Jorge I. Noriega

Definitive fossil evidence for the extant avian radiation in the Cretaceous

Long-standing controversy surrounds the question of whether living bird lineages emerged after non-avian dinosaur extinction at the Cretaceous/Tertiary (K/T) boundary or whether these lineages coexisted with other dinosaurs and passed through this mass extinction event. Inferences from biogeography and molecular sequence data (but see ref. 10) project major avian lineages deep into the Cretaceous period, implying their ‘mass survival’ at the K/T boundary. By contrast, it has been argued that the fossil record refutes this hypothesis, placing a ‘big bang’ of avian radiation only after the end of the Cretaceous. However, other fossil data—fragmentary bones referred to extant bird lineages—have been considered inconclusive. These data have never been subjected to phylogenetic analysis. Here we identify a rare, partial skeleton from the Maastrichtian of Antarctica as the first Cretaceous fossil definitively placed within the extant bird radiation. Several phylogenetic analyses supported by independent histological data indicate that a new species, Vegavis iaai, is a part of Anseriformes (waterfowl) and is most closely related to Anatidae, which includes true ducks. A minimum of five divergences within Aves before the K/T boundary are inferred from the placement of Vegavis; at least duck, chicken and ratite bird relatives were coextant with non-avian dinosaurs.

A NEW UPPER PLEISTOCENE TAPIR FROM ARGENTINA: REMARKS ON THE PHYLOGENETICS AND DIVERSIFICATION OF NEOTROPICAL TAPIRIDAE

Abstract A complete skull of a fossil tapir (Perissodactyla: Tapiridae) was recovered from outcrops of the Arroyo Feliciano Formation (Late Pleistocene; Lujanian Age) in the Argentine Mesopotamia and is here recognized as a new species. The phylogenetic relationships of this new taxon, Tapirus mesopotamicus sp. nov., are revealed by cladistic character analysis using several extinct and extant taxa. The taxa included in the analysis are the extinct genera Miotapirus, Paratapirus, and Plesiotapirus, five North American paleospecies Tapirus veroensis, T. haysii, T. johnsoni, T. webbi, and T. polkensis, and all the living species of the genus Tapirus (T terrestris, T. pinchaque, T. bairdii, and T. indicus). Tapirus mesopotamicus sp. nov is diagnosed by having a robust and long skull with short rostrum relative to total length of cranium, a single and not arched sagittal crest, broad table of frontals on the anterior skull roof, temporal crests converging very near the frontal-parietal suture, palate very arched, premaxilla deeply notched above canine, maxilla and base of zygomatic process strikingly robust, P1 short and quadrangular, and mandibular condyle slender with posterior wall flat or somewhat concave. The resulting cladogram depicts a well-supported clade comprising the South American tapirs. The new taxon T. mesopotamicus sp. nov. groups with its sister taxon T. pinchaque, and together with T. terrestris, form a sister clade to T. bairdii and three North American fossil tapirs.

First Record and a New Species of Seriema (Aves: Ralliformes: Cariamidae) from Santacrucian (Early-Middle Miocene) Beds of Patagonia

