Newly recognized Famennian lungfishes from East Greenland reveal tooth plate diversity and blur the Devonian–Carboniferous boundary

Abstract

Three lungfish specimens from the late Famennian of East Greenland are described. One forms the holotype of a new genus and species, Celsiodon ahlbergi gen. et sp. nov., which, in cladistic analyses, is placed close to the Carboniferous genus Ctenodus. The analyses reveal some Late Devonian lungfishes clustering with Early Carboniferous taxa, suggesting that Late Devonian lungfishes included more crownward taxa than previously appreciated, and that the Devonian–Carboniferous boundary was more fluid for lungfish taxa than supposed. Further study of other specimens shows a range of tooth plate morphologies and tooth crown morphologies, suggesting that the Late Devonian lungfishes were even more diverse and occupied a wider range of feeding strategies than previously suspected.

The smallest known Devonian tetrapod shows unexpectedly derived features

“…It thus changes our perception of this deposit, which has previously appeared to be completely monospecific. Thirdly, it shows a number of derived characters more in keeping with those of early Carboniferous (Mississippian) forms, echoing similar findings among lungfish taxa [16], and the reverse in early Carboniferous forms such as Lethiscus and Perittodus that show plesiomorphic characters more typical of Late Devonian forms [17,18]. Finally, its small size, in what is obviously an adult animal to judge by its state of ossification, is unprecedented in Devonian tetrapods so far known.…”

A lungfish survivor of the end-Devonian extinction and an Early Carboniferous dipnoan radiation

“…For each set of experiments, where applicable, we summarized the results in the form of a strict consensus . Characters 3, 40, 61, 72, 107 & 138 were ordered. Our character matrix requires a dataset that describes the morphological variation of both Devonian and post-Devonian taxa and so to achieve this we have used the matrix of Clack et al (2018). This dataset comprises characters used by Challands & Den Blaauwen (2016) as well as those (where not duplicated) from , the former concerning Devonian taxa exclusively, the latter Devonian-Recent taxa.…”

“…Additionally, we have recoded fifteen characters from the matrix and rerun their analysis using the parameters given above (see supplemental data). In addition to the matrix of Clack et al (2018) we have included the post-Carboniferous taxon Persephonichthys. Taxa that are only known from mandibles and tooth plates, including Chirodipterus rhenanus, Sunwapta and Holodipterus santacrucensis, were omitted from the analysis.…”

“…For instance, characters 167 and 175 (characters 22 and 37 of Schultze & Marshall 1993, respectively) are essentially different permutations of describing the arrangement of the dermal bones and so contain overlap. That said, we employ the characters used in the recent analysis of Clack et al (2018) in order to make our analysis comparable with well-established previous hypotheses that use subsections of the characters we have used. Those characters that are clear repetitions have been removed and are highlighted in the supplemental information of Clack et al (2018).…”

“…That said, we employ the characters used in the recent analysis of Clack et al (2018) in order to make our analysis comparable with well-established previous hypotheses that use subsections of the characters we have used. Those characters that are clear repetitions have been removed and are highlighted in the supplemental information of Clack et al (2018).…”