Vertebrate fossils have been converted from natural history objects into research specimens through the act of preparation for over 200 years. All of the basic techniques applied to specimens in the 21st Century were already in use in palaeontological laboratories by the first decade of the 1900s. It behoves any worker in the field to be intimately familiar with processes for treatment of specimens, as these procedures almost always permanently alter material available for interpretation. Historic treatments also complicate attempts to re-treat or re-prepare specimens. Sometimes this results in damage to fossils and loss of information, and often in wasted resources. Most palaeontologists are unaware of the historical evolution of laboratory methods through this time; much of the documentation of this process is considered to be obscure. However, there is in fact a robust body of literature that chronicles the development of procedures for the preparation of fossils. Awareness of the past development of methods is crucial to guiding future directions in the palaeontological laboratory. Regular reporting of laboratory methods in the technical literature at a pace matching that of other analytical methods is integral to the function of palaeontology as a science.

The Briar Creek Bonebed (Artinskian, Nocona Formation) in Archer County is one of the richest sources of Dimetrodon bones in the Lower Permian of Texas, USA. Based on size, a small (D. natalis), an intermediate (D. booneorum), and a large species (D. limbatus) have been described from this locality. It has been proposed that these traditionally recognised species represent an ontogenetic series of only one species. However, the ontogenetic series hypothesis is inconsistent with the late ontogenetic state of the small bones, as suggested by their osteology and degree of ossification. Histological analysis of newly excavated material from the Briar Creek Bonebed has resolved some of the discretion between these two competing hypothesis, confirming the coexistence of a small (D. natalis) with at least one larger Dimetrodon species. An external fundamental system is present in the largest sampled long bones identified as D. natalis. The histology of D. natalis postcrania is described as incipient fibro lamellar bone. This tissue is a combination of parallel-fibred and woven-fibred bone that is highly vascularised by incipient primary osteons. The species status of D. booneorum and D. limbatus remain unresolved.

Osteohistological characteristics of the large temnospondyl amphibian Metoposaurus diagnosticus from the Upper Triassic of Poland (Krasiejów locality) were determined using vertebral intercentra thin-sections from different regions and growth stages. The intercentra showed a trabecular structure in both the endochondral and periosteal domains. Endochondral ossification developed first, and the primary bone occurs near the periphery with a higher degree of remodelling in the centre. Periosteal bone deposition begins later; first on the ventral side, continuing laterally and finally onto the dorsal side. Periosteal growth rate was initially very rapid, and then subsequently decreased in rate. In all sections, numerous remains of calcified cartilage are visible, which may indicate a juvenile, paedomorphic or plesiomorphic character. The four histologic ontogenetic stages (HOS) of sampled vertebrae were determined based on growth marks. Most of the sampled bones belong to juvenile individuals (HOS 1 to 3), apart from one atlas and the largest anterior dorsal intercentrum, which represent the oldest described stage (HOS 4). Sharpey's fibres are preserved in ventro-lateral cortical regions, around parapophyses and on the posterior side of the neural arch.

The paraphyletic genus ‘Paleorhinus’ is understood currently as a cosmopolitan phytosaur taxon from the Late Triassic. There is no consensus regarding the number of species of ‘Paleorhinus,’ with multiple species and genera synonymised into a single genus or even a single species at various points in its published history. The taxonomy is confounded by historical descriptions without the benefit of comparisons to more recently collected specimens, emphasis on plesiomorphic cranial morphology as diagnostic features of the genus, and lack of cladistic analyses. When included in a recent explicitly cladistic phylogenetic analysis, the holotype of ‘Paleorhinus’ scurriensis (TTU P-00539) was found to be the earliest-branching phytosaur with respect to other North American specimens previously referred to ‘Paleorhinus,’ and is generically distinct from Paleorhinus. ‘Paleorhinus’ scurriensis differs from all known phytosaurs in five unambiguous characters: basitubera widely separated mediolaterally; ridge present on lateral surface of jugal; thickened shelf present along posteroventral edge of expanded pterygoid-quadrate wing; ‘septomaxillae’ separated and excluded from internarial septum; and nasal swelling present posterior to posterior borders of nares. This detailed morphological description of an early-branching phytosaur taxon is a first step towards resolving long-standing issues surrounding specific anatomical features and relationships among early members of the clade.

