On the status of “Urotherium antiquum” (Ameghino) (Xenarthra,Glyptodontidae)

Within the Late Neogene Glyptodontidae of the Pampean region of Argentina, “Urotherium antiquum” was described on the basis of some associated osteoderms of the dorsal carapace, which in addition include a partial skull and left hemimandible. The diagnostic characters are located on the exposed surface of the osteoderms of the dorsal carapace which somewhat resembles those of the Pleistocene genus Neuryurus. Although the relationship of “U. antiquum” to the remaining Glyptodontidae has never been clarified, some cladistic analyses suggest a close phylogenetic affinity with the clade composed of Plohophorus + (Glyptodon + Doedicurus). A careful comparison of “U. antiquum” to well-characterized taxa with similar stratigraphic and geographic provenance reveals that no significant skull differences are observed from Plohophorus figuratus Ameghino. It seems likely that the alleged ornamentation pattern that characterizes this species was produced by a taphonomic alteration of the exposed surface of the osteoderms, a process broadly distributed in glyptodonts having a “rosette” ornamentation pattern. Finally, some characters present in the osteoderms of the type specimen of “U. antiquum” suggest that it may be a juvenile specimen. In summary, “U. antiquum” should be considered a junior synonym of P. figuratus.     

An exceptional Pleistocene specimen of Panochthus Burmeister (Xenarthra, Glyptodontoidea) from Bolivia: Its contribution to the understanding of the Early-Middle Pleistocene Panochthini

Knowledge of the Early-Middle Pleistocene (Ensenadan Age/Stage ; ca. 1.8-0.4 Ma) South American Glyptodontidae (Cingulata) is still poor compared with the Late Pleistocene-Early Holocene taxa (Lujanian Age/Stage). This is especially true for the Glyptodontidae Panochthini, in which it is possible to recognize two Ensenadan species from the Pampean region of Argentina, Panochthus intermedius and P. subintermedius, known only by their type material. Prior to this contribution, the knowledge of P. intermedius, a taxon with biostratigraphic importance for being considered as a guide taxon of the Ensenadan Age/Stage of South America, was limited to a dorsal carapace. The finding of an exceptional almost complete specimen from the Early-Middle Pleistocene of Bolivia has allowed us to greatly improve the morphological characterization of this species, and discuss some taxonomic aspects related to the other Ensenadan Panochthini. This specimen represents the most completely known Panochthini and one of the most complete Glyptodontidae from the Early-Middle Pleistocene of South America.     

First Neogene skulls of Doedicurinae (Xenarthra,Glyptodontidae): morphology and phylogenetic implications

Among Glyptodontidae, Doedicurinae (late Miocene–early Holocene) includes the glyptodonts with the largest size and latest records. Doedicurinae is mainly characterised by a smooth surface of the osteoderms with large foramina, and a particular morphology of the caudal tube. All taxa except one (Doedicurus clavicaudatus) have been recognised and characterised on the basis of remains of caudal tubes and/or dorsal carapaces. This situation produced an evident overestimation of the real diversity of this group, and a taxonomic revision is needed. In fact, no Neogene skulls were known. We present and describe the first two Neogene skulls belonging to Doedicurinae (cf. Eleutherocercus antiquus). The materials come from the El Polvorín and Chapadmalal Formations, in the surroundings of Olavarría and Mar del Plata localities, respectively (Buenos Aires province, Argentina). A cladistic analysis was carried out in order to situate these materials among Glyptodontidae and inferring new synapomorphies at skull level in Doedicurinae. Cf. Eleutherocercus antiquus clusters with the Pleistocene species Doedicurus clavicaudatus showing three unambiguous synapomorphies, which in turn represents the first skull synapomorphies for Doedicurinae. Finally, the presence of cf. Eleutherocercus antiquus in the El Polvorín and Chapadmalal Formations suggests that the stratigraphic distribution of this species could include the Montehermosan–Chapadmalalan interval.     

