Diego Brandoni

First Megatheriines (Xenarthra, Phyllophaga, Megatheriidae) from the Urumaco (Late Miocene) and Codore (Pliocene) Formations, Estado Falcón, Venezuela

Synopsis Two new genera and species of Megatheriinae are described from the Neogene of Venezuela: Urumaquia robusta gen. et sp. nov. from the Urumaco Formation (Late Miocene) and Proeremotherium eljebe gen. et sp. nov. from the Codore Formation (Pliocene). These represent only the second Tertiary record of the subfamily at low latitudes in South America. The anatomical features of Urumaquia robusta suggest that the levels of the Urumaco Formation bearing the fauna here studied may not be correlated with the Laventan SALMA, but with Chasicoan‐Huayquerian SALMAs.

New remains of Megathericulus patagonicus Ameghino, 1904 (Xenarthra, Megatheriidae): information on primitive features of megatheriines

Abstract New remains of Megathericulus patagonicus Ameghino, 1904, the first additional material of this species found since erection of the species, are described. Two individuals from separate localities, the Cerro Guenguel and Arroyo Pedregoso localities in southern Argentina, are represented. The specimens were recovered from the Río Mayo Fm. and are assigned to the middle Miocene Friasian South American Land Mammal Age. Radiometric dating from the Cerro Guenguel locality indicates an age somewhat younger than 11.8 Mya. Megathericulus patagonicus is the earliest certain megatheriine and the new remains provide information on primitive megatheriine features. Among these are that lower molariforms are mesiodistally compressed, as in the palate of the type specimen; ventral margin of dentary is prominently bulged; angular process approximately in same relative position as in most megatheriines, rather than elevated as in Megatherium species; posterolateral opening of the mandibular canal on anterior edge of base of ascending ramus, posterior to m4, and visible in lateral view; ascending ramus begins approximately at level of distal surface of m4, so that m4 was uncovered in lateral view; inclination of base of ramus suggests that anterior margin of coronoid process inclined less steeply than in other megatheriines; symphysis begins posteriorly well anterior to m1; humerus possesses very prominent deltopectoral crest; in the ulna, proximolateral articular facets face nearly laterally, and olecranon process compressed mediolaterally; in the femur, patellar trochlea contiguous distally with medial and lateral articular facets for the tibia; in the astragalus, navicular facet relatively dorsal, with plane of discoid facet intersecting its middle portion; and fibular facet elongated, reaching the ectal facet.

New mammal faunal data from Cerdas, Bolivia, a middle-latitude Neotropical site that chronicles the end of the Middle Miocene Climatic Optimum in South America

ABSTRACT We provide new and revised identifications of mammals from the early middle Miocene (Langhian age, Colloncuran South American Land Mammal Age [SALMA]) of Cerdas, Bolivia. We also formally name a new typothere notoungulate, Hegetotherium cerdasensis, sp. nov., that can be distinguished by the absence of an external talonid sulcus on m3 and its small size (15–25% smaller than Hegetotherium mirabile). We refer several typothere specimens from Nazareno, Bolivia, to H. cerdasensis, which suggests that the two sites are of similar age. We report the first sparassodont and astrapothere remains from Cerdas. Sparassodont remains include an associated basicranium and mostly complete mandible; the species appears to represent a new, small-bodied borhyaenoid. Astrapothere remains consist of many tooth fragments from a new species of the subfamily Uruguaytheriinae. A partial sloth dentary from Cerdas likely pertains to the subfamily Megatheriinae and is the first report of the family Megatheriidae from the site. A newly discovered peltephilid armadillo specimen includes a partial articulated carapace that supports recognition of the Cerdas taxon as a new species. The two dasypodids of Cerdas (one Euphractini, one Eutatini) represent two new species closely related to undescribed species from the late middle Miocene (Serravallian age, Laventan SALMA) of Quebrada Honda, Bolivia. The mammals of Cerdas indicate that (1) the middle latitudes (southern tropics) contributed significantly to the diversity of Miocene mammal communities in South America; and (2) the Middle Miocene Climatic Optimum was a key factor in the differentiation of South American mammal assemblages.

