MUJA and China University of Geosciences scientists document Europe’s first Jurassic lizard trackways in Asturias

The article presenting the research results, funded by the Principality of Asturias, was published online at the end of February in the prestigious international journal Ichnos, published by the Taylor & Francis Group.

The study focuses on two trackways (T1 and T2) preserved as convex hyporeliefs on the underside of a Late Jurassic sandstone layer, approximately 152 million years old, from the cliffs east of Playa de España (Villaviciosa). The specimens are now part of the museum’s collection and are on display in the gallery dedicated to the Asturian Jurassic.

In both trackways, the hand and foot footprints vary from tetradactyl to pentadactyl, are asymmetrical, and show a progressive increase in toe length. Their excellent preservation and morphological characteristics allow them to be attributed to a lizard and assigned to the ichnogenus Rhynchosauroides, which was widely distributed during the Permian and Triassic but is very rare in the Jurassic. In fact, the Asturian examples represent its latest known occurrence in the global fossil record.

Trackway T1 consists of seven footprints (four handprints and three footprints) and was produced by a lizard about 50 centimetres long. Trackway T2 includes six prints (three handprints and three footprints) and is attributed to a somewhat smaller individual, approximately 30 centimetres long.

In trackway T1, researchers detected the presence of a nearly continuous structure that is wide, straight and with very little relief. Its morphology allows it to be identified as a tail drag mark.

It was also observed that the distance between the hand and foot prints varies along the trackway, making it highly irregular. To understand this anomaly in locomotion, reflected in the irregularity of the trackway, several experiments were conducted with two modern lizard species: the ocellated lizard and the bearded dragon.

The non-invasive tests were carried out with captive specimens at a facility in the city of Jiangyin, in China’s Jiangsu province. When these animals—especially juveniles—transitioned from a stationary position to movement, they made abrupt turns that generated trackways similar to the Asturian fossil example.

The lizards left these tracks while moving across semi-consolidated mud in the deltas of the time, which flowed into an inland sea without tides. This sea was protected from strong waves by an external barrier separating it from the open ocean, a setting that favoured the preservation of the footprints.

The article abstract can be consulted at the following link: First report of lizard trackways from the Jurassic of Europe: Ichnos: Vol 0, No 0 - Get Access

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Foundation for the Promotion of Scientific Research and Technology in Asturias (FICYT)