Homo rudolfensis
Homo rudolfensis (Alexeev, 1986) is a late Pliocene hominid from
eastern Africa, representing an early member of the genus Homo.
The best specimen is the holotype KNM-ER 1470, a cranium housed at the Kenya
National Museum (Eastern Lake Rudolf collection). The original fossil was
fragmented into hundreds of pieces, but most of the braincase and face was
determined to be present. The skull was found in the early 1970s at Koobi
Fora, in the badlands east of Lake Rudolf (a.k.a. Lake Turkana),
northern Kenya, East African Rift Valley. It comes from just below the
KBS Tuff in the Koobi Fora Formation (Upper Pliocene), and dates to ~1.9 Ma
(early published dates of 2.6 Ma for the KBS Tuff were controversial; careful 40Ar-39Ar
dating by McDougall (1981) has conclusively shown that the ash bed is 1.88
million years old). This makes Homo rudolfensis a contemporary of Homo
habilis. Fossils assigned to Homo rudolfensis indicate its age
range is about 2.4 to 1.6 million years ago.
The key, distinguishing characteristics of the Homo
rudolfensis skull are a large braincase and a relatively flat face.
The braincase volume was originally estimated to be ~800 mL, later downgraded
to ~750 mL, and more recently estimated at ~525 mL. A recent revised reconstruction
indicates that the face is noticeably prognathic.
Homo rudolfensis (Alexeev, 1986) (above & below) - replica of KNM-ER 1470, the holotype cranium of the late Pliocene hominid Homo rudolfensis (replica on display at the Cleveland Museum of Natural History, Cleveland, Ohio, USA). The dark-colored areas represent portions of the skull that were not recovered. These photos show the traditional reconstruction of the skull. The exact nature of the contact area between the braincase and the face has always been somewhat uncertain. A 2007 revised reconstruction has the face of this creature projecting forward more than shown here.
The taxonomic status of Homo rudolfensis
continues to be discussed in the literature. This skull was originally
assigned to another early Homo hominid - Homo habilis.
Other interpretations include:
1) rudolfensis is an australopithecine hominid
(i.e., not Homo);
2) rudolfensis is a species of Kenyanthropus;
3) rudolfensis is a sexual dimorph of Homo
habilis;
4) rudolfensis is an early Homo species.
Most info. from Tattersall & Schwartz (2000) - Extinct
Humans.
Some info. from McDougall (1981) - Nature 294.