The genus Machaeroprosopus has long been considered invalid because the type specimen of the Late Triassic phytosaur species, M. validus, has been lost. Re-examination of the primary literature regarding the establishment of the Late Triassic phytosaur genus Machaeroprosopus demonstrates that M. buceros is the correct type species, not M. validus. Thus, the genus level name Machaeroprosopus has priority over the genera Pseudopalatus and Arribasuchus and all nominal species should be reassigned. Reassignment of these species to Machaeroprosopus satisfies the requirements of the International Code of Zoological Nomenclature (ICZN) and preserves historical context. The name Pseudopalatinae is retained as the valid clade name for these phytosaurs because its usage falls outside of the ICZN.

The skull anatomy of a new species of the phytosaur Machaeroprosopus is described for the first time on the basis of two specimens from the Upper Triassic Cooper Canyon Formation of Texas. Additional information is provided by a third specimen referred to Machaeroprosopus sp. A paranasal bone, an additional paired element of the narial region, is identified. Important new data are presented for the braincase, including the morphology of the epipterygoid and presphenoid, an anterior process of the prootic, an anteroventral process of the laterosphenoid, and a parasphenoid process. Machaeroprosopus lottorum n. sp. is characterised by four apomorphies: a supratemporal fenestra closed on the skull roof with bevelled anterior rim, a comparatively short squamosal, a flat and rugose narial rim, and medially extended palatines that come close to form an ossified secondary palate. With respect to the supratemporal fenestra, the supraoccipital–parietal complex and several features of the squamosal, Machaeroprosopus lottorum n. sp. bridges the morphological gap between species previously referred to the genera Pseudopalatus and Redondasaurus. A parsimony analysis of known species of Machaeroprosopus supports the hypothesis that the development of the rostral crest in Machaeroprosopus is a sexually dimorphic feature, and questions the validity of the genus Redondasaurus. Consequently, Redondasaurus is here considered a junior synonym of Machaeroprosopus.

Historic type and referred material of the aetosaurian taxa Typothorax coccinarum, Episcoposaurus horridus and Episcoposaurus haplocerus are redescribed and the non-aetosaurian material identified and removed, a task previously considered “hopeless”. Reexamination of the original material reveals that the holotypes of E. haplocerus and probably T. coccinarum are not diagnosable at the species level and therefore are nomena dubia. The next available names for material referred to these taxa are Desmatosuchus spurensis and E. horridus respectively, although it may be more desirable for reasons of taxonomic stability to attempt to petition for a neotype in the latter case. The redescription of historical specimens is necessary to determine their nomenclatural validity. The use of referred specimens as proxy “type” specimens is problematic, as these referrals were originally made not on the basis of apomorphies, but rather on biostratigraphic and/or geographical assumptions which are inherently circular and cannot be unambiguously supported.

The Post Quarry, within the lower part of the type section of the Upper Triassic Cooper Canyon Formation in southern Garza County, western Texas, contains a remarkably diverse vertebrate assemblage. The Post Quarry has produced: the small temnospondyl Rileymillerus cosgriffi; the metoposaurid Apachesaurus gregorii; possible dicynodonts and eucynodonts; a clevosaurid sphenodontian; non-archosauriform archosauromorphs (Trilophosaurus dornorum, simiosaurians, and possibly Malerisaurus); the phytosaur Leptosuchus; several aetosaurs (Calyptosuchus wellesi, Typothorax coccinarum, Paratypothorax, and Desmatosuchus smalli); the poposauroid Shuvosaurus inexpectatus (“Chatterjeea elegans”); the rauisuchid Postosuchus kirkpatricki; an early crocodylomorph; several dinosauromorphs (the lagerpetid Dromomeron gregorii, the silesaurid Technosaurus smalli, a herrerasaurid, and an early neotheropod); and several enigmatic small diapsids. Revised lithostratigraphic correlations of the lower Cooper Canyon Formation with the Tecovas Formation, the occurrence of Leptosuchus, and the overall composition of the assemblage indicate that the Post Quarry falls within the Adamanian biozone, and not the Revueltian biozone. Stratigraphic subdivision of the Adamanian biozone may be possible, and the Post Quarry may be correlative with the upper part of the Adamanian biozone in Arizona. The age of the Post Quarry assemblage is possibly late Lacian or earliest Alaunian (late early Norian or earliest middle Norian), between 220 and 215 Ma.

