Overview

• Researchers identified the Late Cretaceous Acronichthys maccagnoi from Alberta as the oldest known North American otophysan fossil.
• The specimen preserves a well-developed Weberian apparatus that was reconstructed in 3D from micro-CT scans.
• Computer models suggest peak hearing sensitivity between 500 and 1,000 Hz with slightly lower output power than zebrafish yet retaining high-frequency capability.
• Phylogenetic dating places the shift from marine ancestors to freshwater otophysans in the Late Jurassic at about 154 million years ago.
• The study infers at least two early freshwater incursions that seeded two major lineages and likely accelerated diversification into today’s hyper-diverse groups, including catfish, tetras, carps and minnows.