Field of Science

There Goes "Dicynodon" Biostratigraphy!

In the latest Journal of Vertebrate Paleontology Memoir Christian Kammerer, Kenneth Angielczyk, and Jörg Fröbisch (an allstar team of synapsid workers) readily handle the taxonomic mess more commonly known as Dicynodon. They find that the taxon is polyphyletic, is restricted to two species, and reassign all of the other material to a variety of old and new genera. Moreover, I think that their abstract sets a record for the number of included taxonomic names. 

Hey guys, want to tackle "Rutiodon" next?

Kammerer, C. F., Angielczyk, K. D., and J. Fröbisch. 2011. A comprehensive taxonomic revision of Dicynodon (Therapsida, Anomodontia) and its implications for dicynodont phylogeny, biogeography, and biostratigraphy. Journal of Vertebrate Paleontology 31, Supplement 1: 1-158 DOI:10.1080/02724634.2011.627074

Abstract - The dicynodont wastebasket genus Dicynodon is revised following a comprehensive review of nominal species. Most nominal species of Dicynodon pertain to other well-known dicynodont genera, especially Oudenodon and Diictodon. Of the Karoo Permian species that are referable to "Dicynodon" sensu lato, we recognize four common, valid morphospecies: Dicynodon lacerticeps, D. leoniceps, D. woodwardi, and Dinanomodon gilli, comb. nov. Eleven additional species of "Dicynodon" are recognized worldwide: D. alticeps, D. amalitzkii, D. bathyrhynchus, D. benjamini, D. bogdaensis, D. huenei, D. limbus, D. sinkianensis, D. traquairi, D. trautscholdi, and D. vanhoepeni. Morphometric analysis of D. lacerticeps and D. leoniceps specimens recovers statistically significant separation between these species in snout profile and squamosal shape, supporting their distinction. A new phylogenetic analysis of Anomodontia reveals that "Dicynodon" is polyphyletic, necessitating taxonomic revision at the generic level. D. benjamini and D. limbus are basal cryptodonts, whereas the other valid "Dicynodon" species are basal dicynodontoids. The genus Dicynodon is restricted to D. lacerticeps and D. huenei. We reinstate use of Daptocephalus, Sintocephalus, Turfanodon, Daqingshanodon, Jimusaria, and Gordonia for other species. We synonymize Vivaxosaurus permirus and Dicynodon trautscholdi (as V. trautscholdi, comb. nov.) We establish new generic names for several species formerly included in Dicynodon: Peramodon amalitzkii, comb. nov., Keyseria benjamini, comb. nov., Euptychognathus bathyrhynchus, comb. nov., Syops vanhoepeni, comb. nov., and Basilodon woodwardi, comb. nov. Of the main Karoo Permian taxa, Dicynodon, Basilodon, and Dinanomodon range throughout the Cistecephalus and Dicynodon assemblage zones, but Daptocephalus is restricted to the Dicynodon Assemblage Zone.

1 comment:

  1. Thanks for the shout-out! Very happy that this is finally published. We're probably not going to turn our attentions to Rutiodon any time soon, but stay tuned for more big synapsid revisions in the coming year. Nothing quite on the magnitude of Dicynodon, but after you've gone through a genus with 168 species ranging from the Wordian to the Norian nothing else seems quite as bad (I can't even think of any other Paleozoic vertebrates with as expansive and problematic an alpha taxonomy...maybe Bothriolepis?) Incidentally, "Rutiodon" (sensu dumping ground for all Newark phytosaurs) is somewhat relevant to our monograph--we argue that Cope's Dicynodon rosmarus from the Lockatong of Pennsylvania was probably phytosaurian. Unfortunately it's all circumstantial evidence--Cope initially described this taxon in a few sentences, noting that illustrations and a more detailed description would follow. They never did, and the specimen has since been lost. As such we call it a nomen dubium, but speculating a bit on its identity, the original description sounds a lot more like the recurved teeth in a phytosaur terminal rosette than a dicynodont tusk, and all the other dental material from Cope's Wheatley mine collection is phytosaurian. It actually makes me wonder if there wasn't some skullduggery involved in the loss of the type--all the other specimens Cope described from that locality are safely housed at the AMNH and D. rosmarus was clearly lost before this collection ever arrived at the museum (there is no record of its accession with the other specimens). If it was a phytosaur tooth, being a smart guy I'm sure Cope would have figured out its true identity after seeing any complete phytosaur skulls. But coming right on the heels of his Elasmosaurus debacle and given his strong desire not to be caught with his pants down on any more misidentifications, I would not be surprised if the D. rosmarus type simply "disappeared" before anyone else had a chance to see or illustrate it. Pure speculation on my part, mind you, but you have to wonder...

    -Christian

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