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A monodominant late-Pleistocene megafauna locality from Santa Elena, Ecuador: Insight on the biology and behavior of giant ground sloths

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... Xenarthra is a peculiar clade of placental mammals characteristic for the Neotropical region (Gaudin and Croft 2015;Gibb et al. 2015;Delsuc et al. 2016), with a long fossil history since the early Eocene (Bergqvist et al. 2004;Lindsey et al. 2020). Their records are remarkably abundant in various Cenozoic sites mainly in South America (particularly in Argentina, see Scillato-Yané 1986), but also in Central America and North America (McDonald 2005;Brandoni et al. 2016;Gillette et al. 2016). ...
... Their records are remarkably abundant in various Cenozoic sites mainly in South America (particularly in Argentina, see Scillato-Yané 1986), but also in Central America and North America (McDonald 2005;Brandoni et al. 2016;Gillette et al. 2016). Within Xenarthra, two large clades can be recognized, Cingulata and Pilosa, the latter containing the anteaters Vermilingua and the sloths Folivora (or Tardigrada or Phyllophaga, see Delsuc et al. 2001;Lindsey et al. 2020). ...
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Glyptodonts (Mammalia, Xenarthra, Glyptodontidae) represent a diversified radiation of large armored herbivores, mainly related to open biomes in South America, with an extensive fossil history since the late Eocene (ca. 33 Ma) until their extinction in the latest Pleistocene–earliest Holocene. During the Pliocene and Pleistocene, glyptodonts arrived in Central and North America as part of the Great American Biotic Interchange. Within glyptodont diversity, one of the most enigmatic groups (and also one of the least known) are the Doedicurinae, mainly recognized by the enormous Pleistocene Doedicurus, with some specimens reaching ca. two tons. Almost nothing is known about the Neogene evolutionary history of this lineage. Some very complete specimens of the previously scarcely known Eleutherocercus solidus, which in turn becomes the most complete Neogene Doedicurinae, are here described in detail and compared to related taxa. The materials come from the Andalhuala and Corral Quemado formations (north-western Argentina), specifically from stratigraphic levels correlated to the Messinian–Piacenzian interval (latest Miocene–Pliocene). The comparative study and the cladistic analysis support the hypothesis that Doedicurinae forms a well supported monophyletic group, located within a large and diversified clade mostly restricted to southern South America. Within Doedicurinae, the genus Eleutherocercus (E. antiquus + E. solidus) is the sister group of the Pleistocene Doedicurus. Unlike most of the late Neogene and Pleistocene lineages of glyptodonts, doedicurins show along its evolutionary history a latitudinal retraction since the Pleistocene, ending with the giant Doedicurus restricted to the Pampean region of Argentina, southernmost Brazil, and southern Uruguay. This hypothetic relationship between body mass and latitudinal distribution suggests that climate could have played an active role in the evolution of the subfamily.
... Three osteoderms of the giant ground sloth Glossotherium lettsomi flattened by abrasion and perforated like pendants were recovered from the Santa Elina site in levels dating to 27 ka [39]. Although relatively little is known about behaviour or social structure of extinct giant ground sloths, new evidence from a monotypic late Pleistocene locality, Tanque Loma, coastal southwest Ecuador, provides insights into the potential gregarious nature of these megafauna [40]. Researchers interpret the Tanque Loma site as a catastrophic fossil assemblage composed of adult and juvenile Eremotherium laurillardi individuals and suggest that they may have gathered in intergenerational groups. ...
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Megafauna paintings have accompanied the earliest archaeological contexts across the continents, revealing a fundamental inter-relationship between early humans and megafauna during the global human expansion as unfamiliar landscapes were humanized and identities built into new territories. However, the identification of extinct megafauna from rock art is controversial. Here, we examine potential megafauna depictions in the rock art of Serranía de la Lindosa, Colombian Amazon, that includes a giant sloth, a gomphothere, a camelid, horses and three-toed ungulates with trunks. We argue that they are Ice Age rock art based on the (i) naturalistic appearance and diagnostic morphological features of the animal images, (ii) late Pleistocene archaeological dates from La Lindosa confirming the contemporaneity of humans and megafauna, (iii) recovery of ochre pigments in late Pleistocene archaeological strata, (iv) the presence of most megafauna identified in the region during the late Pleistocene as attested by archaeological and palaeontological records, and (v) widespread depiction of extinct megafauna in rock art across the Americas. Our findings contribute to the emerging picture of considerable geographical and stylistic variation of geometric and figurative rock art from early human occupations across South America. Lastly, we discuss the implications of our findings for understanding the early human history of tropical South America. This article is part of the theme issue ‘Tropical forests in the deep human past’.
... In addition, the museum provided photographs of some of the bones and fragments on exhibit inside the museum (Supplementary Materials Figure S1). This work presents a compilation of information from projects and scientific articles related to MPM (e.g., [35,[64][65][66][67][68][69][70][71][72][73]). Finally, this study generated general content on the history, culture, interest and representativeness of the MPM. ...
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The Santa Elena province in Ecuador has outstanding geological potential in petroleum, mining and geosite resources. All the wealth of palaeontological samples and their inherent link to the history of this territory require a recognised museum with educational and scientific material tosupport the potential and promotion of geotourism development. The Megatherium Palaeontological Museum is located in this province and was the first Palaeontological Museum in Ecuador. It exhibits samples corresponding to the Late Pleistocene Megafauna that inhabited the area. This study aims to evaluate the museum (a geoheritage element) as a possible (palaeontological) geosite by analysing its contributions to the geoheritage of the Santa Elena province. Thus, we also aim to enhance the geotourism of the area and promote its collections as a geotouristic attraction. The methodological process was based on: i) information processing and systematisation in the museum and its environment; ii) assessment of the museum’s geological interest through the method of the Geological Survey of Spain, the Brilha method and the Geosites Assessment Model; and iii) a qualitative evaluation using the Delphi and the Strengths, Weaknesses, Opportunities and Threats methodologies to define strategies and proposals for museum development. Based on the results of the applied quantitative assessment, the museum has a “very high” (277/400) degree of geological interest, due to the high values of scientific (310/400), academic (310/400) and touristic (210/400) interest. In this same way, the results obtained through the Brilha method reflect a high scientific (290/400), educational (280/400), and tourist (315/400) interest and a low degradation risk (190/400) value in the museum. Furthermore, the applied Geosites Assessment Model shows the museum as a geosite with high main and additional values, placing it between the Z23 and Z33 fields of the global valuation matrix. The evaluation approached through Delphi analysis and Strengths, Weaknesses, Opportunities and Threats matrix allowed us to propose improvement strategies to take advantage of the museum resources as an alternative that strengthens the geotouristic development of the area.