Ossified skeletal elements within the orbit, such as scleral ossicles, palpebrals, supraorbitals and sesamoids, are widespread across Reptilia, including extant members of Crocodylia, Aves, Squamata and Chelonia. Extant crocodylians lack scleral ossicles, but have a unique palpebral that has recently been shown, through developmental studies, to be an osteoderm in the upper eyelid. Here, we examine the diversity and disparity of the crocodylian palpebral in extant members of Crocodylia and, through the fossil record, trace the origin and evolutionary history of the element throughout Pseudosuchia (all archosaurs more closely related to crocodylians than avians). We show that the crocodylian palpebral originated outside of Crocodylomorpha in early pseudosuchian groups (e.g. Aetosauria, Loricata) and that scleral ossicles are lost in nearly all groups of pseudosuchians, but appear in poposauroids, at least one early crocodylomorph, and some partially or fully marine Crocodyliformes (e.g. thalattosuchians). The morphology and number of palpebrals differs across Crocodyliformes; the presence of two palpebrals is plesiomorphic, but this is reduced to one by Crocodylia. We further recommend the restriction of the term palpebral to the structure in crocodylians and their homologues, but not to the structure in ornithischian dinosaurs.

The state of Texas has one of the greatest records of pterosaurs in the world, surpassing all other US states and most countries in the number of occurrences. Uniquely, this record extends over the entire 150+ million history of the Pterosauria. A review of this pterosaur record confirms at least 30 pterosaurs known from 13 occurrences, including five valid species. The holotypes of two of these species have been described before and are diagnosed and erected here as the new species Radiodactylus langstoni, gen. et sp. nov., named in honour of Dr. Wann Langston Jr, the father of Texas pterosaurology, and Alamodactylus byrdi, gen. et sp. nov.. Phylogenetic analysis of all Texas pterosaurs that can be coded for more than one character confirms that these species are distinct from others and occupy phylogenetic positions close to their original classifications. Radiodactylus langstoni is recovered as a non-azhdarchid azhdarchoid, Quetzalcoatlus northropi as an azhdarchid, Alamodactylus byrdi as a non-pteranodontoid pteranodontian, Aetodactylus as a pteranodontoid, and Coloborhynchus wadleighi as an ornithocheirid. The presence of eudimorphodontid, dsungaripterid, as well as other azhdarchid and pteranodontoid pterosaurs, is also confirmed in Texas.

Records of flying Jurassic reptiles are very scarce in the Southern Hemisphere. Upper Jurassic pterosaurs have been discovered in marine Tithonian sediments of the Vaca Muerta Formation, in the Neuquén Basin, Patagonia, Argentina. Only four specimens are known so far: the first from Arroyo Picún Leufú, and the other three from the lithographic limestones of Los Catutos. Here, we update knowledge of Late Jurassic pterosaurs from northwest Patagonia. We revise the diagnosis and description of a previously described pterodactyloid, which is named as a new genus and species, Wenupteryx uzi. This small-sized pterosaur shows affinities with Euctenochasmatia or Archaeopterodactyloidea, and represents the most complete Jurassic pterosaur so far known from the Southern Hemisphere. We also report a recent finding suggesting that the new specimen belongs to a new species of pterodactyloid pterosaur. These records show that at least three different taxa of pterosaurs coexisted in the Neuquén Basin: Herbstosaurus, Wenupteryx and a more derived pterodactyloid that represents the largest pterosaur known from the Upper Jurassic of Gondwana.

