Search results for "e7"
showing 10 items of 152 documents
Almost disjoint families of countable sets and separable complementation properties
2012
We study the separable complementation property (SCP) and its natural variations in Banach spaces of continuous functions over compacta $K_{\mathcal A}$ induced by almost disjoint families ${\mathcal A}$ of countable subsets of uncountable sets. For these spaces, we prove among others that $C(K_{\mathcal A})$ has the controlled variant of the separable complementation property if and only if $C(K_{\mathcal A})$ is Lindel\"of in the weak topology if and only if $K_{\mathcal A}$ is monolithic. We give an example of ${\mathcal A}$ for which $C(K_{\mathcal A})$ has the SCP, while $K_{\mathcal A}$ is not monolithic and an example of a space $C(K_{\mathcal A})$ with controlled and continuous SCP …
Tectogonotoechia rivasi n. sp. A new lower Pragian Celtiberian (Spain) Ancystrorhynchoidea rhynchonellid brachiopod
2020
A new lower Pragian Ancystrorhynchoidea rhynchonellid, Tectogonotoechia rivasi n. sp. of the Celtiberian region (Eastern Iberian Chain, EIC, and Eastern Guadarrama, EG) is described and figured. The growth of the new species, from the last neanic stage to the senescent one is specially underlined. T. rivasi n. sp. is characterized as the other species of the genus by the occurrence of a pseudoseptum and a pseudoseptalium in the dorsal interior, with a fine connectivum forming a roofed over structure covering most part of the latter. Exteriorly, the species is an entirely costate, strongly dorsibiconvex, uniplicate form lacking of marginal spines. T. rivasi n. sp. is fairly abundant in the u…
Diversity of large ornithopod dinosaurs in the upper Hauterivian-lower Barremian (Lower Cretaceous) of Teruel (Spain): a morphometric approach
2020
We report some large ornithopod vertebrae from two upper Hauterivian-lower Barremian (Lower Cretaceous) localities in El Castellar (Maestrazgo Basin, Teruel,Spain).These fossils have been studied systematically as well as morphometrically using a multivariate analysis in order to analyse the diversity of the sample. In fact, principal component analysis has been demonstrated as a useful tool for establishing affinities in isolated iguanodontian vertebrae, at least when size effect is not removed from the analysed dataset. As result of this study, twolarge indeterminate styracosternans are distinguished in the sample: a large one with platycoelus anterior caudal vertebrae related to the gene…
Early Jurassic (Sinemurian to basal Toarcian) ammonites of the Brescian Prealps (Southern Alps, Italy).
2017
This work provides a more precise up-to-date biostratigraphical framework of the Early Jurassic ammonite succession of the Brescian Prealps with more than seventy taxa for the Sinemurian, Pliensbachian and basal Toarcian corresponding to a about 30 horizons or faunal assemblages rather well correlable with the NW European standard zonation. These results are supported with already published data, new data from recent field investigations, revised contributions of different authors and with the study of the historical collection of the Museum of Natural Sciences of Brescia (Northern Italy). The biohorizons are referred to the Lower Jurassic carbonate series of the Brescian Prealps, cropping …
Preparation protocols for SEM visualization of charred fossil plants: the case of Weichselia reticulata pinnule anatomy
2021
The cosmopolite Mesozoic fern Weichselia reticulata presents many peculiarities in the anatomy of its stem as well as in the architecture of its leaves. Previous analyses of the ultrastructure of their pinnule laminas provided some insight on xeromorphic traits. In this work new protocols for the preparation of charred compression foliage specimens embedded in a limestone matrix for their observation under SEM are presented, which enhance the observation of different plant tissues. The preparation with HCl allows for the visualization of the whole lamina, from the upper to the lower epidermis, which had not been done to date. Additionally, collodion, latex, or wax coverings of the fossils b…
David Malcolm Raup (1933-2015) at the starting point of a new paradigm for Palaeontology
2020
This is a tribute to the late David Malcolm Raup, one of the major palaeontologists of the second half of the 20 th century. In addition, it is a critical review of his outstanding contributions, mainly in the field of theoretical palaeontology: quantitative modelling, the introduction of probabilistic methods in palaeontology, as well as his great imagination to use techniques from other fields, such as insurance actuary. After a general outline of his youth, I present a general depiction of the main topics of his research as a palaeobiologist: morphology, the structure of the fossil record, evolution, and extinction. He covered areas ranging from the theoretical morphology of coiled shell…
Has palaeontology answers for some current environmental problems?
2021
History as an irreversible process has no role from a uniformitarian point of view in geology and palaeobiology. Contingency is another trait of history and particle palaeontology has its foundation on such principles. However, new approaches in physics and the theory of systems point out the need to consider a time arrow. Moreover, chance and necessity are interwoven in synergetics and self-organization theory and there may be some possibility of prediction. The global biota has a history resulting from a process of self-organization. A rich fossil record was produced during the Phanerozoic times and this fossil record shows us how life overcame several important crisis. A clear understand…
The negligence and lazy of the Administration: the greatest danger to the conservation of the unique lagerstätte sites
2019
An example is given of one of the most important sites in the Spanish fossil record, such as the almost a hundred moulds of ancient jellyfish of hydrozoan Medusozoa, Cnidaria, exceptionally preserved in an arkosic greywacke bedding plane of the Corduban/Terreneuvian Epoch (lowermost Cambrian) in the municipal district of Constantina (Seville). In spite of its scientific-patrimonial importance and the fact that it has been brought to the attention of the Andalusian autonomous administration for more than twenty-five years, it has still not been the object of an adequate legal protection figure. This lack of interest or bureaucratic slowness is causing an irreparable loss in many of its eleme…
TESTING SIMILARITY COEFFICIENTS FOR ANALYSIS OF THE FOSSIL RECORD USING CLUSTERING METHODS: THE PALAEOZOIC FLORA AS A STUDY CASE
2020
This paper reports a global methodological approach based on the similarity and clustering methods of the Palaeozoic plant fossil record using a comparative approach between two similarity measures: the Jacard and Raup-Crick Coefficients. The results show that although the Raup-Crick Coefficients clearly have the potential for providing more robust results, the consequences of the extinction processes are better reflected in the similarity analysis based on the Jaccard Coefficients. On the other hand, the cluster analysis based on UPGMA algorithm shows four robust clusters and reveals new evidence for the singularity of Mississippian flora. Finally, the results obtained reveal that similari…
The trace fossil gyrochorte: ethology and paleoecology
2021
Specimens of the trace fossil Gyrochorte from the Ordovician, Jurassic and Cretaceous of Utah, and the Pliocene of Spain are described. These occurrences expand the stratigraphic range of the ichnogenus, and allow for a reexamination of this paleoenvironmentally sensitive and puzzling trace fossil. The recognition of the penetrative characteristic of the trace is essential for a correct identification, as some trace fossils have been erroneously ascribed to Gyrochorte in the past. The producer must have been a detritus-feeding worm-like animal, probably an annelid, that created a bilobed, vertically penetrating and sometimes plaited meandering trace. Gyrochorte typically occurs in sandy f…