This study focuses on Long Pond, a groundwater-fed sinkhole lake in Georgia, which does not exhibit any evidence of eutrophication drivers despite high concentrations of sedimentary phosphorus (P) (> 3000 mg/kg P) in the recent sediment record. Chemical analyses have shown a strong correlation (r2>0.99) between P and aluminum (Al) throughout the core, suggesting Al plays a significant role in sequestering most of the P, and limiting its availability to phytoplankton, thereby inhibiting eutrophication. The purpose of this study is to decipher P and Al physicochemical associations in the sediments. After the samples were fractionated into amorphous and non-amorphous phases, the correlation was maintained in both phases. Evidence suggests two modes of Al-P associations: a sorption and/or co-precipitation occurring mostly in the amorphous phase and a mode whereby Al and P are being inputted to the lake bound together.

O Nordeste brasileiro possui muitos depósitos com rico registro fossilífero da megafauna pleistocênica, ainda a serem estudados com relação ao habitat e hábitos alimentares destes megamamíferos. Desta forma, este trabalho teve por objetivo descrever o ambiente no qual estes animais habitavam durante o Pleistoceno Tardio; discutir o impacto das mudanças climáticas deste período na vegetação e as alterações ocorridas na base da cadeia trófica de representantes da megafauna; verificar se há evidências da interferência humana em sua extinção e averiguar a existência de corredores bióticos que teriam ligado a Mata Atlântica à Floresta Amazônica em momentos de maior umidade na região da Caatinga. Para tanto, foram realizadas análises micropaleontológicas em sedimentos coletados em tanques, contendo restos de megafauna e/ou em lagoas efêmeras, nos municípios de Afrânio, Buíque e São Bento do Una (Pernambuco) e em São João do Cariri (Paraíba) e em cálculos dentários destes animais. Sedimentos coletados em São Bento do Una, com aproximadamente 34.935 anos cal. AP, revelaram a presença de elementos de floresta úmida e fria, de forma descontínua até aproximadamente 19.000 anos cal. AP, coincidindo com os eventos climáticos H3 e H2. Com o aquecimento do final do Pleistoceno, os elementos indicativos de clima frio desapareceram do registro, permanecendo alguns representantes da Amazônia e Floresta Atlântica. Os demais testemunhos cobrem o final do Pleistoceno, até o Holoceno. De forma geral, a umidade permanece, com a manutenção de uma floresta úmida até 6.000 anos cal. AP, quando se inicia a fase de ressecamento e posterior implantação da Caatinga a partir de 4.900 anos cal. AP, sendo esta fase de seca marcada pela perda do sinal polínico, decorrente de hiato, em Buíque. O retorno da umidade, por volta de 2.000 anos cal. AP, foi caracterizado por chuvas torrenciais. Sinais de intervenção humana foram notados através da identificação de palmeiras a partir de 9.000 anos AP, assim como a presença de elementos introduzidos após a colonização. As análises realizadas nos cálculos dentários revelaram a presença de elementos vegetais característicos de floresta úmida e fria, com predomínio de ciclo fotossintético C3. Em suma, conclui-se que os megamamíferos pleistocênicos do Nordeste habitaram em um ecossistema não análogo à Caatinga atual; a presença de elementos vegetais atualmente restritos a ambientes mais úmidos e frios, indica a instalação de um corredor de trocas bióticas no passado; registros micropaleontológicos da Caatinga estão em sincronia e corroboram os estudos paleoclimáticos do Nordeste, no Quaternário Tardio. Não obstante, as alterações climáticas do Pleistoceno Tardio não foram responsáveis pelo estabelecimento da vegetação hiperxerófila, fato que ocorreu por volta de 4.900 anos cal. AP. Desta forma, a extinção da megafauna não ocorreu devido à inexistência de vegetação, mas o início do declínio pode ter ocorrido devido à configuração climática, em decorrência do aquecimento gradativo aliado ao aumento da pluviosidade, ao término do Último Máximo Glacial e durante o evento climático H1. / Northeastern Brazil has many deposits with rich fossil record of the Pleistocene megafauna, still to be studied in relation to the habitat and feeding habits of these megamammals. In this way, this work had the objective to describe the environment in which these animals inhabited during the Late Pleistocene; discuss the impact of climatic changes of this period on vegetation and the changes occurring at the base of the trophic chain of megafauna representatives; to verify if there is evidence of human interference in its extinction; and to investigate the existence of biotic corridors that would have connected the Atlantic Forest to the Amazon Forest in times of greater humidity in the Caatinga region. For that, micropaleontological analyses were performed in sediments collected in tanks containing megafauna remains and / or in ephemeral lagoons, in the cities of Afrânio, Buíque and São Bento do Una (Pernambuco state) and in São João do Cariri (Paraíba state) also in dental calculus of these animals. Sediments