Francisco Ricardo Negri

Amazonia Through Time: Andean Uplift, Climate Change, Landscape Evolution, and Biodiversity

The Making of Amazonian Diversity The biodiversity of the Amazon Basin is legendary, but the processes by which it has been generated have been debated. In the late 20th century the prevalent view was that the engine of diversity was repeated contraction and expansion of forest refugia during the past 3 million years or so. Hoorn et al. (p. 927) analyze findings from a diverse range of disciplines, including molecular phylogeny, ecology, sedimentology, structural geology, and palaeontology, to offer an overview of the entire history of this region during the Cenozoic era (66 million years ago). The uplift of the Andes was a pivotal event in the evolution of Amazonian landscapes because it continually altered river drainage patterns, which in turn put a variety of pressures on organisms to adapt to changing conditions in a multiplicity of ways. Hence, the diversity of the modern biota of the Amazon has more ancient origins than previously thought. The Amazonian rainforest is arguably the most species-rich terrestrial ecosystem in the world, yet the timing of the origin and evolutionary causes of this diversity are a matter of debate. We review the geologic and phylogenetic evidence from Amazonia and compare it with uplift records from the Andes. This uplift and its effect on regional climate fundamentally changed the Amazonian landscape by reconfiguring drainage patterns and creating a vast influx of sediments into the basin. On this “Andean” substrate, a region-wide edaphic mosaic developed that became extremely rich in species, particularly in Western Amazonia. We show that Andean uplift was crucial for the evolution of Amazonian landscapes and ecosystems, and that current biodiversity patterns are rooted deep in the pre-Quaternary.

Late Miocene Tidal Deposits in the Amazonian Foreland Basin

Late Miocene tidal sediments of Acre, Brazilian Amazonia, were deposited in an embayment or interior seaway located in the sub-Andean zone. This late Tertiary embayment system may once have connected the Caribbean with the South Atlantic. The tidal coasts of the embayment-seaway have provided an avenue for the earliest waif (over water) dispersal phases of the great American biotic interchange in the late Miocene. The subsequent change from semimarine to terrestrial environments is of value in assessing the importance of earlier hypotheses on the evolution of the westem Amazonian landscape and gives insight into the formation of several observed biogeographic patterns, especially of aquatic biota.

NEW CHARACOIDS FROM THE UPPER CRETACEOUS AND PALEOCENE OF BOLIVIA AND THE MIO-PLIOCENE OF BRAZIL: PHYLOGENETIC POSITION AND PALEOBIOGEOGRAPHIC IMPLICATIONS

Abstract New genera of characoid fossil fishes are described on the basis of remains from the Maastrichtian El Molino Formation and the early late Paleocene Santa Lucía Formation of Bolivia, and the Mio-Pliocene Solimões Formation of Brazil. Comparisons with the Hepsetidae, Erythrinidae, Ctenoluciidae, Acestrorhynchidae, and the characid Hydrocynus allow the following conclusions to be made: the new Bolivian genus lacks some erythrinid synapomorphies but shows notable resemblance to the Acestrorhynchidae, particularly in the pattern of the replacement teeth. The Brazilian genus is included in the erythrinids.

Late Miocene Potamarchine Rodents from Southwestern Amazonia, Brazil—with Description of New Taxa

The fossil rodents from the southwestern Amazonia of Brazil have been studied since the first half of the 20th century. Several caviomorph rodents were reported for the Neogene of this region, mainly neoepiblemids and dinomyids. Until recently, the record of dinomyids in the Solimões Formation (Late Miocene) was predominantly based on a few isolated teeth, which made it difficult to make more accurate taxonomic identifications due to the scarcity of diagnostic characters. Here, new remains, more complete than those previously reported, of potamarchine dinomyids from the Neogene of Brazil are described. A new species of Potamarchus and a new genus and species of a Potamarchinae are erected. In addition, new material of Potamarchus murinus and Potamarchus sp. is identified. These data suggest a higher diversity of dinomyids in in the western Amazonia than previously supposed.

THE TOTAL STATION AS A TOOL FOR RECORDING PROVENANCE IN PALEONTOLOGY FIELDWORK: CONFIGURATION, USE, ADVANTAGES, AND DISADVANTAGES

Abstract:  Fossil data collecting is an essential stage of every paleontological undertaking. Although there is a consensus regarding the fundamental importance of sedimentary and stratigraphic context, there is still some debate surrounding the need to record the exact position of a fossil in relation to other elements within the same deposit (provenance). Here we provide a practical guide for the in-field use of the Total Station (TST, electronic equipment for xyz coordinates measurements), a tool that has seen wide application in archaeology but has been largely neglected in paleontology. With the TST, recording the provenance of in situ fossils can be done quickly and with great precision. We also present a configuration tutorial showing how to use the equipment, based on our experience in the Solimões Formation (upper Miocene, Acre basin, Brazil), highlighting both its advantages and disadvantages for recording fossil provenances.

A new rodent (Caviomorpha: Dinomyidae) from the upper Miocene of southwestern Brazilian Amazonia

Abstract Recently, the fossil record of rodents from southwestern Brazilian Amazonia has been reviewed with regards to its diversity as well as its ecological relationships. In the reviews, the necessity to report new specimens collected with stratigraphic control was stated. Here, a new dinomyid specimen collected during a 2015 expedition to the Niterói locality, Acre River, is reported. The material is a fragment of skull with the right P4–M1 and the left P4–M2 preserved. The cheek teeth are protohypsodont, a characteristic employed to differentiate Potamarchinae dinomyids from the euhypsodont dinomyids Eumegamyinae and Tetrastylinae. The occlusal surface of the cheek teeth is composed of lophs with interruptions, showing little wear, which suggests that the specimen is not fully ontogenetically developed. The specimen has a unique combination of characters (protohypsodont and pentalophodont cheek teeth, with the leading edges of similar thickness to the trailing edges, and presence of a groove on the bottom of the infraorbital foramen) not present in other known dinomyids, which led us to erect a new taxon. The abundant and diverse fossil record of protohypsodont dinomyids suggests that an important radiative event may have occurred during the middle–late Miocene of northern South America. http://zoobank.org/urn:lsid:zoobank.org:pub:E082C3C6-47B6-4D83-9009-A64879AAFC7A http://www.zoobank.org/NomenclaturalActs/16235A7B-A261-445E-8DD4-940AB21DCB06