Male Devonian Antiarch Placoderm Microbrachius

Microbrachius dicki

Placodermi, Antiarchiformes. Asterolepididae

Geological Time: Middle Devonian

Size (25.4 mm = 1 inch): Fossil is 27 mm in length by 25 mm across on 120 mm by 80 mm matrix

Fossil Site: Eday Flagstones, Caithness, Orkney, Scotland

Code: UKF269

Price: Sold

Description: This is a diminutive Antiach known as Microbrachius dicki. The Antiarchs were most likely bottom dwellers whose ventral mouth was well-positioned for feeding on benthic organisms. This taxon is believed to be the first to have abandoned the process of casting eggs and milt into the water for internal fertilization some 385 million years ago. They are believed to have used the roughened pectoral fins to grip each other while the genital plates of the female“ docked” with the L-shaped claspers of the male to allow the transfer of sperm. I have been told that females are collected at a ratio of 15-20:1 versus the males. Whether this is an artifact of preservation or a representation of the actual population in life is not known. I include a photo of a female alongside so you can see the differences. See my other offerings for an example of a Microbrachius dicki female.

Reference: Nature 517,08 Jan 2015, pp 196-199

Also see: Paleozoic Fish Fossils

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