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Table 7 States of four abiotic factors correlated with age midpoint (average of ages of the beginning and the end of the corresponding stages after international chronostratigraphic chart from stratigraphy.org) and septal slope factor of ontogenetic trajectory of septal thickness through the Mesozoic. Palaeoenvironmental data are from Berner (2006): CO2, Demicco et al. (2005): Mg/Ca ratio, [Ca2+] (mol mol−1), and Ridgwell (2005): Sea surface pH

From: Is the relative thickness of ammonoid septa influenced by ocean acidification, phylogenetic relationships and palaeogeographic position?

Species Age midpoint
(Ma)
Cohen et al. (2013)
Septal slope factor
(this study)
CO2 (ppm)
Berner et al. (2006)
CO2 (ppm)
Berner et al. (2006)
Mg/Ca ratio
(mol mol−1)
Demicco et al. (2005)
[Ca2+] (mol mol−1)
Demicco et al. (2005)
Sea surface pH
Ridgwell (2005)
Desmoceras 105.5 0.0078 1650 1033.87 0.6 5.15 7.55
Cleoniceras 105.5 0.0028 1650 1033.87 0.6 5.15 7.55
Gaudryceras 105.5 0.0124 1650 1033.87 0.6 5.15 7.55
Argonauticeras 105.5 0.0107 1650 1033.87 0.6 5.15 7.55
Eogaudryceras umbilicostriatus 106.75 0.004 1700 1033.87 0.6 5.15 7.55
Divisosphinctes 154.3 0.0037 2430 693.66 1.45 3.5 7.62
Macrocephalites compressus 168.8 0.0041 2430 875.22 1.45 3.5 7.62
Ludwigia 172.2 0.0024 2200 963.28 1.51 3.3 7.62
Staufenia 172.2 0.0004 2200 963.28 1.51 3.3 7.62
Leioceras 176.5 0.001 1950 963.28 1.52 3.25 7.6
Dactylioceras 178.4 0.0027 1800 963.28 1.53 3.2 7.57
Lytoceras 187.7 0.0067 1650 645.87 1.9 2.9 7.54
Asteroceras 195.05 0.0019 1550 870.46 2.4 2.5 7.52
Arietites 195.05 0.0012 1550 870.46 2.4 2.5 7.52
Fuciniceras 195.05 0.0064 1550 870.46 2.4 2.5 7.52
Schlotheimia 196.1 0.0036 1500 870.46 2.45 2.45 7.52
Psiloceras planorbis 200.3 0.0047 1100 870.46 2.7 2.3 7.58
Psiloceras naumanni 200.3 0.0034 1100 870.46 2.7 2.3 7.58
Arcestes 222.8 0.0048 700 1216.61 2.7 2.2 7.7
Halorites 226.6 0.0098 750 1216.61 2.6 2.3 7.73
Cladiscites 226.6 0.0147 750 1216.61 2.6 2.3 7.73
Discophyllites 226.6 0.0077 750 1216.61 2.6 2.3 7.73
Megaphyllites 226.6 0.0054 750 1216.61 2.6 2.3 7.73
Monophyllites 226.6 0.0067 750 1216.61 2.6 2.3 7.73
Rhacophyllites neojurensis 226.6 0.0075 750 1216.61 2.6 2.3 7.73