Published online by Cambridge University Press: 08 February 2016
Antarctic Hoploparia exhibit morphologic changes upsection in a stratigraphic record considered to be long (approximately 15 m.y.) and free of major hiatuses. Five characters exhibit change upsection, and the overall morphologies of the geologically oldest and youngest lobsters are different. The observed patterns could be the result of either phyletic evolution or gradual invasion of one or more species into the range of the original species. The most parsimonious interpretation of the data argues against the invasion hypothesis but supports the phyletic evolution hypothesis.