Could you maybe clarify all the terms on your cladogram? I mean I know that they're all defined by evolutionary relationship and stuff but maybe both define them AND provide an example animal? I'm just a little confused by some of the names...
Oh yeah, sure!
Chordata (Brick Red): Tunicata + Craniata + Cephalochordata; their most recent common ancestor, and all its descendants. Typically characterized by having a notochord, a dorsal neural tube, pharyngeal slits, a post-anal tail, and an endostyle at some stage of their lives. Examples include hagfish, sea squirts, sharks, sea bass, lungfish, frogs, humans, birds, and lizards (all vertebrates are chordates).
Vertebrata (Red): Myllokunmingia + Gnathostomata (+ MRCA and all descendants); typically all chordates that have a backbone. Includes: sharks, sea bass, lungfish, frogs, humans, birds, lizards, and lampreys.
Gnathostomata (Brown): Chondrichthyes + Placodermi + Teleostomi (MRCA & des.; jawed vertebrates. Includes: Sharks, sea bass, lungfish, frogs, humans, birds, and lizards.
Placodermi (Beige): All gnathostomes more closely related to Dunkleosteus than to any living “fish”; these are the “armoured fish” that had huge armor plating on their heads. All non-placoderm Gnathostomes are in Eugnathostomata. Includes Dunkleosteus; all are now extinct.
Chondricthyes (Orange): All Eugnathostomatans more closely related to Carcharodon than to humans; is all cartilaginous fish. Originally it was thought that bony fish evolved from cartilaginous fish, however, it has since been found that both diverged from a common Placoderm ancestor. Includes sharks and rays.
Teleostomi (Yellow): All Eugnathostomatans more closely related to humans than to Carcharodon; “bony fish”. Includes sea bass, lungfish, frogs, humans, birds, and lizards. It is subdivided into Acanthodii & Euteleostomi.
Actinopterygii (Olive Green): All Euteleostomis more closely related to sea bass than to humans. “Ray-finned fish”. Includes sea bass, clownfish, tuna, and goldfish.
Sarcopterygii (Lime Green): All Euteleostomis more closely related to humans than to sea bass. “Lobe-finned fish”. Includes lungfish, coelacanth, frogs, humans, birds, and lizards.
Tetrapoda (Light Green): Frogs + Humans, MRCA & all its descendants. Essentially, all land vertebrates - there are many forms of lobe-finned fish that were able to crawl onto land that form Tetrapoda’s most recent ancestors, but tetropoda proper is just all the descendants of the MRCA for all modern land animals (amphibians, sauropsids, and mammals). Includes frogs, humans, birds, and lizards.
Lissamphibia (Green): Caecilians + Frogs, MRCA & all its descendants. Essentially amphibians, though it excludes many extinct amphibians (when you use the term amphibian to mean all non-amniote tetrapods). This might not actually be a proper cladistic group, but I included it as it definitely does not contain any amniotes. Includes caecilians, frogs, and salamanders.
Amniota (Dark Green): Humans + Birds, MRCA & all its descendants. All hard-shelled-egg laying land animals (specifically, they produce an egg with an amnios, allowing the animal to lay the egg on land, rather than water). Even though many mammals (and some reptiles!) have secondarily lost this ability, their ancestors did have it, making them a part of this group. Includes humans, birds, and lizards.
Synapsida (Seafoam): A group of amniotes that includes mammals and all amniotes more closely related to mammals than other living amniotes. Synapsids are not reptiles; though many non-mammalian synapsids resemble them heavily. They are easily characterized by their skulls: many amniotes have temporal fenestra (a hole behind their eye socket); synapsids only have one of these. Most reptiles have two. Includes Dimetrodon, humans, and whales.
Mammalia (Teal): Platypus + Humans, MRCA & all its descendants. All mammals, essentially. Mammals are typically characterized by the ability to produce milk from mammary glands. Most don’t lay eggs, but either give birth to their young in a pouch (marsupials) or grow the young inside of a placenta (placentals, aka us). Includes echidnas, humans, whales, and kangaroos.
