Paleontologists have reexamined old museum collections of Late Triassic fossils in Britain and uncovered that many specimens previously misidentified actually belong to coelacanthiform fishes.
These bones, sitting in museum drawers for more than 150 years, now offer new insights into diversity and ecology just before the end-Triassic mass extinction.
Ossifications of a typical mawsoniid coelacanth skull with the addition of the symplectic and interhyal. Neurocranium and palate shaded blue to highlight they are beneath the dermal and exterior bones. Modified from Carvalho (2002).
Advances in identification have helped unearth more coelacanths
The study identifies numerous elements, including skull bones and fin supports, that match the anatomy of mawsoniid and latimeriid coelacanths. Among these are distinct cranial bones, opercular plates, and varied fin skeletal pieces. Using comparative anatomy and morphological comparisons, the authors argue that more than one coelacanth taxon was present in end-Triassic seas, indicating a richer fish fauna than previously recognized.
One key revelation is that past misclassifications,fossils labeled as reptilian or “enigmatic” marine creatures, were in fact misread coelacanth parts. The authors provide morphological and metric descriptions for each bone type, clarifying features such as ornamentation, tubercles, articulation surfaces, and scale thickness. Some bones show multiple morphotypes, suggesting size variation and possibly different species or life stages were present.
By mapping these finds onto coelacanth phylogeny, the researchers place the fossils largely within Mawsoniidae, though some bones may belong to other coelacanth lineages. The presence of multiple morphotypes supports that coelacanth diversity in Europe before the Jurassic was underappreciated. They also suggest these fishes inhabited shallow marine or nearshore settings, consistent with other mawsoniid habitats elsewhere.
Mawsoniid coelacanth dentaries. A, B, BRSMG lot acc. no. 451991 Cf16006, morphotype 1, partial left dentary lateral, A, and medial, B, views; C–J, NMW 2001.42G.985, morphotype 2, right dentary exposed in lateral view, C, and 3D reconstruction from CT data in ventrolateral, D, lateral, E, dorsolateral, F, dorsal, G, dorsomedial, H, medial, I, and ventral, J views. Arrows indicate the direction of the anterior. Abbreviations: ant.m.f, anterior part of mandibular fossa; ant.pr, anterior process; d.pr, dorsal process; tub, tubercles; v.pr, ventral process. Scale bars represent 10 mm.
This discovery helps us understand Coelacanths, but will be a useful lesson for all fossils
Coelacanths survived successive environmental stresses, and understanding their diversity immediately before a major extinction helps us trace how lineages persisted or collapsed.
“Coelacanth remains are well known from Paleozoic and Cretaceous rocks in Britain but poorly known from the Late Triassic”, the researchers wrote. “Coelacanth diversity peaked in the Lower–Mid Triassic, so it is surprising just how poorly examples from the British Rhaetian have been reported”
Significantly, the authors warn that fossil collections worldwide may harbor similar hidden diversity, masked by misidentifications. This paper shows that reexamining historic specimens with updated comparative databases can rewrite chapters in vertebrate paleontology.
Mawsoniid coelacanth bones from the postcranial skeleton. A, BRSMG Cg3102, neural spine exposed in lateral view; B, NMW2020.14G.7, right clavicle from a large mawsoniid exposed in lateral view; C. FC-DPV 2341/2977, right clavicle of Mawsonia gigas in lateral view, for comparison. Abbreviations: ant.pr, anterior process; n.s, neural spine. Scale bars equal 10 mm in A, and 20 mm in B and C.