Re: BIRDS AS SUB-ORDER OF DINOS

[Thomas_R_HOLTZ@umail.umd.edu (th81)]

>BIRDS AS SUB-ORDER: I think that's causing all of this confusion about
>whether birds are a sub-order of dinos or an order unto themselves is
>caused by the lack of three-dimentionality in the system. The system
>was invented to classify living animals, all of whom (surprise) were
>(are) alive at one point in time. There are many birds as there were
>dinos, so it's on the one-hand ridiculous to say that B is a subset
>of D when B is as big as D.

If birds are a subset (but NOT a 'suborder') of Dinosauria, then of course,
B<D.  By a headcount, however, the known species of bird far outnumber those
of nonavian dinosaurs.

> By a headcount, Dinosaurs can be divided
>into two groups, one called birds and the other called Dinosaurs.
>Perhaps we need to look at a third-dimension and consider birds the
>(for want of something better) "successor order" to Dinosaurs?
>That would account for the fact that the two orders/whatevers
>existed at different times.3

Birds were present at least by the Kimmeridgian (Late Jurassic), so they
coexisted with nonavian dinosaurs for 80 million years or so.  In fact, they
spent more time living with other dinosaurs than living without them (only
65 million years).

And, of course, you could use a system of nested hierarchies which
recognized that birds arose within the group Dinosauria, just as dinosaurs
arose among the group Archosauria, which arose within the Diapsida, which...
>

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