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Cephalopod Awareness Days: Nifty Nautiloids

October 9, 2012
Photo of an extant chambered Nautilus

Extant chambered nautilus. Please note its many arms, they’re just one of its many charms. Photo by Rofanator on Flickr

Greetings Blogophiles! It’s October 9th, day two of Cephalopod Awareness Days. Today is nautiloids and other lesser known cephalopods. Most of you are probably already aware of nautiloids, they show up as jewelry, as table decorations and for all you math enthusiasts, the shell of the chambered nautilus is frequently used as an example of Euclid’s golden ratio. It is good to be aware of nautiloids.

Nautiloids are a group of cephalopods belonging to the subclass Nautilidea. They have been around since the Late Cambrian, over 500 million years. The shape of their shells has varied greatly between the nautiloid orders and over geologic time. Some were slightly curved, known as cyrtocones, some had straight shells, known as orthocones.  Some orthocone cephalopods even had shells that start off tightly coiled but then straighten out, making them look almost like a shepherd’s crook.  Orthocone cephalopods went extinct it the Late Triassic.

Photo of Orthoceras, an orthocone cephalopod

Several specimens of Orthoceras, an orthocone cephalopod, which have been cut and polished. Photo by A.VaDA on Flickr

The extant genus Nautilus, a tightly coiled form, is a distant relative of a nautiloid order which evolved sometime in the Early Devonian, about 400 million years ago. Nautilus is considered to be a living fossil. Please note: there was no clear transition from straight to curved shells as many of these forms co-existed with each other.

Photo of a paper nautilus in a glass jar

A paper nautilus is really an octopus. Photo by NOAA Photo Library on Flickr.

Here are some fast facts:

  • Nautiloids flourished in the Paleozoic but only a few species are alive today.
  • Extant Nautiloids live in deep water, usually 100-500 meters deep.
  • Nautilus has ~90 arms or tentacles, which have ridged surfaces instead of sucker discs.
  • Nautiluses can live over 20 years
  • Extant nautiluses do not have ink sacs
  • The paper nautilus is not a nautiloid. It is technically and taxonomically an octopus. Its “shell” is really a brood chamber.
  • The beaks or jaws of nautiloids are preserved as fossils called rhyncholites (the upper jaw) and conchorhynchs (the lower jaw). I recently co-authored a paper on them: Weaver, P.G., Ciampaglio, C.N., Sadorf, E.M., 2012. Rhyncholites and conchorhynch (calcified nautiloid beaks) from the Eocene (Lutetian/Priabonian) Castle Hayne Formation, southeastern North Carolina. Neues Jahrbuch fur Geologie und Paläontologie. Abhandlung. 264 (1):61-75.
Photo of Rhyncholites aturensis, three views

Rhyncolites aturensis is a calcified upper jaw part from a fossil nautiloid. This image shows three different views of the same specimen. Photo by Eric Sadorf; used with written permission.

So please wave a many armed salute to our friends the nautiloids and tune in tomorrow for day three of Cephalopod Awareness Days.

Photo of Conchorhynchus furrus, three views

Conchorhynchus furrus, the calcified lower jaw of a fossil nautiloid. These are very rare in the fossil record; this is the first one described from the Eocene of North America. Three views of the same specimen. Photo by Eric Sadorf; used with written permission.

3 Comments leave one →
  1. October 9, 2012 12:43 pm

    Reblogged this on NC Museum of Natural Sciences Blogs and commented:

    by Trish Weaver

  2. October 9, 2012 3:39 pm

    Impressive Day 2! It makes me appreciate my earrings even more. Um, I suppose it’s unethical for a paleontologist’s mom to have earrings made out of ancient cephalopods, huh? Sorry. They really are pretty. I’m waving all of my arms for ICAD!

    Betty Lawver

    • Trish Weaver permalink
      October 9, 2012 4:17 pm

      Hi Betty,
      There is nothing wrong with you owning a pair of cephalopod earrings. You should wear them with pride for Cephalopod Awareness Week.

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