Lithornithidae is an extinct, possibly paraphyletic clade of early paleognath birds. They are known from fossils dating to the Upper Paleocene through the Middle Eocene of North America and Europe, with possible Late Cretaceous representatives. All are extinct today.Lithornithids had long, slender, bills for probing. They closely resembled modern tinamous. They possessed a rhynchokinetic skull with relatively unfused cranial bones, a weakly fused pygostyle and a splenial.