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

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.

Seven remarkable new fossil species of parasitoid wasps (Hymenoptera, Ichneumonidae) from the Eocene Messel Pit

“…The vertebrate fossils comprise mainly fishes [ 26 ]. Other vertebrates are much rarer, but they provide important insights into the former terrestrial ecosystem, like reptiles [ 27 , 28 ], birds [ 29 , 30 ], and mammals [ 16 , 31 ]. Invertebrates, especially insects, document a very high biodiversity [ 20 , 21 , 32 , 33 ], as do the plants [ 34 ].…”

The coevolution of mammae number and litter size

“…Therefore, fossil taxa cannot be included in the analyses presented (PGLS regressions or likelihood modeling). Fossilized embryos have been described for several crowngroup therians (45) (i.e., bats (46), cetaceans (47) (although see (48)), equids (49), oreodonts (50), mammoth (51) and ground sloths (52)). In all cases, either one or two embryos are preserved.…”

Report on the Discovery of Fossil Mares with Preserved Uteroplacenta from the Eocene of Germany

“…Within the abdomen occurs the nearly complete and articulated skeleton of a fetus. When we described this in detail (Franzen et al 2015), we discovered that most of the fetus is still enwrapped in a bright-yellow crust containing petrified bacteria (Text- fig. 6a-b).…”

“…One comes from Eckfeld, the other two from Messel. The report refers to investigations published in detail elsewhere (Franzen et al 2006(Franzen et al , 2015(Franzen et al , 2016, but a third pregnant mare with preserved uteroplacenta was recognized only recently. It is presented and analyzed here for the first time.…”