The Human Reptile?

Reptiles, from Nouveau Larousse Illustré, 1897-1904: Notice the inclusion of amphibians (below the crocodiles).

Reptiles, from Nouveau Larousse Illustré, 1897-1904: Notice the inclusion of amphibians (below the crocodiles).

A long time ago animals were divided into “mammals” and “reptiles” from Latin repere “to crawl, creep”.

Reptiles were the cold blooded, scaly creatures who lurked in cold water laid eggs and were basically “not nice” like fluffy furry mammals. Then along came James Cooke, the discovery of Australia and with it the Platypus an egg-lay “furry thing” to confuse the distinction as now mammals could also lay eggs.

Then recently it was realised that Birds were  closely related to dinosaurs. Even as late as 1999 when the BBC produced walking with Dinosaurs and it was still believed that dinosaurs were cold blooded so were scaly like lizards or at least free of surface “fluff”. So, the BBC have small dinosaurs with no covering at all in icy conditions looking about as warm as stuffed turkeys in the snow.

Leaellynasaura in winter forest 1999

Leaellynasaura in winter forest 1999

But a warm covering wasn’t “allowed” because Reptiles were cold blooded and therefore scaly and fluffless. They couldn’t be warm blooded or “fluffy” like “nice” hair covered mammals.

However, I’ve long been suspicious that just in other areas of academia, in the classification of species, academics are letting their own perceptions interfere with science. Mammals may be more closely related to some groups in the previous “reptile” class than to others.

Looking at Wakopedia (my name for Wikipedia as it’s far from credible after Connolley) it was connolley like asserted that there were two distinct groups of amonites (the group that includes, reptiles, mammals and birds). This group was divided into Sauropsids (reptiles and birds) and Synapsida (mammals). And furthermore:

“Sauropsida is distinguished from Synapsida, which includes mammals and their fossil ancestors.”

So, that seemed conclusive. Mammals were very distinct from the reptiles. However in the same way “CO2 caused 20th century warming” is asserted without evidence, so this emphatic assertion that mammals are distinct was asserted but details were thin on the ground. So, I read on, and the reality appears to be far more complex:

In 1956, D.M.S. Watson observed that sauropsids and synapsids diverged very early in the reptilian evolutionary history [i.e. he asserted] , and so he divided Goodrich’s Protosauria between the two groups. He also reinterpreted the Sauropsida and Theropsida [mammal like reptiles] to exclude birds and mammals respectively, making them paraphyletic, unlike Goodrich’s definition.

This is all beginning to sound very arbitrary and in particular the statement about them being two groups both descending from “amniotes” is as clear as mud:

[Synapsids – (i.e. mammals-like)] are easily separated from other amniotes [the group of Reptile+ mammals] by having a temporal fenestra, an opening low in the skull roof behind each eye, leaving a bony arch beneath each; this accounts for their name. Primitive synapsids are usually called pelycosaurs; more advanced mammal-like ones, therapsids.

The Reptiles, mammals, birds and turtles

The Reptiles, mammals, birds and turtles (source)

We have an assertion that there are two groups: Synapsids & Sauropods, both descending from Amniotes as shown as the lower groups on the diagram to the right. But the paragraph is talking about differences between the mammal-like group from its (supposed) ancestral group of Amniotes, not between the mammal like and the reptile-like group.

As written it sounds as if Amniotes are an early form of the Reptile-like group and both were distinct from the mammal-like group. It was all starting to sound a bit wishy washy and arbitrary so, I thought I’d look at some specific groups to see how they are thought to be related. Eventually I came to Turtles & Tortoises. Now here I found some controversy and controversy always highlights problems and where things just do not fit. So what is this controversy? As the drawing above shows, there is a question where turtles fit:

Their exact ancestry [of turtles] has been disputed. It was believed they are the only surviving branch of the ancient evolutionary grade Anapsida, … All anapsid skulls lack a temporal opening, while all other extant amniotes have temporal openings (although in mammals the hole has become the zygomatic arch).

So, now we seem to have two main groups:

  1. Turtles – only surviving “Anapsida” distinguished by ” skulls lack a temporal opening,”
  2. Mammals and other reptiles whose skulls have a temporal opening.

So, mammals are more closely related to crocodiles than turtles – in other words, if turtles and crocodiles are reptiles, then so are we! But reading further, it seemed I was wrong, because the DNA evidence seems to strongly contradict this:

All molecular studies have strongly upheld the placement of turtles within diapsids; some place turtles within Archosauria, or, more commonly, as a sister group to extant archosaurs. (bird-like reptiles)

That seemed conclusive: Turtles are found to be most like bird-like reptiles, butit continued.

