Behavioural variants of the trace fossil Gyrochorte
نویسندگان
چکیده
The trace fossil Gyrochorte is common in Upper Jurassic siliciclastic rocks of the Kachchh Basin, western India. In the Kimmeridgian Katrol Formation, Gyrochorte comosa Heer, 1865 is tied to storm-generated fine-grained sandstones and exhibits an internal structure composed of double arches in cross-section, confirming the three-dimensional nature of the trace fossil and its interpretation as produced by a deposit-feeder moving obliquely through the sediment. In the Tithonian to Lower Cretaceous Umia Formation, Gyrochorte occurring in thin-bedded, ripple-laminated medium-grained sandstones displays a range of morphological features connected with the sideway exploitation of the substrate (formation of fans) and variations in the degree to which the producer occupied an upright or forward inclined position within the sediment. The morphological expressions of these behavioural variants are subsumed in the new ichnospecies Gyrochorte variabilis.
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