The paleoceanographic dynamics in the Southwestern Atlantic Ocean is still poorly understood, with most studies describing the last 25 ky. In the present study, the coccolithophore assemblages from a sediment core from the Brazilian continental margin (20º01’S) were analysedduring the interval between 423-305 ky (Marine Isotopic Stages – MIS – 11 to 9), including the important Mid-Brunhes Event (MBE). The coccolithophore assemblage is typically tropical: Gephyrocapsa spp. and Florisphaera profunda dominate the assemblage. The productivity (measured by the N ratio) was high throughout the entire studied interval, pointing to a shallow nutricline, induced by the northeast winds of the South Atlantic Subtropical High or by upwelling development. The coccolith numbers was low during almost all the studied interval, since this group is adapted to oligotrophic environments. However, between 420-410 ky, both coccolith numbers and N ratio were high, which may indicate the lack of silicate in the surface waters (reducing the diatom competitiveness). Globally, the MBE is marked by a high production of carbonate and the dominance of Gephyrocapsa caribbeanica in the coccolithophore assemblages. In this work, this dominance was recognized between 420-328 ky (MIS 11-9). Besides the high production of carbonate, the MBE is also globally marked by a great dissolution (Mid-Brunhes Dissolution Interval), but no significant carbonate dissolution was found in this work.
New data from the palynomorph assemblage with angiosperm pollen grains found in lacustrine sediments belonging to the terminal part of the D-129 Formation are herein presented. The fossiliferous section is included in the uppermost part of a thick lacustrine stratigraphic unit, which is widely distributed in the subsurface of the productive San Jorge Gulf Basin. The presence of the paleoequatorial marker Tucanopollis crisopolensis (Regali) in the studied sediments is emphasized and biostratigraphic as well as biogeographic aspects are discussed. Based on the information provided by the fossil record, a late Barremian?/early Aptian age is suggested for the end of the great-lake episode in the present district.
This work reconstructs Late Quaternary paleoceanographic changes in the western South Atlantic Ocean based on sedimentary core GL-77, recovered from the lower continental slope in the Campos basin, offshore SE Brazil. The studied interval comprises the last 130 ka. Changes in sea surface temperature (SST) and paleoproductivity were estimated using the total planktonic foraminiferal fauna and oxygen isotope analyses. The age model was based on the oxygen isotope record, biostratigraphic datums and AMS C-14 dating. It was observed that the Pleistocene/Holocene transition occurs within Globorotalia menardii Biozone Y, and is not coeval with the base of Biozone Z. The range between summer and winter SST estimates is larger during the glacial period compared to interglacials. Three peaks of low SST around 70, 50-45 and 20 ka coincided with periods of enhanced SE trade winds. Despite faunal differences between the last interglacial (MIS 5e) and the Holocene, our SST estimates suggest that SSTs did not differ significantly between these intervals.
In this work, fossil assemblages of coccolithophorids, oxygen stable isotopes (Globigerinoides ruber), and radiocarbon dating were used as proxies. The sediment core, obtained on the slope of Campos Basin, was analyzed, comprising the last 130 kyr. The results show that placolith-bearing taxa, such as Gephyrocapsa spp. and Emilianiahuxleyi, as well as Florisphaera profunda, which inhabits the lower photic zone, dominated the assemblage during the whole study interval. Over the past 130 kyr, there was a relationship between productivity (based on N ratio) and climate cyclicity. In a general way, it can be said that sensu strict interglacial stages (ME 5e and the Holocene) showed low productivity, while the others (MIS 5d-a, 4, 3 and 2) had large fluctuations. During interglacial-like conditions, a northward shift in the Intertropical Convergence Zone position would take place, along with a weakening of the NE winds associated with the Southern Atlantic Subtropical High and a weakening of the Brazil Current, leading to the maintenance of the water stratification. On the other hand, during glacial-like conditions, the inverse conditions would be favorable to a shallower nutricline, increasing productivity in surface waters. Maximum productivity is achieved between 14-6.5 ky (during deglaciation), which could be a reflection of the events of the Last Glacial Maximum.
