RE: paleonet Fossil Color

["Andy Rindsberg" <arindsberg@xxxxxxxxxxxxxxx>]

Title: Message

Hi Carl,

 

To answer your first question, some *modern* lingulids are brown and the Treatise attributes this to iron hydroxide. A glossy brown shell in bluish-gray limestone can be conspicuous, too. The presence of goethite in such specimens should be easy to test by x-ray diffractometry, if you're willing to reduce part of a specimen to powder. In the 1965 Brachiopoda part of the Treatise (p. H159-160), Jope wrote, "The dark brown color of the periostracum of _Lingula_ is due to iron, probably as ferric hydroxide, in places forming about 10 percent of its weight. The iron tends to be distributed in bands following growth lines, the regions representing embryonic or young growth of the shell containing much less proportion of iron than older regions." Oddly enough, I didn't see anything about this under "Shell Biochemistry" in a quick scan of the revised edition (1997). It may be helpful to know that finely crystalline goethite is yellowish whereas coarsely crystalline goethite is brown to brownish-black.

 

Harrington's story may be a tall tale, but he did say where it was set: one of the Triassic basins of eastern North America (Virginia? North Carolina?). Unfortunately, I lent my copy out and it was not returned.

 

Incidentally, the book was one of a series of at least three iterations. Harrington's geophilosophical musings were published first (?) as a presidential address, then as the brief and brilliant "To See a World", finally as "Dance of the Continents", which is perhaps a bit too long to sustain the charm of geowonder, but is still worth reading. The method of first lecturing on a subject, then writing it down, and finally expanding on it is especially good for people who are unused to expressing themselves to learn how to write well for an audience, who provide immediate feedback in the form of nods, looks of incomprehension or boredom, and smiles at unconscious humor. Louis Agassiz used this method too.

 

As to your third comment, all I can say is that you're probably right, but the field is wide open for research, as Jere Lipps pointed out. With recent interest in the molecular evolution of the eye, studies of pigments and color patterns are no longer peripheral and could well be funded.

 

You could also take a look at the AMNH collections of mollusks from the Alabama Paleocene and Eocene. Shine an ultraviolet lamp on a drawer of shells from the Gosport Sand or Greggs Landing Member, and you may be surprised at how many color patterns turn up.

 

Cheers,

Andy

 

Andrew K. Rindsberg

Geological Survey of Alabama

-----Original Message-----
From: Carl Mehling [mailto:cosm@amnh.org]
Sent: Tuesday, June 14, 2005 8:28 AM
To: arindsberg@gsa.state.al.us
Cc: paleonet@nhm.ac.uk
Subject: RE: paleonet Fossil Color

Hey Doc,

At 04:04 PM 6/13/2005, you wrote:

Carl,
 
Brownish inarticulate brachiopods are pigmented with iron hydroxide (presumably goethite), a relatively stable compound. There are many Cambrian and Ordovician examples of brown pigmentation in lingulids and obolids -- it's not a rare phenomenon. Some have a solid color, others are banded concentrically.

Probably unanswerable, but how can one tell if this brown is original or taphonomic/diagenetic?

John Harrington wrote in his wonderful work of geophilosophy, "To See a World", of cracking open a nodule to find a green leaf inside. It immediately began to curl, flake, and discolor. "Here was a Triassic salad, going to waste," he wrote. "So I ate it."

Was he being metaphoric (about it's greenness AND eating it)? Was he talking about the Clarkia or Oregon leaves?

I forget the details, but Hoare wrote a couple of annotated bibliographies on color in fossils. They should pop right up on GeoRef.

My guess is nearly all would represent color patterns rather than true color...

Thanks a million,
Carl

 Cheers,
Andy
 
Andrew K. Rindsberg
Geological Survey of Alabama

-----Original Message-----

From: paleonet-owner@nhm.ac.uk [mailto:paleonet-owner@nhm.ac.uk] On Behalf Of Carl Mehling

Sent: Monday, June 13, 2005 1:26 PM

To: paleonet@nhm.ac.uk

Subject: paleonet Fossil Color

Color patterns are common in the invertebrate fossil record, but real color is extremely uncommon across the board. I know of the Clarkia leaves, some amber insects and the Messel beetles. There must be a few more examples. I turn to you all.

Thanks,

Carl

Carl Mehling

Fossil Amphibian, Reptile, and Bird Collections

Division of Paleontology

American Museum of Natural History

Central Park West @79th Street

New York, NY  10024

(212) 769-5849

Fax: (212) 769-5842

cosm@amnh.org

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Carl Mehling
Fossil Amphibian, Reptile, and Bird Collections
Division of Paleontology
American Museum of Natural History
Central Park West @79th Street
New York, NY  10024
(212) 769-5849
Fax: (212) 769-5842
cosm@amnh.org

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