DOI: 10.5061/dryad.k9b14
title: Data from: Intraspecific variability through ontogeny in early ammonoids

description: Mollusks in general and ammonoids in particular are known to display a
 sometimes profound morphological intraspecific variability of their shell.
 Although this phenomenon is of greatest importance, it has rarely been
 investigated and quantified. It is especially crucial for taxonomy and
 incidentally for biodiversity analyses to account for it, because
 otherwise, the number of described species might exceed that of actual
 species within any group. Early ammonoids (Early Devonian, Paleozoic)
 typically suffer from this bias. For instance, most specimens from the
 same layer and the same region (e.g., the Erbenoceras beds of the Moroccan
 eastern Anti-Atlas studied here) differ morphologically from each other.
 Depending on the importance given to certain morphological characters,
 therefore, one could create a new species for almost every specimen. In
 this study, we measured nearly 100 such specimens from a restricted
 stratigraphic interval and quantified their intraspecific variability.
 There is a variable but strong overlap of the quantified shell characters
 at most ontogenetic stages, and only two species are here separated rather
 than the four previously recognized in Morocco. When ontogenetic
 trajectories of the Moroccan specimens are compared with coeval faunas
 from other regions (assigned to other species), a strong overlap between
 the morphospaces occupied by these taxa becomes apparent. The
 justification of some of these latter species is thus questionable even if
 their mean values in some conch parameters differ considerably from the
 mean values of the Moroccan species. Hence, the number of currently valid
 species of these loosely coiled early ammonoids is probably much too high.
 Extreme caution must therefore taken when examining the diversity of
 groups in which the intraspecific variability is poorly known.
description: Supplementary
 AppendixFurther explanations
 concerning the localities and taxonomy used in this paper. It also
 contains the additional references cited in the supplementary material,
 but not in the main text.DeBaets_etal_SupplementaryAppendix.docSupplementary Figure 1A, The study area (enlarged in B) is marked by the rectangle (modified from Klug 2001). B, Geological map showing the early Emsian localities of the eastern Moroccan Anti-Atlas (modified from Klug 2001). Studied specimens derive from the localities marked by a black dot. C, Paleogeographic reconstruction of the Emsian (modified from Scotese 2001) showing known occurrences of Anetoceras, Erbenoceras and other early Emsian ammonoid faunas discussed in the text and the supplementary appendix. References not listed in the main text can be found in the supplementary appendix.SupplementaryFigure1_DeBaetsetal_StratigraphyPaleobiogeography.jpgSupplementary Figure 2Bivariate plots of whorl interspace index WII (A) and whorl expansion rate WER (B) of Group I (black fillings, white lines) and Group II (white fillings, black lines) against diameter. Note the similarity between the graph of WER and whorl height index WHI of Figure 3A. Multiple measurements of the same specimen through ontogeny are connected by a line.SupplementaryFigure2_DeBaetsetal_BivariatePlots2.jpgSupplementary Figure 3Specimens of Group I (“Anetoceras”) and Group II (“Erbenoceras”) arranged according to umbilical width index UWI (A-R) and according to rib per demi-whorl counts (S-AJ) at 70 mm diameter. Note that some of the specimens were mirrored to enhance comparability. All specimens were coated with NH4Cl. All parts exceeding 70 were cut off in the image processing software. Group I has a grey background and Group II has a white background. A, PIMUZ-29653. B, PIMUZ-29656. C, PIMUZ-29637. D, PIMUZ-29652. E, PIMUZ-29643. F, PIMUZ-28430. G, PIMUZ-29636. H, PIMUZ-29792. I, PIMUZ-29789 J, PIMUZ-29783. K, PIMUZ-29806. L, PIMUZ-29797. M, PIMUZ-29779. N, GPIT-1849-2002. O, PIMUZ-29810. P, PIMUZ-29802. Q, PIMUZ-29805. R, PIMUZ-29815. S, PIMUZ-29637. T, PIMUZ-29656. U, PIMUZ-29653. V, PIMUZ-29643. W, PIMUZ-29652. X, PIMUZ-29806. Y, GPIT-1849-2002. Z, PIMUZ-29810. AA, PIMUZ-29797. AB, PIMUZ-29636. AC, PIMUZ-28430. AD, PIMUZ-29779. AE, PIMUZ-29792. AF, PIMUZ-29802. AG, PIMUZ-29789 AH, PIMUZ-29783. AI, PIMUZ-29805. AJ, PIMUZ-29815.SupplementaryFigure3_DeBaets_SpecimensVariability.jpgSupplementary Figure 4Histograms showing (A) the distribution of maximum size (maximum dm) and associated distributions of (B) whorl height index WHI, (C) umbilical width index UWI, (D) whorl interspace index WII, and (E) ribs per half-whorl RDW for all specimens of Group II (“Erbenoceras”). The two peaks at the 70-75 mm bin (falls in the 1.7-1.8 logarithmic size class) and the 90-95 mm bin (falls in the 1.9-2.0 logarithmic size class) are highlighted in black and grey respectively. Note, that there is no clear separation in frequency distribution of the conch or rib spacing parameters at these diameters, which are highlighted in the same colors. The bimodal distribution of the whorl height index WHI probably results from a sampling bias as this peak disappears when all measurements through ontogeny of more complete specimens are also plotted.SupplementaryFigure4_DeBaetsetal_MaxSizeDistribution.jpgSupplementary Table 1Measurements of the Moroccan specimens. Abbreviations localities: AE = Achguig East, BT = Bou Tchrafine, EK = El Kahla, GEA = Gart El Anz, GM = Gara Mdouara, HT = Hassi Tachbit, OCE = Ouidane Chebbi East, QCE = Qued Chebbi East. Abbreviations collectors: DB = Kenneth De Baets, H = Marcus Hebeisen, K = Christian Klug, Ko = Christian Kolb, T = Frank Trostheide, W = Martin Wasmer. Abbreviations levels: C = Unit C of Klug (2001), D = Unit D of Klug (2001). All specimens deriving from a single slab of Unit D (see supplementary appendix) are marked in bold. Additional references cited in the supplementary material, but not in the main text are listed in the supplementary appendix.SupplementaryTable1.xlsSupplementary Table 2Measurements of the specimens from the literature (Erben 1960, 1962; Bogoslovsky 1969; Ruan 1981; Yatskov 1990; Chlupáč and Turek 1983; De Baets et al. 2009). Abbreviations: HT = holotype, LT = lectotype. Additional references cited in the supplementary material, but not in the main text are listed in the supplementary appendix.SupplementaryTable2.xls