Species of placoderms anatomy

rows · Various placoderm species, including the famous Dunkleosteus. This list of placoderms . The extinct armored fishes known as placoderms make up what is considered to be the earliest branch of the gnathostome family tree — the earliest branch of the jawed fishes. Placoderms bore heavy bony armor on the head and neck, often with an unusual joint in the dorsal armor between the head and neck regions; this joint apparently allowed the head to move upwards as the jaw dropped downwards, . Class Placodermi (placoderms) †Extinct; fishlike; jaws supported by both cranium and hyoid arch (amphistylic); partly ossified cranium; primitive; head and trunk have armour that is jointed at the neck; pelvic fins present or absent; pectoral fins or finlike structures often present; gill arches. Class Chondrichthyes (sharks,.

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Species of placoderms anatomy Placoderm bony plates were generally made up of three layers, including a compact basal lamellar bony layer, a middle spongy bony layer and a superficial layer; Bothriolepis can be classified as a placoderm since it possesses these layers. Placoderms were extinct by the end of the Devonian. Only one known species of Romundina has been discovered which was named Romundina stellina by Ørvig. The species name stellina refers to stellate (derived from Latin word stella meaning star) tubercles that the Placoderm has ornamenting its dermal skeleton. Romundina stellina is one of the earliest known acanthothoraciforms discovered to date. Placoderms (class Placodermi “tablet or plate skin”) were heavily armored jawed fish that range from the Silurian to the Devonian. Armored Jawed Fish Placoderms reached their greatest diversity during the Devonian, often referred to as the “Age of Fish”, and were in fact the dominant fish group during this time (Prothero, , p. ).

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