RESUMEN
Current hypotheses of early tetrapod evolution posit close ecological and biogeographic ties to the extensive coal-producing wetlands of the Carboniferous palaeoequator with rapid replacement of archaic tetrapod groups by relatives of modern amniotes and lissamphibians in the late Carboniferous (about 307 million years ago). These hypotheses draw on a tetrapod fossil record that is almost entirely restricted to palaeoequatorial Pangea (Laurussia)1,2. Here we describe a new giant stem tetrapod, Gaiasia jennyae, from high-palaeolatitude (about 55° S) early Permian-aged (about 280 million years ago) deposits in Namibia that challenges this scenario. Gaiasia is represented by several large, semi-articulated skeletons characterized by a weakly ossified skull with a loosely articulated palate dominated by a broad diamond-shaped parasphenoid, a posteriorly projecting occiput, and enlarged, interlocking dentary and coronoid fangs. Phylogenetic analysis resolves Gaiasia within the tetrapod stem group as the sister taxon of the Carboniferous Colosteidae from Euramerica. Gaiasia is larger than all previously described digited stem tetrapods and provides evidence that continental tetrapods were well established in the cold-temperate latitudes of Gondwana during the final phases of the Carboniferous-Permian deglaciation. This points to a more global distribution of continental tetrapods during the Carboniferous-Permian transition and indicates that previous hypotheses of global tetrapod faunal turnover and dispersal at this time2,3 must be reconsidered.
Asunto(s)
Fósiles , Cubierta de Hielo , Conducta Predatoria , Vertebrados , Animales , Historia Antigua , Namibia , Hueso Paladar/anatomía & histología , Filogenia , Cráneo/anatomía & histología , Diente/anatomía & histología , Vertebrados/anatomía & histología , Vertebrados/clasificación , Humedales , Tamaño CorporalRESUMEN
Sauropodomorph dinosaurs dominated the herbivorous niches during the first 40 million years of dinosaur history (Late Triassic-Early Jurassic), yet palaeobiological factors that influenced their evolutionary success are not fully understood. For instance, knowledge on their behaviour is limited, although herding in sauropodomorphs has been well documented in derived sauropods from the Late Jurassic and Cretaceous. Here we report an exceptional fossil occurrence from Patagonia that includes over 100 eggs and skeletal specimens of 80 individuals of the early sauropodomorph Mussaurus patagonicus, ranging from embryos to fully-grown adults, with an Early Jurassic age as determined by high-precision U-Pb zircon geochronology. Most specimens were found in a restricted area and stratigraphic interval, with some articulated skeletons grouped in clusters of individuals of approximately the same age. Our new discoveries indicate the presence of social cohesion throughout life and age-segregation within a herd structure, in addition to colonial nesting behaviour. These findings provide the earliest evidence of complex social behaviour in Dinosauria, predating previous records by at least 40 My. The presence of sociality in different sauropodomorph lineages suggests a possible Triassic origin of this behaviour, which may have influenced their early success as large terrestrial herbivores.
Asunto(s)
Dinosaurios/anatomía & histología , Paleontología/métodos , Animales , Argentina , Conducta Animal , Evolución Biológica , Huevos , Fósiles , Geografía , Filogenia , Factores de TiempoRESUMEN
BACKGROUND: a death number increment compared to the previous years was observed in Italy for the year 2015; its causes are under study. OBJECTIVES: to verify if the mortality occurred in Palermo Province (Sicily Region, Southern Italy) for the year 2015 was greater than the one observed in the previous period (years 2009-2014) and to find which death causes it would be attributable to. DESIGN: observed number of deaths in 2015 were compared with expected numbers calculated with the traditional analysis of direct adjusted rates, and with a 90% predictive interval estimated fitting a Generalized Additive Model (GAM), via a quasi-Poisson distribution of the observed deaths in the period 2009-2014; various measures of the environmental temperature were used as regressor. The latter method was used also to analyse causes of death. SETTING AND PARTICIPANTS: all deaths occurred in residents in Palermo Province in the years 2009-2015. RESULTS: for each population subgroup based on sex and residence, direct adjusted rates for 2015 were lower than those observed in the previous period, but for women resident in towns outside Palermo (observed/estimated ratio: 1.04; 95%IC 1.00-1.08). GAM analysis shows mortality excesses only in men aged more than 64 years; in Palermo residents, excesses were shown in the 2nd week of December; in residents in towns of the Province excesses were shown in the 2nd and 3rd week of February and in the 1st and 2nd week of August. In the death causes analysis, mortality excesses were shown for pneumonia and bronchial pneumonia in the 1st and 2nd weeks of January; 3rd week of February; in the 1st, 2nd and 4th week of August; and in the 1st week of October. For infectious diseases, these excesses were observed in the 1st week of March. CONCLUSIONS: it is plausible that in some weeks of the year 2015 there have been a mortality excess; however, as all-year mortality is lower or equal to that of the previous periods, the Authors believe that there is an harvesting effect, that is a mortality displacement that does not affect total mortality.
