"Biodiversity scientists estimate that we have discovered less than 10% of the species on our planet," says Dr. Meg Lowman, the Academy's Chief of Science and Sustainability. "Academy scientists tirelessly explore the unexplored regions of Earth -- not only to discover new species, but also to uncover the importance of these species to the health of our natural systems."
One of the newly discovered species is this electric ray, known by the Latin name Tetronarce cowleyi. The Academy describes it as a shiny black-topped, cream-bottomed predator that glides along the seafloor at depths of nearly 500 feet.
Another view of the newly discovered electric ray Tetronarce cowleyi, which was found in the southeastern Atlantic. The ray can discharge a powerful electric shock of 45 volts to paralyze its prey -- "enough to knock down a human adult!" said co-discoverer Dr. David Ebert.
Six new species of so-called Dracula ants were discovered in Madagascar and Seychelles. The California Academy of Sciences says these tiny, subterranean ants are known for hunting down prey with dagger-like teeth.
They live in underground tunnels and some go their entire lives without ever glimpsing sunlight.
"There is a reason we call these strange Prionopelta ants 'Dracula,'" said Dr. Brian Fisher, who discovered the tiny, subterranean species in Madagascar. "They are known to wound the young of their colonies before drinking their blood -- called 'hemolymph' in insects. It's a bizarre but fascinating means of distributing nutrients throughout the colony."
Scientists documented several new species of nudibranch -- a type of sea slugs useful for biomedical research.
The Chelidonura alexisi nudibranch, which is black with tiny white spots, was first described from a deceased specimen found in 2011, but in 2015 researchers encountered a live example in the Philippines.
The Chelidonura alexisi nudibranch was found during an expedition led by Dr. Terry Gosliner in the tropical waters of the Philippines.
"Whether we're finding new species or adding to our understanding of previously known creatures and habitats, these expeditions help us pinpoint how and where to focus protection efforts," Gosliner said in a statement.
This fossilized tooth is from a "new" species estimated to be about 100 million years old. The previously unknown type of prehistoric shark has been dubbed Pseudomegachasma or "False Megamouth." Scientists believe it fed on plankton.