Homo antecessor is a taxon with dubious characteristics. It shares a distinct supraorbital torus, a triple rooted molar, a cranial capacity of over 1000 cc’s, and lived some 800,000 years ago. The sites for this supposed taxon are in Spain, at Atapuerca. Further, the tool technology associated with H. antecessor is Oldowan. Estimated height for this species is 172 cm.
My take on this taxon is that it is, indeed, a variation on Homo heidelbergensis. The lumpers and splitters in taxonomy and cladistics have been at work.