The fossil “transitional form” is not what reporters are making it out to be.
It’s 8 inches long, and it was in a German museum on display as an “unknown fossil” when David Martill (U of Portsmouth) noticed it with his students. It looks like a snake with four tiny feet, complete with 5 digits on each foot. What is it? Martill is convinced he has found a missing link between walking reptiles and snakes. With two colleagues, he published his analysis in Science Magazine, “A four-legged snake from the Early Cretaceous of Gondwana,” and gave it the name Tetrapodophis amplectus, “four-footed embracing snake.” Once the artwork was ready, the press went to work writing dramatic headlines:
- Four-legged fossil snake is a world first (Nature)
- Four-legged snake fossil found (Science Daily)
- Four-legged fossil suggests snakes evolved from burrowing ancestors (PhysOrg)
- Four-legged snake ancestor ‘dug burrows’ (BBC News)
- Four-legged fossil holds secret of snake’s slithering origins (New Scientist)
- Unexpected Step: Snake Ancestor Had Four Feet (Live Science)
- Photos: Weird 4-Legged Snake Was Transitional Creature (Live Science)
- Snakes’ four-legged missing link (Science Magazine)
Deeper reading shows problems with the “missing link” interpretation:
- It’s not that unusual. Other fossil snakes with hind legs are known. Susan Evans lists other fossil in Science Magazine, “The largest set consists of several related marine snakes from the Middle East, North Africa, and southern Europe. These fossil snakes have 140 to 155 precaudal vertebrae and a short tail. They show no trace of forelimbs or shoulder girdle but do have small hindlimbs; only one [Haasiophis preserves digits. The relationships of these limbed marine snakes remain controversial, but many analyses nest them among modern snakes, rather than nearer the base of the snake evolutionary tree.”
- The fossil overturns theories that snakes evolved in the sea: “That debate is a long-running one among palaeontologists, and researchers say wiggle room is running out for the idea that snakes developed from marine reptiles” (BBC News).
- Evolutionists claim that the slithering mobility lifestyle evolved many times—another case of “convergent evolution.” Evans says, “This implies either that hindlimbs were reduced more than once within snakes, or that the limbs redeveloped in some lineages.” Sid Perkins quotes her in his article “Four-legged snake stuns scientists, and invites controversy” in Science Magazine: “a radical elongation of the body and reduction in size or loss of limbs has occurred many times in other groups of reptiles, she notes.” Susan Evans’ write up in Science Magazine, “Four Legs Too Many?”, has a diagram of unrelated reptiles that “evolved” a narrow, slithering lifestyle.
- The provenance of the fossil is unclear. It came from a private collection before being purchased and exhibited in the Solnhofen Museum in Germany. Supposedly it came from Brazil decades ago, but when and where it was found is not known.
- Paleontologists are not claiming the legs and feet are vestigial. They were apparently used for either grasping, climbing, or burrowing. “It’s pretty straight-up adapted for burrowing,” co-author Nick Longrich (U of Bath) says (BBC News). Caldwell thinks the limbs “are remarkably unusual unless you’re a tree-climber.” Perkins writes that the digits “appear to have been functional.”
- Not every paleontologist is convinced this is a snake at all. Michael Caldwell of the U of Edmonton in Alberta says, “In particular, the front surfaces of the vertebrae of known snakes and lizards except geckoes are concave, and the rear surfaces are convex; that doesn’t appear to be the case in Tetrapodophis, he says.” Caldwell thinks it might be an amphibian: “its vertebrae resemble those seen among a large group of extinct amphibians that died out during mass extinctions about 251 million years ago, long before Tetrapodophis appeared on the scene.” That interpretation would mean that Tetrapodopohis was a remnant of the group that survived over a hundred million years longer (in the evolutionary timeline). Perkins quotes Susan Evans: “I’m trying to carefully sit on the fence as to whether this is actually a snake.” In the New Scientist article, Caldwell is emphatic: “I honestly do not think the fossil represents the remains of a snake.” Calling it a “four-footed snake” does not make it one, even in Latin.
- The fossil is so clear that “Details of the bones are clearly visible and impressions of soft tissues such as scales and the trachea are preserved,” Science Daily says.
- If this fossil were labeled a missing link to snakes, how did snakes get to all the other parts of the world?
- Since no other fossils of this species have ever been located, one cannot say it is not a mutant form.
