Measured vs. recorded ammonoids: a curated Paleobiology Database dataset for assessing the temporal coverage of ammonoid measurement data (Devonian–Cretaceous)

This dataset compares two parts of the Paleobiology Database (PBDB) for ammonoids: the specimens that have measurement data, and the full occurrence record. It is curated for testing how evenly the measurement data cover ammonoid species through time, from the Devonian to the Cretaceous (about 420–66 million years ago). It combines two PBDB downloads, both accessed in September 2026: Measured specimens: 20,272 records covering 5,316 species. Occurrences: 64,733 species-level records covering 11,547 species from 25,740 collections and 2,524 references. The original downloads contain more than 120 columns each. This dataset keeps only the fields needed to link specimens to occurrences and to place them in time and taxonomy: identifiers, accepted names, order, family, genus, age bounds, source references, and, for specimens, type status and how the measurement was obtained. Several derived fields were added: the midpoint age of each record and the geological period it falls in; a flag for heteromorphs (ammonoids with uncoiled or partly uncoiled shells), classified at family level; whether each species has at least one measured specimen; a species-level summary table with occurrence counts, collection counts, and measured-specimen counts. No records were removed during curation. The data are provided as a single Excel workbook with six sheets: a README, the species summary, the specimens, the occurrences, the list of heteromorph families, and the period boundaries. The README gives the exact PBDB query URLs and access dates, column definitions, and caveats. The dataset lists which specimens were measured, not the measured values themselves. Those can be retrieved from the PBDB measurements service and joined on specimen_no. This dataset supports the preprint [title, DOI to be added]. That study found that measurement coverage declines from about 76% of species in the Permian to about 28% in the Cretaceous, a pattern that holds after equalizing sampling across periods. It also found that heteromorph species are almost entirely unmeasured. Source data © Paleobiology Database contributors, released under CC0 1.0; this curated dataset is also released under CC0 1.0. Please cite both the Paleobiology Database and this dataset when using it.