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1 November 2016 Star-shaped trace fossil and Phymatoderma from Neogene deep-sea deposits in central Japan: probable echiuran feeding and fecal traces
Kentaro Izumi, Kazuko Yoshizawa
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Abstract

A co-occurrence of the ichnogenus Phymatoderma and a star-shaped horizontal trace fossil was discovered from Neogene deep-marine deposits (Misaki Formation, central Japan), and is described herein for the first time. Phymatoderma consists of a straight to slightly curved tunnel that shows first- or second-order branches. The tunnels are 5.30–27.25 mm in diameter and are filled with ellipsoidal pellets. The relatively well-preserved star-shaped trace fossil is a large horizontal structure (∼18 cm × 19 cm) that consists of at least 10 spokes with diameters ranging from 11.49–20.96 mm. As compared to modern analogous surface-feeding traces produced by abyssal echiuran worms and their burrow morphology, it is highly likely that the star-shaped trace fossil and Phymatoderma found from the Misaki Formation are feeding and fecal traces of ancient deep-sea echiurans, respectively. Difference in preservation potential between surface and subsurface traces may result in rare occurrence of star-shaped trace fossils as compared to Phymatoderma. Microscopic observation of the pelletal infill of Phymatoderma also reveals that the trace-maker fed on organic debris and microorganisms such as diatoms and radiolaria.

© 2016, The Paleontological Society
Kentaro Izumi and Kazuko Yoshizawa "Star-shaped trace fossil and Phymatoderma from Neogene deep-sea deposits in central Japan: probable echiuran feeding and fecal traces," Journal of Paleontology 90(6), 1169-1180, (1 November 2016). https://doi.org/10.1017/jpa.2016.95
Accepted: 1 December 2014; Published: 1 November 2016
JOURNAL ARTICLE
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