Christian Meyer | Natural History Museum Basel (original) (raw)

Papers by Christian Meyer

Sedimentary geology, Jan 1, 2006

A new tracksite located in the Mesozoic autochthonous series covering the Aiguilles Rouges Massif... more A new tracksite located in the Mesozoic
autochthonous series covering the Aiguilles Rouges Massif,
circa 7 km to the NNE of the tracksite of the Vieux
Emosson, is briefly described. The trampled bed is most
likely coeval with the outcrop in the Vieux Emosson area.
Two poorly preserved quadrupedal trackways, almost
parallel, measure 9.8 and 8 m in length, respectively. They
are referred to the Chirotheriidae ABEL, 1835 form-family.
A short and well-preserved quadrupedal trackway,
composed of two manus-pes couples, is assigned to
Chirotherium cf. barthii KAUP, 1835. A reinterpretation of
the Vieux Emosson ichnotaxa reveals that most tracks, if
not all, belong to indeterminate chirotheriid and that no
clear evidence of dinosaur footprints is observed. The
trampled bed of the cover of the Aiguilles Rouges Massif
probably forms a megatracksite, which is Early or Middle
Triassic in age.

Based on an almost complete three-dimensionally preserved skeleton, a new genus and species of an... more Based on an almost complete three-dimensionally
preserved skeleton, a new genus and species of an
azhdarchoid pterosaur Aurorazhdarcho primordius n.gen.
n.sp. from the Late Jurassic Solnhofen limestone (Early
Tithonian) of the Eichsta¨tt area (Bavaria, Germany) is
described. Furthermore, a new family the Protazhdarchidae
is proposed. The specimen is attributed to the Azhdarchoidea
based on its glenoid fossa level with the sternum,
the shovel-like shape of the sternal plate, the wide furca of
the coracoid, the metacarpus being longer than radius and
ulna, the femur being 1/3 longer than the humerus, the
femorotibial ratio, and the hammer-shaped humerus among
other diagnostic features. Under UV-light, soft tissue
preservation around the external mould of the head is
visible. It consists of tiny flakes possibly remnants of skin.
The dorsally curved outline of the external mould of the
head suggests the presence of a cranial crest. The new
species is the oldest record of the azhdarchoid pterosaurs. It
supports the Eurasian origin of this group that includes the
largest flying animal ever.

Carapaces of marine turtles from the Late Jurassic Solothurn Turtle Limestone (Reuchenette Format... more Carapaces of marine turtles from the Late Jurassic Solothurn Turtle Limestone (Reuchenette Formation, Late Kimmeridgian) commonly yield rounded pits that may have resulted from epibi- onts or ectoparasites, although a conclusive interpretation has not yet been presented. Out of a large collection, only very few specimens of carapaces display areas that are more or less densely covered by stellate v-shaped grooves. These are attributed to the ichnotaxon Gnathichnus pentax BroMley and are interpreted as gnawing and rasping traces of the teeth of hemicidaroid sea ur- chins. The size of the traces suggests that Hemicidaris mitra (AgAssiz) which is a very frequent and autochthonous part of the fauna was the producer of these stellate grooves. The grazing traces suggest the presence of a post-mortem dense algal cover and indicate an extended exposure time of the carapaces at the sediment-water interface

Kauffmann, E. G., Harries, P. J., Meyer, Ch., Villamil, T., Arango, C. & Jaecks, G. 2007. Paleoecology of Giant Inoceramidae (Platyceramus) on a Santonian (Cretaceous) Seafloor in Colorado.

Giant Middle Coniacian to Lower Campanian Platyceramus Seitz is among the largest Cretaceous biva... more Giant Middle Coniacian to Lower Campanian Platyceramus Seitz is among the largest Cretaceous bivalves, commonly reaching an axial length of over 1 m, and occasionally over 2-3 m in size. The genus is characterized by its large size, very low convexity, normal inflation limited mostly to the umbonal area, and flattened flanks. It is especially common in moderately deep calcareous shale facies, as well as in chalks and limestones of the Niobrara Formation and equivalents. Preferred facies contain abundant pyrite, elevated total organic carbon (TOC), and very low biotic diversity. The genus maintains its giant size in these facies, and becomes more abundant. It clearly prefers dysoxic facies. As such, it probably is chemosymbiotic; photosymbiosis is almost ruled out because of inferred water depths of 200-350 m. It is also found more sparsely, and of smaller size, in oxygenated facies, including shoreface sandstone. The study area contains over 81 giant-sized Platyceramus platinus (Logan, 1898) on a single bedding plane; there are very few small ones. This allows spacing, orientation, and size analysis to be performed on an adult population.

