Complex sentence: The 4-4-2'Atlantic' type of locomotive originated in the USA and were built expressly for mainline passenger express services, evolving from the less stable 2-4-2 wheel arrangement.
Split into simpler sentences: The 4-4-2'Atlantic' type of locomotive originated in the USA and were built expressly for mainline passenger express services. The type evolved from the less stable 2-4-2 wheel arrangement.