DOI: 10.5061/dryad.pq70h50
title: Data from: Ion microprobe measured stable isotope evidence for ammonite habitat and life mode during early ontogeny

description: Ammonites have disparate adult morphologies indicative of diverse
 ecological niches, but ammonite hatchlings are small (~1 mm diameter),
 which raises questions about the similarity of egg incubation and
 hatchling life mode in ammonites. Modern Nautilus is sometimes used as a
 model organism for understanding ammonites, but despite their outward
 similarities, the groups are only distantly related. Trends in ammonite
 diversity and extinction vulnerability in the fossil record contrast
 starkly with those of nautilids, and embryonic shells from Late Cretaceous
 ammonites are two orders of magnitude smaller than nautilid embryonic
 shells. To investigate possible environmental changes experienced by
 ammonite hatchlings, we used secondary ion mass spectrometry (SIMS) to
 analyze the oxygen and carbon isotope composition of the embryonic shells
 and early postembryonic whorls of five juveniles of Hoploscaphites
 comprimus obtained from a single concretion in the Fox Hills Formation of
 South Dakota. Co-occurring bivalves and diagenetic calcite were also
 analyzed to provide a benthic baseline for comparison. The oxygen isotope
 ratios of embryonic shells are more like those of benthic bivalves,
 suggesting that ammonite eggs were laid on the bottom. Ammonite shell
 immediately after hatching has more negative δ18O, suggesting movement to
 more shallow water that is potentially warmer and/or fresher. After
 approximately one whorl of postembryonic growth, the values of δ18O become
 more positive in three of the five individuals, suggesting that these
 animals transitioned to a more demersal mode of life. Two other
 individuals transition to even lower δ18O values that could suggest
 movement to nearshore brackish water. These data suggest that ammonites,
 like many modern coleoids, may have spawned at different times of the
 year. Because scaphites were one of the short-term K-Pg survivors, it is
 possible that this characteristic allowed them to develop a broader
 geographic range and, consequently, a greater resistance to extinction.
description: SI 6 d18 O SIMS
 tableExcel file of SIMS
 analyses on samples and standards for large and small δ18O analysis spot
 sizes. Column descriptions are included in the file as a
 footer.SI 6
 d18 O SIMS total table.xlsxSI 7 d13 C SIMS
 tableExcel file containing
 all SIMS analyses on samples and standards for δ13C. Column descriptions
 are included in the file as a footer.SI 7 d13 C SIMS total
 table.xlsxSI 8 Phos acid isotope
 micromillResults from gas-source
 mass spectrometry conducted at Isolab – University of
 Washington.Figure SI 9 Beanplot O
 CBeanplot showing the
 distribution of d18O and d13C measurements grouped by method (SIMS vs
 phosphoric acid digestion gas source mass spectrometry [Phos]) and
 material (ammonite = Am, bivalve = Bi, diagenetic infill =
 D).Figure SI 10 Crossplot O
 CCrossplots of d18O and
 d13C from SIMS and gas source mass spectrometry measurements. Calculated
 aragonite values are shown for d18O of material that was calcite. Points
 are coded by material, method, and mount. Pairing SIMS d18O and d13C was
 done by distance along shell.SI 11 Tukey HSD
 contrastsExcel file summarizing
 the Tukey's Honestly Significant Differences test for multiple
 contrasts of the equality of mean d18O values. Analysis conducted in R
 using TukeyHSD() Multiple contrasts are conduced within each individual
 mount by comparing the embryonic (E), varix (V), first whorl (1), and
 second whorl (2).SI 1 J 125 Sample
 mapFlat summary map of
 J-125 sample surface with reflected light and scanning electron microscopy
 imagery overlain. Individual SIMS pits are annotated with the file name.
 Point locations are colored points near the visible SIMS pit images.
 Navigation of this page can be done by zooming in or searching the PDF for
 individual pit file names. Higher resolution images of pits are available
 upon request.SI 2 J 145 Sample
 mapFlat summary map of
 J-145 sample surface with reflected light and scanning electron microscopy
 imagery overlain. Individual SIMS pits are annotated with the file name.
 Point locations are colored points near the visible SIMS pit images.
 Navigation of this page can be done by zooming in or searching the PDF for
 individual pit file names.SI 3 J 209 Sample
 mapFlat summary map of
 J-209 sample surface with reflected light and scanning electron microscopy
 imagery overlain. Individual SIMS pits are annotated with the file name.
 Point locations are colored points near the visible SIMS pit images.
 Navigation of this page can be done by zooming in or searching the PDF for
 individual pit file names. Higher resolution images of pits are available
 upon request.SI 4 J 215 Sample
 mapFlat summary map of
 J-215 sample surface with reflected light and scanning electron microscopy
 imagery overlain. Individual SIMS pits are annotated with the file name.
 Point locations are colored points near the visible SIMS pit images.
 Navigation of this page can be done by zooming in or searching the PDF for
 individual pit file names.SI 5 J 273 Sample
 mapFlat summary map of
 J-273 sample surface with reflected light and scanning electron microscopy
 imagery overlain. Individual SIMS pits are annotated with the file name.
 Point locations are colored points near the visible SIMS pit images.
 Navigation of this page can be done by zooming in or searching the PDF for
 individual pit file names. Higher resolution images of pits are available
 upon request.