Unrelated biota!

-Meganeura

They spawn in forests, jungles, savannas and plains. They're aggressive.

It drops meganeura bits which can be crafted into meganeura kebab and can be cooked using a campfire.

-Pulmonoscorpius

They spawn in savanas and jungles. They attack back if you hit them.

It drops pulmonscorpius stinger and claws. The claw can be cooked using a campfire.

The stinger is used for crafting a stinger spear.

-Dimetrodon

They spawn in savanas and plains. They attack back if you hit them.

It drops dimetrodon meat and can be cooked using a campfire.

-Therizinosaurus

They spawn in taigas. They attack back if you hit them.

the walking animation is a little wack for this one.

It drops a therizinosaurus claw which can be crafted into a knife

-Dunkleosteus

They spawn in almost any ocean. They are aggressive.

It drops a dunkleosteus tooth which can be crafted into an axe

-Trilobite 

It spawns on beaches

It doesn't drop anything.

ANOMALOCARIS!!!!!!

A very cool guy that spawn in warm oceans and regular oceans. They are aggressive.

They're my favourite!

they drop an appendage which can be crafted into sword.

-Inotrancevia

 They spawn in savannas. They will try to kill you.

They drop their teeth. the teeth and glyptodon shell fragments to make a chestplate.

-Scutosaurus

They spawn in savannas and plains. Thay don't fight back.

They drop scutosaurus meat. the meat can be cooked.

 -Glyptodon

They spawn in any taigas. They attack back.

They drop glyptodon shell fragments, which can be made into a chestplate with the inostrancevia teeth.

-Nautilus

They spawn in oceans and they're passive. 

They drop nautilus shells.

-Anglerfish

They spawn in deep oceans. They attack back if you hit them.

They drop bones and bioluminescent goop.

The goop can be crafted into bioluminescent torches.

The torches float.

-Lanternfish 

It's a fish that spawns in any deep ocean

It drops bioluminescent goop, bone, and raw lanternfish.

Raw lanternfish can be cooked.

-Gila monster

It's just a lizard that spawns in savanas

it drops nothing.

-Great grey owl

They spawn in old growth taigas.

It drops feathers.

-Giant beetle

Its not that very big. They like to spawn wherever. They attack.

They also drop beetle meat. Can be cooked with a campfire.

-Velvet ant (female)

They spawn in badlands deserts and savanas. Very dangerous, attacks gives you wither. They are aggressive

They drop velvet ant chitin, velvet ant head, velvet ant stinger and some gold and iron nuggets.

-Velvet ant (male)

less dangerous (no wither) and flys.

They drop the same besides the stinger. They don't have one.

 -Velvet ant items

Chtin, head, stinger, stinger spear and ant armor.

Here's some recipes

-stinger spear

Does poison and wither but only has 5 durability.

-Velvet ant armor

Is very strong. Probably too strong.

Woah!

-Trap-jaw ant

They spawn in forset biomes. They are neutral.

Ant.

They drop ant meat and mandible. meat can be cooked with campfire.

Ant mandible can be made into a club.

-Yellowjacket

It's now here. big and angry.

It's really super big. No items though...

-boatman beetle

Small guy that just swims.

It doesn't drop items.

-Arthropod soup

is a soup.

-Image of garbage made up mobs (don't spawn)

no, you won't get the names.

the animations are awful.

-Old versions of mobs (don't spawn)

Here's an image.

old anomalocaris, old gila monster and old trilobite.