Around 500 million years ago, a strange creature called Odaraia alata swam through Earth’s seas. It had bulging eyes, a rudderlike tail, and 30 pairs of spiny limbs extending from its cigar-sized body. Most of its legs were tucked inside a protective shell that wrapped around its midsection. It also had a mysterious trident-shaped tooth between external jawlike structures in front of its mouth.
The creature likely met its end suddenly, buried underneath sediment. But the circumstances that led to its demise also immortalized it in the fossil record. Paleontologists found several Odaraia fossils in 1912 at the famous Burgess Shale fossil site in the Canadian Rocky Mountains. The best-preserved specimens were re-examined in the 1970s and 1980s, but had remained in storage for decades.
Recently, scientists took a closer look at one of these fossils using better tools and techniques. They were particularly interested in its mandible’s connection to the Cambrian explosion, when many advanced organisms emerged around 540 million years ago. Odaraia may have contributed to the dominance of creatures with mandibles, such as insects.
The evolution of the mandible gave animals a major advantage over competing organisms, allowing them to break larger structures into pieces and access new types of food. This led to a feeding frenzy, and animals with mandibles quickly took over the planet.
Odaraia had two feeding advantages: its relatively large size and its mandibles. Its large size allowed it to roam the open sea and feed more efficiently. The new study also showed that Odaraia was a filter-feeder, using its spiny legs to capture particles.
The discovery of Odaraia’s filter-feeding mechanism suggests that it had a double advantage that contributed to an evolutionary arms race, as it pressured other animals to adapt faster in response. Now scientists are focused on solving the mystery of O. alata’s unexpected trident-shaped tooth.
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Source: https://www.scientificamerican.com/article/500-million-year-old-alien-fish-taco-was-among-first-creatures-with-jaws/