Ancient worm predators ruled Cambrian seas

In the ancient depths of the Early Cambrian, a groundbreaking discovery has unveiled the existence of a formidable group of aquatic predators that prowled the waters over 518 million years ago. These newly identified creatures, named Timorebestia, meaning ‘terror beasts’ in Latin, are colossal worms with distinctive features such as fins along their body, elongated antennae, and massive jaw structures within their mouths. These aquatic giants, exceeding 30cm in length, emerge as some of the largest swimming animals of their time, challenging our understanding of the Early Cambrian ecosystem.

Dr. Jakob Vinther, a senior author from the University of Bristol, notes the significance of Timorebestia in the context of the Cambrian period. While primitive arthropods like anomalocaridids were previously considered dominant predators, Timorebestia introduces a new player—a distant yet close relative of modern arrow worms or chaetognaths. Unlike their diminutive contemporary counterparts, Timorebestia ruled as oceanic behemoths, occupying a prominent position in the ancient food chain.

The researchers reveal that these ancient ocean ecosystems exhibited surprising complexity, featuring multiple tiers of predators. Timorebestia, perched near the apex, played a role equivalent to modern top carnivores like sharks and seals. This finding sheds light on the intricate dynamics of Early Cambrian marine life.

Examining the fossilized digestive systems of Timorebestia provided further insights. The remains of Isoxys, a common swimming arthropod with protective spines, were discovered inside Timorebestia. Morten Lunde Nielsen, part of the study, remarks on the abundance of Isoxys at the Sirius Passet fossil site and how Timorebestia voraciously preyed upon them.

Arrow worms, among the oldest animal fossils from the Cambrian, take on a crucial role in understanding the evolutionary timeline. While arthropods appear in the fossil record around 521 to 529 million years ago, arrow worms trace back even further, reaching at least 538 million years into the past. Dr. Vinther suggests that both arrow worms and the more primitive Timorebestia likely dominated the oceans before arthropods rose to prominence, indicating a possible dynasty lasting 10–15 million years.

Luke Parry from Oxford University emphasizes the significance of Timorebestia in tracing the origins of jawed predators. Unlike contemporary arrow worms with external bristles for catching prey, Timorebestia exhibited internal jaws, resembling microscopic jaw worms seen today. This discovery strengthens our understanding of how arrow worms evolved over the course of half a billion years.

The senior author and field expedition leader, Tae Yoon Park from the Korean Polar Research Institute, highlights the unique nervous center found in arrow worms called a ventral ganglion. This distinct feature, preserved in Timorebestia and another fossil named Amiskwia, provides confidence in the hypothesis that these organisms share an evolutionary lineage. The discovery of such predators in the remote Sirius Passet in North Greenland opens a window into the Early Cambrian, offering anatomical details, including digestive systems, muscle anatomy, and nervous systems.

As the research unfolds, the team anticipates sharing more exciting findings in the coming years, promising a deeper understanding of the earliest animal ecosystems and their evolutionary trajectories. The study, published in the journal Science Advances, marks a significant leap in unraveling the mysteries of Earth’s ancient inhabitants.

Source: University of Bristol

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