Academic literature on the topic 'Xenarthara, Fossil'
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Journal articles on the topic "Xenarthara, Fossil"
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Gaudin, Timothy J., and William D. Turnbull. "The stapedial morphology of the Xenarthra and its implications for higher-level mammalian relationships." Paleontological Society Special Publications 6 (1992): 107. http://dx.doi.org/10.1017/s2475262200006675.
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The mammalian order Xenarthra (including the living Neotropical armadillos, anteaters, and tree sloths) has figured importantly in recent hypotheses of interordinal relationships among eutherian mammals. It has been suggested that the group shares a common ancestry both with the extant Old World order Pholidota (i.e. the pangolins or scaly-anteaters) and the extinct North American group Palaeanodonta. Furthermore, these three groups have been linked together into a monophyletic Cohort Edentata, which has been hypothesized to represent the sister-group to all other eutherians. This placement of edentates relative to the remainder of Eutheria has been supported in part by a purported difference in the morphology of the stapes in the two groups- edentates possessing a primitive, imperforate/columelliform morphology, other placentals a derived, perforate/stirrup-shaped morphology.A recent study of stapedial morphology among mammals by Novacek and Wyss (1986) suggests that within the Xenarthra itself a perforate stapes is found among armadillos, but that the pilosa in particular (the clade including anteaters and sloths) and the order as a whole are characterized primitively by an imperforate stapes. Our studies of the xenarthran ear region (Patterson et al., in press) have uncovered new ontogenetic and paleontological evidence which contradict the findings of Novacek and Wyss. Among adults of the two extant tree sloth genera, the stapes lacks a stapedial foramen. However, in both genera, this adult imperforate morphology is derived from a perforated juvenile stapes. Novacek and Wyss ignored fossil species in their consideration of the xenarthran stapes. It has long been known that extinct ground sloths of the family Mylodontidae possessed a large stapedial foramen. Unfortunately, until now no stapes were known from the remaining ground sloth families, the Megatheriidae and the Megalonychidae. We have uncovered a complete left stapes of an early Miocene megatheriid ground sloth Eucholoeops ingens. This stapes possesses a well-developed stapedial foramen. We believe that this new paleontological evidence, combined with our information on the ontogeny of the stapes in the living genera, clearly indicates that a perforate stapes is primitive for sloths. Moreover, when we plot distributions of stapedial morphologies of both living and fossil edentates onto a phylogeny of the Edentata, we can demonstrate that the a large stapedial foramen is primitive for the Xenarthra as a whole, and probably for the entire Cohort Edentata. Such a distribution makes it unlikely that stapedial morphology can be used to separate edentates from other eutherian mammals.
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Hubbe, Alex, Diogo Melo, and Gabriel Marroig. "A case study of extant and extinct Xenarthra cranium covariance structure: implications and applications to paleontology." Paleobiology 42, no. 3 (2016): 465–88. http://dx.doi.org/10.1017/pab.2015.49.
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AbstractMost of the mammalian diversity is known only from fossils, and only a few of these fossils are well preserved or abundant. This undersampling poses serious problems for understanding mammalian phenotypic evolution under a quantitative genetics framework, since this framework requires estimation of a group’s additive genetic variance–covariance matrix (G matrix), which is impossible, and estimating a phenotypic variance–covariance matrix (P matrix) requires larger sample sizes than what is often available for extinct species. One alternative is to use G or P matrices from extant taxa as surrogates for the extinct ones. Although there are reasons to believe this approach is usually safe, it has not been fully explored. By thoroughly determining the extant and some extinct Xenarthra (Mammalia) cranium P matrices, this study aims to explore the feasibility of using extant G or P matrices as surrogates for the extinct ones and to provide guidelines regarding the reliability of this strategy and the necessary sample sizes. Variance–covariance and correlation P matrices for 35 cranium traits from 16 xenarthran genera (12 extant and 4 extinct) were estimated and compared between genera. Results show xenarthran P-matrix structures are usually very similar if sample sizes are reasonable. This study and others developed with extant therian mammals suggest, in general, that using extant G or P matrices as an approximation to extinct ones is a valid approach. Nevertheless, the accuracy of this approach depends on sample size, selected traits, and the type of matrix being considered.
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Davis, Sarah N., Christopher R. Torres, Grace M. Musser, et al. "New mammalian and avian records from the late Eocene La Meseta and Submeseta formations of Seymour Island, Antarctica." PeerJ 8 (January 9, 2020): e8268. http://dx.doi.org/10.7717/peerj.8268.
