5 Different Types of Nautiloids

Types of Nautiloids
Image credit: J. Baecker via Wikimedia

If you’re going to see nautiloids on your next dive, you’ll have a lot of fun trying to figure out which type you’re looking at. Nautiloids belong to the same family as squid and cuttlefish. 

They are considered the most intelligent invertebrates because they can solve problems and use tools in certain situations.

Learn more about the different types of Nautiloids below!

1. Plectronoceratoidea

Many divers enjoy exploring the vast ocean depths looking for sunken shipwrecks, or trying to discover new species.

There are many different types of nautiloids (carnivorous mollusks) that you might see while diving and some are more common than others.

This blog post is a rundown of six different types of nautiloids that you may be able to spot while submerged.

Plectronoceratoidea: These carnivorous nautiloid mollusks live at deep ocean depths and have elaborate, striped markings all over their shells.

They can be identified by their large heads and wide mouth, which they use to suck in prey items.

2. Endoceratoidea

Endoceratoidea is types of nautiloids, the other being Actinoceratoidea. They have an inwardly facing apex. This can be seen in their shell’s surface. 

Endocertioids create exogastric coiled shells, meaning they curve outward around the inside. The trailing whorl often appears as a lid to the opening aperture.

These shell features make them easy to spot while underwater. This ease makes them susceptible to damage when encountering solid currents and surf.

3. Orthoceratoidea

Nautiloids are a large, diverse group that includes the chambered cephalopods. The traditional classifications divide them into two orders: Orthoceratoidea and Gastropoda.

Some recent molecular research suggests that the two orders should be combined into one order called either Oncocerida or Totanceroidea. 

Several other groups may be considered part of the nautiloid group, such as Actinocerida, Belemnitida, and Clymeniida. These animals are characterized by an exoskeleton composed of multiple calcareous sections known as septa.

A fold along the ventral side of each septum allows it to extend outward so that when its dorsal surface is pressed against another septum, it seals off a chamber within the shell

4. Actinoceratoidea

All nautiloids are in the Cephalopoda, but they are not all members of the subclass Ammonoidea. Unlike many other species, the nautilus is only distantly related to octopus, squid, and cuttlefish; it’s more closely related to squids and cuttlefish. The most common group that people see when diving is probably Actinoceratoidea.

 It is a family of shells with a spindle-shaped body that tapers at both ends. It has about 60 genera and about 250 living species that inhabit warm or temperate waters worldwide.

These types of nautiloids can be found as deep as 600 feet (183 meters) below sea level or as shallow as 0.5 miles (0.8 kilometers) below sea level.

5. Discosoritoidea

The most important thing about discovering Discoaster, our proto-nautilus, is that it marked the end of great controversy.

Until its discovery in 1857, scientists and laypeople were enraptured with an age-old debate: had these animals died out in prehistoric times, or did they still exist? 

And if the latter was true, where could one find these elusive creatures in their natural habitat? So when Esmark found this fossilized animal with an eerily head-shaped shell with eight rays lining its back and saw that it resembled many other forms of cephalopods he’s studied in Denmark and elsewhere, he could finally answer all questions once and for all by naming his newest find: Nautilus.

Conclusion

If you are a scuba diver, you might have had the opportunity to swim with many different types of nautiloids.

It is hard to know where they all come from and how they all look because they come in many shapes and sizes. Fortunately, it is possible to identify them by looking at their features or behaviors. 

One type is called ammonites. They are extinct, but their fossils can be found worldwide. Another type, while more recent than ammonites, still became extinct because of something happening to the environment – such as global warming or pollution – many years ago.

These types of nautiloids were squid-like animals with shells like oysters and clams; most people refer to them as belemnites.

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