52 research outputs found
An Eocene orthocone from Antarctica shows convergent evolution of internally shelled cephalopods
Background The Subclass Coleoidea (Class Cephalopoda) accommodates the diverse present-day internally shelled cephalopod mollusks (Spirula, Sepia and octopuses, squids, Vampyroteuthis) and also extinct internally shelled cephalopods. Recent Spirula represents a unique coleoid retaining shell structures, a narrow marginal siphuncle and globular protoconch that signify the ancestry of the subclass Coleoidea from the Paleozoic subclass Bactritoidea. This hypothesis has been recently supported by newly recorded diverse bactritoid-like coleoids from the Carboniferous of the USA, but prior to this study no fossil cephalopod indicative of an endochochleate branch with an origin independent from subclass Bactritoidea has been reported. Methodology/Principal findings Two orthoconic conchs were recovered from the Early Eocene of Seymour Island at the tip of the Antarctic Peninsula, Antarctica. They have loosely mineralized organic-rich chitincompatible microlaminated shell walls and broadly expanded central siphuncles. The morphological, ultrustructural and chemical data were determined and characterized through comparisons with extant and extinct taxa using Scanning Electron Microscopy/Energy Dispersive Spectrometry (SEM/EDS). Conclusions/Significance Our study presents the first evidence for an evolutionary lineage of internally shelled cephalopods with independent origin from Bactritoidea/Coleoidea, indicating convergent evolution with the subclass Coleoidea. A new subclass Paracoleoidea Doguzhaeva n. subcl. is established for accommodation of orthoconic cephalopods with the internal shell associated with a broadly expanded central siphuncle. Antarcticerida Doguzhaeva n. ord., Antarcticeratidae Doguzhaeva n. fam., Antarcticeras nordenskjoeldi Doguzhaeva n. gen., n. sp. are described within the subclass Paracoleoidea. The analysis of organic-rich shell preservation of A. nordenskjoeldi by use of SEM/EDS techniques revealed fossilization of hyposeptal cameral soft tissues. This suggests that a depositional environment favoring soft-tissue preservation was the factor enabling conservation of the weakly mineralized shell of A. nordenskjoeldi.Facultad de Ciencias Naturales y Muse
An Eocene orthocone from Antarctica shows convergent evolution of internally shelled cephalopods
Background The Subclass Coleoidea (Class Cephalopoda) accommodates the diverse present-day internally shelled cephalopod mollusks (Spirula, Sepia and octopuses, squids, Vampyroteuthis) and also extinct internally shelled cephalopods. Recent Spirula represents a unique coleoid retaining shell structures, a narrow marginal siphuncle and globular protoconch that signify the ancestry of the subclass Coleoidea from the Paleozoic subclass Bactritoidea. This hypothesis has been recently supported by newly recorded diverse bactritoid-like coleoids from the Carboniferous of the USA, but prior to this study no fossil cephalopod indicative of an endochochleate branch with an origin independent from subclass Bactritoidea has been reported. Methodology/Principal findings Two orthoconic conchs were recovered from the Early Eocene of Seymour Island at the tip of the Antarctic Peninsula, Antarctica. They have loosely mineralized organic-rich chitincompatible microlaminated shell walls and broadly expanded central siphuncles. The morphological, ultrustructural and chemical data were determined and characterized through comparisons with extant and extinct taxa using Scanning Electron Microscopy/Energy Dispersive Spectrometry (SEM/EDS). Conclusions/Significance Our study presents the first evidence for an evolutionary lineage of internally shelled cephalopods with independent origin from Bactritoidea/Coleoidea, indicating convergent evolution with the subclass Coleoidea. A new subclass Paracoleoidea Doguzhaeva n. subcl. is established for accommodation of orthoconic cephalopods with the internal shell associated with a broadly expanded central siphuncle. Antarcticerida Doguzhaeva n. ord., Antarcticeratidae Doguzhaeva n. fam., Antarcticeras nordenskjoeldi Doguzhaeva n. gen., n. sp. are described within the subclass Paracoleoidea. The analysis of organic-rich shell preservation of A. nordenskjoeldi by use of SEM/EDS techniques revealed fossilization of hyposeptal cameral soft tissues. This suggests that a depositional environment favoring soft-tissue preservation was the factor enabling conservation of the weakly mineralized shell of A. nordenskjoeldi.Facultad de Ciencias Naturales y Muse