approximately 34,935 yrs cal. BP collected from São Bento do Una, revealed the presence of elements of wet and cold forest, discontinuously approximately 19,000 yrs cal. BP, coinciding with H3 and H2 climatic events. With the warming of the late Pleistocene, the elements indicative of cold weather disappeared from the registry, remaining some representatives of the Amazon and Atlantic Forest. The other core samples covered the late Pleistocene, up to the Holocene. In general, the humidity remains, with the maintenance of a rainforest up to 6,000 yrs cal. BP, when the dry season begins and the posterior Caatinga implantation after 4,900 yrs cal. BP, being this drought phase marked by the loss of the pollen signal, due to hiatus in Buíque. The return of humidity, about 2,000 yrs cal. BP, was characterized by torrential rains. Signs of human intervention were noted through the identification of palms from 9,000 yrs cal. BP, as well as the presence of elements introduced after colonization. The analyses performed in dental calculus revealed the presence of vegetal elements characteristic of wet and cold forest, with predominance of C3 photosynthetic cycle. In sum, it is concluded that the Pleistocene megamammals of the northeast inhabited an ecosystem not analogous to the current Caatinga; the presence of plant elements currently restricted to more wet and cold environments, indicates the installation of a corridor of biotic exchanges in the past; micropaleontological records of the Caatinga are in synchrony and corroborate the paleoclimatic studies of the Northeast in the Late Quaternary. Nevertheless, climatic changes of Late Pleistocene were not responsible for the establishment of hyperxerophilic vegetation, a fact that occurred around 4,900 yrs cal. BP. Thus, the extinction of the megafauna did not occur due to the lack of vegetation, but the beginning of the decline may have occurred as a result of the climatic configuration, due to the gradual warming associated with the increase of rainfall, at the end of the Last Glacial Maximum and during the climatic event H1.

The first high resolution record of dinoflagellate cysts ~110-155 kyr over Termination II and the last interglacial in the Santa Barbara Basin, California from ODP Hole 893A details a complex paleoceanographic history. Changes in cyst abundances, concentrations, diversity, and assemblages reflect climatic and ocean circulation changes, and are successfully used to make quantitative reconstructions of past sea surface temperatures and annual primary productivity with the modern analogue technique based on a dinoflagellate cyst database from the northeast Pacific. The dominance of heterotrophic dinoflagellate cyst taxa Brigantedinium spp. throughout most of the section indicates coastal upwelling is an important influence on the basin. Based on the dinoflagellate cyst assemblages, five cyst zones are identified and approximately correspond to the marine isotope stage boundaries and their associated changes in sea surface temperatures and sea level. Cooler intervals, MIS 6 and MIS 5d, are characterized by cold-water indicator species Selenopemphix undulata whereas thermophyllic taxon Spiniferites mirabilis characterizes MIS 5e. In contrast to other studies in the Pacific, the data shows a one to two-thousand-year cooling event ~129 kyr that correlates to the Termination II sea level still-stand of the two-step deglaciation. A significant increase in cyst concentrations of heterotrophic and autotrophic taxa in the latest MIS 5e implies enhanced primary productivity as a result of increased seasonal upwelling and the warm, nutrient rich waters entering the basin after sea level stabilizes near modern levels. The hydrological evolution and cyst signal of the last interglacial is similar to the development of the Holocene in the Santa Barbara Basin, but the sustained presence of Spiniferites mirabilis across MIS 5e indicates sea surface temperatures were higher than modern conditions. The quantitative reconstructions appear to be less reliable, and show wide sea surface temperature changes across MIS 6 to 5d (~6.2-10.7°C in February; ~12.6-20.3°C in August) similar to modern ranges, while annual primary productivity was confined to a higher narrower range (~456-586 g C m-2 yr-1). / Graduate / 2020-04-18

