All posts by Jonathan Tweet

Clades & Clades Prehistoric Press Release


The creative team behind Grandmother Fish—Jonathan Tweet and Karen Lewis—also created these games and funded them on Kickstarter.

SEATTLE (May 1) — Clades and Clades Prehistoric are now available to the general public from Atlas Games in St. Paul, Minnesota. Game designer Jonathan Tweet and children’s science illustrator Karen Lewis collaborated to create these games, which demonstrate the concept of a clade. In biology, a clade is a complete branch of the evolutionary tree, such as mammals. Players try to be the first to spot matches among the cards on the table, forming matches according to the animals’ clades and other qualities. Clades features living animals, such as a praying mantis, an eagle, and a human. Clades Prehistoric plays the same way but dinosaurs, sea scorpions, woolly mammoths, and other extinct animals. 

John S. Mead, the Eugene McDermott Master Teacher in Science at St. Mark’s School of Texas, recommends Clades to other educators. “I have seen that it manages to help teach evolutionary concepts in a relaxed and organic way,” he said after using the game in his class of middle schoolers. Mead calls the game a “springboard for students to engage in rapid-fire critical thinking based on solid science.” Players do not need to have a knowledge of evolution to play, says Mead, making the game also “great at helping teach evolutionary ideas to beginners.” 

Tweet and Lewis raised money on Kickstarter to produce Clades and Clades Prehistoric, and copies of the game have been sent to the backers. The backers also raised money to send over 100 copies of the games to nonprofits around the country, such as Camp Quest and the National Center for Science Education. Now that the obligations to the backers have been fulfilled, Atlas Games has released the games to the general public. The games will appear in game stores and bookstores, along with Atlas Games’s broadly popular titles such as Gloom and Once Upon a Time. 

Clades and Clades Prehistoric are follow ups to Grandmother Fish, the first storybook to teach evolution to preschoolers. In 2015, game designer Jonathan Tweet and children’s science illustrator Karen Lewis self-published Grandmother Fish, which sold out and was then picked up by Macmillan for release in 2016. It has since been translated into Italian, and a Chinese translation is in progress. 

For more information, contact 

About Jonathan Tweet. Jonathan Tweet is an award-winning, Seattle-based game designer, having contributed to global brands such as DUNGEONS & DRAGONS, MAGIC: THE GATHERING, and POKEMON. His innovative game designs earned him a place in The Academy of Adventure Gaming Arts and Design Hall of Fame, and he has placed a special emphasis on explaining complicated games in simple terms. Currently he is consulting with the Science Museum of Minnesota on an upcoming program for teaching evolution. 

About Karen Lewis. Karen Lewis is a Seattle-based illustrator for children’s storybooks, history, and science. She strives to make her art accessible, accurate and visually delicious. Favorite clients have included the Point Defiance Zoo and Aquarium, the Seattle Aquarium, Seattle Art Museum, Seattle Public Schools, Seattle Public Utilities, KCTS public television, King County and the National Science Foundation. She’s the resident cartoonist for Cobblestone, an American history magazine for kids. Her children’s book include Will it Blow – Become a Volcano Detective at Mount St. Helens, Amazing Alaska and Arturo and the Navidad Birds.

About Atlas Games. Atlas Games is a publisher of award-winning card games, board games, and roleplaying game books. Its best selling card games include Gloom and Once Upon a Time. Since its founding in 1990, Atlas has published games that have changed the way gamers think about gaming. (web:, e-mail:

Chiroptera: Gliding, Flying, and Echolocating

Early echolocating bat, clawed bat, hypothetical protobat

The prehistoric mammals of the air are bats, two early bats, Icaronycteris and Onychonycteris, and an even earlier protobat, which is hypothetical. Icaronycteris (“Icarus bat”) evidently hunted moths with echolocation about 50 Mya, which bats commonly do today. Onychonycteris (“clawed bat”) is the most primitive bat found so far. It had claws on all five of its wing fingers, unlike two for Icaronycteris and one for modern bats. These flying bats evolved from hypothetical protobats that could glide. They may have evolved from tree-climbing mammals that hung upside down to eat fruit or worms in the fruit. Today we think of bats as living in caves, but originally they evolved in trees, as did the first placental mammals.

Speech at March for Science—Seattle

Here’s the 4-minute speech I gave at the March for Science in Seattle, Earth Day 2017, April 22. That’s Karen up on stage with me, wearing a coral reef on her head. It was an honor to speak and a joy to march.

My topic is how evidence can unite us all. My book, Grandmother Fish, gives children evidence for evolution when they wiggle like a fish and hoot like an ape. Kids love learning that humans are part of the great family of animals. Evidence also says that humans are all one family, as Charles Darwin concluded. Evidence can unite the human family because it allows people to share ideas across cultural boundaries.


“Can you wiggle?”


Karen and I are available for artist and author visits, either together or independently. Contact us here:

Pinnipeds: From Feet to Fins

Valenictus, Enliarctos, and Puijila

The prehistoric mammals of the water are pinnipeds (“fin foots”): the walrus-like Valenictus; the seal-like Enaliarctos; and the otter-like Puijila. Valenictus lived around 5 Mya, and it had no teeth other than its tusks. It evidently ate mollusks, like modern walruses do, rather than fish, as the earliest pinnipeds did. Enaliarctos (“Arctic sea bear”) lived around 20 Mya. It caught fish but took them back to land to eat them, rather than eating them in the water as modern seals do. Puijila (“young seal”) looked like an otter but is more closely related to seals. Charles Darwin speculated that a land-living, fish-hunting species could evolve into an aquatic species as they spent more and more time in the water, and the Pujila fossils provide strong evidence for just this process.