Sauropsida (Aqua): All amniotes more closely related to birds than to mammals. Essentially reptiles. Since birds and dinosaurs are included in this group, there aren’t a whole heck of a lot of good unifying characteristics. Many sauropsids are endothermic (warm-blooded); many have feathers in addition to scales; and some even give birth to live young. Includes turtles, plesiosaurs, lizards, tuatara, snakes, mosasaurs, icthyosaurs, crocodiles, pterosaurs, dinosaurs, and because it includes dinosaurs, birds.
Lepidosauria (Dark Purple): Lizards + Tuatara, MRCA & all its descendants. Characterized by having overlapping scales. A part of the larger group Lepidosauromorpha within Sauropsida. Includes lizards, tuatara, snakes, and mosasaurs.
Squamata (Purple): Lizards + Snakes; MRCA & all its descendants. Characterized by skins with horny scales and shields, and can move the upper jaw as well as the lower jaw (not something most jawed vertebrates can do). Includes lizards, snakes, and mosasaurs.
Mosasauridae (Lavender): Mosasaurus + Plioplatecarpus, MRCA & all its descendants. The mosasaurs - large marine reptiles, similar to monitor lizards, but elongated and streamlined for swimming. Extinct now. Includes - you guessed it - Mosasaurus, as well as Tylosaurus and many others.
Serpentes (Fuchsia): Blind snakes + Vipers, MRCA & all its descendants. Essentially all snakes. They’re distinct from lizards due to lack of eyelids and external ears - there are many legless lizards, but snakes are a specific group of “lizards” (given that squamates on the whole can be called lizards). Includes the garter snake, blind snakes, and cobras.
Ichthyosauria (Hot Pink): All animals more closely related to Icthyosaurus than to Grippia; essentially, a group of sauropsids not a part of Lepidosauromorpha or Archosauromorpha. They were adapted for completely aquatic life and are now completely extinct; they sort of looked like dolphins. Includes Icthyosaurus, Opthalmasaurus, and Mixosaurus.
Archosauromorpha (Azure): Birds + Crocodiles + Turtles, MRCA & all its descendants. Essentially all modern sauroposids more closely related to birds than to lizards, though of course it includes many extinct groups as well that are descended from their most recent common ancestor. This is a very diverse group with a wide variety of characteristics. Includes turtles, plesiosaurs, crocodiles, pterosaurs, dinosaurs and therefore birds.
Pantestudines (Dark Violet): All sauropsids more closely related to turtles than any other animal. A group of archosaurimorphs. Genetic analyses have shown strong evidence that they are more closely related to archosaurs than to lepidosaurs; these genetic analyses that include fossils also reveal that animals such as plesiosaurs and placodonts are in this group. Includes turtles, plesiosaurs, Liopleurodon, and Placodus.
Plesiosauria (Plum): Plesiosaurus + Peloneustes, MRCA & all its descendants. The plesiosaurs - the long-necked (though many lost this) marine reptiles from the Mesozoic. This group also includes the pliosaurs, which on the whole lost the long necks characterizing the group. Includes Plesiosaurus, Elasmosaurus, Kronosaurus, and Liopleurodon.
Testudines (Violet): Xinjianchelys + Trionyx, MRCA & all its descendants. Essentially, all modern turtles - characterized by having a shell developed from the ribs that acts as a shield. The classification of turtles has been a struggle, given that they are anapsids - meaning, they have no temporal fenestra. The earliest amniotes were anapsids and it was assumed from fossil evidence that turtles, therefore, were descended directly from them, and were not part of any more derived amniote groups (such as synapsids or archosaurs). Most sauropsids are diapsids - meaning, they have two temporal fenestrae. It has since been theorized, however, that turtle ancestors were diapsids; turtles actually lost their temporal fenestrae during their evolution. This is not a completely ridiculous idea, of course; many traits are secondarily lost in groups, making classification by traits a nightmare and unfeasible. Genetic analyses have revealed that the closest living relatives for turtles are crocodiles and birds, making them a part of Archosauromorpha. Includes Green sea turtles, the African spurred tortoise, and terrapins such as the Red-eared turtle.
