TREMADOCIAN TRILOBITES FROM DARK SHALE FACIES OF THE ALFARCITO MEMBER (SANTA ROSITA FORMATION), QUEBRADA DE MOYA, JUJUY, ARGENTINA. The Quebrada de Moya constitutes a distinctive locality of the Santa Rosita Formation (uppermost Furongian—lowermost Ordovician) in the Quebrada de Humahuaca (Sierra de Tilcara, Cordillera Oriental of Jujuy, Argentina). The trilobites Leptoplastides marianus (Hoek), Parabolinella sp., Hapalopleura acantha Malanca and Brandán, and Asaphellus sp. are described from the dark shale facies of the upper part of the Alfarcito Member. A grainstone interstratified in the mudstones contains a low-diversity conodont assemblage of the Cordylodus angulatus Zone (lower Tremadocian). The Ordovician age of the section is confirmed, in addition, by the record of the graptolite Rhabdinopora flabelliformis ssp. in a sandstone underlying the studied levels. The dark shales accumulated by suspension fall-out during periods of maximum flooding, in a reducing, distal offshore marine environment. The trilobite fauna is largely dominated by L. marianus. The upper part of the Alfarcito Member does not show dark facies in other sectors of the Sierra de Tilcara. The sedimentologic characters of the section described, the low diversity of the conodont assemblage, and the scarcity of agnostoid trilobites may be indicative of a partial isolation of the basin.

ICHNOLOGICAL AND PALEOENVIRONMENTAL ANALYSIS OF THE PUNTA SAN ANDRÉS ALLOFORMATION (PLIO-PLEISTOCENE), BUENOS AIRES PROVINCE, ARGENTINA. Late Cenozoic deposits that crop-out in the costal cliffs of Buenos Aires Province, have been the center of paleontological studies since the beginnings of the twentieth century. The presence of structures related to biological activity in these deposits has been pointed out by several authors. However, they have never been studied in a holistic way, taking into account all of the structures and not only those related to a single group. Amongst the diversity of trace fossils related to invertebrate activity, burrows are the most abundant and two different morphologies can be recognized: (1) unwalled meniscate burrows referred to Taenidium serpentinum, and (2) walled meniscate burrows interpreted as Beaconites coronus. Other trace fossils found in these paleosols are spherical chambers assigned to Castrichnus incolumis. Trace fossils of vertebrate activity are mostly caves. The largest ones are attributed to the activity of Pampatheriidae or Eutatini (Xenarthra, Cingulata) and the smallest ones to the activity of various types of Caviomorpha (Mammalia, Rodentia) including the families Echimyidae, Octodontidae, Cavidae and Chinchillidae. Trace fossils related to flora are root molds and rhizoconcretions. Ichnological analysis allowed some paleoclimatic inferences. The presence of chambers and burrows associated with earthworm activity suggests soils affected by seasonally dry periods. These observations confirm prior paleoclimatic interpretations based on micromorphological study of the paleosols and sedimentological work.

FOSSIL WOODS OF LEGUMINOSAE FROM THE ITUZAINGÓ FORMATION, ENTRE RÍOS, ARGENTINA: PALEOECOLOGICAL AND PALEOBIOGEOGRAPHIC IMPLICATIONS. The family Fabaceae is among the best represented in the fossil record of the Cenozoic of Argentina and in particular of the Ituzaingó Formation. This paper describes four types of permineralized by silicification woods related to this family, Menendoxylon vasallensis Lutz, Anadenantheroxylon villaurquicense Brea, Aceñolaza y Zucol emend., Prosopisinoxylon americanum sp. nov. and Gleditsioxylon paramorphoides sp. nov. Two new fossil species were recognized and the diagnosis of Anadenantheroxylon villaurquicense was amended. The specimens were found in the Ituzaingó Formation (Pliocene—Pleistocene), Entre Rios, Argentina, and have only preserved the anatomy of secondary xylem. Some anatomical features were related with the presence of a seasonal and dry climate. From paleogeographic and paleoecological features of distribution of most related extant genera, it is proposed that during the Pliocene—Pleistocene developed a heterogeneous environment characterized by having arboreal elements linked to Chaco, riparian and component of Seasonally Dry Tropical Forests (SDTF). The presence of the studied fossil wood in the Ituzaingó Formation (Pliocene—Pleistocene) in the Paraná Basin shows a rich flora linked to SDTF southermost of its current distribution, supporting the hypothesis that had a greater extent in South American continent during the late Cenozoic.

