Is This Four-Legged Snake a Missing Link?

The origin of snakes is a hotly debated subject in evolutionary biology. There are controversies about their phylogenetic position, their origin from aquatic vs burrowing (fossorial) ancestors, and naturally transitional fossils (Caldwell & Lee 1997, Rieppel et al. 2003, Brandley et al. 2008, Apesteguía & Zaher 2006, Lee et al. 2007, Caldwell 2007, 2008, Zaher et al. 2009, 2023, Longrich et al. 2012, Zaher & Scanferla 2012, Palci et al. 2013a, 2013b, Palci 2014, Caldwell et al. 2015, Hsiang et al. 2015, Yi & Norell 2015, Da Silva et al. 2018, Xing et al. 2018, Garbergoglio 2019a, 2019b, 2019c). While some scientists are satisfied that “snakes and mosasauroids/coniasaurs share a limbed common ancestor that was likely aquatic, not fossorial” (Caldwell 2008), different scientists strictly declare that “lizards could not have transitioned to snakes by any other evolutionary path than through fossoriality” (Da Silva et al. 2018). Either manner, there ought to have existed transitional varieties, which exhibit at the least some typical options of basal snake anatomy mixed with 4 totally developed fore and hind limbs to doc the transition of limbless snakes from nonetheless quadrupedal walking ancestors.

Assumed Mesozoic stem snakes just like the Madtsoiidae and Simoliophiidae in addition to the very primitive Cretaceous genera Coniophis, Dinilysia, and Najash did solely possess small exterior hind limbs (of which vestigial remnants are additionally retained in some residing snakes like boids), however present no proof of forelimbs (Tchernov et al. 2000, Zaher & Rieppel 2002, Rieppel et al. 2003, Apesteguía & Zaher 2006, Garberoglio et al. 2019c).

In their examine of the evolution of the snake physique plan Garberoglio et al. (2019c) commented:

This basal position of the limbed terrestrial and marine snakes signifies that snakes retain sizeable exterior hindlimbs and sacral contacts for a considerable time after their origin—from roughly 170 Ma to the youngest confirmed legged snakes, the simoliophiids, at roughly 100 Ma. This signifies that (i) the discount and lack of the pectoral girdle and forelimbs most likely occurred a lot earlier, given the definitive absence of those buildings in simoliophiids and the shortage of proof for his or her presence in Najash, Dinilysia, and madtsoiids, and was most likely a serious occasion within the early radiation of snakes, and one which occurred properly earlier than crown (fashionable) snake origins; (ii) the “forelimb-absent and hindlimb-reduced” morphology was a steady and profitable physique plan, somewhat than a transient part between limbed and limbless circumstances; and (iii) the origin of crown snakes was characterised by a serious discount within the hindlimb and pelvis (together with lack of sacral contacts).

This All Sounds Well and Good

That is, till you discover that different fashionable research (e.g., Tchernov et al. 2000, Rieppel et al. 2002, Zaher & Rieppel 2002, Longrich et al. 2012, Zaher & Scanferia 2012, Palci et al. 2013b partly, Hsiang et al. 2015, Garbergoglio et al. 2019a contra Garbergoglio et al. 2019c) don’t even agree that the fossil Madtsoniidae and Simoliophidae and even Dinilysia are stem group snakes in any respect, however recuperate them nested amongst residing snakes, which might suggest that the hind limb discount occurred greater than as soon as in crown group snake. Probably, mainstream evolutionary biologists would reply that such a discount is straightforward and due to this fact not unlikely, as is confirmed by the truth that a number of different teams of amphibians and reptilians have produced legless varieties. However, that is precisely the purpose: convergence is everywhere in the place within the animal kingdom and is nothing however incongruent similarity that contradicts a singular nested hierarchy of similarities predicted by Darwinism. Furthermore, there’s experimental evo-devo proof from transgenic mice that the discount of limbs just isn’t a easy job in any respect however requires a number of codependent mutations (evaluate Kvon et al. 2016). Together with the complicated modifications in cranium kinetics of snakes, this raises a big ready time downside, as a result of even the geologically available window of time of a number of million years is orders of magnitude too brief to accommodate the genetic modifications for this re-engineering of the physique plan, based mostly on the mathematical toolkit of mainstream inhabitants genetics.