The presence of the extinct sloth Megatherium americanum Cuvier in Pleistocene deposits of the Coastal Plain of the State
of Rio Grande do Sul, southern Brazil, has been mentioned by several authors for decades, but formal descriptions of skeletal elements
with unambiguous diagnostic features have never been published. The recent description of one dentary of the megatheriid Eremotherium
laurillardi Lund from deposits in this area raised doubts about the taxonomic affinity of the materials assigned to M. americanum. The present
work confirms the presence of the latter in the coastal plain of the state of Rio Grande do Sul (Santa Vitória do Palmar County), from a partial
skull collected in fluvial deposits of the Santa Vitória Formation exposed on the banks of the Chuí Creek, plus an incomplete dentary, one
tibia, one astragalus found on the shoreline, and another tibia with the fibula fused proximally and distally retrieved from the bottom of the
continental shelf by the research vessel “Atlântico Sul”. The fossils of both species of megatheriid sloths were found in the same deposits
of Rio Grande do Sul (Chuí Creek in the coastal plain and Pessegueiro Creek in the central area of the state), which is remarkable given that
E. laurillardi is known mostly from the intertropical Americas, whereas M. americanum is restricted to the subtropical-temperate regions
of South America. Such co-occurrence could indicate that both species were sympatric or be related to the mixing by fluvial processes of
remains of animals that occupied the same areas at distinct times due to periodic latitudinal shifts of the climatic belts.
SYSTEMATIC AND TAXONOMIC REVISION OF THE GENUS SCELIDOTHERIUM OWEN, 1839 (XENARTHRA, PHYLLOPHAGA, MYLODONTIDAE). The subfamily Scelidotheriinae (Xenarthra, Phyllophaga, Mylodontidae) has been recorded since the "Friasian" sensu lato (middle Miocene) to Lujanian (late Pleistocene-early Holocene). For the Quaternary four genera: Scelidotherium, Valgipes, Scelidodon and Catonyx are recognized and recorded in Argentina, Bolivia, Chile, Ecuador, Peru and Uruguay. The authors performed a systematic and taxonomic study of the genus Scelidotherium Owen of Argentina. Two valid species are recognized: (i) S. bravardi Lydekker presents records in the provinces of Buenos Aires during the Ensenadan (ca. 1 My - 0.4 My BP; early Pleistocene-middle Pleistocene) and in the Pleistocene of the province of San Luis, and (ii) S. leptocephalum Owen presents records during Bonaerian and Lujanian (ca. 0.4 My - 8.5 ky BP; middle Pleistocene-early Holocene) in the Province of Buenos Aires, in the Lujanian of the provinces of Cordoba, Corrientes, Salta y Formosa; outside Argentine territory S. leptocephalum is recorded in the late Pleistocene of Uruguay. RESUMO - A subfamilia Scelidotheriinae (Xenarthra, Phyllophaga, Mylodontidae) e registrada do "Friasense" s.l. (Mioceno medio) ao Lujanense (Pleistoceno fi nal-Holoceno inicial). Para o Quaternario sao reconhecidos e registrados quatro generos: Scelidotherium, Valgipes, Scelidodon e Catonyx, na Argentina, Bolivia, Chile, Equador, Peru e Uruguai. Realiza-se um estudo sistematico e taxonomico do genero Scelidotherium Owen da Argentina. Sao reconhecidas duas especies validas: (i) S. bravardi Lydekker possui registros nas provincias de Buenos Aires durante o Ensenadense (ca. 1 Ma - 0,4 Ma AP; Pleistoceno inicial-Pleistoceno medio) e no Pleistoceno de San Luis; e (ii) S. leptocephalum Owen apresenta registros durante o Bonaerense e Lujanense (0,4 Ma - 8,5 ka AP; Pleistoceno medio-Holoceno inicial) da Provincia de Buenos Aires; no Lujanense das provincias de Cordoba, Corrientes, Salta e Formosa; fora do territorio argentino S. leptocephalum se registra no Pleistoceno fi nal do Uruguai. Palavras-chave: preguicas, America do Sul, Quaternario, sistematica, taxonomia.
