Velvet worm development links myriapods with chelicerates

Area of Science:

• * Zoology
• * Evolutionary Biology
• * Arthropod Phylogenetics

Background:

• * The evolutionary relationships of the four major arthropod groups (Chelicerata, Myriapoda, Crustacea, Hexapoda) are debated.
• * Key hypotheses for myriapod placement include the Paradoxopoda (closest to chelicerates) and Mandibulata (closest to crustaceans/hexapods).
• * Previous molecular and morphological studies have provided inconclusive or conflicting evidence.

Purpose of the Study:

• * To investigate the phylogenetic position of myriapods within arthropods.
• * To provide morphological and embryological evidence for arthropod phylogeny.
• * To test the Paradoxopoda and Mandibulata hypotheses.

Main Methods:

• * Comparative analysis of embryonic characters.
• * Phylogenetic reconstruction using an outgroup comparison with Onychophora (velvet worms).
• * Evaluation of potential synapomorphies (shared derived traits).

Main Results:

• * Several embryonic characters identified as synapomorphies unite chelicerates and myriapods.
• * Outgroup comparison with Onychophora provided crucial data for phylogenetic interpretation.
• * Findings support the monophyly of the Paradoxopoda clade.

Conclusions:

• * The study provides the first morphological/embryological support for the Paradoxopoda hypothesis.
• * The findings suggest that the mandible, a key feature of Mandibulata, may have evolved independently twice in arthropods.
• * Revises our understanding of early arthropod evolution and character evolution.