Yesterday in Bamberg v. Dalvey, __ F.3d __ (Fed. Cir. 2016)(Hughes, J.), following Tronzo v. Biomet, Inc., 156 F.3d 1154 (Fed. Cir. 1998),  the court narrowed the scope of the invention described in the parent application (and thereby denied priority to the parent) because the parent specification included arguments that a particular feature of the invention had advantages over the prior art not possessed by a prior art embodiment otherwise within the literal wording of the claim:

“In Tronzo [ ] this court determined that the asserted claims … which described a generic-shaped cup hip implant, were invalid because these claims could not claim priority to the parent patent….”  [T]he asserted claims could not claim priority to the parent patent because it did not provide written description support where it described only a conically shaped cup and specifically distinguished the prior art (i.e., other shapes) as “inferior” by detailing the advantages of the conically shaped cup. [Tronzo,, 156 F.3d  at 1158–59]. Because the specification detailed why the prior art was inferior, the court determined that the patent ‘discloses only conical shaped cups and nothing broader.’ Id. at 1159.” (original emphasis)