Micrichnus is a trace fossil ichnogenus of arthropods. It was once thought to be a trace fossil made by a vertebrate.
Book: Glut, Donald F. . Dinosaurs: The Encyclopedia. 3rd Supplement . 2003 . McFarland & Company, Inc. . Jefferson, North Carolina . 0-7864-1166-X . Appendix: Dinosaur Tracks and Eggs . 613–652 . registration . https://archive.org/details/dinosaursencyclo00glut_2 .