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Calling a Whale a Fish

Confusing Common-Name Cladistics

Posted: Apr 28th, 2022 - Modified: Nov 28th, 2022
  • An uneducated person might think that whales are fish.
  • An educated person knows that whales aren’t fish; they’re mammals.
  • A fan of the show QI knows that there is No Such Thing As A Fish.
  • The enlighted pedant knows that whales are fish because all mammals are fish.

So goes the internet discourse.

Pufferfish, you see, share a more recent ancestor with humans than they do with sharks. Any group consisting of only the things called ‘fish’ is a group defined by physical features rather than shared ancestry. Fish, in other words, aren’t a true clade.1

These kinds of discussions can be somewhat silly, but let’s run with the fish example, and look for other similarly silly animal classifications.

The following is a cladistic tree of life using common names instead of latin names. When a common-name describes a non-clade group, I’ll play a bit fast and loose with that common name to turn it into a clade. The goal here is to create a tree of life which is as baffling as possible, without, strictly speaking, being wrong. Explanations are down below.

The (Partial) Animal Family Tree

┃ ┣╸Spiders: 🕷️🦂
┃ ┗╸Shrimps 
┃   ┣╸Prawns: 🦀🦞🦐
┃   ┗╸Insects
┃     ┣╸Wasps: 🐜🐝
┃     ┣╸Flies: 🦟🪰
┃     ┣╸Moths: 🦋🐛
┃     ┣╸Beetles: 🪲🐞
┃     ┣╸Crickets: 🦗
┃     ┗╸Cockroaches: 🪳
┣╸Mollusks: 🐙🦑🐚🐌🦪
┣╸Segmented Worms: 🪱
  ┣╸Sharks: 🦈
  ┣╸Ray-finned Fish: 🐟🐠🐡
  ┗╸Lobe-finned Fish
    ┃ ┣╸Possums: 🐨🦘
    ┃ ┗╸Shrews
    ┃   ┣╸Supraprimates
    ┃   ┃ ┣╸Rodents: 🐭🐁🐀🐹🐿️🦫
    ┃   ┃ ┣╸Rabbits: 🐰🐇
    ┃   ┃ ┗╸Monkeys: 🐵🐒🦍🦧🤸
    ┃   ┣╸Even-toed Ungulates:
    ┃   ┃ ┣╸Camelids: 🐪🐫🦙
    ┃   ┃ ┣╸Whippos: 🦛🐳🐋🐬
    ┃   ┃ ┣╸Pigs: 🐷🐖🐗
    ┃   ┃ ┗╸Deers
    ┃   ┃   ┣╸Giraffes: 🦒
    ┃   ┃   ┣╸Elk: 🦌
    ┃   ┃   ┗╸Antelopes: 🦬🐮🐂🐃🐄🐏🐑🐐
    ┃   ┣╸Odd-toed Ungulates: 🐴🐎🦄🦓🦏
    ┃   ┣╸Carnivorans:
    ┃   ┃ ┣╸Cats: 🐱🐈🐈‍⬛🦁🐯🐅🐆
    ┃   ┃ ┗╸Dogalikes
    ┃   ┃   ┣╸Dogs: 🐶🐕🦮🐕‍🦺🐩🐺🦊
    ┃   ┃   ┣╸Bears: 🐻🐻‍❄️🐼
    ┃   ┃   ┣╸Seals: 🦭
    ┃   ┃   ┗╸Stinkers: 🦝🦦🦡🦨
    ┃   ┣╸Bats: 🦇
    ┃   ┣╸Hedgehogs: 🦔
    ┃   ┣╸Elephants: 🐘🦣
    ┃   ┗╸Sloths: 🦥
    ┃ ┣╸Lizards: 🦎🐍
    ┃ ┣╸Turtles: 🐢
    ┃ ┣╸Crocodilians:🐊
    ┃ ┗╸Dinosaurs
    ┃   ┣╸Longnecks: 🦕
    ┃   ┣╸Tyrants: 🦖
    ┃   ┗╸Birds
    ┃     ┣╸Ratites
    ┃     ┣╸Fowl
    ┃     ┃ ┣╸Landfowl: 🦃🐔🐓🐣🐤🐥🦚
    ┃     ┃ ┗╸Waterfowl: 🦆🦢
    ┃     ┗╸Newbirds
    ┃       ┣╸Flamingos: 🦩
    ┃       ┣╸Doves: 🕊️🦤
    ┃       ┣╸Penguins: 🐧
    ┃       ┗╸Birds of Prey: 🦅🦉🐦🦜
    ┗╸Frogge: 🐸

Explanations for Clade Names

Dinosaurs (Dinosauria)

Dinosaurs, as the category exists in the imagination of children and film-makers, are not a clade.