In the Brazilian intertropical region, fossils of megafauna occur in tanks and caves. The occurrence of four taxa has been described for a tank in the locality of Fazenda Charco, Sergipe State, and these are: Eremotherium laurillardi (Lund, 1842) (Megatheriidae), Stegomastodon waringi (Holand, 1920) (Gomphotheriidae), Palaeolama major Liais, 1872 (Camelidae) and Toxodontinae (Toxodontidae). With the collection of new material and the review of already existing material from this locality, it was possible to determine the presence of an additional representative of megafauna, namely a sloth of medium size, Catonyx cuvieri. The giant mammal species of the Brazilian intertropical region are generally attributed to the Late Pleistocene, but the occurrence of fauna found in this region could have extended to the beginning of the Holocene.
EQUUS (AMERHIPPUS) NEOGAEUS LUND, 1840 (PERISSODACTYLA, EQUIDAE) FROM THE QUATERNARY OF PARANÁ STATE, BRAZIL. The fossil record of Equidae in southern Brazil is restricted to Rio Grande do Sul State and is represented by isolated teeth and fragmentary cranial and postcranial remains. This paper describes Equus (Amerhippus) neogaeus Lund from Paraná State, where Pleistocene mammals are poorly known. The material is a left dentary with cheek teeth and was found in the Mangueirinha Municipality in a small alluvial terrace, associated with some remains of Gomphoteriidae and Megatheriidae. The presence of E. (A.) neogaeus suggests an open paleoenvironment with xerofitic vegetation, and could indicate a Lujan Age/Stage (late Pleistocene/early Holocene) for the assemblage fauna. Key words: Quaternary, megafauna, south of Brazil, holartic ungulate. RESUMO – O registro fóssil de Equidae para a região sul do Brasil está restrito ao Estado do Rio Grande do Sul, representado por material fragmentário e dentes isolados. Este trabalho descreve Equus (Amerhippus) neogaeus Lund para o Quaternário do Estado do Paraná, onde os mamíferos pleistocênicos são pobremente conhecidos. O material está representado por um dentário esquerdo incompleto com toda a série molariforme, procedente do Município de Mangueirinha, e foi encontrado em um pequeno terraço aluvionar associado a alguns ossos e dentes de Gomphotheriidae e Megatheriidae. E. (A.) neogaeus sugere paleoambiente aberto com vegetação xerofítica, sendo que sua presença poderia indicar uma Idade/Piso Lujanense (Pleistoceno superior-Holoceno inferior) para a assembleia. Palavras-chave: Quaternário, megafauna, sul do Brasil, ungulado holártico.
Carcharocles megalodon is considered a macropredatory shark that inhabited the seas around the world from middle Miocene to late Pliocene. In Argentina, it has only been formally recorded at two localities. Here, we report the first record for this taxon in the Buenos Aires Province. This occurrence is based on an isolated tooth recovered on the beach at the Punta Médanos locality, which lacks clear stratigraphic context. Based on the regional geology, the specimen probably came from Pliocene beds. Its size indicates that it probably belongs to a juvenile individual. Keywords: Carcharocles megalodon, macropredatory shark, fossil teeth, Mar de Ajó.
Glyptodon tuberculatus Owen was erected on two carapace fragments. Later, it was gave identity to that species through more detailed descriptions and established that it should pertain to the new genus Panochthus Burmeister. In this way, the descriptions, figures, and photographs published by Burmeister, mainly in 1870, were consistently followed by other authors when discussing or listing Panochthus tuberculatus (Owen). As the holotype of the latter species was lost, Zamorano and collaborators assigned a neotype for it, identified as MLP 16-29. For these authors, the elements included in MLP 16-29, are attributable to a single individual and comprise an exo and endoskeleton from Tapalque (Buenos Aires Province, Argentina). However, a detailed historical study of these elements incorporated to the neotype and a detailed comparative anatomical study of them, shows that under the collection number MLP 16-29 more than one individual is represented. Finally, some of these same anatomical elements do not match the characteristics traditionally described for P. tuberculatus. Consequently, the neotype proposed is not available under the current rules of the International Code of Zoological Nomenclature.
‘Venericardia’ patagonica is one of the most common bivalve species represented in the late Oligocene-middle Miocene of Patagonia. Previous authors recognized two contrasting morphologies within this species based on sculpture and outline. An Elliptic Fourier Analysis was performed, using the anterior view of 95 specimens. A Principal Component Analysis was carried out with the Fourier coefficients. The results show two well differentiated groups, based on development of the convexity, each of which could correspond to the mature male and female, as is proposed for other carditids. The females have more bulky shells, with maximum convexity at the centre of valves. The males have less bulky shells, with a sharp ventral edge. These differences correlate with sculpture (more pronounced in males) and size of specimens (larger in females).
