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The miniature echinoid trace fossil Bichordites kuzunensis isp. nov. from early Oligocene prodelta sediments of the Mezardere Formation, Gokceada Island, NW Turkey

Demircan H., Uchman A.

Acta Geologica Polonica

2012

Vol. 62, no. 2

205-215

The pascichnial trace fossil Bichordites kuzunensis isp. nov. occurs as an epichnial complex structure in early Oligocene prodelta sediments of the Thrace Basin in Gokceada Island, northwest Turkey. It displays characteristics of irregular echinoid burrows such as overall shape and a double meniscate filling with a chevron dorsal suture, in addition to the feature typical of the so far monospecific Bichordites Plaziat and Mahmoudi, 1988, that is a single central core around a single drainage tube. Its miniature size can be related to the small size of the tracemaker (ontogenic feature) or to its dwarfism in a stressed deltaic environment (palaeoecological feature). Its occurrence indicates a period of fully marine conditions during accumulation of the deltaic sediments of the Mezardere Formation.

Kiss of death of a hunting fish : trace fossil Osculichnus labialis igen. et isp. nov. from late Eocene - early Oligocene prodelta sediments of the Mezardere Formation, Thrace Basin, NW Turkey

Demircan H., Uchman A.

Acta Geologica Polonica

2010

Vol. 60, no. 1

29-38

The trace fossil Osculichnus labialis igen. et isp. nov. occurs as hypichnial pairs of uneven bilobate mounds in early Oligocene prodelta sediments of the Thrace Basin. Osculichnus is generally elliptical or crescentic in outline and has two lip-like lobes: a smaller and a larger one, which are separated by an undulate furrow. Herein, it is interpreted as a hunting trace (praedichnion) of a fish penetrating a surficial sand layer and into an underlying mud horizon. The fish hunted for small endobenthic bivalves and perhaps other invertebrates such as polychaetes. Penetration into surficial mud rather than sand resulted in poorly preserved variants of this trace fossil, whose median furrow is commonly not visible. The probability of fish trace makers is supported by experiments.