Haliotis ovina patamakanthini Dekker, Regter & Gras, 2001
Distribution: at least Andaman Sea, possibly southern China Sea,
in deeper waters than average ovina. There is a discussion to decide
whether this is a subspecies or just a local form.

Two shells from Phuket area, Thailand. Left: 49mm ovina. Right: 51mm patamakanthini.
According to D. Geiger, the differences, in morphology as well as in anatomy,
don't overstep the limits of ovina's variability, even if, like here, they seem obvious.
Patamakanthini is flatter than ovina s.s, with little or no bump at all.
The shell is more oblong, with often some large folds near the anterior margin.
30m deep, collected by Moken people, Rache Yai island, Phuket area. 65mm.
Same spot, 62mm.
Left & center: common patterns of patamakanthini. Right: comparison with flat ovina ovina (P vs. O).
Between the columella and the row of holes, a typical ovina bears well defined spiral cords;
some of them are visible on the ventral side of the shell (see top O detail).
This feature is not characteristic of patamakanthini, and could help to a better identification.
10-15m deep, in crevices, Rache Yai island, Phuket. 50mm.
When these spiral cords exist, they are on the dorsal side. Notice the strong shoulder above the suture line.
As a typical specimen is often quite flat, this shoulder is more pronounced than in ovina s.s.
Same spot. 48mm. Most of the shells that are offered for sale are red, but other colours are not uncommon.
Regarding this angular shoulder: crenulated in ovina, it is smooth in patamakanthini.
Nha Trang, Khanh Hoa, south-eastern Viet Nam. 90mm.
H. o. patamakanthini often reaches larger sizes than ovina ovina.

All pics © Olivier Caro