A morphological revision of the type species of the genus Pygocephalus Huxley, P. cooperi Huxley, brought out not only its redefinition but also the emend of the diagnosis of Pygocephalus and the family Pygocephalidae. Previous works about this genus and related taxa are discussed, as well as the problem involved in the reconstruction of fossil species of Eumalacostraca based on isolate parts.
In the Recôncavo Basin, Bahia State, Samuel Allport and latter Charles F. Hartt collected several fossils, being some of them attributed to reptile teeth. Based on the morphotypes of these teeth Othniel C. Marsh nominated two species, the first with “delicately wrinkled surface” as Crocodylus hartti (currently Sarcosuchus hartti), and the second based on teeth with “strong continuous striae, and coarse riblets” as Thoracosaurus bahiensis, this latter will be the focus of this work. Marsh did not designate any holotype and, thus, the five teeth collected and described by Allport became the type series and subsequently the syntypes of the species. However, these are currently lost. Comparing the diagnoses of T. bahiensis with the type species of the genus and with others crocodyliformes as well as spinosaurids, we noted that the supposed autapomorphy of the species is highly variable. Therefore, we propose that T. bahiensis should be considered as nomen dubium.
Until recently, one well-characterized Pleistocene genus of the subfamily Glyptodontinae (Glyptodon ca. 1.08-0.0011 My) was recognized in South America. In recent times, some authors have demonstrated, through the re-analysis of material originally classified as Glyptodon Owen and Hoplophorus Lund, the presence of a second species belonging to the North American glyptodontine Glyptotherium Osborn (ca. 58-12 ky BP), currently known from in Venezuela and Brazil. This situation implies the need for a new study, with modern taxonomical criteria, of those materials belonging to the Glyptodontinae, particularly in those territories where the knowledge of these taxa is scarce. Presented here is a new analysis of the Pleistocene Glyptodontidae from Colombia, including some taxonomic and paleobiogeographic remarks. The results show that the only reported Glyptodontidae specimens in Colombia belong to Glyptodon sp. In turn, the evidence suggests that only one single species of Glyptotherium is present in South America, currently assigned to Glyptotherium cf. Gl. cylindricum. However, a more accurate analysis is necessary to confirm or refute this taxonomic identification. To date, Glyptotherium present has been found only in an area parallel to the Caribbean Sea and the Atlantic Ocean (northern Venezuela and eastern Brazil), up to 20 S, and is always linked to lowlands. This geographic distribution agrees with the proposition of an eastern corridor during the Great American Biotic Interchange. Below this latitude, the only recorded glyptodontine corresponds to Glyptodon, which is also recorded in a strip parallel to the Cordillera de Los Andes reaching Colombia and Venezuela. Taking into account this distribution, the presence of this genus in Central America cannot be discarded.
This paper documents the occurrence of Ophthalmoplax brasiliana, the first fossil crab in the Potiguar Basin based on an adult male specimen collected in the outcrop of the Jandaíra Formation (Campanian). The material was obtained from the carbonatic layers of the Upper Cretaceous near the city of Apodi, west of the State of Rio Grande do Norte. This is probably the oldest record of this species in the Americas and a contribution to the knowledge of the paleobiogeography of this taxonomic group.
Eobrasilia coutoi Simpson, 1947, is currently considered to be one of the most enigmatic metatherian mammals of Itaboraí Basin, Brazil. A single badly broken and incomplete skull, with a single strongly worn M3, and an associated fragmentary dentary are the elements currently attributed to this taxon. This fragmentary condition contributes for its uncertain position within Metatheria. Herein, the preserved dental morphology of this species is re-analyzed. The morphology of these structures, such as a tiny, obliquely oriented, one-rooted P1; absence of retro-premolar spaces between the premolars and mesiodistally developed p3, supports the assignment of Eobrasilia as a South American stagodontid. This new result leads a systematic review of the affinities of “Eobrasiliinae”, currently represented by Eobrasilia, Gaylordia and Didelphopsis. The hypothesis that “Eobrasiliinae” represents a valid taxon is refuted in the phylogenetic analysis, which recovered Eobrasilia as more closely related to Didelphodon within Stagodontidae, Gaylordia as the sister taxon of Tiulordia and more closely related to Minusculodelphis and Marmosopsis, and Didelphopsis as the sister taxon of Itaboraidelphys and more closely related to Herpetotherium, Carolopaulacoutoia and Derorhynchus. The shared characters between Eobrasilia, Gaylordia and Didelphopsis were likely a result of convergent evolution, as these three lineages independently adapted to more durophagous diets. The phylogenetic analysis did not support the sister relation between Fumodelphodon and Didelphodon and Eodelphis and Hoodootherium. The grouping of Eobrasilia and Didelphodon corroborates the previous hypothesis that Metatheria dispersed from North to South America during the Late Cretaceous.