A new unusual tapejarid pterosaur from the Early Cretaceous Romualdo Formation (Araripe Basin, Brazil) is described, based on a skull, lower jaw and some postcranial elements. Caupedactylus ybaka gen. et sp. shows the typical high nasoantorbital fenestra of the Thalassodrominae but lacks a palatal ridge, and shares with the Tapejarinae several features, including a downturned rostral end, allowing its allocation to that clade. Furthermore, the new species differs in having an anteriorly and posteriorly expanded premaxillary sagittal crest, the lacrimal process of the jugal strongly inclined, and a slit-like postpalatine fenestra, among other characters. The region of the left jugal-quadratojugal-quadrate shows a pathology that is likely the result of an infection. The lateral surface of the premaxillary crest presents grooves that were interpreted in other pterosaurs as impressions of blood vessels, corroborating growing evidence that cranial crests could have been involved in thermoregulation. Also, the new species has a well-preserved palate with a large palatine forming the anterior region of the choanae and the postpalatine fenestra and a secondary subtemporal fenestra. Since the latter has been regarded as unique to non-pterodactyloids, its occurrence in Caupedactylus demonstrates that the evolution of palatal region in pterosaurs is more complex than previously thought.

The problem of the origin of dinosaurs has historically had three dimensions. The first is the question of whether Dinosauria is monophyletic, and of its relationships to other archosaurs. This question was plagued from the beginning by a lack of relevant fossils, an historical burden of confusing taxonomic terms and a rudimentary approach to devising phylogenies. The second dimension concerns the functional and ecological adaptations that differentiated dinosaurs from other archosaurs, a question also marred by lack of phylogenetic clarity and testable biomechanical hypotheses. The third dimension comprises the stratigraphic timing of the origin of dinosaurian groups with respect to each other and to related groups, the question of its synchronicity among various geographic regions, and some of the associated paleoenvironmental circumstances. None of these dimensions alone answers the question of dinosaur origins, and they sometimes provide conflicting implications. Since Dinosauria was named, one or another set of questions has historically dominated academic discussion and research. Paradigms have shifted substantially in recent decades, and current evidence suggests that we are due for more such shifts. I suggest two changes in thinking about the beginning of the “Age of Dinosaurs”: first, the event that we call the (phylogenetic) origin of dinosaurs was trivial compared to the origin of Ornithodira; and second, the “Age of Dinosaurs” proper did not begin until the Jurassic. Re-framing our thinking on these issues will improve our understanding of clade dynamics, timing of macroevolutionary events, and the effects of Triassic climate change on terrestrial vertebrates.

A Late Jurassic sauropod bone-bed comprising thousands of individual skeletal elements in the Morrison Formation of Montana, USA, is re-analysed to further elucidate its taphonomic history. New data gained from detailed contextual sampling is assembled and presented to test the hypothesis of a drought-induced, mass-mortality assemblage, and its subsequent depositional emplacement by a debris flow. Large dinosaur bone-beds are well-known in the Morrison, yet the Mother's Day Quarry site is unique for the formation in depicting an apparent debris flow deposit. Use of a computer program tailored to the data allows three-dimensional reconstruction of the bone-bed and recreates the palaeoslope of the deposit, adding support to the debris flow hypothesis. Such digital manipulation of field data may allow a deeper understanding of other bone-bed origination events.

