A new classification scheme based on significant morphological features (ichnotaxobases) is proposed for major trace-fossil groups, such as burrows, bioerosional trace fossils, trackways, imprints, and trails. All ichnogenera currently regarded as valid (n=585), together with additional invalid ichnogenera, are listed together with recent references for more detailed data. A critical review shows that the number of valid ichnogenera erected after the last compilation of invertebrate ichnogenera in the Treatise on Invertebrate Paleontology, Part W, by Häntzschel (1975) has more than doubled. Burrows are by far the largest subdivision of them (60%), followed by bioerosional trace fossils (17%), trackways (14%), imprints (5%), and trails (4%). This classification scheme is intended to serve as a solid basis for further ichnotaxonomical work toward a more stable trace-fossil systematics and aims for an improved integration of ichnological and sedimentological data. As a next step, it could be the basis of a searchable online database.