A new cordaitalean pollen species of Cladaitina Maheshwari & Meyen, namely Cladaitina veteadensis is described from the Upper Permian strata of Argentina. The morphology of these dispersed pollen grains were studied using light and scanning electron microscopy. Detailed comparisons are made with similar commonly recorded sporae dispersae incertae sedis forms mainly recorded from other Late Permian palynofloras elsewhere. Cladaitina veteadensis sp. nov. constitutes a characteristic and common component of a rich palynological assemblage found in the upper part of the La Veteada Formation, Famatina Range, La Rioja province, central-western Argentina. More than 40 genera of pollen grains, spores, algae and fungi were recognized in this assemblage that they collectively suggest a latest Permian age. The presence of the genus Cladaitina in Argentina can be considered as a first evidence of the occurrence of Rufloriaceae in Gondwana.
ASSIGNABLE MATERIAL TO EPACHTHOSAURUS POWELL, 1990 (SAUROPODA: TITANOSAURIA), FROM THE BAJO BARREAL FORMATION, UPPER CRETACEOUS, CHUBUT, ARGENTINA. This paper describes materials recovered from levels of the Bajo Barreal Formation (Upper Cretaceous) of Ranch Ocho Hermanos outcrops, Patagonia, Argentina. The materials include an anterior dorsal vertebra and pelvic elements. The large sized dorsal vertebra is assigned to the taxon Epachthosaurus based on the following diagnostic characters which are autapomorphic for the above mentioned taxon: strongly developed intraprezygapophyseal lamina, accessory articular processes extending ventrolaterally from the hyposphene, and aliform processes which project laterally from the dorsal margin of the spinodiapophyseal lamina. The incomplete sacrum has five sacral vertebrae and a portion of the right ilium and pubis. These materials are included within Titanosauria and tentatively pertain to Epachthosaurus. The study of the above mentioned materials is important because it increases our knowledge of the relative abundance of the taxon Epachthosaurus in Ocho Hermanos ranch outcrops. Furthermore, we propose a set of characters which allow the expansion of the generic diagnosis of Epachthosaurus.
Here we present a skull and a lower jaw of a temnospondyl specimen collected from the São Jerônimo da Serra Site, an exposure of the Morro Pelado Member of the Rio do Rasto Formation (Middle/Upper Permian, Paraná Basin), Paraná State of southern Brazil. The sedimentary environment in which the fossil was preserved is characterized by a massive reddish mudstone derived from the slow deposition of fine sediments from suspended load in a terminal splay or ephemeral lake setting. The comparative anatomical description of the new specimen allows its assignment to the rhinesuchid Australerpeton cosgriffi Barberena. The new specimen represents the most complete skull and lower jaw of this species found up to date. Its high degree of ossification associated with its large skull size (58 cm long) indicates that it was a mature adult. This work, besides confirming several anatomical characteristics of A. cosgriffi, reveals previously unknown information about this species: a long cultriform process whose anterior edge surpasses the level of the posterior border of the choanas, being interposed between them; and a pair of longitudinal ridges lacking denticles that run parallel along the premaxillary surface without making contact with the choanae. These features were not reported before in the smaller known skulls of A. cosgriffi because they likely develop late in the ontogeny of this species. This new find provides evidence that this unique long-snouted rhinesuchid was a common and successful faunal component of the Middle-Late Permian fluvio/lacustrine ecosystems of southern Brazil, and reaffirms the Rio do Rasto Formation of Brazil as a rich source of information concerning the initial diversification of the Stereospondyli.