A new ophiuroid species from the Hauptrogenstein Formation (Middle Juras- sic, Bajocian) of the R... more A new ophiuroid species from the Hauptrogenstein Formation (Middle Juras- sic, Bajocian) of the Rehhag ridge near Schöntal, northwestern Switzerland, is described based on 34 specimens. The impression of an indeterminate as- tropectinid sea star has also been found. The fully articulated specimens have been smothered by mobile oolitic dunes or sandwaves. The site can be geneti- cally classified as an obrution deposit and belongs to the widely recognized “Hauptrogenstein type”. The remains are assigned to the genus Geocoma D’ORBIGNY 1850, best known from the type species, G. carinata (MÜNSTER), from the Tithonian Plattenkalk of Zandt. As suggested by Kutscher (1997) this species also includes Ophiocten kelheimense BOEHM 1889, now documented by numerous well-preserved specimens from the Plattenkalk of Hienheim. Kutscher assigned the Hienheim specimens to the genus Sinosura HESS 1964 and used both names though G. carinata has priority. Despite rather small dif- ferences Sinosura is retained as a valid genus besides Geocoma, and both are placed in the family Aplocomidae HESS 1965. Geocoma and Sinosura share small adpressed arm spines with Aplocoma D’ORBIGNY 1852. Aplocoma is represented by a number of Triassic and Jurassic species, and the subfamily Aplocominae is proposed herein for the three genera. A second subfamily, Ophiopetrinae, is proposed for the genera Ophiopetra ENAY & HESS 1962 and Ophiohybris HESS 1964, and is characterized by larger, erect arm spines.

The pre-sacral vertebrae of most sauropod dinosaurs were surrounded by interconnected, air-filled... more The pre-sacral vertebrae of most sauropod dinosaurs were surrounded by interconnected, air-filled diverticula, penetrating into the bones and creating an intricate internal cavity system within the vertebrae. Computational finite-element models of two sauropod cervical vertebrae now demonstrate
the mechanical reason for vertebral pneumaticity. The analyses show that the structure of the cervical vertebrae leads to an even distribution of all occurring stress fields along the vertebrae, concentrated mainly on their external surface and the vertebral laminae. The regions between vertebral laminae and
the interior part of the vertebral body including thin bony struts and septa are mostly unloaded and pneumatic structures are positioned in these regions of minimal stress. The morphology of sauropod cervical vertebrae was influenced by strongly segmented axial neck muscles, which require only small attachment areas on each vertebra, and pneumatic epithelia that are able to resorb bone that is not mechanically
loaded. The interaction of these soft tissues with the bony tissue of the vertebrae produced lightweight, air-filled vertebrae in which most stresses were borne by the external cortical bone. Cervical pneumaticity was therefore an important prerequisite for neck enlargement in sauropods. Thus, we expect that vertebral pneumaticity in other parts of the body to have a similar role in enabling gigantism.

A crinoid Lagerstatte of Chariocrinus wuerttembergicus (Opalinuston Formation, Aalenian, Middle J... more A crinoid Lagerstatte of Chariocrinus wuerttembergicus
(Opalinuston Formation, Aalenian, Middle Jurassic) was
formed under storm conditions. The Lagersta¨ tte is oriented
parallel to paleowave crests, and exhumed concretions indicate
sediment reworking. Paleoflowwas nearly perpendicular
to (storm-) wave ripple-crests and was directed towards
a depocenter to the south-southeast. Both waves and
currents affected crinoid parts, such as stems, and document
combined flow conditions. The crinoids lived on a lowrelief
swell somewhat above stormwave base in amuddy environment,
and caused their own in-situ burial. During a
storm, wave agitation led to suspension of sediments extending
into the habitat of the crinoids. The crinoids provided
additional friction within the near-bottom, suspension-
rich, agitated water body, thereby reducing the speed of
water currents. This led to sediment deposition, and the crinoids
were buried in fine-grained sand and silt. In thisway,
they induced their own burial; therefore, the Lagersta¨ tte is
the product of a feedback process. Rapid burial of the crinoids
led to their excellent preservation. Articulated preservation
is possible only if the flow was too slow to remove the
crinoids from their substrate. Some crinoids tried to escape
these hostile conditions by autotomizing their crowns, but
these were pushed down to the seafloor by oscillatory water
movement, and were immediately covered, mouth upward,
by sediments. The preserved crowns provide an estimate of
the population density in the range of 110 animals m22,
which is a minimumvalue because some crowns might have
been washed away before burial.