Three orders of South American extinct native ungulates are recorded from the Santa Cruz Formation along the Atlantic coast of Patagonia: Notoungulata (Adinotherium Ameghino, Nesodon Owen, Interatherium Ameghino, Protypotherium Ameghino, Hegetotherium Ameghino, and Pachyrukhos Ameghino), Litopterna (Theosodon Ameghino, Anisolophus Burmeister, Tetramerorhinus Ameghino, Diadiaphorus Ameghino, and Thoatheriurn Ameghino), and Astrapotheria (Astrapotherium Burmeister). An ecomorphological study based on geometric morphometries of the masticatory apparatus was performed. The reference sample included 618 extant specimens of the orders Artiodactyla, Perissodactyla, Hyracoidea, and Diprotodontia. Thirty six cranial and 27 mandibular three-dimensional landmarks were digitized. Allometric scaling, principal component analyses, and phylogenetic generalized estimating equations on the cranium and mandible were preformed. Analyses of cranial shape show strong phylogenetic constraints, whereas the mandibular analyses show a functional pattern related to habitat/ diet and hypsodonty. The extant brachydont ungulates from closed habitats show a more elongated and narrower mandibular symphysis with a lower mandibular corpus, than hypsodont, open habitat species. The latter have short symphyses with a high, curved mandibular corpus. This morphological pattern was also present among Santacrucian ungulates, allowing characterization of notoungulates mainly as open habitats dwellers, with some taxa foraging on grass (Protypotherium, Interatherium), and others on grass and leaves {Hegetotherium, Pachyrukhos, and Adinotheriurn), depending on the availability. Nesodon may have dwelled in mixed habitats and had a mixed feeding behavior, while small proterotheriids {Anisolophus and Thoatheriurn) may have fed predominantly on dicotyledonous plants. The remaining litopterns {Tetramerorhinus, Diadiaphorus, and Theosodon) and Astrapotherium may have foraged in closed habitats and fed on dicotyledonous plants.

FIRST RECORD OF COXOFEMORAL DYSPLASIA IN A LATE TRIASSIC RYNCHOSAUR. Paleopathology deals with diseases that have left evidence in the fossil record. This field includes the identification of the pathology, and its consequences that on the animal that suffered it. We present the first record of a coxofemoral dysplasia in an Upper Triassic rhynchosaur, being also the first identification of this pathology in the fossil record. The specimen is an incomplete skeleton, partially articulated, of Hyperodapedon sanjuanensis (Sill), from the Ischigualasto Formation (Carnian—Norian). Rhynchosaurs were herbivores with a widespread geographical distribution, low species diversity and a stratigraphic range restricted to Triassic outcrops. The abnormalities described consist of atrophy of the sacrum and pelvis, sclerosed structures in some dorsal vertebrae, and deformation of the left femur. These features are presently characteristic of acetabular dysplasia in dogs. Acetabular dysplasia is a multifactorial disease appearing in the earliest stages of development and increasing throughout life, triggering a secondary joint osteoarthritis in the adult animal and leading to total disability of the affected limb. The advanced stage of the disease affecting the studied specimen reveals a pace known as “fourth grade claudication”, stage in which the affected limb stops supporting the body-weight, moving the center of gravity and loading the body-weight onto the other legs. Finally, the adult stage reached by the specimen —despite the severity of their condition— may suggest complex survival strategies in Hyperodapedon sanjuanensis, which need confirmation by future analyses.

A new fossil conifer wood —Brachyoxylon currumilii sp. nov.— is described from the Lower—Middle Jurassic of Chubut Province (Argentina). The specimens were collected at a locality where the Cañadón Asfalto Formation is exposed, in the vicinity of the Cerro Cóndor village. The studied wood is characterized by mixed pitting in radial tracheid walls (predominantly uniseriate), araucarioid cross fields, low uniseriate rays and the absence of resin canals. The use of transmitted light and epifluorescence microscopy together with SEM imaging allowed the identification of additional characters such as the presence of pitting with torus-margo and compression wood. These characters are discussed in terms of their systematic relevance. On these grounds, the systematic affinity of the studied wood is discussed and linked to the extinct conifer family Cheirolepidiaceae, one of the dominant plant groups during the Jurassic and Cretaceous in Patagonia.