New fossil proves turtle evolution … or does it?
One of the most challenging examples of evolution for its proponents is that of turtles. This is because turtles have a comparatively good fossil record, which shows that even the first claimed turtle is unequivocally a turtle. A review of the newest claims for evidence of turtle evolution, including Pappochelys, found that major problems exist with all of the examples reviewed. Rather than confirming evolution the newest fossils do more to reinforce the conclusion that the extant fossil record shows no clear evidence for turtles arising from non-turtle ancestors as postulated by evolutionists.
Turtles are ideal animals for testing the validity of evolution.1 A major reason is that their hard shells are well-preserved in the fossil record.2 “Because of their thick bony shells and their compact heavy skulls, turtle remains can survive exposure to the elements much better than” almost any other animal.3 Once “turtles are present in a fauna, their carapaces, or fragments thereof, stand a reasonably good chance to fossilize.”4
Evolutionists date turtle fossils back into the Triassic, evolutionists estimate 220 million years ago, and all turtle fossils, thus far discovered, are clearly turtles.5 Even the earliest known turtle, the Jurassic turtle called Kayentachelys, possessed a “carapace with all of the modern, morphological features of modern, fully aquatic species.”6 Because the “body plan of turtles is unique among tetrapods”, Darwinists believe turtles are ideal animals for evolutionary studies. Furthermore, “remarkable changes in [both] the skeleton and internal organs” were required to evolve turtles from non-turtles.7
The Odontochelys fossil
In 2008, Chun Li and colleagues described a new fossil turtle having unusual features. They named it Odontochelys semitestacea, meaning ‘toothed turtle with a half-shell’. The turtle was found in Chinese ocean sedimentary rock that was dated about the same age as one of the oldest known true turtles, Proganochelys. Odontochelys’ abdomen was protected but it lacked a carapace. The authors’ theory was that turtles evolved their shell piecemeal, the bottom half first.8 Instead of a carapace, Odontochelys possessed only broadened ribs, which one theory speculates eventually coalesced to form larger bony plates (figure 1).9 The many problems with this theory include:
“How do bones that form in the skin fuse with underlying ribs that normally grow into the lateral body wall? And why is it that uniquely in turtles the shoulder blade lies inside the ribcage, instead of being located outside the ribcage as in all other tetrapods?”10
In addition: “Fusion of osteoderms with the underlying ribs would explain how the ribs became incorporated in the carapace”.10 Another issue was that the 40-centimetre-long creature Odontochelys lacked a beak and had a mouthful of well-developed teeth in both its upper and lower jaws in contrast to all known turtles, tortoises and terrapins which instead lack teeth and have powerful horny beaks. This is why “some experts say the fossils raise more questions than they answer … is Odontochelys emblematic of early turtles—or just an oddity? Paleontologists will need to dig up more ancient turtles to find out”.11 The presence of teeth in Odontochelys and lack of a horny beak is evidence that it was a reptile unrelated to turtles.
Yet another problem with the evolutionist claim that Odontochelys “was clearly a stage between turtles as we know them and their more ancient ancestors”12 is that it is the only evidence of an animal with broadened ribs. In contrast, all known turtles have a fully developed carapace. No evidence exists for the gradual evolution of broadened ribs or something even close to a carapace and plastron. Ironically, Professor Hans-Dieter Sues, Department of Paleobiology, National Museum of Natural History, in Washington D.C. claims from this sparse and problematic evidence that “The origin and early evolution of the turtle body plan has become one of the best-documented examples of an evolutionary transition in the fossil record”.12
The Eunotosaurus claim
Another proposed pre-turtle was Eunotosaurus (Latin for stout-backed lizard). It was a typical lizard except that its ribs were wide and flat, forming broad plates.13 This feature likely was needed to support its very broad and fat body, and was not a precursor of a turtle.
In support of this position, anatomical studies and phylogenetic analyses suggest that Eunotosaurus was a para-reptile, an animal that existed at the same time as modern turtles, and not a basal turtle, basal meaning the animal that gave rise to modern turtles.14 When “compared with the newly discovered early turtles”, Eunotosaurus was soon judged as “an important part of the turtle’s transformation”.
“All these fossils”, Black claims, “add up to a reasonably clear picture of how the turtle got its shell”, namely “lizard-like reptiles such as Eunotosaurus were digging into the ground for food or shelter.”12 Then, those pre-turtles “with broader ribs would have been more efficient diggers, and this conferred an advantage that was passed down” to its progeny.12 Exactly how broader ribs made them more efficient diggers is not stated. Effective digging is primarily dependent on muscle development and paw and claw structure, not broader ribs.
