Papers by Cristina Bertoni Machado
Preliminary results on the magnetostratigraphy of three Neogene formations from SW Uruguay are pr... more Preliminary results on the magnetostratigraphy of three Neogene formations from SW Uruguay are presented: Camacho, Raigón and Libertad, and a relative age from the record of reversions in the Earth's magnetic field polarity is proposed. The sediments outcrop in the SW region of Uruguay,and have been received attention due to their fossil contents. The oldest is the late Miocene-Pliocene Camacho
<p>Abbreviations: <b>ac,</b> acetabule; <b>ilba</b>, iliac blade; &... more <p>Abbreviations: <b>ac,</b> acetabule; <b>ilba</b>, iliac blade; <b>prap</b>, pre-acetabular process; <b>poap</b>, post-acetabular process; <b>sar</b>, supra-acetabular crest; <b>sacr,</b> supra-acetabular ridge. Scale: 5cm.</p
Journal of South American Earth Sciences, 2008
... The burrows are the only evidence of vertebrate burrows from the Mesozoic of Rio ... Body fos... more ... The burrows are the only evidence of vertebrate burrows from the Mesozoic of Rio ... Body fossils are unknown to the Guará Formation, consequently the chance preservation of these tracks provides unique evidence of widespread dinosaurs activity in southern Brazil during the ...
FIG. 3. — UFRGS-PV1121T detail of the last lower postcanine in buccal (A) and lingual (B) views. ... more FIG. 3. — UFRGS-PV1121T detail of the last lower postcanine in buccal (A) and lingual (B) views. Abbreviations: aac, anterior accessory cusp; alc, anterior lingual cusp; cc, cingular cusp; ccr, cingular crest; mc, main cusp; pac, posterior accessory cusp. Scale bar: 1 mm.
FIG. 4. — Lower postcanines of sectorial toothed cynodonts: A-C, in lateral (above) and occlusal ... more FIG. 4. — Lower postcanines of sectorial toothed cynodonts: A-C, in lateral (above) and occlusal (below) views; D-I, in lingual view; A, Chiniquodon; B, Therioherpeton; C, Charruodon; D, Riograndia; E, Chaliminia; F, Irajatherium; G, Prozostrodon; H, Brasilitherium; I, Probainognathus (juvenile); A, B, C, from Abdala & Ribeiro (2000); D, from Soares (2004); E, from Martinelli & Rougier (2007); F, from Martinelli et al. (2005); G, from Bonaparte & Barberena (2001); H, from Bonaparte et al. (2003); I, from Abdala (1996). Scale bars: A-C, 10 mm; D-I, 1 mm.
FIG. 1. — A, location of Triassic sediments in the State of Rio Grande do Sul. Extension of the P... more FIG. 1. — A, location of Triassic sediments in the State of Rio Grande do Sul. Extension of the Paraná Basin is indicated on the map of South America; B, location map of the Santa Cruz do Sul locality in the central region of Rio Grande do Sul state (modified from Bertoni-Machado & Holz 2006).
cf. <i>Probainognathus</i> sp. (Figs 2; 3) DESCRIPTION UFRGS-PV-1121T is represented ... more cf. <i>Probainognathus</i> sp. (Figs 2; 3) DESCRIPTION UFRGS-PV-1121T is represented by a fragment of the right mandibular ramus of approximately 7 mm in length (Fig. 2). The horizontal portion is remarkably low and presents one ellipsoid empty alveolus, two alveoli preserving the base of the crowns and the fourth alveolus with a partial postcanine. The coronoid process is rising immediately behind the last postcanine, whereas the ventral margin of the horizontal ramus is straight (Fig. 5A). In medial view the meckelian canal is placed near the ventral margin of the dentary, at approximately one quarter of the height of the bone (Fig. 2B). Most of the meckelian canal is horizontal, except for the posterior portion, at the level of the preserved postcanine, which is directed postero-dorsally (Fig. 2B). The preserved postcanine is 1.8 mm in anteroposterior length (Table 2) and shows a large main cusp, which is aligned with the anterior and posterior accessory cusps (Fig. 3...
