It’s bright yellow and fewer than five inches in diameter, and you’ve never seen it before: a new coral species, Chromoplexaura cordellbankensis. It’s named after Cordell Bank, where it was discovered last summer by scientists with the California Academy of Sciences and Cordell Bank National Marine Sanctuary. Aboard the Bell M. Shimada, a research boat owned by the National Oceanic and Atmospheric Administration, the team encountered the new species using a remotely operated vehicle—a small underwater robot that provides high-definition video above. Since the first finding, scientists have identified the same species within the Channel Islands and Monterey Bay National Marine Sanctuaries. Danielle Lipski, a research coordinator for Cordell Bank who was on the Shimada, said her team has looked at older imagery of the region where they found the coral, tracing it back at least to 2004. The device they used to make the discovery is a large improvement on the technology available two decades ago; the species, she clarified, has likely existed long before 2004. There are several dozen known species of deep-sea coral on the West Coast, providing important nursery habitat for fish and invertebrates. “Deep sea coral is really vulnerable to any type of disturbance,” Ms. Lipski said. “It’s slow-growing and long-lived. They are particularly vulnerable to changing ocean conditions. They take a long time to recover.” The new coral is relatively small: some deep-sea coral can reach more than a meter wide and a meter tall. Discovering a new species on the 26-square-mile underwater bank—once a mountain range and now a hotbed for marine life—is both exciting and a fairly regular occurrence, according to Ms. Lipski. “We still don’t have a complete picture of the animals that live in the deep sea,” she said. “And we still have so many questions about this coral: foremost, how long has this been here?” The findings, co-authored by Dr. Gary Williams from the California Academy of Sciences and Dr. Odalisca Breedy from the University of Costa Rica, were published in the journal The Proceedings of the California Academy of Sciences, on May 15.