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1. Species of Inversiulidae Vigneaux, 1949 (Bryozoa: Cheilostomatida) in the early Miocene of Patagonia (Argentina), with a phylogenetic and palaeobiogeographical analysis of the family.

Author

López-Gappa, Juan, Ezcurra, Martín D., Martha, Silviu O., and Pérez, Leandro M.

Subjects
*ANTARCTIC Circumpolar Current, *MIOCENE Epoch, *BRYOZOA, *SPECIES, *OLIGOCENE Epoch
Abstract

The family Inversiulidae, and its only genus Inversiula, are unique among cheilostome bryozoans owing to the reverse orientation of the operculum, which hinges distally instead of proximally. Inversiula currently includes four extant and one fossil species almost exclusively distributed in the Southern Hemisphere. A phylogenetic analysis of the Inversiulidae based on morphological characters was performed, showing the existence of two clades with contrasting development of the frontal shield. As a result of this analysis, Parainversiula gen. nov. is erected to contain inversiulid species with an umbonuloid frontal shield structure and fewer than 30 central spoked pores. Two poorly known fossil species from the early Miocene of Patagonia (Argentina), originally assigned to the genus Microporella, are here redescribed as Parainversiula sp. and P. chubutiana (Canu) comb. nov. The historical, time-calibrated biogeography of Inversiulidae was estimated using an event-based, multi-model quantitative analysis. The analyses estimated that Australasia was the ancestral area of Parainversiula and a dispersion of the genus into South America occurred between the late Eocene and Oligocene (c. 23–42 Ma), an event that could have been helped by the origin of the Antarctic Circumpolar Current. [ABSTRACT FROM AUTHOR]

Published
2023
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2. SPECIES OF THE GENUS MELICERITA MILNE EDWARDS (BRYOZOA, CHEILOSTOMATIDA) IN THE EARLY MIOCENE OF PATAGONIA (ARGENTINA)

Author

Juan López Gappa and Leandro Martín Perez

Subjects
Cellariidae, Monte León Formation, Chenque Formation, Argentina, Fossil man. Human paleontology, GN282-286.7, Paleontology, QE701-760
Abstract

Species of the cellariid genus Melicerita Milne Edwards develop bilaminar flattened colonies consisting of alternate transverse rows of hexagonal zooids. In South America, its stratigraphic range extends from the early Miocene to the Recent. Re-examination of the type material of M. triforis Ortmann from the Monte León Formation at Río Chalía, and scanning electron microscope images of M. ortmanni Canu from the early Miocene Chenque Formation, confirmed that the latter is a junior synonym of M. triforis. Vicarious avicularia are described for the first time in M. triforis. Lectotypes are herein chosen for both nominal species. M. imperforata sp. nov. is described from material obtained in Monte León Formation (early Miocene). It differs from all known Melicerita species in the size and shape of its vicarious avicularia, which are marginal and much larger than the autozooids. The Recent Magellanic species M. temaukeli Moyano and M. blancoae López Gappa share morphological similarities with M. triforis.

Published
2023
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3. BRYOZOANS ASSOCIATED WITH GASTROPOD SHELLS IN THE EARLY MIOCENE OF PATAGONIA (ARGENTINA).

Author

PÉREZ, LEANDRO M. and LÓPEZ-GAPPA, JUAN

Subjects
*BRYOZOA, *GASTROPODA, *MIOCENE Epoch, *NEOGENE Period
Abstract

This study describes two new species of cheilostome bryozoans associated with gastropod shells from the Monte León Formation (Burdigalian, early Miocene), Argentine Patagonia. Burdwoodipora griffini sp. nov. is the second known species and the first fossil representative of the genus, whose geographic distribution is so far restricted to the Magellan region in the southern southwest Atlantic. it differs from the type species, B. paguricola, in lacking suboral adventitious avicularia in most autozooids. Odontoporella miocenica sp. nov. is morphologically very close to the type species, the Recent O. adpressa, from which it differs in having smaller zooids with fewer areolae and relatively wider orifices. The stratigraphic range of Odontoporella is here extended from the Pleistocene to the early Miocene. its geographic distribution includes southern south America, New Zealand, and New caledonia, suggesting an austral origin of the genus in the Paleogene of former Gondwana. The possible association of these two species with paguroid crabs is discussed. [ABSTRACT FROM AUTHOR]

Published
2022
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4. The stratigraphic and paleoenvironmental significance of the regressive Monte Observación Member, Early Miocene of the Austral Basin, Patagonia

