Early Jurassic dinosaur fetal dental development and its significance for the evolution of sauropod dentition

Robert R Reisz,Shiming Zhong,Thomas W Dudgeon,Timothy Huang,Diane Scott,Chuan-Mu Chen,Aaron R H Leblanc,Hillary C Maddin,Jun Chen

doi:10.1038/s41467-020-16045-7

Abstract

Rare occurrences of dinosaurian embryos are punctuated by even rarer preservation of their development. Here we report on dental development in multiple embryos of the Early Jurassic Lufengosaurus from China, and compare these to patterns in a hatchling and adults. Histology and CT data show that dental formation and development occurred early in ontogeny, with several cycles of tooth development without root resorption occurring within a common crypt prior to hatching. This differs from the condition in hatchling and adult teeth of Lufengosaurus, and is reminiscent of the complex dentitions of some adult sauropods, suggesting that their derived dental systems likely evolved through paedomorphosis. Ontogenetic changes in successive generations of embryonic teeth of Lufengosaurus suggest that the pencil-like teeth in many sauropods also evolved via paedomorphosis, providing a mechanism for the convergent evolution of small, structurally simple teeth in giant diplodocoids and titanosaurids. Therefore, such developmental perturbations, more commonly associated with small vertebrates, were likely also essential events in sauropod evolution.

Highlights

Rare occurrences of dinosaurian embryos are punctuated by even rarer preservation of their development
The anatomy and histology of embryonic teeth of derived sauropodomorph and ornithischian dinosaurs have been studied[10,11], but we currently lack a good understanding of dinosaur tooth development at the earliest ontogenetic stages in other groups
Patterns of tooth development at the initial stages of ontogeny in some of the earliest known dinosaurs are important for reconstructing the evolutionary history of teeth in a clade of tetrapods that demonstrates extreme dental variation, and includes some of the most complex dentitions in history[12,13]

Summary

Introduction

Rare occurrences of dinosaurian embryos are punctuated by even rarer preservation of their development. Comparing the Lufengosaurus embryos with the teeth of a 1-day-old Alligator hatchling (Fig. 3) revealed similar patterns of tooth development, where successive generations of teeth occupy a single large crypt with no intervening jaw or socket bone tissues.

Results

Conclusion