… However, one of the most recent molecular studies, published in February 2012, suggests that turtles are most closely related to the lepidosaurs (lizards, snakes, and tuataras – i.e. reptiles unlike birds).

One group of researchers are stating turtles are in a group with bird-like reptiles, and then woosh … along comes research saying they are more closely related to the other group of reptiles which we could call the “unlike Bird Reptiles”. How can this be? As Wakopedia says:

Reanalysis of prior phylogenies suggests that they classified turtles as anapsids both because they assumed this classification (most of them were studying what sort of anapsid turtles are) and because they did not sample fossil and extant taxa broadly enough for constructing the cladogram.

So, they were found to be Anapsids (Bird-like) because the researchers only tested how close they were to other Anapsids. And they were not found to be lepidosaurs or like Lizard-like because until the last study, no one had checked. And just like the Climate, how do academics respond when it all goes wrong? They redefine the meaning of words so that they mean what they want them to say:

Gauthier, Kluge and Rowe (1988) attempted to redefine Anapsida so it would be monophyletic, defining it as the clade containing “extant turtles and all other extinct taxa that are more closely related to them than they are to other reptiles”. This definition explicitly includes turtles in Anapsida;

In other words when the facts don’t fit, just change your definition so that you redefine the group as “Turtles are in the bird-like reptiles because I say so”.

But it gets worse:

Gauthier, Kluge and Rowe (1988) themselves included only turtles and Captorhinidae in their Anapsida, while excluding the majority of anapsids in the traditional sense of the word from it. In addition, Tsuji and Müller (2009) noted that the name Anapsida implies a morphology (lack of temporal openings) that is in fact absent in the skeletons of a number of taxa traditionally included in the group. …  The presence of temporal openings in the skulls of these taxa makes it uncertain whether the ancestral reptiles had an anapsid-like skull as traditionally assumed or a synapsid-like skull instead.

So, Turtles do not really fit into either the bird-like or lizard-like groups. So what is the problem here? Why are academics jumping through hoops to try to include Turtles as part of the Bird-like reptiles? Why isn’t the evidence that they are as closely related to unlike-bird reptiles being considered?

New family tree of Reptilia

New family tree of Reptilia

Now we have this group diverging from the amphibians and the first split in this group which includes all the reptiles was between the turtles and another group of reptiles which include, crocodiles, birds, lizards, snakes, and … mammals like humans.

This I think is what is causing the academics to jump through hoops and redefine classes to include groups by definition rather than common sense:

Academics don’t like the idea of being considered “reptiles”.

In other words, for all the nonsense about the conflict between supposed “science” and “evolutionists”, it turns out that academics are just as reluctant to follow the logical evidence and put mammals in the class of reptiles as their predecessors were to put humans with apes.


Addendum

And just to show that this is a realistic proposal, I found this after I published which as I suggest shows Turtles branching off the “Reptialian” group before mammals.

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6 Responses to The Human Reptile?

  1. TinyCO2 says:

    There’s a great scene in the radio show Old Harry’s Game where the Devil is arguing with the Professor that it’s impossible to learn from the past. The Prof protests and asks ‘what about the stars. The light from stars is millions of years old and we learn from that’. ‘Okay’ says the Devil ‘Excluding stars, what can we learn from the past?’ ‘And then there’s DNA’ goes on the Prof. ‘Did you know that part of human DNA is left over from when we were prehistoric squid’. The Devil sighs. ‘Okaaaay, apart from sparkly lights in the sky and tiny bits of very old squid, what can we learn from the past?’

  2. Bolko says:

    You seem intentionally misinformed to me. You just try to fit the data in your assumption that we are reptiles. We are not. Reptiles have many synapomorphies that haven’t evolved in mammals, for example, they have a stronger type of keratin, beta keratin, on their dry skin. Mammalian skin is glandular, and in this respect it resembles amphibian skin. Synapsids urinate liquid urine with urea like amphibians, although more concentrated, while reptiles can conserve even more water by excreting uric acid. It is hypothesized that reptiles and synapsids had differing physiologies due to that, with the former more successful for dry places and the latter more tied to water.
    The anapsid is more of a descriptive term, and its use in scientific taxonomy is falling out of use. Most of the anapsids are classified in parareptiles, and some others with closer affinities to the diapsids, in the eureptiles. All of these branched after the synapsids, so they can be considered reptiles. In fact very few fossils before the branching of synapsids and reptiles exist. They would be basal amniotes.
    Turtles are, by most researchers, placed near archosaurs. Many obscure features support that, like the single penis, the egg tooth of the hatchlings, or the placement of calcium in the eggshell rather than the yolk like archosaurs, which precludes vivipary, or at least makes it very difficult.
    Ps. I found your post searching wether archosaurs were more intelligent than synapsids in the Mesozoic. I believe they were.

