Sphenoid

A sphenoid is a type of tetrahedron with only one symmetry axis. As such it has two different isosceles triangles and two identical scalene triangles as faces, and can also be called a mirror-symmetric tetrahedron.

In vertex figures
Sphenoids occur as vertex figures in a total of 23 non-prismatic uniform polychora, including all the cantitruncated polychora, also known as great rhombates. They also appear as vertex figures in the prisms of the 10 3D truncates.