ケヤキ
Today, the genus comprises six species with disjunct distribution patterns: three in eastern Asia ["Zelkova serrata" (Thunb.) Makino; "Zelkova schneideriana" Hand.-Mazz.; and "Zelkova sinica" C. K. Schneid.], one in southwestern Asia ["Zelkova carpinifolia" (Pall.) C. Koch] and two on the Mediterranean islands of Sicily ("Zelkova sicula" Di Pasq., Garfi &amp; Quézel) and Crete [Z"elkova abelicea" (Lam.) Boiss.]. The oldest fossils attributed to "Zelkova" date from the early Eocene (55 million years ago) in western North America, where the genus is extinct today. In Bulgaria, "Zelkova" fossils were found in Paleogene and Neogene layers in the following locations: "Zelkova ungeri" (Ett.) Kov. — Lozenets, Kurilo, Chukurovo in Sofia Region, Dospey in Samokov Region, Pernik, Pirin Mine in Blagoevgrad Region, Bobov Dol in Kyustendil Region; "Zelkova praelonga" Berger — Pirin Mine in Blagoevgrad Region.