Multi-aged social behaviour based on artiodactyl tracks in an early Miocene palustrine wetland (Ebro Basin, Spain)

Ignacio Díaz-Martínez,Juan Cruz Larrasoaña,Oier Suarez-Hernando,Blanca María Martínez-García,Xabier Murelaga,Juan Ignacio Baceta

doi:10.1038/s41598-020-57438-4

Abstract

We present a new locality with at least 880 vertebrate tracks found at the top of a limestone bed from the lower Miocene Tudela Formation (Spain). The trampled surface was formed by artiodactyls that crossed a muddy carbonate accumulated under the influence of water level variations in a palustrine environment. The tracks reflect different types of morphological preservation. The well-preserved tracks have tetradactyl digit impressions caused by both manus and pes, and are the type series of a new artiodactyl ichnotaxon, Fustinianapodus arriazui ichnogen. nov. and ichnosp. nov. The rest of the tracks, which are not as well preserved, are didactyl and were classified as undetermined artiodactyl tracks. According to their preservation, morphology, size, arrangement and orientation, we propose that this tracksite is the product of a social behaviour, particularly gregariousness, of a multi-age group of artiodactyls ~19 Ma ago. The morphologic and palaeoecologic data presented here suggest that the trackmakers were a group of anthracotheres with a livelihood similar to current hippos. They crossed, periodically, a fresh water palustrine area along some preferential pathways (trails).

Highlights

The Artiodactyla is a large order of placental mammals which includes pigs, peccaries, hippopotamus, camels, giraffes, deer, cows, antelope and sheep[1,2]
The artiodactyl tracks studied were impressed at the top of a limestone bed that belongs to the Tudela Formation
They present four types of preservation that are mainly conditioned by the characteristics of the muddy carbonate substrate: well-preserved true tracks, poorly-preserved true tracks, very poorly preserved true tracks and slipping true tracks

Summary

Introduction

The Artiodactyla is a large order of placental mammals which includes pigs, peccaries, hippopotamus, camels, giraffes, deer, cows, antelope and sheep[1,2]. The oldest fossil artiodactyls are from the lower Eocene in North America, Europe and Asia, and evolved to the large land mammals of today[3]. They are “even toed” or “cloven hoofed” ungulates because the autopod axis of symmetry is between the third and fourth digits[2]. The oldest artiodactyl tracks are known from upper Eocene strata of Europe and North America[10,11,12]. The size of the tracksite, the number of tracks and their preservation make it an ideal site to study important aspects of artiodactyls in the past. On the basis of the main orientation, arrangement, shape and size of the studied tracks, a paleoethological reconstruction is proposed

Methods

Results

Conclusion