Archosauria (Cerulean): Crocodiles + Birds, MRCA & all its descendants. Characterized by having teeth in sockets, though some archosaurs (such as birds) lost their teeth secondarily. Many members of the group have erect or partially erect gaits, unlike other sauropsids, which have sprawling gaits (such as lizards). Archosaurs were the dominant land vertebrates for the entirety of the Mesozoic Era (though dinosaurs were only really during the Jurassic and Cretaceous; a wide variety of archosaurs were common throughout the Triassic). Given that birds are far more diverse than mammals; it can still be argued that archosaurs continue to be the dominant land vertebrates today. Includes crocodiles, pterosaurs, dinosaurs and therefore birds.
Pseudosuchia (Aqua): Living crocodilians and all archosaurs more closely related to crocodilians than birds. They have massively built skulls, and many still have the typical reptilian sprawl, though some have an erect gait. They typically also had armored plates. Includes crocodiles, alligators, Deinosuchus, phytosaurs, and aetosaurs.
Ornithodira (Indigo): A subgroup of Avemetatarsalians, which is all archosaurs more closely related to birds than to crocodiles. Ornithodira is, specifically, Dinosaurs + Pterosaurs, MRCA, and all descendants (Ornithodira was easier to fit into the diagram). This group potentially has protofeathers as a characteristic of the entire clade, though many lost them secondarily (such as hadrosaurs). Includes almost all flying vertebrates. Members include Scleromochlus, all pterosaurs, all dinosaurs and therefore all birds.
Pterosauria (Blue-Violet): Anurognathus + Preondactylus + Quetzalcoatlus, MRCA & Descendants. The pterosaurs. These are all of the “flying reptiles” that one typically knows about from the Mesozoic Era. They had pycnofibres - small filaments similar to hair, potentially the same as protofeathers; and flew using membraneous wings that stretched across an extended finger. Includes Dimorphodon, Pteranodon, Pterodactylus (”pterodactyl”), and Ornithocheirus.
Dinosauria (Blue): Megalosaurus + Iguanodon, MRCA & descendants. All dinosaurs. Note that this does not include many of the animals listed above! Dinosaurs are a very specific group of animals that all, typically, were able to walk with the limbs directly beneath the body. Protofeathers were also an ancestral trait for this group, though many dinosaurs secondarily lost them - the same proteins that make protofeathers were turned into scales. Includes Brontosaurus (yes, it’s a thing again, there was a study this year), Stegosaurus, Triceratops, Tyrannosaurus, Allosaurus, Velociraptor, Brachiosaurus, Troodon, Parasaurolophus, Ankylosaurus, Pachycephalosaurus, Archaeopteryx, the Dodo, Bald Eagles, Emus, Cassowaries, Chickens, Ducks, Finches, Parrots, Robins, Crows, Geese, Blue Jays, Penguins, Auks, Seagulls…
Avialae (Light Blue): All dinosaurs more closely related to modern birds than to Troodon. This is typically the group I mean when I say “birds,” though the clade that includes only modern birds is called Neornithes - all non-Neornithes Avialaens are extinct. Many basal Avialae, furthermore, are almost indistinguishable from their closest dinosaurian relatives, the troodontids. It is uncertain whether the earliest Avialaens (such as Archaeopteryx) could properly fly. Includes Archaeopteryx, Confuciusornis, Hesperornis, the Dodo, Bald eagles Emus, Cassowaries, Chickens, Ducks, Finches, Parrots, Robins, Crows, Geese, Blue Jays, Penguins, Auks, Seagulls… essentially, all birds.
I hope that was helpful!