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>From: Michael Edward Purvis <firstname.lastname@example.org>
> Requesting clarification... remarks I've read in different
> reference materials lead me to believe that the genus
> "Trachodon" has been labeled invalid at some point between
> the present time & when I first saw the name back during my
> grade school years.
> Anyone care to fill me in?:)
"Invalid" is perhaps a little too strong.
The name was originally given to a single tooth. This tooth
is what is called the type specimen. The rules require that the
name refers to *at* *least* this one specimen.
Now, unfortunately, most hadrosaurs ("duck-billed dinosaurs") have
similar teeth. This means that the Trachodon is formally indeterminate,
there is no way of telling which hadrosaur it *really* belongs to.
In formal taxonomic terms it is a "nomen dubium", or "doubtful
name". Thus the name Trachodon properly speaking only applies to this
one tooth, and to nothing else. (The structure of the tooth tends
to suggest that it was a *crested* hadrosaur, so it is extrememly
unlikely to belong to the flat-headed hadrosaur usually labeled
"Trachodon" in the older picures anyway - I currently list Trachodon
as Lambeosauridae incertae sedis).
Due to some other complex nomenclatural developments, the species
that used to be labeled "Trachodon" is now properly called Anatotitan.
In books of intermediate age you may see it labeled Anatosaurus,
which it turns out cannot be used either, for diferent reasons.
The peace of God be with you.