Interactive comment on "Physiology regulates the relationship between coccosphere geometry and growth-phase in coccolithophores" by Rosie M. Sheward et al. Rosie M. Sheward et al.sheward@em.uni-frankfurt.de Received and published: 24 January 2017 We kindly thank both reviewers for their positive, insightful and constructive comments on our manuscript and we are pleased that the manuscript was considered to be wellwritten, clearly structured and accessible to non-specialists, with well-reasoned rationale and a high-quality dataset. We have carefully considered all comments and suggestions and hope that we have satisfactorily addressed each point raised. The main points that we have addressed are as follows (see details in specific responses):Applicability and significance of work: Both Reviewers questioned how common the occurrence of coccospheres is in the fossil record and therefore how broadly applicable our results may be. Our wider research demonstrates that coccospheres are uncom-C1 BGD Interactive commentPrinter-friendly version Discussion paper mon but not so rare (documented from a range of ages, ocean basins and latitudes) that our approach would only be applicable in very few cases. We have now emphasised our comments on applicability in the introduction, discussion and conclusions.Correction of Table to report growth rates and minimum, mean and maximum coccosphere geometry for Exponential-phase and Non-exponential-phase days separately to complement the 'full dataset' coccosphere geometry summarised in Table 1.Growth phase, growth rate and fitness comments: We have carefully considered the comments of Reviewer #1 concerning interpreting growth information in the fossil record based on growth phase results rather than growth rate results. In light of specific comments, we have adjusted our phrasing for clarity and to avoid misleading word choices in several places (Ln 67-68; Ln 368; Ln 375-379). We have also added additional comments in the discussion on the value of other experimental approaches in addressing growth rate and coccosphere geometry in future investigations to further advance our work.Statistical methods: We have added a 'Statistical Methods' sub-section to the Methods following the suggestion of Reviewer #2, including bootstrap analysis of our linear regression analysis, which we agree improves the high quality of our extensive dataset.