ALBERT

Description: Euparkeria capensis has long been considered an archetype for the ancestral archosaur morphology, and has been placed just outside of crown Archosauria by nearly all cladistic analyses. Six species are currently considered to be putative members of a clade Euparkeriidae, and have been collected from Olenekian- or Anisian-aged deposits in South Africa (Euparkeria capensis – the only definitive member of the group), China (Halazhaisuchus qiaoensis, Wangisuchus tzeyii, ‘Turfanosuchus’ shageduensis), Russia (Dorosuchus neoetus) and Poland (Osmolskina czatkowicensis). Four other species (Turfanosuchus dabanensis, Xilousuchus sapingensis, Platyognathus hsui, Dongusia colorata) were historically assigned to Euparkeriidae, but have been removed by recent work. Recent authors deemed Osmolskina czatkowicensis and Dorosuchus neoetus to be the most likely taxa to form a euparkeriid clade with Euparkeria capensis, but Osmolskina czatkowicensis and Euparkeria capensis were not found as sister taxa by the only cladistic analysis to have tested euparkeriid monophyly. Euparkeria capensis was small (〈1 m), insectivorous or carnivorous, probably had vision adapted to low-light conditions and a semi-erect crocodile-like stance, and may have been facultatively bipedal. Bone histology demonstrates that Euparkeria capensis had a slow growth rate, which has been suggested to have been an adaptation to relatively stable environmental conditions.

Description: Pterosaurs are a clade of highly specialized, volant archosauromorphs recorded from the Upper Triassic to the uppermost Cretaceous. Problematic remains referred to the Pterosauria are reported from the Triassic of Europe and both North and South America, but unequivocal pterosaur specimens are only known from the Alps (Italy, Austria and Switzerland: Preondactylus buffarinii, Austriadactylus cristatus, Peteinosaurus zambellii, Eudimorphodon ranzii, Carniadactylus rosenfeldi, Caviramus schesaplanensis and Raeticodactylus filisurensis) and Greenland (‘Eudimorphodon’ cromptonellus). Pterosaurs are diagnosed mostly by features associated with the advent of powered flight. They are generally considered to be archosaurians more closely related to dinosaurs than to crocodilians, but non-archosaurian positions have also been proposed. There is a lack of general agreement about ingroup relationships, particularly among the basal pterosaurs. Triassic pterosaurs differ from other non-pterodactyloid pterosaurs in features of the dentition and caudal vertebral column. A ‘Big Bang’ model for their early history fits better with the fossil record: the earliest unequivocal pterosaurs show a sudden and geographically limited appearance in the fossil record, as well as a relatively high burst of diversity and considerable morphologic disparity. Absence of pterosaur remains from deposits where they are expected to be found suggests that they had not yet evolved in pre-Norian times.

Description: The ornithosuchids were a group of archosaurs with body lengths ranging from 2 to 4 m recorded from Upper Triassic beds in Argentina and Scotland. The group was defined as a node-based clade including Ornithosuchus longidens, Riojasuchus tenuisceps, Venaticosuchus rusconii and all descendants of their most recent common ancestor. The ornithosuchids are diagnosed by the following apomorphies observed in the three known species of the clade: downturned premaxilla; premaxilla–maxilla contact with a diastema in the alveolar margin equal in length to two teeth; palatine–pterygoid fenestra; and orbit with a distinct ventral point surrounded by ‘V’-shaped dorsal processes of the jugal. The most remarkable postcranial apomorphy of the group is the presence of the so-called crocodile reversed ankle joint, a condition that seems to be unique for the ornithosuchids among amniotans. The systematic history of Ornithosuchidae is complex and Ornithosuchus was allied with dinosaurs or phytosaurs prior to the implementation of numerical phylogenetic analyses. Currently, there is consensus that Ornithosuchidae is positioned within Pseudosuchia, but their phylogenetic position within the group remains strongly debated. Nevertheless, all hypotheses agree in inferring an extremely long ghost lineage at the base of the clade. The presence of derived pseudosuchians in the late Olenekian produces a ghost lineage of c. 16–18 millions of years for Ornithosuchidae, indicating that only the late evolutionary history of the clade is currently sampled in the fossil record.

