L’une des toutes premières ammonites à coquille presque oxycône observée dans les séries fossilifères après la crise faunique de la limite Trias/Jurassique est décrite. Elle provient du Sinémurien inférieur (chronozone à Semicostatum ou à Turneri) de Bourgogne (Mavilly-Mandelot, Côte-d’Or, France). Cette nouvelle forme, Oxyarietites boletzkyi n. gen., n. sp., possède une coquille involute, comprimée et carénée dont le type clairement suboxycône est nouveau pour le Sinémurien inférieur. En raison de son aire ventrale carénée, ce taxon se rattache probablement à la super-famille des Arietitoidea Hyatt, 1875 sensu Guex (1995) mais son attribution familiale est incertaine et son origine évolutive reste énigmatique. Outre son intérêt taxonomique, cette découverte est importante car elle pose le problème de la valeur adaptative des caractères liés à la géométrie des coquilles d’ammonites. Il est actuellement admis que les coquilles involutes, comprimées et carénées de type suboxycône et oxycône favorisent significativement l’hydrodynamisme et donc la mobilité des espèces qui les possèdent. Il est surprenant que l’acquisition de ce probable avantage adaptatif n’ait pas favorisé l’implantation au sein des peuplements du nouveau taxon, qui reste une forme rare. Dans tous les cas, la découverte d’O. boletzkyi n. gen., n. sp. rajeunit d’environ 2 millions d’années la mise en place des morphologies oxycônes au cours de la phase de reconstitution de la biodiversité post-crise Trias/Jurassique. Oxyarietites boletzkyi n.gen., n. sp., a new genus and species of ammonite for the Lower Sinemurian of Burgundy (France): a rare forerunner of the oxycone morphologies for the Jurassic. One of the very first quasi-oxycone ammonites following the Triassic/Jurassic boundary crisis is described. It was collected from the fossiliferous Lower Sinemurian (Semicostatum or Turneri Chronozone) strata of Burgundy (Mavilly-Mandelot, Côte-d’Or, France). The new taxon, Oxyarietites boletzkyi n. gen., n.sp., possesses an involute, compressed and keeled shell of suboxycone morphology, a shell type previously unknown for the Lower Sinemurian. The discovery makes younger by about 2 Ma the emergence of keeled (sub)oxycone shells following the Triassic/Jurassic boundary crisis. Its obviously keeled ventral area allows a probable assignation to the Arietitoidea Hyatt, 1875 sensu Guex (1995) superfamily, but family level assignation and its evolutionary origin remain obscure. Although, it is generally accepted that involute, compressed and keeled suboxycone and oxycone ammonite shells possess the best hydrodynamical abilities and mobility, the acquisition of this probable adaptive advantage in O. boletzkyi n. gen., n. sp. does not go together with abundancy in the fossil record.
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In this paper, we investigate the potential use of oxygen and strontium isotope ratios (d18Op and 87Sr/86Sr) measured in archaeological fish enamel as provenance indicators. d18Op and 87Sr/86Sr were measured in a suite of archaeological carp remains recovered from the Anatolian townsite of Sagalassos dated to the Early Byzantine period (AD 450e650) and compared to that of modern fish, river and lake waters from the Anatolian region. We used sequential leaches in weak acetic acid to remove diagenetic Sr from fossil tooth enamel, monitoring the effectiveness of this approach by measuring the Sr/Ca ratios of the leachates via an isotope dilution thermal ionization mass spectrometry method (ID-TIMS). d18Op values mostly excluded a riverine origin. 87Sr/86Sr ratios of one fish overlapped with the 87Sr/86Sr signatures of two lakes in the Anatolian region, and at least one lake (Gölcük) could be removed as a candidate owing to a very distinctive 87Sr/86Sr signature not found in any of the fish remains. Most of the tooth samples analyzed could not be assigned a precise geographical origin since the 87Sr/86Sr ratios measured in enamel did not match that of any of the local lakes selected as potential origin. This result suggests that carp may have originated from lakes that have not yet been sampled, although this conclusion is not supported by other archaeological evidence. Alternatively, the lack of correspondence between lakes and fish Sr isotope ratios highlights several possible sources of uncertainties including spatial heterogeneity in 87Sr/86Sr ratio within a lake, the contribution of dietary strontium to the 87Sr/86Sr ratio of fish tooth enamel, and post-mortem alteration of the tooth Sr isotope signal during fossilization. In spite of the high precision of the strontium isotope analyses and the wide range of variation in the surface waters of the Anatolian lakes and rivers, this method may remain limited to distinguishing between lakes situated in regions of bedrock of very distinct age and geology until these sources of uncertainty are more fully investigated.
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Late Devonian aquatic environments hosted the fin-to-limb transition in vertebrates. Upper Devonian (ca. 365–360 Ma) strata in Pennsylvania, USA, preserve a diversity of fishes and tetrapods in coastal marine to fluvial depositional environments, making this region ideal for investigating the ecology and evolution of Late Devonian vertebrates. A key unresolved issue has been reconstructing the specific aquatic habitats that hosted various vertebrates during this period. Specifically, the salinity of environments spanning fresh to shallow marine water is difficult to discern from sedimentological and paleontological analyses alone. Here, we analyze rare earth elements and yttrium (REY) as well as stable oxygen and sulfur isotope compositions (δ18O, δ34S) in fossil vertebrate bioapatite from late Famennian (ca. 362–360 Ma) strata of the Catskill and Lock Haven formations in the Appalachian Basin, USA, to determine the relative salinity of their aquatic environments. These results confirm the ecological euryhalinity of several taxa (Bothriolepis sp., tristichopterids, and Holoptychius sp.). Our results are the first demonstrating that some early tetrapod species occupied unequivocally freshwater habitats by late Famennian time (ca. 362–360 Ma). Our study shows that integrating sedimentological and paleontological data with combined oxygen and sulfur isotope analysis allows precise tracing of the relative salinity of vertebrate habitats deep in the past.
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RBINS Staff Publications 2024
