Numerous Early Cambrian corals or “coralomorphs,” as they are often classified, are recorded from North America, Australia, and Siberia. A new Early Cambrian coral, Harklessia yuenglingensis n. gen. and sp., is found in conjunction with archaeocyathan-microbial reefs in Esmeralda County, southwestern Nevada. The coral-bearing reefs are within quartzic, trilobite-rich packstone beds in the upper portion of the Harkless Formation (Bonnia–Olenellus Zone). Coralla are constructed by subpolygonal to polygonal, cerioid, close-packed corallite tubes. Coralla average 12 cm in height by 18 cm in diameter with individual corallite tubes ranging from 1.2 to 3.2 mm in diameter. Corallites are greater than 25 mm in length. Septa and tabulae are not present.

Many of the Early Cambrian corals previously described have attributes of the class Anthozoa and subclass Zoantharia, with some specific similarities to tabulate corals. Harklessia yuenglingensis is placed confidently within the class Anthozoa, subclass Zoantharia because its morphological characteristics indicate an affinity to true corals, but whether H. yuenglingensis is a tabulate coral remains uncertain.

One new species of retiolitid, Gothograptus storchi, five new species of monograptids (Monograptus patulus, Monograptus glutiformis, Streptograptus galeus, Testograptus cubitus, and Monoclimacis capillus), and one new cyrtograptid, Cyrtograptus palmatus, are described from the lower Homerian lundgreni Biozone of Arctic Canada. The presence of a species of Gothograptus in the Cyrtograptus lundgreni Biozone of Arctic Canada is documented for the first time. Further, full-relief specimens of Cyrtograptus multiramis Törnquist? and C.? urbaneki Teller are described. Better and more completely preserved, isolated material of Sokolovograptus cf. S. parens Obut and Zaslavskaya, Pseudoplectograptus sagenus, Cometograptus apsis, C. nevadensis, Monograptus biglossa, Cyrtograptus hamatus, C. lundgreni, and C. radians, previously described in Lenz and Kozłowska-Dawidziuk (2001a), is also illustrated. The total global species diversity of the lundgreni Biozone thus approaches 50, making the subsequent extinction event even more profound.

Two new xyloiuloid millipedes (Diplopoda: Chilognatha: Juliformia) are described and placed in the new family Gaspestriidae: Gaspestria genselorum n. gen and sp. from the Emsian of Québec and New Brunswick and Sigmastria dilata n. gen. and sp. from the Pragian of the Midland Valley of Scotland. These new millipedes extend the stratigraphic range of xyloiuloid millipedes, which previously were only described from the Pennsylvanian of Europe and North America. All xyloiuloid millipede families are placed within the superfamily Xyloiuloidea which is left incertae sedis within Juliformia due to a lack of preservation of diagnostic characters that would allow placement within an extant order. The presence in the Lower Devonian of the superorder Juliformia, universally agreed among diplopod taxonomists to represent the most derived clade of Diplopoda, indicates that most of millipede cladogenesis leading to high-rank extant clades had to have occurred by this time, much earlier than previously indicated by the fossil record. A stratocladogram for Myriapoda is constructed, and in combination with data from the plant fossil record and nuclear protein-encoding genes, new hypotheses regarding timing of millipede high-rank cladogenesis in the Paleozoic are formulated. These include terrestrialization of Diplopoda no later than the Ordovician along with the origin of the lineage leading to Penicillata and Arthropleuridea, followed by a period of relative stasis until the Middle Silurian, at which point there was a rapid radiation of Diplopoda, producing most of the high-rank clades by the Lower Devonian.

Hystricurus millardensis Hintze, 1953 has been recorded widely in Laurentia. Revision on the basis of abundant new silicified topotype material indicates that most of these records are of morphologically distinct, though related, taxa and that a plexus of related species is involved. The new genus Millardicurus, with H. millardensis as type, is proposed for this clade, which also includes two well-documented new species, M. housensis and M. paramillardensis, from the House Formation of western Utah, several named species from Greenland, and several unnamed new species from various parts of Laurentia that have in the past been referred to M. millardensis. Millardicurus is not apparently closely related to younger Skullrockian–Stairsian hystricurids from Laurentia, but may be related to poorly known coeval Siberian Platform species classified in the genus Nyaya Rozova, 1963. Landmark-based geometric morphometric methods comprising principal component analysis of partial warp scores and Goodall's F test of pairwise means indicate significant shape differences among cranidia, librigenae, and pygidia of the House Formation species of Millardicurus.

