Start Who is ben mckenzie dating

Who is ben mckenzie dating

The anapsid and synapsid reptiles were common during the late Paleozoic, while the diapsids became dominant during the Mesozoic. The later radiations, such as those of fish in the Silurian and Devonian periods, involved fewer taxa, mainly with very similar body plans.

Fish do not represent a monophyletic group, but a paraphyletic one, as they exclude the tetrapods.

Fish, like many other organisms, have been greatly affected by extinction events throughout natural history.

Vertebrates, among them the first fishes, originated about 530 million years ago during the Cambrian explosion, which saw the rise in organism diversity. Pikaia had a primitive notochord, a structure that could have developed into a vertebral column later.

Unlike the other fauna that dominated the Cambrian, these groups had the basic vertebrate body plan: a notochord, rudimentary vertebrae, and a well-defined head and tail.

Lampreys belong to the Cyclostomata, which includes the extant hagfish, and this group may have split early on from other agnathans.

The first jawed vertebrates probably developed during the late Ordovician period.

Although a minor element of modern marine fauna, jawless fish were prominent among the early fish in the early Paleozoic.