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The middle–late Eocene of Antarctica was characterized by dramatic change as the continent became isolated from the other southern landmasses and the Antarctic Circumpolar Current formed. These events were crucial to the formation of the permanent Antarctic ice cap, affecting both regional and global climate change. Our best insight into how life in the high latitudes responded to this climatic shift is provided by the fossil record from Seymour Island, near the eastern coast of the Antarctic Peninsula. While extensive collections have been made from the La Meseta and Submeseta formations of this island, few avian taxa other than penguins have been described and mammalian postcranial remains have been scarce. Here, we report new fossils from Seymour Island collected by the Antarctic Peninsula Paleontology Project. These include a mammalian metapodial referred to Xenarthra and avian material including a partial tarsometatarsus referred to Gruiformes (cranes, rails, and allies). Penguin fossils (Sphenisciformes) continue to be most abundant in new collections from these deposits. We report several penguin remains including a large spear-like mandible preserving the symphysis, a nearly complete tarsometatarsus with similarities to the large penguin clade Palaeeudyptes but possibly representing a new species, and two small partial tarsometatarsi belonging to the genus Delphinornis. These findings expand our view of Eocene vertebrate faunas on Antarctica. Specifically, the new remains referred to Gruiformes and Xenarthra provide support for previously proposed, but contentious, earliest occurrence records of these clades on the continent.
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Vizcaíno, Sergio F., and Gerardo De Iuliis. "Evidence for advanced carnivory in fossil armadillos (Mammalia: Xenarthra: Dasypodidae)." Paleobiology 29, no. 1 (2003): 123–38. http://dx.doi.org/10.1666/0094-8373(2003)029<0123:efacif>2.0.co;2.
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The euphractine Macroeuphractus outesi, from the late Pliocene Chapadmalalan SALMA of Buenos Aires Province, Argentina, is one of the largest dasypodids known. Its skull preserves features remarkable for an armadillo. Its complete dental arcade and large caniniform teeth have received attention in the literature as indicative of scavenging behavior. This report considers the degree of carnivory within the context of the generally omnivorous feeding behavior of euphractine armadillos through morphological and biomechanical analyses. Morphological analyses reveal that the main differences between M. outesi and other euphractines are the enlargement of the cranium, particularly of the temporal fossa; more prominent muscular scars for origin of the temporalis muscle; a more expanded rostrum, particularly in dorsoventral height; a more powerful anterior dentition, especially in the great enlargement and caniniform modification of M2; and a deeper and more robust zygomatic arch. Biomechanical analyses indicate that the moment arm of the temporalis musculature is greater than that recorded for other armadillos. These analyses indicate that the temporalis was probably larger and played a more important role in Macroeuphractus than in other euphractines, a pattern that is more usual for carnivorous mammals. Combined with the second upper molariform, which is caniniform, the features suggest that Macroeuphractus occupied an extreme position in the carnivorous-omnivorous feeding behavior of euphractines. Its large size indicates that it could have easily preyed on hare-sized vertebrates.
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Pujos, François, and Rodolfo Salas. "A systematic reassessment and paleogeographic review of fossil Xenarthra from Peru." Bulletin de l’Institut français d’études andines, no. 33 (2) (August 1, 2004): 331–77. http://dx.doi.org/10.4000/bifea.5746.
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Quiñones, Sofía I., Ángel R. Miño-Boilini, Alfredo E. Zurita, et al. "New records of Neogene Xenarthra (Mammalia) from eastern Puna (Argentina): diversity and biochronology." Journal of Paleontology 93, no. 06 (2019): 1258–75. http://dx.doi.org/10.1017/jpa.2019.64.
