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Feathers of the Ingersoll Shale, Eutaw Formation (Upper Cretaceous), eastern Alabama; the largest collection of feathers from North American Mesozoic rocks

Terrell K. Knight, P. Sean Bingham, Ronald D. Lewis and Charles E. Savrda
Feathers of the Ingersoll Shale, Eutaw Formation (Upper Cretaceous), eastern Alabama; the largest collection of feathers from North American Mesozoic rocks
Palaios (June 2011) 26 (6): 364-376

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 Lagerstatte 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 approximately 1 mu m 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.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 26
Serial Issue: 6
Title: Feathers of the Ingersoll Shale, Eutaw Formation (Upper Cretaceous), eastern Alabama; the largest collection of feathers from North American Mesozoic rocks
Affiliation: Auburn University, Department of Geology and Geography, Auburn, AL, United States
Pages: 364-376
Published: 201106
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 68
Accession Number: 2011-061491
Categories: Vertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: NSF Grant EAR-0633839
Illustration Description: illus. incl. sect., strat. col., 2 tables, geol. sketch map
N32°04'00" - N32°31'60", W85°25'00" - W84°52'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 201134
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