Ancient Fossil Rewrites Evolutionary History, Linked to Jellyfish and Coral Ancestors

A 540-million-year-old fossil, known as Salterella, has been reclassified, profoundly impacting our understanding of early animal evolution. This peculiar organism, which baffled scientists for decades due to its unique mineral-building methods, has now been definitively linked to the cnidarian family, a group that includes modern jellyfish and corals, as reported by sciencedaily on November 12, 2025.

The discovery sheds new light on how animals first developed skeletons during the Cambrian Period, a critical era of rapid diversification of life. Researchers at Virginia Tech, led by geosciences graduate student Prescott Vayda and University Distinguished Professor Shuhai Xiao, utilized modern analytical techniques to unravel Salterella's mysterious lineage.

For many years, the small, cone-shaped creature defied easy categorization, being variously grouped with squids, sea slugs, and even worms. Its dual approach to skeletal construction, combining both biomineralization and agglutination, made it an evolutionary enigma, according to ssbcrack News.

This reclassification places Salterella firmly within the Cnidaria phylum, a significant shift that helps fill a gap in the evolutionary tree. The findings, published in the Journal of Paleontology, suggest a more complex and earlier development of skeletal structures within this ancient group than previously understood.

The research deepens our comprehension of the "skeleton age" that dawned during the early Cambrian Period, approximately 538 to 506 million years ago. It highlights the diverse and often unconventional strategies early life forms employed to build protective and supportive structures, as noted by SciTechDaily on October 16, 2025.

The team’s meticulous analysis of Salterella’s morphology, habitat, and shell architecture provided the crucial evidence needed for this re-evaluation. This breakthrough promises to reshape evolutionary narratives and offer new insights into the origins of complex animal body plans, Virginia Tech announced.

• The Cambrian Period, often referred to as the "Cambrian explosion," witnessed an unprecedented diversification of animal life and the widespread development of mineralized skeletons between 541 and 530 million years ago. Most major animal groups independently evolved methods to build mineral skeletons or shells, typically through either biomineralization (forming mineral tissues on an organic framework) or agglutination (binding environmental minerals together), as detailed by Britannica.
• Salterella distinguished itself by employing both mineral-building methods simultaneously, a rarity among ancient animals. It grew a conical outer shell and then filled its inner cavity with carefully selected mineral grains, creating a unique double-layered structure. This unusual construction made its classification particularly challenging for paleontologists, according to sciencedaily.
• Historically, Salterella, along with a similar fossil called Volborthella, underwent numerous reclassifications, reflecting the scientific community's struggle to place them on the tree of life. Initial theories linked them to cephalopods or mollusks, before a new, separate classification was created for them in the 1970s, as reported by ssbcrack News.
• The recent reclassification was spearheaded by Prescott Vayda, a geosciences graduate student, and University Distinguished Professor Shuhai Xiao, who spent four years collecting and analyzing fossil samples from various locations, including Death Valley and Yukon, Canada. Their collaborative work involved detailed studies of the fossils' shape, mineral composition, and crystal structure, Virginia Tech confirmed.
• The definitive link to cnidarians, which include jellyfish, corals, and sea anemones, is significant because it connects Salterella to a phylum known for its ancient origins and diverse forms. Cnidarians are considered a sister group to bilaterians, offering crucial clues about the evolution of developmental pathways in early animals, as discussed in research on jellyfish evolution.
• Modern cnidarians, like jellyfish, have a long evolutionary history, dating back over 500 million years, with fossil evidence suggesting early forms resembled those seen today. Their evolutionary success is attributed to their adaptability and relatively simple body plans, which have allowed them to thrive across various marine environments, according to Jellyfish Evolution.
• The analytical methodology involved examining the fossils' internal structures, including the selective nature of the minerals chosen by Salterella. Researchers found that the organism avoided clay minerals, was selective with quartz, and favored titanium-rich grains, suggesting a sophisticated level of material selection for its skeletal structure, as highlighted by SciTechDaily.
• This discovery not only resolves a long-standing paleontological mystery but also provides a deeper understanding of the evolutionary pressures and innovations that led to the development of diverse skeletal forms during the Cambrian Period. It underscores the dynamic nature of early life and the complex relationships between ancient organisms and their modern descendants, as noted by the Journal of Paleontology.