Living seriemas (Ralliformes, Cariamidae) are long-legged cursorial birds that comprise only two very closely related, and perhaps congeneric, species (Gonzaga, 1996): Cariama cristata and Chunga burmeisteri. They are endemic to South America and may represent surviving Neotropical relicts of an early ralli form radiation within the suborder Cariamae. Phorusrhacids, idiornithids, and bathornithids are also extinct components of ralliforms, a large terrestrial stock of predator or scavenger birds, which were abundant during the Tertiary of South and North America, and Europe (Mourer Chauvire, 1981, 1983; Alvarenga and H?fling, 2003). The phylogenetic relation ships and paleobiogeographic history of phorusrhacids, idior nithids, and bathornithids are still far from being resolved. Tertiary fossils of the cariamid subtaxon Cariaminae are scarce and restricted to the questionable record of Riacama caliginea Ameghino 1899 from the late Oligocene (Deseadan age) of Santa Cruz Province (see Brodkorb, 1967; Tonni, 1980; Tambussi and Noriega, 1996; Agnolin, 2004), and the early-middle Pliocene (Montehermosan age) record of Chunga incerta Tonni (1974) from Buenos Aires Province, both in Argentina. In this contribution we present new remains of seriemas re covered in 2005 by a joint expedition of the Museo de La Plata, Argentina, and Duke University, USA. They come from the middle levels of the Santa Cruz Formation (Upper-middle Mio cene) along the Atlantic coast of southernmost continental Pata gonia, Argentina, between the Coyle and Gallegos rivers. These localities are situated at about 52 degrees South latitude, about 100 km north to the Magallanes Strait (Fig. 1). In the mentioned area, the Santa Cruz Formation bears a terrestrial vertebrate fauna exceptional in its richness with over 70 species recorded in about 30 fossiliferous levels (Tauber, 1997a, Tauber 1997b; Tauber et al., 2004) that represents the richest assemblage of pre-Pleistocene mammalian skulls and ar ticulated skeletons known in the continent (Hatcher, 1903). A description of the localities and horizons that produced the fossils reported here is provided in the following section. Although still far fewer than mammals, these localities have provided quite a number of bird remains. Many of them were described and beautifully figured in the extensive Reports of the Princeton University Expeditions to Patagonia (Sinclair and Farr, 1932). They include Phorusrhacos longissimus Ameghino 1887, Brontornis burmeisteri Moreno and Mercerat 1891, Patagornis marshi Moreno and Mercerat 1891, Psilopterus bachmanni (Moreno and Mercerat 1891), and Psilopterus lemoinei (Moreno and Mercerat 1891), among the Phorusrhacids. Other bird taxa recorded at the Santa Cruz Formation include Tinamidae (Chiappe, 1991), Rheidae (Opisthodactylus patagonicus Ame ghino 1891), Pelecanidae (Liptornis hesternus Ameghino 1895), Plataleidae (Protibis cnemialis Ameghino 1891), Anatidae (Eone ornis australis Ameghino 1895; Eutelornis patagonicus Ameghino 1895), Aramidae (Anisolornis excavatus Ameghino 1891), and Falconiformes (Badiostes patagonicus Ameghino 1895; Thegornis debilis Ameghino 1895 and T. musculosus Ameghino 1899). Most of these taxa were erected on the basis of very fragmentary and eroded specimens, together with brief and poorly illustrated descriptions, that make difficult to assess their validity (Olson, 1981, 1985; Tonni, 1980; Tambussi and Noriega, 1996). Some of them have been recently revised (Alvarenga and H?fling, 2003; Agnolin, 2004, 2006, 2007).

THE FIRST PLIOCENE MAMMALS FROM THE NORTHEAST (MESOPOTAMIA) OF ARGENTINA: BIOSTRATIGRAPHIC AND PALEOENVIRONMENTAL SIGNIFICANCE

Abstract The record of Neogene faunas from the northeast of Argentina (Mesopotamia) is sporadic, whereas the late Miocene vertebrate-bearing horizons in this area contain a very abundant and diverse fauna, the Pliocene deposits are poorly known and have been unfossiliferous until now. This situation makes the understanding of the biogeographic and evolutionary history of the Mesopotamian taxa difficult. In this contribution, the first mammals are described that were recovered from the most basal levels of the Punta Gorda Group ( = Alvear Formation) at Entre Ríos Province, assigned to the late Pliocene (Lower Matuyama) by previous paleomagnetic studies. These beds are paleomagnetically bracketed between 1.95 and 2.6 Ma (late Pliocene) in the Alvear section and help to refine the biostratigraphy of these species elsewhere in northeastern Argentina. The echimyids Paramyocastor diligens (Ameghino, 1888) and Eumysops sp., and the hegetotheriid Paedotherium cf. typicum herein reported support a Pliocene age for the sediments from which they were recovered. These mammals suggest a paleoenvironment characterized by semiarid and open lowlands, markedly different than that inferred for the Late Miocene in this area.

