Search results
Results from the WOW.Com Content Network
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
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 chambers are separated by walls called septa. The line where each septum meets the outer shell is called the suture or suture line. Like other true ammonites, Baculites have intricate suture patterns on their shells that can be used to identify different species.
A variety of ammonite forms, from Ernst Haeckel's 1904 Kunstformen der Natur.. This list of ammonites is a comprehensive listing of genera that are included in the subclass †Ammonoidea, excluding purely vernacular terms.
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
Sutures are generally ammonitic, characterized by complex saddle and lobe patterns. However, in some derived forms, the suture pattern becomes simplified, appearing ceratitic or even goniatitic. The Ammonitina are derived from the Phylloceratina, another ammonitid suborder which has its origin in the Ceratitida of the Triassic .
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.
Early whorls have umbilical tubercles that in later whorls appear higher on the sides. Earlier whorls normally have lower and fine upper ventrolateral clavi. Ornament weakens in the adult and the last whorl may be smooth. The suture is with numerous adventitious and auxiliary elements, with saddles and lobes that are much frilled.