Description of a Well Preserved Fetus of the European Eocene Equoid Eurohippus messelensis.

Jens Lorenz Franzen,Christine Aurich,Jörg Habersetzer,Andrew A Farke

doi:10.1371/journal.pone.0137985

Abstract

The early Middle Eocene locality of Grube Messel, near Darmstadt (Germany), is famous for its complete vertebrate skeletons. The degree of preservation of soft tissues, such as body silhouettes, internal organs and gut contents, is frequently remarkable. The present specimen was analyzed for remnants of the reproductive system. Classic anatomy and osteology and high-resolution micro-x-ray were applied to describe the fetus of the European Eocene equoid Eurohippus messelensis. Scanning electronic microscopy (SEM) was used for determination of soft tissue remnants. The fetus is the earliest and best-preserved fossil specimen of its kind. The postcranial fetal skeleton is almost complete and largely articulated, allowing the conclusion that the pregnant mare was in late gestation. The apparent intrauterine position of the fetus is normal for the phase of pregnancy. Death of mare and fetus were probably not related to problems associated with parturition. Soft tissue interpreted as the uteroplacenta and a broad uterine ligament are preserved due to bacterial activity and allow considerations on the evolutionary development of the structures.

Highlights

The fossil record of mammals is often restricted to isolated teeth and bones
Koenigswald determined the species as Propalaeotherium parvulum, which was subsequently synonymized with Eurohippus messelensis [4,5]
Franzen has described a comparable case of a fossilized pregnant mare of the equoid Propalaeotherium voigti from the Middle Eocene Maar of Eckfeld, which showed “a hard undulated bright-grey crust enwrapping the bones of a fetus” [17]

Summary

Introduction

The fossil record of mammals is often restricted to isolated teeth and bones. Less than 2% of localities with fossil mammals have yielded anything more than fragments of jaw material and other bones [1, 2]. Fetus of the Eocene Equoid Eurohippus messelensis uteroplacenta is taken from Fig 3a. Fetus of the Eocene Equoid Eurohippus messelensis caput articulates proximomedially with the glenoid cavity of the left scapula, which is situated between the ribs of the left and the internal uterine wall on the right side, so that most of it is hidden.

Results

Conclusion