Rockshelters are capable of preserving excellent environmental records within their sediments. But the matter of interpreting an environmental record from rockshelter sediments presents a significant hurdle in the form of dating. An “age-depth model” is typically used to estimate the age of environmental information extending through the deposit. An age-depth model calculates the changes in time between direct ages (like a radiocarbon age) and can provide an estimated age for any depth. While radiocarbon dating can provide an age for organic remains, optically stimulated luminescence (OSL) can provide a direct age on quartz sand deposition and is particularly effective when applied to deposits formed by the wind. This study compares radiocarbon and OSL age-depth models from Last Canyon Cave (LCC) in the Pryor Mountains of south-central Montana. While radiocarbon ages are quite frequently used to construct age-depth models, it is possible they fail to provide accurate ages for the environmental material they aim to date. I re-evaluated the stratigraphy at LCC and then collected OSL samples as well as samples for grain-size analysis from three different sedimentary exposures. Radiocarbon ages had already been produced for one of the exposures (Kornfeld et al. 2012). The OSL samples were most reliable when analyzed on a single-grain level. After creating age-depth models and collecting the grain-size data, I applied ages to all of the grain-size samples according to each of the three age-depth models. Ultimately, the single-grain OSL proved to be fundamentally different than the radiocarbon age-depth model, thereby challenging the current paleoenvironmental reconstruction of the site (Minckley et al. 2015). I conclude that the radiocarbon and single-grain OSL age-depth models were not sufficiently similar, and therefore both dating methods should always be used together when investigating deposits in rockshelters in order to understand how they relate to one another and to the site formation. The use of granulometry also proved to be an important part of reconstruction site formation history. Ultimately, both single-grain OSL and granulometry were determined to be essential parts of studying environmental records in sedimentary deposits in rockshelters.

This review considers important themes concerning the peopling of South America that have been analyzed in the various articles in this volume. The identification of the oldest lithic tools, the criteria of human association with extinct faunas and the selection of analytical units used to describe the process of peopling are the main themes. Paleoenvironmental issues and its relevance to understand the process of human colonization are also considered. / Se presenta una discusión acerca de algunos temas centrales relacionados con el poblamiento de América del Sur que han sido objeto de análisis en los distintos artículos de este volumen. Se enfatizan cuestiones de identifi cación de las herramientas líticas más antiguas, criterios de asociación humana con fauna extinta y elección de unidades analíticas utilizadas para describir los procesos de poblamiento. También se considera la relevancia de los aspectos paleoambientales para comprender el proceso de colonización humana.

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No. of bitstreams: 1 Dissertacao_KatyMarilym.pdf: 15479101 bytes, checksum: aedfdc050a05128d76fa06e8cfa26c4c (MD5) Previous issue date: 2018-03-28 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work was carried out aiming at the interpretation and inference of the paleoenvironments of a carbonate succession belonging to the Itaituba Formation (Pensilvaniano of the Amazon Basin), which appears on the banks of the Tapajós River, SW of the state of Pará, petrographic studies focused at the characterization and identification of sedimentary microfacies were performed from the analysis of 50 thin sections. The petrographic analysis was developed according to the standard methodology for studies of this nature, essentially involving the classification of carbonate rocks and the characterization and individualization of microfacies. As a result of these analyzes, five lithotypes (mudstones, wackestones, packstones, grainstones and boundstones) and nine microfacies were identified: Mudstone with evaporites (Me), Wackstone with terrígenos (Wt), Wackstone with autigenic quartz and phytoclasts (Wqf), Wackstone (Wbc), Packstone with brachiopods (Pb), Grainstone with brachiopods (Gb), Grainstone with fusulinids (Gf), Grainstone with binders (Ga) and Boundstone with intraclasts (Bi). From these microfacies, four biofacies were distinguished (Biofacies 01, Biofacies 02, Biofacies 03 and Biofacies 04), based on the trends and paleocology of the bioclasts, and five associations of non-skeletal grains (Association 01, Association 02, Association 03, Association 04 and Association 05), based on the sedimentological significance of these grains. From this, five types of microfacies, representative of five distinct depositional systems were interpreted: MFT-01) semi-restricted coastal sabhka, MFT-02) tidal plain, MFT-03) lagoon, MFT-04) tidal channels and MFT -05) bioclastic bars. These types of microfacies indicate a depositional carbonaceous platform model in ramp, with the development of a shallow marine depositional system, dominated by carbonate sedimentation, influenced by tide, under the dominant regime of semiarid climatic and temperature of the water mass varying from temperate to hot. / Este trabalho foi realizado visando à interpretação e a inferência dos paleoambientes de uma sucessão carbonática pertencente à Formação Itaituba (Pensilvaniano da Bacia do Amazonas), que aflora às margens do Rio Tapajós, SW do estado do Pará, estudos petrográficos voltados à caracterização e identificação de