An
international team of Spanish and Portuguese researchers (Universidad de
Zaragoza, Euskal Herriko Unibertsitatea and Universidade Nova de Lisboa) that
has discovered and described a new species of sirenian, a primitive marine
mammal that swam in the waters of the Sobrarbe-Pirineos
UNESCO Global Geopark (Huesca, Northeastern Spain). This new mammal is the
first four-legged sirenian from Eurasia, and the oldest of its kind in West
Europe, with an age of 42 million years.
Sirenians
are the only plant-eating marine mammals, which has earned them their nickname as
“sea cows”. Nowadays, they are represented by the dugongs and manatees. The new
“sea cow” was found in the Spanish Pyrenees and has been described in the
journal Scientific Reports. The name, Sobrarbesiren
cardieli, honours both the territory of Sobrarbe and the local amateur
palaeontologist Jesús Cardiel Lalueza, who found the fossil quarry. It
represents a key step in the evolution of sirenians, this being a four-legged
animal yet to be fully adapted to the aquatic environment. This research is
part of the PhD thesis of Ester Díaz Berenguer, who is currently studying the
anatomy of Sobrarbesiren cardieli in detail to unveil how this
animal lived, particularly whether it was able to walk on land or used its legs
for swimming.
The field
expeditions in Sobrarbe started in 2009, under the management of Prof. Ainara
Badiola, and 600 fossils have now been collected. These are 42 million years
old (middle Eocene in age). Of these, over 300 are sirenian bones, belonging to
at least seven individuals, including adults and juveniles. Most of the
skeleton of Sobrarbesiren cardieli is known, including three
skulls, several vertebrae and ribs, and bones from all four legs. Of
extraordinary importance are the pelvis, femur and fibula – the latter being
the oldest recorded in any sirenian worldwide – which allow the study of Sobrarbesiren’s lifestyle. The fossil
quarry has also yielded remains of turtles, crocodiles, lizards, sharks and
small mammals, together with invertebrate animals and plants. This fauna and
flora has permitted the reconstruction of the palaeoenvironment where Sobrarbesiren cardieli lived and died, a
coastal delta with a tropical climate, flowing into the Cantabrian Sea.
All fossils
were excavated with the authorization of the regional government (Dirección
General de Cultura y Patrimonio) and are housed in the Museo de Ciencias
Naturales de la Universidad de Zaragoza. A selection of the most relevant
specimens will soon be in an exhibition in the gallery of the museum, located
in the University Paraninfo building. Ongoing research is being funded
and supported by several institutions (Universidades de Zaragoza y del País
Vasco, Geoparque de Sobrarbe, Gobiernos de Aragón y del País Vasco, Mineco,
Fondo Europeo de Desarrollo Regional).
The full
article in gold Open Access can be accessed:
Díaz-Berenguer, E., Badiola, A., Moreno-Azanza, M., Canudo,
J.I. 2018. First
adequately-known quadrupedal sirenian from Eurasia (Eocene, Bay of Biscay,
Huesca, northeastern Spain). Scientific
Reports https://www.nature.com/articles/s41598-018-23355-w
What a sirenian
looks like?
Four
sirenian species, including three manatees and the dugong, have survived until
nowadays. They first evolved 50 million years ago, from the same group of
terrestrial mammals that gave rise to the elephants, in the African continent.
Their aquatic lifestyle resulted in a series of changes in their body,
including hair and ear loss, a hydrodynamic body shape, hands modified into
flippers and the progressive reduction of the legs, which are completely lost
in modern forms. They also modified the lungs, which occupy most of the body of
the animal. Their flattened tail, used for propelling the animal, together with
thick and dense bones, makes them slow swimmers, feeding in the shallow sea
grasses.
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