Panderodontida

Isolated element of Panderodus equicostatus, from fossilid.info.

Belongs within: Conodonti.

The Panderodontida are a  group of conodonts with the apparatus composed of simple coniform elements, the largest elements being towards the front (Dzik 1991).

Conodonts: they just got scarier
Published 15 December 2009
Reconstructed apparatus of Besselodus arcticus, from Dzik (1991).

I’ve told you before about conodonts, Palaeozoic microcarnivores with impressive tooth arrays. In the earlier post, I referred mostly to ozarkodinids, later conodonts that had grasping teeth in the front of their mouths and crushing plates towards the back. In this post, I’ll be referring to panderodontids, an earlier group that lacked the crushing plates of ozarkodinids and had a tooth apparatus made up of simpler fang-like elements, similar to the reconstruction above. Apparatus of panderodontids have been found preserved in association, but we don’t yet have preserved examples as good as available for the ozarkodinids.

With such different apparatus, panderodontids were obviously capturing and processing prey differently to ozarkodinids, and a paper just out by Szaniawski (2009) suggests one of those differences. Panderodontids and many other conodonts with coniform teeth had long grooves on the inner surface of some of their teeth (as seen in the photo of a Dapsilodus mutatus element above from Szaniawski, 2009) and Szaniawski points out that these grooves are extremely similar to those seen in the fangs of many venomous fish, lizards and snakes. He therefore infers that panderodontids were similarly venomous. As well as making conodont apparatus even more impressive than they already were, this would make panderodontids the earliest known venomous chordates*.

*Szaniawski refers to them as the “oldest known venomous animals”. However, cnidarians had already been around for some time, and while the cnidarian venom delivery system doesn’t fossilise, the fact that these were crown-group cnidarians makes it a pretty sure bet that they had it by then.

Earlier suggestions that the groove provided an anchoring point for muscles were couched in the belief that conodont elements were permanently internal, a view that is no longer standard*. Other forms of conodont lacked the venom groove, further evidence of the conodonts’ ecological diversity.

*Conodont elements grew as new layers were put down over the outer surface, which is admittedly a little difficult to reconcile with their current interpretation as grasping teeth (which would require the absence of tissue cover). It seems likely that conodont teeth were only exposed when being actively used; at other times they would have been retracted into a covering pocket, in the same manner as the grasping spines of modern chaetognaths.

Systematics of Panderodontida
<==Panderodontida
    |--BelodellidaeD02
    |    |--Stolodus Lindström 1955S88
    |    |    `--S. stola (Lindström 1955)AS93
    |    `--+--Walliserodus Serpagli 1967S88
    |       |    |--W. curvatus (Branson & Branson 1947)WBN02 (see below for synonymy)
    |       |    |--W. declivisPBJ03
    |       |    |--W. ethingtoniPBJ03
    |       |    `--W. sancticlairiMS12
    |       `--+--Dvorakia Klapper & Barrick 1983S88
    |          `--Belodella Ethington 1959S88
    |               |--*B. devonica (Stauffer 1940) [=Belodus devonicus]D02
    |               |--B. anomalisJT12
    |               |--B. minutidentata Dzik 2002D02
    |               |--B. resima (Philip 1965)D02
    |               |--B. robustidentata Dzik 2002D02
    |               `--B. tenuiserrata Dzik 2002D02
    `--PanderodontidaeSD01
         |  i. s.: Neopanderodus Ziegler & Lindström 1971S88
         |           `--N. perlineatus Ziegler & Lindström 1971AS93
         |         Zanclodus Nowlan & McCracken 1988AS93
         |--+--Culumbodina Moskalenko 1973S88
         |  |    `--C. pennaS88
         |  `--Belodina Ethington 1959S88
         |       |--*B. grandis (Stauffer 1935) [=Belodus grandis]M62
         |       |--B. calciprominensS88
         |       |--B. compressaS88
         |       |--B. confluensSS05
         |       `--B. monitorensisS88
         `--+--Parabelodina Sweet 1979S88
            |    `--P. denticulataS88
            |--Plegagnathus Ethington & Furnish 1959S88
            |    `--*P. nelsoni Ethington & Furnish 1959M62
            |--Pseudobelodina Sweet 1979S88
            |    |--P. dispansaNW04
            |    |--P. inclinataS88
            |    |--P. kirkiS88
            |    |--P. obtusaS88
            |    `--P. vulgarisS88
            `--Panderodus Ethington 1959S88 [incl. Pseudopanderodus Landing 1979AS93]
                 |--*P. unicostatus (Branson & Mehl 1933) [=Paltodus unicostatus]SS05
                 |--P. bergstroemiS88
                 |--P. deuteroconusMS12
                 |--P. equicostatus (Rhodes 1953) [=Paltodus equicostatus]SS05
                 |--P. gracilis (Branson & Mehl 1933)WBN02
                 |--P. greenlandensis Armstrong 1990M02
                 |--P. langkawiensisMS12
                 |--P. panderiMS12
                 |--P. recurvatus (Rhodes 1953)MS12
                 |--P. serratusJT12
                 `--P. sulcatus (Fåhraeus 1966)AS93

Walliserodus curvatus (Branson & Branson 1947)WBN02 [incl. Paltodus acostatus Branson & Branson 1947SS05, Panderodus acostatusSS05]

*Type species of generic name indicated

References

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

Dzik, J. 1991. Evolution of oral apparatuses in the conodont chordates. Acta Palaeontologica Polonica 36 (3): 265–323.

[D02] Dzik, J. 2002. Emergence and collapse of the Frasnian conodont and ammonoid communities in the Holy Cross Mountains, Poland. Acta Palaeontologica Polonica 47: 565–650.

[JT12] Jeppsson, L., J. A. Talent, R. Mawson, A. Andrew, C. Corradini, A. J. Simpson, J. Wigforss-Lange & H. P. Schönlaub. 2012. Late Ludfordian correlations and the Lau Event. In: Talent, J. A. (ed.) Earth and Life: Global biodiversity, extinction intervals and biogeographic perturbations through time pp. 653–675. Springer.

[M02] Männik, P. 2002. Conodonts in the Silurian of Severnaya Zemlya and Sedov archipelagos (Russia), with special reference to the genus Ozarkodina Branson & Mehl, 1933. Geodiversitas 24 (1): 77–97.

[MS12] Molloy, P. D., & A. J. Simpson. 2012. An analysis of the Ireviken Event in the Boree Creek Formation, New South Wales, Australia. In: Talent, J. A. (ed.) Earth and Life: Global biodiversity, extinction intervals and biogeographic perturbations through time pp. 615–630. Springer.

[M62] Müller, K. J. 1962. Supplement to systematics of 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. W246–W249. Geological Society of America, and University of Kansas Press.

[NW04] Nitecki, M. H., B. D. Webby, N. Spjeldnaes & Zhen Y.-Y. 2004. Receptaculitids and algae. In: Webby, B. D., F. Paris, M. L. Droser & I. G. Percival (eds) The Great Ordovician Biodiversification Event pp. 336–347. Columbia University Press.

[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.

[SD01] Sweet, W. C., & P. C. J. Donoghue. 2001. Conodonts: past, present, future. Journal of Paleontology 75 (6): 1174–1184.

Szaniawski, H. 2009. The earliest known venomous animals recognized among conodonts. Acta Palaeontologica Polonica 54 (4): 669–676.

[WBN02] Won, M.-Z., R. B. Blodgett & V. Nestor. 2002. Llandoverian (Early Silurian) radiolarians from the Road River Formation of east-central Alaska and the new family Haplotaeniatumidae. Journal of Paleontology 76 (6): 941–964.

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