A unique radiolarian fauna recovered from the top part of the Changxingian stage in south Guizhou, Southwest China, includes at least nineteen species one of which is new. The fauna is mainly composed of Permian species extensively distributed all over the world, such as Hegleria mammilla (Sheng and Wang, 1985); Ishigaum trifustis De Wever and Caridroit, 1984; Foremanhelena triangula De Wever and Caridroit, 1984; Triplanospongos dekkaensis (Noble and Renne, 1990); Nazarovella gracilis De Wever and Caridroit, 1984; and Nazarovella inflata Sashida and Tonishi, 1986, among others. Besides these species, a new radiolarian assemblage, represented by Copicyntra ziyunensis new species; Copiellintra fontainei (Sashida, 2000); Klaengspongus spinosus Sashida, 2000; and Paroertlispongus? sp., was discovered in South China. The assemblage only occurs in less than 10 m siliceous rock strata under the Permian-Triassic boundary at south Guizhou, Guangxi, and north Sichuan. Although only a few new species appeared during this period, they are very important for understanding both the radiolarian extinction at the end of the Permian and the relation between the Paleozoic and Mesozoic Radiolaria.

The reticuloceratid ammonoid Arkanites relictus (Quinn, McCaleb, and Webb, 1962) is represented by hundreds to thousands of individuals from horizons isolated both stratigraphically and geographically in northern Arkansas. These assemblages appear to represent mass mortality events resulting from a semelparous reproductive strategy. Arkanites relictus occurs as a dimorphic pair (depressed, widely umbilicate, cadiconic conchs and compressed, narrowly umbilicate, pachyconic conchs) thought to reflect sexual dimorphism. Late stage ontogenetic modifications, such as septal crowding and change in aperture profile, are widely cited evidence of sexual maturity in ammonoids. Septal crowding begins at a predictable ontogenetic stage in the compressed forms of A. relictus, but specimens with cadiconic conchs do not have crowded septa even at the largest diameters available.

Depending on the trait examined and the proxy for age of individuals, the dimorphism in Arkanites relictus (using the depressed form as the reference morph) is the result of acceleration, neoteny, or hypermorphosis plus neoteny. If size (diameter) is considered a proxy for age, the dimorphs were the same age at death, and the septa in the compressed variants developed via acceleration relative to the depressed variants. Regarding conch shape (width vs. diameter), the compressed morphs developed via neoteny relative to the depressed morphs. If septal count is considered a proxy for age, the dimorphs were not the same age at death, and the compressed forms were produced by a combination of hypermorphosis plus neoteny, i.e., they grew longer yet slower than the depressed forms. In A. relictus, the heterochronic processes of hypermorphosis and neoteny may have been operating simultaneously, which is an interesting possibility because it is an example of a combination of both peramorphic and paedomorphic processes.

The Fossil Brook Member of the upper Chamberlain's Brook Formation is a thin (up to 14 m) but distinctive, unconformity-bound depositional sequence recognizable from Rhode Island to eastern Newfoundland in Avalonian North America. Its diverse trilobite fauna was first described more than century ago from the limestone-rich facies of the member in southern New Brunswick. However, the systematics, stratigraphic context, and biostratigraphic significance of these trilobites have remained poorly known. A revision of the conocoryphid and paradoxidid trilobites has been completed, and the taxa set into their stratigraphic context within the middle Middle Cambrian. The faunas of the Fossil Brook are assigned to the Eccaparadoxides eteminicus Zone of Avalon. Although biogeographic barriers between Avalon and Gondwana remained strong in the Middle Cambrian and few shared trilobite species are present, a generalized correlation of the E. eteminicus Zone into Gondwana is with the Badulesia tenera Zone of the Toushamian Stage in Morocco and the Badulesia Zone of the Caesaraugustian Stage in Spain.

A new glyptocystitidoid rhombiferan, Cheirocystis fultonensis, is described from the contact zone between the Point Pleasant Formation and lower Kope Formation exposed 50 km south east of Cincinnati, Ohio. This species, the second known glyptocystitidoid rhombiferan from the Cincinnatian Series and the youngest known species of Cheirocystis, shows significant suture modification where pectinirhombs are placed. Growth of large pectinirhombs along vertical sutures results in an unusual bowing-out of thecal plate sutures that is also seen in the related species Cheirocystis anatiformis. A juvenile specimen shows that ontogenetically the lateral shared ambulacra become less pronounced, pectinirhombs are added until the eight standard positions are expressed, and the periproct becomes proportionately smaller with age.

