Lobe-finned fishes

Definition

Lobe-finned fishes are a group of bony fish characterized by their fleshy, lobed fins, which are joined to the body by a single bone. These fishes, including the coelacanths and lungfishes, represent a significant evolutionary link between fish and the early tetrapods that eventually ventured onto land. Their unique fin structure provides insight into the transition from aquatic to terrestrial life during the Devonian period.

5 Must Know Facts For Your Next Test

1. Lobe-finned fishes evolved during the Devonian period, which lasted from approximately 419 to 359 million years ago, and are considered a precursor to amphibians.
2. They possess lungs in addition to gills, allowing them to survive in oxygen-poor water and even breathe air when necessary.
3. Fossils of lobe-finned fishes provide evidence for the evolution of limb structure, showing how the fins adapted over time into the limbs of terrestrial animals.
4. The discovery of living coelacanths in the 20th century confirmed that some lobe-finned fishes had survived the mass extinction events that wiped out many other species.
5. Lobe-finned fishes are classified under the subclass Sarcopterygii, which is distinct from ray-finned fishes (Actinopterygii) that dominate modern aquatic ecosystems.

Review Questions

• How do lobe-finned fishes illustrate the evolutionary transition from aquatic life to terrestrial life?
  • Lobe-finned fishes demonstrate the evolutionary transition from aquatic life to land-dwelling animals through their unique fin structure, which resembles limbs. The fleshy, lobed fins of these fishes allowed them to explore shallow waters and navigate through vegetation, setting the stage for the development of true limbs seen in tetrapods. Fossil evidence also shows how these fins gradually evolved into limbs capable of supporting weight on land.
• Evaluate the importance of lobe-finned fishes in understanding vertebrate evolution during the Devonian period.
  • Lobe-finned fishes are critical for understanding vertebrate evolution during the Devonian period because they represent a key link between fish and early amphibians. This era saw an explosion of fish diversity, and lobe-finned species contributed significantly to this. Their adaptations, such as lungs for breathing air and limb-like fins for mobility, highlight essential evolutionary changes that paved the way for life on land.
• Synthesize information about lobe-finned fishes and their role in the ecosystem during the Devonian period with their implications for modern biodiversity.
  • Lobe-finned fishes played a pivotal role in Devonian ecosystems as both predators and prey, influencing food webs and nutrient cycling. Their adaptations set a foundation for future terrestrial vertebrates, shaping modern biodiversity by allowing life to adapt to various terrestrial environments. The traits developed by lobe-finned fishes highlight how evolutionary innovations can lead to new ecological niches and ultimately result in the vast array of species we see today.

Related terms

Tetrapods: Tetrapods are vertebrates that have four limbs and are descended from lobe-finned fishes, marking a crucial step in the evolution of land-dwelling animals.

Devonian period: The Devonian period, often referred to as the 'Age of Fishes', is a time in Earth's history where fish diversity flourished and significant evolutionary developments occurred.

Coelacanth: Coelacanths are a group of lobe-finned fishes thought to be extinct until a living specimen was discovered in 1938, showcasing ancient features unchanged for millions of years.