Fig. 4

New specimens of Helenodora inopinata from the Francis Creek Shale, Westphalian D, Middle Pennsylvanian. a, b FMNH PE13966, part and counterpart. c, d FMNH 33380, part and counterpart. e, f FMNH PE33822, part and counterpart. g FMNH PE45049. h FMNH PE49784. Photographed wet under cross-polarised light. a, Specimen preserves complete anterior, defined by a constriction of the body outline (con), bearing frontal appendages (ant) as well as limbless posterior extension (pos) of the trunk. Ruptured body wall (rup) with putative escaped decaying tissues. Numbers refer to walking limbs from anterior to posterior (b). Putative dermal papillae (“pap”) visible both inside and outside of body wall. In all images, white or pale regions of the fossil correspond to a clay-filled (kaolinite) cast defining the overall morphology of the animal. Bright white patches on the surface of the nodules are caused by concentrations of kaolinite, not reflections or other artefacts associated with the photographic methods. The darker patches, which preserve details of external anatomy, are moulds of external anatomy preserved as siderite with patchy framboidal pyrite. The similarity of patches to features such as jaws (e.g. large dark patch at one end of (g)), is coincidental. Scale bar = 10 mm. High resolution versions of each photograph provided in additional materials (Additional file 4)