Primitive Early Eocene bat from Wyoming and the evolution of flight and echolocation

Area of Science:

• Paleontology
• Evolutionary Biology
• Mammalogy

Background:

• Bats (Chiroptera) are a highly diverse mammalian group, comprising one-fifth of extant species.
• While bat monophyly is supported, their early evolution and the origins of flight and echolocation remain poorly understood.
• The fossil record offers limited insight into these early evolutionary transitions.

Observation:

• A new bat fossil from the Early Eocene Green River Formation, Wyoming, exhibits primitive features.
• This fossil displays forelimb anatomy consistent with powered flight but ear morphology suggesting a lack of echolocation.
• Wing shape indicates a primitive undulating gliding-fluttering flight style, and a long calcar suggests an early evolution of the tail membrane.

Findings:

• The new fossil bat demonstrates incremental evolution of key flight and sensory adaptations.
• It supports the 'flight first' hypothesis, suggesting powered flight preceded echolocation in bat evolution.
• Primitive locomotion may have involved quadrupedal movement and under-branch hanging, with claws on all digits.

Implications:

• This discovery provides crucial fossil evidence for understanding the evolutionary pathways of bats.
• It refines hypotheses regarding the sequence of major chiropteran adaptations.
• The findings contribute to our understanding of early mammalian diversification and adaptation to aerial niches.