Onychophora: Velvet Worms. This is the only phylum containing exclusively terrestrial members, although their ancestors can be traced back to the Cambrian shallow oceans. Onychophorans are ambush predators, moving with slow smooth steps to creep up on their prey. They have unique mucus glands on either side of their face which can spray jets of sticky slime, which effectively immobilizes their prey. Onychophorans have relatively complex brains, and some even live in social "packs" that live and hunt together. Many species in this phylum are ecologically vulnerable, threatened, or endangered.
Platyhelminthes: Flatworms. This phylum includes both colorful free-living members and more modest parasitic members. Free-living worms can be found in marine, freshwater, and even terrestrial environments. All flatworms are, of course, dorsoventrally flattened so their whole bodies can access oxygen from the outside, as they have no specialized circulatory system. Some flatworms are of interest to research in tissue regeneration, as they have the remarkable ability to completely regenerate a new body from a cut piece. Many classes within Platyhelminthes are exclusively parasitic, including flukes, tapeworms, schistosomes, and others. Most flatworms are hermaphroditic, and some larger marine species practice a ritual known as "penis fencing" to determine which worm's eggs will be fertilized.
"Lobopods", unarmored relatives of arthropods, have a long and rich history. While early forms like Hallucigenia remain unclear as to their affinities, another lineage had already split from the first arthropods. Velvet worms still thrive today, having left the seas for rainforests and humid crevices.
Instead of the arthropods' articulated exoskeletons, velvet worms kept a softer, unarticulated cuticle, with tiny round "papillae" covered in bristles and scales providing their velvet-like appearance. They still moult their cuticle regularily, but do not gain new legs doing so - the babies already look like miniature adults!
Adapted to many terrains thanks to their flexible body and clawed legs, velvet worms are true ambush predators. They come with a special weapon: a glue-like slime, immobilizing prey and repelling predators, shot from appendages on each side of their mouth.
Velvet worms are also intelligent, social creatures. At least one species, Euperipatoides rowelli, is known for hunting together, living in groups of up to 15 individuals with complex interactions establishing their social hierarchy. Individuals within a group are often closely related, with most species giving live birth and taking care of their young!
These adorable little creatures are distant cousins of arthropods, but don't have an exoskeleton like them! Instead, their skin has a more velvet feeling, hence their name! They are believed to have existed for more than 500 million years, and...
Yes, they can shoot glue at you if they're angry (or hungry)! They're formidable predators, but also social, living and hunting in groups! Most species are viviparous, with the mothers taking care of their youngs. And they're so colorful and adorable!