New material of the pareiasaur Deltavjatia rossicus from the Kotel'nich locality, Kirov Province, Russia, is described in detail. The taxon is characterised by a distinctive pattern of dermal sculpture and the exaggerated embayment of the posterior skull roof, resulting in the dorsal exposure of the braincase. Postcranially, Deltavjatia shares some aspects of its morphology with basal pareiasaurs, including the osteoderm pattern. Features such as the forward-slanting and pointed iliac blade are shared with stratigraphically younger, more derived forms. Well-preserved material of the taxon spans a wide size-range, allowing an assessment of ontogenetic trends. A geometric morphometric analysis of the skull roof of Deltavjatia reveals an allometric increase in snout length and postorbital area, a result that can serve as a basis for examining morphological trends within pareiasaurs. A reassessment of pareiasauromorph relationships, using both parsimony and Bayesian methods of phylogenetic inference, recovers similar topologies in both cases. Four Bayesian analyses were completed, with and without a gamma-shaped parameter and with and without the inclusion of autapomorphies. Despite differing taxon and outgroup selection, the recovered topologies are similar to previous phylogenies of pareiasaurian relationships, with Deltavjatia appearing as a relatively basal taxon.

New fossil vertebrate microremains from the Lower Silurian of NW Mongolia, Tuva and S Siberia have been discovered, and previous collections of thelodonts (Vertebrata: Thelodonti) from this region re-studied, figured and described, following recent advances in morphology and systematics of thelodont scales. As a result, six thelodont species are described here and attributed to two families and three genera. An emended diagnosis is given for each species. Morpohological scale varieties of each species are revised, and the squamation types are introduced to the species descriptions, resulting in newly grouped morphological sets of scales. The previously monotypic genus Talimaalepis Žigaitė, 2004, is proposed to contain two different species; therefore, two new combinations of morphological scale sets of two species are described for the first time. Both of them show transitional scale structure between the genera Loganellia (family Loganellidae) and Helenolepis (family Phlebolepididae). Two of the thelodont genera, Angaralepis and Talimaalepis, as well as all the six species, are endemic and not known anywhere else in the world. They are accompanied by a variety of other peculiar early vertebrates, such as mongolepids, two endemic genera of acanthodians, and putative galeaspids. This work enhances our knowledge of early Silurian vertebrate diversity, and provides evidence of regional palaeoenvironmental conditions and palaeogeographical relationships of the Siberia and Tuva terranes.

The morphologies of the hyobranchial apparatus in early tetrapods are reviewed, based primarily on first-hand examination and supplemented by published descriptions. The basic arrangement of the “aquatic” hyobranchium, with four pairs of branchial arches and internal gills, was conserved to a remarkable degree across the fish–to–tetrapod transition and was retained in further evolution in adults of several tetrapod lineages. Thus, a fish-like hyobranchium in basal tetrapods does not necessarily represent a larval or paedomorphic character, respectively, as was often suggested in analogy to extant salamanders. Rather, it represents the plesiomorphic state of the adult hyobranchium in tetrapods. The changes in the hyobranchium during the fish–to–tetrapod transition include the reduction of the number of skeletal elements and their morphological simplification. In all three presently discussed scenarios of lissamphibian origin, the temnospondyl, lepospondyl and diphyly hypotheses, the internal gills were reduced independently within temnospondyls and on the amniote stem below seymouriamorphs. Evidence of remodelling into a true “terrestrial” hyobranchium, with reduction of the posterior branchial arches and modification to support terrestrial tongue feeding, is scarce in early tetrapods. It evolved within temnospondyls in zatracheids, amphibamids and lissamphibians, as well as once or several times in early amniotes or in their immediate stem-forms.

A revision of the Carboniferous lungfish genus Ctenodus is undertaken. Ctenodus is the longest-surviving genus of lungfish from the Carboniferous, and is the only one to cross the Lower–Upper Carboniferous boundary. Five species span the period, with species correlated to stage. Species are distinguished by differences in tooth plate morphology. Ridge number increases from the Tournaisian to the Moscovian, and the length to width ratio decreases. A new, almost complete articulated individual of C. interruptus allows identification of this species from pterygoid tooth plates and other characteristics. These, and new features of the postcranial skeleton, are described for the first time. Ctenodus retains primitive features of the skull roof, such as a pair of C-bones and retention of a D-bone; its contemporaries Conchopoma, Sagenodus and Straitonia show the derived condition of these features. Ctenodus retains primitive features of the lepidotrichia, which are distally segmented and bifurcated. However, it also shows the derived condition of the tail region in having a combined first and second dorsal fin: whether there was a separate caudal fin remains unknown.

The twin summits of Preshal More and Preshal Beg, near Talisker, Isle of Skye, comprise the erosional remnants of a thick (at least 120 m) compound olivine tholeiite lava, or flow field, that ponded in palaeo-valleys within the Palaeocene lava field of west-central Skye. This unique flow field constitutes the Talisker Formation and is the youngest preserved extrusive unit of the Skye Lava Field. The lava inundated a complex of palaeo-valleys incised into the higher stratigraphical levels of the existing lava field, and remnants of the original sedimentary fill of these valleys still exist, the Preshal Beg Conglomerate Formation. The lava displays spectacularly well-developed two-tier (colonnade-entablature) columnar joint sets that formed as a consequence of slow, uninterrupted cooling through its base and sidewalls, aided by groundwater circulation and water ingress (from displaced drainage) directed into the lava's interior by master-joint systems. Intrusive phenomena developed at both the base and the top of the lava and there is evidence for the existence of subsurface feeder tubes. The tholeiitic composition of the Talisker Formation lava contrasts with the transitional, mildly alkaline characteristics of the remainder of the (older) lavas of Skye Lava Field. In broad terms, the Talisker Formation lava is compositionally very similar to the suite of cone-sheets emplaced into the oldest of the four intrusive centres that comprise the Skye Central Complex – the Cuillin Intrusive Centre – together with a high proportion of the Skye regional dyke swarm. The stratigraphical position, field relationships and compositional characteristics of the lava indicate that it was erupted and emplaced as an intracanyon-style flow field during the early shield-building stage in the growth of the (tholeiitic) Cuillin Volcano, which post-dates the main Skye ‘plateau’ Lava Field. Although the remnant outcrops are detached from their likely source area through erosion, this tholeiitic lava provides the first direct evidence linking the central complexes of the British Palaeogene Igneous Province and their eruptive products.