Fig. 11

Stereom biocorrosion in columnals from Tuilerie de Gan bed 6 (Late Ypresian). a Eocenocrinus hessi n. gen., n. sp. (syntype A, MNHN.F.A69341, same specimen as in the Fig. 6a, b), stereom without biocorrosion, facet surface of columnals articulated when collected, washed under ultrasound; b Democrinus londinensis (Forbes, 1852) (specimen B, MNHN.F.A69337, same specimen as in Fig. 3d–g) isolated columnal, galleried stereom in ligament area, thin biocorroded layer removed by washing under ultrasound (arrows: broken or altered stereom indicating lower boundary of biocorrosion, stereom preserved as in A below this surface); c Paraconocrinus romanensis (Roux and Plaziat 1978) (specimen E, MNHN.F.A69334, same specimen as in Fig. 5a), biocorroded stereom partly coated by micrite, external columnal surface in contact with clay, soft washing without ultrasound; d: Paraconocrinus romanensis (specimen B, MNHN.F.A69328, same specimen as in Fig. 3a, b) close up on biocorroded stereom (arrow: window showing hollow framework); e, f Eocenocrinus hessi (syntype B, MNHN.F.A69342, same specimen as in Fig. 6e, f), highly biocorroded columnal (same ossicule in Fig. 6e, f); e flaky appearance of eroded external surface; f external surface with all angles smoothed. Scale bars: a–d = 10 µm, e, f = 1 mm