Incisoscutum

Live reconstruction

• Gogo Formation ( Australia)

• Incisoscutum ritchiei

Incisoscutum (from Latin incidere " cut ", " dig " and scutum "shield" ) is a genus of extinct placoderms, a group of armored, fish-like vertebrates from the Upper Devonian. It belongs to the group of arthrodires.

The type species I. ritchiei was first described scientifically in 1981.

The holotype comes from the Australian Gogo Formation and is estimated at an age of 365 million years. The fossil is kept under the archive number WAM 03.03.28 at Western Australian Museum in Perth. It has a length of about 10 cm.

2009, the remains of about 5 cm long embryos were discovered in a specimen of I. ritchiei, showing that this Placoderme was viviparous. Also in 2009, was found in a male fossil of I. ritchiei about 6 mm long Klaspern, an erectile copulatory organ. Thus, there is after the embryo finds at the Ptyctodontiden Materpiscis attenboroughi and Austroptyctodus gardineri another proof of reproduction by copulation at Placodermen. Internal fertilization is therefore already emerged very early in the evolution of vertebrates.

Several hundreds world stored in museums specimens were given a long time no evidence dimorphism in Arthrodiren other than this is the case in the related group of the Ptyctodontiden. It was therefore made ​​to the I. ritchiei Fund that were on the pelvic fins Klaspern as long praise for copulation, all the more spectacular.