Indridae
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Indridae
Genera
Indri
Propithecus
Avahi
The Indridae (also mis-spelled Indriidae) are strepsirhine primates with only four teeth in the toothcomb instead of the usual six.

References

http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=572769
http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Undef&name=indridae&srchmode=1&keep=1&a=Go&lvl=3