Rotulidae, Gray, 1855

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 : 155

Rotulidae

Data were available for the three rotulid genera Heliophora , Rotula , and Rotuloidea as well as the closely related Fibulariella . The three extant species Fibulariella acuta ( Fig. 2s, t ), Heliophora orbicularis ( Fig. 3a, b ), and Rotula deciesdigitatus ( Fig. 3c–e ) do not possess Gregory’ s

Jacksonaster depressum (28, 32 mm); i, j Laganum laganum (28 mm); k, l Peronella lesueuri (26 mm); m Peronella orbicularis (21 mm); n, o Echinocyamus pusillus (5.5, 5 mm); p Mortonia australis (13 mm); q Fibularia ooulum (5.5 mm); r Fibularia nutriens (11 mm); and s, t Fibulariella acuta (6.5, 7 mm). r Modified from Clark (1909). All images show an aboral view with ambulacrum III facing upwards. go gonad, in intestine, re rectum, st stomach. Scale bar a–m = 5 mm and n–t = 1 mm

diverticulum. The available data suggest the same for the fossil genus Rotuloidea , although several of the X-rayed specimens were missing Aristotle’ s lantern. Relatively comprehensive Xray imaging series are available for the extant species H. orbicularis (6–78 mm) and for the fossil Rotuloidea (11– 40 mm). These data further support the conclusion that rotulids as well as Fibulariella do not possess Gregory’ s diverticulum.

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

Fig. 3 Absence of Gregory’s diverticulum in the Rolutidae (a–e) as well as presence and shape of the organ in the Taiwanasteridae (f–j) and Echinarachniidae (k–t). The figure shows selected X-ray images. a, b Heliophora orbicularis (15, 46 mm test length); c–e Rotula deciesdigitatus (17, 22, 50 mm); f–j Sinaechinocyamus mai (1.5, 3.5, 6, 6.5, 7.5 mm); k–o