Zoophycos Massalongo, 1855

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 : 772-774

Ichnogenus Zoophycos Massalongo, 1855

Type ichnospecies: Zoophycos brianteus Massalongo, 1855 , Livorno , Tuscany ( Italy), Upper Cretaceous .

Zoophycos brianteus Massalongo, 1855

Fig. 7A 1 .

Material. —Three nearly complete specimens from the Zoophycos Bed ( MZM Ge 32960, MZM Ge 32961; Z 69) from Velká nad Veličkou, Czech Republic, Eocene.

Description. —The three studied, almost complete specimens exhibit the typical spreite of Zoophycos helically coiled around a vertical axis. Both sinistral and dextral helices were observed, and the structures were constructed from top to bottom. The spirals’ diameters increase down- ward. The first has a nearly circular outline, the second is rather oval, and the last one is slightly lobate. The largest diameters of the three specimens measure 139 mm, 167 mm, and 225 mm respectively. They penetrate from the top of the Zoophycos Bed for about 150 mm with a total height of the Zoophycos spreite whorls of about 40 mm each. In vertical sections, each spreite-whorl is bent concave upwards with both limits (marginal tunnel and contact at the centre) being roughly at the same level. The thickness of the spreite increases from 2.8 mm at the top whorl to up to 6.4 mm as a maximum. This maximal thickness is already reached about halfway through the burrow’s vertical extension. From there on, the spreite thickness does not increase further. An inner, not bioturbated area with a subcircular cross-section is present having a diameter 7.6–8.5 mm. A central shaft has not been observed. In all specimens, the marginal (unlined) tunnel is well developed as well as primary and secondary lamellae of the spreite. The maximal distance between two subsequent primary lamellae increases from the top to the bottom of the helix. On the surfaces of the whorls, faecal pellets have been observed. They have an elongate ellipsoidal to slightly ovoid or capsule-like shape. Their size is fairly constant in all specimens; ranging 0.8–1.4 mm in length and 0.4–0.5 mm in width. With depth protrusion, these faecal pellets increase in size.

Remarks. —Olivero (2007) redescribed the specimens of the three proposed Zoophycos -species by Massalongo, 1855. He selected lectotypes and a new type ichnospecies of Zoophycos since the originally designated type ichnospecies constitutes rather a fossil alga than a trace fossil (Olivero 2007). The studied specimens match with the redescription of Zoophycos brianteus by Olivero (2007).

In general, two ways of construction exist in Zoophycos , from top to bottom or from bottom to top. This can be inferred by the convex side of the lamellae within the spreite ( Olivero and Gaillard 1996). According to the findings by Olivero and Gaillard (1996, 2007), the bottom to top mode of building seems to be more common but the (lecto-)type material of Zoophycos brianteus ( ICN 1, ICN 2, ICN 3, ICN 4) seems to be constructed from top to bottom (see Olivero 2007).

For the studied specimens, ichnogenetic stages ( Belaústegui et al. 2016) are transitional but a growth of the tracemaker during construction can be inferred owing to increases of spreite thickness, diameter of the whorls, pellet size, dimensions of the marginal tunnel etc. (cf. Kotake 1989). The tracemaker seems to have reached adult size before the structure was completed.

All specimens exhibit a continuous spreite with mixture of silty material and pellets ( Fig. 7A 3 ) indicating an active downward-movement of overlying more nutritious material into the nutrition-poor Zoophycos Bed. The deposition of faecal pellets within the structure points towards a sequestration behaviour (cf. Uchman and Wetzel 2016, 2017). The tracemaker purposely stowed material in order to either re-digest it or to utilise it indirectly by consuming microbes cultivated on it or their processed compounds. The same behaviour by a Recent Zoophycos -tracemaker was observed by Wetzel et al. (2011).

Some individual coils of the largest specimen are cross-cut by younger shafts of an undetermined trace fossils with a diameter up to 10 mm ( Fig. 7A 2 ). On the spreite surfaces, several specimens of Chondrites intricatus ( Fig. 7A 4 ) and minute circular shafts (diameter less than 1 mm) occur Fig. 7B ).

Stratigraphic and geographic range —Lower Permian to Recent ( Hu et al. 2010); worldwide.

Burrows with shaft or bunch with downwards radiating probes

Ichnogenus Chondrites Sternberg, 1833

Type ichnospecies: Chondrites targionii ( Brongniart, 1828) , locality and age unknown.

Chondrites intricatus ( Brongniart, 1823)

Fig. 7A 4 .

Material. — 12 specimens on the surface of the above mentioned Zoophycos brianteus specimens ( MZM Ge 32960, MZM Ge 32961; Z 69), 3 isolated specimens observed in sediment (collected in situ from the Zoophycos Bed ) from Velká nad Veličkou, Czech Republic, Eocene.

Description. —Regularly branching, small, dendritic burrow systems covering an area of up to 90 mm 2, with numerous minute branches, less than 1 mm in diameter, usually preserved in close contact with both upper and lower surfaces of Zoophycos spreite/whorls; isolated occurrence of Chondrites intricatus in the surrounding claystone is rare.

Remarks. —All above described Zoophycos brianteus specimens are pierced by minute vertical shafts filled with pyrite having a diagenetic halo ( Fig. 7B ). The diameter of these shafts is in the same size-range as the diameter of the individual branches of Chrondrites intricatus (less than 1 mm). Thus, these shafts may represent connections of the branched section of Chondrites with the ancient water-sediment interface.

Stratigraphic and geographic range —Lower Silurian ( Rindsberg and Chowns 1986) to Recent; worldwide.

Figures

Fig. 7. Zoophycos brianteus Massalongo, 1855, with Chondrites intricatus (Brongniart, 1823). A. MZM Ge 32960, from Velká nad Veličkou, Czech Republic, Eocene.A1, bottom two coils of Z. brianteus, arrows mark specimens of Ch. intricatus; A2, cylindrical structure penetrating a Z. brianteus spreite;A3, pellets on the surface of the spreite;A4, Ch. intricatus on the surface of a spreite. B. MZM Ge 32961, from Velká nad Veličkou, Eocene, minute shafts cross-cutting a Z. brianteus spreite, note the diagenetic halo around the shafts.

Fig. 1. Location of the studied area in Europe (A) and the Czech Republic (B). Schematic map of the studied locality (C).

Fig. 3. Simple horizontal trail Helminthopsis tenuis Książkiewicz, 1968, MZM Ge 32946, from Velká nad Veličkou, Czech Republic, Eocene.

Fig. 2. Stratigraphic position of the Zoophycos Bed in the southern part of the studied locality.

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.