Fossil harvestmen: The oldest surviving arachnids

Abstract

You may never have heard of a harvestman before. And you might think they are entirely unimportant. To the arachnophobes amongst you, they may be a cause of much fear. The odds are, though, that you have seen one these arachnids in the past: there may well be some in your home, or wherever you’re reading this right now, and there are actually more species of harvestmen alive than there are extant species of mammals. We hope to convince you in the course of this article that they are really cool creatures. They are nothing to be afraid of, but they do deserve a little respect. Harvestmen have been around for a very long time, are biologically interesting, and make important contributions to ecosystems. They’re also increasingly useful as model organisms–creatures scientists can use to understand animal development and evolution. This article stems from a paper we wrote in 2011. While we’ll introduce the group as a whole, and their fossil record, some this article will focus on animals from a particular time (the Carboniferous; 360–299 million years ago) which we have studied with a neat technique (high resolution CT scanning). But we’ll first introduce early life on land, based on what we know from the fossil record. Not because it’s particularly important to this study, but because it’s really interesting. We’ll then: outline the fossil harvestmen we already know about; introduce our time period, the last part of the Carboniferous; and explain CT scanning. Finally, we’ll introduce the really exciting new fossils which were the basis of our paper. So, let’s start by having a look at life on land.