A new species, Mesolepis arabellae, is described from material recently recovered from the shales of the Scottish Lower Coal Measure Formation. Up until now, three British species of Mesolepis have been named: Mesolepis scalaris Young, Mesolepis wardi Young, and Mesolepis micropterus Traquair. A fourth member of the genus, Mesolepis pustulosa Pruvost from the coalfields of Northern France, was named on scale description alone, though the validity of this taxon is uncertain. The new material described here varies from other Mesolepis species in its caudal peduncle morphology and overall body shape. Micro-computed tomography of the new species reveals the presence of teeth on the premaxilla and dentary and a splint-like fused prearticular and coronoid element, with implications for a possible feeding behaviour of Mesolepis. Additional information on the homogeneous Mesolepis wardi is also presented.

The holotypic isolated maxilla of the early sphenacodontian Haptodus grandis from the Cisuralian of England is revisited. A unique character combination includes haptodontine-grade traits like less specialised teeth and a high number of precanines, but at the same time a shortened lacrimal that is separated from the naris, which is strongly diagnostic of Sphenacodontoidea. As the specimen cannot be assigned to any known taxon, the new taxon Hypselohaptodus grandis gen. nov. is proposed. Comparison with other sphenacodontians reveals a mosaic distribution of maxillary features, most significantly regarding the precanine region. Preliminary character histories preclude Hypselohaptodus from Sphenacodontidae, but suggest a haptodontine-grade or basal therapsid position. The latter hypothesis is substantiated by an ecological model of episodic wet phases in an overall trend of aridification throughout the Permian, to explain the rareness of non-sphenacodontid sphenacodontians in the fossil record. Also from the early Permian of England, an isolated dentary has previously been assigned to Ophiacodon, but can be shown to be either a sphenacodontian, possibly affiliated with Hypselohaptodus, or a robust, Stereorhachis-like ophiacodontid. The absence of Ophiacodon in the intramontaneous Permian basis of Europe is explained by a narrow environmental tolerance range requiring limnic connection with lowland basins.

A pycnodont premaxilla bearing a large incisiform tooth with an unusual crown morphology is described from the Palaeocene (Thanetian) phosphate deposits of Morocco. This peculiar tooth shows a broad, fan-shaped multicuspid crown with nine cusps, well adapted for benthic macroalgal scraping. This morph, assigned to a new species of Pycnodus (P. multicuspidatus sp. nov.), emphasizes the phenotypic plasticity of the group and documents an additional trophic specialization among Palaeogene pycnodontiform fishes. In the post-K/Pg boundary marine ecosystem of the Ouled Abdoun Basin, P. multicuspidatus sp. nov. may have opportunistically replaced Maastrichtian fish taxa with a similar front dentition and feeding behaviour, such as the putative specialized pycnodontiforms Stephanodus and Hadrodus.

In a cross-sectional study, data from records of cattle slaughtered over a 1-year period at a large abattoir in South West England were analysed using an ordered category response model to investigate the inter-relationships between age, sex and breed on development of the permanent anterior (PA) teeth. Using the model, transition points at which there was a 50% probability of membership of each category of paired PA teeth were identified. Data from ∼60 000 animals were initially analysed for age and sex effect. The age transition was found to be ∼23 months moving from zero to two teeth; 30 months for two to four teeth; 37 months for four to six teeth and 42 months for six to eight teeth. Males were found to develop, on average, ∼22 days earlier than females across all stages. A reduced data set of ∼23 000 animals registered as pure-bred only was used to compare breed and type interactions and to investigate sex effects within the sub-categories. Breeds were grouped into dairy and beef-type and beef breeds split into native and continental. It was found that dairy-types moved through the transition points earlier than beef-types across all stages (interval varying between ∼8 and 12 weeks) and that collectively, native beef breeds moved through the transition points by up to 3 weeks earlier than the continental beef breeds. Interestingly, in contrast to beef animals, dairy females matured before dairy males. However, the magnitude of the difference between dairy females and males diminished at the later stages of development. Differences were found between breeds. Across the first three stages, Ayrshires and Guernseys developed between 3 and 6 weeks later than Friesian/Holsteins and Simmental, Limousin and Blonde Aquitaine 6 and 8 weeks later than Aberdeen Angus. Herefords, Charolais and South Devon developed later but by a smaller interval and Red Devon and Galloway showed the largest individual effect with transition delayed by 8 to 12 weeks.

