RE: paleonet odd ?microbial fossils

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Hi Jim and Jere,

I found similar structures in the early diagenetic recrystallisation of crustacean exoskeletons. They tended to form tight-ball rosettes, some hemispherical and twinned (or paired). The strucutres were up to 150 microns in size and made of calcite rather the than phosphate of the later diagenesis of the cuticle. It appears that the structures may have been bacterially mediated. Their size and form appear to depend on the crystalline structure of the skeleton and the organic content. I found that the structures appeared to form in high concentrations of phosphatic solutions (unpublished, but mentioned in my PhD thesis). There are also secondary 0.35micron spherical structures that form phosphatic replacements of the ultrastructure of the skeleton. These area also thought to be bacterially mediated. I haven't kept up with the literature on this, but I would search through papers by DEG Briggs over the last ten years.

Neil

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Dr Neil DL Clark
Curator of Palaeontology
Hunterian Museum
University of Glasgow
GLASGOW
G12 8QQ
tel: +44 (0) 141 330 3599
web sites: http://www.hunterian.gla.ac.uk/
http://www.scottishgeology.com/
http://www.geologyglasgow.org.uk/
http://www.hmag.gla.ac.uk/Neil/
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-----Original Message-----
From: paleonet-owner@nhm.ac.uk [mailto:paleonet-owner@nhm.ac.uk]On Behalf Of Jere H. Lipps
Sent: 10 August 2004 07:55
To: paleonet@nhm.ac.uk
Subject: Re: paleonet odd ?microbial fossils

Fungus?
Unfortunately, I know of no paleofungologists, although such things have been described in fossil wood and a few other places. I've seen it in long dead bones in the desert too.

At 08:26 AM 8/9/2004, you wrote:

For several years I have been coordinating study of fossils from the
Pipe Creek Sinkhole site, an earliest Pliocene (latest Hemphillian)
buried sinkhole deposit in Grant County, Indiana. We have found
thousands of plant and animal fossils from this unconsolidated deposti
(cf. Farlow et al., 2001, American Midland Naturalist 145: 367-278;
Martin et al., 2002, Journal of Vertebrate Palentology 22: 137-151).

Recently we've been looking at the preservation of vertebrate bone from
this site. There is little or no filling of pore spaces in the bone,
and the inorganic portion of the bone is only slightly modified
chemically from Recent bone.

In some of our thin sections of the bone, however, we see abundant
hemispherical (often paired) whatzits (to use a technical term) about 80
microns in diameter attached to the bone. These objects are
mineralized.

I've wondered if these might be mineralized remnants of microbial
colonies. Is there anybody on this list who knows about such things,
and would be willing to look at SEM images thereof, and offer an opinion
as to their identity?

James O. Farlow
Professor of Geology
Indiana-Purdue University Fort Wayne