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Regions of the suture line and variants in suture patterns Ammonite clean cut While nearly all nautiloids show gently curving sutures, the ammonoid suture line (the intersection of the septum with the outer shell) is variably folded, forming saddles ("peaks" that point towards the aperture) and lobes ("valleys" which point away from the aperture).
Ammolite comes from the fossil shells of the Upper Cretaceous disk-shaped ammonites Placenticeras meeki and Placenticeras intercalare, and (to a lesser degree) the cylindrical baculite, Baculites compressus. Ammonites were cephalopods, that thrived in tropical seas until becoming extinct along with the dinosaurs at the end of the Mesozoic era.
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 fossil cast of the shell of a Baculites grandis on display at the North American Museum of Ancient Life in Lehi, Utah.
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]
Only a few goniatites' full trophic apparatuses have ever been described, and reports of stomach contents in these creatures' fossils remain questionable at best. However, goniatites clearly lacked the calcified jaw apparatuses developed in later ammonites ; this has been cited as evidence against their having a durophagous (shell-crushing) diet.
Their shells had ornate ribs whose function is unknown, although some scientists have speculated that these ribs helped strengthen the animals' shells to allow them to live at greater depths where the water pressure is higher.
An aptychus is a type of marine fossil. It is a hard anatomical structure, a sort of curved shelly plate, now understood to be part of the body of an ammonite. Paired aptychi have, on rare occasions, been found at or within the aperture of ammonite shells. The aptychus was usually composed of calcite, whereas the ammonite shell was aragonite.
Ceratitidae is an extinct family of ammonite cephalopods. Fossils of Ceratitidae are found in the Triassic marine strata throughout the world, including Asia, Europe, the Middle East, North America, and Oceania.