The morphology of the amphibamid temnospondyl amphibian Platyrhinops lyelli from the Middle Pennsylvanian of Linton, Ohio is reassessed from previously described and undescribed specimens. Newly reported or newly significant features include the presence of bicuspid marginal teeth, anteriorly widened frontals, elongate choanae, a broad rhomboidal sphenethmoid and a pair of flattened blade-like ceratohyals. One specimen shows an unusual distribution of tooth sizes along the premaxillaries. No derived characters can be found to justify reference of the species lyelli to the genus Amphibamus as represented by its type species A. grandiceps, but Platyrhinops does belong to the ‘Amphibamus branch’ of the Amphibamidae.

The fossil group Placodermi is the most phylogenetically basal of the clade of jawed vertebrates but lacks a marginal dentition comparable to that of the dentate Chondrichthyes, Acanthodii and Osteichthyes (crown-group Gnathostomata). The teeth of crown-group gnathostomes are part of an ordered dentition replaced from, and patterned by, a dental lamina, exemplified by the elasmobranch model. A dentition recognised by these criteria has been previously judged absent in placoderms, based on structural evidence such as absence of tooth whorls and typical vertebrate dentine.

However, evidence for regulated tooth addition in a precise spatiotemporal order can be observed in placoderms, but significantly, only within the group Arthrodira. In these fossils, as in other jawed vertebrates with statodont, non-replacing dentitions, new teeth are added at the ends of rows below the bite, but in line with biting edges of the dentition. The pattern is different on each gnathal bone and probably arises from single odontogenic primordia on each, but tooth rows are arranged in a distinctive placoderm pattern. New teeth are made of regular dentine comparable to that of crown-gnathostomes, formed from a pulp cavity. This differs from semidentine previously described for placoderm gnathalia, a type present in the external dermal tubercles.

The Arthrodira is a derived taxon within the Placodermi, hence origin of teeth in placoderms occurs late in the phylogeny and teeth are convergently derived, relative to those of other jawed vertebrates. More basal placoderm taxa adopted other strategies for providing biting surfaces and these vary substantially, but include addition of denticles to the growing gnathal plates, at the margins of pre-existing denticle patches. These alternative strategies and apparent absence of regular dentine have led to previous interpretations that teeth were entirely absent from the placoderm dentition. A consensus view emerged that a dentition, as developed within a dental lamina, is a synapomorphy characterising the clade of crown-group gnathostomes.

Recent comparisons between sets of denticle whorls in the pharyngeal region of the jawless fish Loganellia scotica (Thelodonti) and those in sharks suggest homology of these denticle sets on gill arches. Although the placoderm pharyngeal region appears to lack denticles (placoderm gill arches are poorly known), the posterior wall of the pharyngeal cavity, formed by a bony flange termed the postbranchial lamina, is covered in rows of patterned denticle arrays. These arrays differ significantly, both in morphology and arrangement, from those of the denticles located externally on the head and trunkshield plates. Denticles in these arrays are homologous to denticles associated with the gill arches in other crown-gnathostomes, with pattern similarities for order and position of pharyngeal denticles. From their location in the pharynx these are inferred to be under the influence of a cell lineage from endoderm, rather than ectoderm. Tooth sets and tooth whorls in crown-group gnathostomes are suggested to derive from the pharyngeal denticle whorls, at least in sharks, with the patterning mechanisms co-opted to the oral cavity. A comparable co-option is suggested for the Placodermi.

Patterns of morphological variation in the skulls of extant bears were studied as they relate to diet and feeding behaviour. Measurements of craniodental features were used to compute indices that reflect dietary adaptations of the dentition and biomechanical properties of the skull, jaw and related musculature. Species were classified as either carnivores, omnivores, herbivores or insectivores. Differences among dietary groups were assessed with analysis of variance and discriminant factor analysis. Results demonstrated significant morphological separation among all four groups. Carnivores were distinguished by, among other features, molar size reduction, flexible mandibles and, most surprisingly, relatively small carnassial blades. In contrast, herbivores displayed, among other features, large molar grinding areas, rigid mandibles and large carnassial blades. The insectivorous sloth bear was characterized by extreme reduction of the post-canine teeth. As expected, omnivores tended to have morphology intermediate between that of carnivorous and herbivorous ursids. Comparison with previous studies revealed that bears exhibit a different set of morphological specializations for diet than other carnivoran groups. Carnivorous ursids, for example, were found to share aspects of craniodental morphology with omnivorous canids. The relatively weak adaptations for carnivory observed in bears may be the result of selection for the ability to cope with temporal fluctuations in dietary components. The giant panda Ailuropoda melanoleuca was found to have a relatively stiff jaw and great mechanical advantage of the jaw-closing muscles, features previously observed in carnivorous canids and unexpected in this herbivorous bear. Comparison of patterns of morphological variation and patterns of phylogenetic relationships among species revealed surprisingly strong congruence between morphology and phylogenetics.