In Late Jurassic times, the Swiss Jura carbonate platform occupied the transition between the Par... more In Late Jurassic times, the Swiss Jura carbonate
platform occupied the transition between the Paris Basin
and the Tethys and thus connects the Boreal and Tethyan
realm. Up to now, the lack of index fossils in the Reuchenette
Formation prevented a reliable correlation between
both areas (its sediments are characterised by a prominent
sparseness of index fossils). Now, seven recently in situ
collected species of ammonites helped to establish a new
sequence-stratigraphical frame for the platform sediments
of the Reuchenette Formation in NW Switzerland. Based
on biostratigraphical data, five third-order sedimentary
sequences were assigned to the Late Oxfordian to Late
Kimmeridgian. The upper three third-order sequences
correspond to the Boreal sequences Kim3–5 of Hardenbol
et al. (1998). The deduced large-scale sea-level fluctuations
match those from other European regions (Spain, Russia).
This biostratigraphically based sequence-stratigraphical
frame is a prerequisite to refine correlations within a wider
area covering the Swiss Jura and parts of adjacent France
and Germany.

Geological sections of the shallow-water, carbonate-dominated sedimentary system of the Late Jura... more Geological sections of the shallow-water, carbonate-dominated sedimentary system of the Late Jurassic Reuchenette Formation in northwestern Switzerland have been studied between the southern Jura Mountains and the Tabular Jura. The largest sections show a characteristic cyclic stacking pattern. Up to now, the age of these sediments (including the type-section) linking the Boreal and Tethyan realms, was biostratigraphically poorly constrained. In the Tabular Jura five 3rd order sequences can be assigned to the Planula- to Eudoxus-Zone (Late Oxfordian to Late Kimmeridgian) using index-fossils (ammonites and ostracodes; This time control and several new outcrops, in combination with mineralostratigraphical and lithological marker beds, allow the correlation and dating of the thickest sections of the Reuchenette Formation and thus serve to improve the previously estimated ages of their sequence boundaries.
The variability of stacking pattern and facies between sections also reveals distinctive changes in facies evolution, related to
Late Palaeozoic basement structures and synsedimentary subsidence. These structures acted as important controlling factors for the sediment distribution of the Reuchenette Formation besides the sea level fluctuations. The interplay of sea level changes and synsedimentary subsidence is outlined by lateral thickness variations and shifting depositional environments.
A close examination of these changes also sheds much light on the nature of platform topography in the transition area between
the Paris Basin in the north and the Tethys in the south, or more generally between the Boreal and Tethyan realms. During the
Planula- to Divisum-time-intervals the study area was a flat platform with a more or less uniform facies distribution, which
connected the above-mentioned realms. During the Divisum-to Acanthicum-time-intervals this platform changed into a pronounced basin-and-swell morpoholgy, with specific depositional environments and separated the Paris Basin from the Tethys.

The Faciès Rognacien is a sequence of highly bioturbated and pedogenically modified palustrine ca... more The Faciès Rognacien is a sequence of highly bioturbated and pedogenically modified palustrine carbonates that were deposited under oxic conditions around the
Cretaceous-Tertiary (K-T) boundary in the northeastern Pyrenean foreland basin (SW France). The sedimentary structures and early diagenetic features identified
(mottling, nodule formation, brecciation, pseudomicrokarst, cracking, charophytes, Microcodium) suggest deposition in a palustrine environment between the subarid
and intermediate climate type. Sedimentological and paleoecological analysis enables us to distinguish two facies associations, the lacustrine pond facies and the freshwater
marsh facies associations. The majority of the carbonates are attributed to the freshwater marsh facies. The lacustrine pond facies occurs only in isolated paleolows, and is identified on the basis of its paleobiological content (charophytes, ostracodes).
This suggests that the palustrine carbonates of the Faciès Rognacien were deposited in a seasonal wetland (carbonate-producing freshwater marsh), rather than in the marginal zone of a large, shallow lake. In this wetland paleoenvironment, all carbonates underwent widespread pedogenesis, and small, ephemeral ponds are of limited distribution, most likely recording deposition in paleolows.

The first discovery of dinosaur footprints on the Dalmatian part of the Adriatic-Dinaric carbonat... more The first discovery of dinosaur footprints on the Dalmatian part of the Adriatic-Dinaric carbonate platform (ADCP) is reported. They constitute
the geologically youngest record of footprints on the ADCP. The trackbearing layer was formed in the intertidal environment and represents
the final stage of a shallowing-upward cycle. Just below it, a heavy dinoturbated limestone layer can be observed. Microfacies analysis,
incorporating evidence from benthic foraminifera and algae, indicates a Late TuronianeEarly Coniacian age. The overall morphology and size
of the footprints points to sauropod dinosaurs; they represent the largest forms recorded so far on the ADCP. This hints at a prolonged sauropod
presence on the platform and to its Late Cretaceous connection to the continent rather than isolation.