Description: Prestosuchus chiniquensis is an extinct species of terrestrial archosaur from the Middle Triassic Epoch restricted to southern Brazil. In this paper the thigh musculature of P. chiniquensis is reconstructed based on a well-preserved specimen and on myological descriptions of extant birds and crocodylians. Among the 16 analysed muscular groups, 13 were recognized as present and homologous to both extant groups of archosaurs, and two only to the crocodylian line of archosaurs, so that 15 muscular groups were reconstructed in the fossil specimen. Morphological particularities of the pelvic girdle and the hindlimbs of P. chiniquensis gave a distinct arrangement for the muscular origin and insertion sites, leading to different lines of action and functions when compared with extant archosaurs. The comparison between extinct and extant archosaurs showed a basal condition sustained in some aspects, such as the morphology of the femur and the flexion of the knee, although other aspects were considered as derived, such as the morphology of the pubis and ischium, and their associated muscle origin locations.

Description: A small aetosaur skull and skeleton and referred material from the Chinle Formation, Eagle Basin of Colorado, USA, is described as a new taxon, Stenomyti huangae gen. et sp. nov, distinguished from other aetosaurs by the following autapomorphies: three premaxillary teeth; four palpebrals; pronounced midline ridge on frontals and parietals; paired ridges flanking midline ridge on parietal and frontal; exclusion of quadratojugal from ventral margin of skull by contact between jugal and quadrate; exclusion of postorbital from infratemporal fenestra; infratemporal fenestra a horizontally oriented oval that embays the posterior edge of the jugal; retroarticular process longer than distance between articular glenoid and posterior edge of external mandibular fenestra; oval to irregularly shaped ventral osteoderms that do not contact each other. Paramedian and lateral osteoderms of S. huangae are nearly identical to those of Aetosaurus ferratus, and other shared cranial characters suggest that these taxa are closely related and lie outside the clade Typothoracisinae + Desmatosuchinae. This discovery indicates that other reports of Aetosaurus across Laurasia based on osteoderms should be reassessed. Similar confusion with the osteoderms of other non-typothoracisine/desmatosuchine aetosaurs such as Aetosauroides, Stagonolepis and Calyptosuchus suggests that osteoderms are not always reliable taxonomic indicators.

Description: Non-crocodyliform crocodylomorphs, often called ‘sphenosuchians’, were the earliest-diverging lineages of Crocodylomorpha, and document the stepwise acquisition of many of the features that characterize extant crocodylians. The first crocodylomorph fossils are approximately 230 million years old (upper Carnian, Late Triassic), and at least one of these early lineages persisted until at least 150 million years ago (Late Jurassic). These taxa occupied a wide variety of terrestrial environments from equatorial regions to high-paleolatitudes during the early Mesozoic. Despite a quarter-century of quantitative phylogenetic work, the interrelationships of early crocodylomorphs remain in a state of flux, though recent studies suggest that these lineages are paraphyletic with respect to Crocodyliformes, rather than forming a monophyletic early offshoot of Crocodylomorpha as some previously hypothesized. Nearly all early crocodylomorphs were upright quadrupedal small-bodied taxa, but lumping them all together as small cursorial faunivores masks ecological and morphological disparity in diet and limb functional morphology. With the accelerated pace of recent discovery of new specimens and taxa, future consensus on early crocodylomorph phylogeny will provide a solid framework for understanding their change in diversity and disparity through time, potential biogeographic patterns, and the morphological transformation leading to Crocodyliformes.

Description: Recent palaeohistological studies on paramedian osteoderms of aetosaurs revealed the presence of growth lines (lines of arrested growth or LAGs) and a minimal or nonexistent secondary remodelling in the bone matrix of these elements. This feature allows the age of individuals to be estimated through growth line count. In the present contribution we study the growth curve of the South American aetosaur Aetosauroides scagliai. We estimated the age (obtained from LAG counting) and body size (body length and body mass were used as proxies) of different aetosaur specimens in order to reconstruct the growth curve of the South American species. The data obtained for Aetosauroides scagliai were compared with that of other aetosaurs, such as Neoaetosauroides engaeus, Aetosaurus ferratus, Aetobarbakinoides brasiliensis, Typothorax coccinarum and Paratypothorax sp. Our results indicate that, if body length is considered as proxy, all studied aetosaur specimens have a similar or almost identical growth rate. However, important variations arose among aetosaur taxa if body mass is considered as proxy, which would be related to a body morphology ranging from slender (e.g. Aetobarbakinoides brasiliensis) to very wide (Typothorax coccinarum) morphotypes. In comparison with extant pseudosuchians (i.e. crocodylians), Aetosauroides scagliai possesses a relatively lower growth rate.

