Video at Nature.com
--- UPDATE ---
PZ Myers has this to say ...
The media is getting another science story wrong. I keep seeing this discovery of an array of fossil placoderms as revealing the origins of sex, and that's not right. Sex is much, much older, and arose in single-celled organisms. Come on, plants reproduce sexually. A fish is so far removed from the time of origin of sexual reproduction that it can't tell us much about its origins.
Let's get it right. These fossils tells us about the origin of fu…uh, errm, mating in vertebrates.