the plural of hippopotamus is hippopotamus, hippopotamuses, or hippopotami
Straight answer: no. According to AskOxford, the ultimate source of English language questions, the plural of hippopotamus is hippopotamuses.
When a word ends in an S, you don't add another S to make it possessive. You simply add the apostrophe to make HIPPOPOTAMUS'
Coaster's is singular possessive. The plural is coasters, the plural possessive is coasters'.
The correct form is "its" for the possessive form in the plural. "Its" is used for both the singular and plural possessive forms, without an apostrophe.
The plural is briefs. The plural possessive is briefs'.
The plural is lads. The plural possessive is lads'.
The plural is trollies. The plural possessive is trollies'.
The plural is relatives. The plural possessive is relatives'.
The plural is stations. The plural possessive is stations'.
Museum is singular. Museum's is singular possessive. Museums is plural. Museums' is plural possessive.
The singular possessive form is heart's; the plural possessive form is hearts'.