The Shark-Like Edestus: An Interview With Wayne Itano

We've heard from Wayne Itano before, when he told us about the Kremmling Cretaceous Ammonite Locality in Colorado. (To read the post, click HERE.) A physicist at NIST (National Institute of Standards and Technology) in Boulder, Colorado, Wayne also has a hobby interest in paleontology, and is a curator adjoint at the Natural History Museum of the University of Colorado. He has also been doing some very interesting work with a shark-like animal called Edestus, and he graciously agreed to answer a few questions for me regarding this creature! So please join me in welcoming Wayne Itano, as he tell us about this fascinating prehistoric creature!

Scissor-tooth model for Edestus.  Credit Ray Troll, www.trollart.com

The Natural World:  You've been doing some work with an ancient shark-like creature called Edestus. What can you tell us about it?

Wayne Itano:  Edestus is my candidate for the strangest shark of all time. In my opinion, it is even stranger than the better-known spiral-toothed Helicoprion, since it is harder to imagine how the teeth might have been used.  (Read more about Helicoprion HERE.)  Almost the only fossil remains of Edestus are its symphyseal (midline) tooth whorls, which consist of triangular, serrated teeth, joined together at the bases (roots).

Edestus had one tooth whorl in the upper jaw and one in the lower jaw. Since the whorls are bilaterally symmetric (same on the left side as on the right side), they must have been located in the middle of the jaws.

This is a photograph of a specimen of a species called Edestus mirus. It was found in Pennsylvanian-aged deposits (about 300 million years old) of Iowa.

Smithsonian Institution Specimen USNM V 7255. Scale in cm.  To see a better resolution of the picture, click HERE.  Photo Credit: http://collections.si.edu/search/results.htm?view=&dsort=&date.slider=&q=Edestus+mirus+holotype&tag.cstype=all

This is a rare specimen, since it shows both the upper and lower tooth whorls.

The curvature of the tooth whorls makes it difficult to understand how they could have been used.

According to the conventional reconstruction, the two tooth whorls were used as scissors, to cut prey between the two whorls, as in this drawing by Ray Troll.

Scissor-tooth model for Edestus.  Credit Ray Troll, www.trollart.com

To me, this model seems unlikely, given the curvature of the tooth whorls. It seems that the outer teeth are nonfunctional, since they can’t come together, so there would be no reason to retain them.

It seems to me that the teeth would be more efficiently used if the entire head was moved up and down, with jaws fixed, to slash large prey. This is a radically new idea. I have submitted an article for publication elaborating on this idea, but I expect that it may be some time before it gets into print.

New vertical-slashing model for Edestus. Drawing by Gary Raham, www.biostration.com, reproduced with permission of Wayne Itano

My new reconstruction of Edestus, showing the pair of symphyseal tooth whorls, in front, used for slashing prey, and flat teeth in the rear for crushing prey. Drawing by Gary Raham, www.biostration.com, reproduced with permission of Wayne Itano.

TNW: I noticed that you referred to Edestus as being a candidate for the "strangest shark of all time." Is Edestus truly a shark? If not, how do you classify it?

WI: I was using "shark" in an informal sense, as the term is not well-defined for many extinct fish. Edestus certainly falls within the class Chondrichthyes, which today comprises 2 subclasses - Elasmobranchii (sharks, including rays) and Holocephali (ratfish). There is some evidence that Edestus (and also Helicoprion) belong to an extinct line that is closer to the Holocephali than to the Elasmobranchii, but this is a matter of debate. It is safe to call Edestus a chondrichthyan, and I try to avoid the word "shark" when I write a technical paper, or maybe keep it in quotes.

TNW:  Tell us a little bit about your research.

WI:  I am interested in many aspects of paleontology, but for the last 22 years I have focused on fossil sharks, particularly ones from the Paleozoic (older than about 250 million years ago). My interest in Paleozoic sharks dates from 1991, when I found a finspine of a Pennsylvanian-aged shark called Ctenacanthus in a roadcut near the town of McCoy, in Eagle County, Colorado. I wrote an article about this find for the newsletter of the Western Interior Paleontological Society (WIPS) in 1992, which you can read by clicking HERE.

Ctenacanthus finspine found near McCoy, Colorado. Scale in cm.  Photo Credit: Wayne Itano

In trying to identify this finspine, I read everything I could find about Paleozoic sharks. Knowing of my interest in the topic, Professor Martin Lockley of the University of Colorado at Denver loaned me a large collection of shark teeth and finspines from McCoy that he and Karen Houck, also of CU Denver, had found in the 1980s. His paleontological interests had by then switched entirely to ichnology (footprints and other fossil traces), and he gave me the opportunity to write up the fossil shark specimens. I published an article on the finspines in 2003 with Houck and Lockley, which you can read HERE, but I haven’t finished with the teeth yet.

My interest in Edestus started when an amateur fossil collector showed me an unusual shark tooth that he had found at McCoy. After a bit of study, I realized that it was a tooth of Edestus, the first known from the entire Rocky Mountain region. This eventually led to my publishing a rather long paper on Edestus in 2012, again with Houck and Lockley, which you can read HERE.

Recently, I have also published three short papers related to Edestus: one on an Edestus tooth from England, one on an Edestus tooth with abnormal serrations, and one on a tooth from China that had mistakenly been identified as Edestus, but which actually belonged to a more “normal” shark called Carcharopsis.

TNW:  Do you have any future expeditions or research papers in the works?

WI:  Lately most of my “field work” has been in museum collections. In the last few years I have been able to view specimens in the collections of the Yale Peabody Museum, the Natural History Museum (London), the British Geological Society, the American Museum of Natural History (New York), and the New Mexico Museum of Natural History and Science. I have several publications in the works, largely based on fossil shark specimens I have seen in those collections.

