No Transitional Fossils?

Published by Drew Stedman on December 8, 2009 at 9:56am UTC

I was recently presented with a challenge from my former Christian high school biology teacher who is a young earth creationist:

“I still don’t know about the “thousands of transitional species” that you referred to in the fossil record. I will look forward to you pointing those out to me.”

This was a challenge I was more than happy to accept as the evidence from the fossil record unequivocally supports evolution. In response to this list, which took some time to put together, I received a power point presentation of Bible verses about creation. I thought this was ironic because I had just finished rereading the book of Genesis. It was also very telling, because it so clearly shows that in order to believe in creationism, one must completely ignore evidence and rely entirely on blind faith in scripture. Evidence as we shall see, is the enemy of Creationism. Which is why Creationists do not accept evidence.

I hope those of you who are interested in this topic will find this resource useful when being confronted with the statement “There are no transitional fossils”

For the purpose of clarity, I will define transitional fossils as: The fossilized remains of intermediary forms of life that illustrate an evolutionary transition (Wikipedia).

I must emphasize that transitional fossils are those that exhibit a transitional feature. “The transition itself can only be illustrated and corroborated by transitional fossils, but it will never demonstrate an exact half-way point between clearly divergent forms.” (Wikipedia) Because of our understanding of geology and the specific conditions required for the formation of a fossil, we would not expect to have a perfect, or “complete” fossil record. However, upon careful examination of the record, the evidence of a clear and branching pattern of divergence can be observed in the transitional features of taxa. This evidence becomes increasingly overwhelming the more one studies the fossil record as is seen throughout many of the scientific papers referenced in the list below.

Before reviewing this list I find it important to note that ALL of these examples appear in the fossil record in the correct strata and periods predicted by the evolutionary tree of life. This is most extremely exhibited in the case of Tiktaalik. Tiktaalik was discovered because of these predictions, which led Neil Shubin and his colleagues to Ellesmere Island in Nunavut, Canada where they found the fossil in the precise layer of rock they expected to.

Also, the trees of life constructed from the fossil record are identical to those independently constructed from genetics, anatomy, embryology, molecular biology etc. This adds serious weight to the validity of the fossil record.

In this list I have included references for each example in relevant peer-reviewed scientific papers along with a link to each article (or article listing) when possible, as well as relevant news articles. I have also included a link to the Wikipedia entry for each example. This is a very streamlined list of transitional fossils which doesn’t include the much more recent ancestry of humans. We will get to that soon.

Note: (Some of the preliminary information I used to compile this list came from online posts by DonExodus, a biologist whose education includes: BS Evolutionary Biology- UNC-Charlotte. Doctoral- UNC. I used some information from his videos, Transitional Fossils I and II: I did my own research in finding more information and peer-reviewed papers about each example. As part of this I spoke with Kevin de Queiroz, Research Zoologist at the Department of Vertebrate Zoology Division of Amphibians & Reptiles at the Smithsonian National Museum of Natural History who provided me with information on the transitional taxa and stem reptiles which mark the transition between amphibians and reptiles in the fossil record. A site that he directed me to is helpful and relevant to this entire list:


The following two articles are relevant to the information found in this list.

Heterochronical patterns of evolution in the transitional stages of vertebrate classes.

Schad W.

Acta Biotheor. 1993 Dec;41(4):383-9.

Extreme convergence in the body plans of an early suchian (Archosauria) and ornithomimid dinosaurs (Theropoda).

Nesbitt SJ, Norell MA.

Proc Biol Sci. 2006 May 7;273(1590):1045-8.


Eusthenopteron – an example of the beginning of the formation of characteristics only found in tetrapods: Internal nostrils, Labyrinthodont teeth, two part cranium, Intracranial joint, the development of arm and leg bones (humerus, ulna, radius, femur etc.)

Related paper:

Terrestrial-style feeding in a very early aquatic tetrapod is supported by evidence from experimental analysis of suture morphology.

Markey MJ, Marshall CR.

Proc Natl Acad Sci U S A. 2007 Apr 24;104(17):7134-8. Epub 2007 Apr 16.

Panderichthys – development of large tetrapod head, pelvic girdle to support developing limbs, a breathing tube on the top of head.

Related paper:

The pelvic fin and girdle of Panderichthys and the origin of tetrapod locomotion.

Boisvert CA.

Nature. 2005 Dec 22;438(7071):1145-7.

