TIL About 97% of all animal species are invertebrates. They vary in size from 50 μm (0.050mm) rotifers to the 9–10 m colossal squid. by whatilearned October 14, 2021, 5:07 pm Read more: https://en.wikipedia.org/wiki/Invertebrate What do you think? 12 Points Upvote Downvote 0050mmAnimalcolossalinvertebratesrotiferssizespeciessquidTILToday I learnedvaryμm See more Previous article What do whiskey drinkers and catholic priests have in common? Next article How I built a little tool that keeps millions of people safe online One Comment Leave a Reply > The earliest animal fossils appear to be those of invertebrates. 665-million-year-old fossils in the Trezona Formation at Trezona Bore, West Central Flinders, South Australia have been interpreted as being early sponges. Some paleontologists suggest that animals appeared much earlier, possibly as early as 1 billion years ago. Trace fossils such as tracks and burrows found in the Tonian era indicate the presence of triploblastic worms, like metazoans, roughly as large (about 5 mm wide) and complex as earthworms Log in to Reply Leave a Reply Cancel replyYou must be logged in to post a comment.