Avetoichnus Uchman & Rattazzi, 2011

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 : 17-18

Ichnogenus Avetoichnus Uchman & Rattazzi, 2011 Avetoichnus luisae Uchman & Rattazzi, 2011

Material: around 50 endichnia specimens in two levels of whitish-gray mudstone from the levels R 7 to R 17.

Description: dark-colored horizontal to slightly curved zip-like trace fossils. Specimens are up to 45 mm long and over 3 mm wide and appear as two rows of dots arranged along a central axis. Zip-like shape is the result of a “beheaded” helical spiral, each whorl of the spiral being preserved as a pair of dots ( Fig. 5h ).

Remarks: the ethology of the ichnospecies is debatable. According to Uchman & Rattazzi (2011), this complex trace fossil is an agrichnion of a non-graphoglyptide tracemaker which stashed the nutrients rich sediment in its central tubular axis for starting a bacteria farm. It was described as populating deep marine environment, but based on its co-occurrence especially with Rhizocorallium it seems that this species is rather a crossfacies one and its ethology may be more complicated than the original proposed one ( Anistoroae & MiclăuȘ, 2014).

Aside from the described ichnotaxa, many other trace fossils occur in the logged sedimentary succession, but systematic feeding traces of graphogliptides lack. They are generally three-dimensional, horizontal, and subhorizontal, some of them being in co-occurrence, while others are isolated. The plan-parallel or ripple cross laminated coarser beds are dominated by hypichnia, rare epichnia, while endichnia are well developed in the “background” laminated mudstone beds.

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