Palythoa nelliae was described by Prof. Ferdinand Pax in 1935 on the basis of a colony from South Africa.
In the meantime, this crustose anemone has made its way towards Mozambique and is considered an invasive species.
It is interesting to note that in shallow tide pools, other species can be found at the same time as Palythoa nelliae, such as Zoanthus sansibaricus and Zoanthus durbanensis (see Molecular examination of rocky shore brachycnemic zoantharians (Anthozoa: Hexacorallia) and their Symbiodinium symbionts (Dinophyceae) in the southwest Indian Ocean).
The crustose anemone grows up to 3cm high and reaches a diameter of 10 - 15mm (the fspecification of 0.9mm comes from the first description by Pax).
Palythoa nelliae is often found in shallow coastal pools, especially in areas that are occasionally covered with sand.
In the book "Two Oceans" by Branch & Beckley, another anemone called "Protopalyothoe nelliae" is presented, but this species is said to avoid sand (page 16).
However, this species is unknown in WoRMS.