 Subjects -> PALEONTOLOGY (Total: 43 journals)
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- Ocean bottom-water oxygenation across the Late Miocene–Early
Pliocene biogenic bloom
Authors: Maria Elena Gastaldello, Claudia Agnini, Laia Alegret
First page: 14
Abstract: The Late Miocene–Early Pliocene biogenic bloom (ca. 9–3.5 millions of years ago, My) represents a period of globally heightened marine biological productivity. Paleoenvironmental studies across this interval show alternating phases of low-oxygen eutrophic and well-oxygenated oligotrophic conditions. Here, we focus on the bottom water oxygenation changes during the biogenic bloom to assess the validity of the enhanced Benthic Foraminifera Oxygen Index (EBFOI). The index was calculated for three ocean drilling sites: Ocean Drilling Program Site 1085 (southeast Atlantic), and International Ocean Discovery Program sites U1506 (southwest Pacific) and U1488 (equatorial Pacific). The quantitative study of benthic foraminiferal assemblages from Site 1488 allowed us to infer the paleoenvironmental evolution across the biogenic bloom. At this site, we document a shift from stable oxygen concentrations and seasonal input of phytodetritus (8.7–4.3 My) to short-term fluctuations between low oxygen eutrophic conditions and well-oxygenated oligotrophic conditions (4.3–3.0 My). The EBFOI calculated at sites 1085 and U1506 was cross-referenced with the published paleoenvironmental conditions. While the EBFOI proves to be a valuable tool to infer paleoenvironmental changes at the seafloor, it has limitations, as evidenced by comparisons with paleoenvironmental interpretations of Site U1488, where it does not consistently align with inferred oxygen conditions.
PubDate: 2024-06-19
DOI: 10.7203/sjp.28131
Issue No: Vol. 39, No. 1 (2024)
- Taphonomy and palaeoenvironmental interpretation of a new amber-bearing
outcrop from the mid-Cretaceous of the Maestrazgo Basin (E Iberian
Peninsula)
Authors: Sergio Álvarez-Parra, Carlos A. Bueno-Cebollada, Eduardo Barrón, Jordi Pérez-Cano, María Victoria Paredes-Aliaga, Cristóbal Rubio, Ana Rodrigo, Nieves Meléndez, Xavier Delclòs, Enrique Peñalver
First page: 32
Abstract: Cretaceous amber-bearing outcrops are numerous and mainly distributed along the Northern Hemisphere. They have been related to extensive resin mass production occurring from the Barremian to the Campanian presumably due to interrelated abiotic and biotic factors. Amber outcrops are also abundant in the Iberian Peninsula, and they are mostly dated as Albian. Here, we present a new amber-bearing outcrop from the Cretaceous of the Maestrazgo Basin called La Dehesa (Estercuel, Aragón, Spain). This locality is assigned to the Boundary Marls Unit and is known for its rich and diverse palaeobotanical record. The dating of the amber-bearing bed is late Albian–early Cenomanian, based on palynomorphs and ostracods. Amber characteristics are compatible with a medium to long-distance transport before resin deposition, i.e., allochthonous origin. Organism-resin interactions have been identified, such as hyphae of resinicolous fungus in the cortex of the amber, a pholadid boring determined as Teredolites clavatus, and an oyster shell that grew on the solidified resin surface. No bioinclusions have been found so far. The study of the microfossils, some of them containing pyrite aggregates or crystals, found in the amber-bearing bed (palynomorphs, plant remains, foraminifers, echinoid spines, ostracods, and vertebrate remains) points to a coastal to inner mixed platform environment.
PubDate: 2024-06-19
DOI: 10.7203/sjp.28426
Issue No: Vol. 39, No. 1 (2024)
- Famennian conodont assemblage in the Compte section (Upper Devonian,
Central Pyrenees) and its comparison with Eurasian sequences
Authors: Héctor Barrera-Lahoz, José I. Valenzuela-Ríos, Jau-Chyn Liao
First page: 70
Abstract: A detailed study of the fossil assemblages of Famennian conodonts has been carried out in the Compte section in the Central Pyrenees. The studied section comprises the upper part of the Comabella Formation, the La Mena Fm and the lower part of the Barousse Fm. Fifty samples have been collected from a 11.73 m thick Famennian stratigraphic succession. Forty–seven lower–middle Famennian conodont taxa have been identified, belonging to four genera: Palmatolepis, Polygnathus, Icriodus and Mehlina. The identified conodont assemblages change through the studied section: in the lower part, Palmatolepis and Icriodus taxa are more frequent and in the overlaying strata, Palmatolepis and Polygnathus taxa are dominant. Several conodont taxa have been recorded for the first time in Central Pyrenees zone. The conodont sequence analysis suggests a lower to middle Famennian age (from the termini to mg. marginifera Zones) in the Compte section (Beds 98–120). On the other hand, a comparison of the Pyrenean conodont assemblages with those from other relevant regions has been carried out. The conodont associations from Compte shows certain similarities with those from western and eastern Europe; however, sequences from eastern and central Asian exhibit some differences.
