Tuesday, 1 April 2014

Novel burrows from the Miocene of Mizoram State, northeast India.

The fossil record comprises not just the physical remains of organisms that have lived and died in past eras of the Earth's history, but also numerous traces left by these organisms. The study of these traces, ichnology, can reveal important data about past ecosystems even where the identity of the trace maker is unknown, as different organisms will often produce similar burrows in response to similar environmental challenges.

In a paper published in the journal PLoS One on 18 October 2013, Raghavendra Tiwari and Chinmoy Rajkonwar of the Department of Geology at Mizoram University and Satish Patel of the Department of Geology at the Maharaja Sayajirao University of Baroda describe a series of novel burrows from the earl-middle Miocene Bhuban Formation at Aizawl in Mizoram State in northeastern India.

The burrows are placed in the ichnogenus Funalichnus (trace fossils are often named in the same way as body fossils, although these names reflect only similarity of form, not an implied relationship between the trace-makers), which has previously been used to name similar burrows from the Late Cretaceous of the Bohemian Basin in the Czech Republic, and given the specific name bhubani, which is derived from the formation in which it was found.

Funalichnus bhubani is a vertical or nearly vertical burrow, straight, unbranching and smooth with an oval profile, split into a number of cylindrical segments oblique to the long axis. The lower part of the burrow tapers rather than stopping abruptly. The burrows are considerably larger than similar burrows previously seen in the Bohemian Basin (and named Funalichnus strangulatus) reaching 120-200 mm in length and 10-36 mm in diameter, whereas the largest Bohemian trace was only 51 mm in length.

Funalichnus bhubani  specimens from the from the Bhuban Formation at Aizawl in Mizoram State. Tiwari et al. (2013).

The burrows were found in a grey, fine-to-medium grained sandstone which was heavily bioturbated with numerous other, better studied, burrows, as well as ripple marks, cross bedding and other sedimentary structures. This is interpreted as having a shifting, unconsolidated sandbed near to a shore.

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