Lissamphibia is the clade that includes all modern amphibians: frogs, salamanders, and caecilians. Their origins are a major topic in vertebrate paleontology, linking them to ancient amphibian lineages from the Paleozoic and early Mesozoic eras.
- Lissamphibia includes all living amphibians and their closest fossil relatives, defined by shared derived traits such as pedicellate teeth and unique ear structures.
- They are believed to have diverged from other tetrapods in the late Paleozoic or early Mesozoic, approximately 250 million years ago.
- Fossil evidence traces their roots to groups like temnospondyls or possibly lepospondyls, ancient amphibians that exhibited some modern features.
Lissamphibia includes frogs, salamanders, and caecilians.
Their origins trace back to the Late Paleozoic to Early Mesozoic.
Defining Characteristics of Lissamphibia
Modern amphibians possess several unique traits that distinguish them from other vertebrates, both living and extinct.
- Pedicellate teeth: Teeth with a crown and base separated by a layer of connective tissue, unique to Lissamphibia.
- Bimodal life cycle: Most have aquatic larvae and terrestrial adults.
- Permeable skin: Facilitates cutaneous respiration and requires moist environments.
- Unique ear structure: Adapted for detecting airborne and substrate-borne sounds.
Pedicellate teeth, permeable skin, and a bimodal life cycle are unique to Lissamphibia.
Lissamphibians have pedicellate teeth, with a crown and base separated by connective tissue.
Fossil Evidence and Proposed Ancestors
Fossil discoveries have identified potential ancestral groups for Lissamphibia, especially among early tetrapods.
- Temnospondyls: Diverse early amphibians with some features resembling modern amphibians (e.g., pedicellate-like teeth, vertebral structures). Most paleontologists favor temnospondyls as close relatives.
- Lepospondyls: Another group of Paleozoic amphibians with simplified vertebrae; some hypothesize they gave rise to caecilians.
- Early Lissamphibian fossils: Tiny jaws and vertebrae from the Permian and Triassic show traits of modern amphibians, such as pedicellate teeth.
Temnospondyls are the fossil group most commonly linked to Lissamphibia.
Temnospondyls and Lepospondyls are proposed ancestors of Lissamphibia.
Timeline of Lissamphibian Evolution
| Period | Event |
|---|---|
| Late Devonian (~370 Ma) | Earliest tetrapods emerge |
| Carboniferous (~350-300 Ma) | Diversification of amphibian-like tetrapods |
| Permian (~299-252 Ma) | First possible lissamphibian fossils (jaws, vertebrae) |
| Triassic (252-201 Ma) | Major radiation of early Lissamphibia; origin of modern groups |
| Jurassic to Cretaceous | Diversification of crown-group amphibians |
| Cenozoic (66 Ma-present) | Modern amphibians flourish |
The earliest possible lissamphibian fossils appeared in the Permian.
Modern amphibian groups began to diversify during the Triassic.
Conclusion
The Lissamphibia are a remarkable group of vertebrates whose origins trace back to ancient amphibians of the late Paleozoic and early Mesozoic eras. Their distinctive features and fossil record provide critical insights into vertebrate evolution and the transition from aquatic to terrestrial life.
- Lissamphibia includes all modern amphibians, characterized by unique features like pedicellate teeth.
- Fossil evidence links their origins to ancient amphibians such as temnospondyls and lepospondyls.
- Their evolutionary history spans from the late Paleozoic to the present, illustrating major transitions in vertebrate life.
Frogs, salamanders, and caecilians.
Late Paleozoic to Early Mesozoic.
Temnospondyls and Lepospondyls.