Palmatolepis (Palmatolepis)

Apparatus elements of Palmatolepis schindewolfi, from Dzik (2015).

Belongs within: Palmatolepis.

The type subgenus of Palmatolepis includes those Famennian species in which the S3–4 elements have a reduced bipennate morphology (Donoghue 2001).

The baitfish of the Late Devonian
Published 13 May 2024

Towards the end of the Devonian period, the pelagic zone of the sea was dominated by Palmatolepis. Over 100 species have been assigned to date to this genus of conodonts, known from the Frasnian and Famennian stages that make up the Late Devonian epoch. Though the exact size of a living Palmatolepis individual may be open to speculation (like most other conodonts, they are known only from the minute elements that would have functioned like teeth in the live animal), it is tempting to imagine them as the ‘anchovies’ of their time.

Pa element of Palmatolepis schindewolfi, copyright Tomáš Weiner. Scale bar = 1 mm.

The name Palmatolepis was originally associated with broad, scale-like elements (‘carminiplanate’ in the nomenclature of Sweet, 1988) with a short free blade. In life, an opposing pair of these elements would function to crush and grind food particles. The most popular reconstructions of the complete Palmatolepis apparatus place these Pa or P1 elements at the end of a sexi- or septimembrate apparatus, including a ramiform M apparatus, diverse S elements that typically have teeth of alternating lengths, and a more-or-less boomerang-shaped Pb process with a strong central cusp (Sweet 1988). However, because the apparatus associations have not yet been established for many species, Palmatolepis taxonomy has tended to focus heavily on the Pa element alone.

With so many species to keep track of, many authors have divided Palmatolepis into multiple subgenera. Some have gone so far as to raise these to the status of separate genera. The name Palmatolepis would then be restricted to the type subgenus, including species with M element processes following a single line, S elements with weakly developed cusps and irregularly arranged denticles, and a lobate platform on the Pa element (Dzik 2002). However, the majority of authors continue to recognise the genus in its broad sense. A cladistics analysis of selected Palmatolepis species by Donoghue (2001) was unable to support monophyly for any of the subgenera other than the type assemblage. Palmatolepis sensu stricto radiated during the Famennian stage with only a single species P. linguiformis distinguishable from the latest Frasnian (Girard et al. 2007).

Section of Palmatolepis evolutionary tree, showing Pa elements of subgenus Palmatolepis, from Sweet (1988).

Because of their abundance at the time, Palmatolepis species have held a lot of significance for biostratigraphy. The boundary between the Frasnian and Famennian stages was marked by the Kellwasser event, a major extinction event that severely impacted many marine taxa including Palmatolepis. Most of the Palmatolepis species found before the event went extinct, the few survivors (including Palmatolepis sensu stricto) radiating after the event’s close. However, the latter part of the Famennian would see a second decline in Palmatolepis’ fortunes, and the once-dominant genus would be gone by the opening of the Carboniferous.

Systematics of Palmatolepis (Palmatolepis)
<==Palmatolepis Ulrich & Bassler 1926 (Palmatolepis)M62
    |  i. s.: P. (P.) cymbulaM62
    |         P. (P.) humboldtiM62
    |         P. (P.) wolskae Ovnatanova 1969D01
    |--+--P. (P.) crepidaS88
    |  `--P. (P.) terminiS88
    `--+--+--P. grossi [=P. perlobata grossi]S88
       |  `--P. (P.) rugosa Branson & Mehl 1934D01
       |       |--P. r. rugosaS88
       |       |--P. r. amplaS88
       |       `--P. r. trachyteraS88
       `--+--*P. (P.) perlobata Ulrich & Bassler 1926D02, D01
          |    |--P. p. perlobataD01
          |    |--P. p. maxima Müller 1956D01
          |    |--P. p. posteraS88
          |    `--P. p. sigmoideaS88
          |--P. helmsi Ziegler 1962KU04 [=P. perlobata helmsiS88]
          `--P. (P.) schindewolfi Müller 1956D01 [=P. perlobata schindewolfiS88]

*Type species of generic name indicated

References

[D01] Donoghue, P. C. J. 2001. Conodonts meet cladistics: recovering relationships and assessing the completeness of the conodont fossil record. Palaeontology 44 (1): 65–93.

[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.

Girard, C., S. Renaud & R. Feist. 2007. Morphometrics of the Late Devonian conodont genus Palmatolepis: phylogenetic, geographical and ecological contributions of a generic approach. Journal of Micropalaeontology 26: 61–72.

[KU04] Klapper, G., T. T. Uyeno, D. K. Armstrong & P. G. Telford. 2004. Conodonts of the Williams Island and Long Rapids Formations (Upper Devonian, Frasnian–Famennian) of the Onakawana B Drillhole, Moose River Basin, northern Ontario, with a revision of the Lower Famennian species. Journal of Paleontology 78: 371–387.

[M62] Müller, K. J. 1962. Taxonomy, evolution, and ecology 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. W83–W91. Geological Society of America, and University of Kansas Press.

[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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