{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

The Ordovicia2 - animal phyla this is the only phylum that...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
The Ordovician The Ordovician period representes the period of geologic time between 505 to 440 million years ago. Following the extinctions at the close of the Cambrian period, diversification occurred among the survivors. Corals become dominant reef-building animals during the Ordovician, and continue their importance today. Bryozoans and algae were also dominant elements of the reef building biota. Trilobites, which had survived the end of the Cambrian, continued, but were not as dominant in the environment as they had been. The Ordovician is noteworthy because of the moves some green algae made toward the shoreline, and possibly onto land, becoming the first plants. Interesting animals of the period include the conodonts (thought to represent early vertebrates) and graptolites. The first fish also evolved. Bryozoans are a group of organisms sometimes referred to as "moss animals". They form colonies, often consisting of millions of individuals. There are nearly 5000 living species and a great many more taxa known from the fossil record. Among invertebrate
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: animal phyla, this is the only phylum that does not have representatives appearing during the Cambrian. Brachiopods were present (although not major organisms in the environments) during the Cambrian, but after the Cambrian extinction, they underwent an adaptive radiation in the Ordovician. Brachiopods have bilaterally symmetrical shells, which make them among the most common marine fossils in Paleozoic rocks. Traditionally brachiopods were divided into articulate and inaticulate groups, depending on the presence or absence (respectively) of a hinge between the halves of the shell. The earliest brachiopods were inarticulated, and lacked that hinge. Lingula is an example of this type, with fossils very similar to that genus being found in Cambrian rocks, and persisting even today. Systematics of the brachiopods has been under intense revision lately, and the traditional split of the two groups may not in fact be a natural characteristic useful in taxonomy....
View Full Document

{[ snackBarMessage ]}

Page1 / 2

The Ordovicia2 - animal phyla this is the only phylum that...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon bookmark
Ask a homework question - tutors are online