Dendrcystoides scoticus Carpoid from Scotland

Description: I have recently been able to acquire a number of specimens coming from the famous Upper Ordovician Lady Burn Starfish Beds of the Girvan District of Scotland. While it is the most important starfish locality in the British Isles, it also contains a diverse representation of trilobites, crinoids, carpoids and others. Specimens from the locality are not often made available, so this diverse grouping is most uncommon. This plate contains an excellent example of the carpoid Dendrocystoides scoticus. The species name derivation is obvious. The carpoids are one of the most contentious groups of fossil organisms known. While they have been studied for over 150 years, their unique character combinations have caused a number of disputes over both their paleobiology and relationships. While some place them in the Echinodermata, their lack of pentaradial symmetry calls that placement into question. Additionally many carpoids are thought to have possessed gill slits, a feature characteristic of chordates and hemichaordates. Many possess one or two “appendages” which have been interpreted variously as feeding tubes, tails with notocords and muscular feet. The carpoid body was supported by a skeleton of calcitic plates like those found in modern Echinoderms. Some believe that a carpoid may have been the common ancestor between Echinoderms and Vertebrates. It is important to note the carpoids differ from ALL other animals, living and extinct, in that many are completely asymmetrical. With so much debate over assignment of the appendages to specific functions, how can one come to a conclusion about their assignment in the Tree of Life?.