Pterosaur melanosomes support signalling functions for early feathers

Area of Science:

• Paleontology
• Evolutionary Biology
• Mesozoic Era Soft Tissue Research

Background:

• Well-preserved soft tissues in Mesozoic fossils offer insights into feather evolution.
• Previous evidence suggested branched feathers in pterosaurs, hinting at early feather origins, but their homology remains debated.
• Homogeneous melanosome shapes in reported pterosaur feathers suggested limited color variation and primary thermoregulatory function.

Purpose of the Study:

• To investigate the diversity of melanosome geometries in the skin and feathers of a tapejarid pterosaur.
• To determine if pterosaur feathers exhibited varied melanosome populations, similar to theropod dinosaurs.
• To explore the evolutionary origins of feather color manipulation and its potential functions in visual communication.

Main Methods:

• Analysis of soft tissues from a tapejarid pterosaur fossil from the Early Cretaceous, Brazil.
• Microscopic examination of melanosome geometries within different feather types (simple and branched) and skin.
• Comparison of melanosome diversity with known patterns in theropod dinosaurs and birds.

Main Results:

• Discovery of diverse melanosome geometries in the skin, simple feathers, and branched feathers of the tapejarid pterosaur.
• Identification of distinct melanosome populations within different feather types and the skin.
• This melanosome diversity pattern is comparable to that found in theropod dinosaurs, including birds.

Conclusions:

• Tissue-specific melanosome geometries in pterosaurs demonstrate that the manipulation of feather color for functions like visual communication has ancient evolutionary roots.
• The findings suggest that genetic regulation of melanosome chemistry and shape was active early in feather evolution.
• This challenges the notion that early feathers were solely for thermoregulation, highlighting their potential role in signaling.