A Late Pleistocene coastal ecosystem in French Guiana was hyperdiverse relative to today.

Warmer temperatures and higher sea level than today characterized the Last Interglacial interval [Pleistocene, 128 to 116 thousand years ago (ka)]. This period is a remarkable deep-time analog for temperature and sea-level conditions as projected for 2100 AD, yet there has been no evidence of fossil assemblages in the equatorial Atlantic. Here, we report foraminifer, metazoan (mollusks, bony fish, bryozoans, decapods, and sharks among others), and plant communities of coastal tropical marine and mangrove affinities, dating precisely from a ca. 130 to 115 ka time interval near the Equator, at Kourou, in French Guiana. These communities include ca. 230 recent species, some being endangered today and/or first recorded as fossils. The hyperdiverse Kourou mollusk assemblage suggests stronger affinities between Guianese and Caribbean coastal waters by the Last Interglacial than today, questioning the structuring role of the Amazon Plume on tropical Western Atlantic communities at the time. Grassland-dominated pollen, phytoliths, and charcoals from younger deposits in the same sections attest to a marine retreat and dryer conditions during the onset of the last glacial (ca. 110 to 50 ka), with a savanna-dominated landscape and episodes of fire. Charcoals from the last millennia suggest human presence in a mosaic of modern-like continental habitats. Our results provide key information about the ecology and biogeography of pristine Pleistocene tropical coastal ecosystems, especially relevant regarding the-widely anthropogenic-ongoing global warming.

Metals in seston from Cabo Frio Bay, a region under the influence of upwelling in SE-Brazil.

This study, performed during 2003-2005 and 2008-2009, investigated metals (Al, Fe, Ba, Zn, Mn, Cr, Cu, Ni, Cd) content in seston at Cabo Frio Bay, SE-Brazil. This study may serve as a baseline of seston metal distribution to guide biogeochemical and ecological models. The seston fractions (> 20 µm, > 64 µm, > 100 µm, and > 150 µm) were sampled in sub-surface horizontal hauls. Metals were determined by ICP-MS. The metals range: Al (62.5-56,867.6 µg g-1), Fe (23.5-25,384.0 µg g-1), Mn (2.7-336.8 µg g-1), Ba (< 0.005-356.3 µg g-1), Zn (0.5-94.2 µg g-1), Cr (0.7-35.5 µg g-1), Cu (4.3-41.7 µg g-1), Ni (< 0.005-19.1 µg g-1) and Cd (< 0.0004-2.4 µg g-1). Aluminium, Fe, Mn, Ba, and Zn showed significant differences (p < 0.05) between the seston fraction. The results obtained in this study suggest that the elements (Fe, Mn, Ba) in the seston were strongly influenced by the abiogenic source. In contrast, Zn, Cd, Cu, Cr, and Ni can be biogenic/anthropogenic sources. The significant positive linear correlation of Zn:P, Cd:P, and Cu:P can indicate an intracellular concentration higher than the external adsorption in the plankton community.

A comparative approach employing microCT for the analysis of Cenozoic foraminifera from the Brazilian carbonate equatorial platform.

Worldwide, some of the largest hydrocarbon reservoirs are located in tropical neritic carbonate deposits. Biostratigraphic and paleoenvironmental analyzes of these sedimentary records are often based on the study of foraminiferal assemblage. Foraminifera-based biozones are widely employed in the oil industry to support drilling processes that, alongside petrophysical prospecting, define interval favorable for exploiting hydrocarbon resources. Both scientific research and the petroleum industry, however, usually apply traditional petrographical and paleontological methods to analyze microfossil assemblages, especially for large benthic foraminifera. New, faster, and more accurate methods based on microCT analyzes have emerged as a valuable high-output tool to obtain high-resolution microfossil records for biostratigraphy and paleoenvironmental reconstructions. This method is also useful for the development of digital databases for artificial intelligence applications. MicroCT analyzes, therefore, lead to faster identification of foraminifera assemblage and support digital access to international foraminifera repositories and reference collections, introducing a new dimension in micropaleontological research.

Mercury distribution in water masses of the South Atlantic Ocean (24°S to 20°S), Brazilian Exclusive Economic Zone.

