So One Ancient Fish Says to Another, "You Wanna Put What Where?"

In the U.S., how do we teach kids about sex? The birds and the bees, of course. But we should teach them about the fishies too, according to new research on 380-million-year-old pregnant fish that pushes back the date for the earliest example of internal fertilization by about 30 million years.

As was recently published in the journal Nature, two specimens of Incisoscutum ritchiei, a fish that swam in the waters that once covered what is now Australia, died with smaller fish in their bellies.

Fossil (NHM)

One fossil comes from the Gogo formation of western Australia—
image shamelessly boosted from the BBC article linked below

One of the fossilized remains was first discovered in the 1980s, and assumption had long been that the smaller fish was the larger’s last meal. But then researchers looked at a male Incisoscutum ritchiei and realized it had a pelvic fin on its stomach similar to ones modern sharks have.

Called a clasper, it would have been used by the male to grip the female during mating. It is “an intermittent erectile organ that is inserted inside the female to transfer sperm,” co-author Dr John Long, a palaeontologist at Museum Victoria in Australia, told the BBC. (Intermittent erectile organs are now treatable with medicine. But anyway.)

Internal fertilization is one of the processes that distinguishes some fish and virtually all mammals from reptiles and amphibians.

I doubt this was tender love. It was probably more gladiatorial, considering that placoderms, the class of fish this one belonged to, were covered in a formidable fish armor that in at least one other species extended over a hooked clasper. (Ow!) In contrast, Incisoscutum ritchiei’s clasper was formed of soft cartilage. For her, a tender mercy at least.

The development of internal fertilization went on long before our own class, mammalia, arose on the scene; the earliest mammals didn’t appear until about 100 million years after Incisoscutum ritchiei. We are only most distantly related to this potential pioneer of nookie.

And yet internal fertilization is so key to all human cultures. What aspects of our traditions, laws and arts aren’t in some way related to when, where and how who gets internal with whom?

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