1	Odontostyle 19.5–25 µm long	Calcaridorylaimus ruwenzorii
–	Odontostyle shorter, ≤17 µm	2
2	c’=11	Calcaridorylaimus simillimus
–	c’<9	3
3	c’=2.2–2.4	Calcaridorylaimus beatus
–	c’≥ 2.9	4
4	c≤11	5
–	c>11	7
5	V=45–47, supplements 10–13	Calcaridorylaimus promissus
–	V>49, supplements 6–9	6
6	Vulva longitudinal, spicules 52–54 µm	Calcaridorylaimus calcarifer
–	Vulva pore-like, spicules 39–45 µm	Calcaridorylaimus sirgeli
7	Lip region 14–17 µm wide, vulva longitudinal	8
–	Lip region 11–13 µm wide, vulva not longitudinal	9
8	Tail 120–171 µm long, L=1.6–2.27, spicules 57–67	Calcaridorylaimus arcticus
–	Tail 100 µm long, L=1.3–1.7, spicules 72	Calcaridorylaimus signatus
9	Vulva pore-like, spicules 52–57	Calcaridorylaimus andrassyi
–	Vulva transverse, spicules 38–46	Calcaridorylaimus castaneae