Ichnospecies Teredolites longissimus and Teredinid Body Fossils from the Early Eocene of India—Taphonomic and Palaeoenvironmental Implications

Abstract

Extensively bored log-grounds with ichnospecies Teredolites longissimus and body fossils of the causative teredinid molluscs are recorded from the Early Eocene subsurface beds of the Cambay Shale Formation at Vastan lignite Mine in western India. Three sizes of T. longissimus observed in Vastan mostly represent animals in different stages of maturity or successive infestation of substrate. Orientation of a majority of small borings suggests that teredinid larvae preferred to initiate boring across the wood grain and subsequently turned to become parallel to grain exhibiting adult boring behavior. Variations in morphology of recovered shells indicate involvement of at least two teredinid taxa in constructing T. longissimus from Vastan—one is identified as Bankia isp. based on pallets and the other remains unidentified and may possibly represent another bankiine, Nototeredo. Evidences of traumatic as well as attritional mortality are noticeable. The xylic substrates having affinity with woods of a modern tree genus Aglaia (Meliaceae) were apparently transported from their natural habitat of an inland moist tropical forest to the coastal region where they were colonized by the teredinid bivalves. The profusely infested wood logs were buried in a near shore lagoon or a tidal flat setting, which is corroborated by the known biota (vertebrate, invertebrate as well as plants) as well as sedimentary facies of the Cambay Shale Formation in Vastan section.

Keywords:

• Log-grounds
• Teredolites
• Bankia
• Teredinidae (Mollusca)
• Cambay Shale Formation
• Early Eocene
• Vastan Lignite Mine
• India

ACKNOWLEDGMENTS

The authors would like to thank the two anonymous reviewers and Dr. M. K. Gingras, Editor, Ichnos, for their constructive and helpful comments on our manuscript. We thank Prof. Ashok Sahni (Panjab University) for encouragement and advice during the progress of this work and Drs. Mahesh Prasad and J. S. Guleria (BSIP, Lucknow) for comments on the fossil wood. KK thanks Dr. Jiří Kříž (Czech Geological Survey, Praha) and Dr. Simon Cragg (University of Portsmouth, UK) for their helpful comments on the material, Dr L. N. Santhakumaran (Institute of Wood Science and Technology, Bangalore) and Dr. Charles Savrda (Auburn University, Alabama) for constructive suggestions and for providing some of the relevant literature, and the Director, Wadia Institute of Himalayan Geology, Dehradun, for supporting field and laboratory studies. HS is thankful to the Director, Birbal Sahni Institute of Palaeobotany, Lucknow, for providing the necessary facilities. RSR thanks the DST, Government of India, for financial support.