Key 1. Aid to identification of live collected specimens
Digestive coil
Right valve configuration
(if not visible use Key 2.)
Right valve only
Both valves
Simple loop
Right valve configuration
Relatively close, taping anteriorly
Multi-coiled
Yoldiella valorousae
Yoldiella jeffreysi
Multi-coiled
Position of the Umbo
Midline
Yoldiella annekovae
Anterior to midline
midline
midline
Posterior to midline
midline
Parallel
Reverse loop
Yoldiella insculpta
Yoldiella fabula
Ventral margin
Shallowly rounded/straight
Deeply rounded
Dorsal margin
Gently sloping
Steeply sloping
Yoldiella curta
Yoldiella annekovae
Horizontal/Slightly curved
Yoldiella philippiana
Tumidity / Hinge
Ventral margin
Strongly rounded
Moderate
compressed
Tumid
Moderate
Narrow - weak - nearly 180°
Broad - solid - acute angle
Yoldiella thaerella
Yoldiella solidula
Shallowly rounded
Yoldiella frigida
Yoldiella nana
Umbo
Shell shape
Deeply oval
Elongate oval
Small
Broad/prominent
Yoldiella frigida
Dorsal margin
Posterior margin
Broadly rounded
Truncated
Steeply sloping - slightly concave
Gently sloping - slightly convex
Horizontal/Slightly curved
Portlandia intermedia
Yoldiella philippiana
Yoldiella biscayensis
Tumidity
Moderate
Tumid/Inflated
Dorsal margin / Ventral Margin
Steeply sloping - slightly concave
Gently sloping - slightly convex
Yoldiella propinqua
Deeply rounded
Yoldiella incala
Shallowly rounded
Yoldiella lucida
Yoldiella lenticula
Key 2. Aid to identification of live collected specimens
Position of the Umbo
Posterior to midline
Anterior to midline
Dorsal margin
Midline
Gently sloping
Horizontal/Slightly curved
midline
midline
midline
Steeply sloping
Yoldiella philippiana
Yoldiella fabula
Tumidity / Hinge
Posterior margin / Ventral margin
Obliquely truncated
Truncated less obliquely
Rounded
Shallowly rounded/straight
Yoldiella nana
Yoldiella annenkovae
Obliquely truncated
Broadly rounded
Moderate
compressed
Very Tumid - solid
Moderate
Narrow - weak - nearly 180°
Broad - solid - acute angle
Yoldiella solidula
Ventral margin
Shallowly rounded/straight
Deeply rounded
Deeply rounded
Broadly rounded
Yoldiella frigida
Yoldiella annekovae
Dorsal margin
Dorsal margin
Horizontal/slightly concave
Gently sloping
Yoldiella jeffreysi
Slightly curved
Horizontal / shelf - like
Yoldiella insculpta
Yoldiella curta
Yoldiella thaerella
Shell shape
Elongate - extending posteriorly
Rounded oval - equal
Umbo
Broad - Prominent
Small
Posterior margin
Broadly rounded
Truncated
Dorsal margin
Gently sloping - slightly convex
Steeply sloping - slightly concave
Horizontal/Slightly curved
Yoldiella philippiana
Tumidity
Tumid - strongly inflated
Posterior margin / Ventral margin
Moderate
Truncated
Yoldiella lenticula
Shallowly rounded
Deeply rounded
Portlandia intermedia
Yoldiella insculpta
Posterior margin / Hinge
Narrow
Broadly rounded
Resilifer not developed
Yoldiella jeffreysi
Tumidity
Rounded
Narrowly rounded & truncated
Broad
(Rounded in juvenile specimens)
Well developed resilifer
Yoldiella propinqua
Compressed
Moderate
Yoldiella biscayensis
Yoldiella valorousae
Dorsal margin / Ventral Margin
Steeply sloping - slightly concave
Deeply rounded
Yoldiella incala
Gently sloping - slightly convex
Shallowly rounded
Yoldiella lucida