The Kel'tminskaya-1 borehole, drilled along the northeastern margin of the East European Platform (EEP), reveals some 3,600 m of Neoproterozoic sedimentary rocks, mostly confined to the subsurface. The upper 1,000 m of the drilled section correlates with late Ediacaran Redkino and Kotlin successions on the EEP, whereas the lowermost 2,000 m can be related to pre-Sturtian (Upper Riphean) deposits in the Ural Mountains. In between lies the Vychegda Formation, a 600 m siliciclastic succession that has no counterpart in classic EEP stratigraphy.

Vychegda microfossils can be separated into three assemblages. The upper part of the formation contains large, profusely ornamented acritarchs broadly comparable to those of the Ediacaran Complex Acanthomorph Palynoflora, including species of the genera Alicesphaeridium, Asterocapsoides, Cavaspina and Tanarium confined to Ediacaran-aged assemblages elsewhere. Diverse large acanthomorphs are known from Ediacaran strata around the world, but have not previously been recognized from the EEP, an absence attributed to a hiatus between the glacial Laplandian (>635 Ma) and Redkino (mostly <555 Ma) successions. The large acanthomorphic acritarchs record eukaryotic organisms with resting stages in their life cycles and likely include egg or diapause cysts of early animals. In contrast, the lower Vychegda assemblage, found in the basal 10 m of the succession, contains taxa typical of earlier Neoproterozoic successions. The middle assemblage contains only simple filaments and spheroidal acritarchs.

The most parsimonious interpretation of Vychegda biostratigraphy is that pre-Marinoan rocks in the basal part of the formation are separated by a cryptic unconformity from early and middle Ediacaran deposits above. This interpretation is consistent with data from China and Australia, which indicate that the major paleontological transition to diverse ECAP assemblages took place within the Ediacaran Period and not in association with the preceding ice age. Vychegda acritarch assemblages thus contribute to a biostratigraphic model for the initial Ediacaran boundary.

Although used in biostratigraphy and in studies of early Cambrian trilobite evolution, the olenelloid genus Peachella has received little research attention. The ontogenetic and evolutionary origins of its derived features—an effaced cephalon and grossly inflated genal spines—have remained mysterious. Based on examination of new and existing collections, P. iddingsi and P. brevispina are here described in detail, including aspects of their respective ontogenies and the first description of the thorax of P. iddingsi. A new monotypic genus, Eopeachella, is also described from recently collected material from the Delamar Member of the Pioche Formation, Nevada. Eopeachella angustispina n. gen. n. sp., is less derived and stratigraphically older than both Peachella species and bridges the morphological gap between Peachella and typical olenelloids. The study reveals that cephalic effacement was progressively attained during both ontogeny and phylogeny in the Eopeachella Peachella clade. Comparative ontogeny with other olenelloids reveals that progressive effacement was a trend superimposed upon and independent of a conserved pattern of ontogenetic shape change in the glabella and did not represent a peramorphic “extension” of glabellar ontogeny. Genal spine inflation was also achieved progressively (in a proximal-to-distal direction) through both ontogeny and phylogeny in the Eopeachella Peachella clade. Genal spine inflation that convergently arose in later trilobite groups may have been similarly ontogenetically dynamic. Discovery of E. angustispina and P. brevispina in the Delamar Member raises olenelloid diversity in this member to at least 20 species; a higher diversity than in any coeval unit.

During the Eocene, Hahajima Island of the Ogasawara (Bonin) Islands of the Izu-Mariana Arc in the North Pacific was located near the present-day position of western Pacific Micronesia. We identified 17 Eocene ostracode species from the island, of which are new species and likely endemic to this island or to the West Pacific. These new species are systematically described herein and include: Costa matsumarui n. sp., Cytherelloidea ogasawaraensis n. sp., Havanardia ujiiei n. sp., Jugosocythereis nishii n. sp., Neonesidea boninensis n. sp., Schizocythere antiquimicronesiana n. sp., and Uroleberis hahajimaensis n. sp. The Eocene ostracode fauna has a higher rate of endemism than does the modern Micronesian fauna and contains Tethyan genera. These findings contradict a hypothesis that the Pacific fauna had a higher endemism rate after the Paleogene. The findings support another hypothesis that some genera invaded the Pacific from Tethys during the Paleogene. They suggest that West Pacific species did not disperse to the periphery of the Indo-West Pacific region during the Middle–Late Eocene. The “center of origin” hypothesis cannot be applied to Middle–Late Eocene marine ostracode biogeography.

The previously poorly known “Tapiravus” polkensis Olsen, 1960 (Mammalia, Perissodactyla, Tapiridae) is now known from abundant, well preserved specimens from both the type area in central Florida and from the Gray Fossil Site (GFS) in eastern Tennessee. The latter has produced over 75 individuals, the greatest number of tapirids from a single fossil site, including many articulated skeletons. Almost all linear measurements taken on skulls, mandibles, and cheek teeth from GFS have coefficients of variation less than 10 (most between 3 and 7), indicating the presence of a single species. However, the sample reveals considerable intraspecific variation for a few key morphologic features, including development of the sagittal crest, outline shape of the nasals, and number and relative strength of lingual cusps on the P1. The Florida sample of T. polkensis is more limited, but has the same state as the GFS sample for all preserved characters of systematic significance, and while the Florida teeth are on average smaller (especially narrower lower cheek teeth), they fall either within or just below the observed range of the Gray Fossil Site population. The new material supports a reassignment of “Tapiravus” polkensis to the genus Tapirus, and demonstrates that the geologic age of the species is significantly younger than previously thought, Hemphillian rather than Barstovian. Tapirus polkensis is the smallest known North American Tapirus, and smaller than any of the extant species in the genus, with an estimated average mass of 125 kg.

Previously unknown ontogenies of five lichid genera, Dicranopeltis, Platylichas, Borealarges, Dicranogmus and Radiolichas, are described and placed in the context provided by a review of known lichid ontogenies. Lichid phylogenies have been based on holaspid morphology alone without reference to ontogeny. To broaden knowledge of lichid phylogeny, an analysis, based on the last protaspid instar of lichids and possible sister group taxa, is conducted. The results of this analysis show that, within the lichids, the traditional subfamily groupings are not supported, and the sister group of lichids is more likely to be found within the Proetida than the Odontopleurida. Tubercles, a prominent feature of lichid morphology, have not been considered taxonomically significant. An examination suggests that tubercle arrangement and the pattern of change of tubercle arrangement through ontogeny could be important in defining taxa. It is recommended that future work on lichid phylogeny include ontogenetic information and patterns of change in development.

Three rugose species in two genera—Nanshanophyllum hamadai n. sp., N. gokasense n. sp., and Shensiphyllum sp.—are described for the first time from the Kurosegawa Terrane, Southwest Japan. These species occur in the Middle Member of the Gionyama Formation, which is Late Llandovery to Early Ludlow (Silurian) in age. The two genera, Nanshanophyllum and Shensiphyllum, formerly were known only from South China and Qaidam. The occurrence of these two genera in Japan may indicate a paleogeographic connection between ‘Proto-Japan’ and the South China Block during the Silurian.