The Osteology of the Basal Archosauromorph Tasmaniosaurus triassicus from the Lower Triassic of Tasmania, Australia

Proterosuchidae are the most taxonomically diverse archosauromorph reptiles sampled in the immediate aftermath of the Permo-Triassic mass extinction and represent the earliest radiation of Archosauriformes (archosaurs and closely related species). Proterosuchids are potentially represented by approximately 15 nominal species collected from South Africa, China, Russia, Australia and India, but the taxonomic content of the group is currently in a state of flux because of the poor anatomic and systematic information available for several of its putative members. Here, the putative proterosuchid Tasmaniosaurus triassicus from the Lower Triassic of Hobart, Tasmania (Australia),is redescribed. The holotype and currently only known specimen includes cranial and postcranial remains and the revision of this material sheds new light on the anatomy of the animal, including new data on the cranial endocast. Several bones are re-identified or reinterpreted, contrasting with the descriptions of previous authors. The new information provided here shows that Tasmaniosaurus closely resembles the South African proterosuchid Proterosuchus, but it differed in the presence of, for example, a slightly downturned premaxilla, a shorter anterior process of maxilla, and a diamond-shaped anterior end of interclavicle. Previous claims for the presence of gut contents in the holotype of Tasmaniosaurus are considered ambiguous. The description of the cranial endocast of Tasmaniosaurus provides for the first time information about the anatomy of this region in proterosuchids. The cranial endocast preserves possibly part of the vomero-nasal (= Jacobson's) system laterally to the olfactory bulbs. Previous claims of the absence of the vomero-nasal organs in archosaurs, which is suggested by the extant phylogenetic bracket, are questioned because its absence in both clades of extant archosaurs seems to be directly related with the independent acquisition of a non-ground living mode of life

Systematics and evolutionary history of proterosuchian archosauriforms

The evolutionary history of archosauromorphs is of particular interest because it includes the origins of two of the best-known and most distinctive extant tetrapod groups: crocodylians and birds. In this thesis, the anatomy, taxonomy and systematics of the Permo-Triassic non-archosaur archosauromorphs are revised. A revision of the Permo-Triassic archosauromorph record indicates that only four Permian species are known and there are three valid proterosuchid species immediately after the Permo-Triassic boundary in South Africa. Analyses of cranial ontogenetic variation in $Proterosuchus$ $fergusi$ found that ontogenetic modification events (e.g. heterochrony) may have been key drivers of the evolution of the general shape of the skull at the base of Archosauriformes. A comprehensive quantitative phylogenetic analysis recovered a polyphyletic “Prolacertiformes”, restricted the taxonomic content of Proterosuchidae to only six species, Erythrosuchidae was composed of eight nominal species, and $Euparkeria$ $capensis$ was found as the sister-taxon of the clade that includes proterochampsians (doswelliids + proterochampsids) and archosaurs. The results obtained here suggest that the evolutionary history of the archosauriforms during the Early Triassic can be subdivided into a first phase characterized by the short-lived “disaster-clade” Proterosuchidae and a second phase that witnessed the initial morphological and probably palaeoecological diversification of the group

Cranial ontogenetic variation in early saurischians and the role of heterochrony in the diversification of predatory dinosaurs