FIG. 5. — Chrono- and biostratigraphy of southern Brazilian Triassic units: A, Geologic Time Scal... more FIG. 5. — Chrono- and biostratigraphy of southern Brazilian Triassic units: A, Geologic Time Scale 2004 (from Gradstein & Ogg 2004); B, time scale after Muttoni et al. (2004 and reference cited therein), except for the Anisian lower age, after Lehrmann et al. (2006). Dashed line is inferred extension of the base of the Dinodontosaurus Assemblage Zone suggested by the record of the traversodontid Luangwa and the Mariante rhynchosaur (see text).
outcrop of the Triassic Santa Maria Formation contains a rather unusual fossil occurrence consist... more outcrop of the Triassic Santa Maria Formation contains a rather unusual fossil occurrence consisting of a concentration of disarticulated therapsid skeletons dominated by herbivorous and carnivorous cynodonts. Non-cynodont remains are restricted to a single specimen of Rhadinosuchidae (Archosauriformes: Proterochampsia). The taphocoenosis is characterized by the chaotic accumulation of tens of isolated fossil bones within a block of mudrock 10 m wide and 20 m long, and approximately 5 m thick. The site lies within an approximately 30 m thick succession of red mudstone displaying horizons of rhizoliths and carbonate nodules which are interpreted as palaeopedogenic carbonate precipitation in alluvium on a semi arid floodplain. Preservation of the fossil bones at this site is unusually good. Microstructure of the bones shows external and internal precipitation of calcite and quartz in the vessel cavities and pores in the bone matrix indicating that they were initially filled by calcite...
Palavras-chave: Mastodonte, Stegomastodon waringi, tafonomia, Dermestidae, vertebras, Pleistoceno... more Palavras-chave: Mastodonte, Stegomastodon waringi, tafonomia, Dermestidae, vertebras, Pleistoceno. ABSTRACT - INSECT ACTION IN VERTEBRAE OF STEGOMASTODON WARINGI (MAMMALIA, GOMPHOTHERIIDAE) FROM THE PLEISTOCENE OF AGUAS DE ARAXA, MINAS GERAIS, BRAZIL. Borings in several cervical vertebrae of Pleistocene mastodons, found in deposits from Aguas de Araxa city (Minas Gerais State), are recognized here. These borings are assigned to coleopterans pupae chambers. They are represented by hollow oval-shaped structures (without filling), excavated in the spongy part of the bone. The presence of these excavations suggests that the bone fragments of mastodons from Araxa had a relatively long time of exposure, which was sufficient to allow beetles posture, but not long enough to allow the weathering destroy them.
Pesquisas em Geociências
We present here an outcrop with a peculiar fossil assemblage, including a distinct taphocoenosis ... more We present here an outcrop with a peculiar fossil assemblage, including a distinct taphocoenosis in comparison to other fossiliferous outcrops of the Santa Maria Formation (Triassic, Paraná Basin). Fossil concentration in this outcrop is made-up of herbivorous non-mammalian cynodonts (Synapsida, Therapsida) only, tentatively assigned to Massetognathus. The taphocoenosis is characterized by the accumulation of bones within a restricted area, with predominance of skull and mandible remains, almost always disarticulated. Bones are mainly disarticulated and chaotically oriented in a massive, red-colored, muddy matrix. Both the nature of rock matrix and the absence of azimuthal orientation of the bones in the taphocoenosis indicated that tractive currents were not the main process responsible by the accumulation of those fossil remains, mainly skull and lower jaws bones. These are considered the less nutritious bone parts of the vertebrate skeleton and according to this, the skulls and l...
Conforme destacado no capítulo de Introdução à Tafonomia desse livro, o processo de fossilização ... more Conforme destacado no capítulo de Introdução à Tafonomia desse livro, o processo de fossilização é inerentemente seletivo, ou seja, apresenta uma série de vieses de preservação (tendenciosidades), decorrentes de fatores intrínsecos (e.g., dureza do esqueleto) e extrínsecos (e.g., tipos de agentes de transporte e deposição) aos organismos. Além disso, tendenciosidades podem ser introduzidas ainda nas fases iniciais da pesquisa paleontológica (vide Simões & Ghilardi, 2000). Essas são decorrentes das decisões metodológicas, tais como as diferentes estratégias de coleta (=fase de campo da pesquisa) e do processamento e análise das amostras (=fase de laboratório). Por exemplo, partículas bioclásticas extraídas de sedimentos não litificados, comuns em sucessões de rochas do Mesozoico tardio e Cenozoico, podem ser obtidas a partir de amostras totais (bulk samples), as quais permitem obter sucessivas subamostras. Por outro lado, concentrações densas de conchas e ossos, a moda de coquinas (s...
Tafonomia é a ciência que estuda o processo de preservação dos restos orgânicos no registro sedim... more Tafonomia é a ciência que estuda o processo de preservação dos restos orgânicos no registro sedimentar e como esses processos afetam a qualidade do registro fóssil (Behrensmeyer et alii, 2000). O termo Tafonomia (do grego: tafos = sepultamento; nomos = leis) foi introduzido na literatura por Efremov (1940), originalmente para designar o estudo das "leis" que governam a transição dos restos orgânicos da biosfera para litosfera. De um modo geral, pode-se dizer que a Tafonomia nasceu da necessidade do paleontólogo em entender como os organismos e seus restos chegaram à rocha e quais foram os fatores e processos que atuaram na formação das concentrações fossilíferas. Rapidamente, notou-se, porém, que a passagem dos restos orgânicos da biosfera para a litosfera não podia ser descrita por "leis", nem visualizada como ocorrendo dentro de certos padrões constantes e repetitivos. A partir daí, a Tafonomia ganhou terreno no âmbito da Geologia e Paleobiologia, especialmente...
