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Notes from the under-matrix.
Yesterday Chris Bennett attempted to refute my observations of dorsal
frills by noting that on all Niobrara specimens the chalk surface is
worked off so no trace of soft tissue can possibly be seen.
That is a great "Old School" answer.
But leave it to Nature to circumvent the ways of men.
One of the ways that fossils are discovered in bedding planes, is, of
course, by exposure of the fossils themselves. Another way is by noting
animal-shaped rises and stains in the matrix. Often the three go hand
in hand and preparators are thankful for this phenomenon because it
them to "see through" the overlying blanket of matrix to get at the
When preparators do their thing, unfortunately, poorly preserved soft
that accompanies fossils is removed. Fortunately, most preparators work
closely to the fossil so most of the matrix surface is preserved in most
cases, so things like babies and dorsal frills remain visible.
In the case of the Nyctosaurus from the Niobrara chalk I believe that
of preservation or "echoes" of the same above and below the bedding
are what I am seeing. In Ichnology these are called "underprints" I
Perhaps this is why the baby shapes are all unossified.