... Finally, in hippos, there is a slight degree of sexual size dimorphism, but clear dimorphism in the canines resulting in intense fights between males and the formation of groups of females with a single dominant male and groups of single males (Owen-Smith 1988;Eltringham 1999). The comparison with hippos is of particular interest considering previous hypotheses stating gregarious behaviour similar to hippos for the megatheriid Eremotherium based on abundant accumulations of bones interpreted as a massive death assemblage in ponds (Lindsey et al. 2020). ...
Article
Mylodontidae (Mammalia, Xenarthra) is a family of ground sloths widely distributed in the South American fossil record, with members also present in Central and North America. Within the Mylodontidae, Lestodon armatus is the largest species, with an estimated body mass of more than three tonnes. This work focuses on the enlarged lower caniniforms of L. armatus as possibly exaggerated sexually dimorphic structures. Lower caniniforms from the late Pleistocene of Argentina, Uruguay, and Bolivia were studied using specimens from seven palaeontological collections. The possible sexual dimorphism in the caniniforms and its implications regarding the existence of sexual selection was assessed through morphometric analyses. The results support the existence of sexual dimorphism in L. armatus. Sexual dimorphism in an exaggerated structure in a large mammal suggests the existence of sexual selection, via competition between males or female mate choice, resulting in the evolution of the dimorphic structure. In L. armatus, the enlarged caniniforms would correspond to males and could have functioned as armaments in intraspecific fights or ornaments for sexual display. Based on observations in extant mammals, a polygynous mating system is proposed as highly probable in L. armatus, although the existence or composition of social groups cannot be certainly determined.
... McDonald 29 suggested, based on the remarkable differences in size and anatomy, that the extinct ground sloths probably had a more complex social structure than their extant relatives, which are solitary animals. However, specific studies including considerations on the social structure of extinct South American ground sloths are very scarce [65][66][67][68] . ...
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Megamammals constituted an important component in the Pleistocene faunal communities of South America. Paleobiological and paleoecological studies involving different megamammal taxa have increased significantly in the last years, but there are still several poorly-known issues of its life history. In this work, we analyze an assemblage composed of 13 individuals of different ontogenetic stages, and possibly different sex, belonging to the giant ground sloth Lestodon armatus (Xenarthra, Folivora), recovered from Playa del Barco site (Pampean Region, Argentina). A dating of 19,849 years Cal BP allows assigning this assemblage to a period of the MIS (Marine Isotope Stage) 2 related to the end of the Last Glacial Maximum. Based on multiple lines of research (e.g. taphonomy, paleopathology, osteohistology, isotopy), we interpret the origin of the assemblage and diverse paleobiological and paleoecological aspects (e.g. social behavior, ontogenetic changes, sexual dimorphism, diseases, resource and habitat use, trophic relationships) of L. armatus. Evidence suggests that the assemblage was formed by a local single event of catastrophic mortality, which affected different members of a social group. This record represents the first accurate evidence of gregariousness for this ground sloth, providing new data on a poorly-known behavior among extinct Folivora.
... Perhaps future studies of South American asphaltic deposits 23 , with renewed attention to sediment and microfossil excavation protocols, could also yield rodent coprolites and nests of paleoecological relevance. Indeed, a recent study from Tanque Loma in Ecuador hypothesized that plant material associated with a mass death assemblage of ground sloths (Eremotherium) could represent disaggregated fecal material 66 . Similarly, the presence of putative "cigar-shaped" coprolites "the size and shape of rodentia" has been reported from the asphaltic site Las Breas de San Felipe of Cuba 67 . ...
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As fossilized feces, coprolites represent direct evidence of animal behavior captured in the fossil record. They encapsulate past ecological interactions between a consumer and its prey and, when they contain plant material, can also guide paleoenvironmental reconstructions. Here we describe the first coprolites from the lagerstätte Rancho La Brea (RLB) in Los Angeles, California, which also represent the first confirmed coprolites from an asphaltic (“tar pit”) context globally. Combining multiple lines of evidence, including radiocarbon dating, body size reconstructions, stable isotope analysis, scanning electron microscopy, and sediment analyses, we document hundreds of rodent coprolites found in association with plant material, and tentatively assign them to the woodrat genus Neotoma. Neotoma nests (i.e., middens) and their associated coprolites inform paleoclimatic reconstructions for the arid southwestern US but are not typically preserved in coastal areas due to environmental and physiological characteristics. The serendipitous activity of an asphalt seep preserved coprolites and their original cellulosic material for 50,000 years at RLB, yielding a snapshot of coastal California during Marine Isotope Stage 3. This discovery augments the proxies available at an already critical fossil locality and highlights the potential for more comprehensive paleoenvironmental analyses at other asphaltic localities globally.
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The saber-toothed cat Smilodon fatalis is known predominantly from “predator trap” deposits, which has made many aspects of its life history difficult to infer. Here, we describe an association of at least two subadult and one adult S. fatalis from Pleistocene coastal deposits in Ecuador. The assemblage likely derived from a catastrophic mass mortality event, and thereby provides insights into the behavior of the species. The presence of a P3 in the subadult dentaries suggests inheritance, a rare instance of familial relatedness in the fossil record. The siblings were at least two years old and were associated with an adult that was likely their mother, indicating prolonged parental care in S. fatalis. Comparison with the growth of pantherine cats suggests that S. fatalis had a unique growth strategy among big cats that combines a growth rate that is similar to a tiger and the extended growth period of a lion.
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The Progreso Basin province (6083) in northwestern Peru and southwestern Ecuador consists of the Paleogene Santa Elena block and Peru Bank, and the Neogene Tumbes- Progreso subbasin. The Santa Elena block and Peru Bank are part of the Cretaceous-Paleogene Total Petroleum System (TPS)(608302), which contains the Cretaceous-Paleogene Santa Elena Block Assessment Unit (60830201). The Tumbes- Progreso subbasin includes the Neogene TPS (608301) and associated Neogene Pull-Apart Basin Assessment Unit (60830101). The complex tectonic history of the Progreso Basin province influenced depositional and erosional patterns across the region, and also the location, timing, and types of seals, traps, possible source and reservoir rocks, and hydrocarbon generation and migration. Marine shales that are interbedded with and overlie reservoir intervals are the probable hydrocarbon source rocks. Timing of hydrocarbon generation and migration was probably Miocene and younger, following creation of the Tumbes-Progreso subbasin by movement along the Dolores-Guayaquil megashear. More than 220 million barrels of oil (MMBO) and 255 billion cubic feet of gas (BCFG) have been produced from the Progreso Basin province. The means of estimated recoverable oil, gas, and natural gas liquids (NGL) resources from undiscovered fields in the province are 237 MMBO, 695 BCFG, and 32 MMB NGL, respectively. The means of estimated recoverable oil, gas, and NGL resources from undiscovered onshore fields are 45 MMBO, 113 BCFG, and 5 MMBNGL, and from undiscovered offshore fields are 192 BBO, 582 BCFG, and 27 MMBNGL. These are USGS grown undiscovered resources that were determined by using a minimum field size of 1 million barrels of oil equivalent.
