Heinz Furrer

Palaeoenvironmental interpretation of a Triassic-Jurassic boundary section from Western Austria based on palaeoecological and geochemical data

A section spanning the Triassic-Jurassic boundary is described from near the village of Loruns in the Vorarlberg region of western Austria. At Loruns, the uppermost Triassic is characterised by bedded carbonates of the Kossen Formation supporting a stenotopic fauna indicative of a shallow sub-tidal environment of normal marine salinity. The Triassic-Jurassic boundary may be represented as a sequence boundary developed on top of a 1.1 m thick red mudstone of the lower Schattwald Shale, which is interpreted to have been deposited in a marginal marine environment, possibly a mud flat. Above the boundary beds, the upper Schattwald Shale is characterised by thin-bedded marl and dark limestone beds with an earliest Hettangian macrofauna dominated by epifaunal filter-feeding bivalves, including ostreids, mytilids and oxytomids, which suggest a shallow, subtidal, salinity-controlled environment typical of an interplatform lagoon. Carbonate production rejuvenated in the later Early Hettangian with development of the Loruns oolite, a shallow subtidal oolitic and oncolitic unit bearing echinoderms indicative of normal marine conditions. Low ThU ratios from the remainder of the section are a result of reduced thorium in carbonate-rich sediments and not from authigenic uranium in anoxic sediments. In the boundary beds evidence for marine anoxia (or dysoxia) is absent where ThU values, determined by gamma-ray spectrometry, are above 5. The negative excursion in δ13C and positive excursion in δ18O in the boundary beds may be due to secondary geochemical effects, due to organic diagenesis or the precipitation of caliche during paleosol development. Alternatively, the excursions may reflect a primary geochemical signal recording short-term decline in primary productivity. Comparison in δ18O and δ13C values between the Kossen Formation and Lorfus oolite indicate no significant long-term geochemical changes are evident in the section and suggest that any environmental perturbations were restricted to the boundary beds and possible sequence boundary.

Float or sink: modelling the taphonomic pathway of marine crocodiles (Mesoeucrocodylia, Thalattosuchia) during the death–burial interval

A taphonomic model is erected for a dataset of 19 Steneosaurus (Mesoeucrocodylia; Thalattosuchia) from the Toarcian Posidonienschiefer Formation (Lower Jurassic) of Germany. These were deposited in a quiet-water, marine, basin. Their taphonomy is compared with that of an additional seven thalattosuchians from other Jurassic localities (Peterborough and Yorkshire, UK; Nusplingen, Germany). The skeletal taphonomy of the specimens is assessed in terms of the articulation and completeness of nine skeletal units. Steneosaurus from the Posidonienschiefer Formation exhibit variable levels of articulation in the nine units. Completeness also varies but the head, neck and dorsal units are complete in all specimens. Carcasses reached the sediment–water interface shortly after death. Loss of fidelity occurred primarily as individuals lay on the sediment, and disarticulated elements tended to remain in the vicinity of the carcass. Those elements absent from specimens are the smaller, more distal, bones of the limbs and tail; these were removed preferentially by weak bottom currents. Smaller specimens are consistently less complete. Specimens from other localities broadly follow the same taphonomic pathway, suggesting a consistent pattern for the skeletal taphonomy of the carcasses of marine crocodiles. Loss of completeness in some specimens is more exacerbated, the result of stronger current activity at the sediment–water interface.

Dating Bones near the Limit of the Radiocarbon Dating Method: Study Case Mammoth from Niederweningen, ZH Switzerland

Preparation of bone material for radiocarbon dating is still a subject of investigation. In the past, the most problematic ages appeared to be the very old bones, i.e. those with ages close to the limit of the dating method. Development of preparative methods requires sufficient amounts of bone material as well as the possibility of verification of the ages. In the peat section at Niederweningen, ZH Switzerland, numerous bones of mammoth and other animals were found in the late 19th century. The first accelerator mass spectrometry (AMS) radiocarbon ages of those bones from 1890/1891 excavations placed the age between 33,000 and 35,000 BP. The excavations in 2003/2004 provided additional material for 14C dating. An age of 45,870 ± 1080 BP was obtained on base (NaOH step) cleaned gelatin from mammoth bone, which was very close to the age of 45,430 ± 1020 BP obtained for the peat layer that buried the mammoths. The 14C age of gelatin cleaned using the ultrafiltration method obtained in this study, 45,720 ± 710 BP, is in a very good agreement with the previously obtained results. Moreover, the study shows that 3 pretreatment methods (base+Longin, Longin+ultrafiltration, and base+Longin+ultrafiltration) give ages consistent with each other and with the age of the peat section.