Gogonasus – “the most complete, acid-prepared Devonian tetrapodomorph fish yet discovered.” “shares several features with that of Tiktaalik”

Related paper:

An exceptional Devonian fish from Australia sheds light on tetrapod origins.

Long JA, Young GC, Holland T, Senden TJ, Fitzgerald EM.

Nature. 2006 Nov 9;444(7116):199-202. Epub 2006 Oct 18

Tiktaalik – Well-preserved fossils were found in 2004 on Ellesmere Island in Nunavut, Canada. (Wikipedia). Had fish scales, fish gills, tetrapod rib bones, mobile neck and lungs. Fins with basic wrist bones and fingers that were weight bearing. These are clearly traits that are in development.

Related papers:

The cranial endoskeleton of Tiktaalik roseae.

Downs JP, Daeschler EB, Jenkins FA Jr, Shubin NH.

Nature. 2008 Oct 16;455(7215):925-9.

The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb.

Shubin NH, Daeschler EB, Jenkins FA Jr.

Nature. 2006 Apr 6;440(7085):747-9.

Ichthyostega – New bones in pelvic girldle (pubis, ischia, ilia), Rib cage and sternum, still had fish lateral line system, gills and finned tail.

Related paper:

Contrasting developmental trajectories in the earliest known tetrapod forelimbs.

Callier V, Clack JA, Ahlberg PE.

Science. 2009 Apr 17;324(5925):364-7.

Temnospondyli – Eryops and Cacops, Branchiosaurus

Related paper:

The armoured dissorophid Cacops from the Early Permian of Oklahoma and the exploitation of the terrestrial realm by amphibians.

Reisz RR, Schoch RR, Anderson JS.

Naturwissenschaften. 2009 Jul;96(7):789-96. Epub 2009 Apr 4.


Anthracosauria – Ancestral line to reptiles. Ex. Diadectes

Cheirolepis, Osteolepis, Ichthyostega, Pholidogaster, Pteroplax.


For information about the transition between amphibians to reptiles I consulted Kevin de Queiroz – Research Zoologist Department of Vertebrate Zoology Division of Amphibians & Reptiles Smithsonian National Museum of Natural History. He directed me to Seymouria as well as several other stem reptiles that can be found on

Seymouria – Labyrinthodont skull and teeth with reptilian vertebrae, pelvis, humerus and digits; amphibian ankle. (See first article)

Related papers:

Early tetrapod relationships revisited.

Ruta M, Coates MI, Quicke DL.

Biol Rev Camb Philos Soc. 2003 May;78(2):251-345.


Jozef Klembara, David S. Berman, Amy C. Henrici, Andrej Čerňanský, Ralf Werneburg, and Thomas Martens

Annals of Carnegie Museum 76(1):53-72. 2007

Hylonomus and Limnoscelis – slightly amphibian skull with reptilian skeleton.

Related papers:

Discussion on ecology of earliest reptiles inferred from basal Pennsylvanian trackways

David G. Keighley, John H. Carder, Adrian F. Park, Ronald K. Pickerill, John W.F. Waldron, Howard J. Falcon-Lang and Mike J. Benton

Journal, Vol. 164, 2007,1113-1118

Microsaurs and the Origin of Captorhinomorph Reptiles

Joseph T. Gregory Dept. of Paleontology, University of California Berkeley

American Zoologist 1965 5(2):277-286; doi:10.1093/icb/5.2.277


Pelycosaur Synapsids – ex. Ophiacodon, Varanopidae, Ophiacodontidae. Intermediate between cotylosaurs and therapsids.

Related papers:

Fossil Synapsids: The Ecology and Biology of Mammal-like Reptiles.

Kemp TS.

Science. 1987 May 15;236(4803):862-863

The mammary gland and its origin during synapsid evolution.

Oftedal OT.

J Mammary Gland Biol Neoplasia. 2002 Jul;7(3):225-52.

Therapsids – ex. Dimetrodon – Many therapsid fossils show gradual intermediate changes from reptilian to mammalian features: Ribs become restricted to chest instead of entire body, legs are not spread out but pulled in.

Related papers:

Evolution of bone microanatomy of the tetrapod tibia and its use in palaeobiological inference.

Kriloff A, Germain D, Canoville A, Vincent P, Sache M, Laurin M.

J Evol Biol. 2008 May;21(3):807-26. Epub 2008 Feb 25.

Post-Jurassic mammal-like reptile from the Palaeocene.

Fox RC, Youzwyshyn GP, Krause DW.

