# Westlothiana's Early Tetrapod Ancestry Revealed

> New fossil evidence reshapes understanding of early tetrapod limb evolution.
- Title: Westlothiana's Early Tetrapod Ancestry Revealed · Nature
- Summary: New fossil evidence reshapes understanding of early tetrapod limb evolution. Westlothiana lizziae, an Early Carboniferous stem amniote, shows mosaic…
- Keywords: westlothiana, lizziae, early carboniferous, stem amniote, tetrapod limb, amphibious context, carboniferous, science, Westlothiana's, Early, Tetrapod, Ancestry
- Source: Nature — https://nature.com/articles/s41586-026-11090-6
- Published: 2026-09-30T00:00:00+00:00
- Read time: 1 min
- Topics: westlothiana, lizziae, early carboniferous, stem amniote, tetrapod limb, amphibious context, carboniferous, science
## Westlothiana lizziae discovery
Scientists identified Westlothiana lizziae as the earliest terrestrially adapted stem amniote from the Early Carboniferous period.
## Unexpected anatomical features
The fossil shows plesiomorphies in the skull roof, palate, braincase, and mandible alongside aquatic adaptations like an ossified internal gill skeleton.
## Phylogenetic analysis
Westlothiana lizziae is classified as a stem tetrapod in phylogenetic analyses, demonstrating mosaic evolution of terrestrial adaptations.
## Terrestrial adaptation timeline
Amniote-like pedal formula, loss of fin-like forelimb function, and claw-like terminal phalanges evolved in amphibious contexts before the tetrapod crown group.
## Evolutionary significance
These findings reveal substantial gaps in anatomical knowledge for small-bodied taxa, obstructing understanding of early tetrapod evolution.
## Key takeaway

Westlothiana lizziae, an Early Carboniferous stem amniote, shows mosaic terrestrial adaptations evolving in amphibious contexts before the tetrapod crown group emerged.