Co-occurrence of Neusticosaurus edwardsii and N. peyeri (Reptilia) in the Lower Meride Limestone (Middle Triassic, Monte San Giorgio)
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Citations
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Integrated Ladinian bio-chronostratigraphy and geochrononology of Monte San Giorgio (Southern Alps, Switzerland)
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Palaeoenvironmental significance of organic facies and stable isotope signatures: the Ladinian San Giorgio Dolomite and Meride Limestone of Monte San Giorgio (Switzerland, WHL UNESCO)
A new basal actinopterygian fish from the Late Ladinian of Monte San Giorgio (Canton Ticino, Switzerland)
References
Facies, depositional environment, and palaeoecology of the Middle Triassic Cassina beds (Meride Limestone, Monte San Giorgio, Switzerland)
The Miocene Petroleum System of the Northern Apennines in the Central Po Plain (Italy)
U-Pb zircon age of volcaniclastic layers in Middle Triassic platform carbonates of the Austroalpine Silvretta nappe (Switzerland)
Shape disassociation and inferred heterochrony in a clade of pachypleurosaurs (Reptilia, Sauropterygia)
Die Prosanto-Formation―eine fischreiche Fossil-Lagerstätte in der Mitteltrias der Silvretta-Decke (Konton Graubünden, Schweiz)
Related Papers (5)
Facies, depositional environment, and palaeoecology of the Middle Triassic Cassina beds (Meride Limestone, Monte San Giorgio, Switzerland)
Frequently Asked Questions (15)
Q2. How many pairs of caudal ribs can be observed?
Five pairs of caudal ribs can be observed, slightly displaced from their corresponding vertebrae; they show a tapering distal end and their size decreases abruptly after the fourth one.
Q3. What is the composition of the upper meride limestone?
The overlying Upper Meride Limestone is made up of alternating wellbedded limestones and marlstones with an increasing clay content towards the top, where strong seasonal variations of salinity and water level together with the influence from a neighbouring emerged area are documented.
Q4. What is the lateral view of the chevrons of the third to the seventh cau?
The chevrons of the third to the seventh/eighth caudal vertebrae are preserved; they are small elements, showing the distally expanded shape and rounded ventral margin which is typical of neusticosaurs.
Q5. What is the first diversification of pachypleurosaurids in the western?
The first diversification of pachypleurosaurids in the western Tethyan realm followed the marine transgression that began in the late Early Triassic and proceeded from east to west across central Europe.
Q6. What is the morphological character of the wedge-shaped skull?
The wedge-shaped skull with a waisted postorbitalregion which is shorter and wider than the antorbital region rules out N. pusillus, which has a narrow skull table with parallel margins (Carroll and Gaskill 1985; Sander 1989; Rieppel and Lin 1995; Rieppel 2000).
Q7. What is the lateral view of the first 10 caudal vertebrae?
The first 10 caudal vertebrae are also preserved in lateral view (Fig. 7); they show the rib articulations shifting gradually from the neural arch to the centrum, so that, from the fifth caudal vertebra on, the transverse process lies on the centrum only.
Q8. What is the articular surface of the first 10 caudal vertebrae?
They are short, stout and straight, converging on one point to meet the ilium, where they form a well-developed articular surface.
Q9. What is the significance of the co-occurrence of N. peyeri and N. ?
The co-occurence of N. peyeri and N. edwardsii in the same levels implies that the two species indicate possible adaptations toward different size- and/or trophic-related niches rather than representing an anagenetic lineage.
Q10. What is the morphological character of the third carpal in N. edward?
the third carpal in N. edwardsii is a tiny element so that its absence in MCSN 8076 could be due to either a preservation bias or a lack of ossification in case of its being a juvenile specimen.
Q11. What is the earliest known date of the Cassina beds?
The Cassina beds are traditionally regarded as early Ladinian in age (e.g. Hellmann and Lippolt 1981; O’Keefe et al. 1999) but reliable index fossils such as ammonoids and conodonts have never been reported from this horizon.
Q12. What is the palatine shape of the skull?
The palatines are thin and wide, and close the palate completely; they cover the bones of the skull roof, precluding the description of the latter.
Q13. what is the femur/standard length ratio of n. edward?
The femur/standard length ratio of MCSN 8076 is 1.01, well within the range of N. peyeri (0.78–1.06), while the range for N. edwardsii extends from 0.65 to 0.96, averaging 0.73 in juvenile specimens (specimen 3447 in Carroll and Gaskill 1985), therefore indicating a distinctly shorter femur than in MCSN 8076.
Q14. What is the bulk of Neusticosaurus material from the Cassina beds?
According to their examination of the historical collection stored at the Paläontologisches Institut und Museum der Universität Zürich (PIMUZ) and to unpublished field data (both courtesy Heinz Furrer, PIMUZ), the bulk of Neusticosaurus material from the Cassina beds comes from just the base of the sequence, which lies approximately 2 m below the bed bearing the specimen described here.
Q15. What is the preservation pattern of the Neusticosaurus specimen?
This preservation pattern is ascribed to the development of decay gas in the wide abdominal cavity which held the body with the ventral side upward (Furrer 2003).