A new study, led by paleontologists at the Royal Ontario Museum (ROM), sheds light on the evolution and ecology of Odaraia, a taco-shaped marine animal that lived during the Cambrian period. Fossils collected by ROM reveal Odaraia had mandibles. Paleontologists have finally been able to place it among the mandibulates, ending its long puzzling classification among the arthropods since it was first discovered in the Burgess Shale more than 100 years ago, and revealing more about the early evolution and diversification. The study The Cambrian Odaraia alata and the colonization of nektonic suspension feeding niches by early mandibulates was published in the journal Proceedings B.
The study authors were able to identify a pair of large appendages with prehensile serrated edges near the mouth, clearly indicative of mandibles, one of the most important and distinguishing features of the mandible group of animals. This suggests that Odaraia was one of the earliest known members of this group. The researchers made another stunning discovery: a detailed analysis of the more than 30 pairs of legs and an intricate system of small and large spines. According to the authors, these spines could have intertwined with each other, capturing smaller prey as if it were a fishing net, suggesting how some of these first mandibulates left the seabed and explored the water column, thus planting the seeds for their future ecological success.
“The main shield of Odaraia envelops virtually half of its body including its legs, almost as if it were in a tube. Previous researchers had suggested that this shape might have made this possible Odaraia to collect its prey, but the capture mechanism had eluded us until now,” says Alejandro Izquierdo-López, lead author, who was working at ROM as a PhD candidate at the University of Toronto during this work.Odaraia was beautifully described in the 1980s, but given the limited number of fossils at the time and its bizarre shape, two important questions remained unanswered: is it really a mandible? And what did it feed on?”
At almost 8 inches in size, the authors explain that early mandibles are fun Odaraia were part of a community of large animals that could have migrated from the bottom marine ecosystems characteristic of the Cambrian period to the upper layers of the water column. These types of communities could have enriched the water column and facilitated a transition to more complex ecosystems.
Cambrian fossils record the major differences between animal groups that emerged more than 500 million years ago. This period saw the evolution of numerous innovations, such as eyes, legs or shells, and the first diversification of many animal groups, including the mandibulates, one of the most important groups of arthropods (animals with jointed limbs).
Mandibulates are an example of evolutionary success, representing more than half of all current species on Earth. Today, mandibulates are everywhere, from sea-dwelling crabs to centipedes lurking in the undergrowth or bees flying over meadows, but their beginnings were more humble. During the Cambrian period, the first mandibulates were marine animals, most of which bore several head shields or shields.
“The Burgess Shale has been a treasure trove of paleontological information,” said Jean-Bernard Caron, Richard Ivey Curator at the Royal Ontario Museum and co-author of the study. “Thanks to the work we have done at the ROM on amazing fossil animals such as Tokummia And Waptiawe already know a considerable amount about the early evolution of mandibulates. However, some other species had remained quite mysterious, such as Odaraia.“
The Royal Ontario Museum holds the largest collections of Cambrian fossils from British Columbia’s world-famous Burgess Shale. Burgess Shale fossils are exceptional because they preserve structures, animals and ecosystems that under normal conditions would have decayed and disappeared completely from the fossil record. However, mandibulates are generally rare in the fossil record. Most fossils preserve only the hard parts of animals, such as skeletons or the mineralized cuticles of the known trilobites, structures that are absent from the mandible.
For over forty years Odaraia has been one of the Burgess Shale’s most iconic animals, with its distinctive taco-shaped shell, large head and eyes, and a tail that resembles the keel of a submarine. The public can view copies of Odaraia on view in the Willner Madge Gallery, Dawn of Life at the Royal Ontario Museum.
