''Cruziana'' is a

trace fossil A trace fossil, also called an ichnofossil (; ), is a fossil record of biological activity by lifeforms, but not the preserved remains of the organism itself. Trace fossils contrast with body fossils, which are the fossilized remains of part ...

(

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

records of lifeforms' movement, rather than of the lifeforms themselves) 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 found in marine and freshwater sediments. It first appears in upper

Fortunian The Fortunian age marks the beginning of the Phanerozoic Eon, the Paleozoic Era, and the Cambrian Period. It is the first of the two stages of the Terreneuvian series. Its base is defined as the first appearance of the trace fossil ''Treptichnus ...

rocks of northern Iran and northern Norway. ''Cruziana'' has been extensively studied because it has uses in

biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. "Biostratigraphy." ''Oxford Reference: Dictionary of Biology ...

(specific scratch patterns are unique to specific time intervals), and because the traces can reveal many aspects of their makers' behavior. ''Cruziana'' is typically associated with

trilobites Trilobites (; meaning "three-lobed entities") are extinct marine arthropods that form the class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most successful of all early animals, ...

but can also made by other

arthropods Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

. ''Cruziana'' appears in non-marine formations such as the Beacon Supergroup that would have been unsuitable environments for trilobites, and in

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

sediments that were deposited after trilobites became extinct at the end of the Permian Period. ''Cruziana'' traces can reach 15 mm across and 15 cm in length, with one end usually deeper and wider than the other. The burrow may begin or end with a resting trace called '' Rusophycus'', the outline of which corresponds roughly to the outline of the trace-maker, and with sculpture that may reveal the approximate number of legs, although striations (scratchmarks) from a single leg may overlap or be repeated. ''Cruziana tenella'', and conceivably other ichnospecies, appears to have been formed by the concatenation of a series of ''Rusophycus'' traces, suggesting that ''Cruziana'' is a feeding trace, rather than a locomotory trace formed by burrowing within a layer of mud as historically believed. The ichnogenus '' Diplichnites'' may be produced where the trackmaker sped up. Several specimens of ''Cruziana'' are commonly found associated together at one sedimentary horizon, suggesting that the traces were made by populations of arthropods.

References

External links

Trackways and associated burrowGraphic--(trilobite and burrow, etc)Argentine article on ''Cruziana''
"Remarkable ''Cruziana'' beds in the Lower Ordovician of the Cordillera Oriental, NW

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

". {{Taxonbar, from=Q5190350 Arthropod trace fossils Fossil trackways

References

Further reading

External links