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Theropod(?) and bird feathers from Alabama



From: Ben Creisler
bh480@scn.org

A new advance abstract from June PALAIOS:

Terrell K. Knight, P. Sean Bingham, Ronald D. Lewis, and Charles E. Savrda
(2011)
Feathers of the Ingersoll shale, Eutaw Formation (Upper Cretaceous),
eastern 
Alabama: The largest collection of feathers from North American Mesozoic
rocks.
PALAIOS 26: 364?376 
DOI: 10.2110/palo.2010.p10-091r 
http://palaios.ku.edu/26/6/knight.pdf

ABSTRACT:
The Ingersoll shale (Santonian) is a small mudstone lens in eastern
Alabama, interpreted as an abandoned tidal-channel fill that accumulated
rapidly within the lower reaches of a bayhead delta. The diverse biota
found in this fossil Lagerstätte includes 14 individual feather specimens,
the largest collection known from the Mesozoic of North America. Occurring
separately throughout nearly the entire thickness of the clay lens and with
a range of sizes and morphologies, the feathers most likely represent a
number of theropod 
species. Based on known taxa in the region, the largest specimen (16.5 cm)
may be a rectrix (tail feather) from a dromaeosaurid dinosaur or from a
hesperornithid. Smaller feathers may have belonged to a range of shore
birds. The best-preserved specimens were found in the finest grained
intervals. SEM examination reveals very well preserved microstructure
consisting of carbonized rod-shaped bodies ~1 µm in length, preserved in
three dimensions and solid internally. Although identical in size and shape
to modern 
feather-degrading bacilliform bacteria and displaying some bacteria-like
features, their alignment along the axis of feather structures indicates
that they are more likely the fossil remains of melanosomes, melanin bodies
used for color production during life. No three-dimensional arrays or
patterned differences of morphotypes have been seen thus far; almost all
elements are elongate (apparently eumelanin). Inferred colors for four of
the feathers, based on differences in melanosome morphologies, range from
gray and 
brownish gray to black. Whereas the majority of feather-bearing deposits
represent inland lakes, the estuarine setting adds a view of coastal
feathered theropods preserved in detail by rapid deposition of fine-grained
sediment. 


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