The amphibians you raise is a frog.
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern R--A-IU-. That is, eight letter words with 1st letter R and 4th letter A and 6th letter I and 7th letter U. In alphabetical order, they are: ranarium rosarium
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern R-NA--U-. That is, eight letter words with 1st letter R and 3rd letter N and 4th letter A and 7th letter U. In alphabetical order, they are: ranarium runabout
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 9 words with the pattern R---R-U-. That is, eight letter words with 1st letter R and 5th letter R and 7th letter U. In alphabetical order, they are: ranarium redargue remarque remurmur repursue resprout rigorous rosarium rumorous
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 14 words with the pattern ---ARIU-. That is, eight letter words with 4th letter A and 5th letter R and 6th letter I and 7th letter U. In alphabetical order, they are: aquarium conarium denarius fusarium ossarium puparium ranarium rosarium samarium senarius solarium sudarium velarium vivarium