PubDate: 2024-06-19
DOI: 10.7203/sjp.28695
Issue No: Vol. 39, No. 1 (2024)
- Rhombifera Barrande, 1867, and the origin of the Blastoidea
(Echinodermata, Blastozoa)
Authors: Christopher R. C. Paul, Bertrand Lefebvre, Martina Nohejlová, Samuel Zamora
First page: 90
Abstract: Rhombifera bohemica Barrande is redescribed from Barrande’s original material and new specimens from Spain and the Czech Republic. Rhombifera had a heteromorphic proximal stem, a theca with three basals, three infralaterals and five laterals, both greatly elongated, but a reduced oral area in which five, facet-bearing radials alternate with five interradial orals which form the oral frame. The CD oral plus two others share the hydropore and gonopore. Rhombifera is the only glyptocystitoid rhombiferan with a periproct surrounded by two plates, L4 and L5, and ambulacral facets on radial not oral plates. Rhombifera was derived from echinoencrinitid glyptocystitoids, both sharing reduced oral areas with five, not six, radial plates and pectinirhombs with short oval slits. The oral areas of Rhombifera and Lysocystites are similar. In Lysocystites five facet-bearing ‘ambulacral plates’ alternate with five interradial orals forming the oral frame. Extra orals in the CD interambulacrum share the hydropore and gonopore. Lysocystites, coronates and blastoids all possess three basals, five ‘radials’, five deltoids and five homologues of blastoid lancet plates. We suggest that basals, laterals, radials and orals of glyptocystitoids are homologous with basals, radials, lancet plates and deltoids of blastoids, respectively. Rhombifera is a link between glyptocystitoid rhombiferans and blastoids.
PubDate: 2024-06-19
DOI: 10.7203/sjp.28729
Issue No: Vol. 39, No. 1 (2024)
- Analysing Trophic Competition in †Otodus megalodon and Carcharodon
carcharias through 2D-SEM Dental Microwear
Authors: Maria Victoria Paredes-Aliaga, José Luis Herraiz
First page: 102
Abstract: The extinction of the massive apex predator †Otodus megalodon during the Pliocene is a subject of debate, with climate change and emergence of competitors as potential factors, such as Carcharodon carcharias. We explore trophic interactions of †O. megalodon and the C. carcharias by the analysis of dental microwear. For this purpose, high-resolution casts were made from ten megalodon teeth and six white shark teeth. Then, replicas were produced for examination using a Scanning Electron Microscope. Following a previous work on non-occlusal teeth of bony fishes, density and scratch length as well as mean vector were taken into account for the analysis. Our findings revealed that †O. megalodon shows a slight preference for less abrasive diets compared to C. carcharias. However, no significant differences were found in the dental microwear patterns of both species. These results provide additional evidence of a similar trophic spectrum between C. carchariasand †O. megalodon in the Mediterranean Sea basin, contrasting with previous data obtained through texture analysis. However, due to the inability to estimate sizes, we cannot rule out possible ontogenetic dietary differences. Therefore, future studies estimating sizes and incorporating data from other basins could provide more information.
PubDate: 2024-06-19
DOI: 10.7203/sjp.28830
Issue No: Vol. 39, No. 1 (2024)
- Did large foraging migrations favor the enormous body size of giant
sauropods' The case of Turiasaurus
Authors: Jordi Agusti, Luis Alcalá, Andrés Santos-Cubedo
First page: 110
Abstract: We propose that the huge sizes attained by many sauropod dinosaurs can be explained in the context of a climate characterized by pronounced seasonal changes. Under these conditions, the large herbivores would have become migratory, forced to move great distances during the drier times of year, in which case large body size becomes an adaptive advantage, since large home ranges and the ability to travel great distances increase with size. In this way, the need for a large foraging radius is a potent source of selection for larger size, and the capacity for sauropods to migrate and explore new territory was significantly higher than in extant herbivores. Examples discussed are Turiasaurus riodevensis and Camarasaurus lentus; some of their anatomical structures, such as vertebral neural extensions and crests associated with nasal cavities, can also be explained under this scenario, as adaptations to drought conditions.
PubDate: 2024-06-19
DOI: 10.7203/sjp.28176
Issue No: Vol. 39, No. 1 (2024)
- Theropod swim traces in the Santisol tracksite (Lower Cretaceous), Cameros
Basin, La Rioja, Spain
Authors: Raúl Esperante, Kevin E. Nick
First page: 120
Abstract: Swim traces are rare in dinosaur track sites worldwide. This article reports three sets of theropod swim traces found with walking tracks in the Santisol tracksite (Cameros Basin, La Rioja, Spain). The tracksite contains over one hundred theropod and a few ornithopod walking tracks previously reported. The swim traces are well-preserved and do not show evidence of sediment collapse that characterizes the true tracks. One of the swim traces cuts through one theropod track, indicating that the walking prints formed first, followed by the rise of the water level and the formation of swim traces by swimming theropods.
PubDate: 2024-06-19
DOI: 10.7203/sjp.29023
Issue No: Vol. 39, No. 1 (2024)
- Recensión: Antonio Perejón Rincón “El Instituto Lucas Mallada de
Investigaciones Geológicas. CSIC (1943-1979)”. Consejo Superior de
Investigaciones Científicas, Madrid, 2023, 270 pp.
Authors: Rodolfo Gozalo Gozalo
First page: 122
Abstract: Nos encontramos ante un libro que muestra cual fue la evolución del Instituto Lucas Mallada, una institución
clave en el desarrollo de la Geología en la segunda mitad del siglo XX en España. Por dicho Instituto pasaron
y se formaron muchos de los profesores que luego fueron claves en la formación de los distintos grupos de
investigación geológica de nuestro país. La organización del libro nos conduce a través de la historia de la
institución, su labor formativa y sus principales aportaciones a la ciencia española. Los primeros capítulos están
organizados cronológicamente en cuatro etapas, de acuerdo con los directores del Instituto, que marcaron las
directrices en cada momento y dejaron su impronta en las actividades del Instituto, la captación de personal y
marcaron sus principales líneas de investigación. Simultáneamente se puede colegir los cambios institucionales
que se van produciendo en el CSIC, a los que el Instituto se tiene que ir adaptando, y la paulatina separación de
la Universidad y del CSIC.
PubDate: 2024-06-19
DOI: 10.7203/sjp.29039
Issue No: Vol. 39, No. 1 (2024)
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