Keratosperma allenbyensis seeds from the Middle Eocene Allenby Formation near Princeton, British Columbia were reexamined from over 200 new specimens. Anatomical characters have shown their affinities to seeds of Araceae, Subfamily Lasioideae. The seeds were reexamined using the cellulose acetate peel technique modified for hydrofluoric acid. Seeds are campylotropous with three rows of spiny ridges on the integument. Idioblasts that contained raphides are found scattered in the outer integument. The micropylar end of the seed shows an epistase and a thin micropylar cover that was easily displaced at the time of germination. At the chalazal end of the seed a prominent hypostase and podium are present. Endosperm tissue and monocotoledonary embryos are present in some but in most specimens these tissues have been invaded by fungi. Anatomical comparisons with the extant lasioids Cyrtosperma ferox Linden et N. E. Br. and Urospatha sagittifolia (Rodsch.) Schott were made using paraffin and cryo embedding and sectioning techniques. A reconstruction of the fossil seed was made from serial sections allowing the fossils to be compared to extant taxa based on external morphology. Affinities of Keratosperma were originally believed to be with Cyrtosperma from tropical southeast Asia. While shape is most similar to seeds of Urospatha from Central and South America, integumentary zones are distinctly different making these seeds unique. Keratosperma allenbyensis are the oldest known lasioid seeds in the fossil record and represent an extinct araceous lasioid taxon.

Key words: Araceae, Eocene, Keratosperma, seeds