[8][1] The Cretaceous fossil wood, Xenoxylon, is known from China,[9] South Korea, Japan, Manchuria, Siberia, and many other northern hemisphere sites[7] and corresponds to no modern plant.

)[10] Xenoxylon trees lived in a paleoclimate which was temperate to cool temperate, and in wet environments,[9] and the presence of Xenoxylon is an effective marker of global climate change in the Mesozoic era.

[11] Xenoxylon is distinguished from other conifer-like fossil genera by having "clusters of very flattened pits ... on radial tracheid walls", [7] while Gothan's protologue describes Xenoxylon as "wood distinguished by the large oopores of the medullary rays and the very large areolate pits, which are uniseriate and strongly flattened on both sides because of the dense arrangement".

[3] The fossil genera Sciadopityoxylon Schmalhausen, and Trematoxylon Hartig are thought to be probable synonyms.

[3] Xenoxylon latiporosum has very flattened radial pits (twice as wide as they are high).