This is a transitional, what some journalists or laymen might call a missing link.
Scientists already know about it, along with a number of other intermediate species (see the chart).
Many non-scientists deny this type of evidence for religious reasons, but that does not make it go away, nor does it lessen its significance.
Fossil: KNM-ER 3733
Site: Koobi Fora (Upper KBS tuff, area 104), Lake Turkana, Kenya (4, 1)
Discovered By: B. Ngeneo, 1975 (1)
Estimated Age of Fossil: 1.75 mya * determined by Stratigraphic, faunal, paleomagnetic & radiometric data (1, 4)
Species Name: Homo ergaster (1, 7, 8), Homo erectus (3, 4, 7), Homo erectus ergaster (25)
Gender: Female (species presumed to be sexually dimorphic) (1, 8)
Cranial Capacity: 850 cc (1, 3, 4)
Information: Tools found in same layer (8, 9). Found with KNM-ER 406 A. boisei (effectively eliminating single species hypothesis) (1)
Interpretation: Adult (based on cranial sutures, molar eruption and dental wear) (1)
See original source for notes:
Source: http://www.mos.org/evolution/fossils/fossilview.php?fid=33
Source: http://wwwrses.anu.edu.au/environment/eePages/eeDating/HumanEvol_info.html