Additions to the knowledge ofUrumaquia robusta (Xenarthra, Phyllophaga, Megatheriidae) from the Urumaco Formation (Late Miocene), Estado Falcön, Venezuela

We describe new remains ofUrumaquia robustaCarlini, Brandoni & Sänchez, 2006, which significantly improve the knowledge of the species and allow a more precise discussion about the relationships with the rest of the South American Megatheriinae. The new remains (ulna, phalanx, femora, patella, tibia, astragalus, navicular, metatarsals IV–V) described here suggest close affinities of this taxon with the species ofPyramiodontherium and withMegatheriops rectidens, based on morphological similarities of the ulna (length, gracility), femur (general morphology, shape of the medial margin), and astragalus (angle between the discoidal and odontoid facets). In fact, the shape of femoral medial margin is a shared derived character amongUrumaquia, Pyramiodontherium andMegatheriops. However, and despite the increasing information concerning Tertiary species, their phylogenetic relationships are only partially understood.KurzfassungNeue Funde vonUrumaquia robusta Carlini, Brandoni & Sánchez, 2006 werden vorgestellt, die erheblich zum Verständnis der Art beitragen und eine präzisere Diskussion der Verwandtschaftsverhältnisse zu anderen Vertretern der südamerikanischen Megatheriinae erlauben. Das hierin beschriebene neue Material (Ulna, Phalange, Femura, Patella, Tibia, Astragalus, Navikulare, Metatarsalia IV–V) deutet auf nähere Verwandtschaft zu den TaxaPyramiodontherium undMegatheriops rectidens hin. Dies wird unterstützt durch morphologische Ähnlichkeit der Ulna (Länge, Grazilität), des Femurs (generelle Morphologie, Form des medialen Randes) und des Astragalus (Winkel zwischen der Diskoidal- und Odontoidfacette). Tatsächlich handelt es sich bei der Ausprägung des medialen Femurrandes um eine Synapomorphie vonUrumaquia, Pyramiodontherium undMegatheriops. Allerdings sind die phylogenetischen Verwandtschaftsverhältnisse, trotz Zunahme von Informationen über tertiäre Taxa, bisher nur teilweise verstanden.

Mylodon darwini Owen (Xenarthra, Mylodontinae) from the Late Pleistocene of Mesopotamia, Argentina, with remarks on individual variability, paleobiology, paleobiogeography, and paleoenvironment

ABSTRACT The subfamily Mylodontinae, typified by Mylodon, is known from the Colloncuran (late Miocene of Patagonia, Argentina) to the late Pleistocene of South America and North America. Mylodontinae have been recorded during the Pleistocene of Argentina, including the genera Glossotherium, Paraglossotherium, Lestodon, and Mylodon, with Paraglossotherium and Mylodon not as well known as the other genera. In Argentina there have been traditionally four species of Mylodon, M. darwini, M. zeballozi, M. listai, and M. insigne, although the validity of some has been considered doubtful. A nearly complete skull with an associated mandible of Mylodon darwini from the late Pleistocene of Mesopotamia, Argentina, is described. The specimen represents the first record of the species in the Mesopotamian region. The morphometric analysis indicates that M. darwini had greater individual variability than previously thought. Although based on the results of the morphologic and morphometric analysis, the idea of sexual dimorphism for M. darwini is, for the time being, unwarranted. This new record also supports the idea that Mylodon had great ecological tolerance and was capable of inhabiting climates ranging from cold and arid to warm and humid, and even montane environments.

