It looks like #Solana smart contracts don't have a defined calling convention the way Ethereum does. You can send an arbitrary set of bytes to any contract, and it's up to the contract to interpret them.
Doing the equivalent to the @metaplex contract which is essentially the ERC721-equivalent on #Solana requires digging a bit deeper into the code (e.g. https://t.co/saV5geUpmh).