Data from: Patterns of intraspecific variation through ontogeny–a case study of the Cretaceous nautilid Eutrephoceras dekayi and modern Nautilus pompilius

<p>The magnitude and ontogenetic patterns of intraspecific variation can provide important insights into the evolution and development of organisms. Understanding the intraspecific variation of organisms is a key to correctly pursuing studies in major fields of palaeontology. However, intraspecific variation has been largely overlooked in ectocochleate cephalopods, particularly nautilids. Furthermore, little is known regarding the evolutionary pattern. Here, we present morphological data for the Cretaceous nautilid <i>Eutrephoceras dekayi</i> (Morton, 1834) and the modern nautilid <i>Nautilus</i> <i>pompilius </i>Linnaeus, 1758<i> </i>through ontogeny. The data are used to describe the change of conch morphology and to elucidate the evolutionary patterns of intraspecific variation. We discovered the presence of morphological changes at hatching and maturity, which is shared in every conch parameter in <i>E. dekayi</i> and <i>N. pompilius</i>. We also found that intraspecific variation is high in early ontogeny in both taxa, followed by various patterns in later ontogeny. The high variation in early ontogeny may imply their flexibility of changing the timing of growth events, which may have played an important role in nautilid evolutioin. We assume that the decrease in variation in later ontogeny may indicate developmental constraints. Lastly, we compared the similarity/dissimilarity of ontogenetic patterns of variation between taxa. Results reveal that the similarity/dissimilarity of the ontogenetic pattern differs between <i>E. dekayi</i> and <i>N. pompilius</i>. We conclude that this shift in the ontogenetic pattern of variation may be rooted in changes in the developmental program of nautilids through time. We propose that studying ontogenetic patterns of intraspecific variation can provide new insights into the evolution and development of organisms.         </p>