Tuesday, September 8, 2020

Deuterostomes, Protostomes, Acorn Worms -- September 8, 2020

From Evolution: The Whole Story, Thames & Hudson, Steve Parker, p.111, some data points:

  • acorn worms go back all the way to the middle Cambrian, 505 million years ago
  • as a hemichordate, the acorn worm is a Deuterostome
  • broadly speaking:
  • protostomes: invertebrates; all living invertebrates belong to Protostomia
  • deuterostomes: vertebrates; some invertebrates (echinoderms: starfish and sea urchins) belong to Deuterostomia; deuterstomes are all chordates + the invertebrate echinoderms; also include lancelets and tunicates
  • among extant species, there are a gazillion protostomes compare the paltry number of deuterostomes
  • so acorn worms, extending back to the middle Cambrian, are deuterostomes, perhaps starting the long lineage all the way to humans

Internet links:

No comments:

Post a Comment