Meeting Abstract
Pufferfishes and relatives (Acanthomorpha: Tetraodontiformes) are a taxonomically diverse, morphologically disparate, and widely-distributed group, including model genomic species (e.g., Fugu rubripes, Tetraodon nigroviridis), but whose phylogenetic relationships remain problematic, particularly with respect to the beak-toothed gymnodonts. The tetraodontiform fossil record is rich and well-studied, but mostly limited to flattened fossils. These fossils present unusual combinations of tetraodontiform characters relative to extant groups (e.g., Eospinus, Eoplectus), indicating their importance to reconstructing tetraodontiform relationships as a whole. However, a new 3D–preserved beaked tetraodontiform from the early Eocene (London Clay Formation, Ypresian; 53 Ma) provides an opportunity to study the skull and postcranial skeleton in detail, via micro-CT tomography. This new tetraodontiform is coeval with the oldest crown-tetraodontiforms, and again presents unprecedented character combinations, including a fused beak comprising individual teeth with prominent dorsal fin spines inserting anteriorly along the skull, supported by dorso-ventrally flattened and expanded proximal radials. This combination supports homoplasy in the evolution of beaked dentition (gymnodont tetraodontiforms) or dorsal-fin anatomy (absent in gymnodonts, but present in various tetraodontiforms, including monocanthids and balistids, possessing a more typical teleost dentition). The unusual morphologies apparent in this new tetraodontfiorm, along with other fossil taxa, are particularly relevant in the context of recent molecular analyses that strongly refute the monophyly of beaked gymnodont puffers, a group recovered by studies of comparative morphology.
