Brissopsis pohangensis sp. nov., a New Echinoid Species (Spatangoida) from the Middle Miocene Duho Formation, Pohang Basin, Korea
By : Bong Jin Lee and Dal-Yong Kong
Summarized by: Joshua Rivera. Joshua Rivera is a geology major and an Asian studies minor in Binghamton University. He is currently a senior and has no plans post-graduation. He hopes to one day get into an exploration program and find things related to his field, be it fossils, minerals or fossil fuels. In his free time, he currently writes short stories, poetry, and novels. He enjoys exploring the world on hikes, and enjoys playing video games.
Data: Researchers found 428 fossil samples from the Duho Formation, which is a subdivision along the Pohang Basin in southern South Korea. It can be dated to around the middle Miocene Epoch, which is roughly 12 million years old. Among these samples were a never-before discovered sea urchin (related to sea stars), in a group called the spatangoids or the“heart urchins”. Upon a closer look at these fossils, there were a few notable things which stood out. Its petals held a unique shape. The groove along it had a deeper indentation compared to others of its kind. One of its plates was significantly longer as well (Fig. 1). This was common among all found 428 samples. The samples were preserved in a flattened manner, likely from the weight of sediment pressing on it.
Hypothesis: These heart urchins seemed quite similar to others in their group, specifically a genus called Brissopsis. However, the various outliers in plate length and other aspects of its morphology had the researchers asking if these were sufficient enough to determine this finding as an entirely new species or a species already known in the genus Brissopsis.
Methods: These researchers collected and recovered these samples from the field. They began the process of cleaning and preparing the samples, removing any sediment and making sure details on the body were visible. Once clean, they measured the samples. To the best of their ability, they measured the length and width. However, some differences in morphology, or simply the form the critter takes, required microscopy in order to gauge. And so they were measured under a microscope. There were specific urchin related- anatomical parts that they noticed the most difference in. These were namely: the test, the apical disc, the fascioles, and the plastron. To help visualize, the test is the outer hard shell as a whole. The apical disc is the top most disc on the test. The fasciole is a flattened groove along the test. Lastly, the plastron is the bottom shell, or the bottom side of the test. Figure 1 shows these details.
Results: The different body measurements, among others, were enough to find similarities, and therefore confirm they belonged to the genus Brissopsis. It is primarily the measurements and morphology of the labral plate (a small plate near the mouth), which is larger here than other species. The petals were quite different in shape and pattern than other species. Finally, the patterns of the fasciole were also quite different, as they were much deeper than other closely related species. Whilst being a spatangoid, its morphology was far different, to warrant it being a newly discovered species within Brissopsis.
Also of note, their preservation was significant. These spatangoids were found not only preserved in high numbers together, they were also found alongside scallops and snails. Typically, these spatangoids are not very communal, spread anywhere from the shallower tidal flats to the abyssal depths, thousands of meters below sea level. Spatangoids would burrow beneath the sands where they would dwell, predate, far away from most other life. Should something happen to the condition of the sediments, like the oxygen content running low, they would abandon their burrows. Upon leaving the sediments they would typically die, overturning on the surface of the ocean floor. This suggests these spatangoids, in addition to scallops and gastropods, did not die naturally, like of age. Likely, they faced something far more catastrophic, killing them all quickly with little notice.
Significance: This discovery is a breakthrough for spatangoid research. Not only was a new species discovered, but a hypothetical new “piece of the puzzle” is now unlocked in the ecosystems of Miocene East Asia. The assemblage they were found in may now also be a starting point on any investigation studying how they lived and how their preservation can tell us more about how they died.
Broader Implications: This new heart urchin is the new piece of the puzzle, in the larger scheme of East Asian paleontology. Spatangoids feed by burrowing, in the ocean floor. They ate whatever they could. Brissopsis pohangensis may play a yet to be found role in the environment as both predator and prey. Further work to understand how their preservation tells us about their lifestyles or about the moments leading up to their death is warranted to better understand the broader ecological role these organisms played.
Lee, B. J., & Kong, D.-Y. (2025, June 30). Brissopsis pohangensis sp. nov., a new echinoid species (Spatangoida) from the Middle Miocene Duho Formation, Pohang Basin, Korea. Economic and Environmental Geology. https://www.kseeg.org/journal/view.html?uid=2300&vmd=Full#n