Wastebasket taxon(also called awastebin taxon,[1]dustbin taxon[2]orcatch-all taxon[3]) is a term used by sometaxonomiststo refer to ataxonthat has the purpose of classifying organisms that do not fit anywhere else. They are typically defined by either their designated members' often superficial similarity to each other, or theirlackof one or more distinctcharacter statesor by theirnotbelonging to one or more other taxa. Wastebasket taxa are by definition eitherparaphyleticorpolyphyletic,and are therefore not considered valid taxa under strictcladisticrules of taxonomy. The name of a wastebasket taxon may in some cases be retained as the designation of anevolutionary grade,however.
The term was coined in a 1985 essay byStephen Jay Gould.[4][5]
Examples
editThere are many examples of paraphyletic groups, but true "wastebasket" taxa are those that are known not to, and perhaps not intended to, represent natural groups, but are nevertheless used as convenient groups of organisms. Theacritarchsare perhaps the most famous example. Wastebasket taxa are often old (and perhaps not described with the systematic rigour and precision that is possible in the light of accumulated knowledge of diversity) and populous.[6]
- TheFlacourtiaceae,a now-defunct family offlowering plants[7]– theAngiosperm Phylogeny Grouphas placed itstribesand genera in various other families, especially theAchariaceaeandSalicaceae.
- The obsolete kingdomProtistais composed of alleukaryotesthat are notanimals,plantsorfungi,leaving to the protists all single-celled eukaryotes.[8]
- TheTricholomataceaeis a fungal group, at one point composed of the white-, yellow-, or pink-spored genera in theAgaricalesnot already classified as belonging to theAmanitaceae,Lepiotaceae,Hygrophoraceae,Pluteaceae,orEntolomataceae.[9]
- CarnosauriaandThecodontiaare fossil groups, banded together back when the limited fossil record did not allow for a more detailed scheme.
- Condylarthrais an artificial clade into which ungulate mammals not clearly withinPerissodactylaorCetartiodactylawere traditionally shoved. Many of these groups, likeMeridiungulataorProtungulatum,may not representlaurasitherianmammals, while others likephenacodontidshave been clearly established as early odd-toed ungulates.[10][11]
- The orderInsectivorahas traditionally been used as a dumping ground for placental insectivorous mammals (and similar forms such ascolugos), usually aligned withcarnivorans,ungulatesandbats.While the core components (moles,shrews,hedgehogsand their close relations) do in fact form a consistent clade,Eulipotyphla,that is part ofLaurasiatheriawith the aforementioned clades, other mammals historically placed in the order have been found to belong to other branches of the placental tree:tree shrewsand colugos areeuarchontansrelated toPrimatesand sometimes grouped inSundatheria,whiletenrecs,golden molesandelephant shrewsare allafrotheres,probably forming the cladeAfroinsectiphilia.Both of these clades have at times been accused of being wastebasket taxa themselves, grouping superficially similar animals in Euarchonta and Afrotheria, respectively, but they have been more strongly supported by genetic studies.[citation needed]
- Vermesis an obsolete taxon of worm-like animals. It was a catch-all term used byCarl LinnaeusandJean-Baptiste Lamarckfor non-arthropod invertebrate animals.
- The genusMamenchisaurusis sometimes considered a wastebasket taxon for large, long-neckeddinosaurs.[12]
Wastebasket taxa in science
editFossilgroups that are poorly known due to fragmentary remains are sometimes grouped together on gross morphology orstratigraphy,only later to be found to be wastebasket taxa, such as the crocodile-likeTriassicgroupRauisuchia.[13]
One of the roles of taxonomists is to identify wastebasket taxa and reclassify the content into more natural units. Sometimes, during taxonomic revisions, a wastebasket taxon can be salvaged after doing thorough research on its members, and then imposing tighter restrictions on what continues to be included. Such techniques "saved" Carnosauria andMegalosaurus.Other times, thetaxonomicname contains too much unrelated "baggage" to be successfully salvaged. As such, it is usually dumped in favour of a new, more restrictive name (for example,Rhynchocephalia), or abandoned altogether (for example,Simia).[citation needed]
Related concepts
editA related concept is that ofform taxon,"wastebasket" groupings that are united by gross morphology. This is often result of a common mode of life, often one that isgeneralist,leading to generally similar body shapes byconvergent evolution.[citation needed]
The term wastebasket taxon is sometimes employed in a derogatory fashion to refer to anevolutionary gradetaxon.[citation needed]
See also
editReferences
edit- ^Friedman, M.; Brazeau, M.D (7 February 2011)."Sequences, stratigraphy and scenarios: what can we say about the fossil record of the earliest tetrapods?".Proceedings of the Royal Society.278(1704): 432–439.doi:10.1098/rspb.2010.1321.PMC3013411.PMID20739322.
