FOSSIL TROIKA hints at a variable H. erectus. These specimens from Dmanisi exhibit characteristic H. erectus features, such as a heaping up of bone along the midline of the skull known as a sagittal keel and marked constriction of the skull behind the eyes. But they stop short of the classic morphology of that hominid in several ways¿their small brain size, for example, which was about half that of a modern human (right). Specimen D2700 (left), from a teenager, is especially primitive, resembling H. habilis not only in size but in the thinness of its brow, the projection of its face and the rounded contour of the rear of the skull. Some researchers propose that these fossils might represent a new species of Homo. Others suggest that the remains belong to more than one species, pointing to the enormous lower jaw known as D2600 that was unearthed in 2000. Indeed, this mandible is far too large to fit comfortably with any of the crania yet discovered (only D2700 turned up with an associated mandible, D2735; the other fossils were isolated finds). For now, the Dmanisi team considers all the fossils as members of the same, mutable species, H. erectus.