anthoceras, a near miss with a reason
heard as anthoceras
spelled anthoceros
Anthoceros, with o in the last syllable.
What the ear did
This one is a near miss with a good reason behind it. The Greek word for horn is keras, ending in as, and the genus takes the masculine form -ceros instead, as in rhinoceros, the nose-horn.
A-N-T-H-O-C-E-R-O-S
The full entry for anthoceros covers the name itself.