What is this the longest possible series of consecutive captures in a legal position? Here is an example of 25 on the same square, which is not required.
[FEN "q1kr2q1/1qnqnb2/2prp3/q2pK3/2P1P3/1QNQNB2/Q2R2Q1/3R3Q w - - 0 1"]
1. exd5 cxd5 2. cxd5 exd5 3. Bxd5 Qaxd5+ 4. Ncxd5 Rxd5+ 5. Nxd5 Nexd5 6. Qdxd5 Nxd5 7. Qbxd5 Qdxd5+ 8. Rxd5 Qxd5+ 9. Qaxd5 Bxd5 10. Rxd5 Qaxd5+ 11. Qxd5 Qxd5+ 12. Qxd5 Rxd5+ 13. Kxd5