MNG
From Just Solve the File Format Problem
MNG (Multiple-image Network Graphics) is an animated image file format. It was designed to be an alternative to animated GIF.
The MNG format is very similar to PNG. MNG files are not, in general, valid PNG files, although all PNG files are by definition valid MNG files.
In addition to lossless compression, MNG can use JPEG compression. MNG also defines a subformat called JNG, which stores JPEG-compressed still images, and supports transparency.
