Protoscutellidae, Durham, 1955

Ziegler, Alexander, Lenihan, Jennifer, Zachos, Louis G., Faber, Cornelius & Mooi, Rich, 2016, Comparative morphology and phylogenetic significance of Gregory’s diverticulum in sand dollars (Echinoidea: Clypeasteroida), Organisms Diversity & Evolution (New York, N. Y.) 16 (1), pp. 141-166 : 156

Protoscutellidae

This fossil sand dollar family is here represented by a few specimens pertaining to the two species Periarchus lyelli and Protoscutella mississippiensis . Fragments of Aristotle’ s lantern were seen in all samples, suggesting that the internal organs could still have been in place prior to fossilization.

Echinarachnius parma (8, 10, 12, 16, 20 mm); p † Kewia blancoensis (17 mm); q–s † Kewia marquamensis (6, 10, 12 mm); and t † Scutellaster sp. (19 mm). q–s Modified from Linder et al. (1988). All images show an aboral view with ambulacrum III facing upwards. gd Gregory’ s diverticulum, in intestine, re rectum, st stomach. Scale bar = 1 mm

However, no trace of a sand-filled diverticulum was observed in any of the X-ray images. Unfortunately, the single specimen of P. lyelli measured 67 mm in test length, reducing the likelihood of the presence of a sand-filled diverticulum due to the large size of this specimen.