The discovery of new fossils of Metaspriggina walcotti (image ©Giant Blue Anteater) allowed to shed light on the origin of some of the characteristics of the chordates, animals with a backbone structure which in vertebrates has become the spine. It’s an animal lived about 500 million years ago, during the Middle Cambrian period. Due to their worm-like appearance and a length that could reach 10 centimeters (almost 4 inches), they don’t seem like much but they could be the ancestors of all vertebrates living today.

The Metaspriggina walcotti was initially described as similar to Spriggina, an animal part of the Ediacaran fauna. That’s because the first fossils were incomplete, only two specimens of which it was possible to recognize only a few features. The name walcotti of the species was given in honor of Charles Walcott, the discoverer of Burgess shale, the extraordinary fossil deposit where this animal was also found.

The interpretation of Metaspriggina walcotti’s characteristics remained controversial for several years, until the discovery of 40 new more complete fossil specimens in a new fossil deposit discovered in 2012. Thanks to them, it was possible to determine that this animal is one of the the oldest vertebrate fish, near Haikouichthys ercaicunensis and Myllokunmingia fengjiaoa, two very ancient fish found in various fossil deposits in China.

Metaspriggina walcotti shows some differences compared to the other similar species and may have played a key role in the origin of jaws. It has some characteristics of agnates, jawless fishes, and others of the gnathostomes, fishes with jaws, such as the external position of its gills. According to paleontologists there had to be an animal with those features but it was necessary to find well-preserved fossils to recognize them in this species.

It’s possible that these primitives jaws were originally used to push more water, and thus more oxygen, through the mouth and gills of Metaspriggina walcotti. Their use for chewing may have been a later adaptation. We probably will need to find other fossils species from the Cambrian and later periods to better understand the evolution of jaws and of vertebrates, which were crucial to the emergence of many present life forms, including humans.

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