Paedomorphosis and neurocranial ossification in two Devonian lungfishes
Lungfishes are one of the few early vertebrate clades with a rich 410-million-years-old fossil record. Lungfishes are characterized by a low evolutionary rate assumed to be associated with paedomorphosis since the Late Devonian. Lungfish paedomorphic trends include a reduction of the number of med...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Institute of Paleobiology PAS
2022-06-01
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| Series: | Acta Palaeontologica Polonica |
| Subjects: |
| Summary: | Lungfishes are one of the few early vertebrate clades with a rich 410-million-years-old fossil record. Lungfishes are
characterized by a low evolutionary rate assumed to be associated with paedomorphosis since the Late Devonian.
Lungfish paedomorphic trends include a reduction of the number of median fins, reduction of the number of cranial
dermal bones, and reduction of the degree of neurocranial ossification. This neurocranial trait has evolved from heavily
ossified in Devonian species to completely cartilaginous in post-Devonian species. Neurocranial conditions among derived
Devonian lungfishes are needed to have a better understanding of paedomorphosis as a driving force during lungfish
evolution. The neurocrania of two Devonian species, Scaumenacia curta (middle Frasnian, Escuminac Formation,
eastern Canada) and Pentlandia macroptera (Givetian, Orcadian Basin, Scotland), have been micro-CT-scanned. These
species were assumed to have a cartilaginous neurocranium like other “phaneropleurids” and “fleurantids”. Juvenile (or
sub-adult) and adult specimens of S. curta possess cartilaginous neurocrania, whereas P. macroptera is now recognized
to have a poorly ossified neurocranium. Pyrite filled neurocranial cavities preserving some endocranial structures (e.g.,
olfactory bulbs, semicircular canals) allow us to code for phylogenetic endocranial characters in S. curta. This unique
mode of preservation suggests that occasionally pyrite is a preservative rather than a destructive diagenetic agent. In the
evolutionary gap between Pentlandia and Scaumenacia, paedomorphosis had already resulted in reduction of neurocranial
ossification while little changes occurred in cranial dermal bones. |
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| ISSN: | 0567-7920 1732-2421 |