Wolfgang Weitschat

Organic components in phragmocones of boreal triassic ammonoids: Implications for ammonoid biology

KurzfassungAus der borealen Trias von Svalbard und NE-Sibirien werden Ammonoideen-Faunen beschrieben, bei denen die ursprünglich aragonitischen Schalenbestandteile früdiagenetisch in Apatit umgewandelt worden sind. Durch den Umstand, daß die Gehäuse später mit Kalzit ausgefüllt wurden, läßt sich der Kammerinhalt chemisch herauslösen. Damit wird eine außergewöhnliche räumliche Betrachtungsweise des Septenbaues und des Siphonal-Apparates ermöglicht. Das Besondere an diesem Ammonoideen-Material besteht jedoch darin, daß durch den frühen Zeitpunkt der Phosphatisierung auch ehemals organische Gehäusebestandteile in Apatit umgewandelt und damit erhalten geblieben sind. So zeigen fast alle untersuchten Gehäuse ehemals organische Membranen, die die Septen und die Gehäuseinnenwände auskleiden. Diese Membranen können mit dünnen Protein-Lagen im Phragmokon des rezentenNautilus homologisiert werden, die eine besondere Rolle beim Pumpvorgang spielen, wenn die Kammerflüssigkeit nicht mehr im direkten Kontakt mit dem Siphonairohr steht. In einer Anzahl von Exemplaren sind im Phragmokon phosphatisierte, flächenhaft ausgedehnte Lamellen erhalten, die in einem z.T. komplizierten System Teile des Kammerlumens von dem übrigen Raum abriegeln. Nach ihrer Form und Lage innerhalb der Kammer werden drei Typen unterschieden: 1. Siphonal-Lamellen, 2. Transversal-Lamellen, 3. Horizontal-Lamellen. Aus der Interpretation dieser lntrakameralen organischen Strukturen ergeben sich neue Erkenntnisse bezüglich der Funktions-Morphologie von Ammonoideen-Gehäusen besonders im Zusammenhang mit Schwimmfähigkeit, Lokomotion und Lebensweise. Die Beschreibungen ähnlicher Strukturen bei phosphatisierten Ammonoiden aus dem Perm und dem Volgium der UdSSR belegen, daß das Vorkommen derartiger Lamellen nicht auf triassische Arten beschränkt ist, sondern vielmehr ein allgemeines Phänomen darstellt, dessen Erhaltung jedoch besonderer Fossilisations-Bedingungen bedarf.AbstractExtraordinarily well-preserved ammonoids from the Boreal Triassic of Svalbard and NE-Siberia are described, in which the original aragonite of the shell had been replaced by apatite during very early stages of diagenesis. Because of subsequent calcite cementation of the phragmocones, it is possible to dissolve the chamber contents. This allows three-dimensional observations at different ontogenetic stages. The most remarkable features, however, are preserved organic sheets in the ammonoid phragmocones which are normally readily destroyed. Nearly all specimens examined show phosphatized membranes lining the septal surfaces and the inner shell wall. These membranes are most probably homologous to thin protein layers in the phragmocone of the recentNautilus, where they are termed the pellicle. They play an important part in the buoyancy control when the chamber liquid is no longer in direct contact with the siphuncular tube. In a number of specimens, a complicated system of formerly organic sheets which close off single compartments from the main chamber volume are preserved within the phragmocone. Depending on type and position of these layers in an ammonoid chamber, three different groups may be distinguished: 1. siphuncular sheets, 2. transverse sheets, and 3. horizontal sheets. The interpretation of the presence of these sheets leads to new conclusions concerning the functional morphology of the shell, especially related to questions of buoyancy, locomotion, and mode of life. Descriptions of similar structures within Permian goniatitids and Volgian ammonites indicate, that cameral sheets are not restricted to our Triassic species, but are a more general feature. They were probably present in most ammonoids, but have rarely been preserved.

Triassic transgressive-regressive cycles in the Sverdrup Basin, Svalbard and the Barents Shelf

Nine transgressive-regressive (T-R) cycles have recently been recognized in the Triassic succession of the Sverdrup Basin, Arctic Canada (Embry, 1988). The transgressions which initiated the cycles are dated as earliest Griesbachian, earliest Smithian, late Smithian, earliest Anisian, early Ladinian, earliest Carnian, mid-Carnian, earliest Norian, latest Norian and earliest Jurassic.