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The extinction of Pleistocene megafauna and the role played by humans have been subjects of constant debate in American archeology. Previous evidence from the Pampas region of Argentina suggested that this environment might have provided a refugium for the Holocene survival of several megamammals. However, recent excavations and more advanced accelerator mass spectrometry radiocarbon dating at Campo Laborde site in the Argentinian Pampas challenge the Holocene survival of Pleistocene megamammals and provide original and high-quality information documenting direct human impact on the Pleistocene fauna. The new data offer definitive evidence for hunting and butchering of Megatherium americanum (giant ground sloth) at 12,600 cal years BP and dispute previous interpretations that Pleistocene megamammals survived into the Holocene in the Pampas.
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Stable isotope analysis of the first fossilized Eremotherium laurillardi remains from Belize offers valuable insights into the conditions within which this individual lived and its ability to adapt to the increasing aridity of the Last Glacial Maximum (LGM). Cathodoluminescence (CL) microscopy was used to identify chemical alteration of the tooth during fossilization. Results demonstrate that the inner orthodentin resists diagenesis, yielding potentially unaltered values. Using an intensive "vacuum milling" technique, the inner orthodentin produced an accelerator mass spectrometry (AMS) date of 26,975 ± 120 calibrated years before the present. The stable carbon and oxygen isotope analysis of this layer shows that the tooth recorded two wet seasons separated by one longer dry season and that this sloth was able to adapt its diet to the marked seasonality of the LGM. This study offers new insights into obtaining reliable isotope data from fossilized remains and suggests that this individual adapted to climate shifts, contributing to the conversation surrounding megafauna extinction.
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Asphaltic deposits, or " tar pits, " present a unique opportunity to investigate the paleobiology and paleoecology of Quaternary mammals due to their tendency to accumulate and preserve remains of numerous taxa. This role is especially important in areas with low preservation potential or incomplete sampling, such as the Neotropics. Currently, the most well known asphaltic paleontological locality in tropical South America is the Talara tar seeps in northwest Peru, which has yielded a great diversity of microfossils as well as extinct megafauna. Several other highly productive asphaltic localities have been excavated on the nearby Santa Elena Peninsula (SEP) in southwestern Ecuador. This project combines data from recent excavations on the SEP with analyses of fossils collected from southwest Peru and northwest Ecuador currently housed in the collections of the Museo de Historia Natural “Gustavo Orce´s V.” in Quito, Ecuador, the Royal Ontario Museum in Toronto, Canada, and the Muse´um national d’histoire naturelle in Paris, France. In general, the communities of megaherbivores are comparable between these geographically close sites, but Talara and the La Carolina locality in Ecuador present a much more diverse assemblage of birds, micromammals, and carnivores compared to Coralito and Tanque Loma. Taxonomic, geomorphological, and taphonomic data indicate that these two sites were most likely tar pit–style traps analogous to the famous Rancho La Brea locality in California, USA, while the SEP sites Coralito and Tanque Loma likely represent fossil assemblages in marshy or estuarine settings with secondary infiltration of tar. Additionally, geological and taxonomic differences between the nearby localities Coralito and Tanque Loma suggest differences in local paleoenvironments and indicate gregarious behavior in certain species of extinct giant ground sloths. Las localidades asfa´lticas o “charcos de brea” presentan una oportunidad u´nica para investigar la biologı´a y paleoecologı´a de mamı´feros cuaternarios, por su caracterı´stica de acumular numerosos fo´siles de excelente preservacio´n. Este papel esta especialmente importante en lugares con pobre preservacio´n de fo´siles, y/o muestreo incompleto, tal como las regiones neotropicales. La localidad asfa´ltica mas conocida de Sudame´rica es el sitio La Brea en Talara, Peru´, que ha proporcionado una gran diversidad de fo´siles de micromamı´feros ası´ como megamamı´feros pleistoce´nicos. Al mismo tiempo se encuentran localidades asfa´lticas muy productivas en la cercana Penı´nsula Santa Elena, del suroeste del Ecuador. Este trabajo presente resultados de excavaciones recientes en la Penı´nsula de Santa Elena, junto con ana´lisis de fo´siles provenientes de los sitios asfa´lticos del suroeste de Ecuador y noroeste de Peru´ alojados en las colecciones del Museo Gustavo Orce´s en Ecuador, del Royal OntarioMuseum en Canada´, y del Muse´um national d’histoire naturelle en Francia. Por lo general, las comunidades de megaherbı´voros son comparables entre estos localidades geogra´ficamente cercanos. Sin embargo, Talara y La Carolina presentan una biodiversidad de carnı´voros ymicromamı´feros considerablemente mas alta que la encontrada en los otros dos sitios. Datos taxono´micos, geomorfolo´gicos, y tafonomicos indican que estos sitios probablemente funcionaron como “trampas de brea” parecidos al famoso sitio Rancho La Brea en California, EEUU, mientras las localidades Coralito y Tanque Loma mas probable representan acumulaciones de huesos en contextos fluviales o lacustres con infiltracio´n secundaria de brea. Adema´s, ciertas particularidades de algunas localidades sugieren diferencias en los paleoambientes locales y posiblemente comportamiento social en ciertas especies de perezosos gigantes extinguidas.