Exceptional preservation reveals gastrointestinal anatomy and evolution in early actinopterygian fishes

Current knowledge about the evolutionary morphology of the vertebrate gastrointestinal tract (GIT) is hindered by the low preservation potential of soft tissues in fossils. Exceptionally preserved cololites of individual †Saurichthys from the Middle Triassic of Switzerland provide unique insights into the evolutionary morphology of the GIT. The GIT of †Saurichthys differed from that of other early actinopterygians, and was convergent to that of some living sharks and rays, in exhibiting up to 30 turns of the spiral valve. Dissections and literature review demonstrate the phylogenetic diversity of GIT features and signs of biological factors that influence its morphology. A phylogenetically informed analysis of a dataset containing 134 taxa suggests that body size and phylogeny are important factors affecting the spiral valve turn counts. The high number of turns in the spiral valve of †Saurichthys and some recent sharks and rays reflect both energetically demanding lifestyles and the evolutionary histories of the groups.

Exceptional fossil preservation demonstrates a new mode of axial skeleton elongation in early ray-finned fishes

Elongate body plans have evolved independently multiple times in vertebrates, and involve either an increase in the number or in the length of the vertebrae. Here, we describe a new mechanism of body elongation in saurichthyids, an extinct group of elongate early ray-finned fishes. The rare preservation of soft tissue in a specimen of Saurichthys curionii from the Middle Triassic (Ladinian) of Switzerland provides significant new information on the relationship between the musculature and the skeleton. This new fossil material shows that elongation in these fishes results from doubling the number of neural arch-like elements per myomeric segment. This unique way of generating an elongate body plan demonstrates the evolutionary lability of the vertebral column in non-teleostean fishes. The shape and arrangement of preserved myosepta suggest that S. curionii was not a highly flexible fish, in spite of the increase in the number of neural arch-like elements.

New coelacanth material from the Middle Triassic of eastern Switzerland, and comments on the taxic diversity of actinistans

New coelacanth material from the Middle Triassic Prosanto Formation of the Ducan and Landwasser area near Davos in eastern Switzerland, Canton Graubünden, is described. A sub-complete individual is visible in ventral view, and shows details of its branchial apparatus. In particular, it possesses relatively large teeth on the ceratobranchials, and possible ossified hypobranchials. Few diagnostic characters are observable, and most of them are visible on the mandibles preserved in lateral view. This specimen shares characters with Ticinepomis peyeri, a smaller form from the Middle Triassic of Monte San Giorgio, whose holotype is re-described in part here. A second specimen, a fragmentary caudal skeleton shows the typical supplementary lobe of coelacanths, and meristic characters indicating probable close affinities with T. peyeri. We refer this material to Ticinepomis cf. T. peyeri. Because the new specimen is larger than the holotype, we refute the possible juvenile status of the small specimen from Monte San Giorgio. The new material of Ticinepomis from Canton Graubünden shows anatomical features not preserved on the holotype and allows the addition of new characters to a previously published data matrix of actinistians. A phylogenetic analysis is performed, which supports that Ticinepomis is nested among the Latimeriidae. The diversity of post-Palaeozoic coelacanths is assessed. The taxic diversity of observed occurrences shows a peak in the Early Triassic and a peak in the Late Jurassic, as detected in previous studies. When ghost lineages are included in the computation, the Late Jurassic peak is smoothened. By comparing the taxic diversity curves with the curve of average ghost lineage duration, we conclude that the Early Triassic peak of diversity was probably caused by a biological radiation, whereas the Late Jurassic peak of observed diversity is probably the result of a Lagerstätten effect.

