What are ammonite sutures?
Ammonite shells have complex patterns of suture lines that vary across species. The lines are formed at the intersection of the outer shell wall and the septa. The wavy septa can form if the rear mantle of the ammonite, which functions as the template, has a complex shape.
Why do ammonites have complex suture lines?
If ammonites were vertical migrants, they might have evolved more complex shell sutures, compared to earlier ceratitic and goniatic clades, to protect their shell from intense changes in hydrostatic pressure.
What are sutures in fossils?
(Ammonites) The term “suture pattern” refers to the featured line that makes contact with the septa and the interior of the aragonitic shell. Ammonoid suture patterns show more complexity in comparison to the nautiloids whose sutures are comparatively simple.
What are the characteristics of ammonites?
Some ammonites had long, straight shells, while others had helix-shaped shells. Most species, however, had coiled shells lined with progressively larger chambers separated by thin walls called septa. The animals constantly grew new shell material as they aged, but the their bodies always remained in the outer chamber.
How big do ammonites get?
Ammonites came in a range of sizes, from just a few millimetres to times bigger, with larger sizes more common from the Late Jurassic onwards. The largest known species of ammonite is Parapuzosia seppenradensis from the Late Cretaceous. The largest specimen found is 1.8 metres in diameter but is also incomplete.
What are Ammonoid sutures for?
Complex sutures in advanced ammonoids indicated their ability to sharply change the velocity of their movement when chasing their prey or escaping from predators.
Why are ammonites good index fossils?
Ammonoids are important index fossils because of their wide geographic distribution in shallow marine waters, rapid evolution, and easily recognizable features. Three groups of ammonoids succeeded one another through time, each group having a more complex suture pattern.
Is ammonite still alive?
The ammonites became extinct at the end of the Cretaceous, at roughly the same time as the dinosaurs disappeared. However, we know a lot about them because they are commonly found as fossils formed when the remains or traces of the animal became buried by sediments that later solidified into rock.
How many tentacles did ammonites have?
It is believed that Ammonites had eight, grasping arms and two much larger tentacles. These two tentacles had many suckers on the end which helped these animals grab prey. It is likely that because of the variety and diversity of Ammonite species, that these creatures occupied a number of niches in marine food webs.
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