One area is the taxonomy (classification) of Edestus species. About 15 species of Edestus have been named, but I think that many of these are synonymous. For example, people have named new species based on unusually small or large teeth, but I think they are just teeth of the same species of Edestus but of different ages. There may be as few as 3 valid species of Edestus.

I have another project where I am examining microscopic scratches on Edestus teeth. I am hoping that I can find feeding-related scratches and that their orientation will provide some clues as to whether the scissors-model or the up-down-slashing model is correct.

-Thank you so much, Wayne, for answering some of my questions!  I look forward to hearing more about Edestus in the future!  Thanks again!-

The Story of the Kremmling Ammonite Site and a Painting by Wayne Itano, Guest Blogger

Today, we have a very exciting post for you: a guest post from paleo-enthusiast Wayne Itano!  Here is a bit of background on Mr. Itano:  

Wayne Itano is a physicist at NIST (National Institute of Standards and Technology) in Boulder, CO.  He has a hobby interest in paleontology and is also a curator adjoint at the Natural History Museum of the University of Colorado.

Today, Mr. Itano is going to tell us about the Kremmling Ammonite Site.  Join me in giving him a warm welcome!  Let's get started!

The Kremmling Cretaceous Ammonite Locality lies on BLM (Bureau of Land Management) land to the north of the little town of Kremmling, in Grand County, Colorado.  It was first noticed for the very high concentration of very large ammonites(ammonites are extinct relatives of the modern chambered nautilus and were probably more closely related to octopi and squids).  It has been protected since the 1980s.  It was written up in the book “Cruisin’ the Fossil Freeway” by the paleontologist Kirk Johnson and the artist Ray Troll.

Dr. Kirk Johnson, formerly of the Denver Museum of Nature and Science, is now head of the Smithsonian Museum of Natural History.

Ray Troll is an artist with a special interest in natural history and ancient life.  Here is his painting “Night of the Ammonites” inspired by a visit to the Kremmling Ammonite Locality.

Artist Ray Troll’s picture of the Kremmling area, about 73 million years ago, during the Cretaceous Period, when most of Colorado was beneath the sea.  Picture Credit: Ray Troll

The large disk-shelled creatures are ammonites called Placenticeras.  The ones with narrow, straight, tapered shells are another kind of ammonite, called Baculites. The sharp-toothed swimming reptiles are called mosasaurs.  We have evidence from bite marks on ammonite shells that mosasaurs preyed on Placenticeras.  Over on the left are some strangely shaped small ammonites called Anaklinoceras.

The Kremmling site was featured by Earth Magazine, in a kind of online quiz called “Where on Earth.”  The page with the question and answer is HERE.

If you want to visit the Kremmling site, first pay a visit to the BLM office at 2103 E. Park Avenue, Kremmling.  They can advise you on road conditions.  At times it can be inaccessible, even for 4-wheel drive vehicles. Here is a sign at the site:

Warning sign at the Kremmling Ammonite protected area.  Photo Credit: Wayne Itano

Here is an informational sign.  Collecting is prohibited within the site, but there are nearby areas where collecting is allowed.  Inquire at the BLM office.

Explanatory sign at the Kremmling site.  Photo Credit: Wayne Itano

The area is littered with boulders containing the impressions of giant Placenticeras ammonites.  The fossils themselves have been collected, many to museums.  Intact boulders containing ammonites lie under the surface and could be studied in the future.

Boulders with impressions of Placentideras ammonites.  Photo Credit: Wayne Itano

Baculites (straight ammonites) are also rather common. 

A Placenticeras ammonite impression with a Baculites fossil (cylindrical object) on the same boulder.  Photo Credit: Wayne Itano

Large clams called Inoceramus are rather common.  Here are some examples.

A large Inoceramus clam fossil.  Photo Credit: Wayne Itano

A boulder with impressions of Inoceramus clams.  Photo Credit: Wayne Itano

Emmett Evanoff, a professor at the University of Northern Colorado in Greeley, has been studying the paleontology of this area.  One odd thing is that the great majority of the Placenticeras fossils are of females.  (The males are distinguished by being much smaller and having coarse ribs on their shells.) He thinks this might have been a nesting site.  The males would have fertilized the eggs and then left, leaving the females to guard the eggs.  Katie DeBell was a student of Emmett’s who mapped out the ammonites on the surface and seems to know them all by number.  She lives in Kremmling and often gives tours, especially to school groups.  Here she is, pointing out some features of one of the ammonites.

Katie DeBell explaining some features of an ammonite in 2011.  Photo Credit: Wayne Itano

I have a vacation house in the mountains not far from Kremmling.  I happen to know a painter who is also a fossil enthusiast, named Terry McKee.  I commissioned him to do a painting of the Kremmling site when it was an ammonite nesting ground.  I also asked Dr. Evanoff for advice, and the three of us met to plan the painting.  Here it is, and the original is now hanging in my mountain house.

Painting of the Kremmling Ammonite nesting site.  The large ammonites are guarding their eggs.  Baculites and various smaller ammonites, swim above.  The small round ammonite on the left, facing left, between two of the straight baculites, is a male Placenticeras.  A mosasaur lurks in the background.  Picture Credit: Terry McKee

- Wayne Itano

Thank you very much, Mr. Itano, for the post!  The post was really interesting, and I know I learned a lot!  I found the part about the nesting site particularly interesting!  I have no doubt that my readers, as well as myself, would love to hear from you in the future!  Thanks again! - Zack Neher

Bronze Tree on Dwellable