A tale of two clades: Comparative study of Glyptodon Owen and Glyptotherium Osborn (Xenarthra,Cingulata, Glyptodontidae)

Glyptodon and Glyptotherium represent the most conspicuous taxa of late Neogene and Pleistocene glyptodonts in South America and North America, respectively. The earliest records of Glyptodon in South America are 1.07 Ma (late early Pleistocene, Calabrian), although the possibility that “Paraglyptodon uquiensis” represents a Pliocene specimen of Glyptodon cannot be rejected. Glyptotherium originated from South American ancestry in northern South America or Central America about 3.9 Ma (early late Pliocene, Zanclean) or earlier. The diversity of South American Glyptodon is currently under study, but preliminary evidence would indicate that no more than three species (G. munizi, G. elongatus and G. reticulatus) are valid, plus a possible new Andean species. In turn, according to the updated taxonomy proposed herein, Glyptotherium includes two chronospecies. The earliest species, Gl. texanum, differs only slightly from the latest species, Gl. cylindricum. The relationship of Glyptodon and Glyptotherium has been problematical since the discovery of the North American lineage, at first identified as various species of Glyptodon and later considered a separate genus. Glyptodon is recognized as a natural group and recent taxonomic and phylogenetic revisions place all North American glyptodontines into Glyptotherium. In this paper, we propose a detailed morphological comparison between the southern South American species of Glyptodon and Glyptotherium in order to identify diagnostic differences and potential synapomorphies. Both genera can be distinguished mainly by differences in the skull, mandible, dentition, dorsal carapace, and caudal armor, Glyptodon being somewhat larger than Glyptotherium. Both clades show a highly conservative evolution, which could be interpreted as an anagenesis. The scarce records of glyptodonts in Central America show more morphological affinity with Glyptotherium than with Glyptodon.     

North American Glyptodontines (Xenarthra, Mammalia) in the Upper Pleistocene of northern South America

The Glyptodontidae is one of the most conspicuous groups in the Pleistocene megafauna of the Americas. The Glyptodontinae were involved in the Great American Biotic Interchange (GABI) and their earliest records in North America are about 3.9 Ma, suggesting an earlier formation of the Panamanian landbridge. Taxonomically it is possible to recognize two Pleistocene genera of Glyptodontinae:Glyptodon (ca. 1.8 – 0.008 Ma), restricted to South America, andGlyptotherium (ca. 2.6 – 0.009 Ma), including records in both North and Central America. Here we present the first report of the genusGlyptotherium in South America, from the Late Pleistocene of several fossil localities in Falcón State, northwestern Venezuela. A comparative analysis of the material, represented by cranial and postcranial parts, including the dorsal carapace and caudal rings, suggests a close affinity withGlyptotherium cylindricum (Late Pleistocene of Central Mexico). This occurrence in the latest Pleistocene of the northernmost region of South America Supports the bidirectional faunal migration during the GABI and the repeated re-immigration from North America of South American clades, as has been reported in other members of the Cingulata (e.g., Pampatheriidae).      

The southernmost record of a Neuryurini Hoffstetter, 1958 (Mammalia,Xenarthra, Glyptodontidae)

In this contribution we document the southernmost and probably the oldest record of the tribe Neuryurini (Glyptodontidae). The southernmost record of this tribe outside of Patagonia is Neuryurus sp. from Lujanian sediments (Luján Formation, late Pleistocene–early Holocene) at Quequén Grande River (Buenos Aires Province, Argentina). The first and only previous record of a specimen of the Neuryurini in Patagonia was reported from the upper levels of the Puerto Madryn Formation (Huayquerian SALMA, late Miocene), exposed in Península Valdés (Chubut Province, Argentina). The new specimen described here and assigned to an indeterminate Neuryurini was recovered at Estancia La Peninsular (Santa Cruz Province, Argentina). This locality has been recognized in geological studies as part of the Santa Cruz Formation (Santacrucian SALMA, late early Miocene), but there have been no fossils described from this site until now. Therefore, the new specimen represents, with the two confirmed records of Glyptodon Owen and Panochthus Burmeister (both from the Quaternary), the only non-Propalaehoplophorinae glyptodontids reported for Santa Cruz Province.     

On the taxonomic status of some Glyptodontidae (Mammalia,Xenarthra, Cingulata) from the Pleistocene of South America

