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

Abstract

A morphometric analysis of the characteristic whorl cross-sections of 1,200 Jurassic ammonoid species from southern Germany enabled us to characterise their morphospace. The successive Jurassic ammonoid faunas of southern Germany show characteristic patterns in morphospace occupation. While Early and Middle Jurassic ammonoids occupy limited areas of the morphospace range, the Late Jurassic ammonoids cover the entire spectrum. The ammonoids are characterised by an overall increase of both taxonomic diversity and morphological disparity in the course of the Jurassic. Strong fluctuations occur until the middle Late Jurassic, followed by a diversity decrease in the early Kimmeridgian and a disparity reduction in the early Tithonian. While diversity and disparity show similar progression during most of the Early Jurassic, they diverge subsequently and show only poor correlation until the end of the Jurassic. Particularly in the Middle Jurassic diversity and sea level changes correlate strongly. Neither temporal patterns in diversity nor disparity support the hypothesis of a mass extinction event in the early Toarcian. Significant changes in diversity and disparity in the early Callovian support a putative migration event of Boreal ammonoids into the Tethyan realm. <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.201000016" target="_blank">10.1002/mmng.201000016</a>

Extinction Space-a Method for the Quantification and Classification of Changes in Morphospace Across Extinction Boundaries

“…; Simon et al. , ), demonstrating the high potential of this fossil group for disparity analyses. However, extinction events of ammonoids have been analyzed only rarely (Korn ; Villier and Korn ; McGowan ).…”

“…() showed, the dependence of the SOR on the size of the sample becomes unimportant in large data sets; in the case of the Jurassic ammonoids examined by these authors, data sets larger than 100 species were shown to be insensitive to sample size. The SOR is also very sensitive to outliers (morphologically distant singular taxa), which represent species with deviating morphology but that do not play an important role in the composition of the analyzed community (Smith and Bunje ; Deline ; Simon et al. , ). Another critical point is the shape of morphospace; in a principal components analysis (PCA), the axes may be rotated with the introduction of few data points, leading to changes in the length of the axes, and thus also in the SOR. Changes in the SOR are often rather easy to interpret.…”

“…Here we propose an alternative method based on work by Simon et al. (, ), which uses three easily calculated disparity indices to determine if selective extinction occurred. We then use simulations to demonstrate that the mode of extinction plays a major role in determining changes in disparity.…”

Taxonomic Diversity and Morphological Disparity of Paleozoic Ammonoids

“…These three cardinal conch parameters have a pronounced effect on the overall conch form, and it is for this reason that they are often used to express morphospaces either in the form of bi-plots or Principal Components Analysis (PCA). An analysis of measurements and their ratios taken from the last intact whorls of ammonoids allows researchers to track any significant changes in the distribution of the data points within a morphospace over time (e.g., Saunders and Swan 1984;Dommergues et al 2001;Klug et al 2005;McGowan 2007;Moyne and Neige 2007;Saunders et al 2008;Simon et al 2010Simon et al , 2011.…”

New remains ofMachimosaurus hugiivon Meyer, 1837 (Crocodilia, Thalattosuchia) from the Kimmeridgian of Germany

“…Am Haernle Quarry, Neuffen, Baden-Wçrttemberg, Germany. Ataxioceras hypselocyclum Zone (Weisser Jura g 2), Lower Kimmeridgian, Late Jurassic (see Simon et al 2011). Specimen found by E. Schlipf in 1974 and prepared by P. Riederle.…”