In ungulates, a set of deciduous teeth is replaced by a set of permanent teeth during their first 2 years of life. Little is known about factors causing variation in timing of tooth eruption, but overall size, condition or mineral deficiencies may play a role. The pattern of incisor (I) and canine (C) eruption was investigated in 2241 yearlings from five populations of red deer Cervus elaphus in Norway during 1964–2001. Before the sampling period (10 September–15 November), I1 had erupted in most yearlings (97%), while eruption of I3 and C had barely started (erupted in 7% and 5% of individuals, respectively). Exactly 50% of the yearlings had erupted I2. Jawbone length was shown to be a main determining factor for eruption of I2. However, for a given jawbone length, there was large variation among populations in the proportion of yearlings with erupted I2 (from <20% to >75%). Females got their permanent I2 earlier than males. Tooth eruption was found to be later with increasing local deer density, even after correcting for body weight. There was a residual effect of body weight (a measure of condition) after body size (measured as jawbone length) was controlled for in one of five populations, indicating that overall condition may influence timing of tooth eruption in this area. There was no evidence that calcium was limiting for eruption, as no correlation was found between timing of eruption and limestone in bedrock. Since there is large variation in timing of tooth eruption among red deer populations even after controlling for differences in phenotype and environmental factors, genotypic variation may also play an important role for tooth eruption patterns.

The dental morphology of the pycnodontid fish †Stemmatodus rhombus (Agassiz, 1844) from the Lower Cretaceous (lower Barremian) of southern Italy is described in detail. SEM pictures of vomerine and prearticular teeth are provided for the first time allowing the comparison with other Early Cretaceous pycnodonts, which are only known from isolated dental remains. The dentition of †Stemmatodus rhombus consists of incisiform grasping teeth on the paired premaxillae and dentaries and crushing teeth on the unpaired vomer and paired prearticulars. The vomerine teeth are arranged in five longitudinal rows, which display symmetry with a distinct median principal and two lateral rows. The prearticular bears three longitudinal rows. Teeth of the main row are much wider than those of the lateral ones. The tooth crowns are rather flat and expose a shallow apical depression, which is surrounded by a ring of widely-spaced small tubercles. The ornamentation and arrangement of teeth distinguishes dentitions of †Stemmatodus from all other pycnodonts. The wear pattern of the teeth is evaluated and the significance of the dental morphology in pycnodont taxonomy is discussed. In addition, the systematic position of †Stemmatodus is discussed.

The Rhizodontida (Pisces: Sarcopterygii) is a clade of predatory fishes from the Upper Devonian (Aztecia; ?Givetian of Antarctica) through to the Upper Carboniferous (Strepsodus; Moscovian of northern Europe and North America). They form the most basal plesion within the tetrapod stem-lineage. The mandibles were dominated by large symphysial tusks on the dentary. Not much else is known of the mandibles in primitive rhizodontids. However, later forms show several derived characters: the mandible is very deep dorsoventrally and narrow linguolabially; the coronoid fangs bear only a single fang and no other dentition; the Meckelian element was unossified, leaving the adductor fossa unfloored by bone; the prearticular produced a large dorsal process lingual to the adductor fossa, presumably for muscle attachment. These and other characters are discussed in the context of the evolution of the tetrapod stem-group.

The mandible appears to have been split into two functional units, one comprising the firmly sutured prearticular, coronoids and dentary, the other comprising the firmly sutured infradentaries. The connection between the two units was weak, suggesting a longitudinal intramandibular hinge. The possibility that this acted as a ‘torsion grip’ during feeding is discussed.