Turtle ancestors, evolutionists speculate, must have “evolved an abdomen shell, perhaps to protect and stabilise their internal organs from the stresses of digging.”12 This improvement would have also been very helpful for other digging animals. Riley Black speculates that the carapace evolved when “bits of bone began to form along the skin of their backs, creating a more enclosed carapace” and “motions required for digging are similar to those that turtles use to swim”.12 This “pre-adapted turtles to be competent swimmers when that evolutionary niche became available.”12 Black admits that turtle shell evolution is still very debatable:
“… there is still debate about whether the top half of the shell evolved before or after turtles began swimming. Increasingly shelled-in turtles would have had protection from attack while suspended in the water, but it is unclear whether that was a reason they took to a life aquatic or rather a downstream effect of that move.
“Part of the reason we don’t have firm answers here is that there are tens of millions of years between Eunotosaurus, Odontochelys, and Proganochelys, and we don’t know what came in between. We also know little about the role of extinction events. … Yet we have only the wispiest grasp of how and why turtles survived such cataclysmic times.”12
Black neglected to mention the major internal organ and structural changes required to evolve a terrestrial animal into a largely aquatic animal like a turtle.
Pappochelys: the newest claimed example of an intermediate turtle
Currently, the fossil record does not provide evidence of turtle shell evolution. However, several new examples of potential pre-turtles, claimed by evolutionists, will now be evaluated. Gilbert and his associates have proposed a theoretical embryological model involving movement of the ribs into the dermal layer that is believed to have led, millions of years later, to the evolution of the turtle shell.15 This modelling, although useful, cannot replace the requirement for paleontological evidence.16 More fossils and more research has only resulted in biologists telling “dueling stories of how turtles got their shells”.17
After admitting that “For years, the oldest turtle fossils we could find had fully formed shells”, the authors of one new discovery claimed that “more primitive fossils are revealing the strange tale of how turtle shells evolved”.18 What they found, a reptile called Pappochelys (meaning grandfather turtle), is nothing like a turtle (figure 2). The claim is based on a large number of small bone fragments meticulously assembled by the paleontologists. From these fragments, the researchers concluded that the Pappochelys fossil could fit in the palm of a human hand and grow up to eight inches long. It had a tail comprising about half of its length and used its tiny, peg-like teeth to feed on small insects and worms.
This very non-turtle was speculated to be “a key missing link in the evolutionary history of turtles”.19 It had neither a carapace nor plastron, but rather the evolutionists speculated that the plastron may have formed by evolution through serial fusion of the gastralia, bones protecting the ventral area of vertebrates.20 The authors admit “it is difficult to provide a definitive vertebral count for Pappochelys based on disarticulated and sometimes disassociated material”.21 Furthermore, the reconstruction illustrations of the gastralia and the plastron effectively show the major differences between the two.22 Schoch and Sues also speculate that “the plastron may have first developed as protection and ‘bone ballast’ for controlling buoyancy” in a water environment.23 Pappochelys had a few unique traits; it
“… resembles Odontochelys in various features of the limb girdles. Unlike Odontochelys, it has a cuirass of robust paired gastralia in place of a plastron. … Its skull has small upper and ventrally open lower temporal fenestrae, supporting the hypothesis of diapsid affinities of turtles”.27
All of the many very different kinds of turtles have one thing in common, which Pappochelys also possesses, namely
“… modifications required to live inside this box of bone. Their upper ribs are fused to the inside of their shell and their shoulder joints are set inside their ribs. This anatomical form is unprecedented among vertebrates. Imagine how your arms would move—or rather wouldn’t—if your shoulders were inside your ribcage. ‘It is the shell and associated features, such as the position of the limb girdles inside it, that makes turtles so unusual … [see figure 3].’”24
Furthermore, Pappochelys had a pair of openings located behind the eye socket on each side of the skull which exists both in lizards and crocodilians, but not in turtles:
“Look at the back of almost any other reptile skull—whether it is a gecko or a Tyrannosaurus rex—and you will see a pair of openings for jaw muscle attachments. Turtle skulls, with their toothless beaks, don’t have these holes, making them an oddity that lacks a clear connection to any other group of reptiles.”25
The fact is, “The early evolution of turtles continues to be a contentious issue in vertebrate paleontology.”26 Thus, “scientists who study the evolution of these animals have a running joke: turtles might as well have come from space.”27
Changes required to evolve a turtle from another reptile
Major changes would be required for a non-turtle reptile to evolve into a turtle, with its unique shell and other features. As will be explained, none of the claims made for ‘transitional forms’ even begin to bridge this gap. The origin of the turtle shell, which “contains over 50 dermal bones found in no other vertebrate order”,28 is still a major problem for evolution.29 The most radical (but not the only) change required to evolve a turtle from a non-turtle is the evolution of the shell. The shell is a box-like structure firmly fused with the turtle’s backbone and ribs. The top shell, the carapace, and the lower shell, the plastron, are connected by a lateral bridge-like wall on both sides.
