[PatrickHenry]

... these are more likely an old group, just newly discovered, especially since the authors said they were related to the oldest branch of the forams.

Seems likely. I was just using this as an example. A new body type could pop up. In a crowded world it would have a tough time, and it would take forever for it -- and its ever-varying progeny -- to be recognized as a new phylum. The whole conjecture was in response to a question about "why don't we see new phyla"?

[furball4paws]

"The whole conjecture was in response to a question about "why don't we see new phyla"?"

I think the answer is simply that we have too short a time frame (say a couple hundred years since people have really been looking - not enough time for anything to happen from an evolution point of view, except extinction).

The forams form one of the best cases for "punctuated equilibrium". There's a 10 million year stretch of great fossil data from the late miocene to the present.
(Malmgren, B.A., W.A. Berggren and G.P. Lohmann. 1983. Evidence for punctuated gradualism in the Late Neocene Globorotalia tumida lineage of Planktonic Foraminifera. Paleobiology 9:377-89.