It’s only once birds are included that the category of dinosauria becomes cladistic. Hence why dinos, of the pop-culture terrible lizardy beast variety, are called non-avian dinosaurs by science educators.

The term “dinosaur” was coined back when only a few of the beasties were known (namely Megalosaurus, Iguanodon, and Hylaeosaurus). Further study revealed that any clade containing these three creatures must also contain birds, and thus the term “dinosaur” was expanded to include chickens, doves, kiwis, etc. This was a perfectly reasonable choice, as the term “dinosaur” was invented for the sake of scientific classification, and only later spread into pop-culture as a term for big scary lizardy beasts.

What about Pterosaurs?

Sidenote: Pterosaurs aren’t in the clade of dinosauria, but they’re more closely related to dinosaurs than they are to anything else, so I think it’s perfectly reasonable to include them in the pop-culture category of dinos. But if you want a more proper name, the clade containing both dinosaurs and pterosaurs is called Panaves, meaning ‘every bird’, or Avemetatarsalia, meaning ‘bird-footbones’. Eugh. Those names are both boring and confusing. I much prefer Ernst Haeckel’s suggestion that the clade by called dracones, which is just latin for ‘dragons’.

Fishes (Vertebrata)

Fish are not a clade. The common ancestor of sharks, tuna, hagfish, and lungfish, is also the ancestor of tetrapods (reptiles, birds, mammals, and amphibians; all typically four-limbed land creatures). Vertebrata is the name for the clade which includes tetrapods and fish, and its members are called vertebrates.

Thus fish, as usually defined, is the group consisting of non-tetrapod vertebrates. To make “fish” into a clade, we must include whales, chickens, and the like.

The remaining examples are listed in roughly decreasing order of sensibility:

Elephants (Elephantidae)

Asian Elephants are more closely related to Mammoths than they are to African Elephants. Mammoths were fuzzy elephants that recently went extinct. (Mastodons were slightly different creatures.)

Doves (Columbidae)

Columbidae is the clade of pigeons and doves. There is no rigorous distinction between the two terms; I used “doves” in the tree above because it sounds more lovely. The extinct dodo was a large ground-pigeon.

Lizards (Squamata)

Lizards are not a clade. Snakes are a clade. So are amphisbaenians. All three of these types of critters are called squamates in the order squamata. A lizard is any non-snake, non-amphisbaenian squamate.

This one seems like it might be a reasonable category; snakes and amphisbaenians are both mostly legless, so a lizard is just a squamate that still has its legs, right? Well no, there are loads of legless lizards. As described by a professional reptile nerd in this amusing rant, there are over twenty lineages of legless lizards, so it seems bizarre that these two in particular are excluded as not being lizardy enough for the lizard club. You know what? His rant is convincing. Snakes are lizards, and not just for the purposes of this exercise. hashtag lizard unity hashtag snakesarelizards

Rabbits (Leporidae)

You might not even be aware that rabbits and hares are different things. Cladistically, they really aren’t. Rabbits usually dig burrows underground, and are born helpless (like us!). By contrast, hares build nests aboveground and are born ready to hop. It’s primarily a distinction based on nesting behavior, not ancestry. An encyclopedia might define hares cladistically as the genus lepus and then define rabbits as the non-hare leporids. But for this exercise, hares are rabbits.

Moths (Lepidoptera)

Butterflies are a clade of moth which tend to be more colorful and come out during the day. Moths are just non-butterfly lepidopterans. And to make ‘moths’ into a clade, the butterflies must be included.

Note that the emoji 🐛 represents an ambiguous species. Most emoji sets depict it as a baby moth, but some depict it as a centipede.

Wasps (Apocrita)

🐝 Bees are a clade. 🐜 Ants are a clade. Wasps are just any of the species related to bees and ants which are neither bees nor ants. So cladistically, bees and ants are specific kinds of wasps.

Cockroaches (Blattodea)

This is similar to the wasp situation. Termites are a clade. Cockroaches are only a clade if termites are included. Termites are essentially eusocial cockroaches.

Bugs (Arthropoda)

A bug expert might insist that “bug” refers only to a specific clade of insects, either hemiptera or heteroptera, depending on who you ask. But we all know what a bug is. It’s a creepy crawly little whatzit with too many skittery legs. It’s near synonymous with “arthropod”.

