Evolution of Vertebrate Reproduction
Evolution of Vertebrate Reproduction: Reproductive Structures and Embryos in Placoderms
The Linnean Society of London,
Burlington House, Piccadilly,
02074344479 EXT 11
18:00 - 19:00 Thursday 21 January 2016
Placoderms (the armoured fossil fish Eastmanosteus, shown here) are an important group of fishes, because they challenge our established ideas regarding the evolution of reproduction, and the body structures involved. For example, male sharks have a set of claspers developed from the pelvic fin, used for sperm transfer and internal fertilization in the female. More generally, fish reproduce via external fertilization, and this was thought to be the more primitive condition for fish and vertebrates in general. Placoderms represent the most primitive of jawed vertebrates, and they were thought, for the most part, to reproduce externally. However, new research is showing that, instead, many placoderms (males) have bony structures for sperm transfer, accompanied by embryos in the female. Our new data overturns previous suggestions that external fertilization is primitive (seemingly a simpler type of reproductive strategy), and is in fact, the derived condition among vertebrates; the putatively more complex strategy of internal fertilization primitive for jawed vertebrates.
Dr Zerina Johanson FLS is a Researcher in the Department of Earth Sciences, and Head of the Vertebrates and Anthropology Division, Natural History Museum, London. Her research focuses on the evolution and development of early vertebrates, with projects involving the evolution of dentition, evolution of the vertebrate skeleton and reproduction. She is particularly interested in groups such as the placoderms and sharks, and has done extensive fieldwork in Australia, where she obtained her Ph.D.
This meeting is free and open to all; registration is not necessary. Tea and coffee will be served in the Library from 17:30 and a wine reception will follow. Image: Wikimedia Commons/Ghedoghedo @the AMN