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The purpose of this data set was to compile body mass information for all mammals on Earth so that we could investigate the patterns of body mass seen across geographic and taxonomic space and evolutionary time. We were interested in the heritability of body size across taxonomic groups (How conserved is body mass within a genus, family, and order?), in the overall pattern of body mass across continents (Do the moments and other descriptive statistics remain the same across geographic space?), and over evolutionary time (How quickly did body mass patterns iterate on the patterns seen today? Were the Pleistocene extinctions size specific on each continent, and did these events coincide with the arrival of man?). These data are also part of a larger project that seeks to integrate body mass patterns across very diverse taxa (NCEAS Working Group on Body Size in Ecology and Paleoecology: linking pattern and process across space, time, and taxonomic scales). We began with the updated version of D. E. Wilson and D. M. Reeder's taxonomic list of all known Recent mammals of the world (N = 4629 species) to which we added status, distribution, and body mass estimates compiled from the primary and secondary literature. Whenever possible, we used an average of male and female body mass, which was in turn averaged over multiple localities to arrive at our species body mass values. The sources are line referenced in the main data set, with the actual references appearing in a table within the metadata. Mammals have individual records for each continent they occur on. Note that our data set is more than an amalgamation of smaller compilations. Although we relied heavily on a data set for Chiroptera by K. E. Jones (N = 905), the CRC handbook of Mammalian Body Mass (N = 688), and a data set compiled for South America by P. Marquet (N = 505), these represent less than half the records in the current database. The remainder are derived from more than 150 other sources. Furthermore, we include a comprehensive late Pleistocene species assemblage for Africa, North and South America, and Australia (an additional 230 species). “Late Pleistocene” is defined as approximately 11 ka for Africa, North and South America, and as 50 ka for Australia, because these times predate anthropogenic impacts on mammalian fauna. Estimates contained within this data set represent a generalized species value, averaged across sexes and geographic space. Consequently, these data are not appropriate for asking population-level questions where the integration of body mass with specific environmental conditions is important. All extant orders of mammals are included, as well as several archaic groups (N = 4859 species). Because some species are found on more than one continent (particularly Chiroptera), there are 5731 entries. We have body masses for the following: Artiodactyla (280 records), Bibymalagasia (2 records), Carnivora (393 records), Cetacea (75 records), Chiroptera (1071 records), Dasyuromorphia (67 records), Dermoptera (3 records), Didelphimorphia (68 records), Diprotodontia (127 records), Hydracoidea (5 records), Insectivora (234 records), Lagomorpha (53 records), Litopterna (2 records), Macroscelidea (14 records), Microbiotheria (1 record), Monotremata (7 records), Notoryctemorphia (1 record), Notoungulata (5 records), Paucituberculata (5 records), Peramelemorphia (24 records), Perissodactyla (47 records), Pholidota (8 records), Primates (276 records), Proboscidea (14 records), Rodentia (1425 records), Scandentia (15 records), Sirenia (6 records), Tubulidentata (1 record), and Xenarthra (75 records).
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Human-megafauna interaction in the Americas has great scientific and ethical interest because of its implications on Pleistocene extinction. The Arroyo del Vizcaíno site near Sauce, Uruguay has already yielded over 1000 bones belonging to at least 27 individuals, mostly of the giant sloth Lestodon. The assemblage shows some taphonomic features suggestive of human presence, such as a mortality profile dominated by prime adults and little evidence of major fluvial transport. In addition, several bones present deep, asymmetrical, microstriated, sharp and shouldered marks similar to those produced by human stone tools. A few possible lithic elements have also been collected, one of which has the shape of a scraper and micropolish consistent with usage on dry hide. However, the radiocarbon age of the site is unexpectedly old (between 27 and 30 thousand years ago), and thus may be important for understanding the timing of the peopling of America.
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The extinction of late Quaternary megafauna in South America has been extensively debated in past decades. The majority of the hypotheses explaining this phenomenon argue that the extinction was the result of human activities, environmental changes, or even synergism between the two. Although still limited, a good chronological framework is imperative to discuss the plausibility of the available hypotheses. Here we present six new direct AMS 14C radiocarbon dates from the state of São Paulo (Brazil) to further characterize the chronological distribution of extinct fauna in this part of South America. The new dates make evident that ground sloths, toxodonts, and saber-toothed cats lived in the region around the Pleistocene/Holocene transition, and, in agreement with previous studies, also suggest an early Holocene survival for the ground sloth Catonyx cuvieri. Taken together with local paleoclimatic and archaeological data, the new dates do not support hunting or indirect human activities as a major cause for megafauna extinction. Although more data are required, parsimony suggests that climatic changes played a major role in this extinction event.
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Remains of Eremotherium, representing a large-sized megatheriid ground sloth, are known from localities in North, Central, and South America. Usually these remains are currently assigned to the following three species, based largely on geographic provenance: E. laurillardi (Lund), E. mirabile (Leidy), and E. rusconii (Schaub). However, two large, recently recovered collections of Eremotherium remains from Jacobina, Bahia, Brazil, and Daytona Beach, Florida, USA, do not support the separation of these species. Instead, these collections demonstrate the existence of a single Panamerican species. The range of variation is larger than was suspected and the morphological characteristics used in species distinction are not diagnostically valid.The valid name for this species is E. laurillardi (Lund, 1842). The type is a juvenile molariform (ZMUC 1130) from the Pleistocene of Lagoa Santa, Minas Gerais, Brazil. E. mirabile (Leidy, 1855) and E. rusconii (Schaub, 1935) fall as junior synonyms.
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A unique dinosaur assemblage from the Cretaceous beds of western Inner Mongolia preserves geologic and paleontologic data that clearly delineate both the timing and mechanism of death. Over twenty individuals of the ornithomimid Sinornithomimus dongi perished while trapped in the mud of a drying lake or pond, the proximity and alignment of the mired skeletons indicating a catastrophic mass mortality of a social group. Histologic examination reveals the group to consist entirely of immature individuals between one and seven years of age, with no hatchlings or mature individuals. The Sinornithomimus locality supports the interpretation of other, more taphonomically ambiguous assemblages of immature dinosaurs as reflective of juvenile sociality. Adults of various nonavian dinosaurs are known to have engaged in prolonged nesting and post hatching parental care, a life history strategy that implies juveniles spent considerable time away from reproductively active adults. Herding of juveniles, here documented in a Cretaceous ornithomimid, may have been a common life history strategy among nonavian dinosaurs reflecting their oviparity, extensive parental care, and multi-year maturation.
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Hundreds of non-cultural elephant bone sites have been studied in southern Africa, starting at or before the actual moments of death and continuing through bone burial or destruction. In some sites, dozens of elephants died en masse due to drought. These sites contain spirally fractured limb bones in proportions as high as 62% of counted limb elements. Many naturally broken tusk fragments are similar to specimens that have been interpreted as artifacts in fossil proboscidean collections. Trampling marks on bones closely mimic cut marks made by stone tools. As reported here, numerous attributes of non-cultural assemblages are virtually indistinguishable from attributes that archaeologists have believed to be created by human behaviour alone.
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Taphonomic and sedimentologic attributes of three dinosaur bonebeds discovered within the Campanian Two Medicine Formation of Montana suggest drought-related mortality. Two bonebeds, Canyon Bonened and Dino Ridge Quarry, have yielded the near-exclusive remains of a new species of Styracosaurus (Family Ceratopsidae); the third bonebed, Westside Quarry, is dominated by a new species of Prosaurolophus (Family Hadrosauridae). All three assemblages are mono/paucispecific, parautochthonous concentrations of disarticulated and dissociated skeletal debris. Evidence supporting a drought hypothesis includes: 1) a seasonal, semiarid paleoclimate, 2) associated caliche horizons, 3) aqueous depositional settings, 4) apparent age distributions characteristic of modern drought mortality (CBB and DRQ), and the intraformational recurrence of low-diversity bonebeds. Several alternative scenarios were considered, but drought proved most reasonable in light of the enhanced probability of preserving drought assemblages, and the species-selective and recurrent nature of modern drought mortality. Styracosaurus sp. and Prosaurolophus sp. may have been gregarious, water-dependent taxa; during drought these particular taxa may have obligatorily congregated, either in herds, family groups, or seasonal aggregates, in the vicinity of persistent water sources. The mono/paucispecific natures of the bonebeds may reflect ecological segregation due to varying degrees of water-dependency, resource partitioning, or territorial/resource defense within a Late Cretaceous dinosaur community. The preservational bias suggested by previous workers for drought assemblages is seemingly substantiated within the richly fossiliferous strata of the Two Medicine Formation.
