An early Pangaean vicariance model for synapsid evolution

Area of Science:

• Paleontology
• Evolutionary Biology
• Paleogeography

Background:

• Vicariance, or geographic isolation, is a primary driver of speciation in vertebrates.
• Demonstrating vicariance in the fossil record across diverse taxa has been challenging.
• The Late Palaeozoic era (350-250 million years ago) offers a unique window into early vertebrate evolution.

Purpose of the Study:

• To reconstruct an early Pangaean palaeogeographic model for the Late Palaeozoic.
• To test the hypothesis that vicariance due to Pangaean separation influenced early amniote evolution.
• To correlate palaeogeographic models with fossil data and biotic events.

Main Methods:

• In-depth review of Late Palaeozoic fossil data.
• Reconstruction of an early Pangaean junction-disjunction palaeogeographic model.
• Comparison of the palaeogeographic model with time-calibrated cladograms of synapsids.
• Correlation with North American marine biostratigraphic units and biochronostratigraphic charts.

Main Results:

• The reconstructed Pangaean model strongly coincides with cladograms of Late Palaeozoic synapsids.
• The emergence of synapsid taxa aligns with the temporal development of the vicariant topology.
• The model explains patterns in North American marine biostratigraphy and supports allopatric speciation in amniotes.
• Correlations suggest the arido-eustasy model explains mid-Permian extinction events and depositional cycles.

Conclusions:

• Vicariance due to Pangaean separation was a significant factor in early amniote evolution.
• Palaeogeographic evolution is intrinsically linked to the evolution of life on Earth.
• Allopatric speciation through vicariance is supported as a prominent mode of amniote evolution.
• The arido-eustasy model provides a framework for understanding mid-Permian biotic changes.