The extant lungfish, including three genera, the Australian, South American and African lungfishes, retain a dentition that appeared first in the Devonian, in some of the oldest members of this group. The dentition consists of permanent tooth plates with persistent cusps that appear early in development of the fish. The cusps, separate early in development, form ridges that are arranged in a radiating pattern, and fusion of the cusps to each other and to the underlying jaw bone produces a tooth plate. The lungfish dentition is based on a template of mantle dentine that surrounds bone trabeculae enclosed in the tooth plate. The mantle layer is covered by enamel. In most derived dipnoans, this framework encloses two further forms of dentine, known as interdenteonal and circumdenteonal dentines. The tooth plates grow in area and in depth without evidence of macroscopic resorption of dentines or of enamel. Increase in size and changes in shape of lungfish tooth plates is actually achieved by a process involving microscopic remodelling of the bone contained within the margin of each tooth plate, and the later addition of new dentines and enamel within and around the bone. This is accomplished without creating weakness in the structural integrity of the tooth plate and bone complex, and proceeds in line with growth and remodelling of the jaw bones attached to the tooth plates.

Although the 3 genera of living lungfish have different-shaped adult tooth plates, their larval stages have similar patterns of development. The sequence in the pattern of initiation of teeth and their modification through ontogeny in Neoceratodus hatchlings provides a developmental model for fossil hatchling tooth plates (smallest 1–2 mm) recovered as 3-dimensional dentitions from Andreyevichthys. This Late Devonian lungfish demonstrates that these also have a similar dentition pattern and suggests strongly conserved developmental processes. We postulate that a specific pattern of development, derived within lungfish, has been conserved in extant forms through evolution from the earliest known lungfish. The most basal early dipnoan, Diabolepis speratus, is also known from juveniles with tooth plates formed in this pattern.

The lungfish pattern is in marked contrast to the typical linear rows of teeth with lingual replacement for each tooth position, characteristic of most osteichthyan and chondrichthyan dentitions. Uniquely for lungfish, teeth are only added to the lateral ends of the radial rows in the palatal and lingual dentition and are consolidated into dental plates without loss through shedding. It is proposed that this tooth pattern is set up from primordial teeth at the patterning stage of the dentition, one in each dentate region of the larval jaws. Although in post-Devonian lungfish marginal dentate bones are absent in the adult, in both the fossil and extant hatchling, teeth are present and function on some of the marginal bones. This pattern of development and loss is described and we conclude that in both forms it is also based on a radial pattern of successive tooth initiation. We propose that this ontogenetic pattern constrained the phylogenetic pattern of adult form, through evolution of dipnoan dentitions from 360 MYBP until the present. The universality amongst dipnoans and the implications for such a conserved constraint in the developmental module for the dentition is discussed.

We rely on fossils for the interpretation of more than 95% of our evolutionary history. Fieldwork resulting in the recovery of fresh fossil evidence is an important component of reconstructing human evolutionary history, but advances can also be made by extracting additional evidence for the existing fossil record, and by improving the methods used to interpret the fossil evidence. This review shows how information from imaging and dental microstructure has contributed to improving our understanding of the hominin fossil record. It also surveys recent advances in the use of the fossil record for phylogenetic inference.

Ninety-six Border Leicester × Scottish Blackface ewes, aged 2 to 6 years, grazed perennial ryegrass pastures during lactation. The state of their incisor teeth was assessed at parturition on a scale from score 1 (sound teeth) to score 4 (poor teeth). Their live weights and condition scores during lactation were then related to incisor score and age by regression analysis. Lamb growth was similarly analysed. Herbage intakes and milk production were measured in a subset of 24 ewes.

Ewe live weights were significantly lower, per unit incisor score, by 2·2, 2·5 and 2·1 kg at days 22, 50 and 96 of lactation respectively. In ewes with twin lambs, the equivalent reductions were 1·6, 2·8 and 2·1 kg respectively. Reductions in condition score, whilst still significant, were less marked. After adjusting for the effects of incisor dentition, there was no effect of age on ewe live weight or condition score.

Incisor dentition did not markedly affect herbage intake or milk production, except in measurements at day 53 of lactation, where higher incisor scores resulted in significant reductions in the production of milk and its components. Effects on lamb performance were confined to twins, where live-weight gain to day 50 was reduced by 12·2 g/day, per unit increase in ewe incisor score. This resulted in reductions of 0·7 kg (day 50) and 0·9 kg (weaning) in the live weight of twin lambs.