Which of the following is a pair of chordate synapomorphies?

• A. Exoskeleton and jointed appendages
• B. Notochord and dorsal hollow nerve cord
• C. Radial symmetry and gastrovascular cavity
• D. Mantle and radula

Answer: (B)

Verified step by step guidance

1. Understand the term 'synapomorphy': A synapomorphy is a shared, derived trait that is unique to a particular group of organisms and inherited from a common ancestor.
2. Identify the defining characteristics of chordates: Chordates are a phylum of animals that share specific synapomorphies, including the presence of a notochord and a dorsal hollow nerve cord during some stage of their development.
3. Analyze the options provided: Evaluate each pair of traits to determine if they are synapomorphies specific to chordates.
4. Option 1: 'Exoskeleton and jointed appendages' are traits associated with arthropods, not chordates, so this pair is incorrect.
5. Option 2: 'Notochord and dorsal hollow nerve cord' are defining synapomorphies of chordates, making this the correct answer. The other options ('Radial symmetry and gastrovascular cavity' and 'Mantle and radula') are traits associated with other groups like cnidarians and mollusks, respectively.