microfáceis sedimentares foram realizados a partir da análise de 50 seções delgadas. A análise petrográfica foi desenvolvida de acordo com a metodologia padrão para estudos desta natureza, envolvendo, essencialmente, a classificação das rochas carbonáticas e a caracterização e a individualização de microfácies. Como resultado destas análises foram identificados cinco litótipos (mudstones, wackestones, packstones, graisntones e boundstones) e nove microfácies: Mudstone com evaporitos (Me), Wackstone com terrígenos (Wt), Wackstone com quartzo autigênico e fitoclastos (Wqf), Wackstone com braquiópodes e crinóides (Wbc), Packstone com braquiópodes (Pb), Grainstone com braquiópodes (Gb), Grainstone com fusulinídeos (Gf), Grainstone com aglutinantes (Ga) e Boundstone com intraclastos (Bi). Destas microfácies, foram distinguidas quatro biofácies (Biofácies 01, Biofácies 02, Biofácies 03 e Biofácies 04), baseadas nos trends e paleocologia dos bioclastos, e cinco associações de grãos não-esqueletais (Associação 01, Associação 02, Associação 03, Associação 04 e Associação 05), fundamentadas no significado sedimentológico destes grãos. A partir disto, foram interpretados cinco tipos de microfácies, representativos de cinco sistemas deposicionais distintos: MFT-01) sabhka costeira semi-restrita, MFT-02) planície de maré, MFT-03) laguna, MFT-04) canais de maré e MFT-05) barras bioclásticas. Estes tipos de microfácies compõem o modelo deposicional de plataforma carbonática em rampa, com o desenvolvimento de um sistema deposicional marinho raso, dominado por sedimentação carbonática, influenciado por maré, sob regime climático dominante de clima semiárido e temperatura da massa d’água variando de temperada a quente.

Dans le premier chapitre, les dinokystes sont utilisés pour caractériser les étages du Crétacé supérieur et le Paléocène dans puits ODP 959D, foré sur la marge de Côte d'Ivoire-Ghana. La comparaison de nos résultats avec deux études antérieures montre des conflits de position des limites d'étages chaque fois que les marqueurs biostratigraphiques sont des formes rares.Le deuxième chapitre analyse la distribution des dinokystes albiens le long d'un transept côte-large sur la marge ouest ibérique. La comparaison des données des dinokystes avec celles de sédimentologie et de paléontologie permet d'identifier des groupes d'espèces qui ont des préférences et tolérances environnementales communs. Les principaux facteurs contrôlant la distribution des dinokystes sont le gradient de stabilité et de prédictibilité et la disponibilité des nutriments. L'évolution paléo-océanographique et paléo-géographique de la marge ouest ibérique au cours de l'Albien est clairement enregistrée par les associations de dinokystes.Le troisième chapitre compare les répartitions des dinokystes aptiens de l'Atlantique central et du nord-ouest de la Téthys. Ce chapitre teste la méthodologie et les préférences paléo-environnementales des dinokystes obtenus pour l'Albien. Les résultats de l'étude de l'Aptien correspondent précisément à ceux de l'Albien. Les associations de dinokystes enregistrent l'évolution des plates-formes carbonatées dans les régions étudiées, la confrontation avec les donnés de la matière organique sédimentaire permet l'identification des changements océaniques mondiaux et régionaux ; la disparition des plates-formes carbonatées, l'OAE 1a et le niveau Fallot. / In the first chapter, dinocysts are used to recognize the Upper Cretaceous and Paleocene stage boundaries in the ODP Hole 959D, on the Côte d’Ivoire–Ghana transform margin. The comparison of my own results with two previous studies of the same cores highlights uncertainties of biostratigraphic approach when dinocyst markers have low occurrence frequencies. The second chapter analyzes the dinocyst distribution along an inshore-offshore transect on the western Iberian Margin during the Albian. Contrasting the dinocyst occurrence data with the sedimentological and paleontological data allow identifying dinocyst associations with common environmental preferences and tolerances. The main factors contributing to the dinocyst distribution are the stability and predictability gradient and the nutrient availability. Paleoceanographic and paleogeographic evolution of the western Iberian margin during the Albian are clearly recorded in the spatiotemporal occurrence patterns of dinocyst associations. The third chapter compares Aptian dinocyst distribution from the Central Atlantic and northwestern Tethys. It is used to test the methodology and the paleoenvironmental preferences of dinocyst issued from the second chapter. The recognized paleoenvironmental preferences and tolerances of the Aptian dinocysts precisely match those proposed for the Albian species. The Aptian dinocyst associations reflect the evolution of carbonate platforms of both the Southern Provence Basin and the western Iberian margin, combined with the sedimentary organic matter allows the identification of regional and global oceanic changes; the demise of carbonate platforms, the OAE 1a and the Fallot level.

