"The handles of the calyx-krater are placed low down on the body, at what is termed the cul. Their upward curling form lends the shape an appearance reminiscent of the calyx of a flower, hence the name. The earliest known example was possibly made by Exekias in the third quarter of the sixth century. It continues to be produced, mainly in red-figure, becoming more elongated over the course of the fifth and fourth centuries." Classical Art Research Centre, University of Oxford. Accessible online: https:www.beazley.ox.ac.uktoolspotteryshapescalyx.htm 2020 05 08 (en)
"The calyx-krater is one of the largest Attic vases, and is reminiscent of a bell-shaped flower. It is named for its convex lower body that has the configuration of the calyx of a flower, while the flaring upper body is suggestive of the bell-shaped corolla. It has large, robust, upturned handles situated opposite one another on the cul.The calyx-krater appears in Attic black-figure after the middle of the 6th c. BCE and is a popular shape until the end of red-figure."
http:kerameikos.orgidcalyx_krater (en)