As Nigel departs for the surface, he explains that the placoderms as a whole have a grim future ahead of them.
32.
They became extinct at the end of the Devonian period that also claimed the Placoderms and most other jaw-less fish.
33.
""'Wuttagoonaspis " "'is a genus of primitive arthrodire placoderms from Middle Devonian Australia.
34.
The first lobe-finned bony fish appeared in the Devonian, while the placoderms began dominating almost every known aquatic environment.
35.
In another twenty million years, the entire Class of placoderms will disappear, much to the other Devonian fish's relief.
36.
This would have allowed the placoderms to invest more time and energy in producing and nurturing fewer, but more developed, offspring.
37.
Spiny sharks did not diversify as much as placoderms, but survived much longer into the Early Permian about 290 million years ago.
38.
The vertebrate jaw probably originally evolved in the Silurian period and appeared in the Placoderm fish, which further diversified in the Devonian.
39.
Recent studies indicate that Osteichthyes evolved from placoderms like " Entelognathus ", while acanthodians are more closely related to modern chondrichthyes.
40.
Inversely, ptyctodontids are now considered to be the most derived of placoderms, being ancestral and forming a gradient to modern jawed vertebrates.
