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NEW SPECIES OF HOLMESINA SIMPSON (XENARTHRA, CINGULATA, PAMPATHERIIDAE) FROM THE PLEISTOCENE OF RONDÔNIA, SOUTHWEST AMAZONIA, BRAZIL. The Xenarthra Cingulata is one of the most characteristic groups in the Neotropical region. These American endemic mammals comprise several families, among them, the Pampatheriidae (middle Miocene-early Holocene) which are characterized by sharing traits with both the Dasypodidae and the Glyptodontidae. The genera Pampatherium Gervais & Ameghino and Holmesina Simpson, occur in both North and South America. In North America, the species H. floridanus, H. septentrionalis and P. mexicanum are recorded from the late Pliocene to the Pleistocene, whereas H. occidentalis, H. paulacoutoi, H. majus, P. humboldtii and P. typum are recorded in the Pleistocene of South America. New specie of the genus Holmesina is here proposed based on a skull without mandible found at the locality Araras/Periquitos, right margin of Madeira River, municipality of Vila Nova Mamoré, Rondônia State, from the Rio Madeira Formation (late Pleistocene-Holocene). The new specie differs from the other species of the genera Holmesina and Pampatherium by a series of distinctive morphological and allometric features: markedly slender skull, narrow straight nasals, slightly convex frontals, long parietals, and little developed sagittal crest. The zygomatic arch long and slender, without the large lateral area at orbital level observed in the other species, infraorbital process absent; temporal fossa wide and excavated/ deep; supraoccipital very high, deep, with external occipital crest prominent and lambdoid crest expanded posteriorly; palate narrow, with imbrication molariforms between MF2, MF3 and MF4.

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.

-THE PELTEPHILIDAE (MAMMALIA, XENARTHRA) FROM THE COLLÓN CURÁ FORMATION (COLLONCURAN, MIDDLE MIOCENE), ARGENTINA. The Peltephilidae (early Eocene-late Miocene) are a group of extinct armadillos exclusive from South America, known for having horn-like osteoderms on the nasals and maxillaries. This paper discusses a nomenclatorial proposal for anatomical description of these cingulate osteoderms and describes for the fi rst time specimens of Peltephilidae (Xenarthra, Cingulata) from the Collón Curá Formation (Colloncuran, middle Miocene) of Patagonia (Argentina). The major change in the nomenclature of the osteoderms in Peltephilidae here proposed is to replace the term "central or main fi gure" by "central longitudinal elevation". Finally, by analogy with the living species of Dasypodidae and the extinct Pampatheriidae, some considerations are presented about the relationships between the osteoderm and the overlying epidermal scale in Peltephilidae. The new specimens are assigned to Peltephilidae gen. et sp. indet., Peltephilus pumilus Ameghino and P. nanus Ameghino. The latter two species represent their youngest record and indicate a closer taxonomic affi nity of the Colloncuran age with the previous Santacrucian, instead of the subsequent Laventan and Mayoan.Key words: Peltephilidae, Xenarthra, middle Miocene, Colloncuran, Patagonia, Argentina.RESUMO -Os Peltephilidae (Eoceno inferior-Mioceno superior) são um grupo de cingulados extintos exclusivos da América do Sul, conhecidos por apresentar alguns osteodermos cefálicos diferenciados num par de cornos pré-orbitários. Neste trabalho se discute uma proposta nomenclatural para a descrição anatômica dos osteodermos desses cingulados e se descrevem pela primeira vez restos de Peltephilidae (Xenarthra, Cingulata) para a Formação Collón Curá (Colloncurense, Miocen o médio) da Patagônia (Argentina). A principal mudança na nomenclatura dos osteodermos dos Peltephilidae aqui proposta, é a substituição do termo "fi gura central ou principal" por "elevação central longitudinal". Finalmente, por analogia com as espécies de Dasypodidae atuais e Pampatheriidae são apresentadas algumas considerações sobre a relação entre o osteodermo e a escama epidérmica sobrejacente nos Peltephilidae. Os novos espécimens são atribuídos a Peltephilidae gen. et sp. indet., Peltephilus pumilus Ameghino e P. nanus Ameghino. Os últimos dois registros são os mais recentes para ambas espécies e indicam uma maior afi nidade taxonômica da idade Colloncurense à precedente Santacruzense, do que com as posteriores Laventense e Maioense.

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Pampatheriidae is a group of South American native cingulates recorded from the Middle Miocene to the Early Holocene. These animals arrived in North America during the Great American Biotic Interchange. During the Quaternary, at least three genera existed: Tonnicinctus Góis, González Ruiz, Scillato-Yané and Soibelzon, Pampatherium Gervais and Ameghino, and Holmesina Simpson. They are differentiated mainly by craniodental and osteodermal characters. In this paper, we describe a new species of Holmesina from Bahia state, Brazil. Two well-preserved specimens possessing osteoderms associated with their skeletons enabled us to determine the genus and species more reliably. Holmesina cryptae sp. nov. differs from the other Quaternary pampatheres by having the simplest ornamental pattern of osteoderms, sharing characteristics between Pampatherium and Holmesina osteoderms and the most robust skull among the Holmesina species, however preserving the main synapomorphies of the genus. Moreover, the integrity of the remains of H. cryptae sp. nov. enabled us to describe elements of the hyoid apparatus, the clavicle, the entire vertebral column and the pelvis. It was also possible to measure its total axial length (2.2 m) more reliably, which is smaller than previously estimated for other pampatheres. Holmesina cryptae sp. nov. constitutes the sixth species of the genus, and it is the fourth in South America.

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