Hillichnus agrioensis and Associated Trace Fossils from Hettangian to Bajocian Thaiat Member of Lathi Formation, Jaisalmer Basin, Western Rajasthan

The present paper describes the abundant and very well preserved ichnotaxon complex Hillichnus agrioensis , as established by four different morphological levels of exposures. Associated trace-fossils such as Jamesonichnites heinbergi and Ancorichnus ancorichnus are also being reported from the Hettangian to Bajocian Thaiat Member of Lathi Formation of Jaisalmer basin, western Rajasthan, India. The ichnospeices Hillichnus agrioensis is being documented for the first time in India. Morphologically, Hillichnus agrioensis includes straight to gently curved, branched or feather-like (almost flat) structures with a central tube. It is interpreted as a deep-burrowing bi-siphonate or tellinaceans bivalves. The ichnotaxon Jamesonichnites heinbergi is interpreted as a burrow made by an infaunal deposit-feeder (fodinichnion), while Ancorichnus ancorichnus is domichnion and may also solely be the result of locomotion (repichnion). This study suggests the presence of shallow or marginal-marine environment for the above-mentioned trace-fossil bearing horizons as trace-fossils characterized by such features have also been found from other parts of the world.