Author

Ana Parras and José I. Cuitiño

Subjects
Monte León Formation, Sedimentology, Fossil Concentrations, Neogene, Southern South America, Argentina, Geology, QE1-996.5, Geophysics. Cosmic physics, QC801-809
Abstract

The stratigraphy of the Oligocene-Miocene southern Patagonia marine deposits has been extensively discussed. However, the Monte Observación Member (MOM) was vaguely defined and many aspects related to its boundaries, distribution, lithology and paleoenvironments of deposition remain uncertain. In this paper we present results obtained from the field survey of several early Miocene outcrops exposed along the Atlantic coast of southern Santa Cruz Province (Austral-Magallanes Basin). They correspond to the transitional interval between the marine shelf Monte León Formation and the terrestrial Santa Cruz Formation. Sedimentological analysis allowed to define six Facies Associations (FAs) for the studied beds: FA-1 corresponds to inner shelf to lower shoreface deposits; FA-2 corresponds to prodelta to distal delta-front deposits; FA-3 corresponds to proximal delta-front deposits; FA-4 corresponds to terminal distributary channels and meandering channels in the delta plain; FA-5 corresponds to inter-distributary bays and tidal flats; and finally FA-6 corresponds to the upper delta plain deposits. In turn, analysis of fossil concentrations allowed defining three main genetic types: biogenic, sedimentologic, and mixed biogenic-sedimentologic concentrations. Biogenic concentrations are represented by beds and lenses of the marginal marine oyster Crassostrea orbignyi (Ihering), which is a significant fossil invertebrate typical of the transitional deposits and is the last invertebrate showing marine influence in all the studied sections and beyond. Sedimentologic and mixed biogenic-sedimentologic concentrations exhibit different attributes and evidence the action of different processes. They include from mostly monospecific within-habitat reworked concentrations, with little post-morten disturbance to polyspecific concentrations bearing the imprint of various taphonomic processes. The distribution of FAs suggest a regressive system that prograded over shelf deposits in the form of deltaic depositional systems with tidal influence. This analysis allowed to define better the MOM, which shows: 1) null to very low bioturbation degrees; 2) a reduced autochthonous invertebrate faunal content; 3) a well-stratified pattern given by the alternating lithologies, and 4) abundant decimetric intercalations of gray to greenish sandstone beds. The fast accumulation of the MOM, which would be part of the regressive phase of the Monte León Formation, could be the consequence of a peak of siliciclastic and volcaniclastic input into the Austral Basin, produced as a result of rapid exhumation of the Southern Patagonian Andes during the early Miocene.

Published
2021

5. A new genus and species of Chaperiidae (Bryozoa: Cheilostomata) from the early Miocene of Patagonia (Argentina)

Author

Juan López-Gappa and Leandro Martín Pérez

Subjects
010506 paleontology, Zooid, Biodiversity, 010502 geochemistry & geophysics, 01 natural sciences, Paleontología, PREDATORY DRILL HOLES, Avicularia, Ciencias de la Tierra y relacionadas con el Medio Ambiente, purl.org/becyt/ford/1 [https], Paleontology, purl.org/becyt/ford/1.5 [https], Genus, Operculum (bryozoa), Bryozoa, Southern Hemisphere, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, biology, CHEILOSTOME BRYOZOAN, Cheilostomata, biology.organism_classification, CHENQUE FORMATION, Geology, CIENCIAS NATURALES Y EXACTAS, MONTE LEÓN FORMATION, PUESTO DEL MUSEO FORMATION
Abstract

