The five craters are: Chicxulub (Yucatan, Mexico), Shiva (offshore western
India), Small Point Maine (offshore Maine & Massachusetts), Boltysh
(Ukraine), and Silverpit (North Sea).
All these craters date near 65 Ma
I haven't heard of the Small Point Maine crater and don't remember the age
of the Boltysh one. The Shiva "crater" is not a crater, however; Chatterjee
just interpreted a crater into a seafloor map without considering what the
geological evidence actually says and without explaining why the shape has a
corner -- elliptical would be fine, but it isn't elliptical. Ironically,
it's way too _big_ for a crater associated with this mass extinction!
Silverpit is real and has the right age, last time I checked at least.