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GROUND sloths (Gravigrada, Xenarthra) are known from middle or late Oligocene to late Pleistocene in South America1 and from late Miocene to late Pleistocene in North America2. They are medium to gigantic in size and have terrestrial3 habits. Discovery of abundant and well preserved remains of a new sloth (Thalas-socnus natans), in marine Pliocene deposits from Peru4–6 drastically expands our knowledge of the range of adaptation of the order. The abundance of individuals, the absence of other land mammals in the rich marine vertebrate fauna of the site5,6, and the fact that the Peruvian coast was a desert during the Pliocene7,8 suggest that it was living on the shore and entered the water probably to feed upon sea-grasses or seaweeds. The morphology of premaxillae, femur, caudal vertebrae (similar to those of otters and beavers) and limb proportions are in agreement with this interpretation.
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A comprehensive taphonomic analysis has yielded a novel interpretation for one of the most famous dinosaur quarries in the world. The Cleveland-Lloyd Dinosaur Quarry (CLDQ) traditionally has been interpreted as an attritional predator trap. This scenario is based largely on a remarkable 3:1 predator:prey ratio, dominated by the remains of the theropod Allosaurus fragilis. This study addresses the taphonomy of CLDQ by combining analyses of fossils and entombing sediments along with putative modern analogues. Thousands of bones have been excavated from CLDQ, representing at least 70 individual dinosaurs from a minimum of nine genera. The fossils occur in a 1-m-thick fine-grained calcareous mudstone interpreted as a floodplain ephemeral-pond deposit. The bones show minimal carnivore modification and surface weathering, whereas approximately 1/3 of the elements studied possess pre-depositional fractures and evidence of abrasion. The vast majority of elements are found horizontal to subhorizontal, without a preferred long-axis orientation. The demographic profile of the CLDQ dinosaur assemblage appears to be highly skewed toward subadult individuals. Numerous lines of evidence question the traditional predator-trap hypothesis. Of the alternatives, catastrophic drought appears to be most consistent with available data. Evidence includes a large assemblage of animals in a low-energy ephemeral-pond depositional setting and geologic and biologic evidence of desiccation. Additional support comes from modern drought analogues that frequently result in mass-death assemblages of large vertebrates. Climatic interpretations during Late Jurassic times are consistent with a semiarid environment characterized by periodic drought conditions.
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The unique collection of fossils obtained from the asphalt deposits of Rancho La Brea has no parallel among the numerous records of the past life of the earth brought to light by the paleontologist and geologist. Closest approach in age, nature of preservation, and in kinds of materials preserved is made by two additional brea occurrences in California; one located at Carpinteria, Santa Barbara County, the other at McKittrich, in Kern County. Dating from a period not very remote in earth history, yet possessing presumably considerable antiquity as measured in terms of years, the collection from Rancho La Brea furnishes a basis for reconstruction of a remarkably clear picture of life as it existed in the Los Angeles region of Southern California in late geologic time. Among the outstanding features of the Rancho La Brea collection are the great wealth of material, the unusual variety of the species, and the fine state of preservation of the remains. The abundance of well-preserved skulls and skeletal elements makes it possible to prepare mounted skeletons of many of the characteristic mammals and birds. The specimens displayed in Hancock Hall of the Los Angeles County Museum are but a part of the collection obtained from the asphalt. In not a few types, individual skulls and parts of skeletons are duplicated many times by specimens not on exhibition. More than 200 different kinds of animals and plants are now known from Rancho La Brea. To this list probably other forms will be added as the study of the entire assemblage progresses. It is not surprising, therefore, that the occurrence and collection have aroused considerable interest on the part of the scientific specialist and of the layman. Much intensive research during the past fifty years has resulted in the accumulation of a fund of information relating to these deposits and their exhumed organic remains. This knowledge has been shared with the intelligent observer to whom fossils no longer make an appeal merely as objects of curiosity or as "Medals of Creation." The present review of our knowledge of these deposits and of their record of life is intended to further this interest and to serve the needs of the daily visitor to the exhibit hall of the Los Angeles County Museum and the site of Rancho La Brea.
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Sixteen taxa comprising extinct megafauna and extant species from a single asphalt deposit (Project 23, Deposit 1) at Rancho La Brea were isotopically analyzed (δ¹³C, δ¹⁵N, δ³⁴S) and ¹⁴C dated to investigate paleoecology and feeding behavior of terrestrial vertebrates in southern California during the late Pleistocene. The large majority of the ¹⁴C dates cluster between ~35 and 36 kyr BP, but a range of ages indicate this seep was active from ~30 to >43 kyr BP. Many of the Smilodon fatalis and Canis dirus as well as the Canis latrans have similar δ¹³C (~–19‰ to −18‰) and δ¹⁵N (~11‰ to 12‰) results, indicating that these predators may have consumed similar prey species and possibly competed with each other through hunting and/or scavenging. The remains of contemporary potential prey species for these three predators include juvenile Bison antiquus and Camelops hesternus, and possibly adult Paramylodon harlani and Capromeryx minor. However, the δ¹⁵N results of a single C. dirus (8.9‰) and the Panthera atrox (8.3‰) were significantly lower than the other large predators. Potential prey for this dire wolf and lion include Nothrotheriops shastensis, Equus occidentalis and possibly Mammut americanum. Many of the herbivores appear to have utilized broadly similar C3 ecological environments. However, the adult E. occidentalis had isotopic results similar to the Sylvilagus sp. and Spermophilus beecheyi that have restricted home ranges, suggesting this horse was similarly local in its distribution or consumed a similar plant food selection. The isotopic values for extant taxa (Actinemys marmorata, Crotalus sp., Mustela frenata) suggest similar dietary patterns to their modern counterparts, indicating their ecological niches have remained relatively constant. The results presented here establish a foundation for future diachronic studies to better understand how the climate of the last ~50 kyr BP impacted biodiversity and ecological communities in southern California.
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Stable isotope analysis of the first fossilized Eremotherium laurillardi remains from Belize offers valuable insights into the conditions within which this individual lived and its ability to adapt to the increasing aridity of the Last Glacial Maximum (LGM). Cathodoluminescence (CL) microscopy was used to identify chemical alteration of the tooth during fossilization. Results demonstrate that the inner orthodentin resists diagenesis, yielding potentially unaltered values. Using an intensive "vacuum milling" technique, the inner orthodentin produced an accelerator mass spectrometry (AMS) date of 26,975 ± 120 calibrated years before the present. The stable carbon and oxygen isotope analysis of this layer shows that the tooth recorded two wet seasons separated by one longer dry season and that this sloth was able to adapt its diet to the marked seasonality of the LGM. This study offers new insights into obtaining reliable isotope data from fossilized remains and suggests that this individual adapted to climate shifts, contributing to the conversation surrounding megafauna extinction.
