A dipluran, a common if confusing arthropod. Photographed in Urbana, Illinois.
Yesterday’s challenge was an unusual one, in that our ”What Is It?” lacks singular correct answers.
Our uncertainty is paradoxical, because on one hand this thing is obviously a dipluran- a small, entognathous hexapod. The formal classification is a different matter, however, and the problem stems from two distinct types of uncertainty.
First, formal studies suggest conflicting evolutionary relationships of Diplura. Some place these squishy little hexapods as sister to a strictly-defined Insecta, others as sister to Protura. The pattern of their descent remains unsettled. Second, philosophical differences over the best way to define these groups, and where to place our arbitrary ranks of Class, Order, Suborders, and so forth, means different researchers have settled on different taxonomic schemes. This, layered on a background of phylogenetic confusion.
So it is that a common animal can be defended as an insect, or a non-insect hexapod, its ordinal rank being Diplura, or Rhabdura.
Anyway. I will award points as follows:
5 to Thomas Shahan for being lightning-fast to suggest Diplura over on facebook. 5 points to Christopher Taylor for a thoughtful discussion of the problem. 2 points each to Guillaume D, GregZ, Dave, and Christopher Moore for their contributions. And, 2 points to Michael Suttkus for a point well made.