Biology : Semester II


IntroductionSection 1 | Section 2 | Section 3 | Section 4 | Section 5

  Section Three:

Part 1 | Part 2 | Part 3 | Part 4 | Part 5 | Part 6 | Part 7 | Part 8 | Part 9 | Part 10 | Part 11 | Part 12 | Part 13 | Part 14

Biology : The Time of Ancient Life : Part Eleven

The Carboniferous:
Coal Swamps and Glaciers

The Carboniferous period (360 to 286 million years ago) in Europe is better known in North America as the Mississippian period and the Pennsylvanian period. The early Carboniferous equates to the Mississippian, and the late Carboniferous will represent the Pennsylvanian.

The Carboniferous forests produced tremendous biomass which, when buried, eventually turned into massive coal deposits of the age.

The Carboniferous takes its name from the widespread occurrence of coal deposits formed during this time span in Europe and North America. Coal is a sedimentary rock composed of plant debris (and occasionally material from other creatures) that was deposited in a bog or swamp that had little biological activity at its bottom. This led to preservation of the plant leaves, stems, pollen and other structures, although with continued burial these structures become much less distinct. Time and pressure combine with chemical changes to turn the plant material into coal. Fluctuating sea levels during the Carboniferous contributed to the preservation of many coal environments.

Life in the Water

The marine environments, following the rebound from the late Devonian mass extinction underwent changes, with crinoids becoming more dominant and diverse. The early Carboniferous is sometimes known as the "age of crinoids".  More “modern” ray-finned fish replaced armored Devonian fish during this time.


Fenestrate bryozoans were particularly common in the early Carboniferous seas. Archimedes, a corkscrew-shaped fossil, represents the secreted support of a colony of bryozoans that are usually no longer present.  The so-called lacy bryozoans were among the first invertebrate groups to recover after the Devonian extinction.

Brachiopods became increasingly important animals. The spiriferids that began their diversification during the Devonian quickly recovered from the Devonian die-off and resumed or increased their ecological dominance during the early Carboniferous.

Corals were much restricted after the Devonian crisis and the large reefs of the Devonian were replaced with smaller reefs known as patch reefs. The role of corals in these new reefs was much reduced from what it had been in earlier times. Crinoids were also important contributors to the building of these small reefs, as were blastoids, a similar group of echinoderms.

Foraminiferans, a group of unicellular protozoans that date from the Cambrian, developed a new series of forms with calcareous and porcellaneous tests (foram "shells" are technically known as tests). The fusulinids were a large group of foraminiferans that reached sizes of several centimeters in length. The fusulinids were very important during the Permian before their extinction at that period's close.


Sharks and bony fish continued to diversify during the good times of the early Carboniferous, before the dropping sea levels of the late Carboniferous caused loss of habitat. The earliest bony fish to dominate the aquatic environment were the palaeoniscoids, a group that raged in time from the Carboniferous to the Triassic. Palaeoniscoids somewhat resembled modern bony fish but had significant anatomical differences with modern fish, which belong to a later-evolved group. The palaeoniscoids were extinct by the end of the Mesozoic era. Sturgeon are members of a distantly related group to the palaeoniscoids. Sturgeon have a cartilage skeleton and thus a poor fossil record.

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