Re: fossil lichens? (from R. Hill)

[Benjamin Martin Waggoner <bmw@xxxxxxxxxxxxxxxxxxxx>]

Retallack's original paper in Paleobiology (which sparked a bit of
discussion on PaleoNet when it appeared) reviews the non-Ediacaran
fossil record of lichens, or lichen-like organisms, or things-that-
could-be-lichens. A botanist colleague has told me that a fossil
called _Nematothallus_, which has been considered problematic and
has been bounced around from taxon to taxon, might be a lichen; 
but it's 2:20 AM local time and I can't remember exactly when
Nematothallus lived or what it looks like. Can anyone clarify this?
There might be a few more lichens in amber. . . oh yeah, two
South African geologists, Hallbauer and Van Warmelo, have described
Precambrian filamentous microbes in gold-bearing deposits, that might
represent some sort of lichen-like symbiosis -- from what I've seen,
this isn't a fungal-eukaryote algal lichen, but might be an
actinomycete-cyanobacterial lichen, or something like that, which
is unusual but not unheard of today.

I'd surmise that lichens aren't at all common fossils. They're famous for
living in tough environments (bare rock surfaces, high latitudes, etc.)
but these habitats aren't exactly conducive to fossilization. Marine
lichens do exist, but I gather that most if not all extant forms inhabit the
rocky intertidal (another reason I'm skeptical of Retallack's hypothesis,
but that's another story). So much for my two cruzeiros' worth. Good
night.

Ben Waggoner
UCMP
Berkeley, CA 94720

I heard it was charged against me that I sought to destroy institutions,
But really I am neither for nor against institutions,
(What indeed have I in common with them? or what with the destruction of 
	them?)

					Walt Whitman