Rhizocorallium commune Schmid, 1876

Anistoroae, Anca & Miclăuș, Crina, 2015, The Cruziana Ichnofacies In The Lower Member Of The Bisericani Formation (Eastern Carpathians, Romania), Acta Palaeontologica Romaniae 11 (2), pp. 9-23 : 16

Rhizocorallium commune Schmid, 1876

Material: several epichnial specimens on top of sandstone beds from the R 21 interval, but also positive hypichnia right below the mentioned level ( Fig. 5e ).

Description: U-shape horizontal-subhorizontal tonguelike structures of 6-8 cm long, with up to 1.5 cm individual tunnel diameter ( Fig. 5f ). Usually the tubes are covered by striae. The distance between the limbs of U is up to 2.5 cm. One specimen reveals protrusive spreiten ( Fig. 5g ).

Remarks: Rhizocorallium is considered a burrow of deposit – feeding polychaete worm or a dwelling burrows of filter feeders ( Knaust, 2013). According to Seilacher

(2007), Rhizocorallium is ethologically interpreted as fodinichnia but without a behavioral genealogy. Gingras et al. (2009) noted that it is the result of a complex ethology of relatively deep tier tracemakers that systematically feed both with suspension and accumulated sediment. The Rhizocorallium from the analyzed section shows horizontal spreiten which normally represent deposit feeding of the subsurface strip-mining type ( Bromley, 1996). While feeding, the animal builds up the burrow for housing. The presence of striae is a clue for some deposit consistency at bioturbation time. They are usually found in littoral to neritic environment, the specimens older than Cretaceous being described exclusively in shallow waters ( Knaust, 2013). Rarely, it can be found in the deep water, indicating increasing oxygenation and depth of the redox boundary in sediment ( Kotlarczyk & Uchman, 2012). According to Buatois & Mángano (2011), this ichnospecies characterizes lower shoreface to the lower offshore environment.

Figures

Fig. 5 Trace fossils: a Thalassinoides swelled at branching point; b Thalassinoides swelled at terminal part of the tube; c Thalassinoides circular section in R23 interval; d Lockeia; e, f Rhizocorallium; g Rhizocorallium with protrusive spreiten; h Avetoichnus luisae