Currently, only one species, Trichoplax adhaerens, is acknowledged to belong to the Placozoa. The Italian Francesco Saverio Monticelli described another species in 1893, which he found in the waters around Naples, naming it Treptoplax reptans.
A standard mallet has a head length of 9 to 9.5, and this is recommended for beginners. Expert players may use longer head lengths up to 12, as this is thought to make aiming more accurate and makes it harder to accidentally twist the mallet during the stroke.
1 The standard length for a French rolling pin is 20, while 12 (30cm) is the standard for wooden, metallic rolling pins. Marble rolling pins tend to be 10(25cm) in length. Rolling pins longer than 32 can cause bowing.  Don't choose a longer one for normal dough work; it will be too unwieldy to work with.