BIO 385 Invertebrate Zoology
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Invertebrate Diversity
Arthropod Relatives

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Phylum Onychophora Velvet Worms


  • Caterpillar-like, 5 mm - 15 cm long
  • Numerous paired, unjointed lobopods (legs)
  • Head appendages: antennae, jaws, oral papillae
  • Thin, chitinous cuticle is molted
  • Covered in fine tubercles (giving velvet-like appearance)
  • Produce sticky slime to capture prey
  • Terrestrial in moist tropical forests
Velvet Worm
Velvet Worm, Peripatus sp., preserved specimen
Possible Onychophorans (lobopods) from the Cambrian Period, from left to right: Aysheaia, Diania (aka the walking cactus), & Hallucigenia (not to scale)

Phylum Tardigrada Water Bears


  • Small (< 0.5mm), stubby-bodied
  • 8 short, clawed legs
  • Have a slow, lumbering gait
  • Chitinous cuticle that is molted
  • Oral stylets for piercing plants
  • Most in moist film on lichens, mosses, and other small plants
  • Capable of cryptobiosis: suspended animation to withstand drying
Water Bear
Water Bear, probably Hypsibius sp.
Water Bear
Water Bear, probably Hypsibius sp.
Marine Tardigrade
Unidentified marine tardigrade

Phylum/Class Dinocaridida Dinocarids


  • Extinct; Primarily from Cambrian Period
  • Segmented with broad lateral lobes
  • Well-developed eyes (either 2 or 5)
  • Ventral mouth
  • Segmented feeding appendage(s)
  • Anomalocarids included the largest predators of their time
  • Sometimes considered a Class within Phylum Arthropoda
Animalocarids from the Cambrian Period: Anomalocaris (above) and Peytoia (below)
Aegirocassis, a large (2 m), suspension-feeding animalocarid from the Ordovician Period
Opabinia, from Cambrian Period
This page last updated 18 March 2017 by Udo M. Savalli ()
Images and text Udo M. Savalli. All rights reserved.