There’s a new T. rex in the fossil record, only this one terrorized the ancient seas. New research uncovers a new, massive species of mosasaur, a marine reptile that lived during the age of the dinosaurs. One of the largest mosasaurs known to date—stretching up to 43 feet long—this top predator was described from 80-million-year-old fossils that were found primarily in northern Texas decades ago. It was named Tylosaurus rex, or T. rex for short, meaning “king of the tylosaurs.”

A new study from the University of Copenhagen shows that marine heatwaves can disrupt microscopic moving structures on the surface of reef-building corals that support their oxygen uptake. When seawater temperature crosses a critical threshold, this oxygen supply mechanism collapses, increasing the risk of coral death.

The earliest known eukaryotes, the ancestors of all complex life on Earth, lived in oxygenated, shallow marine environments nearly 1.7 billion years ago, according to a new study led by researchers at McGill University and the University of California, Santa Barbara. The findings cast doubt on the long-held belief that early complex life emerged in oxygen-poor environments or floated freely in the open ocean.

A new study of the blue button (Porpita porpita), a small and elusive sea creature which lives on the surface of the ocean, has found that it may live for several years adrift at sea, much longer than previously estimated. Researchers from the University of Tokyo’s Misaki Marine Biological Station also found that the float which keeps the animal adrift expands by growing new rings from its outermost layer. Blue buttons are notoriously difficult to keep alive in captivity, so this is a step closer towards eventually understanding their full life cycle.

In the latest in a series of studies showing how lab-raised fish differ from those raised in more natural environments, researchers found that medaka maintained in more natural settings ovulated earlier than those in the laboratory. These findings highlight the challenges of inferring natural behavior from that observed in the laboratory.