Primer mamÃfero Mesozoico de Chile: el registro más austral de un gondwanaterio del Cretácico tardÃo
Se describe a Magallanodon baikashkenke gen. et. sp. nov., un nuevo mamÃfero gondwanaterio del Cretácico tardÃo de la Región de Magallanes, en el sur de Chile (Valle del RÃo de Las Chinas, Estancia Cerro Guido, norte de Puerto Natales, Provincia de Última Esperanza). Las capas portadoras se ubican entre los niveles del Campaniano tardÃo-Maastrichtiano temprano de la Formación Dorotea (Cuenca de Magallanes/Austral). Los nuevos restos constituyen el registro más austral de un mamÃfero gondwanaterio del Mesozoico, como asà también el primer mamÃfero Mesozoico conocido para Chile. El nuevo taxón es comparable en tamaño a las formas hipsodontes Gondwanatherium (Cretácico tardÃo) y Sudamerica (Paleoceno temprano), pero con molares notoriamente braquidontes soportados por cuatro a cinco raÃces. Como en otros gondwanaterios, posee al menos un incisivo superior rodentiforme en la serie superior. Se diagnostica y describe brevemente el nuevo taxón, considerado tentativamente como un ferugliotérido (Ferugliotheriidae). De confirmarse esta asignación, este nuevo taxón representarÃa el miembro de mayor tamaño para la familia. El patrón oclusal de los molariformes, con el desgaste, se semeja también al de otros gondwanaterios, en particular al de los ferugliotéridos y al del sudamerÃcido Gondwanatherium, agregando en consecuencia más evidencias en favor de la proximidad filogenética entre ambas familias. Se llevó a cabo un análisis de la microestructura del esmalte del incisivo superior de Magallanodon; como resultado, se encontraron varias similitudes importantes con el patrón existente en Gondwanatherium (Sudamericidae). Se discute la significación de Magallanodon en la adquisición, entre los gondwanaterios, de un patrón molariforme caracterizado por la presencia de lofos transversos. Finalmente, se discute la significación del nuevo hallazgo en el contexto de las biotas australes, incluyendo aquellas de Patagonia y Antártica.We describe Magallanodon baikashkenke gen. et. sp. nov., a new gondwanatherian mammal from the Late Cretaceous of the Magallanes Region in southern Chile (RÃo de Las Chinas Valley, Estancia Cerro Guido, north of Puerto Natales city, Última Esperanza Province). The mammal-bearing layer is placed within the Late Campanian-Early Maastrichtian levels of the Dorotea Formation (Magallanes/ Austral Basin). The new remains constitute the southernmost record of a Mesozoic gondwanatherian mammal, as well as the first Mesozoic mammal from Chile. This taxon is comparable in size to the hypsodont-toothed Gondwanatherium (Late Cretaceous) and Sudamerica (Early Paleocene) but with noticeably brachyodont molariforms supported by four to five roots. As in other gondwanatherians, it has at least one hypertrophied, rodent-like incisor in the upper jaw. The new taxon is here diagnosed and described, and is regarded as a possible ferugliotheriid (?Ferugliotheriidae). If confirmed, it would represent the largest known taxon for this family. Its molariform occlusal crown pattern, after wear, resembles that of other gondwanatherians, particularly ferugliotheriids and that of the sudamericid Gondwanatherium. This adds new evidence on the phylogenetic proximity of ferugliotheriid and sudamericid gondwanatherians. An analysis of the enamel microstructure of the upper incisor of Magallanodon was performed demonstrating several crucial similarities with the pattern shown by Gondwanatherium (Sudamericidae). We discuss the significance of Magallanodon for understanding the acquisition, within gondwanatherians, of a lophed molariform pattern. Finally, we discuss the significance of the new finding in the context of southern biotas, including those of Patagonia and Antarctica.Fil: Goin, Francisco Javier. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División PaleontologÃa Vertebrados; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata; ArgentinaFil: Martinelli, AgustÃn Guillermo. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Soto Acuña, Sergio. Universidad de Santiago de Chile. Facultad de Ciencias; ChileFil: Vieytes, Emma Carolina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División ZoologÃa de Vertebrados; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata; ArgentinaFil: Manriquez, Leslie. Universidad de Vale do Rio dos Sinos; BrasilFil: Fernandez, Roy A.. Universidad de Santiago de Chile. Facultad de Ciencias; ChileFil: Pino, Juan Pablo. Instituto Antártico Chileno; ChileFil: Trevisan Cristine. Instituto Antártico Chileno; ChileFil: Kaluza, Jonatan Ezequiel. Universidad de Santiago de Chile. Facultad de Ciencias; Chile. Fundación de Historia Natural Félix de Azara; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Reguero, Marcelo Alfredo. Museo Nacional de Historia Natural de Santiago; Chile. