It was determined the complete mitochondrial DNA sequences of the velvet worms (Phylum Onychophora) Oroperipatus sp. (Peripatidae) and Peripatoides sympatrica (Peripatopsidae), and showed that they encode highly reduced tRNA genes. Because a well-paired acceptor stem is essential for tRNA recognition by its cognate aminoacyl-tRNA synthetase, it was suspected that their products are restored by RNA editing. Here it is showed that many reduced mt-tRNA molecules in the onychophorans Oroperipatus sp. and Peripatoides sympatrica are post-transcriptionally edited by what appears to be a novel RNA editing mechanism. During this process, up to 34 nucleotides are added to the primary truncated transcripts, restoring the amino-acyl acceptor stem, the TΨC arm, and in some cases the variable loop and nucleotide in positions 42 and 43 in a standard tRNA structure, which represent the most extreme tRNA editing event reported in animal mitochondria to date. In addition, it was found sequences that form two stem loop structures in Oroperipatus sp. mtDNA, resembling the human stem loop structure associated with the origin of L-strand replication. This suggests that an analogue replication mechanism may exist in Oroperipatus sp. mtDNA. It is also reported that the Peripatoides sympatrica gene arrangement represents the ancestral Onychophoran gene order.