[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Just this n that

At 12:56 AM 3/18/97 GMT, Roger A. Stephenson wrote:

[Didn't see the Natty Geo Explorer, so can't comment on it.]

>Isn't it entirely possible that feathers evolved in arboreal creatures, not
>for flight first, but rather for the insulating factor? (My tree sitting
>experience and the wind chill factor). If you can't stay warm up a tree you
>sure aren't going to stay up there long enough to evolve flight
>capabilities. If the origins of flight resulted from creatures consistantly
>arboreal, cold wet weather would have to be addressed. Even in a much
>warmer climate where quick temperature changes are rare, such protection
>would have been handy.

Two bits:
I) It has long been recognized that protofeathers almost certainly had a
non-flying function, and were later exapted into use in
gliding/flying/parachuting/whatever.  Birds seem to be unique among
vertebrate flyers and gliders in that there is no evidence of a typical
flat-bodied gliding stage in their evolution.

II) Many ectotherms live very well up in trees: iguanas, chameleons, snakes,
and tree frogs, to name a few diverse groups.  All, of course, are warm
climate creatures, but there is not much compelling evidence for cold
forests in the Middle and Late Jurassic (the latest interval for the origin
of Archie's ancestors).

>Doesn't the micro and macro aspects of tyrannisaurid teeth arrangements,
>and jaw closing geometry, suggest a chunk ripper rather than a slash and
>puncture type bite? If most tyrannisaurids were chunk rippers would this
>support an ambush over chase hunting style, and why or why not? (No
>tripping threads please :-| ).

I do not see how this would favor one hunting style over the other.  Hunting
styles (ambush vs. pursuit) describe the sequence from prey identification
to prey acquisition.  We can try and correlated some anatomical features
(limb proportions, for example) with different hunting styles.  Once the
prey is acquired, how it is dispatched is determined by other aspects of
their biology (jaw geometry, for example).

In other words, hunting styles describe how the prey is caught, but not
necessarily what is done to it after it is caught.

>Is there any more material of Elmisaurid than what is cited in Dinosauria?
>Would it be possible for Elmisaurids to be discovered in the Hell CreeK

First off, combine the "caenagnathid" section of the "Oviraptorosauria"
chapter and the "Elmisauridae" chapter: they are the same group.

Secondly, additional material for this taxon includes the Chirostenotes
specimen with partial skull at the Royal Ontario Museum, the Turonian
central Asian form Caenagnathasia, and additional North American specimens
discussed in the Currie, Godfrey, and Nessov paper in the first
Sino-Canadian Dinosaur Project issue of the Canadian Journal of Earth
Sciences (30:2255-2272).

Finally, one of the specimens in the paper cited (Black Hills Museum
specimen 2033) is indeed from the Hell Creek Fm.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661