Nature. 1992 Jul 16;358(6383):233-5.

Cynodont theriodonts – ex. Cynognathus – Very mammal-like reptiles. Differentiated teeth, differentiated vertebral column, mammalian limbs and digits, has undeniably reptilian jaw joint.

Related papers:

Buyle-Bodin Y, Dubreuil D.

J Biol Buccale. 1976 Jun;4(2):91-108.

Cynodont reptile with incipient mammalian jaw articulation.

Romer AS.

Science. 1969 Nov 14;166(907):881-2.

Tsubamoto T.

Clin Calcium. 2005 Jun;15(6):1045-8.

Tritylodont theriodonts – ex. Tritylodon – even more mammal characteristics but still has reptilian jaw joint.

Related paper:


Ailin Sun and Yuhe Li

Vertebrata PalAsiatica Volume XXIII, No.2 April, 1985 pp. 135-150

Examples of transition b/w reptilian inner ear and jaw to mammalian inner ear and jaw:

Ictidosaur theriodonts – ex. Pachygenelus (formerly known as Diarthrognathus) – has all mammalian features of tritilodonts and has double jaw joint, both the reptilian jaw joint and the mammalian jaw joint side by side in the skull.

Related papers:

An Ictidosaur Fossil from North America.

Chatterjee S.

Science. 1983 Jun 10;220(4602):1151-1153

The dentitions of the Tritheledontidae (therapsida: cynodontia)

Gow CE.

Proc R Soc Lond B Biol Sci. 1980 Jul 17;208(1173):461-81.

Morganucodonts – ex. Morganucodon – Same double jaw joint but with the MAMMALIAN JOINT DOMINANT with reptilian joint moving inward

Related paper:

Mammal Teeth from the Forest Marble (Middle Jurassic) of Oxfordshire, England.

Freeman EF.

Science. 1976 Dec 3;194(4269):1053-1055.

Eupantotheres – ex. Amphiperatherium – Mammals begin to show complex molar cusp patterns. Has mammalian jaw joint.

Related papers:

Crystallite orientation discontinuities and the evolution of mammalian enamel–or, when is a prism?

Lester KS, von Koenigswald W.

Scanning Microsc. 1989 Jun;3(2):645-62; discussion 663

Mammal Teeth from the Forest Marble (Middle Jurassic) of Oxfordshire, England.

Freeman EF.

Science. 1976 Dec 3;194(4269):1053-1055.

An example of the transition between egg-laying reptiles and placental mammals is the Platypus which is warm-blooded, has fur, produces milk but lays eggs instead of having live young. Some parts of their skeleton are more similar to a reptile than to a mammal. EX. Obdurodon – Extinct platypus that had molar teeth.

Related article:

Platypus Genome Reveals Secrets of Mammal Evolution

Scott Norris for National Geographic News May 7, 2008

Related paper:

New information about the skull and dentary of the Miocene platypus Obdurodon dicksoni, and a discussion of ornithorhynchid relationships.

Musser AM, Archer M.

Philos Trans R Soc Lond B Biol Sci. 1998 Jul 29;353(1372):1063-79.


Anchiornis huxleyi – New feathered Dinosaur just discovered in China in the past few weeks. Has “dino fuzz” and four limbs with wing-like characteristics which also found in later specimens such as Arhaeopteryx.

Related article:

Archaeopteryx – has many avian characteristics such as feathers but also some that are only found in reptiles such as: has no bill, trunk region vertebra are not fused as in all birds, pubic shafts with slightly angled cross-section, neck attaches to skull from rear as in dinosaurs not from below like birds. Claws on 3 non-fused digits a feature that no adult bird has. The sacrum occupies 6 vertebra (birds always have 11-23) along with many other traits.

Related paper:

A well-preserved Archaeopteryx specimen with theropod features.

Mayr G, Pohl B, Peters DS.

Science. 2005 Dec 2;310(5753):1483-6.

More on Archaeopteryx:

From Answers in Genesis:

“One of the biggest dilemmas for those who want to believe that dinosaurs evolved into birds is that the so-called feathered dinosaurs found thus far are dated to be about 20 million years more recent than Archaeopteryx. This is a problem for evolution because Archaeopteryx is now generally recognized to be a true bird.”

