with and without sand indicate that juveniles grew more rapidly if sand was present. The reason this adaptation is beneficial is because sand dollars with higher growth rates also have higher mortality rates, which suggests that either the larvae did not use a significant amount of lipid energy reserves to survive or that energy reserves are not critical for the survival of the larvae. Another reason this adaptation is beneficial is because newly metamorphosed sand dollars are extremely vulnerable to tube-building predators such as Leptochelia dubia. References Schultz, Heinke (2006) Sea Urchins I: a guide to worldwide shallow water species Heinke + Peter Schultz Partner Scientific Publications ; Sea Urchins Treatise on Invertebrate Paleontology Part U, Volume 2 1966 Mortensen, T. 1948. A Monograph of the Echinoidea IV.2 Clypeasteroida. C. A. Reitzel, Copenhagen. Seilacher A. 1979. Constructional Morphology of Sand Dollars. Paleobiology. 5(3): 191-221 Mooi, R. 2016. Paedomorphosis, Aristotle's lantern, and the origin of the sand dollars (Echinodermata: Clypeasteroida) Paleobiology. 16(1):25-48 Telford M. 1981. A Hydrodynamic Interpretation of Sand Dollar Morphology. Bulletin of Marine Science. 31(3):605-622(18) Highsmith RC, Emlet RB. 1986. Delayed metamorphosis: Effect on growth and survival of juvenile sand dollars (Echinoidea: Clypeasteroida). Bulletin of Marine Science. 39(2):347-361(15). Highsmith RC. 1982. Induced Settlement and Metamorphosis of Sand Dollar (Dendraster Ecentricus) Larvae in Predator‐Free sites: Adult Sand Dollar Beds. Ecology. 63(2) External links Natural History Museum Sepkoski Online Clypeasteroida Extant Piacenzian first appearances Monotypic echinoderm genera Echinoidea genera