Ardipithecus ramidus Poorly known. Predates everything else (~4 MYA). Upright posture, very small cranial capacity.
Australopithecus. Early manlike forms living from ca. 3.8 MYA to about 2 MYA. Oldest form A. afarensis followed by A. africanus. Cranial capacity less than 600 CC.
Paranthropus. Largebodied vegetarian (mostly fruit-eating) forms deriving from and contemporaneous with Australopithecus. Sagittal ridge – the “crest” at the top of the skull to which jaw muscles were anchored. Three species: * P. robustus* – despite the name the least robust of the forms (it got named first). * P. boisei* (formerly Zinjanthropus) – larger, heavier, bigger ridge. * P. aethiopicus* – known primarily from the “Black Skull” and apparently slender and with enormous jaw muscles. (My wife and I speculate that it is an adolescent P. boisei. The paranthropines existed from about 3.5 MYA to 2 MYA and perhaps a bit beyond.
Homo habilis: Leakey’s earliest man. Probably the first tool- and fire-user. Fairly small cranial capacity, but over 600 CC, IIRC.
Homo erectus: First form to leave Africa – found in the Middle East, southern Europe, Asia, and Indonesia. Java Man, Peking Man, and a few other types belong to this species. Old synonyms include Pithecanthropus and Sinopithecus. Substantially larger cranial capacity. Primitive tool user.
Homo sapiens: Modern man and his immediate ancestors.
There are those who subdivide Homo much further, including:
Homo rudolfensis - advanced H. habilis
H. ergaster - a variant on *H. erectus, including Turkana Boy
H. heidelbergensis - “archaic Homo sapiens” to the lumpers. About 500,000 YA.
H. neanderthalensis - the name makes clear what this is. Lived from ca. 200,000 YA to about 30,000 YA. Included the “classic” forms of your childhood books, which were adapted to the rigors of Ice Age Europe, and more “normal” looking forms in the Middle East. Neanderthals averaged a larger cranial capacity than modern man does.
That’s from memory; if I can remember to do so, I’ll look up the details from my wife’s papers and post more (probably in response to questions). Corrections where my memory is slightly “off” are requested; I vouch for the general validity of the above but not for specifics, in particular dates and specific-number cranial capacities.