Clypeasteridae, L. Agassiz, 1835

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 : 154

Clypeasteridae

In addition to the speciose genus Clypeaster ( Fig. 2a, b ), the clypeasterid genera Ammotrophus ( Fig. 2 c ), Arachnoides ( Fig. 2d, e ), and Fellaster ( Fig. 2f ) were studied. A relatively comprehensive X-ray imaging series of specimens from 4 to 43 mm test length is available for the species Arachnoides placenta . The data reveal no trace of Gregory’ s diverticulum or of any potential precursor of the organ in members of the Clypeasteridae .

Figures

Fig. 2 Absence of Gregory’s diverticulum in the Clypeasteridae (a–f), Laganidae (g–m), Echinocyamidae (n–p), Fibulariidae (q, r), and the miniaturized rotulid Fibulariella (s, t). This figure shows selected X-ray images, virtual MRI sections at the level of the main digestive tract, as well as a drawing and a photograph of dissected specimens. a, b Clypeaster reticulatus (24 mm test length); c Ammotrophus cyclius (35 mm); d, e Arachnoides placenta (27 mm); f Fellaster zelandiae (47 mm); g, h