The anatomical and taxonomic knowledge of some groups of Glyptodontidae (Mammalia, Cingulata) is still very poor. In addition, a strict typological/morphological taxonomic criterion was used in recognizing many taxa, especially during the second half of the 19th century and the first of the 20th century. This particular situation resulted in a clear overestimation diversity, mainly with respect to the South American glyptodonts. In this scenario, this paper analyzes the taxonomic status of some Glyptodontinae through a precise comparative study with well characterized taxa. The main results show that the genera Pseudothoracophorus Castellanos (P. depressus) and Chlamydotherium Lund, one species of the genus “Boreostracon” Simpson (B. corondanus), and one species of the genus Glyptodon Owen (G. falkneri), actually represents juvenile specimens referable to Glyptodon Owen; the genus Neothoracophorus Ameghino (N. elevatus) could be related either to Glyptodon Owen or Glyptotherium Osborn. Another species, Heteroglyptodon genuarioi, presents an almost identical morphology compared with the recognized species of Glyptodon (e.g. G. munizi and G. reticulatus). In this sense, the diagnostic characters described for Glyptodon perforatus Ameghino, a taxon with biostratigraphic relevance since it is characteristic of the Lujanian Age/Stage (late Pleistocene-early Holocene), are also present in other species of Glyptodon, especially G. reticulatus and G. clavipes, very frequent taxa in southern South America.     

Sunosuchus (Archosauria, Crocodyliformes) from the Toutunhe Formation (Middle Jurassic) of the Southern Junggar Basin (Xinjiang, NW-China)

A new specimen of the widespread Middle Jurassic to Lower Cretaceous Asian gonipholidid crocodilian genus Sunosuchus is described on the basis of a partial skeleton from the Upper Toutunhe Formation (Middle Jurassic, ?Bathonian-Callovian) of Liuhonggou, SW of Urumqi, Xinjiang Uygur Autonomous Region, People’s Republic of China. The specimen is represented by a partial mandible, teeth, vertebrae, limb and girdle bones and osteoderms. It can be distinguished from other nominal species of the genus by a unique combination of characters: slightly heterodontous dentition, strongly sculptured posteroventral part of the mandible, short fenestra mandibularis, convex dorsal surface of the retroarticular process, keeled cervical vertebral centra and ventral osteoderms with a distinctive sculpture of wide pits and narrow ridges. The heterodontous dentition is a potential autapomorphy of this form. The new specimen is closest in morphology to material described recently from the Callovian of Kirghisia as Sunosuchus sp. It represents the second Middle Jurassic record of the genus, the first crocodile from the Toutunhe Formation, the first substantial crocodile find from the Mesozoic of the Southern Junggar Basin, and the first Middle Jurassic record of Sunosuchus from China. This extends both the paleobiogeographical distribution of the genus in Asia and its stratigraphic distribution in China considerably.     

Comparative paleohistology in osteoderms of Pleistocene Panochthus sp. Burmeister, 1886 and Neuryurus sp. (Xenarthra,Glyptodontidae)

Xenarthran osteoderms are integumentary bones with high fossilization potential presenting a high degree of morphological and histological diversity. Here, new data on the osteoderms histology of two glyptodonts, Panochthus and Neuryurus are presented. The poor spatial organization of the mineralized fibers and a large trabecular area in the middle zone identified in Neuryurus indicate a different bone pattern than the one found in Panochthus, which is mainly characterized by a middle zone with less spongiosa. Through the Bone Profiler program, the degree of compactness of the specimens was obtained, with about 70% for Neuryurus sp. and approximately 90% for Panochthus sp., showing the difference in bone pattern. These values confirm the visible difference in the histological patterns of these taxa, especially in the middle zone. This work demonstrates the microstructural variation studied in osteoderms and shows the importance of paleohistology as a starting point for a better understanding of extinct taxa.     

Caracterización microfaunística de una transgresión marina : Formación Agrio (Cretácico inferior), Cuenca Neuquina, Argentina

Distinctive sedimentological and micropalaeontological responses characterise the basal interval of the Agrio Formation (Valanginian) in central-western Argentina, which is associated to a transgressive event. The effect of the sea-level rise is interpreted from the record of abundant radiolarians and the widespread marlstone and limestone deposits associated with eutrophication of surface waters and development of low-oxygen conditions on the sea-floor. Such a situation accords with pyrite and organic matter rich laminated sediments, as well as with a monotypic foraminiferal assemblage of Epistomina. Bi/plano-convex trochospiral test, epifaunal/semi-epifaunal microhabitat, and deposit-feeding trophic strategy are favourable features for adaptation of this genus to oxygen depressed sea-bottom conditions. The large size of the test could be related to chemolithotrophic bacterial symbionts. Epistomina loncochensis nov. sp. BALLENT is described.     

