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2d ago

Study Finds Rodent Thumb Nail Widespread and Key to Food Handling

Researchers say the small nail likely arose early with gnawing teeth to let rodents exploit hard, energy‑rich foods.

Mit flachen Nägeln lassen sich Nüsse besser greifen als mit langen Krallen
Eichhörnchen gehören zu den Nagetieren, die ihr Futter beim Fressen in den Händen halten – und die am Daumen statt einer Kralle einen Daumennagel haben. © Jule Ahlers/ iStock
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Overview

  • Surveying museum specimens from 433 rodent genera, the team found a thumb nail in about 86% of the genera examined.
  • Species that grasp seeds or nuts with their forepaws typically have a flattened nail on the thumb, whereas mouth‑feeders often lack a thumb or its nail.
  • Phylogenetic reconstruction and fossils point to an early origin for the trait, with evidence from Paramys around 55 million years ago and indications it was present by the early Oligocene.
  • Later lineages that dig burrows frequently replaced the thumb nail with a claw or lost the digit, aligning nail presence with above‑ground and arboreal habits rather than subterranean life.
  • The peer‑reviewed study by Missagia and colleagues at Chicago’s Field Museum appears in Science and proposes that this trait helped open new dietary niches that fueled rodent diversification.