Those LFD resources contain animations played in the cutscenes, the missions objective screens that appear in the PDA, and the game menus.
ANIMs are quite logically a collection of DELTs.

Note: the .anm extension is a convention adopted by add-on developers when writing conversion programs, there are no real ANM files in DARK FORCES.

Their format is quite simple:

ANIM_Header IS { NbDELT int // number of embedded DELTs }

Then follows each DELT, encoded as:

ANIM_DELTData IS { DELTSize long // the size of the embedded DELT aDELT bytes[n] // a complete DELT resource }