Revista Brasileira de Paleontologia, 2006
Nearby the city of Santa Cruz do Sul (central region of Rio Grande do Sul State in Brazil), an ou... more Nearby the city of Santa Cruz do Sul (central region of Rio Grande do Sul State in Brazil), an outcrop of the Triassic Santa Maria Formation contains a rather unusual fossil occurrence consisting of a concentration of disarticulated therapsid skeletons dominated by herbivorous and carnivorous cynodonts. Noncynodont remains are restricted to a single specimen of Rhadinosuchidae (Archosauriformes: Proterochampsia). The taphocoenosis is characterized by the chaotic accumulation of tens of isolated fossil bones within a block of mudrock 10 m wide and 20 m long, and approximately 5 m thick. The site lies within an approximately 30 m thick succession of red mudstone displaying horizons of rhizoliths and carbonate nodules which are interpreted as palaeopedogenic carbonate precipitation in alluvium on a semi arid floodplain. Preservation of the fossil bones at this site is unusually good. Microstructure of the bones shows external and internal precipitation of calcite and quartz in the vessel cavities and pores in the bone matrix indicating that they were initially filled by calcite, and than partially replaced by quartz. These features combined with the presence of calcareous rhizoliths and carbonate nodules, suggest that the bones were accumulated on a playa lake margin with the position of the shoreline being controlled by the groundwater table movements between dry and wet seasons. The taphocoenosis shows a predominance of disarticulated and disassociated skulls and mandibles. Commonly large and very small bones occur side-by-side with no preferred orientation. This taphonomic style suggests a biogenic agent of concentration of the bones by selective predation.
PLOS ONE, 2015
The 'Rauisuchia' are a group of Triassic pseudosuchian archosaurs that displayed a near worldwide... more The 'Rauisuchia' are a group of Triassic pseudosuchian archosaurs that displayed a near worldwide distribution. In Brazil, their fossils are found only in the Santa Maria Formation (Paraná Basin) of the Rio Grande do Sul State, specifically in the Middle Triassic Dinodontosaurus assemblage zone (AZ) and the Late Triassic Hyperodapedon AZ (Rauisuchus tiradentes). Between these two cenozones is the Santacruzodon AZ (Middle Triassic), whose record was, until now, restricted to non-mammalian cynodonts and the proterochampsian Chanaresuchus bonapartei. Here we present the first occurrence of a rauisuchian archosaur for this cenozone, from the Schoenstatt outcrop, located near the city of Santa Cruz do Sul and propose a new species, based on biostratigraphical evidence and a comparative osteological analysis.
Quaternary International, 2013
During the Quaternary in South America, the gomphotheres were one of the most common elements in ... more During the Quaternary in South America, the gomphotheres were one of the most common elements in the mammal megafauna. They went extinct in an evolutionary event known as the Late-Pleistocene Megafaunal Extinction, of which climate changes and human hunting are commonly claimed as the main possible causes. Most of the Brazilian Pleistocene fossil mammals did not preserve collagen, so alternative dating techniques are needed. In this case, the only option for dating such fossils is via Electron Spin Resonance (ESR) dating. The aim of this paper is (i) to place the Quaternary Águas de Araxá's Notiomastodon platensis population in a chronological context through ESR dating and, (ii) to investigate its paleoenvironmental context and extinction causes. The ESR analysis was made on both crushed tooth enamel and sediment from the study area. They were subjected to Neutron Activation Analysis to determine the concentration of U, Th and K. The ESR dating indicated an age somewhere between 60,000 and 55,000 a for this N. platensis population (Lujanian, the last age of the Late Pleistocene South American Land Mammal Ages e SALMA). The date found for these gomphotheres is included in the Middle Pleniglacial, which is characterized by a cold and arid climate. Previous paleodiet studies suggest that the feeding habits of those individuals were basically opportunistic/generalist herbivores (C 3 grasses and woody plants). Taphonomically, it was observed that the gomphotheres carcasses were transported by a high-energy water stream, typical of fluvial systems, and that the large amount of individuals in the fossil record is due to a mass death event related to a dry period. Based on taphonomical, paleoecological and chronological evidence, it is possible to assume that the gomphothere population from the Quaternary of Águas de Araxá is probably an example of individuals that suffered from climate changes during the Late Pleistocene in South America.
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Papers by Cristina Bertoni Machado