These bony shell plates are covered with keratin, the tough substance found in claws, hair, fingernails, and horns, which protects the shell and reduces water loss.30 The shell design suggests “daring architectural design with innovative engineering.”31 Although the main function of the turtle shell is protection, it also serves as a reservoir for water, fat, and wastes and also functions as an effective pH buffer.31
Another required change concerns the scapulae (‘shoulder blades’), which in other vertebrates are located outside of the rib cage, except in turtles, where they are located inside the rib cage (along with the humerus and several other bones).32 The primitive-reptile turtles are theorized to have evolved from a reptile with three to five cervical vertebrae and, in contrast, turtles have eight. The turtle skull is also very different from that of other reptiles.33 Turtle skeletal structure is so very different from all other tetrapods that “turtle origins are difficult to resolve without evidence [of these changes] in the fossil record.”34
Depending on the turtle type, the dermal layer of the shell generally has a total of 60 bones. The carapace is composed of about 38 paired and 12 unpaired bones, and the plastron has eight paired bones and one unpaired bone. The shell’s epidermal layer is made up of 38 keratinized sections, called scutes, in the carapace and 16 in the plastron.35 The evolution of the turtle would thus also require the formation of several score new structures besides the shell, including much of the turtle‘s bony skeleton.36 The tetrapod body plan requires not only extensive modification to evolve into a turtle, but also dramatic physiological changes. For example, because the turtle chest is not distensible, the turtle respiratory system is designed very differently from that of all other reptiles.37
For these reasons, the “turtle shell represents a classic evolutionary problem: the appearance of a major structural adaptation.”38
One hypothesis developed to solve the evolution of turtles problem is the theory that the turtle carapace gradually evolved from “elements of the primitive reptilian integument”.39 Systematist and reptile expert Olivier Rieppel stated that a big “problem for an evolutionary biologist is to explain these transformations in the context of a gradualistic process.”40 Rieppel concludes that turtles could not have evolved by any gradual process, so they must be an example of ‘hopeful monsters’, a result of major mutations that cause very rapid evolution called punctuated equilibrium.41 In short:
“The origin and early evolution of turtles have long been major contentious issues in vertebrate zoology. This is due to conflicting character evidence from molecules and morphology and a lack of transitional fossils from the critical time interval.”42
All of these and hundreds more changes are required for a turtle to evolve from a non-turtle. Proganochelys was, and still is, the most primitive known turtle which “was unquestionably a turtle, from its spiky shell to the arrangement of its shoulders and lack of holes in the rear of its skull.”25 This turtle obviously “wasn’t much help to those trying to figure out how turtles evolved.”19
A huge chasm exists between turtles and their proposed reptilian ancestors. The latest claims of evolutionary links totally fail to bridge this large gap. The origin of turtles remains one of the most problematic claims of evolution and all efforts to fill the gap have failed.
References and notes
- Bergman, J. and Frair, W., Evidence for turtle evolution? J. Creation 21(3):24–26, 2007. Return to text.
- Lee, M.S.Y., The origin of the turtle body plan: bridging a famous morphological gap, Science 261(5129):1716–1720, 1993. Return to text.
- Flank Jr, L., The Turtle: An owner’s guide to a happy, healthy pet, Howell Book House, New York, p. 20, 1997. Return to text.
- Rieppel, O. and Reisz, R.R., The origin and early evolution of turtles, Annual Review of Ecology and Systematics 30:1–22, 1999; p. 17. Return to text.
- Spotila, J.R., Sea Turtles: A complete guide to their biology, behavior, and conservation, The Johns Hopkins University Press, Baltimore, MD, p. 57, 2004. Return to text.
- Pritchard, P., Evolution phylogeny and current status; in: Lutz, P.L. and Musick, J.A. (Eds.), The Biology of Sea Turtles, CRC Press, New York, p. 2, 1996. Return to text.
- Burke, A.C., The development and evolution of the turtle body plan: inferring intrinsic aspects of the evolutionary process from experimental embryology, American Zoologist 31(4):616–627, 1991; p. 616; Burke, A.C., Development of the turtle carapace: implications for the evolution of a novel bauplan, J. Morphology 199(3):363–378, 1989; and Bellairs, A.d’A., Reptiles: Life history, evolution, and structure, Harper Torchbooks/Harper and Brothers, New York, p. 63. 1960. Return to text.
