Monotreme Fossil Record Still Baffles Evolutionists

The platypus and echidna were
already hard for evolutionists
to explain. New discoveries
make the problem worse.

 

 

by Jerry Bergman, PhD

One of my main interests is the fossil record of animals. I have reviewed almost every major type of animal. Although no definitive evolutionary claims are made for most animal kinds, at least some possibilities, sometimes reasonable possibilities, do exist.[1] The lack of evidence for evolution in the fossil record has been a major problem since Darwin proposed his evolution theory. He admitted that “Geology assuredly does not reveal any such finely graduated organic chain; and this, perhaps, is the most obvious and gravest objection which can be urged against my theory.”[2] This concern is still a major problem for evolution.

A good example of zero evidence for evolution can be found in the fossil record of monotremes. Monotremes are a unique group of mammals characterized by their egg-laying reproductive system.

The most well-known monotreme is the duck billed platypus. One reason it is difficult to find clear evidence for monotreme evolution in the fossil record is because monotremes are distinct in so many ways that they don’t fit neatly into any group. The platypus has traits typical of mammals, birds, and reptiles. It has a bill like a duck, a flat tail like a beaver, a reptile-like skeleton, a comparatively large forefeet for a 3.5-pound animal, and a streamlined body that allows it to rapidly maneuver like a fish in its watery world. These features forced taxonomists to invent an entirely new classification for the platypus, namely the monotreme.

Mammals feed their young milk, as do monotreme mothers, so they are mammals. However, unlike all other mammals that give birth to live young, monotremes lay eggs like birds. Complicating matters further, male monotremes can deliver poisonous venom—much like snakes—with a potency strong enough to kill smaller animals such as dogs. Monotremes also exhibit skeletal features that resemble reptiles.[3] Remarkably, the platypus—unlike mammals—uses electroreception, the ability to detect electrical signals to locate its prey. Besides the Guiana dolphin, no other mammal exhibits this trait. Given their unique blend of mammalian, reptilian, and avian characteristics, the question is raised, “where should we search for their evolutionary ancestors?” Among mammal-like creatures? Avian ancestors? Reptilian predecessors? Or perhaps somewhere totally different?”

The Other Monotreme: Echidnas

The echidna—a spiny anteater-like animal—because it is more similar to the platypus than to any other living mammal, is also classified as a monotreme. Echidnas are small terrestrial mammals characterized by coarse hair and sharp dorsal spines resembling juvenile porcupines. Echidnas share several key mammalian traits: they are warm-blooded, have dense body hair, produce milk via mammary glands to nourish their young, and possess three middle-ear bones, as do humans. Its long, thin, narrow bill looks very much like a hummingbird beak.Although they do not look at all like a bird,  they lay eggs like a bird.

These odd-looking creatures are designed to consume termites, ants, insect larvae, and even worms. When threatened, they curl into a small ball with their sharp spines extending outward to protect themselves. Or they might partly bury themselves in dirt, using their spines to shield their body. Their present distribution is largely limited to Australia and New Guinea.

Unraveling the fossil record of monotremes thus far has been challenging for many reasons:

Monotremes are one of the strangest and rarest mammalian groups we have today. From spiked echidnas, to platypuses with bills, monotremes have an array of seemingly bizarre adaptations such as electroreception, egg-laying reproduction (oviparity), and milk field lactation…. This combination of odd morphologies, low taxonomic diversity, and narrow geographic distribution makes the origin and evolution of monotremes intriguing questions.[4]

The Monotreme Fossil Record

Department of Biology Professor Megan Whitney of Loyola University in Chicago detailed the problem of monotreme evolution. She observed that, in comparison to most other animals, the sparseness of the monotreme fossil record is a common theme in evolution textbooks:

Open any vertebrate paleontology or evolutionary morphology textbook and there will undoubtedly be a plethora of details on the evolution of marsupial and placental mammals. By comparison, there are usually only one or two paragraphs on monotremes, at most. While fossil monotremes display a greater range of morphological variation than what is represented today, their fossil record is very much incomplete, especially in comparison to their placental and marsupial relatives. As a result, monotreme evolution has remained a hotly debated scientific inquiry—especially for questions surrounding the taxonomic affinity of certain key fossils and the ancestral adaptations of monotremes.[5]

Kryoryctes Promises Much But Deliverers Little

The paper by Megan Whitney, published in the Proceedings of the National Academy of Sciences (PNAS), is titled “Updated fossil analyses reveal critical insights into the origins of monotreme lifestyles.” It promised much but delivered little insight for understanding monotreme evolutionary origins.

