The rapid evolution of lungfish durophagy

Abstract

Innovations relating to the consumption of hard prey are implicated in ecological shifts in marine ecosystems as early as the mid-Paleozoic. Lungfishes represent the first and longest-ranging lineage of durophagous vertebrates, but how and when the various feeding specializations of this group arose remain unclear. Two exceptionally preserved fossils of the Early Devonian lobe-finned fish Youngolepis reveal the origin of the specialized lungfish feeding mechanism. Youngolepis has a radically restructured palate, reorienting jaw muscles for optimal force transition, coupled with radiating entopterygoid tooth rows like those of lungfish toothplates. This triturating surface occurs in conjunction with marginal dentition and blunt coronoid fangs, suggesting a role in crushing rather than piercing prey. Bayesian tip-dating analyses incorporating these morphological data indicate that the complete suite of lungfish feeding specializations may have arisen in as little as 7 million years, representing one of the most striking episodes of innovation during the initial evolutionary radiations of bony fishes.

Morphometric analysis of lungfish endocasts elucidates early dipnoan palaeoneurological evolution

“…Lungfish first appear in the fossil record in the Early Devonian as robust marine animals, many with hyper-mineralised tooth plates, heavily-ossified dermal skulls and neurocrania ( Cui et al, 2022 ). However, from the Late Devonian-Carboniferous onwards, many undergo a decline in the degree of ossification as their skeleton becomes more cartilaginous.…”

The biogeography of extant lungfishes traces the breakup of Gondwana

“…We used the FBD model with rho set to 0.24, which is the proportion of living species in our dataset. We set the origin age prior to 450 Ma, which represents an estimate of the maximum age of the lungfish total clade (Cui et al, 2022; Meyer et al, 2021), with a minimum of 419.2 Ma following a recent phylogeny (Cui et al, 2022), which invariably provides a minimum divergence time of lowermost Lochkovian age for the lungfish total clade, a maximum of 440 Ma, which is the age of the coelacanth‐dipnotetrapodomorph split based on genomic data (Meyer et al, 2021), and a mean of 425 Ma, which is the rounded age of divergence based on genomic data (see figures in Meyer et al, 2021). The diversification rate prior was set to 0.01, which is the number of living species in our dataset divided by the mean origin prior age.…”

“…Lungfishes (Dipnoi) are an iconic group of lobe‐finned fishes that comprise the sister lineage of tetrapods, which includes all terrestrial vertebrates (Amemiya et al, 2013; Meyer et al, 2021; Rosen et al, 1981; Takezaki & Nishihara, 2017). Despite their present‐day low species richness, lungfishes showed a considerable degree of morphological disparity in the past, with the clade experiencing a burst of speciation and phenotypic innovation following their appearance in the Silurian‐Devonian (Cui et al, 2022; Schaeffer, 1952; Stanley, 1975). The phylogenetic relationships of these early fossil species have been extensively investigated (Cui et al, 2022; Kemp et al, 2017; Pardo et al, 2014).…”

“…Despite their present‐day low species richness, lungfishes showed a considerable degree of morphological disparity in the past, with the clade experiencing a burst of speciation and phenotypic innovation following their appearance in the Silurian‐Devonian (Cui et al, 2022; Schaeffer, 1952; Stanley, 1975). The phylogenetic relationships of these early fossil species have been extensively investigated (Cui et al, 2022; Kemp et al, 2017; Pardo et al, 2014). In contrast, the timing of diversification among the three extant lungfish lineages—the Australian Neoceratodus , the African Protopterus and the South American Lepidosiren —and their relationships to extinct clades remain poorly understood (Capobianco & Friedman, 2019).…”

A single-cell atlas of West African lungfish respiratory system reveals evolutionary adaptations to terrestrialization

“…Lungfishes, a group of lobe-finned fishes, emerged around 400 million years ago and are the closest living relatives of tetrapods 9 . While it is appreciated that extant lungfish species have diverged in various ways since their Devonian origin 9 , 10 they nevertheless, as their name indicates, possess bimodal respiration with gills for water breathing and lungs for air breathing. Understanding the respiratory characteristics of basal fish species with bimodal respiration promises to reveal insights into fundamental adaptations associated with early tetrapod terrestrialization and fish evolution 1 – 5 .…”