In a cave in northern Spain, a team of scientists has retrieved the remains of 28 prehistoric humans, members of an enigmatic species that could be described as a little bit Neanderthal.

They had Neanderthal faces, with heavy brows and protruding noses. They had powerful mandibles and mouths that could open extremely wide, indicating that they used their teeth as gripping tools. But they didn’t have the large skulls or other robust skeletal features seen in the prototypical Neanderthals who, hundreds of millennia later, roamed Ice Age Europe.

These were apparently ancestors of Neanderthals, inhabitants of a line that many thousands of years earlier had split from the ancestors of modern humans. An international team of scientists published the description of the Spanish fossils Thursday in the journal Science but has not yet given this population a new species name. That will come later, the scientists said, after consultations with colleagues.