Non-avian saurischian skulls underwent at least 165 million years of evolution and shapes varied from elongated skulls, such as in the theropod Coelophysis, to short and box-shaped skulls, such as in the sauropod Camarasaurus. A number of factors have long been considered to drive skull shape, including phylogeny, dietary preferences and functional constraints. However, heterochrony is increasingly being recognized as an important factor in dinosaur evolution. In order to quantitatively analyse the impact of heterochrony on saurischian skull shape, we analysed five ontogenetic trajectories using two-dimensional geometric morphometrics in a phylogenetic framework. This allowed for the comparative investigation of main ontogenetic shape changes and the evaluation of how heterochrony affected skull shape through both ontogenetic and phylogenetic trajectories. Using principal component analyses and multivariate regressions, it was possible to quantify different ontogenetic trajectories and evaluate them for evidence of heterochronic events allowing testing of previous hypotheses on cranial heterochrony in saurischians. We found that the skull shape of the hypothetical ancestor of Saurischia likely led to basal Sauropodomorpha through paedomorphosis, and to basal Theropoda mainly through peramorphosis. Paedomorphosis then led from Orionides to Avetheropoda, indicating that the paedomorphic trend found by previous authors in advanced coelurosaurs may extend back into the early evolution of Avetheropoda. Not only are changes in saurischian skull shape complex due to the large number of factors that affected it, but heterochrony itself is complex, with a number of possible reversals throughout non-avian saurischian evolution. In general, the sampling of complete ontogenetic trajectories including early juveniles is considerably lower than the sampling of single adult or subadult individuals, which is a major impediment to the study of heterochrony on non-avian dinosaurs. Thus, the current work represents an exploratory analysis. To better understand the cranial ontogeny and the impact of heterochrony on skull evolution in saurischians, the data set that we present here must be expanded and complemented with further sampling from future fossil discoveries, especially of juvenile individuals

A revision of the ‘coelophysoid-grade’ theropod specimen from the Lower Jurassic of the Isle of Skye (Scotland)

The broadest diversification of early predatory dinosaurs is represented by the ‘coelophysoid-grade’ neotheropods, but their Hettangian–Sinemurian (c. 191–201 Ma) record is scarce worldwide. More information is needed to shed light on the evolution of this dinosaur group after the end-Triassic mass extinction (c. 201 Ma). Here we revisit the anatomy and phylogeny of one of these earliest Jurassic neotheropod specimens, an isolated partial tibia from the lower Sinemurian of the Isle of Skye (Scotland) that was previously identified as probably closely related to Liliensternus liliensterni and coelophysids. However, we found that the Skye specimen is positioned in the branch leading to Averostra (Ceratosauria + Tetanurae), in a polytomy with Sarcosaurus woodi from the late Hettangian–lower Sinemurian of central England and a clade composed of Tachiraptor admirabilis and Averostra. The morphology of the Skye specimen is congruent with that of referred specimens of Sarcosaurus woodi, but because it probably represents a skeletally immature specimen, we assign it to cf. Sarcosaurus woodi. The Skye specimen increases the number of averostran-line neotheropod specimens recorded in the Lower Jurassic of Europe and current evidence indicates that these forms, and not coelophysoids, were relatively common in this part of the world at that time

Early dinosaur radiation: testing macroevolutionary models through diversification rate shift analyses of an early Mesozoic amniotan supertree

The early radiation of dinosaurs has been traditionally explained through a "competitive model", which attributes dinosaur success to their superiority in a drawn-out process involving inter-specific competition, or a more accepted "opportunistic model", which states that dinosaur radiation occurred in an empty ecospace cleared by two successive Late Triassic extinctions. Following the "opportunistic model", it would be expected that dinosaurs acquired diversification shifts only after the Late Triassic extinctions. Conversely, in the "competitive model" diversification shifts would be expected during the evanescence of their competitors. With the aim to test how these models fit to current phylogenetic reconstructions, a diversification rate analysis was performed on an amniotan supertree of 690 taxa. We found that the early dinosaur phylogeny significantly departs from a stochastic branching model (p<0.001) and a significant branching shift is located at the base of Dinosauria (p<0.05). This result is in agreement with the high diversity of early dinosaurs observed in the Ischigualasto Formation (early Late Triassic), clearly supporting that the dinosaur radiation started before the end-Ischigualastian extinction (middle Late Triassic). Ischigualastian continental assemblages were dominated by rhynchosaurs and traversodontids, and crurotarsans were common faunistic elements, indicating that the early radiation of dinosaurs firstly took place into a crowded-ecospace. However, branching patterns are not homogenous within Dinosauria: diversification shifts for Theropoda occurred at Ischigualastian and Hettangian-Sinemurian times (Early Jurassic), but in the case of Sauropodormorpha and Ornithischia the shifts took place in the Coloradian (latest Late Triassic), immediately after the end-Ischigualastian extinction. Together with herbivorous dinosaurs another six significant/conspicuous branching shifts are also recorded among Coloradian amniotan clades (e.g., mammaliamorphs, crocodylomorphs, pterosaurs), indicating that this stage of diversification was also experienced by another amniotan lineages. Accordingly, the early radiation of dinosaurs started during the Ischigualastian in a crowded-ecospace, showing different patterns within the group later in the Triassic, within a macroevolutionary scenario that does not completely fit with none of the two traditional models.Sesiones libresFacultad de Ciencias Naturales y Muse

