Researchers from CONICET and the La Plata Museum (Argentina), the MUJA (Asturias, Spain), and the Rochester Institute of Vertebrate Paleontology (USA) document a new ichthyosaur from the Jurassic seas of Asturias

Researchers Marta Fernández and Lisandro Campos from CONICET and the La Plata Museum (Argentina), Judy Massare from the Rochester Institute of Vertebrate Paleontology (United States), and Laura Piñuela, Ángel García-Pérez and José Carlos García-Ramos from the Jurassic Museum of Asturias (MUJA) have documented the presence in Asturias—and for the first time outside the United Kingdom—of the Early Jurassic marine reptile Ichthyosaurus anningae. The study was published online in early September in the international journal Acta Palaeontologica Polonica.

The findings were presented today at the museum in an event attended by Pablo León, Director General of Cultural Heritage; José Ángel Toyos, Mayor of Colunga; Paulo García, Mayor of Ribadesella; and the MUJA scientific team, José Carlos García-Ramos, Ángel García-Pérez and Laura Piñuela.

The specimen is an incomplete ichthyosaur skeleton. Ichthyosaurs were marine reptiles with a streamlined body shape broadly resembling that of dolphins. The first skeletal remains of this specimen were discovered in 2009 by José Antonio Sánchez Féliz, a Madrid resident, in the cliffs near Vega Beach (Ribadesella).

The rock enclosing the bones, a dark gray marl, belongs to the Rodiles Formation, which dates to the Early Jurassic (201–175 million years ago). Recent research based on ammonites—marine cephalopods related to modern squid and cuttlefish—has made it possible to determine the age of the Asturian ichthyosaur with considerable precision, at around 192 million years ago, within the Pliensbachian Stage. The global fossil record of ichthyosaurs from this interval is relatively scarce, highlighting the importance of the discovery.

The sediment in which the reptile was originally buried formed the muddy, oxygen-poor seafloor of a very extensive marine shelf, less than 100 meters deep, that covered much of what is now Asturias during the first half of the Jurassic.

Ichthyosaur bones, particularly those of the skull, are extremely delicate, making preparation in the laboratory a difficult and time-consuming process. Once the specimen had been prepared, researchers were able to identify several skull bones—some of them preserved in three dimensions and displaying previously unknown details—as well as teeth, part of the left flipper, and numerous ribs and vertebrae, including cervical, dorsal and caudal vertebrae.

The shape of the humerus, together with diagnostic features of the skull, allowed the Ribadesella specimen to be assigned to Ichthyosaurus anningae, a species previously known only from the United Kingdom. The species was named in honor of the famous English paleontologist Mary Anning. A comparative analysis of the length of the Asturian specimen's humerus with those of other I. anningae specimens from southern England also showed that it is the largest known specimen of the species. It was an adult, with an estimated body length of approximately 2 meters.

Its dentition is markedly different from that of the ichthyosaur previously described from Asturias, which was found in cliffs near Rodiles (Villaviciosa) and assigned to the genus Leptonectes. These differences suggest that the two ichthyosaurs had substantially different diets. I. anningae had more robust, moderately conical teeth with rounded tips, consistent with a generalist diet, whereas Leptonectes had slender, finely striated and more delicate teeth, associated with a piscivorous diet.

Around 192 million years ago, the seas of Asturias were inhabited by at least two different genera of ichthyosaurs, together with plesiosaurs, another group of contemporaneous marine reptiles whose skeletal remains have also been discovered in Jurassic rocks in the region. These three marine reptiles represent the most complete skeletons of their respective groups known from the Iberian Peninsula.

Publication reference

Fernández, M.S., Piñuela, L., Massare, J.A., Campos, L., García-Pérez, A., and García-Ramos, J.C. 2026. First record of Ichthyosaurus anningae outside the United Kingdom: new evidence from the Lower Jurassic of northern Spain. Acta Palaeontologica Polonica 71 (3): 489–507.