Biostratigraphy and sequence stratigraphy of the lower and middle Triassic deposits from the Svalis Dome, Central Barents Sea, Norway

Abstract Material from shallow cores drilled through the uplifted and truncated deposits near the Svalis Dome in the Barents Sea contains Lower and Middle Triassic palynomorphs and ammonoids. Eight miospore assemblage zones have been established in this paper, and six of them are calibrated by ammonoids: Svalis‐1 is dated by ammonoids of the late Griesbachian commune Zone. The assemblage is recovered from the Havert Formation overlying the Permian limestone. Svalis‐2 is dated by ammonoids to the late Smithian tardus Zone. The deposits belong to the lower and middle parts of Klappmyss Formation. The unit represents the transgressive systems tract of a Smithian‐early Spathian T‐R Sequence. Svalis‐3 is recorded from the youngest part of Klappmyss Formation which is missing age conclusive faunal evidence. The palynological assemblage is correlated as early Spathian in age. The deposits represent the regressive systems tract of the Smithian‐early Spathian T‐R Sequence. Svalis‐4 is recovered from rocks deposite...

Ostracoden (O. Myodocopida) mit Weichkörper-Erhaltung aus der Unter-Trias von Spitzbergen

A new myodocopid ostracode subfamily (Triadocypridininae) is described from the Lower Triassic (Spathian) from W-Spitsbergen. All of the 60 specimens obtained are complete carapaces. The original calcium carbonate and the chitin of the ostracodes are replaced by apatite resulting in some specimens in a preservation of the appendage structures in minute detail. Parts of the 1st and 2nd antenna, the 2nd maxilla and the 2nd thoracopode are well preserved. Some specimens show characteristic gill-like structures with three lobes sitting posterior on each side of the body. In one specimen the lateral eye is preserved. The fossilized appendage structures, described for the first time, are almost identical with those known from recent species of this family. The environment and the secondary phosphatization leading to this extraordinary preservation is discussed.KurzfassungAus der Unter-Trias (Spathian) von W. Spitzbergen wird eine neue Ostracoden-Sub-familie Triadocypridininae (O. Myodocopida) beschrieben. Sämtliche 60 vorliegenden Exemplare sind zweiklappig erhalten. Die ehemals aus Calciumkarbonat bestehende Schalensubstanz ist sekundär in Apatit umgewandelt. Bei einem Teil der Exemplare sind auch die chitinigen Weichkörper-Anhänge phosphatisiert und so z.T. hervorragend erhalten geblieben. Neben Teilen der ersten und zweiten Antenne konnten in vielen Fällen die Atemplatte der Maxille und der als Putzfuß umgebildete zweite Thorakopode nachgewiesen werden. Einige Exemplare zeigen charakteristische dreilappige Kiemenpaare, die beiderseits am Hinterende des Körpers ansetzen. Bei einer einzigen Form ist sogar das Lateralauge erhalten geblieben. Die hier erstmals fossil beschriebenen Weichkörper-Strukturen sind mit denen der rezenten Vertreter dieser Familie nahezu identisch. Die Fossilisationsbedingungen und die Phosphatisierung, die zu der außergewöhnlichen Erhaltung geführt haben, werden diskutiert.

An Early Eocene gecko from Baltic amber and its implications for the evolution of gecko adhesion

A new genus and species of gecko from the Lower Eocene of north-western Russia is described from a superbly preserved specimen in Baltic amber. It is the oldest gekkonid lizard to be represented by more than fragmentary skeletal remains. The digits of the specimen are mostly intact and reveal a unique combination of characters not seen in any living form. Expanded sub-digital scansors on the toes, however, are essentially similar to those of modern climbing geckos and verify the existence of a complex adhesive system 20–30 million years earlier than supported by previously discovered fossil geckos.

Zur Anatomie und Ökologie von Ammoniten: Funde von Kropf und Kiemen

ZusammenfassungWeichteilreste in Wohnkammern der AmmonitengattungenArnioceras, Hildoceras, «Oppelia» undPhysodoceras werden beschrieben. Dabei wird besonders auf den Kropfinhalt und daraus folgernd auf die Ernährungsweise der Ammoniten eingegangen. Die Analyse unserer Funde zeigt, daß Foraminiferen, Ostracoden, kleine Ammoniten und Seelilien gefressen wurden.Auf einen Fund von Ammoniten-Kiemen wird hingewiesen.AbstractSoft parts within the living chambers of specimens of the generaArnioceras, Hildoceras, «Oppelia», andPhysodoceras are described. Special attention is given to the contents of the crops and, in consequence, to the feeding habits of ammonites. Our analysis shows that foraminifera, ostracods, small ammonites, and crinoids have been eaten by ammonites.A find of ammonite gills is demonstrated.

