Temporal patterns in disparity and diversity of the Jurassic ammonoids of southern Germany

Morphology represents an important tool in descriptive and analytical biology and particularly in palaeontology. Whereas early studies concentrated on qualitative description of morphological characters, there was a transition in the early 20th century leading to analytical approaches with quantitative elements (Thompson 1917; see also Bookstein 1998). This new exploratory focus called morphometrics contained measurement data (metric values, angles etc.) and was introduced ‘. . .in order to describe changes in morphological characters and their correlation with other variables’ (Adams et al. 2004). Due to the lack of information about morphological characters of a given shape as a whole, a second transition was necessary that focused on shape and occurred in the late 20th century. The establishment of this ‘geometric morphometrics’, allowed the description of the entire shape of an organism or any part of its skeleton or shell and its geometrical features. This was such a big watershed that Rohlf & Marcus (1993) felt obliged to call it a ‘revolution in morphometrics’. Two major methods are the landmark-based analysis and the outline analysis. The first concentrates largely on homologous points in the shape of morphologically similar individuals (Bookstein 1991) and the second provides differences in the form of shape outlines (Ferson et al. 1985). With the aid of these methods it is possible to outline a morphospace containing a broad spectrum of morphological information representing the entire shape. A morphospace divided in space and time allows the observer to identify morphological developments and enables them to compare these developments with ecological and environmental circumstances affecting the evolution of organisms. Since Eldredge & Gould (1972) proposed widespread stasis in fossil taxa, implying alternating phases with different evolution rates, research interest focused more and more on events that evoke such anomalies. Extinction events, which are