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Species of the Ordovician acritarch genus Dicrodiacrodium, with a single apical process, are evaluated critically, based on a review of published literature and new studies on material from Belgium, Bohemia, China, Germany, and Morocco. Investigations of large populations of such species show a wide variability between specimens. Biometric studies, including measurements on type area material, show that the subdivision into varieties and even into species is not justified. There is a complete gradation between all of the prescribed taxa. which are impossible to distinguish.

• Read more about Variability in the Ordovician acritarch Dicrodiacrodium

In sphaeroidal enrolment, the exoskeleton formed a closed capsule. Well known in post-Cambrian trilobites, many Cambrian species, in addition to Agnostina and eodiscoids, also enrolled in this manner. Characteristic features of such forms (other than Agnostina and eodiscoids) are: a fulcrate thorax; the fulcrum relatively close to the axis; the facets of the anterior segments large and backwardly directed; more posterior facets smaller, steeper, and less so directed.

• Read more about Sphaeroidal enrolment and thoracic characters in Beltella depressa and other olenid trilobites

A new alligatorine eusuchian, Stangerochampsa mccabei gen. et sp. nov., is described on the basis of a partial skeleton from the Horseshoe Canyon Formation (Early Maastrichtian) of southern Alberta. It is unique in possessing an ectopterygoid/palatine contact, a ventrolateral process of the quadrate, a groove-like recess for nerves and blood vessels in the upper jaw, a rectangular palatine with a lateral process at its midpoint, and a basioccipital with a ventral exposure longer than that of the pterygoid. Several derived characters indicate a close relationship of S.

• Read more about A new alligator from the Upper Cretaceous of Canada and the relationships of early eusuchians

The enigmatic Upper Triassic reptile, Pachystropheus rhaeticus, displays characters suggestive of choristoderan affinity and, as such, is potentially the oldest known choristoderan reptile. Examination of the blown skeletal elements indicates that the choristoderan lineage remained morphologically conservative throughout its recorded history.

• Read more about The diapsid reptile, Pachystropheus rhaeticus, a probable choristodere from the Rhaetian of Europe

The holotype and only skull of Deltacephalus whitei from the Lower Triassic of Madagascar, is redescribed and reconstructed. D. whitei shares several morphological features with Lydekkerina huxleyi and Limnoiketes paludinatans and is argued to be a member of the family Lydekkerinidae. Derived characters distinguishing the Lydekkerinidae from other rhinesuchoid temnospondyls are given, and the genus Deltacephalus is diagnosed within the family.

• Read more about The skull of Deltacephalus whitei, a lydekkerinid temnospondyl amphibian from the Lower Triassic of Madagascar

An unusual specimen of Youngina is described from a new locality in the Karoo Basin of South Africa. The locality is in the Tropidostoma Assemblage Zone (equivalent to the former Lower Cistecephalus Zone), making the specimen the oldest recorded example of this genus. It comprises an association of five immature skeletons which are fully articulated and thus provide the first clear indication of body proportions in Youngina. In addition, the material yields new information on the pectoral girdle, pelvis and foot.

• Read more about New material of Youngina: evidence of juvenile aggregation in Permian diapsid reptiles

Armoured fossil jawless fishes, or 'ostracoderms', have long been regarded as being ancestral to Recent hagfishes and lampreys. The latter were supposed to have lost the mineralised exoskeleton and undergone a 'degeneracy' linked with their burrowing or ecloparasitic modes of life. However, recent cladistic analyses suggest that most, if not all 'ostracoderms' are more closely related to jawed vertebrates than to either lampreys or hagfishes, although they are clearly jawless.

• Read more about The dawn of the vertebrates: characters versus common ascent in the rise of current vertebrate phylogenies [Palaeontological Association 1995 annual address]

Two unusual new genera and species of acanthodian fishes are described from the Lower Devonian of the Mackenzie Mountains, Northwest Territories, Canada. Kathemacanthus rosulentus gen. et sp. nov. is a deep-bodied species that lacks a dermal shoulder girdle, but has a pectoral 'collar' or 'necklace' of large spines and enlarged scales, positioned in series with a large pectoral fin and spine inserted high on the animal's flank. K. rosulentus is assigned to the new monotypic family Kathemacanthidae.

• Read more about Early Devonian acanthodians from northern Canada

Normal growth patterns and structure of one species of dendroid, Dictyonema pentlandica, from the North Esk Inlier, Pentland Hills, Lothian, UK, are described and considered to be the result of the secretory zooids adhering to a strict and characteristic growth pattern. Aberrant and abnormal structures include: stipe truncation and compensatory growth by neighbouring stipes; changes in growth pattern; abnormal bursts of growth; tearing or splitting; and abnormal thecal growth.

• Read more about Implications of normal and abnormal growth structures in a Scottish Silurian dendroid graptolite

It is widely held that during the Permian, especially the Late Permian, the Subangara flora spread southwards into China, where it mingled with the 'Cathaysian flora'. However, the reputedly Angaran or Subangaran elements found in North China, which are common in, or even characteristic of the Psygmophyllum Zone of that region, include gymnosperms such as callipterids, peltasperms and psygmophylloids, which are in fact Euramerican in origin.

• Read more about Past global floristic changes: the Permian Great Eurasian Floral Interchange