Le bassin paléoprotérozoïque (2,1 à 2,0 Ga) de Franceville, situé au Sud-est du Gabon, est étudié depuis des décennies pour son fort potentiel métallifère (uranium et manganèse), depuis 2010, pour avoir livré les plus anciens macro-organismes multicellulaires connus à ce jour, repoussant la limite de l'apparition de la vie multicellulaire complexe à 2,1 Ga. Cette période, est synchrone de grands bouleversements ayant affectés à l'échelle du Globe la chimie de l'atmosphère et des océans et correspond à la mise en place de la formation FB de la série sédimentaire du Francevillien. C'est dans la région de Mvengué, au centre du bassin, que le stratotype de la formation FB a été initialement défini. L'objectif de cette étude est de pouvoir apporter de nouvelles informations sur les conditions de sédimentation et de diagenèse précoce de ces sédiments, et de mieux comprendre la mise en place de la sédimentation carbonatée essentiellement au sein de niveaux de black shales et d'intercalations silto-gréseuses.<br/>Dans la zone de Mvengué, les dépôts de la formation FB sont composés d'unités déposées dans un environnement marin avec des profondeurs variables en dessous de la limite d'action des vagues de tempête. On distingue les unités (1) FB1b comprenant des pélites noires, des grès intercalaires et des pélites rubanées ou dolomites litées, (2) FB1c formée par l'alternance de black shales et de grès noirs et enfin (3) FB2a caractérisée par les grès massifs ou grès de Poubara. La variabilité verticale est identique dans les différents sondages. Les analyses pétrographiques, minéralogiques et chimiques montrent que ces sédiments ont subi une diagenèse modérée. Toutefois, les effets de cette diagenèse est variable selon les faciès.<br/>Les carbonates sont associés aux black shales, de manière souvent diffuse, ils peuvent s'exprimer en lits et bancs individualisés à Mvengué, mais également en concrétions sur le site de Moanda, où elles apparaissent sur une épaisseur de 12 m intercalées dans les niveaux de black shale de l'unité FB1c. Ces concrétions, ovoïdes à lenticulaires, de taille centimétrique à décamétrique, forment des alignements au sein de 8 niveaux successifs. Quelle que soit leurs formes, leurs relations géométriques avec les lamines de l'encaissant black shale argue en faveur d'une mise en place dans un sédiment encore meuble, bien avant le début de la compaction. En se développant les concrétions ont incorporé une fraction argileuse semblable à celle de l'encaissant et dont la composition est relativement homogène depuis leur bordure externe jusqu'à leur centre. Les analyses isotopiques du carbone et de l'oxygène de la phase carbonatée et du carbone de la phase organique ainsi que les relations morphologiques et texturales indiquent que la dolomitisation ayant générée ces concrétions s'est effectuée durant les premiers stades de la diagenèse et a été favorisée par l'oxydation bactérienne de la matière organique conduisant à l'augmentation de l'alcalinité des eaux interstitielles des sédiments. / The Paleoproterozoic (2.1 to 2.0 Ga) Franceville Basin, South-east of Gabon, has been studied for decades for its high metalliferous (primarily uranium and manganese) potential. The discovery of the oldest known macro-multicellular organisms in the FB Formation in the basin in 2010 caused a repositioning of the appearance of complex multicellular life to 2.1 Ga in Earth history. This period is synchronous with great upheavals that affected the global chemistry of the atmosphere and oceans, and corresponds to the deposition of the FB Formation in the Franceville Basin. Core samples from the FB Formation were sampled from the centre of the basin (MVengué syncline) and the western flank of the basin (Moanda) for comparative analyses. The objective of this study is to provide new information on precipitation conditions of the early diagenetic carbonate cements and concretions associated with the organic-rich black shales and siltstones in the FB Formation using facies analyses, petrographic, and geochemical techniques.