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A recurrent aspect of the fossil record is the observation of a disproportionate number of specimens or individuals of a single taxon in some deposits, which is stated as dominance. Commonly, the dominance is explained as the result of catastrophic or short-term mass death events or are proxies for palaeoecological inferences regarding gregariousness. However, taphonomic, stratigraphic and chronologic analyses of fossiliferous deposits have shown that this is not always true. To contribute to the study of dominance in fossil assemblages, we describe a probable Quaternary skeletal accumulation dominated by the extant gregarious rock-dwelling rodent Kerodon rupestris recovered from Sumidouro do Sansão, a 65m deep pitfall cave in northeast Brazil, and discuss the palaeoecological implications of our findings. We provide taxonomic identification, taphonomic analyses, and chronological assessment. Besides K. rupestris (minimum number of individuals, MNI=35), we recorded three taxonomic groups, that are the ground sloth Catonyx cuvieri (MNI=1), the anteater Tamandua tetradactyla (MNI=1), and the cougar Puma concolor (MNI=1). The taphonomic analysis of the K. rupestris remains supports the idea that entrapment of individuals was the main process of bone accumulation and that the death of cave inhabitants followed by short transport to the main hall possibly occurred. Kerodon rupestris remains persisted on the surface of the cave deposit for different time spans and were exposed to fragmentation, weathering, invertebrate boring and encrustation inside the cave environment. Direct dating suggests differences in the ages obtained and intermittent deposition of the individuals inside the cave. It highlights the influence of taphonomic controls on gregarious taxa, such as K. rupestris, towards dominating attritional time-averaged assemblages.Furthermore, it demonstrates that such assemblages do not necessarily support inferences about single event mortality and gregariousness of the dominant taxon.
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Bones of recent mammals in the Amboseli Basin, southern Kenya, exhibit distinctive weathering characteristics that can be related to the time since death and to the local conditions of temperature, humidity and soil chemistry. A categorization of weathering characteristics into six stages, recognizable on descriptive criteria, provides a basis for investigation of weathering rates and processes. The time necessary to achieve each successive weathering stage has been calibrated using known-age carcasses. Most bones decompose beyond recognition in 10 to 15 yr. Bones of animals under 100 kg and juveniles appear to weather more rapidly than bones of large animals or adults. Small-scale rather than widespread environmental factors seem to have greatest influence on weathering characteristics and rates. Bone weathering is potentially valuable as evidence for the period of time represented in recent or fossil bone assemblages, including those on archeological sites, and may also be an important tool in censusing populations of animals in modern ecosystems.
Article
Large cats, canids, bears, and hyenas create distinctive types of damage when they gnaw bones. This paper describes the diagnostic characteristics of damage done by each taxon to femora and tibiae of herbivores with body weights = or >300kg. Pleistocene and Recent fossil collections that include gnawed bones might provide data on the presence of carnivores whose own remains are not found in the collections. Information might also be gained about predator and scavenger utilization of prey carcasses, often a reflection of prey vulnerability or availability in past communities.-Author
Article
Discusses a karstic site containing teeth, tusks, skulls and postcranial skeletal elements of mammoth. The site is especially interesting as it involved the live entrapment of mammoth rather than an accumulation of dead remains. The mammoths died by drowning or starvation after slipping or falling into a sink hole, and being trapped by steep and slippery walls. The remains therefore represent a cross-section of the healthy population. Spiral fractures, often cited as evidence of man, are common, although there is no evidence of man at this site. -T.M.Kennard
Article
Nonmarine lower Miocene rocks widely exposed in nearly continuous outcrop over approximately 3100 km2 (1,200 mi2) of the Hartville Table in southeastern Wyoming and western Nebraska indicate a semiarid continental interior, with seasonal climate characterized by sandy ephemeral or intermittent braided streams, interchannel plains mantled by fine-grained volcaniclastic loess, and shallow ephemeral holomictic lakes. These paleoenvironments are recognized on the basis of distinctive sedimentologic, faunal, and taphonomic characteristics. Stream sediments (10 percent or less of total outcrop) are primarily tuffaceous silty sandstones, deposited as reworked pyroclastic debris in wide shallow valleys. These valleys first filled with fluvial fine-grained volcaniclastics, but with the cessation of streamflow in the region, filling was completed by air-fall volcaniclastic loess that blanketed both valleys and interchannel reaches. Fluvial sediments within the valleys include much spatially dispersed mammal bone that had been scavenged and subaerially weathered prior to burial. Waterholes, situated in or adjacent to the valleys, filled with tuff and carbonate mud containing freshwater ostracods, pulmonate gastropods, diatoms, and charophyte algae. These tuffaceous waterhole muds intertongue with fluvial volcaniclastic sediments and are the locus of major mammalian bone beds, the best known preserved at Agate Fossil Beds National Monument. Bones of chalicothere, rhinoceros, and entelodont are common in waterhole bone beds and in fluvial sediments in the region. Massive tuffaceous air-fall silty sandstones (87 percent of outcrop) punctuated by silcrete paleosols were deposited in the interchannel reaches; mammal remains are commonly represented by widely scattered, isolated bones and partial skeletons of young and aged ungulates, chiefly oreodonts and camels, indicative of attritional deaths over time. No bone beds occur. Thin silicified carbonate mudstones (about 2 percent of outcrop) with ostracods, plant debris, and aquatic pulmonate gastropods (but without fish or other aquatic vertebrates) indicate shallow, holomictic, ephemeral lakes that filled with homogeneous micrite mud. These lakes were isolated sheet-like bodies of water unassociated with stream sediments. Following desiccation, lacustrine sediments were commonly overprinted by pedogenic features. Eolian transport of fine pyroclastic detritus into the North American midcontinent was essential to preservation of these sedimentary environments and their rich fossil record. In the Americas and in Africa during the Cenozoic, fine-grained volcaniclastic sediments blanketed large geographic areas within the continental interiors, preserving significant temporal intervals of the vertebrate fossil record. If volcanism had not occurred, these intervals would exist as major hiatuses in our knowledge of vertebrate, particularly mammalian, evolution. The important role of fine-grained volcaniclastics in preservation of mammalian faunas and their associated depositional environments in the Americas and in Africa during the Cenozoic deserves greater emphasis.
