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The topology of the septa, especially around the rim, results in the various suture patterns found. [5] The septal curvature in nautiloids and ammonoids also differ in that the septa curves towards the opening in nautiloids, and away from the opening in ammоnoids. [6] Regions of the suture line and variants in suture patterns Ammonite clean cut
This ammonite has a ceratitic suture pattern on its shell (smooth lobes and frilly saddles). Evolution of the frilly saddles is thought to be due to increased pressure on the shell, at greater depth. The frilly pattern would increase the strength of the shell and allow Ceratites to dive deeper, possibly in search of food. [citation needed]
Ceratitida is an order that contains almost all ammonoid cephalopod genera from the Triassic as well as ancestral forms from the Upper Permian, the exception being the phylloceratids which gave rise to the great diversity of post-Triassic ammonites.
The sutures of nautiloids are by comparison somewhat simpler, being either straight or slightly curved, whereas later ammonoids showed suture patterns of increasing complexity. One explanation for this increasing extravagancy in suture pattern is that it leads to a higher strength of the shell.
The terminal part (adult stage) is much shorter, erect, and bends over the older shell like a hook. They have transverse, branching ribs with tubercles (small bumps) along the venter. Suture pattern of Scaphites
Where the septum meets the shell a suture line forms; in some ammonoids these lines became extremely complex and elaborate, providing strength without the necessity of added weight. Elaborate sutures allowed for thinner shells, and hence less time needed for shell growth and less time spent in the vulnerable juvenile stage.
Adult Baculites ranged in size from about 7 centimetres (2.8 in) (Baculites larsoni) up to 2 metres (6.6 ft) in length. As with other ammonites , the shell consisted of a series of camerae, or chambers, that were connected to the animal by a narrow tube called a siphuncle by which gas content and thereby buoyancy could be regulated in the same ...
Arctomeekoceras is a genus of ammonoids in the order Ceratitida from the Early Triassic, included in the Meekoceratidae; a family characterized by more of less involute, compressed, discoidal forms that are smooth or weakly ornamented and have a ceratitic suture with broad saddles.