A Late Devonian coelacanth reconfigures actinistian phylogeny, disparity, and evolutionary dynamics

Area of Science:

• Paleontology
• Evolutionary Biology
• Vertebrate Zoology

Background:

• Coelacanths (Actinistia) are ancient fish, often called 'living fossils'.
• They belong to a morphologically conservative group of vertebrates.
• The living coelacanth genus Latimeria is iconic in evolutionary studies.

Purpose of the Study:

• To describe a new 3-D preserved coelacanth fossil from the Late Devonian Gogo Formation.
• To analyze the phylogeny, evolutionary rates, and morphological disparity of all coelacanths.
• To understand the evolutionary trajectory and key transitional stages in coelacanth history.

Main Methods:

• Description of a new fossil coelacanth specimen.
• Comprehensive phylogenetic analysis of coelacanths.
• Assessment of morphological disparity and evolutionary rates across geological time.

Main Results:

• A new coelacanth fossil from the Late Devonian Gogo Formation is described.
• A significant shift in morphological disparity occurred between Devonian and post-Devonian coelacanths.
• Major morphological innovations largely ceased after the mid-Cretaceous, while other traits continued evolving.

Conclusions:

• The new fossil represents a critical transitional stage in coelacanth evolution.
• Tectonic activity is the most likely driver for variations in coelacanth evolutionary rates.
• Coelacanth evolution shows distinct phases of innovation and gradual change.