''Rusophycus'' is a

trace fossil A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...

ichnogenus An ichnotaxon (plural ichnotaxa) is "a taxon based on the fossilized work of an organism", i.e. the non-human equivalent of an artifact. ''Ichnotaxa'' comes from the Greek ίχνος, ''ichnos'' meaning ''track'' and ταξις, ''taxis'' meaning ...

allied to ''

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. It is fo ...

''. ''Rusophycus'' is the resting trace, recording the outline of the tracemaker; ''Cruziana'' is made when the organism moved. The sculpture of ''Rusophycus'' may reveal the approximate number of legs that the tracemaker had, although striations (scratchmarks) from a single leg may overlap or be repeated. Both ''Rusophycus'' and ''Cruziana'' are typically associated with

trilobites Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

but can also be made by other arthropods. ''Rusophycus'' is known from sediments dating to the earliest Cambrian Period (somewhat before the first appearance trilobite fossils), and from the

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

Period (after the

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last ...

extinction of trilobites), indicating that other producers could make the trace.

References

Arthropod trace fossils {{trace-fossil-stub