Article
This article begins with a description of excavations in the Las Vegas type site on the Santa Elena Peninsula, Ecuador. A pre-Las Vegas phase (11,000 to 10,000 B.P.) is defined provisionally, and the Early Las Vegas (10,000 to 8000 B.P.) and Late Las Vegas (8000 to 6600 B.P.) phases are described from artifacts, burials, settlement data, faunal remains, pollen, and phytoliths. The Las Vegas people were unspecialized hunters, fishermen, and gatherers living in a littoral zone who added plant cultivation to their subsistence system before 8,000 years ago. Evidence for bottle gourd (Lagenaria siceraria) and primitive maize (Zea mays L.) was found in the Las Vegas type site. The differences between the modern, semiarid environment and the environment of the preceramic period are accounted for without hypothesizing climatic change. Las Vegas is interpreted as a local manifestation of an early tropical forest cultural tradition out of which developed the ceramic-stage cultures of the Ecuadorian coast.
Article
Determination of whether a particular age profile derived from a sample of prehistoric bones represents catastrophic or attritional mortality depends largely on the frequencies of age classes. Analyses of mortality profiles derived from samples of cervids (Odocoileus hemionus and Cervus elaphus) that died catastrophically in the Mount St. Helens blast zone indicate that a minimum sample of 30 individuals is required for a reliable inference of mortality pattern when a newborn individual of the taxon of concern has an average life expectancy of about three years. This conclusion is corroborated by drawing 16 random samples of various sizes from two paleontological faunas, each consisting of one taxon, one with a life expectancy similar to and the other with a life expectancy different from the Mount St. Helens cervids. Pre-eruption survivorship of the Mount St. Helens cervids was controlled by an estimated 20% annual harvest rate. Comparison of simulated survivorship in nonhunted cervid populations with archaeologically documented survivorship may provide insights to effects of prehistoric hunting on animal populations.
Article
African wild dog (Lycaon pictus) predation was observed in Ngorongoro Crater, Tanzania, between September, 1964, and July, 1965, when packs were in residence. The original pack of 21 dogs remained only 4 months, but 7 and then 6 members of the group reappeared in the Crater at irregular intervals. The ratio of males:females was disproportionately high, and the single bitch in the small pack had a litter of 9 in which there was only one female. The pack functions primarily as a hunting unit, cooperating closely in killing and mutual defense, subordinating individual to group activity, with strong discipline during the chase and unusually amicable relations between members. A regular leader selected and ran down the prey, but there was no other sign of a rank hierarchy. Fights are very rare. A Greeting ceremony based on infantile begging functions to promote pack harmony, and appeasement behavior substitutes for aggression when dogs are competing over meat. Wild dogs hunt primarily by sight and by daylight. The pack often approaches herds of prey within several hundred yards, but the particular quarry is selected only after the chase begins. They do not run in relays as commonly supposed. The leader can overtake the fleetest game usually within 2 miles. While the others lag behind, one or two dogs maintain intervals of 100 yards or more behind the leader, in positions to intercept the quarry if it circles or begins to dodge. As soon as small prey is caught, the pack pulls it apart; large game is worried from the rear until it falls from exhaustion and shock. Of 50 kills observed, Thomson's gazelles (Gazella thomsonii) made up 54 percent, newborn and juvenile wildebeest (Connochaetes taurinus) 36 percent, Grant's gazelles (Gazella granti) 8 percent, and kongoni (Alcelaphus buselaphus cokei) 2 percent. The dogs hunted regularly in early morning and late afternoon, with a success rate per chase of over 85 percent and a mean time of only 25 minutes between starting an activity cycle to capturing prey. Both large and small packs generally killed in each hunting cycle, so large packs make more efficient use of their prey resource. Reactions of prey species depend on the behavior of the wild dogs, and disturbance to game was far less than has been represented. Adult wildebeest and zebra (Equus burchelli) showed little fear of the dogs. Territorial male Thomson's gazelles, which made up 67 percent of the kills of this species, and females with concealed fawns, were most vulnerable. The spotted hyena (Crocuta crocuta) is a serious competitor capable of driving small packs from their kills. A minimum of 4-6 dogs is needed to function effectively as a pack. It is concluded that the wild dog is not the most wantonly destructive and disruptive African predator, that it is an interesting, valuable species now possibly endangered, and should be strictly protected, particularly where the small and medium-sized antelopes have increased at an alarming rate.
Article
Of the four late Pleistocene and early post-Pleistocene lithic complexes defined by Edward P. Lanning, only one, the Las Vegas complex, is supported by existing evidence from the Santa Elena Peninsula of southwest Ecuador. The Achallan culture, previously defined by Stothert and assigned to the post-Las Vegas period, is now unsupported by satisfactory evidence.
Article
Biological, stratigraphic, and temporal processes act on the origin of fossil concentrations. The influence of these phenomena on fossil vertebrate accumulations from tank deposits recently began to be analyzed in detail. This paper documents taphonomic patterns recognized in the late Pleistocene fossil vertebrate accumulation from a tank deposit of Lage Grande Paleontological Site (LGPS), Pernambuco State, northeastern Brazil. The preservation observed in LGPS differs strongly from the expected for tank accumulations and, given the high quality of preservation and the low rate of time-averaging inferred (indicated by the low degrees of surface bone modifications), it seems reasonable that LGPS accumulation reflects nearly non-biased biocenotic patterns. Under this hypothesis, Eremotherium laurillardi was the most abundant species in the region of Lage Grande during the late Pleistocene, similarly to other areas with tank deposits. Surprisingly, cingulates were rare or absent. Non-mammalian vertebrates and Glossotherium were rare in that area. Taphonomic signatures indicate that the thanatocoenosis of Lage Grande experienced a short time span of subaerial exposure prior to burial and short transport to inside the tanks by debris-flows. Thus, LGPS accumulation can be classified as parautochthonous. Besides the inferred rapid burial of the LGPS assemblage, when compared to other tank accumulations, another feature that may had generated the peculiar taphonomic setting of LGPS accumulation is the uncommon pond-like morphology of this deposit. Morphology of the tanks may be one additional factor responsible for differential preservation of vertebrates in this kind of deposit.
Article
Marine sediments from 3°37′S, 83°58′W yield a well-dated pollen record of equatorial Andean vegetation. Moderate development of Podocarpus -high montane rainforest (∼34,000-28,000 yr B.P.) and increase of high Andean grassland pollen (∼28,000-16,000 yr B.P.) imply an extended dry, cool glacial period following a brief interstade. Rapid stepwise expansion in coastal and montane forest pollen characterizes the deglacial interval. The general correspondence between pollen and oxygen isotope variations in Tri 163-31B suggests that tropical climatic variations in the northern Andes were basically coherent with northern hemisphere glacier variations.
