Brachiopoda: Fossil Record

The above chart is called a spindle diagram. This sort of diagram is used by the paleontologist to gain an understanding of how diverse a group of organisms has been through geologic time. On one axis of the chart is time, from the Cambrian at the bottom to today at the top. The bars indicate how many different kinds of brachiopod fossils that have been found by paleontologists during each time period.

Look at the spindle diagram. What does it tell you?

Well, it tells you that brachiopods were most diverse during the Devonian period. The widest bar represents just over 200 different genera that have been found for that time. The chart also shows you that the brachiopods were much more diverse and numerous during the Paleozoic era, which corresponds to the periods Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. Between the Permian and the Triassic there is a drastic drop in the number of brachiopods. In fact, the fossil records of many animal groups show this enormous die off, giving the boundary the following name: The Permo-Triassic mass extinction. This was the largest of all extinction events, killing nealy 90 percent of all species alive at the time. The diagram also shows you that brachiopods have never been as diverse since that event.

Fossil Range Chart of Brachiopods

The chart below shows you the ranges of the fossil records for each of the different brachiopod groups. There are three groups alive today, the Lingulata, the Rhynchonellida and the Terebratulida. Again, you can see that more of the groups lived during the Paleozoic than during more recent times.

The above chart is mapped. You can go directly to each of the major brachiopod groups.

Source: Gould, S.J. and Calloway, C.B. 1980. Clams and brachiopods--ships that pass in the night. Paleobiology 6(4), 383-396.