    • Thanks for posting. I was going to add your last paragraph to the article because it’s useful to have the evidence for an “alternative view”, however you’ve said why turtles are like crocodiles, but you haven’t explicitly said that these features are missing in early mammals (single penis??)

      On the point about reptiles – are birds reptiles?

      According to the “standard classification”, they are reptiles. So asking “are humans reptiles” becomes a valid question. The real answer is that “reptile” is not a real family of animals at all (it’s just a bucket for animals without another home). It is really a totally meaningless classification.

      But once we get beyond the meaningless concept of “reptile”, the really interesting question is whether mammals are more closely related to crocodiles than turtles are to crocodiles.

      There always tends to be a huge amount of inertia in academia – this tends to mean evidence is moulded to support the status quo.

      I didn’t see anything to cause me to reject the hypothesis that humans are more closely related to crocodiles than turtles, however, more than happy to add evidence that contradicts me.

  3. Bolko says:

    Reptile, or any other Linnaean taxonomic concept for that matter, is essencially an arbitrary concept made by humans to classify biological organisms better. The concept of clade has some more significance, because it classifies organisms based strictly on common descent, but the fact is that only the biological species concept can be thought as natural. Given that reptile is an arbitrary term, we can subsume mammals into reptiles, and later amphibians, fish etc, or the other way around, but then we wouldn’t have any real taxonomic terms. We want a working definition for reptiles, which must benarrower.
    Actually birds haven’t so many differences with reptiles, and personally I would not have any problem if I learnt that they were subsumed into reptiles. Endothermy is their main difference, but that was also possessed by many extinct groups, and some extant large reptile species with greater temperature controls blurr the lines between endotherm and ectotherm. Also crocodilians might be secondary ectotherms, as their distant ancestors’ anatomy and bone histology suggest an endothermic, or at least tachymetabolic compared to modern reptiles ancestry.
    No, archosaur and mammal penises aren’t homologous.
    http://blogs.scientificamerican.com/tetrapod-zoology/terrifying-sex-organs-of-male-turtles/
    But even if they were, that could just mean that they were lost in the squamate line and analogous structures re-evolved later. Most birds have lost them, the tuatara has greatly simplified hemipenes, and given their independent evolution they aren’t hard to evolve, so that isn’t impossible. That would not disprove their taxonomic placement, as there are tons of other characters linking archosaurs with the other diapsids.
    I am still buffled on why you insist on the possibility of mammals being more closely related to crocodiles, turtles or any other reptile. Mammals are equidistant from any other reptile, as they share a common ancestor. Thus all reptiles are more closely related to themselves than anything else.
    As for turtles, I learnt just yesterday, that an even older species, Pappochelys rosinae, has been discovered. This middle Triassic turtle was an aquatic species with a tail as long as the body, but not a true shell. It had brawdened ribs instead, and broad and in places fused gastralia, which made the plastron. But the most unexpected finding were two pairs of small temporal fenestrae on the skull, settling once and for all the debate about turtle placement in the tree of life. Turtles are diapsids. That turtle debate ended for good, as it had reached extremes, with creationists on the one side believing that they found concreat evidence for their wacky ideas, and with wacky scientists or pseudoscientists invoking even horizontal gene transfer between distantly related species in order to explain turtle uniqueness.

    • I think we both agree that “reptile” is not a group of closely related animals and excludes animals like birds (& mammals) which rightly belong in the same group.

      On whether mammals or turtles are more closely related, I wish I had the time to look at the subject more closely. All I can say is that I found a reasonable argument based on one piece of evidence that seemed to suggest mammals are more closely related than turtles.

      You’ve clearly got more information from what appears to be a wider range of evidence so I’m sure if I understood it, you have made an equally good or better argument the other way.

      However, what is far more important is that you don’t just dismiss the suggestion, which is the hallmark of the poor/disreputable “science” in climate. Instead you do seem to take it as a reasonable thing to hypothesise and offer contrary evidence.

      This tells me, that even if there were a slight bias toward one interpretation of the evidence, other interpretations would get a reasonable hearing – so long as there are people with the courage to make them in the first place!