La familia Chaperiidae alcanza su máxima biodiversidad en el hemisferio sur. El principal rasgo morfológico que caracteriza a la familia es un par de láminas calcáreas asociadas con la inserción de los músculos oclusores del opérculo. El propósito de este trabajo es describir a Aluis spinettai gen. et sp. nov., a partir de material obtenido en las Formaciones Monte León, Chenque y Puesto del Museo (Mioceno temprano, Patagonia, Argentina). A. spinettai posee colonias erectas bilaminares, suturas crenuladas entre los zooides, un extenso criptocisto y ovicelas esféricas, y carece de gimnocisto, espinas orales y avicularias. La nueva especie exhibe una notable convergencia morfológica con una especie del género Aspidostoma del Mioceno temprano (Fm. Chenque) en Patagonia. En algunas zonas de la colonia los zooides presentaban perforaciones circulares en el criptocisto realizadas por un depredador desconocido. A. spinettai presenta una distribución estratigráfica que va desde ~19 a 17 Ma (Burdigaliano). Su presencia sugiere una correlación entre los niveles superiores de la Formación Monte León y los inferiores de la Formación Chenque. La distribución paleogeográfica de esta nueva especie abarca al menos 500 km a lo largo de la costa atlántica austral de Sudamérica. Los representantes actuales de la familia Chaperiidae en el Atlántico Sudoccidental no parecen relacionados con A. spinetta. The family Chaperiidae reaches its highest biodiversity in the southern hemisphere. The main morphological feature characterizing the family is a pair of calcareous laminar structures associated with the insertion of the operculum occlusor muscles. The aim of this study is to describe Aluis spinettai gen. et sp. nov., from material collected in the Monte León, the Chenque, and the Puesto del Museo formations (early Miocene, Patagonia, Argentina). A. spinettai has erect bilaminar colonies, crenulated sutures between zooids, an extensive cryptocyst and spherical ovicells; gymnocyst, oral spines, and avicularia are absent. The new species exhibits a remarkable morphological convergence with a species of Aspidostoma from the early Miocene (Chenque Formation) of Patagonia. In some areas of the colony, the cryptocysts were pierced by circular drill holes made by an unknown predator. The stratigraphic distribution of A. spinettai ranges from â19 to 17 Ma (Burdigalian). Its presence suggests a correlation between the upper levels of the Monte León Formation and the lower levels of the Chenque Formation. The paleogeographic distribution of this new species spans at least 500 km along the southern Atlantic coast of South America. The living representatives of the Chaperiidae in the Southwest Atlantic do not seem related to A. spinettai. Fil: López Gappa, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Pérez, Leandro Martín. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina

Published
2020

6. Sr-isotope chronostratigraphy of Paleogene–Neogene marine deposits: Austral Basin, southern Patagonia (Argentina)

Author

Parras, Ana, Dix, George R., and Griffin, Miguel

Subjects
*STRONTIUM isotopes, *MARINE sediments, *COASTAL plains, *NEOCENE stratigraphic geology, *PALEOGENE stratigraphic geology, *BRACHIOPODA, *SEDIMENTARY structures
Abstract

Abstract: The Paleogene to Neogene San Julián and Monte León formations underlie the central and eastern parts of the Austral Basin (Patagonia, Argentina), and represent coastal plain to shallow shelf systems within a retroarc foreland basin east of the Andes. The formations are characterized by prominent occurrences of thin (<1 m) densely compacted fossil concentrations, including the large oyster Crassostrea? hatcheri. Formation ages have been problematic given macrofaunal provincialism effectively precluding precise extrabasinal correlations. A Sr-isotope chronostratigraphy based on fossil shell calcite from oysters, pectinids and brachiopods is presented for a regional NE–SW-oriented transect extending ∼200 km along strike of the Austral Basin. The Paleogene–Neogene boundary (∼23 Ma) may occur within the uppermost San Julián Formation (22.68 Ma, with a range between 22.22 and 23.22 Ma), coincident with a prominent glauconitic interval, or in a meteorically altered erosional paleosurface that caps this formation and may correlate with an eustatic sea level fall coincident with the global boundary. The younger Monte León Formation is entirely of early Neogene (Aquitanian to early Burdigalian) age, with ages of 22.12 Ma (21.68–22.58) at the base to 17.91 Ma (17.51–18.29) at the top. The proposed new chronostratigraphic framework forms a foundation for future differentiation of local, regional, and global sedimentary patterns in the Austral Basin during the Paleogene/Neogene transition; in particular, with contemporaneous basins and tectonic blocks across the southern polar region, such as in Australia, New Zealand, and Antarctica. [Copyright &y& Elsevier]

Published
2012
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7. The stratigraphic and paleoenvironmental significance of the regressive Monte Observación Member, Early Miocene of the Austral Basin, Patagonia

Author

Parras, A. and José Ignacio Cuitiño

Subjects
purl.org/becyt/ford/1 [https], purl.org/becyt/ford/1.5 [https], ARGENTINA, NEOGENE, SOUTHERN SOUTH AMERICA, FOSSIL CONCENTRATIONS, Geología, SEDIMENTOLOGY, CIENCIAS NATURALES Y EXACTAS, MONTE LEÓN FORMATION, Ciencias de la Tierra y relacionadas con el Medio Ambiente
Abstract

