Abstract
Many modern groups of marine fishes first appear in the fossil record during the early Palaeogene (66–40 Ma), including iconic predatory lineages of spiny-rayed fishes that appear to have originated in response to ecological roles left empty after the Cretaceous/Palaeogene extinction. The hypothesis of extinction-mediated ecological release likewise predicts that other fish groups have adopted novel predatory ecologies. Here, we report remarkable trophic innovation in early Palaeogene clupeiforms (herrings and allies), a group whose modern representatives are generally small-bodied planktivores. Two forms, the early Eocene (Ypresian) †Clupeopsis from Belgium and a new genus from the middle Eocene (Lutetian) of Pakistan, bear conspicuous features indicative of predatory ecology, including large size, long gapes and caniniform dentition. Most remarkable is the presence of a single, massive vomerine fang offset from the midline in both. Numerous features of the neurocranium, suspensorium and branchial skeleton place these taxa on the engraulid (anchovy) stem as the earliest known representatives of the clade. The identification of large-bodied, piscivorous anchovies contributes to an emerging picture of a phylogenetically diverse guild of predatory ray-finned fishes in early Palaeogene marine settings, which include completely extinct lineages alongside members of modern marine groups and taxa that are today restricted to freshwater or deep-sea environments.
Highlights
Body fossils [1,2,3], otoliths [4], ichthyoliths [5,6] and molecular clocks [7,8] point to the early Palaeogene as a time of remarkable diversification and innovation among marine fishes
We report a new early–middle Eocene clade of large-bodied clupeiform fishes, the anatomy of which has been revealed by micro-computed tomography
This group, represented by the previously described †Clupeopsis straeleni from the Ypresian of Belgium [16] and a new genus and species from the Lutetian of Pakistan, is characterized by remarkable dental specializations: a single row of enlarged dentary teeth combined with a single massive vomerine fang that extends to the ventral margin of the mandibular symphysis
Summary
Body fossils [1,2,3], otoliths [4], ichthyoliths [5,6] and molecular clocks [7,8] point to the early Palaeogene as a time of remarkable diversification and innovation among marine fishes. We report a new early–middle Eocene clade of large-bodied clupeiform (herrings and anchovies) fishes, the anatomy of which has been revealed by micro-computed tomography (μCT) This group, represented by the previously described †Clupeopsis straeleni from the Ypresian of Belgium [16] and a new genus and species from the Lutetian of Pakistan, is characterized by remarkable dental specializations: a single row of enlarged dentary teeth combined with a single massive vomerine fang that extends to the ventral margin of the mandibular symphysis. They point to previously unappreciated trophic innovation in an early Palaeogene marine setting that has not persisted to the modern day
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