I’m not the only one who uses the term “bug” this way. is about “Insects, Spiders & Their Kin”, for example. The “bug” emoji 🐛 doesn’t depict a “true bug”, either.

(Ignore the fact that bacteria are sometimes called bugs, because then every living organism would cladistically be a bug.)

Monkeys (Simiiformes)

A monkey is a non-ape simian. There are two different clades of monkeys, and any clade that includes both will also include the apes. Members of that shared clade are called “anthropoids” or “simians”. But for this exercise, I’m calling apes “Monkeys” for the same reason that I’m calling them “Fish”.

Sharks (Chondrichthyes)

Sharks and rays are in the clade Chondrichthyes, which means Cartilaginous Fish, and that’s what this group is usually called. Unlike other fish, which have hard bony skeletons, sharks and their relatives have skeletons mostly made of flexible cartilage. In addition to actual sharks, this group includes rays (one family of which are called carpenter sharks) and chimaeras (some species of which are called ghost sharks).

Crickets (Orthoptera)

The only thing which prevents crickets (Ensifera) from being a clade are pygmy mole crickets (Tridactylidae), which are more closely related to grasshoppers. Crickets and grasshoppers together form the clade Orthoptera, which means ‘straight wings’.

Here marks the point where things start getting downright silly.

Antelopes (Bovidae)

Antelopes are not a clade. The clade which contains antelopes is called Bovidae, and its members are called bovids, which means ‘cattle-like’. Cows are bovids, of course. So are sheep, goats, and musk ox. An antelope is simply any bovid which people don’t care enough about to lump it into its own category. I suppose you could cheekily define an antelope as any non-algricultural bovid.

“Bovid” is simple enough to be used as a common-name, but for this silly exercise, we’re going to call all bovids ‘antelopes’.

The clade would become even more expansive if pronghorns were included. Pronghorns are often called American Antelope, but they aren’t even bovids; Pronghorn are their own weird thing. The clade which includes both bovids and pronghorns is called Pecora, which, like bovidae, can be translated as ‘cattle-like’. Deer and giraffes are also pecorans.

So an antelope in the broadest sense is anything related to cattle which isn’t similar enough to cattle to be called cattle, but which isn’t different enough to be called something else. 🤷

Deer (Ruminantia) and Elk (Cervidae)

Deer are a clade if, by ‘deer’, we mean only the cervids, members of the clade Cervidae, which includes caribous and moosen.

But there are two non-cervid critters which are also called ‘deer’. The first is the musk-deer, which is a stinky little fanged fella more closely related to antelopes than to elk. The second is the tiny mouse-deer, also called the chevrotain. The clade which includes both cervids and chevrotains is called Ruminantia and its members are call ruminants, named after their tendency to regurgitate and rechew their food.

If my goal here were to find sensible common names for clades, then “Ruminant” is a fine term, fairly common, with its own related idioms.

But my goal is not to be sensible. As described above, deer are pecorans antelopes. Well, antelopes are also ruminants deer. (Hopefully it’s clear now why biologists use cumbersome Greco-Latin names for clades.)

And what then shall we call the cervids, the “true deer”? Well, there are two species of deer called “elk” - the wapiti, and the moose. And these two species are very distant from one another on the cervid family tree. The only clade that includes both of them is cervidae itself.

Spiders (Arachnida)

Actual spiders are members of the clade Araneae. The arachnids are a broader clade which also includes scorpions, ticks and daddy long-legs, among others.

As with deer, there are a few species in the broader clade which are also called spiders. Namely, animals in the clade Solifugae are often called sunspiders or camel spiders. Daddy long-legs are sometimes called “spiders” as well. The only clade which includes both these and true spiders is Arachnida.

Solifugae are also called wind scorpions, so by the same logic, we could expand “scorpion” to refer to all of Arachnida. But “arachnid” comes from the Greek word for spider, so that feels more natural.

Shrimps (Pancrustacea) and Prawns (Decapoda)

Shrimps are not a clade. A shrimp is basically any little crustacean that swims about and looks… er… shrimpy. There are many different groups of creature called “shrimp” scattered all over the crustacean family tree. To turn “shrimp” into a clade, you could either declare one and only one of these groups to be True Shrimp, and insist all the others are imposters. Or you could shrug your shoulders as I’m doing here and say “sure, all crustaceans are shrimps”. Lobster? Big shrimp, so big he has trouble swimming. Crab? That’s a big shrimp who folded up his tail.

