Table 1.

Key morphological feature of Tripneustes species.

	T. depressus	T. gratilla gratilla	T. gratilla elatensis	T. kermadecensis	T. ventricosus
test shape	variable	high (TH > 63%TD)	depressed (mean TH 54%TD)	depressed (mean TH 51%TD)	high (TH > 59%TD)
adapical ambulacral primary tubercles	every second plate	every second plate	every fifth plate	every third plate	every third plate
ambital ambulacral primary tubercles	every third plate	every second plate	every third plate	every fourth plate	every third plate
adoral ambulacral primary tubercles	every second plate	every third plate	every second plate	every second plate	every second plate
ambulacral plates occluded from perradial suture	few	none	none	numerous (2 in 3 at ambitus)	only few at ambitus (1 in 3 plates)
aboral interambulacral primary tubercles on every plate	yes	yes	no (every second plate)	yes	yes
size of interambulacral tubercles	half of plate height	half of plate height	half of plate height	full plate height	half of plate height
enlarged secondary tubercles in adapical interambulacral plates	yes	no	no	no	yes
mean peristome size	22–36%TD	28.1%TD	36.9%TD	25.2%TD	30%TD
sunken peristomal margin	no	yes	no	no	yes
deeply bifurcate compass ends	?	yes	no	no	no
compass ends flat and wide	?	no	yes	yes	no
dumb-bell shaped ossicles extremely abundant in distal tubefeet	?	yes	no	no	completely absent