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David Kohls wrote: [deleted] >But please, for the sake of discussion, consider a specimen found in the >magnesian marlstone, lacustrine deposits of the western interior of the >United States. This specimen is of the tipulidae family. It is a complete, >full-bodied specimen. Both patterned wings are present, each being 2.6 cm >in length. Each is extended nearly perpendicular to the body with every >vein clearly discernable. Halteres are noted on both sides of the body. >Individual eggs are clearly visible within the abdomen of this fecund fly. >Examination of the faceted eyes shows the ommatidial support structures. >Within each structural harness can be counted at least 300 "facets", their >diameter being measured in microns. Mouthparts are present and complete. >Both obverse and reverse of the specimen are present. This specimen, >deposited inter-varvely, is of middle-Eocene age. Buried in the matrix, in >close proximity to this specimen, rests a specimen of a beetle and of a fly, >both showing excellent preservation. > >For you to more clearly understand the taphonomy of the above described, >actual specimen, which questions would you pose and which answers would you >seek? Start with, What is the thickness of the bed? Where in the bed is the fossil located (top, bottom, middle etc.) What is the matrix composed of? What is the geochemistry of the matrix? What is the fossil composed of (organic film, phosphate, or other)? What is the orientation of the fossil? What is the orientation of other fossils in the layer (same as fossil or different). Are other fossils in the same layer preserved in the same way? What is the faunal composition of the bed/layer. Is this faunal composition different from other beds/layers or similar. Are there any trace fossils associated with the bed/layer? Chris cnedin@geology.adelaide.edu.au nedin@ediacara.org ------------------------------------------------------------------- Many say it was a mistake to come down from the trees, some say the move out of the oceans was a bad idea. Me, I say the stiffening of the notochord in the Cambrian was where it all went wrong, it was all downhill from there.
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