1. Matthew E. Clapham University of California, Santa Cruz mclapham@ucsc.edu Disparity trends in the shell coiling shape of ammonoids

2. Ammonoid coiling geometry From Korn & Klug, 2012 The coiled shells of ammonoid cephalopods have evolved a huge array of geometric shapes

3. Ammonoid morphometrics Villier & Korn, 2004 Saunders et al., 2008 The regular geometric shapes of ammonoid shells make them well suited for morphometric studies to examine trends in disparity over their evolutionary history and across important events Saunders & Swan 1984; Dommergues et al., 1996 ; Saunders et al. 2004, 2008; McGowan 2004, 2007; Villier & Korn 2004; Korn & Klug 2012; Brosse et al. 2013, etc.

4. Ammonoid measurements Traditional parameters of whorl width (W) and height (H), umbilical diameter (U), and diameter Principal components analysis of W/D, H/D, and U/D ratios Modified from Brosse et al., 2013

5. Heteromorph ammonoids Heteromorph ammonoids have uncoiled whorls or deviate from planispiral coiling form, so cannot reasonably be quantified with W/D, H/D, or U/D measurements and are excluded

6. Ammonoid morphospace Morphospace defined by axes from evolute to involute coiling (U/D and H/D) and from compressed to depressed whorl widths (W/D) 8515 specimens 2687 species

7. Morphospace occupation Areas of morphospace occupation and degree of morphological variability differed widely among time intervals

8. Disparity trends in shell coiling Pennsylvanian-Permian peak Guadalupian-Lopingian drop Jurassic-Cretaceous low

9. Taxonomic contributions

10. Shape variation among orders Post-Paleozoic and especially post-Triassic disparity is reduced because ceratites and especially ammonites are increasingly restricted to a narrow region of the morphospace Globular shells (high W/D) are common among goniatites but extremely rare among ammonites

11. Ammonoid size Average shell volume increased by more than an order of magnitude from Paleozoic to the Jurassic

12. Ammonoid size On average, ammonites were ~10 times as large as goniatites Perhaps globular morphotypes are unfeasible at large size?

13. Size and shell shape Highly globular shells were more common among small goniatites, but globular ammonites tended to be large

14. Competitors? Perhaps other groups (heteromorph ammonites or non-ammonite taxa like crustaceans or fish) were occupying the ecological role formerly occupied by globular goniatites?

15. Phytoplankton and food web dynamics Post-Paleozoic shift from prasinophytes to bloom-forming phytoplankton (dinoflagellates, nannoplankton) (Falkowski et al., 2004) Perhaps altered the nature of food webs to favor groups with different ecological strategies? Acritarchs Prasinophytes Dinoflagellates Calcareous nannoplankton Diatoms

16. Conclusions 1.Ammonoids peaked in the diversity of coiling morphologies (excluding heteromorphs) in the late Paleozoic 2.Major decline during Guadalupian-Lopingian transition and never recovered Paleozoic levels of disparity 3.Jurassic and Cretaceous ammonites had low coiling disparity because they rarely evolved the globular morphotypes common in goniatites 4.Loss of globular morphotypes may have resulted from other groups occupying those niches or from loss of that niche altogether due to post-Paleozoic food web restructuring

17. Ammonoid shell web app https://mclapham.shinyapps.io/ammonShape/ Make your own plots of PCA results by taxon and time interval

18. Acknowledgments All of the ammonoid measurements used here are in the PBDB Jeanette Sullivan (2013) and Jocelynn Morales (2014) for data entry R code at: https://github.com/mclapham/ammonShape These slides and ammonite measurements at: http://figshare.com/authors/Matthew_Clapham/593028 PBDB data enterers, especially: Me, Wolfgang Kiessling, Austin Hendy You too can make data useful with the PBDB!