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AbstractXenarthra is an endemic South American lineage of mammals, probably the sister clade of the other placental mammals. The oldest records of Xenarthra are from the latest Paleocene, although its current diversity is much lower than that recorded in some intervals of the Cenozoic Era. A new Neogene Xenarthra (Pilosa and Cingulata) assemblage from two localities of the Argentine Eastern Puna (Calahoyo and Casira) is described. The newly recorded taxa—Cingulata, Dasypodidae, Eutatini: Stenotatus sp. indet. and Eutatini indet., Euphractini: Macrochorobates scalabrinii (Moreno and Mercerat, 1891), and Tardigrada, Mylodontinae: cf. Simomylodon sp. indet. and Simomylodon cf. S. uccasamamensis Saint-André et al., 2010—and those already published from Calahoyo—Cingulata: Macrochorobates chapadmalensis (Ameghino, 1908), Eosclerocalyptus sp. indet., and Tardigrada, Megatheriidae: Pyramiodontherium bergi (Moreno and Mercerat, 1891)—suggest a middle–late Miocene age for the fossil-bearing levels. In Calahoyo, the presence of Stenotatus sp. indet., in addition to some rodents currently under study in the lower levels, suggest a closer similarity with the palaeofauna of Cerdas (southern Bolivia), probably involving the last part of the Miocene Climatic Optimum. The Xenarthra recorded in the middle and upper levels of Calahoyo and Casira suggest a late Miocene–Pliocene age. A comparative analysis between Calahoyo and Casira highlights the absence of Cingulata in the latter and a high diversity in the former. This situation probably indicates different paleoenvironmental conditions. Finally, we present the first certain record of the genus Simomylodon Saint-André et al., 2010 in Argentina, which includes the oldest record of dermal ossicles for sloths in South America.
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dos Reis, Mario, Jun Inoue, Masami Hasegawa, Robert J. Asher, Philip C. J. Donoghue, and Ziheng Yang. "Phylogenomic datasets provide both precision and accuracy in estimating the timescale of placental mammal phylogeny." Proceedings of the Royal Society B: Biological Sciences 279, no. 1742 (2012): 3491–500. http://dx.doi.org/10.1098/rspb.2012.0683.
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The fossil record suggests a rapid radiation of placental mammals following the Cretaceous–Paleogene (K–Pg) mass extinction 65 million years ago (Ma); nevertheless, molecular time estimates, while highly variable, are generally much older. Early molecular studies suffer from inadequate dating methods, reliance on the molecular clock, and simplistic and over-confident interpretations of the fossil record. More recent studies have used Bayesian dating methods that circumvent those issues, but the use of limited data has led to large estimation uncertainties, precluding a decisive conclusion on the timing of mammalian diversifications. Here we use a powerful Bayesian method to analyse 36 nuclear genomes and 274 mitochondrial genomes (20.6 million base pairs), combined with robust but flexible fossil calibrations. Our posterior time estimates suggest that marsupials diverged from eutherians 168–178 Ma, and crown Marsupialia diverged 64–84 Ma. Placentalia diverged 88–90 Ma, and present-day placental orders (except Primates and Xenarthra) originated in a ∼20 Myr window (45–65 Ma) after the K–Pg extinction. Therefore we reject a pre K–Pg model of placental ordinal diversification. We suggest other infamous instances of mismatch between molecular and palaeontological divergence time estimates will be resolved with this same approach.
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Springer, Mark S., Robert W. Meredith, Jan E. Janecka, and William J. Murphy. "The historical biogeography of Mammalia." Philosophical Transactions of the Royal Society B: Biological Sciences 366, no. 1577 (2011): 2478–502. http://dx.doi.org/10.1098/rstb.2011.0023.
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Palaeobiogeographic reconstructions are underpinned by phylogenies, divergence times and ancestral area reconstructions, which together yield ancestral area chronograms that provide a basis for proposing and testing hypotheses of dispersal and vicariance. Methods for area coding include multi-state coding with a single character, binary coding with multiple characters and string coding. Ancestral reconstruction methods are divided into parsimony versus Bayesian/likelihood approaches. We compared nine methods for reconstructing ancestral areas for placental mammals. Ambiguous reconstructions were a problem for all methods. Important differences resulted from coding areas based on the geographical ranges of extant species versus the geographical provenance of the oldest fossil for each lineage. Africa and South America were reconstructed as the ancestral areas for Afrotheria and Xenarthra, respectively. Most methods reconstructed Eurasia as the ancestral area for Boreoeutheria, Euarchontoglires and Laurasiatheria. The coincidence of molecular dates for the separation of Afrotheria and Xenarthra at approximately 100 Ma with the plate tectonic sundering of Africa and South America hints at the importance of vicariance in the early history of Placentalia. Dispersal has also been important including the origins of Madagascar's endemic mammal fauna. Further studies will benefit from increased taxon sampling and the application of new ancestral area reconstruction methods.
