Losing a Missing Link: What is its Significance?

The fossil of Tetrapodophis. Note its small size and tiny bones. Image from Caldwell et al. (2021) (see notes 2 and 5 below for full citation).

In 2015, a new fossil creature, Tetrapodophis, was named and described. “Tetrapodophis” literally means, “four-legged snake” (“tetra” means four, “poda” means leg, and “ophis” means snake), which is exactly what this animal was described as: a four-legged snake. As it was classified close to the base of Ophidia, the group that contains the snakes, it was thought to represent a basal form of snake, shedding light on how snakes evolved from lizards.[1] 

This year, a study came out that challenged that assessment of Tetrapodophis. A re-examination of the skeleton determined that it is actually a dolichosaur, rather than a snake.[2] Now, a dolichosaur is a long bodied type of lizard. Dolichosaurs belong to the same group as the more familiar mosasaurs. Together with a third group, the aigialosaurs, the dolichosaurs and mosasaurs form a group called Mosasauria.

What are we to make of this turn around? Tetrapodophis used to be thought of as a transitional fossil, but now it has been reclassified away into a different group. That means that a gap now exists between lizards and snakes, and that evolutionists have no explanation for how snakes evolved from lizards, right?

Well, not quite. For one thing, snakes and Mosasauria belong together in one large group called Pythonomorpha.[3] While Tetrapodophis is certainly no longer considered a basal snake, it didn’t move that far on the “tree of life.” In other words, reclassifying Tetrapodophis as a dolichosaur was less of a “complete re-evaluation” as it was refining its classification. Second, there are still other snakes that have limbs and are considered to be close to the base of the snake group.[4] Granted, these snakes have only a pair of limbs, rather than two like Tetrapodophis, but there is barely a gap left in the latter’s absence. Third, and most importantly, evolutionists do not live and die by the fossil record. They consider cladograms, statistically created “trees of life”, to be more significant in determining relationships between animals than fossil are. After all, cladograms are based on available data from animal morphology while the fossil record may be missing things. Basically, they simply admit that the fossil record is incomplete. As was discussed in a previous post on this blog, the fossil record is incomplete, so it is kind of hard to fault them for not having fossils of every single creature that ever existed.

It may be tempting to think that Tetrapodophis was originally identified as a four-legged snake because evolutionists “needed” a transitional snake, so the first thing that looked like a transitional snake got plugged into that role, regardless of how well it actually fit. Then, more level-headed scientists eventually came along and performed “real science” to determine what Tetrapodophis actually was. Rather than being a contrast between “quick tempered” evolutionists and “level-headed” scientists, the reason Tetrapodophis was re-evaluated was simply because of good scientific scrutiny: a hypothesis, that Tetrapodophis was a four-legged snake, was proposed and, like all hypotheses, it needed to be tested. The reason for the delay between the original description (2015) and subsequent re-evaluation (2021) was because of legal and ethical issues regarding ownership and availability of the fossil.[5] In other words, no one was dragging their feet because Tetrapodophis was “too good to fail.” It was genuinely difficult to get access to study the fossil.

I might also add that the Tetrapodophis fossil does not look like it is easy to interpret. First of all, the fossil itself is surprisingly small. Second, the skull, which often carries several diagnostic characteristics, is crushed, leaving much to interpretation. See the illustration at the beginning of this article and the illustration below to see what I am talking about. In other words, I do not think that Tetrapodophis was identified as a snake because “evolutionists saw what they wanted to see,” but that it is a genuinely difficult fossil to interpret.

The skull of Tetrapodophis. As you can see, this is something that would be difficult to interpret. The black bar int he bottom left is 1 mm long. Image from Caldwell et al. (2021) (see notes 2 and 5 below for full citation).

If the reclassification of Tetrapodophis does not leave a sizable gap in the evolutionary record, if the presence of a gap does not kill the theory of evolution, and if evolutionists are not fudging the data to make it fit their theory, then what good is it to know that Tetrapodophis has been reclassified? It is good to know because it reminds us that human knowledge is limited. Why was Tetrapodophis reclassified? Because finite people studying a single fossil and comparing it to a finitely known group of animals had to re-evaluate the original interpretation. That is why scientific discoveries are always subject to revision: a new interpretation can come along or new information may be found that forces us to re-evaluate what we once thought was correct.

Science being something that is constantly up for revision is not a problem in and of itself. However, if one’s worldview is supposed to be based entirely on science, then it can cause problems. Science, being something that is constantly subject to revision, will always leave our knowledge with an air of uncertainty. Evolutionists, who want to understand the world using science alone, without any input from outside sources of knowledge (such as God), are thus putting themselves in a position where nothing that they know can be known for certain. In other words, their entire worldview is shaky simply because of the changing nature of science. They have to trust, without proof, that every time science corrects itself, it gets closer to reality. Unfortunately, for them, this is not something that can be objectively proven.We, on the other hand, have the Word of God as our standard, and as long as we continue to return to that standard and evaluate our knowledge in light of that standard, we will be able to get our science back on track, as it were.

Thoughts from Steven

[1]Martill, David; Helmut Tischlingerl; Nicholas Longrich (2015) “A four-legged snake from the Early Cretaceous of Gondwana” Science 349(6246): 416-419

[2]Caldwell, Michael; Tiago Simoes; Alessandro Palci; Fernando Garberoglio; Robert Reisz; Michael Lee; Randall Nydam (2021) “Tetrapodophis amplectus is not a snake: re-assessment of the osteology, phylogeny and funtional morphology of an Early Cretaceous dolichosaurid lizard” Journal of Systematic Palaeontology DOI: 10.1080/14772019.2021.1983044

[3]According to evolutionists, anyway.

[4]Palci, Alessandro; Michael Caldwell; Randall Nydam (2013) “Reevaluation of the anatomy of the Cenomanian (Upper Cretaceous) hind-limbed marine fossil snakes Pachyrhachis, Haasiophis, and EupodophisJournal of Vertebrate Paleontology 33(6): 1328-1342

[5]Caldwell, Michael; Tiago Simoes; Alessandro Palci; Fernando Garberoglio; Robert Reisz; Michael Lee; Randall Nydam (2021) “Tetrapodophis amplectus is not a snake: re-assessment of the osteology, phylogeny and funtional morphology of an Early Cretaceous dolichosaurid lizard” Journal of Systematic Palaeontology DOI: 10.1080/14772019.2021.1983044

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