Anyway, due to the truth that no identified fossil stem snakes had retained 4 purposeful limbs, the invention of a putative four-legged snake was an actual sensation. Eight years in the past my good colleague Prof. David Martill, with whom I co-authored a number of articles and monograph of the fossils of the Lower Cretaceous Crato Formation in Brazil (Martill et al. 2007), described from this locality the lengthy sought lacking hyperlink of snake evolution within the prestigious journal Science (Martill et al. 2015; additionally see this YouTube video): the fantastically and utterly preserved fossil reveals a really elongate snake-like animal with small fore and hind limbs, each with 5 well-developed digits. They named the 110-million-year-old fossil Tetrapodophis, which suggests four-legged snake. Their phylogenetic evaluation placed it on the very base of the snake lineage. The scientists additionally recognized burrowing diversifications that arguably would assist an origin of snakes from fossorial somewhat than aquatic ancestors. Of course, the invention was a lot celebrated in information stories as “a snake version of Archaeopteryx” (e.g., University of Portsmouth 2015, Christakou 2015a, Evans 2015, Yong 2015)

Yong (2015) commented in National Geographic:

Their evaluation produced a household tree during which Tetrapodophis got here after the earliest identified snakes like Eophis, Parviraptor, and Diablophis, however remains to be very a lot a snake. But how may that be? Eophis and the others solely have two legs, so how may four-legged Tetrapodophis have come after them? The reply is that evolution doesn’t proceed alongside easy, straight strains.

This is typical Darwinist doublespeak for the straightforward incontrovertible fact that the fossil doesn’t match inside a Darwinian situation with out advert hoc hypotheses to clarify away conflicting information. But on this case there’s one other little downside: all identified fossils of the Jurassic earliest stem snakes (Portugalophis, Eophis, Parviraptor, and Diablophis) don’t even have the physique area preserved, which might present in the event that they possessed limbs or not (see Caldwell et al. 2015), in order that the above assertion can also be incorrect. Never imagine Darwinist pop science journalists, who’re notoriously sloppy with details. But aside from this glitch, the true blows towards Tetrapodophis have been but to return.

A First Blow

The first blow got here with a really heated dialogue concerning the authorized standing of the fossil (Christakou 2015b), though there was no proof that any legal guidelines have been damaged with the export and sale of the fossil. I personally contemplate this dialogue as very a lot ridiculous, given the truth that numerous fossils from the quarries in Brazil have been grinded for cement manufacturing or used for pavements, with none native scientist caring for this pure heritage. Now, museums world wide, which invested plenty of money and preparation effort to protect these fossils for science, are actually requested to repatriate the collections to Brazilian museums with a really poor observe report of correct conservation and curation, all within the identify of defending alleged nationwide treasures of poor international locations from evil Western exploitation. Unfortunately, the pervasive woke agenda has taken maintain of paleontology as properly, which impairs scientific progress and has made fossil amassing to a really irritating endeavour.

A Second Blow

The second blow got here with one other foolish dispute concerning the deposition of the specimen. The specimen was deposited in a public museum in Germany as a mortgage by a personal collector, who briefly restricted access to the specimen as a result of it was broken through the examination with synchrotron micro-CT scanning. Even although access was later restated and the specimen was additionally meticulously documented with drawings and images within the unique publication, some scientists made absurd statements like “if the fossil can’t be studied, it doesn’t exist … I don’t want to mention the name Tetrapodophis ever again” (Gauthier quoted in Gramling 2016). Other researchers mentioned the “original paper should not have been published, because the fossil was not officially deposited in a museum or other repository”. This displays a standard politically appropriate sentiment amongst scientists towards non-public collections, though many non-public fossil collections are higher curated and extra simply accessible to scientists than public collections in sure doubtful international locations with a fame of sloppiness and corruption. Nevertheless, these bigoted scientists somewhat would go away sensational finds of excessive scientific worth undescribed eternally, than having scientific publications based mostly on materials in non-public collections. I discover this weird, scientifically reprehensible, and politically extremely problematic (anti non-public property in favor of statist forms). After all, utilizing the identical type of reasoning we may purge all paleontological data from science that’s based mostly on museum specimens that have been destroyed throughout World War II, or misplaced by the put up after they have been despatched on mortgage to international scientists, or just can’t be relocated within the museum archives anymore, which occurs far more usually than many individuals might imagine. Many scientists appear to have misplaced their widespread sense these days.

Last however Not Least

The third and really deadly blow got here with a number of research by paleontologist Michael Caldwell and his colleagues, who strongly disputed the fossorial adaptation of Tetrapodophis in favor of an aquatic adaptation, and likewise disputed the snake-affinity in favor of a dedication as dolichosaurid lizard (Lee et al. 2016, Caldwell et al. 2016, 2021, Paparella et al. 2018), which is an extinct group of marine reptiles. The press instantly reported that the large splash was a case of mistaken identification (Geggel 2016), and that the assumed lacking hyperlink between lizards and snakes has been debunked (Hodžić_2021, Lyle 2021, Strauss 2022).