The stratigraphy of the Oligocene-Miocene southern Patagonia marine deposits has been extensively discussed. However, the Monte Observación Member (MOM) was vaguely defined and many aspects related to its boundaries, distribution, lithology and paleoenvironments of deposition remain uncertain. In this paper we present results obtained from the field survey of several early Miocene outcrops exposed along the Atlantic coast of southern Santa Cruz Province (Austral-Magallanes Basin). They correspond to the transitional interval between the marine shelf Monte León Formation and the terrestrial Santa Cruz Formation. Sedimentological analysis allowed to define six Facies Associations (FAs) for the studied beds: FA-1 corresponds to inner shelf to lower shoreface deposits; FA-2 corresponds to prodelta to distal delta-front deposits; FA-3 corresponds to proximal delta-front deposits; FA-4 corresponds to terminal distributary channels and meandering channels in the delta plain; FA-5 corresponds to inter-distributary bays and tidal flats; and finally FA-6 corresponds to the upper delta plain deposits. In turn, analysis of fossil concentrations allowed defining three main genetic types: biogenic, sedimentologic, and mixed biogenic-sedimentologic concentrations. Biogenic concentrations are represented by beds and lenses of the marginal marine oyster Crassostrea orbignyi (Ihering), which is a significant fossil invertebrate typical of the transitional deposits and is the last invertebrate showing marine influence in all the studied sections and beyond. Sedimentologic and mixed biogenic-sedimentologic concentrations exhibit different attributes and evidence the action of different processes. They include from mostly monospecific within-habitat reworked concentrations, with little post-morten disturbance to polyspecific concentrations bearing the imprint of various taphonomic processes. The distribution of FAs suggest a regressive system that prograded over shelf deposits in the form of deltaic depositional systems with tidal influence. This analysis allowed to define better the MOM, which shows: 1) null to very low bioturbation degrees; 2) a reduced autochthonous invertebrate faunal content; 3) a well-stratified pattern given by the alternating lithologies, and 4) abundant decimetric intercalations of gray to greenish sandstone beds. The fast accumulation of the MOM, which would be part of the regressive phase of the Monte León Formation, could be the consequence of a peak of siliciclastic and volcaniclastic input into the Austral Basin, produced as a result of rapid exhumation of the Southern Patagonian Andes during the early Miocene. Fil: Parras, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: Cuitiño, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina

Published
2018

8. First fossil occurrence of the genus platychelyna hayward and thorpe (Bryozoa: Cheilostomata)

Author

Leandro Martín Pérez, Miguel Griffin, and Juan López-Gappa

Subjects
MONTE LEON FORMATION, 010506 paleontology, ARGENTINA, biology, Smittinidae, Cheilostomata, Paleontology, 010502 geochemistry & geophysics, biology.organism_classification, 01 natural sciences, Archaeology, SMITTINIDAE, Paleontología, Ciencias de la Tierra y relacionadas con el Medio Ambiente, Geography, Genus, EARLY MIOCENE, Bryozoa, Ecology, Evolution, Behavior and Systematics, CIENCIAS NATURALES Y EXACTAS, 0105 earth and related environmental sciences, NEW SPECIES
Abstract

Platychelyna secunda sp. nov. is described based on material collected in the Monte León Formation, Patagonia, Argentina (early Miocene). This is the second species of Platychelyna Hayward and Thorpe to be described and the first fossil representative, expanding the stratigraphic range of the genus by ~20 Ma. P. secunda and P. planulata Hayward show similar geographic distributions in the southern tip of South America. Zooid size is ~50% larger in the recent species compared to the fossil one, which could be related to the cooling of the water masses in the Southwest Atlantic since the opening of the Drake Passage towards the end of the Oligocene. Fil: López Gappa, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Pérez, Leandro Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina Fil: Griffin, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina

Published
2018

9. New and little-known bryozoans from Monte León Formation (early Miocene, Argentina) and their paleobiogeographic relationships

Author

Miguel Griffin, Juan López-Gappa, and Leandro Martín Pérez

Subjects
0106 biological sciences, 010506 paleontology, biology, Range (biology), Ecology, Fauna, Paleontology, biology.organism_classification, Neogene, 010603 evolutionary biology, 01 natural sciences, Ciencias de la Tierra y relacionadas con el Medio Ambiente, PATAGONIA, EARLY MIOCENE, South american, Calyptotheca, Bryozoa, BRYOZOA, Meteorología y Ciencias Atmosféricas, Cenozoic, CIENCIAS NATURALES Y EXACTAS, Geology, MONTE LEÓN FORMATION, 0105 earth and related environmental sciences
Abstract

