The origin and early evolution of arthropods

Area of Science:

• Paleontology
• Evolutionary Biology
• Zoology

Background:

• Arthropods represent a pivotal event in life's history, being among the first terrestrial and aerial animals.
• Their diversification has profoundly shaped global ecosystems and ecological networks.
• Recent paleontological findings are revising our understanding of their early evolution.

Purpose of the Study:

• To elucidate the precocious appearance of extant arthropod lineages during the Cambrian explosion.
• To investigate the role of planktonic life and hard integuments in early arthropod diversification.
• To re-evaluate the stepwise acquisition of arthropod characters and the phylogenetic placement of Cambrian taxa.

Main Methods:

• Analysis of exceptionally well-preserved Palaeozoic arthropod fossils.
• Application of new approaches and techniques to re-examine existing and newly discovered fossils.
• Phylogenetic analysis incorporating paleontological data to resolve relationships, including the 'deep split' hypothesis.

Main Results:

• Extant arthropod lineages (Mandibulata and Chelicerata) are traceable to the Cambrian period.
• Early arthropods possessed a homologous frontalmost appendage (cheira), evolving into antennules and chelicerae.
• Evidence suggests both predation and suspension-feeding were key drivers of early panarthropod evolution.
• The 'deep split' model supports Artiopoda as sister taxa to chelicerates, reinforcing Arachnomorpha.

Conclusions:

• The Cambrian explosion was more complex, with early euarthropods belonging to extant lineages.
• Cephalic appendage evolution, brain, and labrum remain areas of active research.
• Integrating fossil data from various Palaeozoic Lagerstätten is crucial for a comprehensive picture of arthropod evolution.