I must note that this argument, while it has been thoroughly refuted is further weakened by the very recent discovery of Anchiornis huxleyi, which pre-dates Archaeopteryx. Also, Archaeopteryx is NOT widely recognized as a true bird. It is widely recognized as a transitional form between reptiles and birds, it could in fact be more accurate to describe it as a “true reptile” rather than a true bird because it actually has more reptilian characteristics than avian ones.

An article from UC Berkeley:

I have also heard a similar argument that uses this quote from Dr. Alan Fedduccia: “Paleontologists have tried to turn Archaeopteryx into an earth-bound, feathered dinosaur. But it’s not. It is a bird, a perching bird. And no amount of ‘paleobabble’ is going to change that.”

While Fedduccia believes that Archaeopteryx is fully a bird, he is in the minority in that regard. This is a classic case of quote mining in a weak attempt to overlook that the fossil clearly has both reptilian and avian traits.

Dr. Fedduccia also said of Archaeopteryx:

“…The creature thus memorialized was Archaeopteryx lithographica, and, though indisputably birdlike, it could with equal truth be called reptilian…. The Archaeopteryx fossil is, in fact, the most superb example of a specimen perfectly intermediate between two higher groups of living organisms–what has come to be called a “missing link,” a Rosetta stone of evolution….”

Sinornis santensis – Bird traits: short trunk, claws on toes, stronger flight-feather bones, short hand. Reptilian traits: Reptilian stomach ribs, non-fused hand bones, pelvis, teeth and tail.

Related paper:

Early Evolution of Avian Flight and Perching: New Evidence from the Lower Cretaceous of China.

Sereno PC, Chenggang R.

Science. 1992 Feb 14;255(5046):845-848.

Las Hoyas Birds – Reptilian pelvis and legs, bird-like shoulder. Transistions between Archaeopteryx and modern birds.

Related paper:

The birds from Las Hoyas.

Sanz JL, Ortega F.

Sci Prog. 2002;85(Pt 2):113-30.

An additional note: Chicken bills can be induced to form teeth because they still have dormant genes for making teeth. Why would they have genes for making teeth if not for a toothed ancestor?

Articles about teeth in birds:


Should see transition between ears that are designed to hear on land and those that are designed for the water.

Pakicetus – Distinct whale skull, but with nostrils on tip of snout. Ears which are partially modified for hearing under water.

Related paper:

Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls.

Thewissen JG, Williams EM, Roe LJ, Hussain ST.

Nature. 2001 Sep 20;413(6853):277-81

Ambulocetus natans – A whale with four legs. Stubby front legs with well developed back legs and large feet that stick out like tail flukes.

Related paper:

“Ambulocetus natans, an Eocene cetacean (Mammalia) from Pakistan”

J. G. M. Thewissen, S. I. Madar, and S. T. Hussain

Courier Forschungsinstitut Senckenberg (1996) 191: 1–86.

Related article:

Rodhocetus – hind legs which were shorter than A. natans. Could probably waddle on land but with powerful tail. Nostrils moved back from tip of snout.

Related paper:

Origin of whales from early artiodactyls: hands and feet of Eocene Protocetidae from Pakistan.

Gingerich PD, Haq Mu, Zalmout IS, Khan IH, Malkani MS.

Science. 2001 Sep 21;293(5538):2239-42. Epub 2001 Sep 19.

Basilosaurus isis – Whale with legs but hind feet had 3 toes and small remnant of 2nd toe.

Related paper:

Hind Limbs of Eocene Basilosaurus: Evidence of Feet in Whales.

Gingerich PD, Smith BH, Simons EL.

Science. 1990 Jul 13;249(4965):154-157.

Prozeuglodon – Very tiny hind legs, had vestigal 6 inch legs at rear of 15 foot body. Whale-like skull with dorsal nostrils.

Related paper:

Replacement of Deciduous First Premolars and Dental Eruption in Archaeocete Whales

Mark D. Uhen

Journal of Mammalogy 81(1):123-133. 2000 doi: 10.1644/1545-1542(2000)081


These fossils hold extra weight because of the fact that sometimes whales and dolphins are born with intact feet, which sometimes even have toes.

Related papers:

Limbs in whales and limblessness in other vertebrates: mechanisms of evolutionary and developmental transformation and loss.

Bejder L, Hall BK.

Evol Dev. 2002 Nov-Dec;4(6):445-58.

On the development of Cetacean extremities: I. Hind limb rudimentation in the Spotted dolphin (Stenella attenuata).

Sedmera D, Misek I, Klima M.

Eur J Morphol. 1997 Feb;35(1):25-30.

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