Zygognathus pyramidalis, from Hass (1962).

Belongs within: Prioniodontida.

The Cyrtoniodontidae is a group of conodonts known from the Ordovician (Hass 1962). The type species and form taxon Cyrtoniodus complicatus may represent the M element of Phragmodus cognitus (Sweet 1988).

Characters (from Hass 1962, for S elements only): Main cusp terminal; aboral side of posterior bar partly or wholly expanded into concavity; anticusp, if present, may be denticulated.

<==Cyrtoniodontidae [Cyrtoniodontinae, Phragmodontidae]
    |--Cyrtoniodus Stauffer 1935 [incl. Barbarodina Stauffer 1935]H62
    |    `--*C. complicatus Stauffer 1935H62
    |--Gothodus Lindström 1954H62
    |    `--*G. costulatus Lindström 1954H62
    |--Holodontus Rhodes 1953H62
    |    `--*H. superbus Rhodes 1953H62
    |--Keislognathus Rhodes 1955H62
    |    `--*K. gracilis Rhodes 1955H62
    |--Peridon Hadding 1913H62
    |    `--*P. aculeatus Hadding 1913H62
    |--Rhynchognathodus Ethington 1959 [=Rhynchognathus Ethington 1959 non Jaekel 1929]H62
    |    `--*R. typica (Ethington 1959) [=*Rhynchognathus typica]H62
    |--Bryantodina Stauffer 1935S88
    |    `--*B. typicalis Stauffer 1935H62
    |--Zygognathus Branson, Mehl & Branson 1951 [incl. Eoligonodina Branson, Mehl & Branson 1951]H62
    |    |--*Z. pyramidalis Branson, Mehl & Branson 1951H62
    |    `--Z. robustaH62
    `--Phragmodus Branson & Mehl 1933S88
         |--*P. primus Branson & Mehl 1933H62
         |--P. cognitusS88
         |--P. flexuosusS88
         |--P. harrisi Bauer 1989AS93
         |--P. inflexusS88
         `--P. undatus Branson & Mehl 1933AS93

*Type species of generic name indicated


[AS93] Aldridge, R. J., & M. P. Smith. 1993. Conodonta. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 563–572. Chapman & Hall: London.

[H62] Hass, W. H. 1962. Conodonts. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt W. Miscellanea: Conodonts, Conoidal Shells of Uncertain Affinities, Worms, Trace Fossils and Problematica pp. W3–W69. Geological Society of America, and University of Kansas Press.

[SS05] Sansom, I. J., & M. P. Smith. 2005. Late Ordovician vertebrates from the Bighorn Mountains of Wyoming, USA. Palaeontology 48 (1): 31–48.

[S88] Sweet, W. C. 1988. The Conodonta: Morphology, taxonomy, paleoecology, and evolutionary history of a long extinct animal phylum. Clarendon Press: Oxford.

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