The hybrid was especially rare because of its melon-headed genes: The toothed-whales are rarely seen in these Hawaiian waters, the researchers wrote.
A genetic analysis revealed the animal was likely a first-generation hybrid between a female melon-headed whale (a rarely seen type of dolphin) and a male rough-toothed dolphin, marking what's thought to be the first-ever documented discovery of a hybrid between the two mammals.
"The head shape appears intermediate between the two species, with a gently-sloping rostrum rather than the rounded-head of a melon-headed whales but which is truncated compared to rough-toothed dolphins", researchers said.
A report published last week by ocean research organisation Cascadia Research Collective concluded that a mammal spotted off the coast of Kauai, Hawaii, in August a year ago is indeed the product of mating between a dolphin and a whale.
"It isn't and shouldn't be considered a new species", Robin Baird, a biologist with the research group, told HuffPost in an email.
In a report published this month, the researchers said it had "pigmentation and morphological characteristics suggesting it may be a hybrid". That's because two animal species are unlikely to have the same number of chromosomes, and hybrids won't be able to reproduce if their parents are too genetically dissimilar.More news: ‘Collusion is not a crime,’ says Trump, as Mueller-Manafort trial begins
The animal is a cross between a melon-headed whale and a rough-toothed dolphin.
And, although rare, other dolphin hybrids are known, such as the offspring of a bottlenose dolphin and false killer whale (also delphinidae), called a wholphin, and the offspring of a beluga whale and a narwhal, called a narluga.
He said: "That isn't the case, although there are example where hybridisation has resulted in a new species".
And while this is a new find, it's not quite a "new species", as is being reported web-wide.
There may be similar hybrids out there, he told HuffPost.
Hybrids generally occur when there is a decline in the population in one of the parental species, so scientists will be looking out for such a decline. They also hope to do testing on other species in the area. This is because naval activities, particularly those that use sonar, can disrupt their way of life - and commonly used cetacean frequencies can interfere with sonar. It's been dubbed a "wholphin", although its technical name is Steno bredanensis.