are they extinct?
Yes, several species of small hippopotamids have become extinct
Pygmy hippopotamus
everal species of small hippopotamids have also become extinct in the Mediterranean in the late Pleistocene or early Holocene.
what is the pygmy hippopotamus? It  is a small hippopotamid. can you please describe it? They share the same general form as a hippopotamus. They have a graviportal skeleton, with four stubby legs and four toes on each foot, supporting a portly frame. The pygmy hippo, however, is only half as tall as the hippopotamus. The skin is  greenish-black or brown, shading to a creamy gray where is it found? It is native to the forests and swamps of West Africa, primarily in Liberia, with small populations in Sierra Leone, Guinea, and Ivory Coas what does it eat? Its diet consists of ferns, broad-leaved plants and fruits how does it reproduce? A study of breeding behavior in the wild has never been conducted; the artificial conditions of captivity may cause the observed behavior of pygmy hippos in zoos to differ from natural conditions.
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Pygmy hippopotamus [SEP] Extinct pygmy and dwarf hippos
Several species of small hippopotamids have also become extinct in the Mediterranean in the late Pleistocene or early Holocene. Though these species are sometimes known as "pygmy hippopotami" they are not believed to be closely related to "C. liberiensis". These include the Cretan dwarf hippopotamus ("Hippopotamus creutzburgi"), the Sicilian hippopotamus ("Hippopotamus pentlandi"), the Maltese hippopotamus ("Hippopotamus melitensis") and the Cyprus dwarf hippopotamus ("Hippopotamus minor"). These species, though comparable in size to the pygmy hippopotamus, are considered dwarf hippopotamuses, rather than pygmies. They are likely descended from a full-sized species of European hippopotamus, and reached their small size through the evolutionary process of insular dwarfism which is common on islands; the ancestors of pygmy hippopotami were also small and thus there was never a dwarfing process.