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Billet, Guillaume, Lionel Hautier, Christian de Muizon, and Xavier Valentin. "Oldest cingulate skulls provide congruence between morphological and molecular scenarios of armadillo evolution." Proceedings of the Royal Society B: Biological Sciences 278, no. 1719 (2011): 2791–97. http://dx.doi.org/10.1098/rspb.2010.2443.
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The cingulates of the mammalian order Xenarthra present a typical case of disagreement between molecular and morphological phylogenetic studies. We report here the discovery of two new skulls from the Late Oligocene Salla Beds of Bolivia (approx. 26 Ma), which are the oldest known well-preserved cranial remains of the group. A new taxon is described: Kuntinaru boliviensis gen. et sp. nov. A phylogenetic analysis clusters K. boliviensis together with the armadillo subfamily Tolypeutinae. These skulls document an early spotty occurrence for the Tolypeutinae at 26 Ma, in agreement with the temporal predictions of previous molecular studies. The fossil record of tolypeutines is now characterized by a unique occurrence in the Late Oligocene, and a subsequent 12 Myr lack in the fossil record. It is noteworthy that the tolypeutines remain decidedly marginal in the Late Palaeogene and Early Neogene deposits, whereas other cingulate groups diversify. Also, the anatomical phylogenetic analysis herein, which includes K. boliviensis , is congruent with recent molecular phylogenetic analyses. Kuntinaru boliviensis is the oldest confident calibration point available for the whole Cingulata.
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Toledo, N., M. S. Bargo, S. F. Vizcaíno, G. De Iuliis, and F. Pujos. "Evolution of body size in anteaters and sloths (Xenarthra, Pilosa): phylogeny, metabolism, diet and substrate preferences." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 106, no. 4 (2015): 289–301. http://dx.doi.org/10.1017/s1755691016000177.
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ABSTRACTPilosa include anteaters (Vermilingua) and sloths (Folivora). Modern tree sloths are represented by two genera, Bradypus and Choloepus (both around 4–6 kg), whereas the fossil record is very diverse, with approximately 90 genera ranging in age from the Oligocene to the early Holocene. Fossil sloths include four main clades, Megalonychidae, Megatheriidae, Nothrotheriidae, and Mylodontidae, ranging in size from tens of kilograms to several tons. Modern Vermilingua are represented by three genera, Cyclopes, Tamandua and Myrmecophaga, with a size range from 0.25 kg to about 30 kg, and their fossil record is scarce and fragmentary. The dependence of the body size on phylogenetic pattern of Pilosa is analysed here, according to current cladistic hypotheses. Orthonormal decomposition analysis and Abouheif C-mean were performed. Statistics were significantly different from the null-hypothesis, supporting the hypothesis that body size variation correlates with the phylogenetic pattern. Most of the correlation is concentrated within Vermilingua, and less within Mylodontidae, Megatheriidae, Nothrotheriidae and Megalonychidae. Influence of basal metabolic rate (BMR), dietary habits and substrate preference is discussed. In anteaters, specialised insectivory is proposed as the primary constraint on body size evolution. In the case of sloths, mylodontids, megatheriids and nothrotheriids show increasing body size through time; whereas megalonychids retain a wider diversity of sizes. Interplay between BMR and dietary habits appears to be the main factor in shaping evolution of sloth body size.
Dissertations / Theses on the topic "Xenarthara, Fossil"
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Pujos, François. "Contribution à la connaissance des Tardigrades (Mammalia : Xenarthra) du Pléistocène péruvien : systématique, phylogénie, anatomie fonctionnelle et extinction." Paris, Muséum national d'histoire naturelle, 2002. http://www.theses.fr/2002MNHN0020.
