Planolites, Nicholson, 1873

Šamánek, Jaroslav, Vallon, Lothar H., Mikuláš, Radek & Vachek, Michal, 2022, A glimpse into ancient food storage: Sequestrichnia and associated nucleocave Chondrites from Eocene deep-sea deposits, Acta Palaeontologica Polonica 67 (3), pp. 767-779 : 770

Planolites isp.

Material. — Six specimens on 2 samples collected from the siltstone layer overlying the Zoophycos Bed ( MZM Ge 32948) from Velká nad Veličkou , Czech Republic, Eocene .

Description. —Near-surface, unbranched, cylindrical burrows with a smooth wall and no lining, preserved as positive hyporelief. Course of burrow generally horizontal but un- dulating vertically. Occurring in two different size ranges; the smaller one is about 1 mm wide and preserved over a length of about 30 mm, the larger type has a constant width of about 5 mm and is preserved for lengths between 30 to 80 mm. The latter size variant is more common.

Simple, actively filled (pelletoidal) horizontal to oblique structures

Ichnogenus Tubulichnium Książkiewicz, 1977

Type ichnospecies: Tubulichnium incertum Książkiewicz, 1977 , Gurni- gel Nappe in the Fribourgian Alps, Switzerland, Maastrichtian–lower Palaeogene .

Remarks. —Originally described as Tubotomaculum García-Ramos, Mángano, Buatois, and Rodríguez-Tovar, 2014 , the ichnogenus was considered a junior synonym of Tubulichnium Książkiewicz, 1977 , by Uchman and Wetzel 2017) and its only ichnospecies Tubotomaculum mediterranensis García-Ramos, Mángano, Buatois, and Rodríguez-Tovar, 2014 , was transferred to Tubulichnium by Uchman and Wetzel (2017).

Tubulichnium mediterranensis ( García-Ramos, Mángano, Buatois, and Rodríguez-Tovar, 2014)

Fig. 4 .

Material. —In the field, about 200 observed, usually partially preserved specimens, derived from the Zoophycos Bed ; 113 collected (owing to the large number of specimens, inventorying was done in lots: MZM Ge 32958 (figured herein), MZM Ge 32959 (not figured) from Velká nad Veličkou, Czech Republic, Eocene.

Description. —All Tubulichnium mediterranensis specimens were observed in mid-tier position within the Zoophycos Bed as horizontal, unbranched burrows with no obvious con- nection to the surface. The burrows have a fairly straight to slightly winding course and blind endings. The diameter of the burrows is fairly constant in the range of 4.4 to 13.5 mm, but irregular swellings occur along the burrow. The burrows are lined with elongated, small, 1 mm long and 0.4 mm wide, silty pellets consisting of material derived from the overlying siltstone layer. The maximal preserved length is 60 mm. Larger burrows of probably higher ichnogenic stages display a spindle-like morphology and often retrusive, vertical spreiten with oblique lamellae. Burrows are often colour-enhanced by manganese- or/and iron-rich oxides.

Remarks.— Tubulichnium mediterranensis is relatively common in Cretaceous to Eocene strata in the Mediterranean and occurs according to García-Ramos et al. (2014) often in association with Rotundusichnium zumayensis Plička, 1989 , Zoophycos isp., Chondrites isp., Gyrophyllites isp., and Stelloglyphus llicoensis Le Roux, Nielsen, and Henríquez, 2008 . Other occurrences are restricted to the Miocene of Borneo ( Seilacher 2007; García-Ramos et al. 2014). Tubulichnium was interpreted by Uchman and Wetzel (2017) to represent a sequestrichnion.

Stratigraphic and geographic range. —Upper Cretaceous to Miocene ( García-Ramos et al. 2014); probably worldwide.

Figures

Fig. 4. Simple, actively filled (pelletoidal) horizontal to oblique structure Tubulichnium mediterranensis (García-Ramos, Mángano, Buatois, and Rodríguez-Tovar, 2014), from Velká nad Veličkou, Czech Republic, Eocene. A. Field photo of in situ specimens. B–E. MZM Ge 32958, partially preserved burrows with clearly visible spindle-like shape and pelletal infill. Same specimens from different angles (B1 and B2; C1 and C2). Scale bars 10 mm.