From Nature · · 1m
Westlothiana's Early Tetrapod Ancestry Revealed
New fossil evidence reshapes understanding of early tetrapod limb evolution.
In brief
New fossil evidence reshapes understanding of early tetrapod limb evolution. Westlothiana lizziae, an Early Carboniferous stem amniote, shows mosaic terrestrial adaptations evolving in amphibious contexts before the tetrapod crown group emerged. Originally reported by Nature.
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.
In short
Westlothiana lizziae, an Early Carboniferous stem amniote, shows mosaic terrestrial adaptations evolving in amphibious contexts before the tetrapod crown group emerged.