- Snake evolution is mysterious. Evans writes, “The combined efforts of paleontology and developmental biology have gone some way toward unraveling the early history of snakes, but many questions remain as to their origins, relationships, character evolution, and ancestral lifestyle. Resolution of these questions depends, ultimately, on the recovery of further fossils and their thorough and objective analysis.”
The number of vertebrae are controlled by Hox genes (developmental switches). Evans writes, “In all vertebrate embryos, individual vertebrae develop from segments (somites) that form at regular intervals. To increase vertebral numbers, somite formation must either continue for longer or occur at a faster rate. Snakes use both strategies. Individual vertebrae then acquire positional identity along the body axis through the overlapping expression domains of Hox genes. In a typical tetrapod, the boundaries between major vertebral regions (such as the neck and the trunk) coincide with Hox gene expression boundaries.” Gene switches can also suppress the development of limbs. If limbs “reappear” in a limbless vertebrate that evolutionists consider “younger” than an ancestor that lacks limbs, it doesn’t mean that limbs evolved de novo; rather, the information for limbs was never lost.
Unquestionably, this is a beautiful fossil with snake-like features and well-preserved limbs. It has 160 body vertebrae and 112 tail vertebrae, within the range of snake traits. Stomach contents show it had some vertebrate animal for its last meal. Photos of the fossil are shown by Live Science. Caldwell expresses his reservations about its identity this way: “I think this creature is far more exciting for what it might be than for what [the team] says it is.”
Update 7/30/15: AiG has an article about worm lizards (see also 4/27/15) that slither like snakes but are members of the lizard family that burrow underground, like this fossil apparently did. Some worm lizards have limbs and some don’t. For other problems with snake evolution, see “On the Origin of Snakes” here, 12/06/13.
Update 10/28/16: “A transitional form debunked” shouts a headline on PhysOrg. The fossils is not a snake at all, but a swimming reptile in the group dolichosaurid, which falls under the squamate (scaly reptile) umbrella, concludes Michael Caldwell (U of Alberta) after re-examining the only fossil of this finger-sized species. Live Science is asking whether it a case of “mistaken identity” as the “debate heats up” over what it represents.
Other Reptile News
Eggshell surprise: In other reptile news, the “oldest lizard embryos” were found preserved in fossil eggs in Thailand, PhysOrg reports. The creature is being called an anguimorph, neither dinosaur nor lizard, and is dated near the same time as the four-footed snake. “‘The discovery of anguimorphs in hard-shelled eggs comes as a considerable surprise,’ said the statement—and recast the evolution of lizard reproduction. ‘So far, only geckos were known to lay hard-shell eggs.'”
Horned lizard design: In a “delightful example of biomimetics,” a physics trick by the common “horny toad” (horned lizard) has been imitated in the lab, reports the BBC News. The spines on the back of the creature aren’t just for protection; they funnel water to the lizard’s mouth in its dry desert climate. A grad student at Aachen University noticed “You can apply the water to the back, to their front, to the tail… and it’s always transported fastest towards the mouth.” An intricate system of channels or capillaries creates directional fluid motion. When the lizard opens and closes its mouth, it may be pumping the water toward its mouth. Two principles are at work: “We have the narrowing of the single capillary channels on the one hand, and we have the capillary network and its interconnections on the other hand,” the article explains. “These are the two underlying principles that we found to establish this directional transport.” The researchers were able to imitate these effects in the lab. The “sophisticated” skin of the horned lizard was referred to as a “design” half a dozen times.
If you’re a creationist tempted to think that Tetrapodophis represents something out of Genesis 3, don’t go there. The fossil records an animal that was alive at the time of the Flood, possibly thousands of years later than Eden. We know that the present world is impoverished of many well-designed creatures that existed in the antediluvian world. Suffice it to say this is one of them. Some antediluvian birds had teeth and claws on their wings; the living hoatzin still has the claws, but not the teeth. It shouldn’t be surprising that some long, slithering reptiles, whether snakes, legless lizards or amphibians also had limbs or the genetic information for them. In some, that information is present but not expressed (blind cave fish are an example). Limbs are designed. This creature had limbs and digits adapted for its needs. If anything, the limbs were “devolving” not evolving; no new genetic information was emerging from scratch.
It sounds so much like a skink, I wonder how it can be so summarily added to snake fossils. If the girdle’s intact there is no need to deny its skinkhood.