(August 26, 2016, 10:01 AM EDT) -- NEW YORK — A federal district court erred in certifying a class of investors in a securities class action lawsuit because shareholders failed to show that the class is “ascertainable” and because the shareholders failed to plead the superiority and predominance prongs of Federal Rule of Civil Procedure 23 in moving for class certification, underwriter defendants argue in an appellant brief filed in the Second Circuit U.S. Court of Appeals on July 25 (In re Petrobas Securities Litigation, No. 16-1914, 2nd Cir.)....