A smaller, square, keyed connector first brought to popularity in the Macintosh PowerBook SCSI Connectors. Because SCSI conenctors (even the bastardized Macintosh 25-pin conenctor) are rather big, they don't work well on a laptop. Solution? Use a new connector!
Enter HDI-30. It stands for, obviously, Hight Density Interface, 30 leads. It gives you enough pins to to a (basic) SCSI interface in less then 1cm sqaure. Of course this requires a special adapter, and they ain't cheap -- $10 to $30 USD new, but you can get 'em for $5 used, especially if the person selling it doesn't know what it is.
And, for a bit of fun, a few of the more 'amusing' computer manufacturers have, in the past, produced keyboards with this interface (ostensibly to provide things like more controls and speakers). Oh, joy.