Originally Posted by roadwarrior

Exactly....thinner seat means you are closer to the pedals, and that could do it without question. Also, the OP needed to know where his hip was on the old saddle versus where the new one sets up. Since the Arione has a totally different shape and is longer, my guess is it's both fore/aft and height.

I ride an Arione on one bike and an Antares on the other. Different setups. Not dramatic, but different.

You were higher up on the old seat. Now you are lower. This is why you need to know your dimension from seat center to the pedal with the crank at maximum extension (extended down the seat tube line to the 7 o'clock position). Same goes if you change pedals or shoes. If you ride Sidi Genius versus Ergo for example, and swtiched you'd need to change seat height because the carbon Genius sole is thicker that the Ergo or Genius 6 soles (Ergo and Genius have the same sole).

Always always measure where things were and write it down before changing anything on a road bike.