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Cruziana
''Cruziana'' is a trace fossil consisting of elongate, bilobed, approximately bilaterally symmetrical burrows, usually preserved along bedding planes, with a sculpture of repeated striations that are mostly oblique to the long dimension. Trace fossils can reveal many aspects of their makers' behavior, and work on ''Cruziana'' has been extensive.
The makers of ''Cruziana'' are mainly considered to have been trilobites; since they appear in the non-marine Beacon Supergroup, and Triassic deposits (after trilobites went extinct ()) they must also have been made by other arthropods. In some cases, the burrow begins or ends with a resting trace, called ''Rusophycus'', whose outline corresponds roughly to the outline of the tracemaker, and whose sculpture may reveal the approximate number of legs, although striations (scratchmarks) from a single leg may overlap or be repeated. If the trilobite sped up, ichnogenus ''Diplichnites'' may result. Several specimens of ''Cruziana'' are commonly found associated together at one sedimentary horizon, suggesting that they were made by populations of trilobites.
''Cruziana'' can reach 15mm across and 15 cm in length, with one end usually deeper and wider than the other.〔
The trace fossil is found in marine and freshwater environments.〔 It has uses in biostratigraphy; certain scratch patterns are unique to certain time intervals.
==References==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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