Aetosaur fossils from the Upper Triassic Ischigualasto Formation of Argentina formerly assigned to Aetosauroides scagliai Casamiquela and Argentinosuchus bonapartei Casamiquela are reassigned to Stagonolepis robertsoni Agassiz (small specimens) and S. wellesi (Long and Ballew) (larger specimens). Numerous features of the skull, vertebral column, appendicular skeleton, and particularly the armor, of these Argentinian aetosaurs are identical to those of Stagonolepis and differ from other aetosaurs. Identification of Stagonolepis in South America has important implications for the correlation of nonmarine strata across Late Triassic Pangea. Stagonolepis is an index taxon of the Adamanian land-vertebrate faunachron of latest Carnian age. Its occurrences in the Ischigualasto and Santa Maria formations, as well as at the type locality in the Lossiemouth Sandstone of Scotland and in the Blasensandstein of the German Keuper, cross-correlate with a well-established tetrapod biostratigraphy of the Chinle Group in western North America. Thus, all Stagonolepis records are of Adamanian (latest Carnian) age, not Otischalkian (early or “middle” Carnian) age, as proposed by some earlier workers. This correlation also demonstrates that the oldest known dinosaurs are not from the Ischigualasto and Santa Maria formations. Previous workers obtained radioisotopic dates of 227.8 Ma from the Ischigualasto Formation, providing a maximum numerical date for Stagonolepis-bearing units. This date must be late Carnian, not of Ladinian age, and thus supports the apparent age of the Ladinian-Carnian boundary (232 Ma) of time scales based on the Newark Supergroup in eastern North America.

Re-examination of the dentitions of carpolestid plesiadapiform mammals from the late Paleocene Swan Hills locality, northern Alberta, and correlative localities in the vicinity of Roche Percée, southeastern Saskatchewan, Canada, indicates that Carpodaptes cygneus (Russell) as known from these sites is polyphyletic: the name C. cygneus is here restricted to the Swan Hills carpolestid, while the Roche Percée form represents a new, more derived species, Carpodaptes stonleyi. Other purported records of C. cygneus are reconsidered as well: C. cygneus from DW-1, central Alberta, is more appropriately dubbed C. cf. cygneus; C. cygneus at Canyon Ski Quarry, central Alberta, is best identified as C. cf. stonleyi, while C. cf. cygneus from Police Point, southeastern Alberta, has closest affinities to C. hazelae Simpson. Carpolestids from the Tongue River Formation, North Dakota, are referred to Carpodaptes cf. hobackensis Dorr and C. cf. hazelae. After a review of the available evidence, the recent hypothesis that C. cygneus and other North American carpolestids are congeneric with Carpocristes oriens Beard and Wang from the Paleocene or Eocene of China, is rejected.

The ichnogenus Pholeus Fiege, 1944, is a common constituent of the Lower Muschelkalk (Middle Triassic) carbonates of the Germanic Basin, where it occurs in the upper part of shallowing upward cycles. It is restricted to a marly limestone lithofacies and is commonly associated with omission and erosion surfaces. The dwelling structures (domichnia) were created in a shallow-marine to lagoonal paleoenvironment in an intertidal to shallow subtidal setting. New material from Thuringia and Lower Saxony makes a re-evaluation of Pholeus possible and confirms the validity of this ichnogenus. Certain features, such as general form, wall, lining, and branching differentiate it from similar trace fossils. In addition to the already described P. abomasoformis, three new ichnospecies are named for distinctive forms: P. bifurcatus, P. platiformis, and P. elongatus. Based on geometry, size, and wall lining, the burrow producers were most probably decapod crustaceans. Many similarities to modern burrows of Callianassa sp., Neocallichirus grandimina, and Nephrops norvegicus suggest thalassinian shrimps and lobsters as likely tracemakers of Pholeus burrows. Compound burrow systems and retrusive burrow parts with spreiten-like structures are common and point to an upward shifting of the burrows related to certain sediment input in relation to tidal currents.

Psilonichnus lutimuratus n. ichnosp. is described from a Pliocene estuarine-mouth depositional environment (Skolithos ichnofacies) of the Olympic Peninsula, Washington, U.S.A. These simple Y-, I-, and J-shaped, mud-lined burrows occur in situ as dense patches within alternating, wavy-bedded sandstone and mudstone in a storm and flood influenced coastal sequence from an active tectonic margin. The I- and J-shaped traces represent erosional modification of burrow tops during storm-flood events. The new ichnospecies differs from the two other Psilonichnus ichnospecies by the distinct mud-lining of the burrow wall. Comparison with living thalassinoidean shrimp burrows and shrimp ecology allow this new ichnospecies to be attributed to the extant mud shrimp Upogebia. Biological and behavioral characteristics of this living shrimp restrict it to the mouth of the open estuary, and these parameters can be used to narrowly define a shoreline environment in the stratigraphic record.