Invertebrates to Fish
- Pikaia gracilens — extremely primitive notocord
- Conodont— ray fins and a notocord
- Haikouichthys — A notochord with separate vertebral elements (craniate)
- Arandaspis — Well armoured jawless fish
- Birkenia — primitive, jawless fish or fishlike vertebrate 
- Guiyu — The oldest known bony fish
Jawless fish to shark
- Cladoselache — intermediate between jawless fishes to sharks
- Tristychius — another sharklike fish.
- Ctenacanthus — first primitive shark.
- Paleospinax — sharklike jaw, primitive teeth.
- Spathobatis — First ray-like fish.
- Protospinax — Ancestral to both sharks and skates.
Jawless fish to bony fish
- Acanthodians — similar to early bony fishes, possibly a transitional form.
- Palaeoniscoids — primitive bony fishes.
- Canobius, Aeduella — more advanced jaws.
- Parasemionotus — combination of modern cheeks with more primitive features, like lungs
- Oreochima — first teleost fish
- Leptolepids — ancestor of modern teleost fish. Lung transformed into swim bladder.
- Amphistium and Heteronectes — transition to the eye location of flatfishes.
Fish to amphibian
- Paleoniscoids — both ancestral to modern fish and land vertebrates.
- Osteolepis — modified limb bones, amphibian like skull and teeth.
- Eusthenopteron, Sterropterygion — fin bones similarly structured to amphibian feet, but no toes yet, and still fishlike bodily proportions.
- Panderichthys, Elpistostege — tetrapod-like bodily proportions.
- Obruchevichthys — fragmented skeleton with intermediate characteristics, possible first tetrapod.
- Tiktaalik — a fish with developing legs. Also appearance of ribs and neck.
- Acanthostega gunnari — famous intermediate fossil. most primitive fossil that is known to be a tetrapod
- Ichthyostega — like Acanthostega, another fishlike amphibian
- Hynerpeton — A little more advanced then Acanthostega and Ichtyostega
- Labyrinthodonts — still many fishlike features, but tailfins have disappeared
- Lungfish–A fish-that has lungs.
Primitive to modern amphibians
- Dendrerpeton acadianum
- Archegosaurus decheni
- Eryops megacephalus
- Amphibamus lyelli
- Doleserpeton annectens
Amphibian to reptile
Early reptile to turtle
- Odontochelys Semitestacea — partial formation of a turtle shell, showing how the hard underbelly formed first.
- Deltavjatia vjatkensis
Early reptile to diapsid (dinosaurs and modern reptiles except for turtles)
Reptile to mammal
- Protoclepsydrops haplous
- Adelobasileus cromptoni
- Morganucodon — a transition between “mammal-like reptiles” and “true mammals”.
- Steropodon galmani
- Vincelestes neuquenianus
- Pariadens kirklandi
Dinosaur to bird
- Allosaurus –A large therapod with a wishbone
- Compsognathus –A small coeleosaur with a wishbone
- Microraptor — a feathered bird with distinctly dinosaurian characteristics, such as its tail.
- Xiaotingia — slightly earlier than Archaeopteryx, slightly more like a dinosaur and less like a bird
- Archaeopteryx — the famous bird-with-teeth.
- Columba One of many typical modern birds
Transitional mammalian fossils
- Darwinius masillae — a link between earlier primates and later ones.
Non-human primate to human
- Aquatic ape hypothesis — a very controversial suggestion, aquatic apes may or may not have existed
- Australopithecus — a genus of bipedal apes
- Australopithecus sediba — advanced australopithecus showing more human features
- Homo habilis — a transitional form from Australopithecus to later Homo 
- Homo rudolfensis — a type of Homo habilis or a different species
- Homo ergaster — a form of Homo erectus or a distinct species
- Homo erectus — a transitional form from Australopithecus to later Homo (Latin for humans) species
- Homo heidelbergensis — A possible common ancestor of modern man and homo neanderthalensis  
- Homo neanderthalensis — They may or may not have done Humpy bumpy with modern humans.  
- Cro-magnon — considered early modern human and perhaps as smart as we are
- Ambulocetus— an early whale that looks like a mammalian version of a crocodile
- Indohyus — a proto-whale.
- Basilosaurus — transition from early marine whales (Indohyus) to modern whales
- Dorudon — Another candidate for transition from early whales to modern whales
- Zeuglodon — a whale-like cetacean with vestigial limbs
Transitional plant fossils
- Williamsonia — an early flowering plant (“stem angiosperm”)