A Peculiar New Pampatheriidae (Mammalia: Xenarthra: Cingulata) from the Pleistocene of Argentina and Comments on Pampatheriidae Diversity

Pampatheriidae are a group of cingulates native to South American that are known from the middle Miocene to the lower Holocene. Two genera have been recognized between the lower Pleistocene and the lower Holocene: Pampatherium Gervais and Ameghino (Ensenadan, Bonaerian and Lujanian, lower Pleistocene–lower Holocene) and Holmesina Simpson (Blancan, Irvingtonian, upper Pliocene–lower Holocene). They have been mainly differentiated by their osteoderm morphology and cranio-dental characters. These taxa had a wide latitudinal distribution, extending from the southern part of South America (Península Valdés, Argentina) to North America (Florida, USA). In this contribution, we describe a new genus and species of Pampatheriidae for the lower and middle Pleistocene of Buenos Aires Province and for the upper Pleistocene of Santa Fe Province (Argentina).The new taxon is represented by disarticulated osteoderms, one skull element, two thoracic vertebrae and a right femur and patella. It has extremely complex osteoderm ornamentations and particular morphological characters of the cranial element and femur that are not found in any other species of the family. This new taxon, recorded in the lower–middle Pleistocene (Ensenadan Stage/Age) and in the upper Pleistocene–early Holocene (Lujanian Stage/Age), is incorporated to the Pleistocene mammal assemblage of South America. Finally, the Pampatheriidae diversity is greater during the Lujanian Stage/Age than the Ensenadan Stage/Age.     

Mammals in Last 30 to 7 ka Interval (Late Pleistocene-Early Holocene) in Southern Uruguay (Santa Lucía River Basin): Last Occurrences,Climate, and Biogeography

Fossiliferous Quaternary sedimentary beds in the Santa Lucía Basin (southern Uruguay) are potentially useful for the study of the last occurrences of extinct taxa, as well as the environmental and climatic patterns in the late Pleistocene to the early Holocene. They have provided a chronological framework (AMS ¹⁴C and Optically Stimulated Luminescence dates), a mammalian diversity and interpretations of last occurrence, the climatic-environmental setting, and some associated biogeographic processes. The ages produced encompass the last 30 to 7 ka interval (latest Pleistocene-early Holocene). The mammalian assemblage (36 genera, 24 species) includes typical South American late Pleistocene mammals, extinct species of extant genera, and some extant species that still exist elsewhere on the continent. The preservation pattern includes articulated and semi-articulated skeletons of large and small mammals. The presence in the southern Uruguayan Pampean area of some mammals currently inhabiting Patagonia, northwest and central Argentina (Dolichotis, Galea, Microcavia, Chaetophractus, Lagostomus, and Vicugna) is explained by the predominance of open areas and cold climates associated with the Last Glacial Maximum. The mammalian record depicts local extinctions or shifting ranges occurring in latest Pleistocene or early Holocene. The sedimentary chronological framework and taphonomic features suggest the persistence into the early Holocene of Eutatus seguini, Morenelaphus brachyceros, Equus neogeus, Hemiauchenia sp., Lama sp., and Vicugna sp. Glyptodon and Glossotherium seem to persist at least to the latest Pleistocene. This pattern can substantiate the hypothesis that some megafauna and large mammals persisted for some millennia alongside people with extinction occurring before, during, and after human colonization.     

The oldest South American tuco-tuco (late Pliocene,northwestern Argentina) and the boundaries of the genus Ctenomys (Rodentia,Ctenomyidae)

A new species of Ctenomyidae from the late Pliocene of Uquía Formation (northwestern Argentina) is described. The new remains consist of a fragmentary rostrum, and a left mandible with partial lower dentition. Its phylogenetic affinity and morphological specializations for tooth-digging support its assignation to the South American rodent genus Ctenomys. In this context, we highlight the importance of unique morphological specializations for the delimitation of genera within an intrafamilial clade in which similar adaptive strategies could have evolved more than once. The new materials are the oldest fossils for the genus (ca. 3.5 Ma), and their finding in the central Andes agrees with previous hypotheses about the possible area of origin of Ctenomys. They precede by about one million years the presence of Ctenomys chapalmalensis in the Pliocene of the Pampean region of central Argentina, the oldest record previously known for the genus. Nevertheless, the new species does not contribute key information about ancestral character states for the genus beyond those already known through C. chapalmalensis. The phylogenetic, adaptive and even chronological information supplied by these new materials would be linked to the differentiation of the genus rather than to its origin.     