The pre–Pleistocene fossil record of sturgeons (family Acipenseridae) from North America is reviewed based on a survey of reports in the literature and firsthand examination of specimens in museum collections. We provide a redescription of the only known specimen of †Protoscaphirhynchus squamosus (Late Cretaceous, Montana), a very poorly preserved specimen for which few morphological details can be determined. Three taxa described as species of the genus Acipenser from North America (†A. albertensis, †A. eruciferus, and †A. ornatus) were described based on isolated and fragmentary remains, and are here considered to be nomina dubia. The earliest reported remains of North American sturgeons are from the Late Cretaceous (Santonian to Campanian Milk River Formation). There is a relatively continuous record, with the exception of the Eocene and Oligocene, in which there are few (potentially in the Eocene) or no (Oligocene) known specimens available in collections. We have found that nearly all specimens are best regarded as Acipenseridae indeterminate genus and species due to their fragmentary preservation and lack of preserved diagnostic characters.

A new fish fauna is described from the late Middle Miocene (Volhynian; early Sarmatian sensu lato) of Tsurevsky, North Caucasus, Russia. Ten taxa belonging to nine families are described, of which two may be new (Micromesistius sp., Bothus sp.), but not formally described awaiting better-preserved material. The predominant faunal element is Sardinella sardinites, including more than 42% of all investigated specimens. The paleoecological analysis reveals a semienclosed marine environment not far from the coast, characterized by shallow depths and a soft bottom. The sedimentological features of the deposits and the preservation of the specimens suggest that periodic oxygen minima affected the bottom waters, causing repeated hypoxic events, probably related to the decay of organic matter previously accumulated in the basin. Paleoenvironmental considerations of fish faunas from several Paratethyan localities suggest that marine waters characterized by a little shift in chemical composition (high alkalinity) filled up the entire basin during the Sarmatian.

Erosion of the upper Arkadelphia Formation by the Ouachita River in Hot Spring County, Arkansas, has revealed a diverse and abundant, late Maastrichtian chondrichthyan fauna representing at least 17 species: Squatina hassei, Ginglymostoma lehneri, Plicatoscyllium derameei, Ondontaspis aculeatus, Carcharias cf. C. holmdelensis, Serratolamna serrata, Squalicorax kaupi, Galeorhinus girardoti, Rhinobatos casieri, Ischyrhiza avonicola, Ischyrhiza mira, Sclerorhynchus sp., Ptychotrygon cf. P. vermiculata, Raja farishi, Rhombodus binkhorsti, and Dasyatis sp. All of these species are widely known from the Upper Cretaceous of North America. An extremely rare species, Schizorhiza cf. S. stromeri, currently known only from Mexico and Africa, is also present. The chondrichthyan remains occur almost entirely as teeth scattered by river activity across the surface of the marl and marly clay of the Arkadelphia Formation and can be collected from within localized accumulations of river sediments. Also present with the chondrichthyan remains are teeth from actinopterygians and reptiles as well as molluscan steinkerns, echinoid spines, and fragments of branching corals. This fauna expands the known geographic distribution of late Maastrichtian chondrichthyans in North America, and provides an important biostratigraphic connection between fauna of the Gulf Coastal Plain and Western Interior Seaway. It also supports the idea of a significant chondrichthyan turnover across the Cretaceous–Tertiary boundary.

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.

The skeletal anatomy of the Early Permian eureptile Thuringothyris mahlendorffae from the Bromacker Quarry, Germany, is redescribed on the basis of several new specimens. The taxon retains some plesiomorphic characters, such as an ectopterygoid and a tabular, but it also possesses low neural spines and nonswollen neural arches, a combination that is unique for early eureptiles. A phylogenetic analysis places Thuringothyris as the sister taxon of Captorhinidae, excluding any potential “protorothyridid” affinities. Implications of this study are that the swollen neural arches of captorhinids and araeosceloids might have evolved independently, that a downturned rostrum occurred only later in captorhinid evolution, and that the European Permian is important to the understanding of the origin of eureptiles.

