Re: Fossil Stomach Contents in Marine Environments

[Danvarner@aol.com]

I'm forwarding Mike  Everhart's reply to M.J.Murphy's original post. A 
shameless plug (although I  haven't seen the book yet). DV :
> Have been reading Everhart's extremely  cool "Oceans of Kansas" book,

Thanks for the nice compliment on the  book..

> I could not help but note the frequent references to "fish in  a fish" 
fossils, or more generally fossils with preserved stomach  contents.  Am 
I correct in inferring that fossils like this are more  common in a 
marine environment? If so, why?  Because meals are more  likely to be 
swallowed whole?  Or not?

I really don't have any  data to compare the occurrence of our marine 
fossils with those from a  terrestrial environment, so I cannot say that 
they are more frequent or  not.. There is certainly some 'bias' in my 
(over?) reporting of the stomach  contents because that is an area of 
special interest to me. An increased  possibility of being preserved on a 
fairly quiet and nearly anoxic sea  bottom versus the likelihood of being 
scavenged on land probably has  something to do with it.

Reported in the book but also worth mentioning  here:

There are two large shark (/Cretoxyrhina/) specimens at the  University 
of Kansas with evidence associated prey; one with most of a big  teleost 
(/Xiphactinus/ /audax/) inside.. .and another with the definitely  
indigestible gastroliths left over from feeding on the guts of a  
probable elasmosaur.. Another shark specimen (/Squalicorax/) at the  
University of Wisconsin-Madison has the remains of several species of  
prey inside, including fish, turtle and mosasaur.

... /Xiphactinus  /seemed to have a bad habit of eating large prey 
(/Gillicus/, mostly).....  and dying well before the prey was digested.. 
X-fish were quite large (12-18  feet is a good range for what we see as 
fossils).  The most famous  specimen, the "Fish-in-a-fish" at the 
Sternberg Museum, is only 13 feet  long, and swallowed a 6 foot long 
Gillicus shortly before it died. I suspect  the prey weighed 90-100 lbs, 
was quite strong itself, and struggled a bit as  it went inside the 
larger fish. As I suggested in the book, and Dan's  artwork showed well, 
that's a big object to swallow, and I suspect something  vital in the 
X-fish was punctured in the process.  Another, much larger  (17 ft) 
X-fish that I found in 1996 also had the remains of a /Gillicus/  inside, 
digested just enough to become disarticulated... but the death of  the 
X-fish must have occurred less than 24 hours after eating.

These  instances may simply indicate bad luck or poor judgment on the 
part of the  predator... A 13 foot long X-fish must have fed on hundreds 
of smaller fish  without ill-effects during it's lifetime just to get 
that large.

At  least two specimens of a medium sized predatory fish (/Cimolichthys/) 
are  known to have died with a large /Enchodus/ inside as a last meal, 
and  another "choked" on a large squid...

The big /Tylosaurus/ in the exhibit  at the Smithsonian also died with 
the remains of a large meal inside.. in  that case a juvenile 
plesiosaur.. however, the gut contents were too far  along in the the 
digestive process to tell if the plesiosaur had been  swallowed whole or 
not.. I suspect that it had since most mosasaurs, and/  Tylosaurus/, in 
particular were not well equipped for 'slicing and dicing"  their prey. 
... but were very similar to a snake in their adaptations for  swallowing 
large prey. I have no idea what killed it.  Same goes for a  big 
/Tylosaurus/ found in South Dakota that was "stuffed" with the remains  
of a bird, a large fish and small mosasaur as it's last meal.

A large  elasmosaur we helped collect from the Pierre Shale  in 1992-93 
had a  lot of ground up fish bones mixed with gastroliths in it's 
crop/gizzard when  it died.... suggesting that it died reasonably soon 
after  eating...

Bottom line is that these specimens are somewhat more  interesting to me 
because of their association with prey, compared to the  majority of the 
remains found in the Smoky Hill Chalk, and are reported more  often. The 
incidence of preserved stomach contents is actually pretty low  compared 
to the huge number of vertebrate specimens that have been collected  
there since l868.

Regards,

Mike Everhart  <  mike@oceansofkansas.com >
Adjunct Curator of Paleontology
Sternberg  Museum of Natural History
Fort Hays State University, Hays,  KS
www.oceansofkansas.com