Asunto(s)
Mortalidad/tendencias , Adolescente , Adulto , Causas de Muerte/tendencias , Niño , Preescolar , Femenino , Humanos , Masculino , Persona de Mediana Edad , Modelos Estadísticos , Sicilia/epidemiología , Factores de Tiempo , Adulto JovenRESUMEN
Dinosaurs have been major components of ecosystems for over 200 million years. Although different macroevolutionary scenarios exist to explain the Triassic origin and subsequent rise to dominance of dinosaurs and their closest relatives (dinosauromorphs), all lack critical support from a precise biostratigraphically independent temporal framework. The absence of robust geochronologic age control for comparing alternative scenarios makes it impossible to determine if observed faunal differences vary across time, space, or a combination of both. To better constrain the origin of dinosaurs, we produced radioisotopic ages for the Argentinian Chañares Formation, which preserves a quintessential assemblage of dinosaurian precursors (early dinosauromorphs) just before the first dinosaurs. Our new high-precision chemical abrasion thermal ionization mass spectrometry (CA-TIMS) U-Pb zircon ages reveal that the assemblage is early Carnian (early Late Triassic), 5- to 10-Ma younger than previously thought. Combined with other geochronologic data from the same basin, we constrain the rate of dinosaur origins, demonstrating their relatively rapid origin in a less than 5-Ma interval, thus halving the temporal gap between assemblages containing only dinosaur precursors and those with early dinosaurs. After their origin, dinosaurs only gradually dominated mid- to high-latitude terrestrial ecosystems millions of years later, closer to the Triassic-Jurassic boundary.
Asunto(s)
Evolución Biológica , Dinosaurios/anatomía & histología , Animales , Argentina , Calibración , Geografía , Factores de TiempoRESUMEN
OBJECTIVE: to assess whether compositional (education, income index, number of family members) and contextual (area socioeconomic index) risk factors independently predict all cause and specific mortality. DESIGN: a multilevel (hierarchic) logistic regression model was applied to the individual data of a cohort followed up from 01.01.2002 till 31.12.2007. SETTING AND PARTICIPANTS: the study evaluated 40-79 years old people resident in Palermo at 01.01.2002, for whom it was possible to match register office and census data (220,723 people, 74.8% of the same age group total population). MAIN OUTCOMES MEASURES: odds ratios for specific risk factors. RESULTS: mortality was generally lower in people with better socioeconomic conditions and living in more affluent neighbourhoods. Individual risk factors odds ratios do not vary in models with and without area related risk factor. Variance partition component and other between area and total variability ratio index show small values. CONCLUSION: compositional and contextual socioeconomic factors are independent predictors of mortality; area related variability is only a small fraction of total variability.
Asunto(s)
Mortalidad/tendencias , Adulto , Anciano , Femenino , Humanos , Italia , Modelos Logísticos , Masculino , Persona de Mediana Edad , Análisis de Regresión , Factores de Riesgo , Factores SocioeconómicosRESUMEN
OBJECTIVE: To assess whether mortality rates differ among areas with different values of a socioeconomic index. DESIGN: Ecological mortality study; mortality rates were compared among four areas joining census tracts categorized by quartiles of a socioeconomic status index. This index was calculated using individual 2001 census data in a factorial analysis. SETTING: The study was conducted in Palermo (Italy) a city with 668,996 inhabitants in 2006. MAIN OUTCOMES MEASURES: Sex, age group, cause specific standardized mortality rates and rate ratios, expected life years. RESULTS: The area with the lowest value of the socioeconomic index had mortality rates higher than the area with the uppermost value. This occurred in both sexes, all age groups and for most mortality causes (with few exceptions): not all rate ratios were always statistically significant. CONCLUSION: Despite limitations due to the use of an area-based index, results suggest that the welfare system is not successful in compensating health inequalities caused by socioeconomic inequalities.