<br/>At the basin centre, the FB Formation is composed of sedimentary units that reflect deposition in a deep marine environment with variable depths below the limit of storm wave actions. Three units can be distinguished: (1) FB1b consisting of black shales, fine grained sandstones, and laminated mudstones or layered dolomites; (2) FB1c consisting of alternating black shales and sandstones; and (3) FB2a that is characterized by massive sandstone (namely the Poubara sandstone). Detailed analytical studies showed that these sediments have undergone moderate diagenetic modifications. However, the degree of diagenesis varies between different lithofacies.<br/>The carbonates are commonly diffused within the associated black shales throughout the FB Formation. In addition, at the Mvengué, the carbonates are present as individual beds, and as ovoid to lenticular centimeters to tens of centimeters thick concretions at Moanda, where they occur interlayering the FB1c black shales at eight levels. Irrespective of their form of occurrence, their relationships with the laminated black shale argues in favour of their formation before significant compaction. As a result, the incorporated clay minerals in the concretions are similar to the host rocks (black shales) and their composition is relatively homogenous from the edge to the centre. Isotope analyses of carbon and oxygen in the carbonates and of carbon in the organic matter, as well as the morphological and textural relationships suggest that the dolomitiation processes at the origin of the concretions, occurred during the early diagenetic stage, were favoured by bacterial oxidation of organic matter resulting in increasing pore water alkalinity in the sediments.

No description available.

L’étude des faunes du Quaternaire s’inscrit dans une dynamique de connaissance des paléoenvironnements et est de ce fait nécessaire pour mieux cerner les contraintes environnementales qui ont rythmé la dispersion des hominidés sur l’ensemble des continents. Le genre Canis, autour duquel nous avons axé ce travail de recherche, présente la particularité d’être resté constamment présent en Europe occidentale depuis son apparition, il y a plus de trois millions d’années, jusqu’à aujourd’hui. Cette constance fait de lui, malgré son caractère ubiquiste, un excellent témoin de l’évolution des paléoenvironnements.A travers l’analyse de la variabilité des populations actuelles et l’étude de dix séries fossiles du Sud de la France couvrant le Pléistocène, de nouveaux éléments de discussion sont avancés sur l’évolution des représentants du genre. Nos résultats, couplés à l’analyse critique des données bibliographiques nous ont dès lors permis de proposer une nouvelle phylogénie. Cette dernière permet non seulement de mieux cerner les phases d’apparition et de dispersion des différentes espèces du genre Canis, mais également de démontrer son potentiel biochronologique. Ainsi, trois grandes phases dans l’évolution du genre ont pu être mises en évidence. La transition de ces espèces est corrélée à de grands événements de l’histoire des faunes quaternaires (bioevent) et autorise de ce fait l’utilisation de cette phylogénie à des fins biochronologiques ainsi qu’une discussion autour des relations entre ces espèces et les paléocommunautés animales et humaines. / Quaternary mammals form an important part of the material available for researchers focusing on paleoenvironmental reconstructions. Their study is thus often used to infer the environmental constraints that set the pace of human dispersal through the world. The genus Canis, main subject of this thesis, is present in Western Europe since its origin three million years ago. This continuous presence makes it a good candidate as a paleoenvironmental proxy, even when considering its ecological plasticity.The study of ten fossil sequences from Southern France spanning the Pleistocene, coupled with the analysis of the variability of modern populations, bring new insights on the evolution of the members of this lineage. Our results, once confronted to previous studies, allowed us to propose a new phylogeny. This new framework permits a better understanding of the apparition and disappearance of the different species, but also demonstrates the biochronological potential of the Canis genus. Three major phases have been identified in its evolutionary history. The transition between the different Canids is correlated with major events in the history of quaternary mammals (bioevent). Thus, its phylogeny can be used for biochronological purposes and has to be considered in the bigger debates that focus on the interactions between animal communities and human groups.