A new genus for the Megatheriinae (Xenarthra, Tardigrada, Megatheriidae) from the Arroyo Chasicó Formation (Upper Miocene) of Buenos Aires Province, Argentina

Fil: Brandoni, Diego. Provincia de Entre Rios. Centro de Investigaciones Cientificas y Transferencia de Tecnologia a la Produccion. Universidad Autonoma de Entre Rios. Centro de Investigaciones Cientificas y Transferencia de Tecnologia a la Produccion. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Centro de Investigaciones Cientificas y Transferencia de Tecnologia a la Produccion; Argentina

“Xyophorus” sp. en El Mioceno Medio de Chubut: Implicancias Sistemáticas, Biogeográficas y Biocronológicas Del Registro de un Nothrotheriinae en el Neógeno de la Argentina

Abstract. “XYOPHORUS” SP. FROM THE MIDDLE MIOCENE OF CHUBUT PROVINCE: SYSTEMATIC, BIOGEOGRAPHIC, AND BIOCHRONOLOGIC IMPLICATIONS OF THE RECORD OF A NOTHROTHERIINAE FROM THE NEOGENE OF ARGENTINA. Xyophorus Ameghino was described based on mandibular fragments of Xyophorus rostratus Ameghino from the Early Miocene of Patagonia. The specimen herein described was collected in the locality “El Petiso”, located in northwestern Chubut Province, in sediments referred to the Middle Miocene and it is represented by a mandibular fragment that is characterized by: (1) posterior margin of the mandibular symphysis anterior to the plane of the caniniform; (2) posterolateral opening of mandibular canal on the lateral side of the coronoid process and nearly to the oclusal plane; (3) oclusal surface of the molariforms with two crests separated by a “V” valley; and (4) molariforms 1–2 presents vertical grooves on the labial and lingual sides, and molariform 3 with a groove on the labial one. The features present in this specimen and in the species herein referred to “Xyophorus” bondesioi Scillato-Yané, and “Xyophorus” villarroeli Saint-André allow distinguishing them from the species of the genus Xyophorus (e.g., X. andinus Ameghino, X. atlanticus Ameghino, X. crassissimus Ameghino) justifying the erection of a new genus and its inclusion in Nothrotheriinae. The record of “Xyophorus” sp. from the Middle Miocene of Chubut Province represents the oldest and australmost for Nothrotheriinae from Argentina, whereas, the record of “Xyophorus” cf. bondesioi from the locality of Cerdas, in Bolivia, would correspond to the oldest one for the subfamily.

Anisodontherium from the Late Miocene of North-Western Argentina

The fossil record of Megatheriinae (Tardigrada, Megatheriidae) in Argentina extends from the Colloncuran (Middle Miocene of Patagonia) to the Lujanian (Late Pleistocene—Early Holocene of the Pampean region). In the Late Miocene of north-western Argentina, Megatheriinae is represented by just three species belonging to a single genus, Pyramiodontherium. Here, we describe a partial mandible and the phalanges of a third digit of the manus recovered from the Saladillo Formation (Upper Miocene) of Tucumán Province, and assign them to Anisodontherium sp. Anisodontherium is primarily characterized by mesiodistally compressed molariforms, an anterior margin of the coronoid process located posterior to m4, and a posterior margin of the mandibular symphysis located anterior to m1. While these features can also be observed in A. halmyronomum from the Arroyo Chasicó Formation (Buenos Aires Province, Pampean region), Anisodontherium sp. is smaller and more slender than the former. The shape of each molariform of Anisodontherium affects the total length of the molariform tooth row, and thus the interpretation of some characters used in cladistic and paleobiological analyses. The material described here adds to the knowledge of the mandibular and dental anatomy of early megatheriines. In addition, the occurrence of Anisodotherium in Tucumán Province provides the first record of this genus outside the Pampean region, and increases the diversity of megatheriines during the Late Miocene—Pliocene of north-western Argentina.

