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Original spotted patterns on Middle Devonian phacopid trilobites from western and central New York

Christopher A. McRoberts, Thomas A. Hegna, Jeri J. Burke, Morgan L. Stice, Steven K. Mize and Markus J. Martin
Original spotted patterns on Middle Devonian phacopid trilobites from western and central New York
Geology (Boulder) (March 2013) 41 (5): 607-610


Preserved color markings in Paleozoic fossils are rare and have been hypothesized to reflect muscular attachment scars, diagenetic artifacts, or the altered remains of biochromes (organic pigments) or sclerochromes (structural colors) embedded in fossilized skeletal remains. More than 25 exceptionally well preserved phacopid trilobites with spotted patterns are described from the Middle Devonian of western and central New York State (USA). The small ( approximately 0.23 mm) circular markings appear either brown on a lighter cuticle, or white on a darker cuticle. Thin section, scanning electron microscope imaging, energy-dispersive X-ray spectroscopy, and wavelength-dispersive spectroscopy elemental analyses show spots to be microcrystalline low-Mg calcite spheres embedded within the primary layer of the cuticle below the prismatic layer. Surrounding exoskeleton (low-Mg calcite) exhibits coarser crystallinity, typical lamellar structures, pore canals, and possible organic matrix, as expected for relatively unaltered trilobite skeletons. Potential diagenetic mineralogies or microstructures were not observed, making diagenesis an unlikely explanation. Spot distribution, morphology, and position in exoskeleton rule out a relationship with sites of musculature attachment and/or insertion. We suggest that spots represent original biologic structures manifested as either crystallographic or optical loci resulting in sclerochrome spots or possibly clear spots embedded in the cuticle that contrasted with a pigmented exoskeleton and may have served as windows to an underlying epidermis.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 41
Serial Issue: 5
Title: Original spotted patterns on Middle Devonian phacopid trilobites from western and central New York
Affiliation: State University of New York at Cortland, Geology Department, Cortland, NY, United States
Pages: 607-610
Published: 20130318
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 27
Accession Number: 2013-030732
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2013166
Illustration Description: illus. incl. strat. col., sketch map
N40°30'00" - N45°00'00", W79°45'00" - W71°55'00"
Secondary Affiliation: Western Illinois University, USA, United States
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 the Geological Society of America, Boulder, CO, United States
Update Code: 201319
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