Most deformities that affect apes and primates are known as well as how they affect bones. So those are usaully detectable. The paper itself will be able to tell you why they classified it as a distict species. Somebody had the pdf and offered to share I believe.
The skull itself was discovered in 1970s and as far as I remember had a cranial structure very different from habilis of erectus grades. But check a review paper on that.