Mercury (Hg) is a toxic globally spread pollutant that has been found at increasing concentrations in the South Atlantic Ocean. The present work provides the first insight into the total mercury (HgT, unfiltered waters) content in the water of the Brazilian Exclusive Economic Zone (BEEZ), within a 24°S to 20°S. Water samples were collected from surface to 3400 m depth along transects, and analyzed with atomic fluorescence. The mean HgT concentration for the Tropical Water mass (TW) was 6.3 ± 1.4 pM (n = 16), for the South Atlantic Central Water (SACW), 5.9 ± 0.7 pM (n = 8), for the Antarctic Intermediate Water (AAIW), 5.0 ± 0.6 pM (n = 2), for the Upper Circumpolar Deep Water (UCDW), 6.5 pM (n = 1), and for the North Atlantic Deep Water (NADW), 5.7 ± 0.9 pM (n = 12). HgT concentrations were highest throughout the BEEZ in comparison with other parts of the Atlantic Ocean, farther from the coast.

Trace metals enrichment and potential ecological risk in sediments of the Sepetiba Bay (Rio de Janeiro, SE Brazil).

The Sepetiba Bay (SB; SE Brazil) has been severely affected by growing of urbanization and industrial activity. This work aims to analyze the evolution of contamination by metals of sediments in SB. The results show a marked increasing trend in the concentrations of potentially toxic elements (PTEs), which is consistent with the rapid populational and industrial growth, mostly since 1970 CE. The remobilization and redistribution of sediments by currents have contributed to the dispersion of metals from the main source of pollutants to relatively distant regions. "Moderately to strongly polluted" sediments are also recorded in some sites in deeper sedimentary layers (namely in preindustrial periods), probably due to lithologic sources of the sediments. The concentrations of PTEs in SB are relatively high when compared with those found globally and in other Brazilian water bodies. Samples of high-resolution sediment cores confirmed that potential ecological risk to the coastal system is influenced not only through human actions but also by natural causes.

Shark and ray diversity in the Tropical America (Neotropics)-an examination of environmental and historical factors affecting diversity.

We present the first comprehensive review of the present and past shark and ray diversity in marine waters of Tropical America, examining the patterns of distribution in the Eastern Central Pacific (EP) and Western Central Atlantic (WA) realms. We identified the major regions of diversity and of endemism, and explored the relations to physical variables. We found a strong relationship between shark and ray diversity with area and coastal length of each province. The Tropical Northwestern Atlantic Province is characterized by high diversity and greater occurrence of endemic species, suggesting this province as the hotspot of sharks and rays in Tropical America. The historical background for the current biogeography is explored and analyzed. Referential data from 67 geological units in 17 countries, from both shallow and deep-water habitats, across five time-clusters from the Miocene to the Pleistocene were studied. New data include 20 new assemblages from six countries. The most diverse Neogene and extant groups of shark and ray are Carcharhiniformes and Myliobatiformes, respectively. The differentiation between Pacific and Atlantic faunas goes to at least the middle Miocene, probably related with the increasing closure of the Central American Seaway acting as a barrier. The highest faunal similarity between the assemblages from the EP and the WA at the early Miocene could be related to the lack of a barrier back then, but increased sampling is needed to substantiate this hypothesis.

Neogene Proto-Caribbean porcupinefishes (Diodontidae).

Fossil Diodontidae in Tropical America consist mostly of isolated and fused beak-like jawbones, and tooth plate batteries. These durophagous fishes are powerful shell-crushing predators on shallow water invertebrate faunas from Neogene tropical carbonate bottom, rocky reefs and surrounding flats. We use an ontogenetic series of high-resolution micro CT of fossil and extant species to recognize external and internal morphologic characters of jaws and tooth plate batteries. We compare similar sizes of jaws and/or tooth-plates from both extant and extinct species. Here, we describe three new fossil species including †Chilomycterus exspectatus n. sp. and †Chilomycterus tyleri n. sp. from the late Miocene Gatun Formation in Panama, and †Diodon serratus n. sp. from the middle Miocene Socorro Formation in Venezuela. Fossil Diodontidae review included specimens from the Neogene Basins of the Proto-Caribbean (Brazil: Pirabas Formation; Colombia: Jimol Formation, Panama: Gatun and Tuira formations; Venezuela: Socorro and Cantaure formations). Diodon is present in both the Atlantic and Pacific oceans, whereas the distribution of Chilomycterus is highly asymmetrical with only one species in the Pacific. It seems that Diodon was as abundant in the Caribbean/Western Atlantic during the Miocene as it is there today. We analyze the paleogeographic distribution of the porcupinefishes group in Tropical America, after the complete exhumation of the Panamanian isthmus during the Pliocene.