New sauropod dinosaur material is described from Jones Ranch, Early Cretaceous of Texas (USA). Originally described as Paluxysaurus jonesi, the material from Jones Ranch has recently been referred to Sauroposeidon proteles. Elements newly prepared from dense concretionary matrix include the sacrum, ilium and proximal portion of the tail. Reconstructions of the skull and sacrum plus pelvic girdles are presented. ‘Paluxysaurus jonesi’ (=S. proteles) is a blunt-faced sauropod that was originally regarded as closely related to Brachiosaurus. Portions of the sacrum are now exposed and show that it is nearly complete, missing only parts of the first sacral (S1). The anterior sacrals are firmly fused, however, a newly discovered opisthocoelous last sacral (S6) remains unfused. A complete sequence of proximal caudal vertebrae shows a rapid transition from anteroposteriorly short and mediolaterally broad centra anteriorly, to more elongate cylindrical centra posteriorly. All proximal caudals have slightly amphicoelous centra. Some middle anterior caudals have a shallow longitudinal groove on the ventral surface of the centrum. Specimens from Jones Ranch exhibit characters of the sacrum and tail that clearly corroborate placement of ‘P. jonesi’ (Sauroposeidon proteles) as a somphospondylan titanosauriform.

Rare remains of tyrannosauroid dinosaurs from the Aguja Formation in West Texas indicate the presence here of a relatively gracile species, comparable in form and adult size to Appalachiosaurus or subadult albertosaurines, Gorgosaurus and Albertosaurus. Histologic analysis of one of the specimens indicates that the Aguja tyrannosaur attained an adult size substantially smaller than adult albertosaurines (700 kg, 6·5 m body length). The frontal bone is narrow with a wide orbital slot and a bipartite joint for the postorbital, features thought to be diagnostic of Albertosaurinae; but there is a tall sagittal crest and reduced parietal wedge separating the frontals on the midline, features thought to be diagnostic of Tyrannosaurinae. The tall sagittal crest may be a synapomorphy of Tyrannosaurinae, and the Aguja tyrannosaur is herein referred to that clade. However, the unique combination of character states exhibited by the frontal prevents confident attribution to any known species. The Aguja tyrannosaur provides further evidence that North American Campanian tyrannosauroids were remarkably diverse for such large predators, and that each species was apparently endemic to a relatively small geographic province.

The centrosaurine ceratopsid taxon Pachyrhinosaurus is the most speciose of centrosaurines, being represented by at least three species (P. canadensis, P. lakustai, and the recently described P. perotorum) from the late Campanian and early Maastrichtian of North America. The species are readily distinguished from one another by details of easily visible cranio-facial and frill ornamentation, features commonly used to differentiate ceratopsid taxa. Braincase material is also known for all three taxa. We describe the braincase of P. perotorum based on specimens from the Kikak–Tegoseak Quarry of the North Slope of Alaska. We then compare it to braincase and endocranial descriptions of the other Pachyrhinosaurus taxa to test whether there may be useful species-level differences present in these robust parts of the ceratopsid skull. Braincase morphology, including cranial nerve paths through the braincase walls in P. lakustai and P. perotorum, were found to be very similar. Two potential diagnostic differences between taxa were found, although tests based on larger sample sizes will be necessary to verify them. This reinforces the importance of highly visual cranio-facial and frill ornamentation as the best tool for species recognition and phylogenetic reconstruction in ceratopsid dinosaurs.

Sebecus icaeorhinus possessed a narrow, elevated snout and laterally compressed, serrate teeth, unlike modern crocodilians, but superficially similar to those of theropod dinosaurs. Lever arms of the mandibular adductors were generally relatively greater than those of Crocodylus niloticus. Some of the adductors and the depressor mandibulae were relatively larger than in Alligator mississippiensis. Thus Sebecus may have had a stronger bite than the modern forms examined. The form of the teeth suggests use in cutting. Some theropod dinosaurs are similar to sebecosuchians in the possession of relatively deep, narrow snouts and laterally-compressed, serrate teeth. However, the adductor structure was substantially different from that of Sebecus. The presence of muscle and tendon attachments in Sebecus suggests the adductor structure of mesoeucrocodylians is conservative and was established before divergence of the sebecosuchian and neosuchian lineages. No results presented here contradict the interpretation of sebecosuchians as land-dwelling predators.