They clarify mysteries about the evolution of ruminants

A recent study reveals key aspects about the enigmatic Amphimoschus, a ruminant that lived in Europe during the Miocene, between 17.5 million and 13.8 million years ago. The study also provides information on the evolution of the cranial appendages of ruminants.

Scientists from the University of Zaragoza, the Miquel Crusafont Catalan Institute of Paleontology (ICP), the National Museum of Natural Sciences (MNCN, of the Higher Council for Scientific Research (CSIC)) and the University of Alcalá (UAH) participated in the research. , in Spain.

The work has been possible thanks to fossils found in the French paleontological sites of Artenay, Aerotrain and Thenay, loaned to researchers by the National Museum of Natural History in Paris, France.

The remains analyzed have allowed the team to learn for the first time in 150 years the postcranial skeleton of this animal described in 1873, of which only cranial and dental fossil remains were available. The results of the analysis suggest that this ruminant without cranial appendages occupied a basal evolutionary position within the cervoid group, that is, the ruminants with the closest evolutionary relationship to modern deer. This research challenges previously well-accepted hypotheses that associated Amphimoschus with other lineages within ruminants.

“With the added data from the postcranial skeleton, we have been able to confirm that Amphimoschus is not related to bovids as previously thought, but rather is a basal member of cervoids,” explains Israel M. Sánchez, researcher associated with the ICP. “Thanks to phylogenetic analyses, we have managed to redraw the evolutionary tree of ruminants and identify the three large lineages to which the current groups belong: Giraffomorpha, Cervidomorpha and Bovidomorpha,” adds MNCN researcher Juan López Cantalapiedra.

Artistic recreation of an adult male Amphimoschus in its habitat. (Illustration: Flavia Strani / University of Zaragoza)

The anatomy of the legs of this ruminant suggests that it could have lived in swampy or semi-aquatic environments because they resemble those of some current species, such as African sitatunga antelopes, adapted to this type of habitats. Like these antelopes, Amphimoschus had stylized legs with elongated hooves and very long fingers that opened at an angle, allowing this ruminant to move without problem on the very soft and plastic substrates characteristic of swampy environments. The research has also allowed us to estimate the body size of Amphimoschus, which would have weighed between 36 and 47 kilograms, somewhat larger than a current roe deer, which places it among the medium-sized ruminants of its time.

This work is another step in understanding the evolution of cranial appendages in ruminants, one of the most complex and hot topics in mammalian paleobiology. “The absence of horns in Amphimoschus is an interesting example of how some lineages of ruminants diversified without developing the characteristic cranial structures that we today associate with many members of this group, and is also proof that the debate of the single or multiple origin of The cranial appendages in ruminants are far from closed,” Sánchez highlights. “It also opens up new approaches to study the origin of the periodic regeneration of deer antlers. It is possible that perennial unbranched appendages preceded the antlers, since our results indicate that cranial appendages emerged only once in the evolution of cervoid animals,” adds Beatriz Azanza, professor of Palentology at the University of Zaragoza, who has participated in this study together with researcher Flavia Strani, and Daniel de Miguel, ARAID researcher with whom he co-directs the Paleoenvironmental Extinction and Reconstruction research group, attached to the University Institute of Environmental Sciences of Aragon (IUCA), of the University of Zaragoza.

The study is titled “The postcranial skeleton of Amphimoschus Bourgeois, 1873 (Cetartiodactyla, Ruminantia, Pecora) sheds light on its phylogeny and the evolution of the clade Cervoidea.” And it has been published in the academic journal Journal of Systematic Palaeontology. (Source: University of Zaragoza)