ABSTRACT – VEGETATION CHANGES OF LAGUNA MERÍN BASIN, URUGUAY, DURING THE LAST CA. 2000
CAL. YR BP. The palynological analysis from a sedimentary sequence from the wetland Paso Barranca-India Muerta at Laguna Merín Basin (RB1 core, 33°40’36”S-53°49’15”W) of southeastern Uruguay, allowed to reconstruct the vegetation history during the last ca. 2000 cal. yr BP. The modern pollen-vegetation relationship from Laguna Merín Basin at regional scale was used for the interpretation of RB1 fossil record. Results revealed that during the late Holocene grassland vegetation dominated at Paso Barranca-India Muerta, together with the development of riparian forests, palm grooves and freshwater marshes. This suggests a diverse vegetation on the area under either humid climatic conditions or a positive water balance. However, the freshwater marsh showed fl uctuations in depth and extent, probably as a response to local soil water content changes. Since ca. 2000 cal. yr BP the marsh water level changes displayed variability, with increased levels at ca. 700 cal.
yr BP. Thereafter, conditions remained relatively steady until ca. 300 cal. yr BP, when the marsh water level progressively increased until reaching the current conditions. The local soil water content changes would have responded to the late Holocene climate variability suggested for southeastern Uruguay, even under humid conditions proposed for the campos region of the Río de la Plata grasslands. The vegetation changes inferred from the palynological analysis could not be related to the anthropogenic changes introduced by the prehispanic populations in the region. This work substantially improves our knowledge of the late Holocene vegetation and climate conditions in the Laguna Merín Basin.
Biostratigraphic results obtained with a systematic study of the planktic foraminiferal assemblages recovered from Upper Cretaceous-Lower Paleogene strata (Turonian? to early Danian in age) of Deep Sea Drilling Program (DSDP) Site 356, Sao Paulo Plateau, are presented and discussed herein. Fifty-nine planktic foraminiferal species were identified within the studied interval, enabling the identification of 11 planktic foraminiferal zones (Turonian? to early Danian in age): Marginotruncana schneegansi, Dicarinella concavata, Dicarinella asymetrica, Globotruncanita elevata, Contusotruncana plummerae, Radotruncana calcarata, Globotruncanella havanensis, Pseudoguembelina palpebra, Abathomphalus mayaroensis, Pseudoguembelina hariaensis and Pa. An unconformity spanning at least 0.96 Ma could also be suggested within core 31 (Maastrichtian in age), due to the absence of the Racemiguembelina fructicosa Interval Zone from the studied section. High sedimentation rates were estimated within the Santonian (Dicarinella asymentrica Total-range Zone) and the uppermost Maastrichtian (Pseudoguembelina hariaensis Interval Zone) of DSDP site 356, while lower and more constant values were suggested for the Campanian-lower Maastrichtian interval (Globotruncanita elevata Partial-range Zone to Pseudoguembelina palpebra Interval Zone). The reliability in identifying the Contusotruncana plummerae Interval Zone (Campanian in age) in Cretaceous sections of the South Atlantic Ocean is confirmed herein.
We present the sigmodontine assemblage from lower and middle Holocene recorded in the archaeological site RS-TQ-58: Afonso Garivaldino Rodrigues (County of Brochier, State of Rio Grande do Sul). A total of 16 species are detected from the study of 572 specimens, about half of which belonging to the tribe Akodontini. The assemblage recorded include species which typically inhabit open areas (e.g. Calomys sp., Gyldenstolpia sp., Kunsia tomentosus) and also several considered as forest dewellers (e.g. Delomys sp., Juliomys sp., Sooretamys angouya). Necromys obscurus, a sigmodontine today restricted to Central Argentina and Southern Uruguay, is abundantly recorded in Garivaldino and reported for the first time to the Quaternary from Brazil. Thaptomys nigrita and Wilfredomys oenax have in Garivaldino their first records to the Holocene from Rio Grande do Sul State. Compared to the recent assemblage of sigmodontine rodents recorded in Rio Grande do Sul, Pseudoryzomys simplex, K. tomentosus, N. obscurus and Gyldenstolpia sp. became regionally extinct. The sigmodontine assemblage detected in Garivaldino is richest than a previously studied one from Pilger site. The evidence of both sites reflects changes in the species composition, which can be linked with a progressive transformation of the general landscape from mostly open grasslands to forests.