An additional complication is that scientists have recently learned that insects are crustaceans, cladistically speaking. For example, the brine shrimp (called Sea-monkeys when sold as pets) are more closely related to butterflies than they are to lobsters.2 So in this exercise, insects are crustaceans, and crustaceans are all shrimps, so insects are shrimps.

Meanwhile, the ‘classic’ crustaceans are in the clade Malacostraca, which means ‘soft-shell’ in Greek. Aristotle gave them this name because their shells crush under pressure, in constrast to harder-shelled animals (like snails and oysters) whose shells shatter under pressure.3 The most familiar Malacostracans - 🦀🦞🦐 crabs, lobsters, and the other big shrimps people like to eat - are Decapods, in the clade Decapoda, meaning ‘ten-feet’. Malacostraca includes the decapods as well as other creatures like mantis shrimp and roly-polies (isopods).

I wanted to find a common-name which cladistically includes all of the decapods, and settled on “Prawns”. Like “shrimp”, “prawn” has no precise scientific meaning. A critter is prawn if it looks like a prawn, and whether a critter is called a “prawn” or a “shrimp” often comes down to regional slang.4 But unlike “shrimp”, the application of the name “prawn” seems limited to decapods.

Worms (Bilateria)

Between the segmented worms, the round worms, the arrow worms, the flat worms, the velvet worms, the various arthropods called ‘worms’ (eg silkworms), and the snakes from whence the word originates via “wyrm”, worms cover most of the animal family tree. Nearly all animals, excepting a few simple creatures like jellies and sponges, are bilaterally symmetric creatures with body plans built around a central tube - they’re worms, cladistically and structurally.

Birds of Prey (Telluraves)

Birds of Prey, (aka “Raptors”, though Jurassic Park has completely changed the meaning of that term,) are the big fierce hunter birds. Eagles, hawks, falcons – you know the lot. It was a sensible guess that these birds might be a clade, but it is now known that falcons are more closely related to parrots and songbirds. The clade containing all the birds of prey is now called “Telluraves”, which means “Earth-birds” or “Land-birds”. Owls and woodpeckers are also telluravians.

The 🐦 emoji is displayed as different species depending on the emoji set, but all of the identifiable species (bluebird, cardinal, canary, parrot) are telluravians.

Shrews (Placentalia)

What’s a shrew? True shrews are a clade, closely related to hedgehogs. But there are also tree shrews and elephant shrews. All three of these creatures were once thought to be closely related, but tree shrews are now know to be more closely related to primates, and elephant shrews are known to be more closely related to elephants than they are to true shrews (that’s not a joke).

The smallest clade that includes all of these shrews is Placentalia, encompassing all of the placental mammals - sheep, whales, elephants, you, your dog…

A similar argument could be made to expand ‘mole’ to apply to all placental mammals, by way of the true moles and the golden moles. But ‘shrew’ sounds funnier, and I’ve heard it said that the shrew’s bodyplan is in some sense the ‘default’ mammalian bodyplan.

There’s also various species called “marsupial shrews” and “shrew possums”, which would expand our shrew clade to include all the placental mammals and the marsupials. But unlike the previous shrews mentioned, biologists never grouped marsupial shrews together in the same clade with the other shrews; the pouch makes the difference clear. And besides, there are also creatures called “marsupial mice”, “marsupial moles”, “marsupial tapirs”, and the “Tasmanian tiger”. And in Chinese, kangaroos are called “pocket rats”. People just weren’t being very creative when they named some of these marsupial critters.

Possums (Marsupalia)

Speaking of marsupials, possums are not a clade. To make possums into a clade, the macropods (kangaroos, wallabies, etc.) must be included5.

Possums aren’t the same thing as opossums (american marsupials famous for playing dead) or shrew-oppossums (a marsupial which is neither a shrew nor an oppossum). But opossums are often called “‘possums”, and possums were named for their similarity to opossums. So here, I’ve lumped them together. The smallest clade that includes all the (o)possums is the clade which includes every marsupial.

Other Clade Names Used

In some cases, I wasn’t able to find a common name which could be expanded to cover a clade, and didn’t want to just list each species individually.

