Thread by @parasociality

A hierarchy of alienness: Pictures of animals from least to most related to you.

Least-related animal: Sponges. You and sponges are both animals. That's basically all you've got in common.

You and comb jellies are both eumetazoans: "later animals").

You and jellyfish are both planulozoans: animals with serotonin, a chemical that carries messages between nerve cells in the brain.

You and xenacoelomorphs are both bilaterians: animals with bilateral symmetry as an embryo.

You and mollusks are both nephrozoans: animals with specialized excretory organs, like kidneys.

You and starfish are both deuterostomes: "second mouth," animals characterized by their anus forming before their mouth during embryonic development.

Kinda weird to think you're more closely related to a starfish than an octopus or a butterfly, isn't it?

You and lancelets are both chordates: animals having a notochord at some stage of their development.

You and sea squirts are both olfactores: "smellers."

Again, isn't it weird that you're more related to THIS than to any animal shown above?

You and hagfish are both vertebrates.

You and sharks are both gnathostomes: jawed animals.

You and the bony fishes (i.e., most fishes) are both euteleostomes: bony vertebrates.

You and coelacanths are both sarcopterygians: "fleshy fins," the things that would become your limbs.

You and lungfish are both rhipidistians: "small bellows." In other words, you both have lungs.

You and amphibians are both tetrapods: "four foot."

You and reptiles and birds are all amniotes: animals whose embryos are suspended in fluid-filled sacs.

Note: I've chosen to represent this group with a snake, but note that all amniotes including snakes are still tetrapods (four-foots).

You and the platypus are both mammals: animals whose mothers feed their young milk.

You and opossums are both therians ("wild beasts"): mammals that give birth to live young without a shelled egg.

You and armadillos are both eutherians ("true beasts"): placental mammals, where the fetus is carried in the uterus of its mother to a relatively late stage of development.

You and rhinoceroses are both boreoeutherians ("true beasts of the north"): mammals where the males have scrotums.

You and rabbits are both euarchontoglires, which hilariously translates to: "True rulers and dormice."

This superorder includes both glires ("dormice," rabbits and rodents) and euarchons ("true rulers," the somewhat arrogant name for the group that includes humans).

You and treeshrews are both members of grandorder Euarchonta: "true rulers."

You and colugos are both primatomorpha: "shaped like the noble ones."

You and lemurs are both primates: the "noble ones," the "excellent" or "highest" animals.

Primates are distinguished by large brains, good eyes with color vision, a shoulder girdle allowing a large degree of movement in the shoulder joint, and dextrous hands.

You and tarsiers are both haplorhines: "simple-nosed" primates.

You and New World monkeys (like spider monkeys) are both simians: "snub-nosed," the apelike animals.

You and mandrills are both catarrhines ("flat nose"): Old World monkeys.

Catarrhines lack prehensile tails, have flat fingernails and toenails, a tubular ectotympanic (ear bone), and eight premolars.

You and gibbons are both apes: "Hominoidea," "resembling man."

You and orangutans are both hominids: "Manlike," great apes.

You and gorillas, like the late great Harambe, are both African hominids.

You and chimpanzees are both members of the tribe Hominini: "the tribe of man."

But chimpanzees and bonobos are both part of the genus Pan (named for the Greek god of nature and wilderness), while humans are part of the genus Homo ("man"). They are our closest living relatives.

This has been your tour of your extended family.

From your most distant cousin, the sponge, to your closest living non-human relative, the chimpanzee.

As an aside: Note that sea squirts are chordates, because their larva have a notochord.

The lancelet, pictured before the sea squirt, is also not a vertebrate, and is actually less related to us than the sea squirt.

I know the lancelet looks like a fish, but they're not really a fish, just "fish-like."

If you watch a video you'll get a sense of how distantly related they are. In motion, it looks more like a worm than a fish:

I got a question about what this means for other mammals.

The non-Boreoeutheria mammalian superorders are Afrotheria ("wild beasts," elephants & aardvarks) and Xenarthra ("strange joints," armadillos and sloths).

In both cases, the males' testicles are always fully internal.

Note: Hagfish are vertebrates (subphylum Vertebrata), BUT they don't actually have a spine. Just rudimentary vertebrae.

Taxonomists have even debated whether hagfish should in fact be classed as vertebrates, but current consensus says they are.

Since posting, I have been informed that placing a rabbit on its back is called "trancing" them: induces them to lie still and feign death.

It's a cute photo, but you it's not something you should usually do to them, because it may scare them and make them injure themselves.

I ended the list too soon. Our closest living relative is: Ourselves.

You and all humans are members of the genus Homo ("man's sort," "mankind").

Humans are the sole extant species in our genus. Being one species means we can breed together & the resulting offspring are fertile

Question from @gomes_ha: Where do insects branch off?

The answer is: the octopus entry. That entry is doing a lot of work, because the clade Nephrozoa is huge & diverse.

Insects, like octopuses & us, are nephrozoans.
Unlike us, but like octopuses, insects are not deuterostomes.

Mollusks (octopuses), arthropods (butterflies), and annelids (earthworms) are all protostomes: "first mouth."

Their mouth is derived from the embryonic blastopore.

In contrast, in us deuterostomes ("second mouth") the blastopore becomes our anus in embryonic development.

Every animal on the list including and after the starfish is a deuterostome.

You're about as closely related to a butterfly as you are to an octopus or an earthworm.
But butterflies, earthworms, and octopuses are all more closely related to each other than they are to you.

Another topic: Birds & reptiles.

Traditional taxonomy considered reptiles (Reptilia) and birds (Aves) to be separate classes of amniotes, alongside Mammalia.

Modern taxonomy treats both birds & reptiles as part of a common clade, Sauria.

Clade Sauria is divided into two big groups:

1) Archelosaurians: Birds, crocodilians and turtles

Within the archelosaurians, birds and crocodilians together form the archosaurs: "ruling lizards."

Crocodilians are birds' closest living relatives, and vice versa.

A crocodile is actually more closely related to a sparrow than to a turtle, snake or lizard!

Besides archelosaurians, the other big group of clade Sauria is:

2) Lepidosaurians: Snakes, lizards (iguanas, geckos, etc.), and tuataras

Tuataras (pictured) look like lizards, but they're pretty distinct. They lacks eardrums and earholes, for example.

Snakes and lizards are more closely related to each other than either is to tuataras.

Together, snakes and lizards are called squamates: "scaled ones."

To recap:
An alligator is more closely related to a pigeon than a turtle, and more closely related to a turtle than to a cobra.
A turtle is more closely related to a hawk than to an iguana.
An anaconda is more closely related to a gecko than to tortoise.

Simple right?

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