Are placoderms vertebrates or invertebrates?

Are placoderms vertebrates or invertebrates?

Placoderms were among the first of the jawed fish and were dominant vertebrates in the Devonian.

When did the placoderms go extinct?

Sharks and possibly placoderms and acanthodians are thought to have been present (Blieck, 2003). Placoderms are known from the early Silurian (about 430 million years ago) and disappeared at the end of the Devonian (about 360 million years ago).

What killed the placoderms?

It was thought for a time that placoderms became extinct due to competition from the first bony fish and early sharks, given a combination of the supposed inherent superiority of bony fish and the presumed sluggishness of placoderms.

What is the taxonomy of Placodermi?

Taxonomy and phylogeny. Currently, Placodermi are divided into eight recognized orders. There are two further controversial orders: One is the monotypic Stensioellida, containing the enigmatic Stensioella; the other is the equally enigmatic Pseudopetalichthyida.

What are the characteristics of placoderms?

Their head and thorax were covered by articulated armoured plates and the rest of the body was scaled or naked, depending on the species. Placoderms were among the first jawed fish; their jaws likely evolved from the first of their gill arches.

Are placoderms herbivores or planktivores?

Some placoderms were herbivorous, such as the Middle to Late Devonian arthrodire Holonema, and some were planktivores, such as the gigantic, 8 m (26 ft) long arthrodire, Titanichthys . 1⁄2 in) offspring and was fossilized with the umbilical cord intact.

What do placoderm braincases have in common with fish?

Placoderms also possess a support for the eye called the eyestalk similar to a structure in sharks (Long, 1995). Placoderm braincases possessed a number of structures shared among jawed fish such as the position of several arteries, the pathways of nerves, and perhaps the jaw articulation (Maisey, 2005).