Turbellarian Taxonomic Database

A listing of the taxonomy of turbellarians
(formerly class Turbellaria of the phylum Platyhelminthes)

Taxonomic search (for taxon, taxonomic authority, taxonomic literature)
  Biogeography search (by location, coordinates, authority)
  History of turbellarian research (those who conducted research on turbellarians)

database last modified: 12 March, 2014


Cite as "Tyler S, Schilling S, Hooge M, and Bush LF (comp.) (2006-2012) Turbellarian taxonomic database. Version 1.7 http://turbellaria.umaine.edu"


About turbellarians

Traditional, pre-cladistic systems placed the flatworms in a single phylum, the Platyhelminthes, subdivided into the classes Turbellaria, Monogenea, Trematoda, and Cestoda. Turbellarians are the largely free-living flatworms---those that don't parasitize other animals---while the other classes encompass the obligate parasites, most of which live in or on the bodies of vertebrates. Turbellaria is, in particular, considered an invalid class because it is not monophyletic. (It is either paraphyletic--that is, having descendants, namely the parasitic classes, that are not classified within it [Ehlers, 1985]; or it could be polyphyletic--that is, having arisen from more than one ancestor, one for the acoels and another for catenulidans and rhabditophorans [Baguñà and Riutort, 2004; Phillipé et al., 2011]). The term "turbellarian" can still be applied to those worms that were formerly classified in the Turbellaria, but the term "Turbellaria" (specifically, the capitalized taxon name) would have to be written in quotation marks to indicate its paraphyletic status. Not all turbellarians are free-living.

In recognition of recent proposals based on molecular sequences (particularly of 18s rDNA, some Hox genes, and, most recently, fuller genomic data) the system displayed here treats the Acoelomorpha as separate from the phylum Platyhelminthes. The position and status of Acoelomorpha have been volatile in molecular systematics, some claiming that it itself is paraphyletic, many claiming that it (possibly as separate taxa Acoela and Nemertodermatida) belongs near the base of the animal tree of life, as the most basal bilaterians---that is, the most primitive of any animal phylum outside of the sponges and cnidarians. The most recent genomic study (Phillipé et al., 2011), placed the Acoelomorpha within the Deuterostomia, in a phylum Xenacoelomorpha that includes also the enigmatic sack-like animal Xenoturbella); Xenacoelomorpha is placed as sister group to the Ambulacraria (Ehinoderms + Hemichordata). Significantly, the earlier proposals that Acoelomorpha was the most primitive bilaterian---a controversial claim that did not make sense in terms of the morphology of acoels---are now seen to be a result of a statistical error known as long-branch attraction. The Platyhelminthes, as defined in these molecular systems, would be only distantly related to the Acoelomorpha and classified as a lophotrochozoan phylum.

This taxonomic database covers all turbellarian flatworms, including parasitic turbellarians. The position of the major parasitic taxa (the other classes in the traditional system), encompassed now in the taxon Neodermata, is shown as proposed by cladistic systems based on morphological characters (see Baguñà and Riutort, 2004, for summary of other proposed positions of the Neodermata).

References cited


About the taxonomic listing

Louise Bush sorting turbellarians

Data in this listing were initially compiled by Louise Bush using programs developed by Seth Tyler. Dr. Bush's last update to the database was in 1991, the year of her death. Since 1991, the database has been updated by S. Tyler, Steve Schilling, and Matt Hooge, with help from specialists on various groups of turbellarian platyhelminths, including Masaharu Kawakatsu, Ulrich Ehlers, Marco Curini-Galletti, Oleg Timoshkin.

Steve Schilling collecting geographic data

Availability of images is denoted with -symbols; these link to one or more images of mostly systematic importance. Most of those of Rhabdocoela and Proseriata were kindly provided by Tom Artois and Ernest Schockaert of Universitair Centrum, Deipenbeek, Belgium; Matt Hooge, University of Maine; and Rick Hochberg, Smithsonian Institution, Fort Pierce, FL. Images of Acoela, Prolecithophora, and other Rhabdocoela were provided by Matt Hooge.

The data pertaining to the Acoelomorpha is the most reliable, having been checked more thoroughly for accurracy in synonymy and literature citations. Notes in this section (reached with the "notes" links and the -symbols by the taxon names) are transcriptions from or images of index cards that Louise Bush maintained. They summarize references to the taxa made in the literature (up to about 1991; more recent notes are separated from Bush's with a horizontal line). Notes on groups outside the Acoelomorpha are mostly in the form of images of index cards. Steve Schilling transcribed Bush's notes and scanned the cards for this database. He is also entering biogeographical data.

Entry of data on the geographic distribution of species is supported in part by the Ocean Biogeographic Information System (OBIS). Steve Schilling is handling these data, gathering collection records of turbellarian species world-wide (both marine and freshwater). Species for which data have been entered are flagged with a "dist'n hyperlink, and clicking on this hyperlink will list those records. Maps of those collection sites can be reached using the map hyperlink and the map all distribution points at the end of each listing. (Resources we use for determining geographic coordinates of collecting sites and for drawing maps [Google Maps and Topozone] are listed separately: mapping resources.)

This is a work in progress. Copyrights for images remain with the original print publishers. Please send corrections to Seth Tyler, E-Mail "styler at maine dot edu"


Explanation (electronic poster) of how the databases work

See also explanation of Platyhelminthes--the nature of a controversial phylum, which includes an explanation of Acoela and its relationship to the Platyhelminthes.



Cite as "Tyler S, Schilling S, Hooge M, and Bush LF (comp.) (2006-2012) Turbellarian taxonomic database. Version 1.7 http://turbellaria.umaine.edu"

Creative Commons License
This work is licensed under a Creative Commons License.

This material is based upon work supported by the National Science Foundation under Grant No. 0118804.