Ana Maria Ribeiro

A Primitive Late Triassic ‘ictidosaur’ from Rio Grande Do Sul, Brazil

A primitive ‘ictidosaur’ from lower Norian beds of southern Brazil, Riograndia guaibensis gen. et sp. nov., represented by a fragmentary skull and a lower jaw bearing a complete dentition, shows a more generalized morphology than Chaliminia from the Upper Triassic of Argentina and PachygenelusDiarthrognathus from the Lower Jurassic of South Africa, Canada and Greenland. The frontal bone borders the orbit, and ventrally contacts the dorsal process of the palatine. The secondary bony palate extends back to the last postcanine. I1 and i2 are reduced, whereas I2-3 and i1 are hypertrophied. Both PC 1–7 and pc 1–7 have blade-like crowns without cingula and with 5–9 small sharp cuspules. The upper postcanine crowns are semicircular in labial view with the cuspules around their margins. The lower postcanine crowns are asymmetrical with most of the cuspules dorsodistally distributed. The possible origin of this peculiar dentition is interpreted as the retention of the juvenile dentition of ancestors. The hypothesis that Riograndia guaibensis and the so-called ‘ictidosaurs’ might have been derived from gomphodont cynodonts is presented.

New Tapirus species (Mammalia: Perissodactyla: Tapiridae) from the upper Pleistocene of Amazonia, Brazil

Abstract A new species of Tapirus (Perissodactyla: Tapiridae) is described from the upper Pleistocene of the Rio Madeira Formation in Araras, Nova Mamoré Municipality, Rondonia State, Brazil. Tapirus rondoniensis sp. nov. is represented by a nearly complete skull with a unique combination of characters that differ from those of extant and fossil species of Tapirus described from South America. It is diagnosed mainly by its broad frontals that bear a pneumatization extending to the frontoparietal suture, a high sagittal crest, a weakly molarized P2 lacking a protoloph, and a metaloph that merely reaches the base of the ectoloph. T. rondoniensis sp. nov. is similar in some respects to T. terrestris, but it retains some primitive dental and cranial character states in common with T. pinchaque, such as broad frontals and a weakly molarized P2.

The African cynodont Aleodon (Cynodontia, Probainognathia) in the Triassic of southern Brazil and its biostratigraphic significance

In this contribution we report the first occurrence of the enigmatic African probainognathian genus Aleodon in the Middle-early Late Triassic of several localities from the state of Rio Grande do Sul in southern Brazil. Aleodon is unusual among early probainognathians in having transversely-expanded postcanine teeth, similar to those of gomphodont cynognathians. This genus was previously known from the Manda Beds of Tanzania and the upper Omingonde Formation of Namibia. The Brazilian record of this genus is based upon multiple specimens representing different ontogenetic stages, including three that were previously referred to the sectorial-toothed probainognathian Chiniquodon theotonicus. We propose a new species of Aleodon (A. cromptoni sp. nov.) based on the specimens from Brazil. Additionally, we tentatively refer one specimen from the upper Omingonde Formation of Namibia to this new taxon, strengthening biostratigraphic correlations between these strata. Inclusion of A. cromptoni in a phylogenetic analysis of eucynodonts recovers it as the sister-taxon of A. brachyrhamphus within the family Chiniquodontidae. The discovery of numerous specimens of Aleodon among the supposedly monospecific Chiniquodon samples of Brazil raises concerns about chiniquodontid alpha taxonomy, particularly given the extremely broad geographic distribution of Chiniquodon. The discovery of Brazilian Aleodon and new records of the traversodontid Luangwa supports the hypothesis that at least two subzones can be recognized in the Dinodontosaurus Assemblage Zone.

