antebrachium from the same area that shows evidence of septic arthritis. Both these specimens and a complete humerus from the same unit are closely comparable to the lower forelimbs of lambeosaurines among hadrosaurid dinosaurs. Although the absence of lambeosaurine synapomorphies observable on the New Egypt Formation forelimbs precludes their definite referral to Lambeosaurinae, they show that a morphotype of large hadrosauromorph with distinctly elongate forelimbs existed in the latest Maastrichtian of eastern North America and allow for a revision of the latest Cretaceous biogeography of crested herbivorous dinosaurs.

The Upper Triassic Tiki Formation of India has yielded several new cynodont taxa, which are described on the basis of multiple isolated teeth and a jaw fragment. A new species of dromatheriid, Rewaconodon indicus, is defined by a tri- and tetracuspid asymmetric crown, long anterior edge of the major cusp a, cingular cusps d and f, and marked constriction at the crown-root junction. Another new dromatheriid, Inditherium floris n. gen. n. sp., is characterized by a broad, flower-shaped pentacuspid crown, multiple cingular cusps, and a weak lingual cingulum is also described from the same horizon. In addition, a new mammaliamorph taxon, Tikiodon cromptoni n. gen. n. sp., is established on a tooth specimen, which has a shovel-shaped crown, three closely spaced main cusps, a pronounced lingual cingulum with multiple cingular cusps, and a root of incomplete root bifurcation. Such a tooth morphology occupies an intermediate position between the non-mammalian cynodonts and the early mammals, as is evident from the co-occurrence of various cynodont dental morphotypes in the Tiki Formation. Moreover, Late Triassic cynodonts occurred along narrow belts demarcated by paleolatitudes, though the Indian fauna shows both Laurasian and Gondwanan affinities.

Arnebolagus leporinus Lopatin and Averianov, 2008, known previously from a single tooth (P3) from the early Eocene Bumban Member of Naran Bulak Formation at Tsagan-Khushu locality in Mongolia, is redescribed based on additional specimens from the type locality. Phylogenetic relationships of Eocene stem lagomorphs from Asia and North America are reconstructed for the first time based on a parsimony analysis of 54 morphological characters and 32 taxa. Two new node-based clades are proposed, stemming from the most-recent common ancestor of LepusLinnaeus, 1758 and Dawsonolagus Li, Meng, and Wang, 2007 (Eulagomorpha new clade, ‘lagomorphs of the modern aspect') and from the most-recent common ancestor of Lepus and Gobiolagus Burke, 1941 (Epilagomorpha new clade). Arnebolagus Lopatin and Averianov, 2008 is geologically oldest and the most plesiomorphic eulagomorph, similar to Dawsonolagus from the early Eocene Arshanto Formation of China in its weakly pronounced, unilateral hypsodonty of the upper cheek teeth and its brachyodont lower cheek teeth with separate roots. Arnebolagus is more plesiomorphic than Dawsonolagus in having two roots of P4. Arnebolagus is the oldest known eulagomorph, the only taxon known from the earliest Eocene Bumbanian Asiatic Land Mammal Age (ALMA). The other Asiatic early Eocene eulagomorphs (Dawsonolagus, AktashmysAverianov, 1994, and RomanolagusShevyreva, 1995) come from the Arshantan ALMA.

We undertake a redescription of the equid sample from the Early Pleistocene of Roca-Neyra, France. This locality has been recently calibrated at the Pliocene/Pleistocene boundary (2.6 ± 0.2 Ma) and therefore it is of interest for the first appearance of the genus Equus and last appearance of hipparionine horses. The Roca-Neyra equid sample, reanalyzed herein using morphological, morphometrical, and statistical analyses, has revealed the co-occurrence of Plesiohipparion cf. ?P. rocinantis and Equus cf. E. livenzovensis. The analysis undertaken on several European, African, and Asian “Hipparion” sensu lato species from late Miocene to Early Pleistocene has revealed different remnant Hipparion lineages in the Plio-Pleistocene of Europe: Plesiohipparion, Proboscidippaion, and likely Cremohipparion. The discovery of the first European monodactyl horse, Equus cf. E. livenzovensis correlates Roca-Neyra with other 2.6 Ma European localities in Italy, Spain, and in the Khapry area (Azov Sea region). The morphological description of the Equus cf. E. livenzovensis lower cheek teeth has highlighted intermediate features between the North American Pliocene species Equus simplicidens and Early Pleistocene European Equus stenonis. Our study supports the hypothesis that E. livenzovensis is a plausible evolutionary predecessor for the Equus stenonis group. These observations underscore the importance of Roca-Neyra as an important locality for the last European hipparions and the first Equus in the Early Pleistocene of Europe.