Звичайні тюлені відрізняються від сірих меншими розмірами і v подібними ніздрями

The common seal can be distinguished from the grey seal by its smaller size and shorter head with a more concave forehead. Common seals have V-shaped nostrils. They are very variable in colour, from blonde to black, but generally grey with dark spots.
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The grey seal can be distinguished from the common seal by its larger size and longer head with a sloping 'roman nose' profile. Looking straight on, their nostrils are parallel, rather than v-shaped as in common seals. Mainly grey in colour, the unique pattern of darker blotches and spots can be used to identify individuals.

National Geographic