Question

What does the agnathans group include?

Answer 1

AGNATHANs are 'jaw less' vertebrates: gnathos in Greek means jaw. They were the first vertebrate to evolve in early Palaeozoic, more than 500 million years ago.

Explanation:

Superclass Agnatha is included under phylum Chordata, subphylum Vertebrata.

Very few living agnathans are present today, all are aquatic.

There is a single living class Cyclostomata, that includes all living agnathans.

Class Cyclostomata includes two members:

Hag fish/ Myxine

and

Lamprey/ Petromyzon.

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Most of extinct Agnathans are referred to as Ostracoderm : a group of fish like organisms whose head was protected by a bony shield.

Most agnathans were extinct by the end of Paleozoic.