Acanthothecis collateralis is a rare endemic species of script lichen in the family Graphidaceae.

[1] Found in the Andaman Islands of India, it was formally described as a new species in 2007 by Urmila Makhija and Bharati Adawadkar.

It is distinguished from other Acanthothecis species by its specific arrangement of ascomata and distinct chemical composition.

The exciple, a protective layer, is brown and non-striate, converging at the base and covered by a thalline margin up to the top.

Unlike the closely related Acanthothecis rosea, A. collateralis does not contain the pigment isohypocrelline and does not have rose-pink ascocarps.