The skull of a carnivorous therapsid from the Tapinocephalus Assemblage Zone of the Beaufort Group, Middle Permian of South Africa, is described as a new burnetiamorph biarmosuchian. Pachydectes elsi n. gen. and sp. is distinguished from all other therapsids by its possession of a conspicuous pachyostotic maxillary boss that sheathes the root of the upper canine. It shares the presence of a preparietal ossification with other biarmosuchians and a pachyostotic boss below the postorbital bar with other burnetiamorphs. Pachydectes is the first burnetiamorph known from along the Ecca-Beaufort contact in the eastern part of the Karoo Basin and only the second burnetiamorph to be described from the Tapinocephalus Assemblage Zone. All other South African burnetiamorphs, save Bullacephalus jacksoni, are known from much younger biozones of the Beaufort Group. Our phylogenetic analysis links Pachydectes and Bullacephalus, which are the stratigraphically lowest-occurring taxa, with Burnetia, the burnetiamorph known from the highest position in the lower Beaufort Group. This result suggests that most of the history of biarmosuchians in South Africa is unrecorded.

The earliest known record of lingulid-coral associations is described from Ashgill tabulate corals preserved on Manitoulin Island, Ontario. Lingulid infestation of tabulate corals and stromatoporoids also is locally abundant in Ashgill and Llandovery limestones on Anticosti Island, Québec, and these preserve the new lingulid species Rowellella? anticostiensis inside the cavities of Trypanites borings. In all examples, lingulids appear to nestle in previously formed Trypanites, likely in a dead host coral or stromatoporoid. In some instances in the Silurian of Anticosti, regeneration of host growth while infested by lingulids is evidenced by a new type of compound trace fossil, Klemmatoica linguliforma new ichnogenus and ichnospecies. Similar endosymbiotic relationships previously observed in Silurian corals from Wales and Sweden suggest that the lingulid association with tabulate corals and stromatoporoids was widespread in early Paleozoic shallow marine settings.

Entobia, a sponge boring commonly consisting of interconnected chambers and galleries (i.e., it is camerate), is a dominant agent of bioerosion in Mesozoic and Cenozoic marine carbonates. A similar camerate boring, Topsentopsis devonica, is widely recognized from the Devonian, and its classification is reappraised here. This paper synonymizes Topsentopsis with the senior synonym Entobia, making E. devonica n. comb. the oldest representative of the ichnogenus. New specimens of E. devonica borings in stromatoporoids and megalodont bivalves are described from the Frasnian Guilmette Formation of Nevada, which includes breccias of the Alamo Bolide Impact. The borings occur in skeletal substrates both within and above the impact event breccias, demonstrating their existence prior to the impact and their survival of the catastrophic event. The Nevada discovery extends the geographic distribution of the oldest Entobia to include the western and midcontinental United States, western Canada, and eastern Europe. E. devonica was an important bioerosive agent during the Givetian–Frasnian, but it is unknown following the Frasnian–Famennian mass extinction.

A fossilized social insect nest, Socialites tumulus new ichnogenus and ichnospecies, is described from continental strata of the Upper Cretaceous Kaiparowits Formation in southern Utah. Nine discrete nest structures are preserved along a single bedding plane, within an area of about 25 m². Fine-grained, ripple-laminated sandstone, interpreted as a fluvial crevasse splay deposit, drapes the nest structures and is thought to have rapidly buried and preserved much of the aboveground architectural morphology of the nest structures. Such social insects as ants and termites are considered as possible tracemakers. Comparison to fossil and modern nests suggests that Socialites tumulus is more similar to nests produced by ants than by termites. This trace fossil preserves rare, tangible evidence of nest construction by social insects during the Late Cretaceous, adding new information on insect diversity and habitat utilization in Mesozoic terrestrial ecosystems. Detailed study of these complex nest structures also aids in paleoenvironmental reconstruction, revealing multiple phases of nest construction, burial, and reestablishment.