ICHNOLOGY OF THE RÍO MAYER FORMATION, LOWER CRETACEOUS, SOUTHWESTERN GONDWANA, PATAGONIA, ARGENTINA. The Río Mayer Formation was deposited during the Early Cretaceous in the Austral Basin (Santa Cruz Province, Argentina) and includes black shales with intercalated sandstones and marls. Abundant information is available on its palaeontological content, especially on ammonoids, but detailed ichnological studies are lacking. Sedimentological and ichnological data were collected in the Río Guanaco area (49°57′11″S—72°04′56″W). Three sections were identified and described in detail. The lower Section was deposited during the Berriasian—Valanginian and is composed of black shales. The middle section including black marls with intercalated black shales was deposited during the Valanginian—Hauterivian. The upper section is composed of black shales with frequent thin intercalations of finegrained sandstones (Barremian—Albian). Six ichnogenera were identified: Zoophycos, Chondrites, Bergaueria, Ophiomorpha, Palaeophycus and Teredolites. The most abundant and constant is Zoophycos, arranged in three morphological groups. All these ichnogenera are grouped —in the Río Mayer Formation— into two ichnoassociations. The first is found in the middle section, and is a typical Zoophycos ichnofacies with associated Bergaueria. The second ichnoassociation appears at the top of the upper section, and contains a Zoophycos ichnofacies with associated Ophiomorpha and Teredolites. The unusual presence of Bergaueria in low oxygen offshore environments, exceeds the bathymetric range typical of this ichnogenus. The unusual presence of O. cf. rudis in outer shelf environments reveals the existence of doomed pioneers in the analyzed unit.

REEVALUATION OF TETRAGRAPTUS PHYLLOGRAPTOIDES AND T. AKZHARENSIS BIOZONES (LOWER ORDO-VICIAN, FLOIAN) FROM THE CORDILLERA ORIENTAL ARGENTINA. This paper presents new accuracies and correlations of the Lower Ordovician (Floian) biostratigraphic scheme of the Cordillera Oriental. The Tetragraptus phyllograptoides and T. akzharensis biozones are reevaluated based on graptolite records from the lower levels of the Acoite Formation, outcropping in the Quebrada de Quinilicán (Sierra de Aguilar). The stratigraphic range of the characteristic taxa is discussed and compared with that observed in Los Colorados area. In the Tetragraptus phyllograptoides Biozone, it is worth mentioning the presence of Tetragraptus approximatus (Nicholson), Tetragraptus sp., Baltograptus geometricus (Törnquist), Cymatograptus demissus (Törnquist) and C. rigoletto (Maletz, Rushton and Lindholm) in addition to the index species. Tetragraptus amii (Elles y Wood), Cymatograptus protobalticus (Monsen), C. balticus (Tullberg) and Paradelograptus sp. appear in the lower part of the T. akzharensis Biozone, whereas Baltograptus vacillans (Tullberg), Corymbograptus v-fractus tullbergi (Monsen), Trichograptus dilaceratus (Herrmann), Expansograptus latus (Hall), E. holmi (Törnquist), E. constrictus (Hall), Acrograptus gracilis (Törnquist), and A. filiformis (Tullberg) are recorded in the upper portion of the same biozone. The regional correlation of both biozones is corroborated on the western margin of the Cordillera Oriental. The possible subdivision of the T. akzharensis Biozone is commented, according to the biostratigraphic scheme recently proposed for Scandinavia, and a more accurate intercontinental correlation of Northwestern Argentina Floian levels is proposed. In addition, the paleoecological implications of some studied taxa and the paleobiogeographical relationships between Northwestern Argentina and other Gondwanan regions are discussed, and the strong affinity with Baltoscandinavia during the Lower Ordovician is validated.