A New Eocene Dasypodid with Caniniforms (Mammalia,Xenarthra, Cingulata) from Northwest Argentina

The aim of this work is to present a new genus and species of Dasypodidae from the Lumbrera Formation (“lower Lumbrera”), early-middle Eocene of Salta Province, northwest Argentina. The new taxon, documented by one specimen, consists of an incomplete skull and jaw with teeth housed in their alveoli, postcranial remains, and isolated osteoderms. Lumbreratherium oblitum, gen. et sp. nov., is characterized by heterodont dentition, with a caniniform as the first tooth, diastema between caniniform and first molariform, teeth with closed roots, and a peculiar morphology of the osteoderms. A phylogenetic analysis indicates that Lumbreratherium oblitum, gen. et sp. nov., and Pucatherium parvum belong to a monophyletic clade in a basal position within the Cingulata. The singularity of the morphological characteristics of these Paleogene armadillos of northwest Argentina reinforces the hypothesis of an intertropical origin of mammal clades different from those of the Paleogene in more austral regions of Argentina.     

A new species of Panochthus Burmeister (Xenarthra,Cingulata, Glyptodontidae) from the Pleistocene of the Eastern Cordillera,Bolivia

Panochthus and Glyptodon are the Pleistocene Glyptodontidae having the greatest range of latitudinal distribution and elevation in South America. The most recent revisions of Panochthus recognized its high taxonomic diversification mainly distributed in the Chaco-Pampean region of Argentina, Uruguay, southern Bolivia and southern and north-eastern Brazil, while the Andean records are poorly known. This contribution aims: (a) to describe a new species of Panochthus from the Pleistocene of the surroundings of Potosi (Bolivia), which represents one of the highest known elevation records for fossil Xenarthra; (b) to carry out a phylogenetic analysis in order to test its location in Panochthus and relationship to some allied genera; (c) to discuss some palaeobiogeographical and morphological implications. The results show that, in agreement with previous studies, Panochthus is a natural group, being Propanochthus the sister taxa. This conclusion agrees, at least in part, with the original interpretation of Burmeister, who recognized Pr. bullifer as belonging to Panochthus. The genera Nopachtus and Phlyctaenopyga are more closely related to some ‘Plohophorini’ than to the clade Propanochthus + Panochthus. Within Panochthus, this new species occupies a relatively basal position as a sister taxon of the clade composed of P. tuberculatus, P. intermedius, and P. greslebini.http://zoobank.org/lsid:zoobank.org:pub:5A766550-DBCA-4C4A-BDB8-602E500E4954     

Osteoderm morphology in recent and fossil euphractine xenarthrans

The presence of osteoderms within the integument, forming a carapace, is one of the most distinctive features of armadillos with the external morphology of these elements forming the basis of most systematic schemes. This is especially true for fossil taxa, where these elements are most frequent in the palaeontological record. A detailed study of osteoderms from the cephalic shield and different regions of the dorsal armour of Chaetophractus villosus (Euphractinae, Xenarthra) was made and compared to those of the extant genus Dasypus (Dasypodinae, Xenarthra), and the extinct genus ?Eutatus. Three distinct histological zones were recognized: outer and inner zones are thin, formed by regular compact bone, the middle zone is thicker, with large cavities that contain mainly adipose tissue, hair follicles, and sweat and sebaceous glands. The internal structure of ?Eutatus (also a member of Euphractinae) osteoderms is close to that of C. villosus, consistent with the notion that these taxa are phylogenetically closely related. In contrast, Dasypus shows marked differences. Dasypus shows hair follicles associated with both gland types (sweat and sebaceous) and connected to foramina on the external surface. Although not observed in adult C. villosus, it has been documented during embryonic development, only to atrophy later in ontogeny. Furthermore, the presence of red bone marrow is rare in C. villosus, but widespread in Dasypus novemcinctus osteoderms. These results suggest an early split of both subfamilies and support the hypothesis that the Euphractinae are more derived than the Dasypodinae.     

Mycoflora of freshly harvested flint corn from Northwestern Provinces in Argentina

A mycological survey was carried out for the first time, on red flint corn samples from the northwestern Andinian region of Argentina in the 1999 and 2000 harvest seasons. Species of the genus Fusarium were the most prevalent component of the flint corn mycoflora present in all provinces.F. verticillioides was the predominant Fusarium isolated in the 1999 harvest season in the the region, and was found at higher incidence level than those observed on commercial semident corn hybrids harvested in the main corn production area in Argentina (Pampean region). During the 2000 harvest season, Fusarium graminearum was most commonly isolated species in Salta province.This revised version was published online in October 2005 with corrections to the Cover Date.