Eggshell and Histology Provide Insight on the Life History of a Pterosaur with Two Functional Ovaries.

Xiaolin Wang,Taissa Rodrigues,Xi Meng,Xin Cheng,Juliana M Sayão,Qiang Wang,Alexander W A Kellner,Fabiana R Costa,Shunxing Jiang,Zhonghe Zhou,Ning Li

doi:10.1590/0001-3765201520150364

Abstract

The counterpart of a previously described non-pterodactyloid pterosaur with an egg revealed the presence of a second egg inside the body cavity of this gravid female. It clearly shows that pterosaurs had two functional oviducts and demonstrates that the reduction of one oviduct was not a prerequisite for developing powered flight, at least in this group. Compositional analysis of one egg suggests the lack of a hard external layer of calcium carbonate. Histological sections of one femur lack medullary bone and further demonstrate that this pterosaur reached reproductive maturity before skeletal maturity. This study shows that pterosaurs laid eggs even smaller than previously thought and had a reproductive strategy more similar to basal reptiles than to birds. Whether pterosaurs were highly precocial or needed parental care is still open to debate.

Highlights

Information about the reproductive biology of extinct animals is hard to be retrieved from the fossil record, if suitable modern analogs are not available
Wang et al (2014) reported five exceptionally well-preserved eggs associated with hundreds of pterosaur bones from Hami, located in the Xinjiang Uyghur Autonomous Region of China, and a tridimensionally preserved egg was retrieved from the Lagarcito Formation and referred to Pterodaustro guinazui (Grellet-Tinner et al 2014)
The first was previously reported in the main slab (Lü et al 2011a) where it is preserved as an impression, while the most complete part remained on the counter slab (IVPP V18403)

Summary

INTRODUCTION

Information about the reproductive biology of extinct animals is hard to be retrieved from the fossil record, if suitable modern analogs are not available. The specimen ZMNH M8802/IVPP V18403 was originally referred to the wukongopterid Darwinopterus (Lü et al 2011a) without proper justification since this non-pterodactyloid group has proven to be rather diverse (Wang et al 2009, 2010, Lü et al 2011b) The skull of this pterosaur is partially preserved in the counter slab as an impression and confirms that this specimen lacks a premaxillary crest (Lü et al 2011a). The first was previously reported in the main slab (Lü et al 2011a) where it is preserved as an impression, while the most complete part remained on the counter slab (IVPP V18403) This egg is positioned on the left side of the specimen, immediately posterior to the pelvis, partially overlapping the tail, and can be distinguished from the brownish sedimentary matrix by its whitish-grey coloration. Estimated dimensions Initial egg mass Hatchling mass corrected for compaction (g) (IEM)

Findings

DISCUSSION

CONCLUSION