Abstract Nearly half of all living vertebrate diversity can be traced back to a single lineage of lobe‐finned fishes (piscine sarcopterygians) that radiated during the Palaeozoic Era. In recent years, the phylogenetic framework of tetrapodomorph fishes has largely stabilized, with the exception of the ‘Osteolepiformes’, the interrelationships of which are still under debate. To resolve these uncertainties, expanded taxonomic sampling and new morphological data are essential to refine our understanding of their evolutionary history. Emerging tomography imaging techniques are providing much of this new anatomical information, including that pertaining to cranial endocasts. Endocasts can serve as proxies for gross brain morphology, and thus have the added benefit of shedding light on palaeoneurological evolution in long‐extinct lineages. Here, using a combination of synchrotron, neutron and micro‐computed tomography, we generate high‐resolution 3D virtual models of ethmosphenoids and their associated cranial endocast and sensory (lateral) line canal systems in 13 stem tetrapods. Using principal components analysis for incomplete data we identify distinct patterns of morphospace occupation among the different families. While the ‘Tristichopteridae’ usually occupy a wholly distinct region, the ‘Osteolepididae’ and Megalichthyidae exhibit partial overlap, but with ‘Osteolepididae’ always showing a broader range of variation. Our findings demonstrate that ethmosphenoids and their endocasts retain morphological features of shared phylogenetic affinity that can aid in resolving phylogenetic placement of fragmentary or enigmatic taxa. Furthermore, palaeoneurobiological evidence from these ‘Osteolepiformes’ suggests that these fishes retained a more conservative sensory umwelt prior to the rapid emergence of enhanced visual acuity in the earliest tetrapods.
Clement et al. (Fri,) studied this question.