11 research outputs found
Ichthyosaur embryos outside the mother body: not due to carcass explosion but to carcass implosion
Family Dibrachicystidae (Echinodermata: Rhombifera) from the âMiddleâ Cambrian of the Barrandian area, Czech Republic
Early evolution of the ossicular chain in Cetacea: into the middle ear gears of a semi-aquatic protocetid whale
New species and stratigraphic data on Lower Bajocian (Middle Jurassic) lytoceratids (Ammonoidea) from LĂłkĂșt, Bakony Mts, Hungary
From exceptionally rich and mostly well-preserved
Lower Bajocian ammonite assemblages, eight
lytoceratid species are described and discussed in detail.
They belong to four genera (Lytoceras, Megalytoceras,
Alocolytoceras and Nannolytoceras) and include some
stratigraphically important forms. Thus the material yielded
the hitherto known youngest (Lower Bajocian Otoites
sauzei Zone) representative of genus Alocolytoceras
(A. isztimeri n. sp.). On the basis of here-identified forms,the range of Lytoceras subfrancisci could be extended up into the Otoites sauzei Zone. A new species (Nannolytoceras gibbosum n. sp.) from the Witchellia laeviuscula/Otoites sauzei zonal boundary interval suggests that the origin of Nannolytoceras could have been earlier than previously recorded. The faunal compositions of the assemblages reflect a typical Tethyan character, with lytoceratids representing only the third most numerous ammonite group behind Phylloceratina and Ammonitina
Chaniella, a new lower Tremadocian (Ordovician) brachiopod from northwestern Argentina and its phylogenetic relationships within basal rhynchonelliforms
The new rhynchonelliform brachiopod Chaniella pascuali n. gen. n. sp. is described from the lower Tremadocian Guayoc Chico Group of northwestern Argentina. Cladistic analysis shows that Chaniella is closest to the billingsellides Protambonites and Korinevskia. The particular combination of features of the new genus, in particular the presence of narrow lateral deltidial plates instead of a complete pseudodeltidium, led to the designation of the new monotypic family Chaniellidae. Parsimony analysis supports the separation of clitambonitidines and billingsellidines as monophyletic clades within the order Billingsellida and places the protorthide Arctohedra and the orthides Jivinella and Bohemiella close to the ancestry of the billingsellides.Fil: Benedetto, Juan Luis Arnaldo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Exactas FĂsicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentin
Chaniella, a new lower Tremadocian (Ordovician) brachiopod from northwestern Argentina and its phylogenetic relationships within basal rhynchonelliforms
Huncalotis, an enigmatic new pectinoid genus (Bivalvia, Late Jurassic) from South America
Float, explode or sink: postmortem fate of lung-breathing marine vertebrates
What happens after the death of a marine tetrapod in seawater? Palaeontologists and neontologists have claimed that large lung-breathing marine tetrapods such as ichthyosaurs had a lower density than seawater, implying that their carcasses floated at the surface after death and sank subsequently after leakage of putrefaction gases (or ââcarcass explosionsââ). Such explosions would thus account for the skeletal disarticulation observed frequently in the fossil record. We examined the taphonomy and sedimentary environment of numerous ichthyosaur skeletons and compared them to living marine tetrapods, principally cetaceans, and measured abdominal pressures in human carcasses. Our data and a review of the literature demonstrate that carcasses sink and do not explode (and spread skeletal elements). We argue that the normally slightly negatively buoyant carcasses of ichthyosaurs would have sunk to the sea floor and risen to the surface only when they remained in shallow water above a certain temperature and at a low scavenging rate. Once surfaced, prolonged floating may have occurred and a carcass have decomposed gradually. Our conclusions are of significance to the understanding of the inclusion of carcasses of lung-breathing vertebrates in marine nutrient recycling. The postmortem fate has essential implications for the interpretation of vertebrate fossil preservation (the existence of complete, disarticulated fossil skeletons is not explained by previous hypotheses), palaeobathymetry, the physiology of modern marine lung-breathing tetrapods and their conservation, and the recovery of human bodies from seawater