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Taphonomy of naraoiids (Arthropoda) from the Middle Cambrian Kaili biota, Guizhou Province, south China

Jih-Pai Lin
Taphonomy of naraoiids (Arthropoda) from the Middle Cambrian Kaili biota, Guizhou Province, south China
Palaios (February 2006) 21 (1): 15-25


Naraoiids in the Kaili biota (Taijiangian Stage, Wulingian Series, lower Middle Cambrian) are preserved in a variety of taphonomic states. Decomposition, entombment, and fossil diagenesis of Kaili naraoiid specimens (n = 69) are described. The decay rates of appendages, internal organs, and dorsal sclerites are different, and should be treated as separate taphonomic elements. A classification scheme to delineate the preservational states is proposed here to distinguish carcasses from molts in deposits with exceptional preservation. For example, at least 35% of Kaili naraoiids represent carcasses. Among them, approximately 21% of individuals are interpreted as having been buried alive (Type A preservational state) and 79% showed some evidence of decay prior to burial (Type B preservational state). 65% of naraoiids can be either molts or decayed carcasses, and molts typically are articulated (Type C preservational state). Disarticulated (Type D preservational state) specimens are rare. Kaili naraoiids were buried in three orientations with respect to bedding: (1) parallel, (2) oblique, and (3) folded-over (specimens with noticeably shortened anterior shields). Due to the nature of the naraoiid bauplan, most specimens ( approximately 77%) tend to be buried parallel to bedding. All naraoiid specimens with folded-over anterior shields (10%) represent carcasses. Identified taphonomic modifications caused by post-burial processes include extruded gut contents, three-dimensionally preserved internal organs, and sclerite fractures. Preservation of three-dimensional soft-parts accompanied by flattened hard-parts is interpreted here as the result of syndiagenetic anaerobic microbial decay. The relief and size of preserved midguts depend on: (1) availability of volatile tissues, (2) abundance and types of microbes, and (3) duration of anaerobic microbial decay prior to compactional dewatering.

ISSN: 0883-1351
Coden: SKT
Serial Title: Palaios
Serial Volume: 21
Serial Issue: 1
Title: Taphonomy of naraoiids (Arthropoda) from the Middle Cambrian Kaili biota, Guizhou Province, south China
Author(s): Lin, Jih-Pai
Affiliation: Ohio State University, Department of Geological Sciences, Columbus, OH, United States
Pages: 15-25
Published: 200602
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 94
Accession Number: 2006-034880
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., 2 tables, sketch map
N26°45'00" - N26°45'00", E108°25'00" - E108°25'00"
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: 200619
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