In the late 19th century, when Scottish physician and naturalist Ramsay Heatley Traquair first acquired specimens of a “strange little fossil vertebrate” from Achanarras Quarry in Caithness, Scotland, he likely had no idea that he would soon stumble on a mystery that would confound paleontologists for over a century.
“The comparatively few feet of rock exposed in this quarry afford a remarkable assemblage of fossil fishes,” he wrote in 1890. Among them was a tiny fish fossil that proved difficult to classify. He named it Paleospondylus gunni. Paleospondylus means ancient vertebrae in Greek, but gunni is an old Scottish term for a bugbear, or boogeyman. It’s been a boogeyman among paleontologists ever since (though often a dull one), with bizarre features that have defied easy classification.