BIOGENIC  PRODUCTS

 

Biogenic products constitute another category of fossils.  Many paleontologists refer to such things as trace fossils, but they really aren't.  Biogenic products are objects produced by ancient organisms.  This is different from what trace fossils are (footprints, tracks, burrows, trails, bitemarks, etc.).

 

Examples of fossil biogenic products include eggs, amber (fossilized tree sap), coprolites (fossilized feces), and spider silk.



 

FOSSIL  EGGS

 

Fossil eggs are good examples of biogenic products - objects produced by ancient organisms.  The most famous fossil eggs are those of dinosaurs.  Dinosaur nests having eggs in their original laying position are known from several localities around the world.  Sometimes, x-ray analysis or cat-scan analysis shows the presence of dinosaur embryos inside intact eggs.  The embryos would be body fossils, but the surrounding eggshell material is a biogenic product.

 

Dinosaur eggshell fragment (5.2 cm across; eggshell thickness is 4 to 5 mm) - note the surface ornament consisting of large pustules or tubercles; commercial specimen identified as a sauropod dinosaur eggshell from the Upper Cretaceous of Patagonia, Argentina.

 



 

AMBER  &  COPAL

 

Fossilized tree sap (resin) is called amber.  Resin that has not been completely altered to amber is called copal (“subfossilized tree sap”).  The general term for such materials is resinite.

 

Copal ranges in age from several years old to ~33,000 years old.  True amber ranges in age from a few million to hundreds of millions of years old - as far back as the Carboniferous.

 

Amber and copal vary in color, but are typically a rich, light- to dark-golden brown.  Resinites are quite lightweight (but amber is denser than copal), and show conchoidal fracture when broken.  Copal often is, and has been, passed off as true amber.

 

Amber is valued as a gem material for its transparency and distinctive color.  Amber and copal are also valued for the frequent presence of fossil inclusions, typically insects.

 

Amber (resinite) - raw amber from the Baltics (left: 2.7 cm across; right: 3.1 cm across).

 


 

Baltic amber (resinite or succinite) (polished; 16 mm across) showing transparency and included fossil fly (Arthropoda, Insecta, Diptera, Brachycera).  The fly has a milky-white decay coating.

Stratigraphy & age: “Blue Earth layer”, “Amber Formation”, Lutetian Stage, lower Middle Eocene.

Locality: Kaliningrad District, Baltic Sea, far-western Russia.

 


 

Copal (left: 4.6 cm across; right: 4.9 cm across) - raw copal (likely very young) showing obvious crazing (surficial & near-surface cracking, the result of evaporation of volatile organics; amber does not craze quickly or as deeply as copal does - see Grimaldi, 1996).

 


 

Some modern trees release relatively copious amounts of resin.  The photos below show Acacia trees in the South Australian Outback that have oozed masses of resin.

 

Resin mass on Acacia tree (above & below) near Old Wirrealpa Mine, north of the Blinman-Wirrealpa Road, Flinders Ranges, South Australian Outback.

 


 

Resin mass on Acacia tree (above & below) near Old Wirrealpa Mine, north of the Blinman-Wirrealpa Road, Flinders Ranges, South Australian Outback.

 

 


 

Some references on amber & fossils in amber:

 

Poinar, G. & R. Poinar.  1994.  The Quest for Life in Amber.  Reading, Massachusetts.  Addison-Wesley Publishing Company.  219 pp.

 

Dahlström, A., L. Brost & J. Leijonhufvud.  1996.  The Amber Book.  Tuscon, Arizona.  Geoscience Press, Inc.  134 pp.

 

Grimaldi, D.A.  1996.  Amber, Window to the Past.  New York.  American Museum of Natural History.  215 pp.

 

Ross, A.  1998.  Amber.  London.  The Natural History Museum.  73 pp.

 

Poinar, G.O. & R. Milki.  2001.  Lebanese Amber, the Oldest Insect Ecosystem in Fossilized Resin.  Corvallis, Oregon.  Oregon State University Press.  96 pp.

 

Geirnaert, E.  2002.  L'Ambre, Miel de Fortune et Mémoire de Vie.  Monistrol-sur-Loire, France.  176 pp. [in French]

 

Hong Youchong.  2002.  Amber Insects of China.  Beijing.  Beijing Scientific Publishing House.  653 pp.  48 pls. [in Chinese]

 

Weitschat, W. & W. Wichard.  2002.  Atlas of Plants and Animals in Baltic Amber.  Munich.  Dr. Friedrich Pfeil.  256 pp. [excellent resource!  highly recommended!]

 

Selden, P. & J. Nudds.  2004.  Baltic amber.  pp. 131-141 in  Evolution of Fossil Ecosystems.  Chicago.  University of Chicago Press.

 

 



 

COPROLITES

 

Coprolites are fossilized fecal masses.  They range in size from microscopic-sized pellets to moderately sizable dung piles (see dinosaur coprolite below).  The most famous examples are “Washington coprolites” from the Miocene Wilkes Formation of Washington State, USA.  These are now considered cololites (intestinal casts).  True coprolites are fossilized dung.  Coprolite thin sections often reveal fragments of incompletely digested plant matter or sometimes undigested animal tissue.

 

So, coprolite studies can provide information about the diet of ancient organisms, assuming the coprolite maker is known with some specificity (which is very frequently not the case).

 

Coprolite - dinosaur coprolite, attributed to the Morrison Formation (Jurassic) of Cortez, Colorado, USA.

 


 

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