Article
This work analyses the origin and taphonomy of three Plio-Pleistocene mammal assemblages from the Guadix-Baza basin (Granada, Spain): Huélago; Huéscar-1; and Cúllar de Baza-1. Similarities and differences in the taphonomic features are evaluated with regard to marginal lacustrine sedimentary processes involved in the accumulation of these mammal assemblages. Selective preservation of skeletal-part and taxa in relation to facies have been explored to determine their suitability for palaeoecological analysis. The mortality in Cúllar de Baza-1 and Huélago-1 corresponds to a catastrophic pattern, but other taphonomic features of the bones indicate that accumulation processes were diachronic as occurred in Huéscar-1. This could be explained by selective-predation and/or seasonal accumulation of bones. Hydraulic sorting and transportation greatly controlled the size and shape of accumulated skeletal elements, and the different preservational circumstances of each environment largely constrained the taxonomic composition of the fossil bone assemblages. Autochthonous fauna only occurs in Huéscar-1 corresponding to subaquatic environments. The absence of carnivores among the identifiable remains from Huélago-1 has no plausible taphonomic or sedimentological explanation. Nevertheless, after taking into account the taphonomic factors, the differences in taxonomic composition between these three mammal assemblages reflect differences in the surrounding habitats. The great diversity of ruminant artiodactyls, in particular browsers, is indicative of wooded or bushy areas in the surroundings of Huélago-1 although not in the immediate area of the lake margin. This diversity coincides with that observed in other Villafranchian localities and represents the greatest diversity of artiodactyls known from the Neogene and Quaternary record of Western Europe. In turn, the high diversity of sub-aquatic forms and a smaller variety of artiodactyl species in Huéscar-1, reflects an open, sparsely forested environment susceptible to seasonal drought. A similar sparse forested environment has been deduced for Cúllar de Baza-1. The climate and environmental conditions in Huéscar-1 and Cúllar de Baza-1 are consistent with a climatic deterioration at the beginning of the Middle Pleistocene (‘Glacial Pleistocene’).
Article
The remains of 400 or more Permian amphibians were found in a series of siltstone channels confined to an area 50 feet square. The fossils include 90 per cent Diplocaulus, 8 per cent Trimerorachis, and 2 per cent other types. The channels are thought to be the remnants of a drying watercourse in which aquatic amphibians were concentrated by drought. The absence of fish remains suggests that the fishes died at an earlier stage of the desiccation of the stream. Absence of Eryops and amphibians of more terrestrial habits indicates that these forms left the water for more suitable habitat. The fossils are mostly or entirely of heavy-bodied, weak-limbed forms that probably could not walk about on land.
Article
We report taphonomic and palaeoecologic data on the rich, diverse and well preserved assemblage of large mammals from lower Pleistocene deposits at Venta Micena (Orce, Granada, south-east Spain). The biostratinomic and diagenetic characteristics of the assemblage are congruous with the sedimentary context deduced from the study of the site, and both confirm that: (i) the assemblage represents an accumulated taphonomic stage, (ii) it was formed by demic, autochtonous palaeobiologic entities, which were preserved and recorded in situ, and (iii) it is the result of biological processes and agents. Interspecific analysis of size/abundance patterns in ungulates shows that the main taphonomic bias affecting the bones was produced by biological destruction before burial, and that the loss of information was greater for species of smaller body size. Factor correspondence analysis was used to compare the frequencies at which some groups of postcranial elements are represented in several recent and archaeological bone assemblages accumulated by carnivores, rodents and hominids. The results obtained strongly suggest that the bones from Venta Micena were collected mainly by hyaenids, which deposited them near shallow dens excavated around the ponds that surrounded the Pleistocene lake of Orce. An analysis of the abundance of major long bones has shown that differential fragmentation was produced by hyaenas as a function of their structural density and mean marrow content. All these data allow to formulate a descriptive-quantitative model for the characterization of bone assemblages generated from hyaenid activity, in which Venta Micena is an example of bone concentration and modification activities by Pachycrocuta brevirostris. Strong selection of prey by carnivores (which killed preferably juveniles, females and individuals with diminished locomotive capabilities among ungulate prey species of larger body size) is indicated by (i) the abundance of juvenile individuals with deciduous teeth in relation to the average weight estimated for adults in each ungulate species, by (ii) the U-shaped attritional mortality profiles deduced from crown heigth measurements, by (iii) the presence of many metapodials with different osteopathologies, and by (iv) a biased sexual ratio deduced from the metacarpals of large bovids. Comparison between the frequencies in which modern African carnivores kill and scavenge ungulates from different size classes and the abundance of these size categories in the assemblage suggests that the Venta Micena hyaena was a bone-cracking scavenger which fed largely on carcasses of ungulates preyed upon and partially consumed by flesh-eating carnivores such as saber-toothed felids and wild dogs.
Article
A paleomegafauna site from central Amazonia with exceptional preservation of mastodons and ground sloths allows for the first time a precise age control based on 14C analysis, which, together with sedimentological and δ13C isotope data, provided the basis to discuss habitat evolution within the context of climate change during the past 15,000 yr. The fossil-bearing deposits, trapped within a depression in the Paleozoic basement, record three episodes of sedimentation formed on floodplains, with an intermediate unit recording a catastrophic deposition through debris flows, probably favored during fast floodings. The integrated approach presented herein supports a change in humidity in central Amazonia through the past 15,000 yr, with a shift from drier to arboreal savanna at 11,340 (±50) 14C yr B.P. and then to a dense forest like we see today at 4620 (±60) 14C yr B.P.
Article
New remains of Eremotherium were recovered from the Pacific coast of Ecuador’s Manabi province. The Machalilla fossiliferous locality records the northernmost presence of Eremotherium along the Pacific coast of South America. Most of the fossil remains belong to the same individual, mainly its posterior half, but other individuals are represented. Among the better-preserved specimens are skull fragments, most of the hind limb bones and a number of trunk and caudal centra. These remains were compared with samples collected during the 20th century along the southern coastal regions of Ecuador and northern Peru. Many characters of the long bones and tarsals testify to a possibly different lineage despite the closeness of other Eremotherium populations. Some metric and morphological aspects suggest a different space-temporal southern Caribbean provenance. Other Eremotherium specimens, coming from other Ecuadorian localities, were studied and compared with classic Eremotherium samples. Interesting morpho-functional aspects are pointed out with regard to the tail and its importance in the bipedal stance.
Article
Preliminary identification of insect fragments obtained by washing the matrix from the Pleistocene tar-seeps of Talara, northwest Peru, shows that the order Coleoptera is represented by the families Hydrophilidae, Dytiscidae, Gyrinidae, Scarabaeidae, Tenebrionidae, Curculionidae, Carabidae, and possibly Haliplidae, Silphidae, Dermestidae, Histeridae, Cicindelidae, and Cerambycidae, The orders Lepidoptera and Orthoptera are represented by the families Sphingidae and Acrididae respectively. The insect fauna exhibits distinct resemblances to that of the Pleistocene tar-seeps of Rancho La Brea, California. Similarity in climatic conditions during the trapping of animals in both tar-seeps is further supported by the possible ecological interpretations based upon the fauna.