On the causes of economic growth in Europe: why did agricultural labour productivity not converge between 1950 and 2005?

The objective of this study is to make a further contribution to the debate on the causes of economic growth in the European Continent. It explains why agricultural labour productivity differences did not converge between 1950 and 2005 in Europe. We propose an econometric model, one combining both proximate and fundamental causes of economic growth. The results show that the continuous exit of labour power from the sector, coupled with the increased use of productive factors originating in other sectors of the economy, caused the efficiency of agricultural workers to rise. However, we offer a complete explanation of the role played by institutions and geographical factors. Thus, we detect a direct and inverse relation between membership of the EU and the Communist bloc and the productivity of agricultural labour. In addition, strong support for agriculture affected productivity negatively

Is There Increasing Regional Specialisation within the General Process of Deindustrialisation?

Trade theory and economic geography suggest that the removal of trade barriers is likely to bring about more economic specialisation and potentially more diverse development paths between countries and regions. Thus, the deepening and extending European integration should be accompanied by an increasing regional specialisation. In contrast, our results for the period from 1995 to 2004 show considerably declining differences in the share of manufacturing in total value added across nations and regions of the EU. The decrease in sectoral specialisation is accompanied by a strong and almost uniform process of deindustrialisation. However, this trend is slowing down and manufacturing shares appear to be gradually approaching lower limits. These bounds are specific according to national affiliation and settlement types of regions

The multi-peak adaptive landscape of crocodylomorph body size evolution

Background: Little is known about the long-term patterns of body size evolution in Crocodylomorpha, the > 200-million-year-old group that includes living crocodylians and their extinct relatives. Extant crocodylians are mostly large-bodied (3–7 m) predators. However, extinct crocodylomorphs exhibit a wider range of phenotypes, and many of the earliest taxa were much smaller ( Results: Crocodylomorphs reached an early peak in body size disparity during the Late Jurassic, and underwent an essentially continual decline since then. A multi-peak Ornstein-Uhlenbeck model outperforms all other evolutionary models fitted to our data (including both uniform and non-uniform), indicating that the macroevolutionary dynamics of crocodylomorph body size are better described within the concept of an adaptive landscape, with most body size variation emerging after shifts to new macroevolutionary regimes (analogous to adaptive zones). We did not find support for a consistent evolutionary trend towards larger sizes among lineages (i.e., Cope’s rule), or strong correlations of body size with climate. Instead, the intermediate to large body sizes of some crocodylomorphs are better explained by group-specific adaptations. In particular, the evolution of a more aquatic lifestyle (especially marine) correlates with increases in average body size, though not without exceptions. Conclusions: Shifts between macroevolutionary regimes provide a better explanation of crocodylomorph body size evolution on large phylogenetic and temporal scales, suggesting a central role for lineage-specific adaptations rather than climatic forcing. Shifts leading to larger body sizes occurred in most aquatic and semi-aquatic groups. This, combined with extinctions of groups occupying smaller body size regimes (particularly during the Late Cretaceous and Cenozoic), gave rise to the upward-shifted body size distribution of extant crocodylomorphs compared to their smaller-bodied terrestrial ancestors.</p