Description: Unlike most rauisuchians, which are known based on partially preserved specimens, fossils attributed to Decuriasuchus quartacolonia include a monotaxonomic assemblage composed of nine associated individuals (MCN-PV10.105a–i), three with almost complete skulls (MCN-PV10.105a,c,d), and a partial disarticulated skull (MCN-PV10.004) collected in the Middle Triassic (Ladinian, Dinodontosaurus Biozone) beds of the Santa Maria Formation, in south Brazil. Because of its completeness and possible phylogenetic position, as one of the most basal loricatans, D. quartacolonia is a key taxon for anatomic, evolutionary and biomechanical studies of rauisuchians. The comparative description of its osteology reveals that the skull and mandible of D. quartacolonia are very similar to those of cf. Prestosuchus chiniquensis and Saurosuchus galilei, sharing a drop-shaped subnarial fenestra, a subtriangular antorbital fenestra with an elongated and narrow anterior point, a ‘roman nosed’ nasal, and a posteroventrally oriented ridge on the lateral surface of the ventral ramus of the squamosal. Among the differences are the autapomorphies of D. quartacolonia: numerous maxillary teeth (17), lateral expansion of the nasal/lacrimal covering the antorbital fenestra dorsally, and squamosal and quadratojugal forming a subtriangular projection that invades the lower temporal fenestra.

Description: Ichnological evidence suggests that dinosauromorphs originated by the Early Triassic, and skeletal remains of non-dinosaur representatives of the clade occur from the Anisian to the end of the Triassic. These taxa are small- to medium-sized, vary in feeding and locomotor features, and occurred over most of western Pangaea. They include the small lagerpetids from the Mid–Late Triassic of Argentina and the United States, and the larger, quadrupedal Silesauridae, with records in the Middle Triassic of Africa and Argentina, and in the Late Triassic of Europe, the Americas and northern Africa. The former group represents the earliest diverging dinosauromorphs, whereas silesaurids are more closely related to Dinosauria. Other dinosauromorphs include the archetypal early dinosauriform Marasuchus lilloensis (Middle Triassic of Argentina) and poorly known/controversial taxa such as Lewisuchus admixtus and Saltopus elginensis. The earliest diverging dinosauromorphs may have preyed on small animals (including insects), but cranio-dental remains are rare; by contrast, most silesaurids probably included plant material in their diet, as indicated by their modified jaw apparatus and teeth. Our knowledge of the anatomy and thus relationships of non-dinosaurian Dinosauromorpha is still deficient, and we suspect that future discoveries will continue to reveal novel patterns and hypotheses of palaeobiology and biogeography.

Description: Proterochampsia is a monophyletic group of crocodile-like archosauriforms currently endemic to the late Middle and early Late Triassic of South America considered as one of the potential successive sister-taxa of the crown group Archosauria. The proterochampsians come from the Ischigualasto-Villa Unión Basin in the west of Argentina and the Parana Basin in the south of Brazil. The traditional composition of the group includes the genera Cerritosaurus Price 1946, Proterochampsa Reig 1959 (with two species: P. barrionuevoi in Argentina and P. nodosa Barberena 1982 in Brazil), Chanaresuchus Romer (with two species from Argentina: C. bonapartei Romer and C. ischigualastensis Trotteyn et al. 2012), Gualosuchus reigi Romer 1971 and Tropidosuchus romeri Arcucci 1990. After a precladistic history of confusion about their relationships with crocodilians, in the last 20 years new discoveries of taxa, and more systematic and phylogenetic studies, have clarified their position as non-archosaurian archosauriforms and their relationships with other Triassic archosaurs.