Fossil Record最新文献

Sauropod dinosaurs present exceptional challenges in understanding their biology because of their exceptional body size. One of these, life history, can be inferred from the histology of their bones. For this purpose, the diverse sauropod assemblage of the Upper Jurassic Tendaguru beds was sampled with a new coring method which provided unprecented access to and insights into sauropod bone histology.

Growth series of humeri and femora as well as long growth records from single bones suggest that all four sauropod taxa are characterized by continued growth after sexual maturity but that growth was determinate. Fibrolamellär bone is dominant in the samples, indicating that the bones of the Tendaguru sauropods grew at rates comparable to those of modern large mammals. The growth pattern of these sauropods thus combines typically reptilian traits with typically mammalian traits. In the details of their bone histology, the Tendaguru sauropod taxa show considerable variation which reflects life history. In addition, Barosaurus exhibits probable sexual dimorphism in bone histology.

Das Verständnis der Biologie der sauropoden Dinosaurier wird durch ihre enorme Körpergröße außerordentlich erschwert. Allerdings kann ein Aspekt, die Lebensgeschichte, anhand der Histologie ihrer Knochen untersucht werden. Zu diesem Zweck wurde die diverse Sauropoden-Vergesellschaftung der oberjurassischen Tendaguru-Schichten beprobt, und zwar mit einer neuartigen Kernbohrmethode, die einen herausragenden Zugang und Einblick in die Knochenhistologie der Sauropoden ermöglichte.

Wachstumsserien von Humeri und Femora sowie umfassende Überlieferungen des Wachstums von Individuen anhand einzelner Knochen machen es wahrscheinlich, daß alle vier Sauropoden-Taxa der Tendaguru-Schichten durch ein auch nach der Geschlechtsreife anhaltendes Wachstum gekennzeichnet waren. Allerdings ging das Wachstum nicht bis zum Tode des Tieres weiter, sondern kam bei einer etwas variablen Maximalgröße zum Stillstand.

Fibrolamellärer Knochen ist der vorherrschende Knochentyp in den Proben, was anzeigt, daß die Tendaguru-Sauropoden mit für Säugetieren typische Raten wuchsen. Die Tendaguru-Sauropoden kombinerten also ein für Reptilien typisches Muster des Wachstums, nämlich nach der Geschlechtsreife anhaltendes Wachstum, mit für Säuger typischen Raten des Wachstums. Die verschiedenen Sauropoden-Taxa zeigen erstaunliche Unterschiede in den Details ihrer Knochenhistologie, die Unterschiede in der Lebensgeschichte belegen. Bei Barosaurus scheint außerdem ein Geschlechtsdimorphismus in der Histologie der Langknochen vorzukommen.