NEW SPECIES OF GIANT TORTOISE OF THE GENUS CHELONOIDIS FITZINGER, 1835 (CRYPTODIRA: TESTUDINIDAE), FROM THE LOWER MEMBER OF THE TOROPÍ/ YUPOÍ FORMATION (LATE PLEISTOCENE/ LUJANIAN), BELLA VISTA, CORRIENTES, ARGENTINA. A new species of giant tortoise from the upper section of the lower member of Toropí/ Yupoí Formation (late Pleistocene, 58–22 ka) is described. The holotype of this new species was recovered at Arroyo Toropí (10 km south from Bella Vista city, Corrientes Province, Argentina). The presence of pectoral scales in the plastron narrower in midline and antero-posteriorly expanded towards the marginal scutes, allow us to assign this tortoise to the genus Chelonoidis Fitzinger. The non parallel lateral margins, the peripheral bones lobed in the bridge, the elliptical depression on both sides of peripheral bones III, and a sub- rhomboidal entoplastron proximally broadening, with distal projections covering the pectoral scales, allow us to recognize a new species, Chelonoidis lutzae sp. nov. The strict consensus tree of the phylogenetic analysis of Chelonoidis shows a polytomy among Ch. lutzae sp. nov., ?Ch. gallardoi (Rovereto), ?Ch. australis (Moreno), and the extant and extinct species assigned to carbonaria and chilensis groups. The carbonaria group includes Ch. denticulata (Linnaeus) and another clade formed by Ch. carbonaria (Spix) and Ch. hesterna (Auffenberg). The chilensis group, includes two subclades, one composed by Ch. chilensis (Gray), Ch. petersi (Freiberg) and Ch. nigra (Quoy and Gaimard), and another formed by YPFBPAL 0932 and Ch. gringorum (Simpson). Using the “pruned tree” option of TNT an “extinct giant continental tortoise” clade (Ch. lutzae sp. nov. and ?Ch. australis) is recovered, clearly differentiated from the giant Galápagos tortoises.

A GUIDELINE FOR THE IDENTIFICATION OF SUBFOSSIL TANYTARSINI (DIPTERA: CHIRONOMIDAE: CHIRONOMINAE) FROM PATAGONIA. This paper presents a key for the identification of nine subfossil morphotypes of the Tribe Tanytarsini (Subfamily Chironominae), described for Argentinean and Chilean Patagonia, from 39° to 54°S. The key is structured based on the head capsules, which is the only material preserved in the sedimentary record. Tribe Tanytarsini is of particular importance as it includes species with high environmental importance, especially climatic. The material collected in Argentinean and Chilean Patagonia allowed the classification of nine morphotypes, distinguished mainly by four easily observables characteristics; (1) the spur shape of the antennal pedestal, (2) presence and shape of post-occipital plate, (3) number of premandible teeth, and (4) mentum and ventromental plates. The main goal of this contribution is to bring together the very sparse and limited knowledge on Tanytarsini from southern South America, in a simple and practical key helping the identification and separation of morphotypes, especially useful for scientists working with fossil chironomids from the Quaternary of Patagonia and other regions of the Southern Hemisphere.

THE TURTLES FROM THE UPPER VALLESIAN OF CERRO DE LOS BATALLONES (MADRID, SPAIN): NEW DATA ON THE POORLY KNOWN GENUS PALEOTESTUDO. The Vallesian fossil sites of Cerro de los Batallones (Madrid, Spain) are relevant in the European record both because of the diversity recorded and the preservation of its fossils. Although the most abundant record of these sites corresponds to mammals, especially carnivores, other vertebrates have also been identified. Turtles are the best represented lineage of reptiles, but this group has not been studied. The analysis of the currently available material allows the identification of three taxa. One of them corresponds likely to a freshwater testudinid, that could belong to a member of the “Palaeochelys sensu lato-Mauremys” group. The other two are attributed to terrestrial testudinids, being the largest compatible with the Spanish Miocene specimens assigned to Cheirogaster. The other, represented by several well-preserved shells, is identified as a member of Paleotestudo. The presence of Paleotestudo had not been, so far, confirmed in the Iberian Peninsula. The review of the Spanish record allows us identifying this genus in all the Aragonian and Vallesian biozones. The validity of several Iberian taxa is refuted, and both the stratigraphie and paleobiogeographic distributions of this genus are extended.

SYSTEMATICS AND PHYLOGENY OF THE GENUS AMEGHINOMYA IHERING, 1907 (BIVALVIA: CHIONINAE) FROM THE CENOZOIC OF ARGENTINA AND CHILE. A systematic revision of the genus Ameghinomya Ihering, 1907 is conducted and its phylogenetic relationships are explored through a cladistic analysis based on morphological characters of extant and fossil species. The resulting strict consensus shows one clade consisting of Protothaca Dall and Austrovenus Finlay and another one encompassing the species of Ameghinomya, the latter being monophyletic. Ornamentation of the valves is shown to have systematic value which until now had not been appropriately explored. Based on the results of the phylogenetic and systematic analysis, it is proposed to assign the species Venus antiqua King, 1832 (extant, Southwestern Atlantic) and Venus chiloensis Philippi, 1887 (Miocene, Chile) to the genus Ameghinomya. Ameghinomya camachoi sp. nov. is described from the Carmen Silva Formation (Miocene, Isla Grande de Tierra del Fuego, Argentina).