- Black, R., How the turtle got its shell: evolutionary puzzle finally cracked, New Scientist, May 2–8 2020, pp. 37, 39. Return to text.
- Li, C. et al., An ancestral turtle from the Late Triassic of southwestern China, Nature 456(7221):497–501, 2008. Return to text.
- Rieppel, O., How did the turtle get its shell? Science 325(5937):154–155, 2009. Return to text.
- Stokstad, E., Sea Change for Turtle Origins? sciencemag.org/news/2008/11/ sea-change-turtle-origins, 26 November 2008. Return to text.
- Black, ref. 8, p 39. Return to text.
- Cox, C.B., The problematic Permian reptile Eunotosaurus, Bulletin of the British Museum of Natural History 18:167–196, 1969. Return to text.
- Benton, M.J., The Chinese Pareiasaurs, Zoological J. Linnean Society 177 (4):813–853, 2016. Return to text.
- Cebra-Thomas, J. et al., How the turtle forms its shell: a paracrine hypothesis of carapace formation, Molecular Development and Evolution 304(6):558–569, 2005. Return to text.
- Nagashima, H., Kuratani, S. et al., Turtle–chicken chimera: an experimental approach to understanding evolutionary innovation in the turtle, Developmental Dynamics 232:149–161, 2004. Return to text.
- Lubick, N., Biologists tell dueling stories of how turtles get their shells, Science 341:329, 2013. Return to text.
- Black, ref. 8, pp. 36–39. Return to text.
- Key Link in Turtle Evolution discovered. Mentioned four times. Smithsonian Insider, insider.si.edu/2015/06/key-link-in-turtle-evolution-discovered/. Return to text.
- Schoch, R.R. and Sues, H.D., A Middle Triassic stem-turtle and the evolution of the turtle body plan, Nature 523 (7562):584–587, 2015; p. 584. Return to text.
- Chun, L. et. al., A Triassic stem turtle with an edentulous beak, Nature 560:476–479, 2018; Chun, L. et al., An ancestral turtle from the Late Triassic of southwestern China, Nature 456(7221):497–501, 2008; p. 478. Return to text.
- Schoch and Sues, ref. 20, p. 586. Return to text.
- Schoch and Sues, ref. 20, p. 587. Return to text.
- Black, ref. 8, 2020. p. 36–37. Return to text.
- Black, ref. 8, 2020. p. 37. Return to text.
- Li, C., Fraser, N.C., Rieppel, O., and Wu, X.C., A Triassic stem turtle with an edentulous beak, Nature 560:476–479, 2018. Return to text.
- Black, ref. 8, p. 36. Return to text.
- Gilbert, S.F., Loredo, G.A., Brukman, A., and Burke, A.C., Morphogenesis of the turtle shell: the development of a novel structure in tetrapod evolution, Embryology and Development 3(2):47–58, 2001; p. 47. Return to text.
- Gilbert et al., ref. 28, pp. 47–48. Return to text.
- Van Damme, J. and Aerts, P., Kinematics and functional morphology of aquatic feeding in Australian snake-necked turtles (Pleurodira; chelonian), J. Morphology 233:113–125, 1997. Return to text.
- Willis, D., Explorations: prehistoric encounter, Omni, June 1982, p. 132. Return to text.
- Rieppel, O., Turtles as hopeful monsters, BioEssays 23(11):987–991, 2001; p. 990, 2001. Return to text.
- Lee, M., Turtles; in: Singer, R. (Ed.), Encyclopedia of Paleontology, vol. 2, Fitzroy Dearborn Publishers, Chicago, IL, pp. 1297, 1999. Return to text.
- Gaffney, E. and Kitching, J.W., The most ancient African turtle, Nature 369:55, 1994. Return to text.
- Gilbert et al., ref. 28, p. 48. Return to text.
- Lee, M.S.Y., The homologies and early evolution of shoulder girdle in turtles, Proceedings: Biological Sciences 263(1366):111–117, 1996. Return to text.
- Bellairs, ref. 7, p. 66. Return to text.
- Gilbert et al., ref. 28, p. 56. Return to text.
- Burke, ref. 7, 1989, p. 363. Return to text.
- Rieppel, ref. 32, p. 990. Return to text.
- Rieppel, ref. 32, p. 987. Return to text.
- Schoch, R.R. and Hans-Dieter, S., A Middle Triassic stem-turtle and the evolution of the turtle body plan, Nature 523 (7562):584–587, 2015. Return to text.