      … however, also thanks to your comments, you’ve provided the alternative more informed view – so if anyone happens to be doing class work in this area, they will have your input which is good. However, I still would like you to make it more understandable!

  4. Bolko says:

    No, I don’t believe we agree in that. We agree that reptile is in fact an artificial term, because it contains animals based on appearance (cold-blooded, scaly etc), excluding some other groups. Only if you put mammals in reptiles you make a group with not closely-related animals, if you leave birds inside you have a group of quite closely related animals.
    I believe that science corrects itself in light of new discoveries. Especially in such fields like archaeology, paleontology or astronomy, where the object of study is in the past and the evidence often fragmentary, theories and descriptions of events change, even radically sometimes, when a new piece of evidence is found to complete the picture. Of course there are here dogmatic people and others arguing due to personal issues, but the same happens to other fields as well. Humans are not perfect. Quite a few times phylogenetic trees have changed, and that is not indicative of faulty methodology if indeed new evidence has been found. Moreover, I don’t think that there is much incentive to alter data here. After all, scant grants go towards such studies, because exactly there is no much economic benefit from their results. Believe me, no one will care if we are technically mammals, reptiles or molluscs. Humanity has many other pressing problems. On the other hand, huge interests are at stake when it comes to climate research. Its results about so called global warming do and will influence global politics, the fossil fuel market, the sustainability market, and thus the economy at large. You have any reason to be too skeptic of their results, and I have any reason to be too skeptic of their results. Especially after reading Michael Crichton’s book State of Fear, I have become even more skeptic of climate science. The events described there aren’t too far from reality. For that reason, I would never equate climate research with cladistics or paleontology.
    As for the branching events, these do not deserve of much skepticism, because they are well-known. If anapsids branched before mammals and turtles were a part of them, then turtles would be something different, and mammals would be more closely related to other reptiles. But neither fossil nor molecular evidence agrees with that. The so called anapsids is a defunct group now, and no fossils of them are found before the mammals branched off. Also turtles are diapsids, long-known from molecular studies, and recently confirmed by fossil findings. With these information in mind, the branching order is as follows:
    First, before approximately 320 million years ago, there were the stem amniotes. These were small, lizard like animals with features of amphibians and more terrestrial species. We do not know for sure which fossils were true amniotes and which their immediate progenitors, because we don’t have any fossilized amniotic egg. Fossils of that age are few and fragmentary, because they were small animals. Then, a few million of years after that, the mammalian line branched off. It had a pair of temporal fenestrae affording more space for the jaw muscles, but in other respects, the first synapsids weren’t much different from basal amniotes. Only a little later they started loosing ancestral features like ventral dermal bony plates and palatal dentition. They possessed glandular skin like that of amphibians.
    Not much time after the divergence of synapsids, some basal amniotes evolved into reptiles, which branched into two lines, the parareptiles and the eureptiles. All the parareptiles and some eureptiles were classified as anapsids in the past, but the fact is that some of these anapsids evolved independently a temporal fenestra or a noch in the bones there for the same purpose. At the end of the carboniferous, not long after the divergence of those groups, within the eureptiles there evolved the diapsids, which had two pairs of temporal fenestrae. These contain the modern reptiles. At the end of the Permian both of the main lines which would play a large role in future reptile evolution were distinct. The lepidosauromorphs and the archosauromorphs. The lepidosauromorphs gave rise to the large marine reptiles, the tuataras, lizards and snakes, as well as to many other extinct clades. The archosauromorphs gave rise to turtles, many other extinct clades and archosaurs proper, which contain crocodilians, pterosaurs, dinosaurs and birds, as well as other, less-known extinct clades.
    Meanwhile the synapsids were evolving into various clades, one of which were the true mammals. I doubt that their ancestors would be classified as reptiles if there were living today. Early on they had taken the compact mammalian body form, with the short, thin tail and a semi-erect gate. They probably had good control over body temperature and cared for the eggs or young. But even the earlier, more lizard-like forms would most probably not be classified as reptiles due to absence of scales, and if the hypothesis that they layed very soft eggs and cared for them is true, they would be more mammal-like in human consciousness. But neither pterosaurs, dinosaurs or most land crocodilians would be classified as reptiles if found living today, because they were too different, and most probably warm-blooded. It seems, from all of that, that reptile was a descriptive term at first, which later only was taken by taxonomy. Don’t forget that in the past amphibians, insects, and some small mammals were put in that creeping reptile category.

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