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.

Formation of the Isthmus of Panama.

The formation of the Isthmus of Panama stands as one of the greatest natural events of the Cenozoic, driving profound biotic transformations on land and in the oceans. Some recent studies suggest that the Isthmus formed many millions of years earlier than the widely recognized age of approximately 3 million years ago (Ma), a result that if true would revolutionize our understanding of environmental, ecological, and evolutionary change across the Americas. To bring clarity to the question of when the Isthmus of Panama formed, we provide an exhaustive review and reanalysis of geological, paleontological, and molecular records. These independent lines of evidence converge upon a cohesive narrative of gradually emerging land and constricting seaways, with formation of the Isthmus of Panama sensu stricto around 2.8 Ma. The evidence used to support an older isthmus is inconclusive, and we caution against the uncritical acceptance of an isthmus before the Pliocene.

Sawfishes and Other Elasmobranch Assemblages from the Mio-Pliocene of the South Caribbean (Urumaco Sequence, Northwestern Venezuela).

The Urumaco stratigraphic sequence, western Venezuela, preserves a variety of paleoenvironments that include terrestrial, riverine, lacustrine and marine facies. A wide range of fossil vertebrates associated with these facies supports the hypothesis of an estuary in that geographic area connected with a hydrographic system that flowed from western Amazonia up to the Proto-Caribbean Sea during the Miocene. Here the elasmobranch assemblages of the middle Miocene to middle Pliocene section of the Urumaco sequence (Socorro, Urumaco and Codore formations) are described. Based on new findings, we document at least 21 taxa of the Lamniformes, Carcharhiniformes, Myliobatiformes and Rajiformes, and describe a new carcharhiniform species (†Carcharhinus caquetius sp. nov.). Moreover, the Urumaco Formation has a high number of well-preserved fossil Pristis rostra, for which we provide a detailed taxonomic revision, and referral in the context of the global Miocene record of Pristis as well as extant species. Using the habitat preference of the living representatives, we hypothesize that the fossil chondrichthyan assemblages from the Urumaco sequence are evidence for marine shallow waters and estuarine habitats.

Palaeontological evidence for the last temporal occurrence of the ancient western Amazonian river outflow into the Caribbean.

Fossil catfishes from fluvio-lacustrine facies of late Miocene Urumaco, early Pliocene Castilletes and late Pliocene San Gregorio formations provide evidence of a hydrographic connection in what is today desert regions of northern Colombia and Venezuela. New discoveries and reevaluation of existing materials leads to the recognition of two new records of the pimelodid Brachyplatystoma cf. vaillantii, and of three distinct doradid taxa: Doraops sp., Rhinodoras sp., and an unidentified third form. The presence of fossil goliath long-whiskered catfishes and thorny catfishes are indicative of the persistence of a fluvial drainage system inflow into the South Caribbean during the Pliocene/Pleistocene boundary, complementary to the previous western Amazonian hydrographic system described from the Middle Miocene Villavieja Formation in central Colombia and Late Miocene Urumaco Formation in northwestern Venezuela. The Pliocene Castilletes and San Gregorio formations potentially represent the last lithostratigraphic units related with an ancient western Amazonian fish fauna and that drainage system in the Caribbean. Alternatively, it may preserve faunas from a smaller, peripheral river basin that was cut off earlier from the Amazon-Orinoco, today found in the Maracaibo basin and the Magdalena Rivers.

The anatomy of the world's largest extinct rodent.

Phoberomys is reported to be the largest rodent that ever existed, although it has been known only from isolated teeth and fragmentary postcranial bones. An exceptionally complete skeleton of Phoberomys pattersoni was discovered in a rich locality of fossil vertebrates in the Upper Miocene of Venezuela. Reliable body mass estimates yield approximately 700 kilograms, more than 10 times the mass of the largest living rodent, the capybara. With Phoberomys, Rodentia becomes one of the mammalian orders with the largest size range, second only to diprotodontian marsupials. Several postcranial features support an evolutionary relationship of Phoberomys with pakaranas from the South American rodent radiation. The associated fossil fauna is diverse and suggests that Phoberomys lived in marginal lagoons and wetlands.