Late Cenozoic birds of Buenos Aires province (Argentina): an attempt to document quantitative faunal changes

Abstract An analysis of quantitative evolution of the late Cenozoic bird communities of Buenos Aires Province (Argentina) indicates that there is a general tendency for taxonomic diversity to increase from the Huayquerian to the Montehermosan, to peak in the Chapadmalalan, to decrease in the Uquian, and to increase steadily from the Ensenadan to the Recent. It can be inferred from the results of faunal turnover that the present compositional patterns at the familial and generic levels were already established by the Montehermosan and post-Chapadmalalan times respectively. Likewise, extant species of birds are post-Ensenadan in origin. The high diversity parameters calculated from the Montehermosan may be related to stability of environmental-clinic conditions. The abrupt impoverishment in taxonomic diversity during the Chapdmalalan and the Uquian is probably correlated with an important global climatic change during the late Pliocene.

Phylogeny and Taxonomy of the Patagonian Miocene Falcon Thegornis musculosus Ameghino, 1895 (Aves: Falconidae)

Abstract The fossil record of the family Falconidae is poor and fragmentary. Extinct representatives from South America include the late early Miocene (Santacrucian) Thegornis musculosus and Thegornis debilis. Both species were originally described as Falconidae and afterwards moved to Accipitridae Circinae or Buteoninae. The analysis of a very well preserved and complete specimen of T. musculosus with similar stratigraphic and geographic provenances of the type material (lower levels of Santa Cruz Formation, coast of Patagonia, Argentina) corroborates the validity of the genus and its falconid affinities. The skull and postcranial morphology exhibit strong resemblances with the open-savannah inhabiting Herpetotheres and the forest-dwelling Micrastur (Herpetotherinae) but differ substantially from Falconinae (Falconini plus Caracarini). Detailed comparisons with a broad arrange of falconiform taxa in a cladistic framework, confirm its phylogenetic placement within the Herpetotherinae and sister to H. cachinnans. The ecotonal margins produced by the vanishing of humid forests that developed during changes in Patagonian plant communities throughout early Neogene times are hypothesized as a plausible scenario to understand the evolution of this basal clade of falcons.

First record of an extinct marabou stork in the Neogene of South America

We describe a new large species of marabou stork, Leptoptilus patagonicus (Ciconiiformes, Ciconiidae, Leptoptilini), from the late Miocene Puerto Madryn Formation, Chubut Province, Argentina. The specimen consists mainly of wing and leg bones, pelvis, sternum, cervical vertebrae, and a few fragments of the skull. We provisionally adopt the traditional systematic scheme of ciconiid tribes. The specimen is referred to the Leptoptilini on the basis of similarities in morphology and intramembral proportions with the extant genera Ephippiorhynchus, Jabiru, and Leptoptilos. The fossil specimen resembles in overall morphology and size the species of Leptoptilos, but also exhibits several exclusive characters of the sternum, humerus, carpometacarpus, tibiotarsus, and pelvis. Additionally, its wing proportions differ from those of any living taxon, providing support to erect a new species. This is the first record of the tribe Leptoptilini in the Tertiary of South America.

The Tropical Tortoise Chelonoidis denticulata (Testudines: Testudinidae) from the Late Pleistocene of Argentina and Its Paleoclimatological Implications

Fil: Manzano, Adriana Silvina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Universidad Autonoma de Entre Rios; Argentina

FOSSIL DUGONGIDAE (MAMMALIA, SIRENIA) FROM THE PARANÁ FORMATION (LATE MIOCENE) OF ENTRE RÍOS PROVINCE, ARGENTINA

Abstract. Fossil sirenians are well known from the Western Atlantic and Caribbean (WAC) region. Neogene records from the Atlantic coast of South America, although scarce, seem to reflect a similar taxonomic composition to its northern contemporaries. Fossil sirenians from Argentina are known from the late Miocene Paraná and Ituzaingó formations in Entre Ríos Province. An upper third molar housed in the Museo de Paleontología de la Universidad Nacional de Córdoba (CORD-PZ 4301), from the Paraná Formation, was originally described and assigned to the dugongid genus Metaxytherium Christol. Subsequent workers suggested it could instead belong to the dugongid genus Dioplotherium Cope, a designation that we confirm upon examination of the material. Additionally, we describe new sirenian remains from the Paraná Formation, consisting of two incomplete maxillae with teeth, belonging to one individual, deposited at the Museo de Ciencias Naturales de Paraná (MASP 373). This specimen shows similarities with species of Metaxytherium from the northern WAC. The Paraná Formation sirenians represent the southernmost occurrences of these two genera, and the geologically youngest occurrence of dugongids in the southern WAC. Dioplotherium and Metaxytherium also occur in the early Miocene of northern Brazil. The presence of these taxa as far south as Entre Ríos latitude suggests two possible dispersal routes: (1) across a marginal connection between a southern arm of the Amazonian Sea and the “Paranense Sea”; (2) along the Brazilian coast. Lastly, the occurrence of dugongids, which feed mainly on seagrasses, indicates that these marine angiosperms were present in the region as well.

