Title: Ancient Fossil Suggests Sea Squirts Were Bottom-Dwellers
Subtitle: Discovery Pushes Back Origin of Vertebrate Body Plan by 50 Million Years
Date: [Insert Date]
In a groundbreaking study published in Nature Communications, researchers have uncovered a 500-million-year-old fossil named Megasiphon thylakos, which provides valuable insights into the evolutionary history of sea squirts (tunicates) and challenges previous assumptions about their lifestyle. This remarkable finding suggests that sea squirts, our closest invertebrate relatives, were bottom-dwelling creatures, shedding light on the origins of tunicates and the fundamental vertebrate body plan.
Sea squirts are one of two types of marine invertebrates known as tunicates. While sea squirts attach themselves to hard surfaces, the other type consists of free-swimming tunicates such as salps, pyrosomes, and larvaceans. The stark contrast in their lifestyles has left scientists curious about the ancestral form of tunicates.
The researchers made this groundbreaking discovery while studying the collections at the Natural History Museum of Utah. When Javier Ortega-Hernández and Rudy Lerosey-Aubril, both invertebrate paleobiologists at Harvard University, stumbled upon a chunk of mudstone, they found a fossil that closely resembled a modern tunicate. The fossil, resembling a vase with two spouts, was later named Megasiphon thylakos.
Karma Nanglu, a paleontologist at Harvard University, examined the fossil and dismissed alternative identities for it. By comparing the fossil to modern tunicate muscles, Nanglu discovered distinct similarities. Advanced microscopy techniques were suggested to examine the fossil’s chemical elements, as the study of trace elements in ancient tunicate tissue could offer insights into their past living environments.
The unique preservation of soft tissues in Megasiphon adds weight to the argument that the earliest tunicates were bottom-dwellers like modern sea squirts. Combining these findings with recent molecular estimates, researchers hypothesize that the tunicate’s free-swimming lifestyle evolved independently multiple times, suggesting a complex evolutionary history.
The discovery of Megasiphon raises questions about the scarcity of tunicate fossils. While the Utah formation containing Megasiphon has preserved numerous soft animals, tunicate fossils have been rare. This has led researchers to speculate that tunicates were exceptionally uncommon during the Cambrian period.
Despite the mystery surrounding their scarcity in the fossil record, tunicates, with their simple body plans and lack of a true brain, likely had no reason to feel sad about their lonely existence during the Cambrian era.
This extraordinary finding not only offers important insights into the evolutionary history of sea squirts but also pushes back the origin of the basic vertebrate body plan by an astounding 50 million years. As more research continues to unravel the secrets of ancient tunicates, scientists await further discoveries that may shed light on their hidden past.
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