Element of Drepanoistodus suberectus, copyright Olle Hints.

Belongs within: Conodonti.

The Drepanoistodontidae are a group of conodonts known from the Ordovician possessing apparatus composed of recurved and/or geniculate coniform elements (Sweet 1988). Members of this family comprise the core of what has been recognised as the form-family Distacodontidae; however, the use of this latter name was discouraged by Sweet (1988) due to the type genus Distacodus being a nomen dubium of uncertain affinities.

Members of the basal genus Paltodus had a quinquimembrate apparatus with a geniculate coniform element in the M position and asymmetrically bicostate nongeniculate element in the P positions (Sweet 1988).

<==Drepanoistodontidae [Distacodontacea, Distacodontidae]S88
    |--Nordiodus Serpagli 1967AS93
    |--Acodina Stauffer 1940H62
    |    `--A. cuspidata (Stauffer 1940)WSQ86
    |--Decoriconus Cooper 1975AS93
    |    `--D. fragilis (Branson & Mehl 1933)AS93
    |--Acontiodus Pander 1856H62
    |    |--*A. latus Pander 1856H62
    |    `--A. franconicusLM05
    |--Distacodus Pander 1856 (n. d.)S88 [=Machairodus Pander 1856 non Kaup 1833H62; incl. Machairodia Smith 1907H62]
    |    |--*D. incurvus (Pander 1856) [=*Machairodus incurvus]H62
    |    `--D. ensiformisH62
    |--Scandodus Lindström 1955AS93
    |    |--*S. furnishi Lindström 1954DJ71
    |    |--S. flexuosusPBJ03
    |    |--S. oelandicusDJ71
    |    `--S. sinuosusPBJ03
    |--Paltodus Pander 1856S88
    |    |--*P. subequalis Pander 1856H62
    |    |--P. deltifer (Lindström 1955)AS93
    |    |--P. jemtlandicusPBJ03
    |    |--P. spuriusLM05
    |    `--P. truncatusH62
    |--Paroistodus Lindström 1971S88
    |    |--P. horridus (Barnes & Poplawski 1973)S88
    |    |--P. numarcuatusS88
    |    |--P. originalisPBJ03
    |    |--P. parallelusPBJ03
    |    `--P. proteusPBJ03
    `--Drepanoistodus Lindström 1971SS05
         |--*D. forceps (Lindström 1955) [=Oistodus forceps]SS05
         |--D. angulensisPBJ03
         |--D. basiovalisPBJ03
         |--D. concavusPBJ03
         |--D. inaequalis (Pander 1856)AS93
         |--D. latusPBJ03
         |--D. lucidusPBJ03
         |--D. nowlaniAB04
         `--D. suberectus (Branson & Mehl 1933)SS05 (see below for synonymy)

Drepanoistodus suberectus (Branson & Mehl 1933)SS05 [=Oistodus suberectusSS05, Drepanodus suberectusDJ71; incl. D. homocurvatusDJ71, Oistodus inclinatusDJ71]

*Type species of generic name indicated


[AB04] Albanesi, G. L., & S. M. Bergström. 2004. Conodonts: Lower to Middle Ordovician record. In: Webby, B. D., F. Paris, M. L. Droser & I. G. Percival (eds) The Great Ordovician Biodiversification Event pp. 312–326. Columbia University Press.

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

[DJ71] Druce, E. C., & P. J. Jones. 1971. Cambro-Ordovician conodonts from the Burke River Structural Belt, Queensland. Commonwealth of Australia, Bureau of National Development, Bureau of Mineral Resources, Geology and Geophysics, Bulletin 110: 1–159.

[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.

[LM05] Lehnert, O., J. F. Miller, S. A. Leslie, J. E. Repetski & R. L. Ethington. 2005. Cambro-Ordovician sea-level fluctuations and sequence boundaries: the missing record and the evolution of new taxa. Special Papers in Palaeontology 73: 117–134.

[PBJ03] Pyle, L. J., C. R. Barnes & Z. Ji. 2003. Conodont fauna and biostratigraphy of the Outram, Skoki, and Owen Creek Formations (Lower to Middle Ordovician), Wilcox Pass, Alberta, Canada. Journal of Paleontology 77 (5): 958–976.

[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.

[WSQ86] Wang C.-Y., Shi C.-G. & Qu G.-S. 1986. Conodonts and ostracodes from the Devonian “Heitai Formation” of Mishan County, Heilongjiang Province. Acta Micropalaeontologica Sinica 3 (2): 205–214.

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