Cruziana semiplicata from the Furongian (Late Cambrian) of Severnaya Zemlya Archipelago, Arctic Russia, with a review of the spatial and temporal distribution of this ichnospecies

Abstract

The Furongian (Late Cambrian) Kurchavinskaya Formation of October Revolution Island, Severnaya Zemlya Archipelago, Arctic Russia, contains two distinctive morphotypes of the trace fossil Cruziana, both of which we assign to Cruziana semiplicata. A wider form shows characteristics typical of this ichnospecies with inner and outer lobes and marginal ridges. A narrow form has only an inner lobe with siculate, often interfering scratch‐marks, and rare, narrow marginal ridges. This narrow form, which shows characters in common with Cruziana tortworthi, probably represents burrowing in a strongly head‐down orientation. The record from October Revolution Island provides additional evidence that the palaeogeographical distribution of Cruziana semiplicata is not restricted to Gondwana, but also extend to parts of Baltica and North Kara. Cruziana semiplicata is known from the Furongian and Tremadocian of Gondwana, whereas on Baltica it is known only from the Furongian. Copyright © 2010 John Wiley & Sons, Ltd.

Were all trilobites fully marine? Trilobite expansion into brackish water during the early Palaeozoic

“…Maladioidella , a widespread taxon in Gondwana, has been indicated as the producer of C. semiplicata based on, among other criteria, that both co-occur in Furongian successions of Oman, Spain, and Wales [4]. However, Maladioidella has not been recorded from Argentina nor from other areas where C. semiplicata has been documented [38].…”

An intermittent mode of formation for the trace fossilCruzianaas a serial repetition ofRusophycus: the case ofCruziana tenella(Linnarsson )

“…The scratch pattern in some instances such as Cruziana semiplicata from the Furongian and lower Ordovician (Fortey & Seilacher ; Jensen et al . ; Sadlok ), can be complex with outer and inner lobes with differing ornament (Bergström ; Seilacher ). The discussion on the rusophyciform/cruzianaeform character of Cruziana has been recently revisited (Gibb et al .…”

“…The great number of morphological, and inferred behavioural, variants of Cruziana range from relatively short straight trace fossils with simple scratch patterns, to large scribbling circling trace fossils that are reminiscent of wide area grazing with minimal resource gathering optimization (Seilacher 1953(Seilacher , 1959(Seilacher , 1985F€ arber & Jaritz 1964). The scratch pattern in some instances such as Cruziana semiplicata from the Furongian and lower Ordovician (Fortey & Seilacher 1997;Jensen et al 2011;Sadlok 2014), can be complex with outer and inner lobes with differing ornament (Bergstr€ om 1969;Seilacher 2007). The discussion on the rusophyciform/cruzianaeform character of Cruziana has been recently revisited (Gibb et al 2016).…”

First Furongian (late Cambrian) trilobites from the Cantabrian Zone (north-western Spain)

“…Due to these Tremadocian occurrences of C. semiplicata, Fortey & Seilacher (1997, p. 111) suggest that it is likely that some other trilobite genus, morphologically similar to Maladioidella, may have been responsible for traces of the ichnospecies younger than Furongian. More recently, Jensen et al (2011) plotted all the occurrences of C. semiplicata around Gondwana, Baltica, the Kara plate and Siberia, showing that a direct link between Maladioidella of colcheni type and C. semiplicata is not evident for the Sierra de la Demanda, where there is a considerable stratigraphic distance between the records of both fossils. Additionally C. semiplicata shows variations revealing a number of different limb morphologies among its producers, or even cases in which the supposed exopodite brushings and the endopodite scratches may result from the same leg branch made in different digging postures.…”