- ^Hallam, A.;Wignall, P. B. (1997).Mass extinctions and their aftermath.Oxford [England]: Oxford University Press. p. 107.ISBN978-0-19-854916-1.
- ^Monks, N. (July 2002)."Cladistic analysis of a problematic ammonite group: the Hamitidae (Cretaceous, Albian-Turonian) and proposals for new cladistic terms".Palaeontology.45(4): 689–707.Bibcode:2002Palgy..45..689M.doi:10.1111/1475-4983.00255.
- ^Gould, S. J. (1985). "Treasures in a taxonomic wastebasket".Natural History.94:22–33.
- ^Plotnick, Roy E.; Wagner, Peter J. (2006). "Round up the Usual Suspects: Common Genera in the Fossil Record and the Nature of Wastebasket Taxa".Paleobiology.32(1): 126–146.Bibcode:2006Pbio...32..126P.doi:10.1666/04056.1.JSTOR4096821.S2CID86606882.
- ^Plotnick, Roy E.; Wagner, Peter J. (2006). "Round up the Usual Suspects: Common Genera in the Fossil Record and the Nature of Wastebasket Taxa".Paleobiology.32(1): 126–146.Bibcode:2006Pbio...32..126P.doi:10.1666/04056.1.JSTOR4096821.S2CID86606882.
- ^Chase, Mark W.; Sue Zmarzty; M. Dolores Lledó; Kenneth J. Wurdack; Susan M. Swensen; Michael F. Fay (2002). "When in doubt, put it in Flacourtiaceae: a molecular phylogenetic analysis based on plastidrbcLDNA sequences ".Kew Bulletin.57(1): 141–181.Bibcode:2002KewBu..57..141C.doi:10.2307/4110825.JSTOR4110825.
- ^Whittaker RH (January 1969). "New concepts of kingdoms or organisms. Evolutionary relations are better represented by new classifications than by the traditional two kingdoms".Science.163(3863): 150–60.Bibcode:1969Sci...163..150W.CiteSeerX10.1.1.403.5430.doi:10.1126/science.163.3863.150.PMID5762760.
- ^Young AM (2002). "Brief notes on the status of Family Hygrophoraceae Lotsy".Australasian Mycologist.21(3): 114–6.
- ^Naish, Darren (8 August 2013)."Phenacodontidae, I feel like I know you".Tetrapod Zoology.Scientific American.
- ^Cooper, Lisa Noelle; Seiffert, Erik R.; Clementz, Mark; Madar, Sandra I.; Bajpai, Sunil; Hussain, S. Taseer; Thewissen, J. G. M. (2014)."Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls".PLOS ONE.9(10): e109232.Bibcode:2014PLoSO...9j9232C.doi:10.1371/journal.pone.0109232.PMC4189980.PMID25295875.
- ^Moore, A.J.; Upchurch, P.; Barrett, P.M.; Clark, J.M.; Xing, X. (2020). "Osteology ofKlamelisaurus gobiensis(Dinosauria, Eusauropoda) and the evolutionary history of Middle–Late Jurassic Chinese sauropods ".Journal of Systematic Palaeontology.18(16): 1299–1393.Bibcode:2020JSPal..18.1299M.doi:10.1080/14772019.2020.1759706.S2CID219749618.
- ^Nesbitt, Sterling J. (2003)."Arizonasaurus and its implications for archosaur divergence".Proceedings of the Royal Society B: Biological Sciences.270(Suppl 2): S234-7.doi:10.1098/rsbl.2003.0066.PMC1809943.PMID14667392.