RE: Hesperornis - Marine Dinosaur

[Toby White <mwhite@houston.rr.com>]

Mike:

I just finished my entry on this group, which is at 
http://home.houston.rr.com/vnotes/unit7.html#Hesperornithiformes, with a 
bit more at 
http://home.houston.rr.com/vnotes/notes/Hesperornithiformes.html. 
 Unfortunately, I left most of the lineage stuff out because it was either 
vague or unpublished.  However, the answer to your question seems to be 
'yes'.  Enaliornis is a rather scrappy fossil from the *lower* K of Britain 
which suggests an intermediate form.  I have read that Tim Tokaryk of the 
Royal Saskatchewan Museum has found a (unpublished) possibly flying 
Hesperornithiform in late K marine deposits in Saskatchewan, but I haven't 
followed up.

If you're doing any significant research on this group, I'm curious about a 
number of features I see inconsistently displayed in reconstructions, 
mostly dealing with the femur and the sternum.  Please let me know if you 
(or anyone else on the list) might be in a position to answer a few 
questions.

  --Toby White

Vertebrate Notes at
http://dinodata.net and
http://home.houston.rr.com/vnotes/index.htm


On Sunday, January 30, 2000 12:56 PM, Mike Everhart 
[SMTP:mjever@southwind.net] wrote:
> All,
> I'm looking for a general answer to a question concerning the lineage of
> Hesperoronis (fossil record and such). T. Mike Kelsey has already done
> the cladogram, so it is unnecessary to repeat those:
>    < http://dinosaur.umbc.edu/taxa/hesperornithiformes.html >
>
> Hesperornis has been referred to as the "only marine dinosaur" and is
> certainly the only one for which we have a fossil record. It apparently
> returned to the oceans (late Cretaceous), about the same time as the
> demise of the Ichthyosaurs and was competing successfully with
> plesiosaurs, mosasaurs and large fish in the more northern (cooler?)
> oceans. It arrived in Kansas in the early Campanian (Smoky Hill Chalk /
> Pierre Shale) but is never as common there as late Cretaceous deposits
> further north.
>
>            < http://www.oceansofkansas.com/hesper.html >
>
> It was very much a bird, with feathers,  but still had teeth, and solid
> (not hollow) bones. It's upper limbs were atrophied to the point of
> being almost useless, and it's lower limbs were so specialized for
> swimming that Hersperornis probably could not walk very well on land, if
> at all.  They apparently fed on fish and other small prey and in turn
> were eaten by mosasaurs:
>            < http://www.oceansofkansas.com/sdsmt.html >
>            < http://www.oceansofkansas.com/Varner/varner10.jpg >
>
> Also, described in this quote from:
>         < http://www.ummz.lsa.umich.edu/birds/ornclass/lecpa.html >
> "Mid-Cretaceous fossils Hesperornis and Ichthyornis were marine,
> toothed, large birds. Hesperornis includes 13 species of diving seabird
> ranging in size from a chicken to a large penguin, foot-propelled,
> superficially resembled modern loons, flightless. No keel on sternum,
> large cnemial crest on tarsometatarsus for swimming muscles like loon &
> grebe but different origin, vertebrae were heterocoelous like modern
> birds. Ichthyornis was a flying, tern-like bird, keel on sternum, same
> time as plesiosaurs in oceans. Apparently off the main lineage of bird
> evolution, vertebrae amphicoelous like primitive reptile, they left
> no living descendants. Both are closely related to modern birds, in
> Ornithurae."
>
> Is there any fossil evidence that they evolved from a bird that was
> capable of flight?  Other comments??
>
> Mike Everhart                       < http://www.oceansofkansas.com >
> Adjunct Curator of Paleontology
> Sternberg Museum of Natural History
> Fort Hays State University, Hays, KS