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 Stegosaur Song (Stegosaurus Week)

The second of a pair of songs that I made especially for Stegosaurus Week!  "The Stegosaur Song" to the tune of "The Mexican Hat Dance."  Below is the link to the song:

Here are the lyrics to the song:

Full Lyrics:

Primitive stegosaurs they are all found in China, England, France, and Tibet
Lexovisaurus and Regnosaurus and a stegosaur not named quite yet
Chialingosaurus and Craterosaurus and Jiangjunosaurus too
Next we have the huayangosaurs from China and so far they number but two

[Chorus:]
Oh, the plates and the spikes like the head of a trike with them you definitely don't want to mess
The stegosaurs lived in the Jurassic but some lived to the dawn of the Cretaceous

Chungkingosaurus and Huayangosaurus and now we move on to the set
Gigantspinosaurus and then Kentrosaurus and Loricatosaurus you bet
Those last three were all primitive stegosaurids but still thought to be more advanced
There are two more still Paranthodon and Tuojiangosaurus I bet you're entranced

[Chorus]

The dacentrurines are the second to last of all the groups of stegosaurus
Dacentrurus who gives name to the group Miragaia and then there are no more
The stegosaurines are the last of the bunch Stegosaurus most notorious
Hesperosaurus and Wuerhosaurus and last of all Hypsirophus

[Chorus]

Are you diggin' the songs?  Well, then check out our playlist below!

CLICK HERE TO BE DIRECTED TO A FUN-FILLED PLAYLIST OF AMAZING SONGS.

Want to learn more about Stegosaurus and it's relatives?  Well, check out the Homebase for Stegosaurus Week HERE to partake in more of the festivities! 

Top Ten: Extinct Sea Monsters (Part 4 of 5)

7.  Archelon - Archelon is the largest sea turtle that has been discovered to date, the closest living relative that Archelon has is the "Critically Endangered" leatherback sea turtle, the largest sea turtle alive today.  Living in the Late Cretaceous Western Interior Seaway between 75-65 MYA, Archelon has been discovered in the states of South Dakota, Wyoming and Kansas. 

8.  Leedsichthys - Often cited as the largest fish known to humankind, the largest Leedsichthys had an estimated length of 72 feet, but some researchers believe that it could have grown to sizes that would rival those seen in the blue whale, the largest known animal ever to live on planet Earth.   Although Leedsichthys swam the seas only during the Jurassic Period, the group that it belonged to survived until the end of the Cretaceous Period.  Remains of this filter feeder have been uncovered in England, France, Germany, and Chile.  


COMING UP NEXT WE HAVE:

9.  Tanystropheus
10. Tylosaurus

This post is part of the "Top Ten: Extinct Sea Monsters" series.  For the rest of the posts in this series, click HERE.  

Top Ten: Extinct Sea Monsters (Part 2 of 5)

So why did I split this post up into five parts?  Well, originally it was all just one big post, but it was simply too big, like so often happens.  So I will just post the rest of the parts throughout the next few days.  So here is part number two!

3.  Liopleurodon - A member of the short-necked Plesiosaurs, or Pliosaurs, Liopleurodon was the top predator of the Middle and Late Jurassic shallow seas that covered Europe at that time.  Fossils of Liopleurodon have been found in England, France, Germany, and Russia. 

4.  Shonisaurus - Shonisaurus is a fascinating example of convergent evolution.  When similar environmental and ecological pressures went to work on the ancestors of Shonisaurus, and the rest of the ichthyosaurs, as well as the ancestors of the dolphins and porpoises, they produced very similar results in very different kind of animals.  Shonisaurus and the rest of the ichthyosaurs are marine reptiles, while the dolphins and porpoises are both mammals.  Shonisaurus lived during the Late Triassic Period, right around when the dinosaurs were first making their debut.  At least thirty-seven skeletons of this giant have been discovered in Nevada. In fact, Nevada is still a fantastic place to see some of these creatures, especially Berlin Ichthyosaur State Park in Berlin, a few hours outside of Reno (pictured below)!  This is where the first bones belonging to Shonisaurus were actually discovered!  Definitely high on the list of places that I want to go!

Coming Up:
5.  Elasmosaurus
6.  Dunkleosteus
7.  Archelon
8.  Leedsichthys
9.  Tanystropheus
10. Tylosaurus

This post is part of the "Top Ten: Extinct Sea Monsters" series.  For the rest of the posts in this series, click HERE.  

Animal Spotlight: The Okapi

For years, Europeans who traveled to Africa heard tell of a mysterious rainforest animal that they came to refer to as the "African Unicorn."  Apparently, Sir Harry Johnston, the British governor of Uganda, rescued a small group of the native inhabitants, often called the pygmies, from a foreign show person, who, sadly, was most likely going to use his abductees for a circus or freak show.  Upon their rescue at Johnston's hand, they repaid him by giving him information about the animal.

Now we know the animal as the okapi, or Okapia johnstoni, named in honor of Sir Harry Johnston.  Despite the zebra-like stripes on its tail, the okapi is not all that closely related to the zebra, and is actually a very close relative of the giraffe.  Although they may not look super similar, they both have ossicones on their head, similar to the base of DEER antlers.  Ossicones are not only possessed by both the okapi and the giraffe, but also by extinct relatives of both, such as Sivatherium and Climacoceras.

The okapi is listed as "NEAR THREATENED" by the IUCN.  Honestly, I was surprised that it wasn't at least listed as "VULNERABLE," and "ENDANGERED" or worse would not have surprised me at all, given its reclusive nature, its beautiful pelt, and the very fact that humans didn't have much proof of its existence until 1901, when Sir Henry Johnston sent back a carcass to England.  I suppose, however, that its reclusive nature likely helps it to evade human influences a great deal, coupled with the fact that the rainforest that it inhabits is not too heavily tread.  And I guess the fact that it was really made known to science only a little more than one hundred years ago couldn't have hurt either, as it would be soon entering into an age when nature was offered greater protection than in the 1800s. 

Like the COELACANTH and THE MOUNTAIN PYGMY POSSUM, the okapi is often referred to as a "LIVING FOSSIL."  Its habitat consists of montane rainforests in the Central African Republic (CAR) and the DEMOCRATIC REPUBLIC OF THE CONGO (DRC).