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- Argonauta shares other characteristics with some Jurassic and Cretaceous ammonites, namely multicuspid rachidial tooth on the radula.
- The fossil content consists of ammonites, belemnites, brachiopods, echinoderms, bivalves, crinoids, gastropods, ostracodes and benthic foraminifers.
- A feature of especial interest is that, while the youngest Triassic ammonites are quite rare, the oldest Jurassic ammonites are extremely abundant, entering the succession in a veritable flood.
- This increase in disparity also corresponded to a phyletic radiation, as all the earliest Jurassic ammonites derived from scarce ammonites of rather homogeneous and medium-sized species.
- In eastern Mongolia late Permian marine sediments with brachiopods, crinoids and Bryozoa and Triassic marine sediments with ammonites occur in the suture zone, indicating that marine conditions existed during these times.
- The egg case secreted by the Cenozoic argonautids was shaped like Cretaceous ammonites, which their ancestors used to occupy and emend.
- Among the Middle Jurassic ammonites, they may be one of the more polymorphic groups: a feature which has made them a particularly useful subject for quantitative and biostatistical approaches.
- When the tests for dimorphism are now applied to these adults, it is clear that they are in fact dimorphic in just the same manner as other Jurassic ammonites.
- The children have dug up fossils of ammonites from millions of years ago.
- We love it there because rather than having just a sandy beach, there are loads of rocks and rock pools to explore and as the program showed last night, the place is abundant with fossils, especially ammonites.