Fig. 2

Portions of the dendritic radix structures of the hemicosmitid rhombiferan Caryocrinites and the monobathrid camerate crinoid Eucalyptocrinites from the middle Silurian Massie Formation of the Napoleon quarry (CMC IP82656). Radicles from these two pelmatozoans became interwoven into one composite structure. a. View of the upper surface of the specimen, which has the appearance of a single radicle that is swollen with secondary stereom. Scale bar = 10 mm. b. Cross-sectional (articular) view of the radicles, with the trilobate lumen of Caryocrinites and the pentalobate lumen of Eucalyptocrinites outlined. The uppermost lobe of the pentalobate lumen appears enlarged due to the angle at which this portion of the specimen is fractured. Note also that the Caryocrinites radicle has a circular outline, in contrast to the more irregular outline of the Eucalyptocrinites radicle. Scale bar = 5 mm. c. Close-up view of some of the branches off of the main axis of the radicles. Those belonging to Eucalyptocrinites are characterized by minute pentalobate lumina, whereas those belonging to Caryocrinites are solid, undifferentiated rods of stereom lacking lumina. Scale bar = 2 mm