Devonian Ammonites
The Devonian witnessed the first appearance of the Ammonites as they evolved from bactrites, a straight-shelled nautiloid. The order Clymeniida arose during the Devonian but did not outlast the difficulties of the Devonian Mass Extinction and all signs of this order are gone by the end of the period.
There were three orders of ammonites during this period.
- Anarcestida (the first ammonites)
- Clymeniida
- Goniatitida
The graph below depicts the number of orders that existed through different stages of the Devonian period. Overall there were 225 orders, of which 192 went extinct.
The Late Devonian saw the near extinction of the Ammonites as 150 orders of the existing 153 orders went extinct.
Other data can tell us a great deal about the diversity and relative numbers of orders between the three ammonite groups. See the tables below.
Extant Orders During the Devonian
The Anarcestida were the first order of Ammonites to appear. Their numbers dominated the overall totals of the Devonian, but they were in a competitive race with the other two orders which developed Late in the Devonian: the Clymeniida and Goniatitida.
The Clymeniida had the highest number of genera during the Late Devonian, but were no match for the Extinction that totally destroyed the order.
Origination of Orders During the Devonian
Origination data shows that the Anarcestida remained steady in their ability to diversity throughout the Devonian. The Clymeniida had the highest rate of diversification, only to go extinct by the end of the period. The Goniatidia fell between the other two orders but went on to be a highly successful order.
Extinction of Orders During the Devonian
The number of orders that went extinction throughout the Devonian tells us that there was a significant event during the Late Devonian. We know this as the Devonian Mass Extinction, one of the 5 most extensive extinctions to have ever occurred. Despite these tremendous difficulties when many of the marine animals died, the ammonites were able to survive.