Aalenian-Bajocian benthic foraminiferal and ostracode assemblages of the Dalichai Formation (lithologic unit III) at Telma-Dareh, Alborz Mountains (northern Iran) are presented herein. Twenty-four foraminiferal taxa were identified, with the genera Reinholdella, Epistomina and Lenticulina as the dominant taxa. The dominance of r-selected strategists among foraminifera suggests the occurrence of stressing paleoenvironmental conditions, probably related to bottom-water oxygen levels, during the deposition of the studied strata. The foraminiferal assemblages studied herein are similar to other Boreal ones in paleobiogeographic terms. The ostracode assemblages present low abundance, low species richness and poor preservation, which did not allow any identification at species level. A possible record of Majungaella is briefly discussed due to its paleozoogeographic significance. Cytherella, Paracypris and Pontocyprella are the richest genera with two species each.
SYSTEMATIC POSITION OF AKODON (ABROTHRIX) KERMACKI AND A. (AB.) MAGNUS (RODENTIA, CRICETIDAE) FROM THE PLIO-PLEISTOCENE OF SOUTHEASTERN BUENOS AIRES, ARGENTINA. The taxonomic status of the fossil sigmodontine rodents Akodon (Abrothrix) kermacki Reig 1978 and A. (Ab.) magnus Reig 1987 (Plio- Pleistocene, Buenos Aires Province) was revised. Based on molar morphology and other cranial traits of the type specimens, and considering the current defi nition of the Abrotrichini, we suggest that both taxa are not member of this tribe. These fossil forms are preliminarily referred to Akodontini, pending of further studies for a fi nal taxonomic identity. In addition, some biogeographical considerations about the Abrotrichini evolution based on this new taxonomic scenario are presented.
PAST SPECIES DISTRIBUTION MODELING: A PROMISING APPROACH IN PALEOECOLOGY. Paleoecological studies are based on fossil records, which often have spatial and temporal gaps, making the analysis of past biotas more difficult, or even impossible. Thus, Species Distribution Models (SDMs) may be useful tools to complement the available information on the geographical distribution of species over time, and have been applied to many different paleoecological questions involving fossil data and paleoclimatic simulations. This paper presents a review of SDMs applied to paleoecological questions, showing how to build and evaluate these models using fossil data, as well as discussing important issues about their assumptions, uncertainties, and challenges. Moreover, it is illustrate the applicability of SDMs to paleoecological studies by discussing the extinction dynamics of Smilodon populator Lund based on the modeling of their geographic distribution over the last 126 ky BP.
A possible episode of coevolution between galling insects and plants is reported. It was identified by a high infestation (density) of fossil gall found on the compressed Dicroidium Flora from the Triassic (Ladinian-Carnian) Passo das Tropas Member, Santa Maria Formation, Paraná Basin. The galls were found on phytofossils in 2.2 m thick mudstones with horizontal lamination, intercalated between coarse and medium-grained sandstones with clasts and cross-lamination at the base and top of the section. The associations were identified with a stereomicroscope, after which they were quantified within each botanical group, along with their type, in order to calculate the average number of galls per leaf (density). The overall density found was 4.018. Corystospermales was the predominant botanical group (87.81%), with a gall density of 4.281, followed by Ginkgoales, Equisetales, and Incertae sedis. Current ecological studies indicate that a xerophytic paleoenvironment correlates with high infestations of galling insects. However, many taphonomic, biological, and ecological factors may be involved, resulting in different hypotheses from the same data. On the other hand, they support the interpretations of this record in other aspects discussed. Furthermore, the identified gall density can be interpreted from a paleobiogeographical perspective, showing dispersion at low altitudes and intermediate subtropical latitudes (25° to 38° S or N).
ABSTRACT – NEW WOOD RECORDS OF THE MIOCENE OF THE SOLIMÕES FORMATION, ACRE BASIN, AMAZONIA, BRAZIL.
