The following notes are meant to supplement labs 17 and 18.  Much of the information you'll want to know can be found in the Fleagle reading on electronic reserve; other details can be found in the outlines to my A105 Lectures 9-11 (accessible through the A105 link from the main page, then click on Lecture Outlines on the left).  So, the information below is limited to topics not covered in either of the aforementioned resources.

Sahelanthropus tchadensis, "Toumai."  6-7 million years old.  So far, a mostly complete cranium has been recovered; however, it is in relatively poor condition.  Its finders suggest that it may have some features in common with Homo that are not shared by australopithecines; however, it is far too soon to accept or reject these claims.  Importantly, it was found in West Africa; most other hominid fossils are found in East or South Africa.

Orrorin tugenensis, "Millennium Man."  About 6 million years old, from Kenya.  About 13 skeletal parts have been recovered, including teeth; multiple individuals may be represented.  Its discoverers claim evidence of bipedalism in its remains; they also believe they have identified certain features in the dentition that would ally Orrorin more closely with Homo than with hominids much closer in age (such as Ardipithecus); these features include relatively small molars and thick dental enamel.

Ardipithecus ramidus.  Most specimens date around 4.2-4.5 million years ago; recent finds that appear to belong to a subspecies of this hominid date to over 5 mya; from Ethiopia.  Its molars are smaller than those of australopithecines, and it has thin dental enamel.  One deciduous mandibular first premolar is said to more closely resemble that of a chimpanzee than seen in later hominids.  A relatively small brain size would be expected; the foramen magnum and pelvis fragments reported suggest bipedalism, but much more will be known when more finds are published.

Australopithecus garhi.  About 2.5 million years ago, in Ethiopia.  Its brain was about 450cc, with a prognathic jaw similar to A. afarensis; its molars fall within the robust australopithecine range but also have Homo-like features.  Postcrania have also been recovered.  It was found in association with cutmarked fauna (animal bones), and the earliest known stone tools have been recovered from a study area located quite close to the garhi site.

Kenyanthropus platyops.  3.5 million years ago, from Kenya.  Its place in the hominid lineage is still uncertain;  a single cranium has been found so far, with a mix of primitive and modern traits.  Controversial; some scientists would place later fossils now assigned to Homo rudolfensis into this genus, while others would place this find into an australopithecine species.