Biomagnetostratigraphy of the Vikinghøgda Formation, Svalbard (Arctic Norway), and the geomagnetic polarity timescale for the Lower Triassic

A bio-magnetostratigraphy for the Lower Triassic is constructed, using the ammonoid biostratigraphy from arctic Boreal successions. Combined thermal and alternating field demagnetisation determines the Triassic magnetic field polarity in 86% of specimens, with 36% showing linear trajectory line-fits and the remainder great circle trends towards the characteristic magnetisation. Mean pole directions for the Deltadalen (=50°, φ=159°, dp/dm=3.9°/5.1°), Lusitaniadalen (=56°, φ=163°, dp/dm=4.4°/5.4°) and Vendomdalen (=57°, φ=143°, dp/dm=4.4°/5.4°) members fall close to the European Lower Triassic apparent polar wander path. Mean directions for two of these member-means pass the reversal test. The remanence is predominantly carried by magnetite. The polarity stratigraphy, when integrated with the ammonoid and meager conodont data is similar to that determined from successions in the Sverdrup Basin (Canada). The Permian-Triassic boundary post-dates a pronounced palynofloral turnover, and pre-dates a short duration reverse magnetozone (LT1n.1r). In the correlated Shangsi section (in S. China) LT1n.1r occurs after the FAD of H. parvus, but in the arctic is within the Otoceras boreale Zone. The late Griesbachian to early Smithian is mostly reverse polarity, with three normal polarity intervals, overlain by mid and late Smithian normal polarity. The Spathian contains four reverse polarity intervals, the oldest one within the early Spathian with the remainder in the late Spathian. Transition into the Anisian is within the uppermost reverse magnetozone, a feature documented in other sections of this age. The polarity pattern is correlated to other marine sections, indicating the robustness of the bio-magnetostratigraphic composite and its utility in calibrating Lower Triassic time.

A Review of the Order Mantophasmatodea (Insecta)

The newly discovered insect order Mantophasmatodea, known from two Recent species in tropical Africa and some fossils in Baltic amber, is reviewed, with all the material currently known being listed. A new genus and species is described: Praedatophasma maraisi Zompro & Adis, n. gen., n. sp. Complete information available at present on habitats and the biology is given.

Triassic conodonts from Svalbard and their Boreal correlations

Conodont faunas are described from Triassic sections of Svalbard, and their occurrences are locally correlated with established ammonoid zones. With a synthesis of previous conodont-based publications, the current work presents a taxonomically up-to-date compilation of conodont data for the Triassic of Svalbard that is used to construct a conodont-based biochronology, indexed to the current lithostratigraphic nomenclature. Twenty-eight taxa spanning the earliest Griesbachian to the earliest Carnian are presented in a range chart. The examined conodont faunas are correlated with well-established conodont zonations of the Canadian Arctic, and in turn also form the basis for regional correlations.

Magneto-biostratigraphy of the Middle to Upper Triassic transition, central Spitsbergen, arctic Norway

Palaeomagnetic and biostratigraphic data were obtained for the latest Ladinian and most of the Carnian (Botneheia Formation to basal Kapp Toscana Group), from two sections in central Spitsbergen (Svalbard archipelago). Thermal and alternating field (AF) demagnetization reveals a magnetization of both normal and reversed polarities. The mean directions pass reversal and fold tests and are similar to other European Late Triassic palaeopoles. One of the sections displays 15° of vertical-axis, clockwise, tectonic rotation on a décollement in the underlying Botneheia Formation. The magnetostratigraphy is dominated by normal polarity in the uppermost Botneheia Formation and into the Tschermakfjellet and basal De Geerdalen formations. A substantial hiatus characterizes the Ladinian–Carnian boundary in central Spitsbergen, so reverse magnetozones, identified in Tethyan sections near this boundary, are absent. Magnetostratigraphic correlation, along with palynostratigraphic constraints, indicates that most of the De Geerdalen Formation is Lower Carnian. The magnetostratigraphy and palynology indicates that the Isfjorden Member (upper unit of the De Geerdalen Formation) is probably mid-Carnian in age. Change in the lithological architecture in the Isfjorden Member, compared with the underlying parts of the De Geerdalen Fm, suggests a hiatus near the base of the member, which may represent a mid-Carnian unconformity, not previously recognized on Spitsbergen.