Data from: Star-shaped trace fossil and Phymatoderma from Neogene deep-sea deposits in central Japan: probable echiuran feeding and fecal traces

Co-occurrence of the ichnogenus Phymatoderma and star-shaped horizontal trace fossil was discovered from the Neogene deep-marine deposits (Misaki Formation, central Japan), and were described herein for the first time. Phymatoderma consists of 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 (approximately 18 × 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 the star-shaped trace fossils as compared to Phymatoderma. Microscopic observation of the pelletal infill of Phymatoderma also revealed that the trace-maker actually fed on organic debris and microorganisms such as diatoms and radiolaria.