The bryozoan fauna from the South American Cenozoic is poorly known. The study of new material collected in the Monte León Formation (early Miocene), gave us the opportunity to describe four new species: Valdemunitella canui n. sp., Foveolaria praecursor n. sp., Neothoa reptans n. sp., and Calyptotheca santacruzana n. sp. Two of them (V. canui and C. santacruzana) were first recorded by F. Canu and interpreted as recent species from the Australian bryozoan fauna, but are herein described as new species. The stratigraphic range of Otionella parvula (Canu, 1904) is extended to the early Miocene. The present study emphasizes the close relationships between the South American Neogene bryozoan faunas and those of other Gondwanan sub-continents such as New Zealand and Australia. Fil: Pérez, Leandro Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina Fil: López Gappa, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina Fil: Griffin, Miguel. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Published
2015

10. A new Patagonian long-lived species of Cyclochlamys Finlay, 1926 (Bivalvia: Pectinoidea)

Author

Miguel Griffin and Roberto Santiago Guido Pastorino

Subjects
010506 paleontology, ARGENTINA, biology, Paleontology, Pectinoidea, Biología Marina, Limnología, 010502 geochemistry & geophysics, Bivalvia, biology.organism_classification, 01 natural sciences, SOUTHWESTERN ATLANTIC, Ciencias Biológicas, Geography, CYCLOCHLAMYDIDAE, Humanities, Ecology, Evolution, Behavior and Systematics, CIENCIAS NATURALES Y EXACTAS, 0105 earth and related environmental sciences, MONTE LEÓN FORMATION
Abstract

A new species of the bivalve family Cyclochlamydidae is described from the southwestern Atlantic in Argentine waters. Cyclochlamys argentina sp. nov. is the second representative of the genus known to live in the Magellanic area. In addition, this long-lived species is also recorded from lower Miocene rocks in the province of Santa Cruz exposed along the Atlantic coast of the Monte León National Park. The material was collected from the Punta Entrada Member of the Monte León Formation. These small mollusks clearly belong in Cyclochlamys because of shell characters such as the irregularly pitted prodissoconch I and right valve with commarginally elongated rectangular prisms over most of disc. Cyclochlamys argentina sp. nov. shows affinities with taxa such as C. aupouria and C. shepherdi, all of which are known from areas of New Zealand. Fil: Pastorino, Roberto Santiago Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Griffin, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentina

Published
2018

11. First record of a fossil selenariid bryozoan in South America

Author

Juan López-Gappa, Miguel Griffin, and Leandro Martín Pérez

Subjects
0106 biological sciences, 010506 paleontology, biology, Monte León Formation, lyrula-like denticle, Argentina, Paleontology, biology.organism_classification, 010603 evolutionary biology, 01 natural sciences, Archaeology, Bryozoa, Avicularia, lower Miocene, Ciencias de la Tierra y relacionadas con el Medio Ambiente, Geography, Patagonia, Ciencias Naturales, Lrula-like denticle, Meteorología y Ciencias Atmosféricas, Selenariidae, Ecology, Evolution, Behavior and Systematics, CIENCIAS NATURALES Y EXACTAS, 0105 earth and related environmental sciences
Abstract

Selenariidae Busk 1854 (Bryozoa) is considered endemic to Australia and New Zealand. Here we describe a new species of Selenaria Busk 1854 from the lower Miocene Monte León Formation (Patagonia, Argentina). Selenaria lyrulata sp. nov. is characterized by autozooids with a lyrula-like, anvil-shaped cryptocystal denticle, opesiular indentations and lateral condyles, as well as avicularia with a shield of fused costae. This is the first record of a selenariid bryozoan in South America., Facultad de Ciencias Naturales y Museo

Published
2017

12. Sr-isotope chronostratigraphy of Paleogene-Neogene marine deposits: Austral Basin, southern Patagonia (Argentina)

Author

Ana Parras, Miguel Griffin, and George R. Dix

Subjects
Geology, Structural basin, Neogene, Geociencias multidisciplinaria, Ciencias de la Tierra y relacionadas con el Medio Ambiente, Paleontology, PATAGONIA, AUSTRAL BASIN, SAN JULIÁN FORMATION, SR-ISOTOPE ANALYSIS, Geología, Chronostratigraphy, Paleogene, PALEOGENE-NEOGENE BOUNDARY, CIENCIAS NATURALES Y EXACTAS, Earth-Surface Processes, MONTE LEÓN FORMATION
Abstract

The Paleogene to Neogene San Julián and Monte León formations underlie the central and eastern parts of the Austral Basin (Patagonia, Argentina), and represent coastal plain to shallow shelf systems within a retroarc foreland basin east of the Andes. The formations are characterized by prominent occurrences of thin (

Published
2012

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