An ammonoid fossil, especially one of a later type found chiefly in the Jurassic and Cretaceous periods, typically with intricately frilled suture lines.
Typified by ammonoids of the order Ammonitida‘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.’
Mid 18th century from modern Latin ammonites, from medieval Latin cornu Ammonis ‘horn of Ammon’, from the fossil's resemblance to the ram's horn associated with Jupiter Ammon (see ammoniacal).