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De nouveaux restes de Tardigrades ont été découverts dans les dépôts pléistocènes péruviens. Les Megatheriidae sont extrêmement diversifiés et deux nouvelles espèces du genre Megatherium font l'objet d'une étude anatomique détaillée. Une analyse phylogénétique des mégathères effectuée sur la base de 35 caractères crâniens et postcrâniens a été réalisée. Un nouveau paresseux singulier est également signalé. Ce mégalonychidé, présente une mosai͏̈que de caractères qu'il est inhabituel de retrouver associés chez un même paresseux et pourrait être mis en relation avec des aptitudes arboricoles. Une analyse phylogénétique préliminaire des Megatherioidea sur la base de 34 caractères crâniens et post-crâniens a été effectuée. Des études stratigraphiques et paléo-environnementales ont été réalisées dans trois sites de mammifères pléistocènes. Les fortes modifications du climat ainsi que l'intervention indirecte de l'homme a peut-être joué un rôle important dans l'extinction de ces mammifèresNew Tardigrada specimens have been discovered in Pleistocene deposits of Peru. Megatheriidae are extremely diversified and two new Megatherium species were described in detail. A megatheriine phylogenetic analysis has been performed on the basis of 35 cranial and postcranial characters. A new peculiar sloth is also reported. This Megalonychidae shows a mosaic of characters that is unusual to find associated a single in sloth species and could be related to arboreal habits. A preliminary phylogenetic analysis of Megatherioidea based on 34 cranial and postcranial characters was performed. Stratigraphical and paleoenvironmental studies were performed in three mammal bearing Pleistocene sites. Strong modifications of the climate and the indirect intervention of man may have played an important role in the extinction of these mammals
Books on the topic "Xenarthara, Fossil"
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The armor of fossil giant armadillos (Pampatheriidae, Xenarthra, Mammalia). Texas Memorial Museum, University of Texas at Austin, 1985.
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The ground sloth Megalonyx (xenarthra, megalonychidae) from the Pleistocene (late Irvingtonian) Camelot local fauna, Dorchester County, South Carolina. American Philosophical Society, 2010.
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Bryan, Patterson. The ear region in Xenarthrans ( = Edentata: Mammalia). Field Museum of Natural History, 1992.
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Bryan, Patterson. The ear region in Xenarthrans ( = Edentata: Mammalia). Field Museum of Natural History, 1989.
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Gene, Montgomery G., ed. The Evolution and ecology of armadillos, sloths, and vermilinguas. Smithsonian Institution Press, 1985.
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Description of the skeleton of an extinct gigantic sloth, Mylodon robustus, Owen: With observations on the osteology, natural affinities, and probable habits of the megatheroid quadrupeds in general. J. Van Voorst, 1985.
Book chapters on the topic "Xenarthara, Fossil"
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Rose, Kenneth D., and Robert J. Emry. "Relationships of Xenarthra, Pholidota, and Fossil “Edentates”: The Morphological Evidence." In Mammal Phylogeny. Springer New York, 1993. http://dx.doi.org/10.1007/978-1-4613-9246-0_7.
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Kemp, T. S. "Living and fossil placentals." In The Origin and Evolution of Mammals. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780198507604.003.0010.
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The vast majority of living and fossil mammals are placentals. Today there are about 4,400 species, which are traditionally organised into 18 Orders, with an extra one if the Pinnipedia are separated from the Carnivora, and a twentieth if the recently extinct Malagasy order Bibymalagasia is recognised as such. There have been many attempts to discover supraordinal groupings from amongst these Orders based on morphological characters, though few proposals have been universally accepted. It is only with the advent of increasingly large sets of molecular sequence data in the last few years that a reasonably robust resolution looks imminent, although these contemporary analyses are remarkably and controversially at odds with the traditional ones. Novacek et al. (1988) summarised the then current situation regarding supraordinal classification of placentals, a time at which morphology was still dominant but molecular data was at the threshold of significance. They accepted a basal group Edentata that combined the Xenarthra of the New World with the Pholidota of the Old, based on a few cranial characters, loss of the anterior teeth, and reduction of the enamel of the remaining ones. This left the rest of the living placentals as a monophyletic group Epitheria, sharing such apparently minor characters as the shape of the stapes bone in the ear. They found very little resolution within the Epitheria, and concluded that there was a polychotomy of no less than nine lineages arranged as a ‘star’ phylogeny. No remnant of the previously recognised taxon Ferungulata, created by Simpson (1945) for the Carnivora plus the ungulate orders Artiodactyla, Perissodactyla, Proboscidea, Hyracoidea, Sirenia, and Tubulidentata remained. On the other hand, three supra ordinal taxa of earlier authors did survive. One was Gregory’s (1910) Archonta, consisting of generally conservative forms and by now composed of the Primates, Dermoptera, Scandentia, and Chiroptera, but excluding the Lipotyphla. The second was Glires, originating with Linnaeus (1758) and widely accepted ever since, for the Rodentia and Lagomorpha; Novacek et al. (1988) tentatively placed the Macroscelidea as the sister-group of the Glires. The third supraordinal taxon recognised was, like Glires, well-established if not universally accepted.