This widely distributed genus comprises three species, all found in Australian waters. Species undertake vertical migrations to feed in mesopelagic waters.
Ocean sunfish, the largest bony fishes in the world, have a very deep, oblong to almost circular body, with tall dorsal and anal fins and a small rounded pectoral fin. They have a rudder-like structure or clavus (from the Latin clavus, = rudder) instead of a caudal fin. Their thick skin is covered with rough textured denticles. Molids also have a small rounded mouth with fused teeth forming a plate in each jaw.
Britz, R. & Johnson, G.D. 2005. Occipito-vertebral fusion in ocean sunfishes (Teleostei: Tetraodontiformes: Molidae) and its phylogenetic implications. Journal of Morphology266: 74–79. https://doi.org/10.1002/jmor.10366
Johnson, G.D. & Britz, R. 2005. Leis' conundrum: Homology of the clavus of the ocean sunfishes. 2. Ontogeny of the median fins and axial skeleton of Ranzania laevis (Teleostei, Tetraodontiformes, Molidae). Journal of Morphology 266(1): 11-21 https://doi.org/10.1002/jmor.10242
Nyegaard, M., Sawai, E., Gemmell, N., Gillum, J., Loneragan, N.R., Yamanoue, Y., Stewart, A.L. 2017. Hiding in broad daylight: molecular and morphological data reveal a new ocean sunfish species (Tetraodontiformes: Molidae) that has eluded recognition. Zoological Journal of the Linnean Society 182(3): 631-658 https://doi.org/10.1093/zoolinnean/zlx040
Yoshita, Y., Yamanoue, Y., Sagara, K., Nishibori, M., Kuniyoshi, H., Umino, T., Sakai, Y., Hashimoto, H. & Gushima, K. 2009. Phylogenetic relationships of two Mola sunfishes (Tetraodontiformes: Molidae) occurring around the coasts of Japan, with notes on their geographical distribution and morphological characteristics. Ichthyological Research 56: 232–244. https://doi.org/10.1007/s10228-008-0089-3