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata; ArgentinaFil: Leppe, Marcelo. Instituto Antártico Chileno; ChileFil: Ortiz, Hector. Universidad de Santiago de Chile. Facultad de Ciencias; ChileFil: Rubilar Rogers, David. Museo Nacional de Historia Natural de Santiago; ChileFil: Vargas, Alexander. Universidad de Santiago de Chile. Facultad de Ciencias; Chil
Late Mesozoic marine Antarctic fishes: future perspectives based on the newly collections recovered in the Ameghino and Lopez de Bertodano Formations
Nowadays, notothenioids are the teleostean group that dominates marine Antarctic waters. However, during the Mesozoic a diverse ichthyofauna inhabited the sea that surrounded Antarctic. We present the preliminary results of the last two Argentinian Antarctic field expedition to the Late Jurassic of Antactic Peninsula (Longing Gape) and Cretaceous-Paleogene of Seymour (=Marambio) Island. The fish material recovered is extremely abundant and their further detailed study may provide significant clues into the taxonomy and paleobiogeography of the mesozoic antactic ichthyofaúnas.Facultad de Ciencias Naturales y Museo (FCNM
First record of Toxodontidae (Mammalia, Notoungulata) from the late Miocene–early Pliocene of the southern central Andes, NW Argentina
Late Mesozoic marine Antarctic fishes: future perspectives based on the newly collections recovered in the Ameghino and Lopez de Bertodano Formations
Nowadays, notothenioids are the teleostean group that dominates marine Antarctic waters. However, during the Mesozoic a diverse ichthyofauna inhabited the sea that surrounded Antarctic. We present the preliminary results of the last two Argentinian Antarctic field expedition to the Late Jurassic of Antactic Peninsula (Longing Gape) and Cretaceous-Paleogene of Seymour (=Marambio) Island. The fish material recovered is extremely abundant and their further detailed study may provide significant clues into the taxonomy and paleobiogeography of the mesozoic antactic ichthyofaúnas.Facultad de Ciencias Naturales y Museo (FCNM
Carnivorans at the Great American Biotic Interchange: new discoveries from the northern neotropics
Weddellian marine/coastal vertebrates diversity from a basal horizon (Ypresian, Eocene) of the Cucullaea I Allomember, La Meseta formation, Seymour (Marambio) Island, Antarctica
The La Meseta Formation crops out in Seymour/Marambio Island, Weddell Sea, northeast of the Antarctic Peninsula and contains one of the world's most diverse assemblages of Weddellian marine/coastal verte-brates of Early Eocene (Ypresian) age. The La Meseta Formation is composed of poorly consolidated, marine sandstones and siltstones which were deposited in a coastal, deltaic and/or estuarine environment. It includes marine invertebrates and vertebrates as well as terrestrial vertebrates and plants. The highly fossiliferous basal horizon (Cucullaeashell bed, Telm 4 of Sadler 1988) of the CucullaeaI Allomember is a laterally extensive shell bed with sandy matrix. The fish remains, including 35 species from 26 families, of the Ypresian Cucullaeabed represent one of the most abundant and diverse fossil vertebrate faunas yet recorded in southern latitudes. Stratigraphic distribution and phylogenetic relationships of the Weddellian sphenisciforms are consistent with a first radiation of this group in the Early Eocene. The first inquestionable archaeocete from Antarctica is recorded in this unit and is referred to a new taxon
Réplica a los comentarios de E. P. Tonni y A. L. Cione sobre la geocronologÃa, estratigrafÃa y paleontologÃa de vertebrados de la Fm. UquÃa en el perfil de Esquina Blanca, Jujuy
5 páginas.Peer reviewe
Identification of type materials of the species of Protypotherium Ameghino, 1885 and Patriarchus Ameghino, 1889 (Notoungulata: Interatheriidae) erected by Florentino Ameghino
Fernández, Mercedes, Fernicola, Juan Carlos, Cerdeño, Esperanza, Reguero, Marcelo A. (2018): Identification of type materials of the species of Protypotherium Ameghino, 1885 and Patriarchus Ameghino, 1889 (Notoungulata: Interatheriidae) erected by Florentino Ameghino. Zootaxa 4387 (3): 473-498, DOI: https://doi.org/10.11646/zootaxa.4387.3.
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