Taphonomic analysis of Saurichthys from two stratigraphic horizons in the Middle Triassic of Monte San Giorgio, Switzerland

Excavations of Middle Triassic strata at Monte San Giorgio (Switzerland–Italy) have famously recovered a range of reptiles whose affinities, morphology and preservation have been extensively described. The locality has also yielded a contemporaneous and equally diverse fish fauna that has yet to be described to the same degree. To address this imbalance, a taphonomic study was undertaken using the actinopterygian Saurichthys, a relatively abundant taxon found in the Besano Formation (latest Anisian–earliest Ladinian) and Cassina Beds of the Meride Formation (early Ladinian). Specimens from each horizon were scored for articulation and completeness across ten anatomical units, the resulting datasets being used to determine a taphonomic model and investigate preservational variation through time. Saurichthys showing moderate to high articulation and high completeness occur in both horizons but states of low articulation and moderate completeness are only present in the Besano Formation. The same feature is apparent in corresponding unit plots, suggesting different environmental conditions were present during deposition of each horizon, specifically those that reduced articulation and completeness during a prolonged residence on the sediment surface.

New holostean fishes (Actinopterygii: Neopterygii) from the Middle Triassic of the Monte San Giorgio (Canton Ticino, Switzerland)

The new neopterygian genus Ticinolepis, including two new species T. longaeva and T. crassidens is described from Middle Triassic carbonate platform deposits of the Monte San Giorgio. The anatomy of this fish shows a mosaic of halecomorph and ginglymodian characters and, thus, the new taxon probably represents a basal holostean. During the latest Anisian to earliest Ladinian the two new species coexisted in the intraplatform basin represented by the uppermost Besano Formation, but only T. longaeva sp. nov. inhabited the more restricted basin represented by the Ladinian Meride Limestone (except for the Kalkschieferzone). The more widely distributed type species shows interesting patterns of intraspecific variation including ontogenetic changes and morphological variation over time. The second species presents anatomical features that strongly indicate a strictly durophagous diet. The different distribution of the species is interpreted as a result of habitat partitioning and different adaptability to palaeoenvironmental changes.

The Triassic–Jurassic boundary in the shallow-water marine carbonates from the western Northern Calcareous Alps (Austria)

The Triassic–Jurassic (T–J) boundary coincides with one of the five biggest mass extinctions in the Phanerozoic. This event has been extensively studied in the eastern and central Northern Calcareous Alps (NCA), where the global stratotype section and point for the base of the Jurassic is outcropping. We present one of the first combined bio-, litho- and carbonate carbon isotope stratigraphic study across the T–J boundary from the western NCA, focusing on the shallow-water marine carbonate successions “Lorüns” and “Steinernes Meer”. An almost complete T–J succession with the Upper Triassic Kössen Formation, the T–J Schattwald beds and the Lower Jurassic Lorüns oolite is preserved in the Lorüns section, whereas a stratigraphic hiatus at the T–J boundary is observed in the Steinernes Meer section. The carbonate carbon isotope record of Lorüns shows the characteristic T–J carbon isotope evolution with a short initial negative carbon isotope excursion (CIE) in the lower Schattwald beds, which is separated from the following and longer main negative CIE in the Lorüns oolite by a positive excursion in the upper Schattwald beds. The synchroneity of the initial and main CIE with the last occurrence of Triassic fauna and the first appearance of Jurassic ammonites suggests placing the T–J boundary at the base of the Lorüns oolite. The Steinernes Meer section records only the main negative CIE in the Lorüns oolite due to emersion and/or no sedimentation between the Upper Triassic Kössen Formation and the Lower Jurassic Lorüns oolite, caused by regression and synsedimentary tectonics. This study provides new evidence in support the hypothesis that the latest Rhaetian decrease and the Hettangian recovery of the carbonate production coinciding with the initial and main CIE, respectively, can be interpreted as evidence of acidification of the Tethys ocean due to elevated atmospheric CO2 concentrations, probably caused by voluminous volcanic gas emissions.

A new species of Macrocnemus from the Middle Triassic of the eastern Swiss Alps

A new species of Macrocnemus is described on the basis of two incomplete specimens from the Lower Ladinian Prosanto Formation of southeastern Switzerland. The new form can be distinguished by its gracile limb elements and having a noticeably longer tibia than either Macrocnemus bassanii or Macrocnemus fuyuanensis. One of the new specimens exhibits soft part preservation in the region of the pelvic girdle. The hind part of this individual is preserved fully articulated and allows a complete count of the caudal vertebrae to be made for the first time with 52 caudals. It is postulated that this specimen was predated upon and that the anterior part of the animal was consumed by a large predator such as a nothosaurid reptile or the actinopterygian fish Saurichthys.