Ammonities vs Nautiloids

During the days of the dinosaurs there were underwater creatures which have tentacles growing from their heads but do not have backbones— instead they have shells. These creatures are called cephalopods. The most famous among the cephalopods are the ammonities and nautiloids. These cephalopods are usually mistaken as the same. Sometimes people get confused which is which. This is because the nautiloids have the same outer physical appearance as the ammonite. The nautiloids shell is flat and coils around like that of the ammonites; this is where the confusion all began. However there are certain differences between the two which are also very significant. These differences are found inside their shell.

It is in the interior of the shell where one finds out the differences between the two. The interiors of the shells have septas. Septas are bulkheads that divide the chambers inside the shell of these cephalopods. When you open up the shell and examine the interior part of it, you will find these septas and you will be able to notice the great difference between the two cephalopods. When you observe the septa of the nautiloid you will be able to notice that it is quite simple, unlike that of the ammonites. The nautiloids have septas that look more like contact lenses while the ammonites have septas that look more like lasagna. It is full of swerves and loops and other complex margins.

Another difference is their shell’s tube. These tubes that stretch through the length of the entire shell of these cephalopods are called siphuncle. The siphuncle of the nautiloids runs through the center of the septrum while the siphuncle of the ammonite runs around its shell’s outer edge through the edge of every septum.

The time the dinosaurs extinct were the same time that the ammonites were also extinct. There is still one genus of nautiloids that survived though. The fossils of the ammonites these days formed as a planispirals, which means it looks like corals that spiraled.

These are some of the major differences between the two cephalopods. These interesting creatures, though they look a like, have significant difference between them after all. However, to notice the difference between the two you have to literally get into it. This is because you have to see the interior part of these cephalopods just to see the difference. These cephalopods are being studied these days through their fossils, except for the few species of nautiloids that survived up until the present day.

SUMMARY:

1.

The main difference between the two is seen in their interior, which are the septa. The nautiloids have simple shaped septa while the ammonites have complex septa.
2.

The tubes in their shells, the siphuncle differ from each other. The nautiloids run through the center while the ammonites have their siphuncles running through the edges around their shells.
3.

Lastly, there are no more ammonites left and there is still specie of nautiloids surviving up to this day.

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