Cruziana

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Cruziana
Temporal range: Cambrian - Triassic, 537–250 Ma
Cruziana2.jpg
Cruziana, fossil trackways of trilobites.
Trace fossil classification e
Kingdom: Animalia
Phylum: Arthropoda
Class: †Trilobita
Ichnogenus: †Cruziana
d'Orbigny, 1842
Cruziana from the Devonian Brallier Formation or Harrell Formation.

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 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 tracemaker, 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[]

  1. ^ Jump up to: 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.
  2. ^ 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.
  3. ^ Seilacher, A. (1994). "How valid is Cruziana stratigraphy?". Geologische Rundschau. 83 (4): 752–758. Bibcode:1994GeoRu..83..752S. doi:10.1007/BF00251073. S2CID 129504434.
  4. ^ 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.
  5. ^ 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.
  6. ^ 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.

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