Morphology of the forelimb of Psilopterus bachmanni (Aves, Cariamiformes) (Early Miocene of Patagonia)

Psilopterines are the smallest and most gracile predatory birds belonging to the large terrestrial Phorusrhacidae, which were abundant during the South American Tertiary. Two taxa are recognized from the Santacrucian (late Early Miocene) beds of Argentinian Patagonia: Psilopterus lemoinei and Psilopterus bachmanni. Although the first species was recently redescribed and is well known, in the case of P. bachmanni, the smaller of the two, the forelimb skeleton was virtually unknown until recently. The fossils described herein come from the coast of Santa Cruz Province, and were recovered from the middle levels of the Estancia La Costa Member, Santa Cruz Formation. The specimen includes associated bones of both forelimbs and a fragmentary furcula. The manus of this species, previously unknown, is described here for the first time: the os carpi ulnare and radiale are very stout bones, the carpometacarpus has processi extensorius and alularis very marked and stout and the os metacarpale majus and phalanges digiti majoris are very robust, and the phalanx digiti minoris is flattened. It has been proposed that some species belonging to Psilopterus were able to fly in a clumsy manner. While this work is not intended to certify this condition through complex models, some considerations of the paleobiology of P. bachmanni based on manus movement capabilities and body mass are presented. It seems plausible that P. bachmanni would have had both cursorial and flying capabilities. The information provided here represents an effort to discuss features previously unknown in phorusrhacids and to provide new data that may be useful in future systematic, morpho-functional and evolutionary studies.KurzfassungPhorusrhacidae des taxons Psilopterinae sind die kleinsten und grazilsten Raubvögel der großen terrestrisch lebenden Familie Phorusrhacidae, die im Tertiär von Südamerika sehr häufig war. Zwei Taxa aus dem späten Unter-Miozän (Santacrucium) von Patagonien (Argentinien) sind bekannt: Psilopterus lemoinei und Psilopterus bachmanni. Beide wurden ursprünglich sehr oberflächlich beschrieben. Während die erstere Art erst kürzlich neu beschrieben wurde, war das Skelett der Vordergliedmaßen von P. bachmanni bisher praktisch unbekannt. Die Fossilien, die in dieser Arbeit beschrieben werden, stammen aus der Lokalität Puesto Estancia La Costa (=Corriguen Aike), die in der Santa Cruz Provinz liegt. Sie stammen aus den mittleren Schichten der Estancia La Costa Member, Santa Cruz Formation. Das Exemplar besteht aus assoziierten Knochen beider Vordergliedmaßen und einem Fragment der Furcula. Die Hand dieser Art war bisher unbekannt und wird hier im Rahmen dieser Arbeit das erste Mal beschrieben: Ulnare und Radiale sind beide sehr kräftige Knochen, der Carpometacarpus hat kräftige und markante Processi extensorius et alularis. Das Metacarpale majus und die Phalanges digiti majoris sind sehr robust, die Phalanx digiti minoris ist abgeflacht. Frühere Arbeiten gingen davon aus, dass einige Arten der Gattung Psilopterus auf eine schwerfällige Art fliegen konnten. Diese Arbeit kann diese Annahme nicht bestätigen, aber einige neue Annahmen zur Paläobiologie von P. bachmanni präsentieren, die auf den Fähigkeiten der Handbewegungen und der Körpermasse basieren. Es scheint plausibel, dass P. bachmanni sowohl Merkmale eines Laufvogels als auch für Flugfähigkeit in sich vereint. Diese neuen Erkenntnisse ermöglichen es einige Merkmale, die vorher unbekannt für die Phorusrhacidae waren, neu zu bewerten, und liefern neue Daten für zukünftige systematische, funktionsmorphologische und evolutionäre Studien.