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| Aquilolamna milarcae feeding on plankton in the Gulf of Mexico 93 million years ago. This newly described group of Late Cretaceous sharks (Aquilolamnidae) occupied the same ecological niche as Cenozoic devil and manta rays (Mobulidae), indicating that "winged" suspension feeders evolved independently in two distinct lineages of cartilaginous fishes before and after the end-Cretaceous crisis. Vullo, Frey, Ifrim, González González, Stinnesbeck & Stinnesbeck, 2021 Illustration: Oscar Sanisidro |
Abstract
The ecomorphological diversity of extinct elasmobranchs is incompletely known. Here, we describe Aquilolamna milarcae, a bizarre probable planktivorous shark from early Late Cretaceous open marine deposits in Mexico. Aquilolamna, tentatively assigned to Lamniformes, is characterized by hypertrophied, slender pectoral fins. This previously unknown body plan represents an unexpected evolutionary experimentation with underwater flight among sharks, more than 30 million years before the rise of manta and devil rays (Mobulidae), and shows that winglike pectoral fins have evolved independently in two distantly related clades of filter-feeding elasmobranchs. This newly described group of highly specialized long-winged sharks (Aquilolamnidae) displays an aquilopelagic-like ecomorphotype and may have occupied, in late Mesozoic seas, the ecological niche filled by mobulids and other batoids after the Cretaceous–Paleogene boundary.
Romain Vullo, Eberhard Frey, Christina Ifrim, Margarito A. González González, Eva S. Stinnesbeck and Wolfgang Stinnesbeck. 2021. Manta-like Planktivorous Sharks in Late Cretaceous Oceans. Science. 371(6535); 1253-1256. DOI: 10.1126/science.abc1490
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| Artist's view of three eagle sharks (Aquilolamna milarcae) feeding on plankton in the Gulf of Mexico 93 million years ago. This newly described group of Late Cretaceous sharks (Aquilolamnidae) occupied the same ecological niche as Cenozoic devil and manta rays (Mobulidae), indicating that "winged" suspension feeders evolved independently in two distinct lineages of cartilaginous fishes before and after the end-Cretaceous crisis. Illustration: Oscar Sanisidro |
A soaring shark
Modern sharks occupy marine ecosystems across the world but display little morphological diversity, being mostly streamlined predators. Vullo et al. describe a new species of shark from the late Cretaceous that shows that the lack of current variation is not due to limited morphological “exploration” in the past. Specifically, Aquilolamna milarcae displays many features similar to modern manta rays, notably long, slender fins and a mouth seemingly adapted to filter feeding, suggesting that it was planktivorous. This finding indicates both that elasmobranchs evolutionarily experimented with other forms and that the planktivorous “soarers” emerged in this group at least 30 million years earlier than previously recognized.