A hovering shark
Modern sharks occupy marine ecosystems around the world, but display little morphological diversity, as they are mostly streamlined predators. Vullo et al. describe a new species of shark from the late Cretaceous that shows that the lack of current variation was not due to limited morphological “exploration” in the past. Specific, Aquilolamna milarcae exhibits many characteristics similar to modern manta rays, especially long, thin fins and a mouth apparently adapted for filter feeding, indicating that it is plankton. This finding both indicates that elasmobranches have evolutionarily experimented with other forms and that the plankton “swears” emerged in this group at least 30 million years earlier than previously recognized.
Science, this issue p. 1253
Abstract
The ecomorphological variety of extinct elasmobranches is incompletely known. Here we describe Aquilolamna milarcae, a bizarre likely planktivorous shark from early late-critical open marine deposits in Mexico. Aquilolamna, provisionally assigned to Lamniformes, is characterized by hypertrophy, slender pectoral fins. This previously unknown body plan represents an unexpected evolutionary experiment with underwater flight under sharks, more than 30 million years before the emergence of manta and devil rays (Mobulidae), and shows that winged pectoral fins developed independently in two closely related clade filter-feeding elasmobranches. This newly described group of highly specialized long-winged sharks (Aquilolamnidae) exhibits an aquilopelagic ecomorphotype and may in the late Mesozoic seas occupy the ecological niche filled by mobules and other batoids after the Cretaceous-Paleogene boundary.