On the Systematics of Ortotherium Ameghino (Xenarthra, Tardigrada, Megalonychidae) from the ‘Conglomerado Osífero’ (Late Miocene) of Argentina

Megalonychidae are a group of Xenarthra known from the Deseadan SALMA of Argentina (Carlini and Scillato-Yané, 2004) and Bolivia (Pujos and De Iuliis, 2007) to the present, represented by the extant sloth Choloepus Illiger (White and MacPhee, 2001; Gaudin, 2004; but see Carlini and ScillatoYané, 2004). Although the principal records of Megalonychidae are those from Central and North America (e.g., Matthew and Paula Couto, 1959; Hirschfeld and Webb, 1968; White and MacPhee, 2001), in South America, Megalonychidae are common in the ‘Conglomerado osı́fero’ (Ossiferous Conglomerate) or ‘Mesopotamiense’ within the Ituzaingó Formation, Entre Rı́os Province, Argentina (Paula Couto, 1979; Carlini et al., 2000; Cione et al., 2000). Several authors have studied the Megalonychidae from the ‘Conglomerado osı́fero’ (e.g., Ameghino, 1885, 1891; Kraglievich, 1922, 1923a, 1923b, 1923c, 1925, 1926; Bordas, 1942; ScillatoYané, 1980), but no systematic revision of the group has been performed beyond the original naming of species. Many of these fossil sloths have not been included in studies by other researchers due to the fragmentary nature of their remains. The most recent works on Megalonychidae from the ‘Conglomerado osı́fero’ are those by Carlini et al. (2000), Cione et al. (2000), and Brandoni (2008), which briefly commented on the different genera: Ortotherium Ameghino, 1885, Pliomorphus Ameghino, 1885, Menilaus Ameghino, 1891, Amphiocnus Kraglievich, 1922, Protomegalonyx Kraglievich, 1925, Megalonychops Kraglievich, 1926, and Paranabradys Scillato-Yané, 1980. Despite these contributions, the taxonomic status of several species from the Tertiary of Argentina that were first described and named in the late 19th century has not been addressed. The dentary specimen that forms the basis for this report, from the ‘Conglomerado osı́fero’ of Entre Rı́os Province, was briefly commented upon and illustrated by Brandoni (2008). The aim of this paper is to describe this specimen (here referred to Ortotherium), provide an emended diagnoses for the genus and species, and assess variation within the genus. For the purposes of this paper, I follow the systematic arrangement suggested by Gaudin (2004) (e.g., Eucholaeops Ameghino is considered a Megalonychidae). Institutional Abbreviations—MACN, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia,’ Buenos Aires, Argentina; MLP, Museo de La Plata, Facultad de Ciencias Naturales y Museo, La Plata, Argentina. Anatomical Abbreviations—c, caniniform; HRM, height of the mandibular ramus; m1–m3, molariforms 1–3; po, posterolateral opening of mandibular canal. Other Abbreviations—SALMA, South American Land Mammal Age.

AN ENIGMATIC NOTHROTHERIINAE (XENARTHRA, TARDIGRADA) FROM THE PLEISTOCENE OF ARGENTINA

The aim of this contribution is to describe two femora (MACN Pv 14148 and MACN Pv 14149 ) recovered from the Pleistocene of Santa Fe Province Argentina, provided a taxonomic assignation for them, and to discuss some taxonomic and biogeographical aspects of these finds. The general morphology of the femora more closely resembles the femur of Nothrotheriops (Xenarthra, Tardigrada, Nothrotheriidae) than any of the other known South American late Pleistocene nothrotheres. Although a bit larger, both specimens are also more similar in size to those of Nothrotheriops shastensis and share several features with this species. Based on their morphology the femora could be referred to Nothrotheriops, a genus exclusively recorded from the Pleistocene of North America, making this the first record of the genus outside of its known geographical distribution. However an alternative hypothesis is also plausible: the assignation of MACN Pv 14148 and MACN Pv 14149 to other Nothrotheriinae, i.e., Nothropus, which was recorded from the same beds of the femora but was determined on a mandibular fragment.