Size and shape data of Globigerinoidesella fistulosa, Trilobatus sacculifer and intermediate specimens from ODP Site 1115

Planktonic foraminifera are extremely well-suited to study evolutionary processes in the fossil record due to their high-resolution deposits and global distribution. Species are typically conservative in their shell morphology with the same geometric shapes appearing repeatedly through iterative evolution, but the mechanisms behind the architectural limits on foraminiferal shell shape are still not well understood. To understand when and how these developmental constraints can be overcome, we study morphological change leading up to the origination of the unusually ornate species Globigerinoidesella fistulosa. Our results show that the origination of G. fistulosa from the Trilobatus sacculifer plexus involved an amalgamation of three different heterochronic expressions: addition of chambers (hypermorphosis), earlier onset of protuberances (pre-displacement), and steeper allometric slope (acceleration) as compared to its ancestor. We argue that the protuberances unique to G. fistulosa we..., Study species.—Globigerinoidesella fistulosa is a short-ranging morphospecies with a distinct stratigraphic range (Fig. 3). Both its origination and extinction are used as markers in Neogene planktonic foraminiferal biostratigraphy (Wade et al. 2011). Globigerinoidesella fistulosa evolved from the Trilobatus sacculifer plexus in the late Pliocene at 3.33 Ma (King et al. 2020; Raffi et al. 2020) and went extinct in the early Pleistocene at 1.88 Ma, marking the Base of Zone PT1a (Raffi et al. 2020) (Fig. 3). The phylogenetic relationships are well-constrained, and the two morphospecies T. sacculifer sensu stricto (s.s.) and G. fistulosa s.s. are morphologically disparate (Poole and Wade 2019), but intermediate specimens bridge the morphological evolution (Fig. 2) and remain as common as G. fistulosa s.s. throughout the stratigraphic range of G. fistulosa (Poole and Wade 2019). Trilobatus sacculifer persists throughout the stratigraphic range of G. fistulosa  and is still alive today (Wade..., Excel or Google Spreadsheets, # Size and shape data of Globigerinoidesella fistulosa, Trilobatus sacculifer and intermediate specimens from ODP Site 1115

## Description of the Data and file structure

The file titled number_of_chambers_per_specimen.xlsx contains the total number of chambers per specimen of ten individuals of T. sacculifer and intermediate specimens, and 14 specimens of G. fistulosa. Every row contains a single specimen.

The file titled SizeShape_data_sacculifer-fistulosa_individuals.xlsx contains area and curvature data as obtained from 2D images. Every row contains a single specimen.

## Sharing/access Information

Links to other publicly accessible locations of the data: none

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**Version changes**

19-20 December 2024: added sample IDs and ages to the size and shape data of T. sacculifer, G. fistulosa and intermediate specimens. These can be found in the file titled '[SizeShape_data_sacculifer-fistulosa_individuals_with_sam...