Redescription of Dasypus punctatus Lund, 1840 and Considerations on the Genus Propraopus Ameghino, 1881 (Xenarthra, Cingulata)

ABSTRACT The comparative description of the most complete specimen of Dasypus punctatus (Xenarthra, Cingulata), from southeastern Brazil, reveals that the species differs from other Dasypodini by the numerous foramina it has in both buckler and movable osteoderms, providing the basis for the lectotype designation. This species was historically allocated to Propraopus, but the inclusiveness and monophyly of that genus are uncertain. A new phylogenetic analysis groups D. punctatus with the living species of Dasypus in a monophyletic clade for the genus, also supporting a Propraopus clade composed of P. sulcatus and the type species P. grandis. The palatal anatomy corroborates previously suggested affinities between D. kappleri and D. punctatus. On the contrary, the possible synonymy between P. grandis and P. sulcatus needs further investigation, given that they differed on a single character. As usual in cingulate systematics, characters related to osteoderm ornamentation proved essential to determine the relationships of taxa. However, their use requires careful sampling in order to account for intraspecific variation biases.

Late Miocene Potamarchine Rodents from Southwestern Amazonia, Brazil—with Description of New Taxa

The fossil rodents from the southwestern Amazonia of Brazil have been studied since the first half of the 20th century. Several caviomorph rodents were reported for the Neogene of this region, mainly neoepiblemids and dinomyids. Until recently, the record of dinomyids in the Solimões Formation (Late Miocene) was predominantly based on a few isolated teeth, which made it difficult to make more accurate taxonomic identifications due to the scarcity of diagnostic characters. Here, new remains, more complete than those previously reported, of potamarchine dinomyids from the Neogene of Brazil are described. A new species of Potamarchus and a new genus and species of a Potamarchinae are erected. In addition, new material of Potamarchus murinus and Potamarchus sp. is identified. These data suggest a higher diversity of dinomyids in in the western Amazonia than previously supposed.

The first record of Galea Meyen, 1832 (Rodentia, Hystricognathi, Caviidae) in the late Pleistocene of southern Brazil and its palaeobiogeographic implications

The first caviine rodent referable to Galea Meyen, 1832 is described from the late Pleistocene of southern Brazil based on a left dentary with the p4–m3 series. The specimen derives from the Ponte Velha I locality in the Touro Passo Creek (Touro Passo Formation, upper Pleistocene), western Rio Grande do Sul State. The main characters used to assign this specimen to Galea are: anterior area of horizontal crest at the level of prism I of p4; deep anterior area of masseteric fossa; incisor alveolus on the medial face of the dentary extended up to the level of prism II of m2; and presence of cement in the hypoflexid. Currently, the genus has a disjunct distribution, with a group in Argentina, Bolivia and Peru, and another in northern and northeastern Brazil. The presence of this taxon in Pleistocene deposits of Rio Grande do Sul State, Uruguay and the Argentine Mesopotamian, where there are no extant representatives of the genus, indicates its wider distribution during the late Pleistocene.

The sea-level highstand correlated to marine isotope stage (MIS) 7 in the coastal plain of the state of Rio Grande do Sul, Brazil.

The coastal plain of the state of Rio Grande do Sul, in southern Brazil, includes four barrier-lagoon depositional systems formed by successive Quaternary sea-level highstands that were correlated to marine isotope stages (MIS) 11, 9, 5 and 1, despite the scarcity of absolute ages. This study describes a sea-level highstand older than MIS 5, based on the stratigraphy, ages and fossils of the shallow marine facies found in coastal barrier (Barrier II). This facies outcrops along the banks of Chuí Creek, it is composed of fine, well-sorted quartz sand and contains ichnofossils Ophiomorpha nodosa and Rosselia sp., and molluscan shells. The sedimentary record indicates coastal aggradation followed by sea-level fall and progradation of the coastline. Thermoluminescence (TL) and electron spin resonance (ESR) ages from sediments and fossil shells point to an age of ∼220 ka for the end of this marine transgression, thus correlating it to MIS 7 (substage 7e). Altimetric data point to a maximum amplitude of about 10 meters above present-day mean sea-level, but tectonic processes may be involved. Paleoceanographic conditions at the time of the highstand and correlations with other deposits in the Brazilian coasts are also discussed.

