|Ammonites in 1991|
Donovan, D.T. (1993). Ammonites in 1991, in: House, M.R. (Ed.) The Ammonoidea: environment, ecology, and evolutionary change. pp. 1-11
In: House, M.R. (Ed.) (1993). The Ammonoidea: environment, ecology, and evolutionary change. The Systematics Association Special Volume, 47. Clarendon Press: Oxford. ISBN 0-19-857765-6. 353 pp., more
In: The Systematics Association Special Volume, more
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VLIZ: Geology and Geophysics 
Advances of knowledge since the Second World War are reviewed. A great increase in the number of researchers worldwide has led to a great increase in systematic descriptions of ammonoid faunas which were previously unknown or undescribed. Sexual dimorphism is generally accepted, and taken into account by most systematists. Knowledge of mode of life has greatly increased. We have a good idea of how ammonites controlled buoyancy and what their depth limitations were. We know what their buccal apparatus was like. However, there are still big gaps in our understanding. We do not know how they swam, what their food was, or how they caught it. Many evolutionary sequences have been described, but we have little or no idea of their significance in adaptive terms. There are still major problems.