One would possibly assume that this misidentification is a minor challenge as a result of dolichosaurids are sometimes thought of as shut kinfolk of snakes inside a clade Pythonomorpha. However, this opens a complete new can of worms, because the standing of Pythonomorpha is topic of appreciable scientific controversy itself. The Wikipedia article on Pythonomorpha has a superb abstract of this mess, of which the lengthy story brief is as follows: Pythonomorpha was proposed by the well-known nineteenth century paleontologist Edward Drinker Cope (1869) to incorporate mosasaurs and snakes as assumed shut kinfolk, whereas snakes have been believed to have advanced from burrowing lizards. This was rejected by most twentieth century consultants, who as an alternative instructed that the closest kinfolk of mosasaurs are monitor lizards (e.g., Russell 1967). Then, Pythonomorpha was resurrected by Michael Caldwell and Michael Lee within the late Nineteen Nineties (Caldwell & Lee 1997, Lee 1997, 1998, Caldwell 1999, Lee & Caldwell 2000) to incorporate the aquatic extinct reptile teams aigialosaurs, mosasaurs, dolichosaurs, coniasaurs, in addition to snakes, which have been postulated as derived from aquatic ancestors (additionally see Pierce & Caldwell 2004, Palci & Caldwell 2007, Caldwell 2008, Paparella et al. 2018). This was once more questioned by anatomical proof (Zaher & Rieppel 1999) and extra recent phylogenetic research, which once more placed mosasaurs with monitor lizards and snakes with skinks (Conrad 2008) or with anguinids and iguanas (Simões et al. 2020), or placed mosasaurs extra basal than monitor lizards and snakes (Gauthier et al. 2012). On the opposite hand, extra recent analyses (Palci et al. 2013a, Palci 2014, Martill et al. 2015, Reeder et al. 2015) recovered snakes and mosasaurs as sister teams and thus supported a monophyly of Pythonomorpha. The latter would even be congruent with the rising for a monophyletic group known as Toxicofera, which would come with all squamates with poison glands resembling iguanas, monitor lizards, gila monsters, and snakes, underneath exclusion of skinks, gekkos, and true lizards. However, as all the time in phylogenetics there’s additionally sturdy conflicting proof offered by opponents of the Toxicofera speculation (Hargreaves et al. 2015, Mongiardino Koch & Gauthier 2018, Joffroy 2022). If we’d draw a least widespread denominator of all revealed timber of the previous many years, the outcome could be an unresolved polytomy (as I described in a recent Fossil Friday article about arachnid phylogeny), which somewhat agrees with the expectations of creationists than these of evolutionary biologists.

A New Turn of Events

Considering this uncertainty it’s hardly a shock that this 12 months a brand new examine introduced a brand new flip of occasions and once more confirmed the standing of Tetrapodophis as most basal snake (Zaher et al. 2023). The authors remarked that “Our scorings of Tetrapodophis were based on first-hand observations of the original specimen, and our interpretations of the anatomy and attendant scoring disagree significantly with those of Caldwell et al. (2021), as do our phylogenetic results.” It doesn’t take an excessive amount of of a prophetic reward to foretell that we’ll not have to attend very lengthy for a rebuttal by Caldwell and his crew.

Whoever might finally win this dispute, there isn’t any doubt that the true cause for all this uncertainty is the straightforward incontrovertible fact that the sample of similarities between totally different animal teams doesn’t fall right into a neatly ordered set of nested hierarchies as usually pretended by hardcore Darwinists. In actuality, incongruent patterns are everywhere in the place. A snake-like physique plan is an effective instance: Among tetrapod vertebrates a snake-like physique solely originated in caecilians (Gymnophiona) amongst lissamphibians and in squamates amongst amniotes. However, inside amniotes this physique plan originated not lower than 26 occasions independently (Brandley et al. 2008, Evans 2015). Tetrapodophis could possibly be a lacking hyperlink to at the least two of them respectively, or simply could be quantity 27, who is aware of. What can also be attention-grabbing is that scientists discovered “statistically significant support for at least six examples of the re-evolution of lost digits in the forelimb and hind limb” ((Brandley et al. 2008), which reveals the extent of absurdity that’s readily accepted solely to protect the evolutionary paradigm.

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• Zaher H, Mohabey DM, Grazziotin FG & Mantilla JAW 2023. The cranium of Sanajeh indicus, a Cretaceous snake with an higher temporal bar, and the origin of ophidian wide-gaped feeding. Zoological Journal of the Linnean Society 197(3), 656–697: DOI: https://doi.org/10.1093/zoolinnean/zlac001