Meeting Abstract

P2.111  Tuesday, Jan. 5  How much have raninid crab eyes changed after 94 m.y. of evolution? LUQUE, J*; DOUGLASS, J.K.; JARAMILLO, C.A; Université de Montréal, Département de sciences biologiques, Québec, Canada; Smithsonian Tropical Research Institute, Panamá ; Smithsonian Tropical Research Institute, Panamá ; Smithsonian Tropical Research Institute, Panamá javierluquec@gmail.com

Raninid crabs, commonly known as “frog crabs” are an ancient group of marine crabs with the oldest fossil records extending back to the Cretaceous Period (100 mya). The combination of ancestral and advanced features of raninid crabs and the incomplete preservation of most fossil raninids makes them a phylogenetically controversial group, thus knowledge of primitive raninids is important for understanding taxonomic relationships among the principal crab groups. The functional morphology of fossil and extant raninids indicates they have been well suited to a soft sediment burying lifestyle since their appearance, therefore optical adaptations are expected to be conservative throughout time. Until now, fossil raninid compound eyes possessing preserved facets have not been reported. We describe the compound eyes of fossil specimens which are close to the oldest records of raninids and compare them to optically relevant characteristics of extant genera Raninoides, Notosceles, and Symethis to examine whether such optical features have changed over 94 m.y. The highly preserved fossil raninids used in this study possess unique and primitive features including extremely large eyes relative to extant raninids and at least one fossil possesses a facet type not observed in extant specimens. This comparison could provide insights into the relationships among some primitive lineages of Podotremata Raninoids, providing valuable taxonomic, taphonomic, and paleoecological information, which enhances the understanding of tropical ocean communities during Cenomanian-Turonian times.