Cruziana
| Cruziana | |
|---|---|
| |
| Cruziana, fossil trackways of trilobites. | |
Trace fossil classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | †Trilobita |
| Ichnogenus: | †Cruziana d'Orbigny, 1842 |
Cruziana is a trace fossil (fossil 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.[1] It first appears in upper Fortunian rocks of northern Iran and northern Norway.[2] Cruziana has been extensively studied because it has uses in biostratigraphy (specific scratch patterns are unique to specific time intervals),[3] and because the traces can reveal many aspects of their makers' behavior.
Cruziana is typically associated with trilobites but can also made by other arthropods.[1] Cruziana appears in non-marine formations such as the Beacon Supergroup that would have been unsuitable environments for trilobites,[1] and in Triassic sediments that were deposited after trilobites became extinct at the end of the Permian Period.[4]
Cruziana traces can reach 15 mm across and 15 cm in length, with one end usually deeper and wider than the other.[1] The burrow may begin or end with a resting trace[5] 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.[6]
The ichnogenus Diplichnites may be produced where the trackmaker sped up.[citation needed] Several specimens of Cruziana are commonly found associated together at one sedimentary horizon, suggesting that the traces were made by populations of arthropods.[1]
References
[edit]- ^ a b c d e Woolfe, K.J. (1990). "Trace fossils as paleoenvironmental indicators in the Taylor Group (Devonian) of Antarctica". Palaeogeography, Palaeoclimatology, Palaeoecology. 80 (3–4): 301–310. Bibcode:1990PPP....80..301W. doi:10.1016/0031-0182(90)90139-X.
- ^ Daley, Allison C.; Antcliffe, Jonathan B.; Drage, Harriet B.; Pates, Stephen (22 May 2018). "Early fossil record of Euarthropoda and the Cambrian Explosion". Proceedings of the National Academy of Sciences of the United States of America. 115 (21): 5323–5331. Bibcode:2018PNAS..115.5323D. doi:10.1073/pnas.1719962115. PMC 6003487. PMID 29784780.
- ^ Seilacher, A. (1994). "How valid is Cruziana stratigraphy?". Geologische Rundschau. 83 (4): 752–758. Bibcode:1994GeoRu..83..752S. doi:10.1007/BF00251073. S2CID 129504434.
- ^ Donovan, S. K. (2010). "Cruziana and Rusophycus: trace fossils produced by trilobites … in some cases?". Lethaia. 43 (2): 283–284. doi:10.1111/j.1502-3931.2009.00208.x.
- ^ Garlock, T. L.; Isaacson, P. E. (1977). "An occurrence of a Cruziana population in the Moyer Ridge Member of the Bloomsberg Formation (Late Silurian)-Snyder County, Pennsylvania". Palaeontology. 51 (2): 282–287. JSTOR 1303607.
- ^ Kesidis, Giannis; Budd, Graham E.; Jensen, Sören (2018). "An intermittent mode of formation for the trace fossil Cruziana as a serial repetition of Rusophycus: The case of Cruziana tenella (Linnarsson)". Lethaia. 52: 133–148. doi:10.1111/let.12303.
Further reading
[edit]- Goldring, R. (1 May 2009). "The formation of the trace fossil". Geological Magazine. 122 (1): 65–72. doi:10.1017/S0016756800034099. S2CID 130340569.
- Jensen, Soren (2006). Trace Fossils from the Lower Cambrian Mickwitzia Sandstone, South-Central Sweden. Wiley. ISBN 978-82-00-37665-1.
- Vinn, O (2014). "Cruziana traces from the Late Silurian (Pridoli) carbonate shelf of Saaremaa, Estonia". Estonian Journal of Earth Sciences. 63 (2): 71–75. doi:10.3176/earth.2014.06.
External links
[edit]- Trackways and associated burrow; Photo--(Close-up); Graphic--(trilobite and burrow, etc)
- Argentine article on Cruziana "Remarkable Cruziana beds in the Lower Ordovician of the Cordillera Oriental, NW Argentina".