In 2003 vertebrate tracks attributed to pterosaur, crocodiles, turtles, hadrosaurs and sauropods ... more In 2003 vertebrate tracks attributed to pterosaur, crocodiles, turtles, hadrosaurs and sauropods have been reported from a locality close to Sabinas (Coahuila) in the Sierra Madre Oriental (Maastrichtian). Three trackways of medium-sized theropods could be observed. Evenly spaced parallel scratches forming a trackway might have been left by a swimming pterosaur. Furthermore a clear tetradactyl imprint, with claw marks only
can be temptatively assigned to a pterosaur. So far, we have observed tracks of theropods only and probable prints of pterosaurs. The purported turtle tracks are small paired and tripled very faint scratches that have been produced by a xiphosuran arthropod. These are the first limulid tracks from Mexico. Another locality, Santa Helena, close to the village of Melchior Musquiz (Campanian) yields several surfaces with dinosaur fooprints.
The best preserved trackway is attributed to a large theropod.

Until now dinosaur tracks from Switzerland were only known from Triassic and Late Jurassic strata... more Until now dinosaur tracks from Switzerland were only known
from Triassic and Late Jurassic strata. We report here for the first
time the occurrence of ornithopod tracks from the Schrattenkalk
Formation (Late Aptian) from the Swiss Central Alps. The locality
is situated in an abandoned quarry on the shore of Lake
Lucerne close to the village of Beckenried.
The steeply inclined surface has more than 50 tracks ( in three
trackways) of ornithopod dinosaurs that are attributed to iguanodontids.
Three trackways can be followed for distances of 25 to
35 m. The lengths of the footprints (mean: 30 cm) point to animals
ranging in size of from 4 to 6 m, with estimated hip heights between
1.8 and 2 m (hip height 6 FL) and 1.4 to 1.7 m (hip height 5
FL). One of the trackways shows two succesive manus impressions,
indicating facultative quadrupedal gait.
The track bearing layer consists of shallow water micrites with
traces of emersion, and it is overlain by bioclastic grainstones.
Previously the Upper Schrattenkalk Member in the Helvetic
realm was thought to have formed on a large shelf far away from
any continents. The present discovery will shed new light on the
paleogeographic position of the Helvetic nappes.

Until 1960, the record of dinosaurs was rather poor in Switzerland. Between 1960 and 1980, severa... more Until 1960, the record of dinosaurs was rather poor in Switzerland. Between 1960 and 1980, several new localities with plateosaurid remains as well as prosauropod and theropod tracks were found in Late Triassic sabkha and floodplain environments.
The discovery of large surfaces with sauropod tracks in the Late Jurassic of the Jura Mountains in 1987 triggered a stream
of new data. More than 20 new localities with tracks from both sauropod and theropod dinosaurs in different stratigraphic levels
have been found since then. The latest discoveries include trackways of iguanodontids from the Early Cretaceous of the central Swiss Alps and a large Late Jurassic surface with trackways of small sauropods in the northernmost part of the Jura Mountains. The best skeletal record comes from the Late Triassic, with scattered data from the Late Jurassic. The track and trackway record appears to be best in the Late Jurassic.

Depth reconstruction based on the extrapolation to fossil assemblages of present-day depth ranges... more Depth reconstruction based on the extrapolation to fossil assemblages of present-day depth ranges of closely related groups is one of the most widely used approaches in palaeobathymetry. Here, we assess the ophiuroid fauna of the Bajocian to Bathonian (Middle Jurassic) Hauptrogenstein Formation and coeval formations in Switzerland with respect to the depth ranges of extant members of the groups identified. In addition to previously known taxa, we describe three new species, one assignable to the extant genus Ophiotholia within the family Ophiomycetidae (resurrected herein), and two belonging to new genera within the family Ophiacanthidae. The Hauptrogenstein ophiuroid fauna is shown to display a striking similarity to modern bathyal brittle star assemblages. In combination with taphonomic evidence of the autochthonous nature of the ophiuroid occurrences, the direct extrapolation of present-day depth ranges, as performed in various previous studies, would imply the Hauptrogenstein Formation to have been deposited in a bathyal setting. This, however, is in stark contrast with the generally accepted, sedimentology-based concept of this unit as a very shallow, highenergy carbonate platform deposit. Evidently, direct extrapolation of modern depth distribution patterns fails to provide a reliable palaeobathymetrical assessment here. In this respect, the case of the Hauptrogenstein ophiuroid fauna serves as a remarkable example to stress the pitfalls of assemblage-based palaeodepth estimates: (1) depth distribution patterns might not be controlled by water depth, or not even by a factor directly related to depth, (2) habitat preferences of a group might have changed through time without being reflected by morphological modifications and (3) shifts in depth ranges might occur due to the rise or extinction of groups interacting with the organism in question. Thus, extrapolation of present-day depth ranges to ancient communities can only produce reliable palaeodepth estimates if there is a mechanistic explanation why organisms are confined to a particular depth.

Sedimentary geology, Jan 1, 2006

Kauffmann, E. G., Harries, P. J., Meyer, Ch., Villamil, T., Arango, C. & Jaecks, G. 2007. Paleoecology of Giant Inoceramidae (Platyceramus) on a Santonian (Cretaceous) Seafloor in Colorado.