A soaring shark
Modern sharks occupy marine ecosystems around the world, but exhibit little morphological diversity, being mostly streamlined predators. Vullo et al. describe a new late Cretaceous shark species showing that the lack of current variation is not due to limited morphological “exploration” in the past. Specifically, Aquilolamna milarcae exhibits many features similar to modern manta rays, notably long, slender fins and a mouth apparently modified to filter, suggesting it was planktivore. This finding indicates that cartilaginous fish have experimented with other forms evolutionarily and that the planktivorous “risers” in this group emerged at least 30 million years earlier than previously believed.
Science, this issue p. 1253
Abstract
The ecomorphological diversity of extinct cartilaginous fish is not fully known. Here we describe Aquilolamna milarcae, a bizarre probable planktivorous shark from the early late Cretaceous open marine deposits in Mexico. Aquilolamna, tentatively assigned to Lamniformes, is characterized by hypertrophic, slender pectoral fins. This previously unknown body plan represents an unexpected evolutionary experiment of underwater flight among sharks, more than 30 million years before the emergence of mantas and devil rays (Mobulidae), and shows that wing-like 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) exhibits an aquilopelagic-like ecomorphotype and may have occupied the ecological niche in the late Mesozoic seas filled with mobulides and other batoids beyond the Cretaceous-Paleogene boundary.