Cranial and dental studies of Glossotherium robustum (Owen, 1842) (Xenarthra: Pilosa: Mylodontidae) from the Pleistocene of southern Brazil

Pitana, V.G., Esteban, G.I., Ribeiro, A.M. & Cartelle, C. 2013. Cranial and dental studies of Glossotherium robustum (Owen, 1842) (Xenarthra: Pilosa: Mylodontidae) from the Pleistocene of southern Brazil. Alcheringa, 1–16. ISSN 0311-5518. Mylodontine ground sloths were studied from several Pleistocene localities of Rio Grande do Sul State: São Gabriel (central region), Quaraí, Uruguaiana and Alegrete (western region) and Santa Vitória do Palmar (coastal region) municipalities. The cranial and mandibular material is assigned to Glossotherium robustum based on the enlargement of the anterior portion of the maxilla, a rounded and ventrolaterally arched fossa for the estylohyal, an elliptical occipital condyle, a spatulate symphyseal region of the mandible, together with the size and degree of lobulation of the teeth. Comparison with specimens from the Pampean region of Argentina, western Uruguay and northeastern Brazil revealed that the Rio Grande do Sul material is most similar morphologically to that of the Pampean region of Argentina and Uruguay. These southern specimens are morphologically distinct from Pleistocene material from tropical Brazil assigned to Glossotherium sp. The Pleistocene records of G. robustum indicate that this taxon was widely distributed between 20°S and 40°S spanning Argentina, Brazil, Bolivia, Chile, Uruguay and Paraguay, whereas Glossotherium sp. was restricted to latitudes <30°S.

Capybaras (Rodentia: Hystricognathi: Hydrochoeridae) from the late Pleistocene of southern Brazil

The Hydrochoeridae are caviomorph rodents of medium to large size. They are euhypso- dont and elasmodont, with a peramorphic trend to increase the number of M3 prisms from basal to advanced taxa. The diversity of this family was higher during the Miocene/Pliocene, but today they are represented by a single genus, with two species, Hydrochoerus hydrochaeris (Linnaeus, 1766) and H. isthmius GoLdman, 1912. In this paper we described fossil remains assigned to H. hydro- chaeris from Touro Passo Creek (Touro Passo Formation, upper Pleistocene, Lujanian Age) in west- ern Rio Grande do Sul State, southern Brazil. The main charac ters used to assign these specimens to H. hydrochaeris are: M3 with 13 free prisms, upper diastema shorter than the maxillary cheek teeth, rostral area relatively wide, smaller proportion s than Neochoerus Hay, 1926 and larger than H. isthmius. The presence of H. hydrochaeris suggests that in late Pleistocene of western Rio Grande do Sul State, probably existed environments with permanent water bo dies.

Chiroptera (Mammalia) from the Holocene of Rio Grande do Sul State, Brazil

The Chiroptera do not have an extensive fossil record. To date, for the Quaternary of Brazil, only material from Minas Gerais, São Paulo, Bahia and Goiás States are known. For Rio Grande do Sul State, in contrast to the studies about the Pleistocene megafauna, little is known about Holocene small mammals, this being the first contribution about the Chiroptera of this age found in Rio Grande do Sul. The material was excavated from two archaeological sites, dating from ± 9,400 yrs BP to ± 4,250 yrs BP. The taxa recorded were: Chrotopterus auritus, Pygoderma bilabiatum (Phyllostomidae); Eptesicus brasiliensis, E. fuscus, Myotis cf. Myotis ruber, Vespertilionidae aff. Lasiurus (Vespertilionidae); Tadarida brasiliensis, and Molossus molossus (Molossidae). The presence of E. fuscus extends its Holocene distribution far southwards into the south temperate zone; its previous Quaternary occurrences were in Bahia State, Brazil, as well as in Venezuela, Mexico and the USA.