Actual Clade Names

  • Insects (Insecta)
  • Flies (Diptera)
  • Beetles (Coleoptera)
  • Mollusks (Mollusca)
  • Segmented Worms (Annelida)
  • Ray-finned Fish (Actinopterygii)
  • Lobe-finned Fish (Sarcopterygii)
  • Mammals (Mammalia)
  • Supraprimates - It rolls off the tongue better than the synonym Euarchontoglires, which means soemthing like ‘true-ancestors-and-dormice’.
  • Rodents (Rodentia)
  • Camelids
  • Pigs (Suidae)
  • Giraffes (Giraffa) - I didn’t put Okapi on the tree. Okapi aren’t giraffes, but they are giraffids.
  • Carnivorans (Carnivora)
  • Cats (Felidae)
  • Dogs (Canidae)
  • Seals (Pinnipeds) - A sea lion is an eared seal. A walrus is a seal that hosts MythBusters.
  • Bats (Chiroptera)
  • Hedgehogs (Erinaceidae) - These used to be called “urchins”. Closely related to the true shrews and moles.
  • Sloths (Folivora)
  • Crocodilians - Secret taxonomy tip: Never worry about whether it’s a crocodile or an alligator. Just call them both crocodilians.
  • Turtles (Testudines)
  • Ratites - This is the term for those weird flightless birds. Kiwis, emus, and the like. The name comes from the shape of their sternum.
  • Fowl (Galloanserae), Landfowl (Galliformes), and Waterfowl (Anseriformes)
  • Frogs (Anura) - Toads are just ugly frogs.

‘Translated’ Names

  • Dogalikes (Caniformia)
  • Even-toed Hoofers (Artiodactyla) and Odd-toed Hoofers (Perissodactyla) - These two clades are often called “ungulates”, which is a Latin term referring to their hooves. I’ve translated “Ungulate” as “Hoofer”. <aside>I have been informed that “hoofer” is a term for a tapdancer. I’m not changing it; I like the imagery.</aside>
  • Newbirds (Neoaves) - It’s difficult to determine the relationships between birds within this clade because it underwent very rapid speciation after most of the dinos got wiped out 6. I’ve sidestepped the issue by only listing a few of the sub-clades.
  • Tyrants (Tyrannosaurus) - Listing all Theropods would make birds a subset, and I didn’t want to indent that sublist an extra time.

Other Clade Names

  • Stinkers (Musteloidea) - Most of the species in this clade are noted for their use of anal-gland secretions for use in communication and defense. “Badger” would also work as a name for the clade because there is a skunk species called the “stink badger”.
  • Longnecks (Sauropods) - They’ve got the longest necks. It’s a good name. Thanks to The Land Before Time for this one.
  • Whippos (Whippomorpha) - It’s not a common term at all, but what a fun word.

OneZoom Tree of Life
Zoomable fractal showing the tree of life. Playing around with it, it does seem like many of the branches are outdated.
A fork of OneZoom. More up to date, but only depicting the tetrapods.
Tree of Life web project
Hypertext tree of life with a seperate page for each node.


  1. A clade is any group of organisms which share a common ancestor, such that all of the descendants of that common ancestor are included in the group. 

  2. A Phylogenomic Solution to the Origin of Insects by Resolving Crustacean-Hexapod Relationships Combosch Giribet Nelson Schwentner (2017). (Sea-monkeys are a kind of Branchiopoda). This paper says something called Remipedia are even closer to insects, but I’ve never even heard of Remipedes before. 

  3. From a translated copy of Aristotle’s History of Animals

    Another genus is that of the malacostraca. These are animals that have their hard structure outside, and their soft or flesh-like substance inside, and the hard substance belonging to them has to be crushed rather than shattered; and to this genus belongs the crawfish and the crab.

  4. Several examples of such regional differences are given on page 108 of This is Not a Weasel, by Philip B Mortenson. 

  5. From An emerging consensus in the evolution, phylogeny, and systematics of marsupials and their fossil relatives (Metatheria) Beck, Croft, Eldridge, Fox, Travouillon (2019):

    A monophyletic grouping of all “possums” (Phalangeroidea + Petauroidea)… was initially supported by DNA hybridization data (Kirsch et al. 1997) … However, this arrangement has received little support in subsequent molecular studies. Instead these analyses have allied Macropodiformes with either Phalangeroidea (Phillips and Pratt 2008; Meredith et al. 2009a, 2009b, 2009c), consistent with some morphological evidence (Szalay 1994), or with Petauroidea (Meredith et al. 2011; Mitchell et al. 2014; May-Collado et al. 2015), but without strong support for either arrangement.

  6. Data Types and the Phylogeny of Neoaves. Braun and Kimball (2021). This paper compares the different versions of the bird family tree. Studies agree about some parts of the family tree, but disagree about others. (e.g. what’s going on with the hoatzins?) The language in this article is very technical, but the pictures give ample context. 

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