Dil and formerly Ichy were the Big Bads of the Land Before Time 4 Journey through the mists. Dil is a Deinosuchus, one of many crocodilians called "Belly Draggers" in the series.
Because Ichy has sharper eyesight than Dil, he finds food for the two of them, and calls himself "the eyes". Dil is nearly blind, which is why she is dependant on Ichy to find food for her. However, because of his small size, catching prey is difficult for him. Therefore, Dil, when pointed in the direction of the prey, nabs them/it, and calls herself "the teeth".
Ichy and Dil are more partners than friends, as they constantly argue with each other and say they would be better off without each other. This is focused on in their song: "Who Needs You?". However, they still stay together because of their handicaps; Ichy's being size and Dil's being vision. It isn't until the end of the movie when they finally have had enough of each other, and finally split up. Dil slaps Ichy away with her tail, but when she turns around and finds an hungry Elasmosaurus looming overhead of her, she cries out for Ichy before getting chased by the Elasmosaurus. while Icky reformed from his evilness, Dil retained hers when the Villain leage eventallty founded her.
Role in the series
Dil returns in Quest for Camelot as a member of the Villain League, recruited mainly for her brute straingh and size, but with the downside that she's dumb and blind. in Spongebob and Friends find the black cauldron, she's is appearently still with the villain leage, cause they needed someone to be the eqilient of Icky since they can't find any other land before time bad guys, and the ones that did defeated Icky before are good guys, and will never work with villains, and may be able to perfectly understand reformnation.