Enter Kryoryctes, a putative prehistoric monotreme mammal from the early Cretaceous, of which the only evidence is a partial right humerus (arm bone) discovered by Professor Phillips. Phillips is at the Center for Macroevolution and Macroecology, Research School of Biology at Australian National University, Canberra, Australia. He wrote:

The fossil record has provided few clues as to their origins and the evolution of their ecological specializations” Kryoryctes is the only evidence now existing to document monotreme evolution even though bone’s microstructure is “only similar to modern platypuses.” [6]

He then admits to the following difficulties using this fossil to understand monotreme evolution:

In addition to challenges surrounding the taxonomic affinity of [a fossil arm known as] Kryoryctes, the sparse fossil record documenting monotreme evolution results in lingering questions surrounding the ancestral adaptations of the group. This question is further complicated by the extremely divergent adaptations apparent in our modern monotreme representatives. Did echidnas evolve from a platypus-like ancestral condition? Or is terrestriality ancestral for monotremes? Based on the morphology of fossil monotremes such as Teinolophos, Monotrematum, and Sternopodon, the prevailing body plan and lifestyle appears to be more similar to a platypus. However, the remarkably similar humeral morphology between Kryoryctes and echidnas has generated an alternative hypothesis that the ancestral condition may have been more terrestrial and echidna-like.[7]

Kryoryctes is currently known only from a single humerus. The speculation from this bone includes a claim that early monotremes were semiaquatic burrowers. This basis for the claim it was adapted for life in the water comes from an observation that its dense bone tissue could be used for ballast. This discovery challenges the long-held belief that monotremes originated on land. It also requires rearranging the story for the other monotremes, the echidnas. Now, they say, echidnas may have evolved from semiaquatic ancestors, then evolved into a terrestrial animal.

The Missing Common Ancestor

Evolutionists claim that this single fossil bone, discovered over 20 years ago, “clearly continues to provide unparalleled insight into evolutionary history.” In this case, the evolutionists concluded that the Kryoryctes cadburyi‘s humerus bone suggests that the echidna’s ancestors were semi-aquatic burrowers, similar to modern platypuses. Thus, the common ancestor of both echidnas and platypuses is now assumed by evolutionists to have adapted to a life both in and out of the water. Then, echidnas later supposedly evolved to be primarily terrestrial, which, scientists admit, is a rare evolutionary adaptation in mammals.[9] The research team wrote:

Up until now, the accepted understanding about these egg-laying monotremes – arguably the most unusual mammals on the planet – was that they were both descended from a land-bound ancestor. And while the platypus ancestors became semiaquatic, the echidnas stayed on the land, or so the story went. But following a UNSW-led analysis of the bone – which was discovered by a team from Museums Victoria – it now looks like echidnas and platypuses evolved from a water-dwelling ancestor…. there are about 30 instances where mammals evolved from land-dwelling to live wholly or partly in water, for example, whales, dolphins, dugongs, seals, walruses, otters, and beavers. But it’s virtually unheard of to see mammals evolve in the opposite direction.[10]

While this conclusion may be true, it is itself a problem for evolution. The history of paleontology demonstrates that drawing conclusions from a single fossil bone—like the Kryoryctes humerus—can be profoundly misleading. The claim that, as some concluded from the Kryoryctes fossil, different mammals including whales, dolphins, dugongs, seals, walruses, otters, and beavers, all must have evolved from land-dwelling animals into animals living wholly or partly in water.[11] This adds another layer of evolutionary complexity, further reducing the probability of evolution.

Likewise, any evolutionist interpreting the Kryoryctes  humerus bone, would have had a priori beliefs that evolution had occurred. As a result, the researchers would interpret the data in light of that belief, even though the actual evidence for it was very sparse. The papers reviewed above rely on a single small humerus bone, which may have belonged to an extinct creature entirely unrelated to the platypus or its presumed evolutionary lineage. In spite of this, with very minimal evidence, a whole new scenario for the evolution of monotremes was proposed.

Summary

This is yet another example of  “how one fossil can serve as a critical dataset in reconstructing evolution”, despite offering only minimal data. The problem is, belief in evolution causes one to see in a fossil evidence that requires a far more complex evolutionary journey. It must have evolved to live in the water, then this bias leads investigators to misinterpret the data as supporting a new evolutionary history, even though it actually introduces additional complexity and requires further, unexplained evolutionary steps to account for the modern organism.

References

[1] Bergman, Jerry, Fossil Forensics: Separating Fact from Fantasy in Paleontology. Bartlett Publishing, Tulsa, OK, 2019.

[2] Darwin, Charles. The Origin of Species. London.  John Murry. 1859.  p. 280.

[3] Pettigrew, John D., “Electroreception in monotremes,”  The Journal of Experimental Biology 202 (Part 10): 1447–1454, 1999.

[4] Whitney, Megan. “Updated fossil analyses reveal critical insights into the origins of monotreme lifestyles,” Proceedings of the National Academy of Science 122(23):1, 2025.

[5] Whitney, 2025.

[6] Phillips, Matthew, “Molecules, morphology, and ecology indicate a recent, amphibious ancestry for echidnas,” Proceedings of the National Academy of Science 106(40):17089-17094, 2025.

[7] Whitney, 2025.

[8] Hand, Suzanne J., et al., “Bone microstructure supports a Mesozoic origin for a semiaquatic
burrowing lifestyle in monotremes (Mammalia),” Proceedings of the National Academy of Science  122(19):1-19, https://www.pnas.org/doi/10.1073/pnas.2413569122, 28 April 2025.

[9] University of New South Wales, “‘Extremely rare event’: Bone analysis suggests ancient echidnas lived in water,” https://www.eurekalert.org/news-releases/1081536, 28 April 2025.

[10] University of New South Wales, 2025.  

[11] Bergman, Jerry “Whale Evolution: A Whale of a Tale.” Creation Research Society Quarterly. 49(2): 122-134, Fall 2012.

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Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,900 publications in 14 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.