On a new Melanosuchus species (Alligatoroidea: Caimaninae) from Solimões Formation (Eocene-Pliocene), Northern Brazil, and evolution of Caimaninae.

The Solimões Formation (Eocene-Pliocene) is a well-known geological unit due to the great diversity of crocodylian species. Here we describe a new species of Melanosuchus, M. latrubessei sp. nov., from the Talismã locality, state of Amazonas, from the Upper Miocene of the Solimões Formation (Solimões Basin, Brazil). A new phylogenetic inference focused on Caimaninae is provided and the different evolutionary scenarios involving this new species are discussed. In addition, quantitative morphology studies are carried out and comments regarding the paleoecology aspects of this new species are made. M. latrubessei represents a medium-sized generalist predator, being proportional to the medium-sized M. niger. This new species inhabited the drainages of the Solimões Formation and was ecologically related to other taxa of crocodylians during the proto-Amazon Miocene. The evolutionary advantages of Melanosuchus genus are discussed to better understand the biogeographical occurrence of M. niger in South America, a species which survives to this day in contrast to several other species that became extinct during the Miocene-Pliocene periods. The extinction of the Miocene-Pliocene crocodylian taxa of the Solimões Formation, including Melanosuchus latrubessei, seems to be directly related with the uplift of the northern portions of the Andes, which generated significantly changes in drainages and Amazon paleoenvironments.

Measuring resilience and assessing vulnerability of terrestrial ecosystems to climate change in South America.

Climate change has been identified as the primary threat to the integrity and functioning of ecosystems in this century, although there is still much uncertainty about its effects and the degree of vulnerability for different ecosystems to this threat. Here we propose a new methodological approach capable of measuring and mapping the resilience of terrestrial ecosystems at large scales based on their climatic niche. To do this, we used high spatial resolution remote sensing data and ecological niche modeling techniques to calculate and spatialize the resilience of three stable states of ecosystems in South America: forest, savanna, and grassland. Also, we evaluated the sensitivity of ecosystems to climate stress, the likelihood of exposure to non-analogous climatic conditions, and their respective adaptive capacities in the face of climate change. Our results indicate that forests, the most productive and biodiverse terrestrial ecosystems on the earth, are more vulnerable to climate change than savannas or grasslands. Forests showed less resistance to climate stress and a higher chance of exposure to non-analogous climatic conditions. If this scenario occurs, the forest ecosystems would have less chance of adaptation compared to savannas or grasslands because of their narrow climate niche. Therefore, we can conclude that a possible consolidation of non-analogous climatic conditions would lead to a loss of resilience in the forest ecosystem, significantly increasing the chance of a critical transition event to another stable state with a lower density of vegetation cover (e.g., savanna or grassland).

Neogene sharks and rays from the Brazilian 'Blue Amazon'.

The lower Miocene Pirabas Formation in the North of Brazil was deposited under influence of the proto-Amazon River and is characterized by large changes in the ecological niches from the early Miocene onwards. To evaluate these ecological changes, the elasmobranch fauna of the fully marine, carbonate-rich beds was investigated. A diverse fauna with 24 taxa of sharks and rays was identified with the dominant groups being carcharhiniforms and myliobatiforms. This faunal composition is similar to other early Miocene assemblages from the proto-Carribbean bioprovince. However, the Pirabas Formation has unique features compared to the other localities; being the only Neogene fossil fish assemblage described from the Atlantic coast of Tropical Americas. Phosphate oxygen isotope composition of elasmobranch teeth served as proxies for paleotemperatures and paleoecology. The data are compatible with a predominantly tropical marine setting with recognized inshore and offshore habitats with some probable depth preferences (e.g., Aetomylaeus groups). Paleohabitat of taxa particularly found in the Neogene of the Americas (†Carcharhinus ackermannii, †Aetomylaeus cubensis) are estimated to have been principally coastal and shallow waters. Larger variation among the few analyzed modern selachians reflects a larger range for the isotopic composition of recent seawater compared to the early Miocene. This probably links to an increased influence of the Amazon River in the coastal regions during the Holocene.