New fossil wood records associated to the families Lecythidaceae, Calophyllaceae, Combretaceae and Arecaceae for the Miocene of the
Solimões Formation, Acre Basin, Brazil, are described. The specimens have been collected on the banks of the Juruá and Envira rivers. The
main anatomical characters that allowed relating the specimens to these families are tangential diameter and distribution of vessels per mm2,
parenchyma type, intravascular pits and types and sizes of rays. It is the first record of Carinianoxylon brasiliense Selmeier, Calophyloxylon
eoionophyllum Prakash and Awasthi, Terminalioxylon erichensii Mussa and Palmoxylon Schenk for formation; in addition, a new species
for the genus Lecythioxylon Milanez is described. Systematic comparisons have been made with the other fossil records of these families in
other Gondwana formations. The paleoflora of the Solimões Formation analyzed here shows a great richness of taxonomic groups, reason
why this work provides new and important data for the knowledge of the paleoflora of the Amazon region.
Detailed descriptions are provided for specimens of a new genus and species of Mimosoideae and Swartzioxylon naraense Delteil-Desneux emended (Papilionoideae) from the Solimões Formation, Miocene, Acre Basin, Brazil. Anatomical characteristics of the woods show a resemblance with the extant genera Zygia P. Browne and Swartzia Schreb, respectively. These genera currently have a wide distribution in Brazil and throughout the Amazon region; their presence in the outcrops of the Solimões Formation supports the idea that these genera might have been important components and indicates their importance in the fossil record, both to establish its distribution and evolution from the past to present of Amazon flora.
A taxonomic review of Miocene gastropods from the Solimões Formation, Acre Basin, Brazil, from specimens collected at Cachoeira do Bandeira, Oriente, and an outcrop named Spot 04, is here presented. Three ampullariid species (Pomacea maculata, P.planorbula, Pomacea sp.), one thiarid species (Aylacostoma sp.), and one cochliopid species (Sioliella sp.) are identified for these deposits. These gastropod are known to occur in freshwaters environments, thus consolidating the hypothesis of a non-influence of brackish water on the upper Miocene deposits of the Acre Basin. The previous identification of P. maculata and Aylacostoma sp. is changed here considering biometrical analyses and shell morphological descriptions. The first report of Sioliella in this basin increases the gastropod fauna known for these strata and expands the range of this genus. Keywords: Pomacea, Aylacostoma, Sioliella, Ampullariidae, Thiaridae, Cochliopidae.
The Solimoes Formation (lower Eocene-Pliocene), southwestern Brazilian Amazonia, is one of the most abundant deposits of reptiles from the Cenozoic of Brazil. Eight species of Crocodylia have been described from this formation, including taxa of all the three main extant clades: Gavialoidea (Gryposuchus and Hesperogavialis), Alligatoroidea (Caiman, Mourasuchus and Purussaurus) and Crocodyloidea (Charactosuchus). Here, we describe crocodylian fossil remains collected in 1974 by RadamBrasil Project. Specimens were described and identified to the possible lowermost systematic level. With the exception of the osteoderms, the associated postcranial elements were not identified. It is concluded that at least in one location there may have been co-occurrence of four different morphotypes (Gavialoidea indet., Purussaurus sp., Mourasuchus sp. and taxa of the Brevirostres Glade, but not pertaining to Purussaurus or Mourasuchus), suggesting that they could have been contemporaneous, with habitat and niche partitioning.
In order to determine modern analogues for fossil pollen sequences associated with archaeological sites in the lower Colorado river basin (southwest of Buenos Aires Province), the modern pollen-vegetation-climate relationships were evaluated. The study conducted through vegetation samples, pollen percentage diagrams and cluster analysis included surface samples, located at the northern and southern parts of the basin. Six plant communities (halophyte steppe, xerophytic woodland, grassland with xerophytic woodland elements, ruderal, halophiles/gramineous grassland and hydrophytic) were determined. The pollen spectrum was dominated by Chenopodiaceae, Asteraceae, Brassicaceae and Poaceae families. Most of the vegetation and pollen reflected the local communities as part of the Espinal Province (Calden District), recording a greater influence from the Pampean region (Pampas grassland-Espinal ecotone) under sub humid-dry weather at north of the basin, and greater influence with the Monte Province (Monte-Espinal ecotone), linked to semi-arid climatic conditions to the south. Non-pollen microfossils (spores of fungi and algae) and taphonomic analysis complemented the study.