Xenarthrans and Afrotheres: Prehistoric Oddballs

Glyptodont, ground sloth, and mammoth

The prehistoric mammals of the land are two xenarthrans (“strange joints”) and an afrothere (“Africa beast”). The xenarthrans are a glyptodont and a ground sloth, while the afrothere is a mammoth. Glyptodonts (“carved tooth”) were giant armadillos that arose about 20 Mya. Their armor protected them from giant flightless birds and other predators. Ground sloths evolved great size to protect themselves from most predators. They appeared about 35 Mya. Sloths are closely related to anteaters. Like all xenarthrans, they have long, clawed toes and low body temperatures. Xenarthrans evolved in South American after it split from Africa, and they spread to North America when the two land masses connected to each other 3 Mya. Afrotheres evolved in Africa when it was separate from the other land masses, leading to aardvarks, shrew-like tenrecs, manatees, and elephants. Elephants later spread into Asia, and mammoths reached North America. Glyptodonts, ground sloths, and mammoths died out with the end of the last ice age and the arrival of human hunters. Xenarthra and Afrotheria diverged from the other placental mammals long ago in the Mesozoic. Their ancestors either split off separately but at nearly the same time or they split off together and then diverged from each other soon afterwards.

Myriapods: Trash Munchers and Bug Hunters

Millipedes, pauropods, and centipedes

The prehistoric arthropods of the land are Myriapoda (“countless feet”): a gigantic millipede, Arthropleura; a millipede relative, a pauropod; and a predatory centipede. Myriapods were the first land animals. They breathed air in and out through spiracles, which are holes in their exoskeletons. Early myriapods ate rotting plants. Like pancrustaceans, the myriapods had mandibles that were good for chewing food. Millipedes (“thousand feet”) appeared over 400 million years ago, and their body segments were “doubled”, so they had two pairs of limbs per segment. Arthropleura (“jointed ribs”) lived 300 Mya, before the Permian extinction. The biggest Arthropleura were over 2 meters long, as big as the big eurypterids, and the biggest land arthropods ever. On the other hand, Pauropoda (“few feet”) are tiny, and scientists have found no fossil traces of them. They evidently split from the millipedes over 400 million years ago. Centipedes (“hundred feet”) split off even earlier. Unlike their immediate ancestors, centipedes were predators. Their two front legs no longer helped them walk but instead formed pincer-like venomous stingers called forcipules. It’s a sting, not a bite, because forcipules are limbs, not mouthparts. The centipede clade is called Chilopoda (“thousand feet”), and the millipede clade is called Diplopoda (“double feet”).

Chelicerata: Claw-Horns of the Deep

Two eurypterids and an early horseshoe crab

The extinct arthropods of the water are chelicerates: a eurypterid, Hughmilleria; a Stylonurid eurypterid; and an early horseshoe crab, Lunataspis. Eurypterids walked on legs and swam with paddles. They also had chelicerae (“claw horns”), which were claws by their mouths that helped them catch and eat prey. This adaptation helped them dominate the seas. Some, such as Hughmilleria, adapted to habitats with brackish or fresh water. Others, such as most of the Stylonurids, lost their swimming legs and only crawled. Like Eurypterids, horseshoe crabs are descended from the original chelicerate ancestors, along with scorpions, spiders, and other arachnids. These arthropods all arose during the Paleozoic Era, which ended in a great extinction event 252 Mya. Many sorts of arthropods survived, but not the eurypterids.

Pantestudines: Long Necks, Big Teeth, and Hard Shells

Pliosaurus, Plesiosaurus, and Odontochelys

The sauropsids of the water are a Plesiosaurus, a Pliosaurus, and an Odontochelys, an early turtle relative. Early in the Mesozoic Era, several sorts of lizard-like sauropsids swam and hunted in the water. While some lines of sauropsids led to land-loving lizards, pterosaurs, and dinosaurs, other lines evolved into ichthyosaurs, plesiosaurs, turtles, and crocodiles. Plesiosaurus and its close relatives hunted by sight, but scientists aren’t sure what their long, stiff necks were for. Pliosaurus is also part of the clade of plesiosaurs, and they were top predators, guided by sight to ambush or pursue prey. No one is sure where the turtle line originated, but one popular idea is that they arose from the same clade that led to plesiosaurs, called Pantestudines. Ondontochelys had a shell only on its belly. The turtle line later diverged into some lines that live exclusively in the water, some only on land, and many that both swim in the water and crawl on land.

Prehistoric Insects: Crawlers, Flitters, and Hunters

Cockroach (300 million years ago), butterfly (35 Mya), and giant dragonfly relative (300 Mya)

The arthropods of the air are flying insects, a cockroach, Aphthoroblattina; a butterfly, Prodryas; and a dragonfly relative, Meganeura. Over 300 million years ago, insects appeared that could lay their eggs on land they could fold their wings behind them, allowing them to crawl easily. These lines evolved into cockroaches, such as Aphthoroblattina, and later into termites, grasshoppers, walking sticks, and their relatives. The butterfly Prodryas represents the clade of insects that develop first as larvas, then as pupas, and finally as adults. These insects, including ants, bees, and flies, have been even more successful than the roaches and their relatives. Among these insects, butterflies are relatively recent. You can think of butterflies as daytime moths, and they evolved from nighttime moths about 50 million years ago. Scientists know about Prodryas from a single, 35 million year old fossil, but it is one of the best butterfly fossils ever found. Meganeura was a predator living 300 million years ago. With a wingspan of 60 centimeters (2 feet), it was one of the biggest flying insects ever. Their clade died out, but the closely related dragonflies have survived for over 300 million years.