The Early Ordovician successions of the southern Montagne Noire consist of a thick sequence of predominantly siliciclastic sediments of which the late Tremadocian St. Chinian Formation and the earliest Floian La Maurerie Formation contain a comparatively rich and abundant cephalopod association. The cephalopods of the St. Chinian and La Maurerie Formation are interpreted as generally authochthonous, representing a fauna which originally lived in the open water above the sediments or related to the sea bottom. The cephalopod associations of the St. Chinian and La Maurerie formations are similar to other contemporaneous assemblages known from higher palaeolatitudes and associated with deeper depositional settings. They are composed almost exclusively of longiconic orthocones, in this case predominantly of eothinoceratids and baltocerids. The occurrences of Annbactrocera, and Bactroceras in the St. Chinian Formation are at present the earliest unambiguous reports of the Orthocerida. The available data suggest an initial expansion of orthoceroid cephalopod faunas from open water habitats of high paleo-latitudes, and a subsequent expansion on the carbonate platforms during the Floian. The presence of the eothinoceratid Saloceras in abundance demonstrates the Gondwanan affinity of the assemblage whilst adding further support for the presence of a ‘Saloceras realm’ that may have extended along the margins of East and West Gondwana at least into intermediate latitudes. The following new taxa are proposed: Annbactroceras n. gen., Annbactroceras felinense n. sp., Cyclostomiceras thorali n. sp., Felinoceras n. gen., Felinoceras constrictum n. sp., Lobendoceras undulatum n. sp., Rioceratidae n. fam., Saloceras murvielense n. sp., Thoraloceras n. gen., Thoraloceras bactroceroides n. sp. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The Hirnantian Glisstjärn Formation (Normalograptus persculptus graptolite Biozone) is a succession of limestones and shales onlapping the Katian Boda Limestone in the Siljan District, Sweden. It contains a conspicuous, up to several decimeter thick bed densely packed with bipolarly oriented, orthoconic cephalopod conchs that can reach lengths of more than 120 cm. Conch fragmentation, bioereosion and the generally poor preservation of the conchs indicate time averaging and the conchs are tentatively interpreted as beached, and a result of winnowing. Ten nautiloid species were collected from the Glisstjärn Formation of which five are new: Dawsonoceras gregarium n. sp., Discoceras siljanense n. sp., Isorthoceras dalecarlense n. sp., Retizitteloceras rarum gen. et sp. n., and Transorthoceras osmundsbergense gen. et sp. n. The non-endemic taxa in most cases are known from elsewhere in Baltoscandia, except one species which is known from Siberia, and North America respectively. Proteocerid orthoceridans dominate the association, of which T. osmundsbergense is the predominant species. Oncocerids are diverse but together with tarphycerids very rare. Notable is the lack of many higher taxa, that are typical for other Late Ordovician shallow water depositional settings. Based on the taxonomical composition of the cephalopod mass occurrence it is interpreted as an indicator of eutrophication of the water masses in the area. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A morphometric analysis of the characteristic whorl cross-sections of 1,200 Jurassic ammonoid species from southern Germany enabled us to characterise their morphospace. The successive Jurassic ammonoid faunas of southern Germany show characteristic patterns in morphospace occupation. While Early and Middle Jurassic ammonoids occupy limited areas of the morphospace range, the Late Jurassic ammonoids cover the entire spectrum. The ammonoids are characterised by an overall increase of both taxonomic diversity and morphological disparity in the course of the Jurassic. Strong fluctuations occur until the middle Late Jurassic, followed by a diversity decrease in the early Kimmeridgian and a disparity reduction in the early Tithonian. While diversity and disparity show similar progression during most of the Early Jurassic, they diverge subsequently and show only poor correlation until the end of the Jurassic. Particularly in the Middle Jurassic diversity and sea level changes correlate strongly. Neither temporal patterns in diversity nor disparity support the hypothesis of a mass extinction event in the early Toarcian. Significant changes in diversity and disparity in the early Callovian support a putative migration event of Boreal ammonoids into the Tethyan realm. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The hypothesis that ocean acidification was a proximate trigger of the marine end-Triassic mass extinction rests on the assumption that taxa that strongly invest in the secretion of calcium-carbonate skeletons were significantly more affected by the crisis than other taxa. An argument against this hypothesis is the great extinction toll of radiolarians that has been reported from work on local sections. Radiolarians have siliceous tests and thus should be less affected by ocean acidification. We compiled taxonomically vetted occurrences of late Permian and Mesozoic radiolarians and analyzed extinction dynamics of radiolarian genera. Although extinction rates were high at the end of the Triassic, there is no evidence for a mass extinction in radiolarians but rather significantly higher background extinction in the Triassic than in the Jurassic. Although the causes for this decline in background extinction levels remain unclear, the lack of a major evolutionary response to the end-Triassic event, gives support for the hypothesis that ocean acidification was involved in the dramatic extinctions of many calcifying taxa. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The lack of a revision of the ostracodes described by Aurel Krause at the end of the 19th century from glacial erratic boulders from Berlin and the Mark Brandenburg (Northern Germany) has led to taxonomic confusion in the corresponding literature of the 20th century. To attain stability in names, some of Krause's ostracode species have been revised based on the types stored in the Museum für Naturkunde Berlin, namely Primitia plana, P. plana tuberculata, P. intermedia, P. globifera, Entomis sigma antiquata, Bollia v-scripta, B. granulosa, B. duplex, Strepula lineata, Isochilina canaliculata, Beyrichia dissecta, B. mamillosa, B. signata, and B. bidens. Most species have up to four younger synonyms among species described later from outcrops or borings in Baltoscandia or glacial erratic boulders of Northern Germany and Sweden. Three of Krause's species, which have been considered as nomina dubia by Jaanusson are in fact valid species. Some of Krause's species or of their synonyms are type species. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The fauna of the Middle Devonian Red Hill I locality, Nevada, is unusual in the co-occurrence of a rich fish assemblage with a rich invertebrate one. Sponges are second in abundance of specimens and number of species only to the fishes and occur together with other invertebrates (conodonts, conulariids, dacryoconarid tentaculites, gastropods, bivalves, brachiopods, arthropods, and unidentifiable ammonoids and echinoderms). The invertebrates indicate a marine depositional paleoenvironment. The conodonts indicate a placement within the lower disparalis Zone, late Givetian. The fish assemblage is dominated by the antiarch Asterolepis. All the other fishes, acanthodians, actinopterygians and sarcopterygians, are less common. The closest biogeographic relationship of the fish fauna is with the Middle/Late Devonian fish fauna of the Baltic Region, followed by that of eastern Canada (Miguasha), Scotland and Iran. This distribution corresponds to the Devonian Euramerica faunal province with connection to eastern Gondwana (Iran and Australia). Localities with the same genera as Red Hill I are interpreted as marine with the exception of the Scottish localities. Asterolepis is the most widely distributed vertebrate genus, mostly marine, but it may be able to enter freshwater like Eusthenopteron if one accepts a freshwater depositional paleoenvironment for the Scottish localities. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A dermal bone from the late Famennian of Ketleri in Latvia, identified as a probable tetrapod postorbital by Oleg Lebedev and stored in the Museum für Naturkunde Berlin, is described in detail. Its tetrapod status is confirmed based on the dermal sculpture consisting of polygonal pits and radially aligned ridges and furrows. The sculpture resembles that of Devonian tetrapods but is nevertheless not as regular as in most post-Devonian forms. The bone can be designated as a postorbital because of its concave anterior margin, the lateral line that shows no bifurcation, and the ossification centre that is located in the dorsal portion of the bone. The lateral line (i.e., the postorbital branch of the infraorbital line) forms an open, deep sulcus in the ventral portion of the postorbital but is enclosed within the bone in the dorsal portion and opens through pores to the surface. This morphology of the postorbital branch is unique among basal tetrapods. The bone might belong to the tetrapod Ventastega curonica Ahlberg et al., 1994 that is known from the same strata at Ketleri, however, since the postorbital is unknown in this taxon, this cannot be stated with certainty. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A small coelacanth specimen of Viséan age from a newly described locality near Rösenbeck at the northern margin of the Rhenish Mountains (North Rhine-Westphalia, Germany) is described. The head and pectoral girdle are not preserved, however, the specimen can be distinguished from all other known Carboniferous coelacanths by derived characters of the articulated postcranial skeleton. Derived characters include: (1) The slender first and second dorsal fins that carry only seven to eight and six fin rays, respectively. (2) Both the pelvic and anal fin have a broad base and are unusually weakly lobed. (3) The fin rays of the second dorsal fin are much more robust than those of the first dorsal fin. (4) The second dorsal and anal fins are longer than the first dorsal and pelvic fins. The Rösenbeck coelacanth is interpreted as a juvenile specimen, since the basal plates that support the fins are not ossified. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The Late Jurassic Bavarichthys incognitus, n. gen. n. sp. from Ettling, Bavaria, is described. The new species represents the oldest record of a crossognathiform in Europe and together with Chongichthys from the Oxfordian of South America stands at the basal levels of a clade including crossognathids and pachyrhizodontoids. In addition, the new fish represents the first record of a crossognathiform in the Solnhofen Limestones. The new genus is characterized by numerous features such as the presence of infraorbitals 1–3 independent and 4 + 5 fused; two supramaxillary bones present; supramaxilla 2 considerably shorter than supramaxilla 1 and lacking an antero-dorsal process; well-developed series of epineural, epicentral and epipleural intermuscular bones; parhypural and hypurals 1 and 2 partially fused to each other; a series of epaxial basal fulcra; and a few, elongate fringing fulcra associated with the dorsal leading margin of caudal fin. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)