Arthropleura (meaning "jointed ribs") was a giant, centipede-like arthropod from the Carboniferous period 320 to 299 million years ago, and was the largest known land arthropod ever.
Despite its relationship to centipedes it was actually omnivorous, or possibly even herbivorous, but could still have had venomous bites to protect itself from the few large predators that lived in the Carboniferous.
Arthropleura was a giant millipede, it grew 1-8.5 feet (0.3–2.6 metre) in length and was covered in hard armored plating. Despite its menacing appearance it was an omnivore or possibly an herbivore.
In The Land Before Time
Arthropleura makes a cameo appearance in The Land Before Time IX: Journey to Big Water during the end of the Imaginary Friend song, where it is seen amongst the other imaginary friends of the characters. However, its appearance is depicted as being more dinosaur-like than insect-like. It should be noted that this imaginary friend belongs to Spike, as hinted by the creature being slow and having a face similar to Spike's.
In The Land Before Time X: The Great Longneck Migration, during the song "Adventuring", Cera sings about scary things on Littlefoot's journey and, as she does so, a monstrous, imaginary Arthropleura with one huge eye, sharp teeth, a tuft of fur on its head, light green skin and red legs appears briefly near Ducky. It disappears when she tells Cera to stop.
An Arthropleura appears in the TV series episode The Cave of Many Voices, snatching up Petrie before it disappears, also appearing in the song "Adventuring". It has a slightly different appearance than the one from X, having two eyes instead of one and having blue legs instead of red. It also has a much longer tongue like a frog or chameleon. It is also smaller and has a different shade of blue.