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Thursday, 22 October 2015

The Spinosaurus saga continues

A year after the 'Spinosaurus reboot' as a small-legged, early whale-mimicking aquatic quadruped, experts remain divided over fundamental aspects of Spinosaurus palaeobiology. This depiction shows Spinosaurus aegyptiacus as generally imagined prior to 2014.

The long, tragic and occasionally controversial research history of the giant, enigmatic theropod Spinosaurus aegyptiacus will be familiar to many readers of this blog*. First named and described in the early 20th century by Ernst Stromer from remains found in Late Cretaceous strata of Egypt, our principle Spinosaurus material fell victim to Allied bombing raids in World War II and was completely destroyed. Stromer's detailed illustrations and descriptions are all that remains of this material, and these have formed a variably interpreted foundation of all subsequent Spinosaurus research. For much of the 20th century the life appearance of Spinosaurus remained mysterious. Depicted as a nondescript sailed giant theropod early on, discovery of well represented spinosaurids like Baryonyx and Suchomimus, as well as fragments of new Spinosaurus material, permitted more confident interpretations of Spinosaurus size and form as we approached the new millennium. By the 2010s, Spinosaurus was recognised as a gigantic, derived and perhaps semi-aquatic spinosaurid, adapted for feeding on large aquatic prey (above). Much of this interpretation relied on new Spinosaurus remains from multiple locations in northern Africa, including the famous Moroccan Kem Kem Beds, an expanse of Late Cretaceous rocks roughly contemporaneous with those Egyptian deposits yielding the original, destroyed Spinosaurus remains.

*For succinct overviews of Spinosaurus research prior to 2014, check out posts at Tetrapod Zoology and Laelaps.

Famously, last year saw Spinosaurus reinvented again, this time as a quadrupedal, knuckle-walking, long-bodied, tiny-legged dinosaurian take on a crocodile or early whale (below). The authors of this widely publicised study, Nizar Ibrahim and colleagues (2014), synthesised existing and new data on African spinosaurids to create this reconstruction, synonymising several taxa into S. aegyptiacus and presenting new Spinosaurus remains obtained from the Kem Kem beds. The most significant of these was a set of associated vertebrae, pelvic and hindlimb remains which were proposed as a neotype specimen for Spinosaurus (a specimen to hold the Spinosaurus name now that the original material is lost to science). That this neotype represents Spinosaurus was bolstered by it bearing similar hindlimb and vertebral proportions to 'Spinosaurus B', a collection of Egyptian spinosaurid specimens described by Stromer, considered referable to Sp. aegyptiacus by Ibrahim and colleagues. Spinosaurus B is also now lost, also being destroyed in WWII. The Ibrahim et al. study provided a lot of new data on Spinosaurus and has helped cement the concept of it being a semi-aquatic animal, but several aspects of the paper didn't meet the warmest reception from a number of academics. Specific issues were scaling of the skeletal components, how sensible it was to lump so much north African spinosaurid material into one species, and uncertainty about the provenance of the neotype specimen. Some of these concerns were diffused by the authors, but we await a promised monograph for answers to all the questions raised by their first paper. In the mean time, the 2014 Spinosaurus interpretation remains a debated topic among those interested in dinosaur palaeontology.

The Ibrahim et al. (2014) take on Spinosaurus aegyptiacus. Different colours represent different specimens: red is the neotype; brown is the original Spinosaurus material; yellow is referred, isolated Spinosaurus remains; green bones are borrowed from other spinosaurids, and blue bones are crafted to fit the skeleton based on neighbouring elements. Image borrowed from Smithsonian.com.

One year later...

This week, the Spinosaurus tale has taken another twist with publication of a mammoth (open access) paper penned by a team of European spinosaurid experts, led by Serjoscha Evers. Evers et al. have reappraised the affinities of Moroccan specimens seemingly related to Spinosaurus: Sigilmassasaurus brevicollis and Spinosaurus maroccanus. These animals, known only from vertebrae, were subsumed into Sp. aegyptiacus by Ibrahim et al. (2014) as part of their trans-African Spinosaurus concept, and that decision is a core focus of the Evers et al. paper. Their work contains extensive commentary on the detailed anatomy of Moroccan spinosaur material and what it might mean for recent interpretations of Spinosaurus form and lifestyle. Given the wide interest in Spinosaurus and the 2014 reconstruction, I thought it might be of interest to summarise some of what they outline here.

Firstly, taxonomic revisions proposed by Evers et al. present a very different picture of what fossils we can identify as belonging to Spinosaurus. Their work on Si. brevicollis and Sp. maroccanus suggests these species are probably one and the same (the latter being sunk into the former), and that Sigilmassasaurus should be considered distinct from Sp. aegyptiacus. They go on to suggest that other Kem Kem vertebrae hint at a second spinosaurid species in the Kem Kem fauna, and outline several reasons why the Ibrahim et al. 'neotype' specimen cannot be referred to Spinosaurus. For one, the neotype is anatomically quite different from Stromer's Egyptian 'Spinosaurus B' specimen. Ibrahim et al. considered Spinosaurus B as representing Sp. aegyptiacus, but Evers and colleagues argue that Spinosaurus B is anatomically more similar to Sigilmassasaurus than Spinosaurus. Spinosaurus B therefore might have no use for linking any specimens specifically to Sp. aegyptiacus, including that all-important neotype.

In addition to these morphological objections, Evers et al, also raise palaeobiogeographic issues with the 'neotype' referral. Evidence for Egyptian dinosaur species being present in Morocco is scant at best, most data indicating little mixing of eastern and western African dinosaur species during the Late Cretaceous. It would be unusual, then, to find the Egyptian species Sp. aegyptiacus in Morocco. Palaeobiogeography is not a deal clincher for taxonomy of course - careful examination of the neotype and genuine Spinosaurus remains will be the deciding factor here - but it is another stick in the mud for the neotype proposal. Although the exact identity of the 'neotype' specimen is left in the air by Evers et al. - ongoing descriptive work on the specimen needs to be completed to truly assess this - they reject the proposal of the Kem Kem specimen as a Sp. aegyptiacus neotype, and leave Spinosaurus characterised by features in Stromer's illustrations. This is obviously quite a shake up of the suggestions made last year: Spinosaurus 2014 might be a mix of at least two named species, incorporate material of under-appreciated taxonomic importance, and substantial, newly published material might have little, if anything, to do with Spinosaurus.

The proposed Spinosaurus neotype. Image borrowed from Andrea Cau's excellent Theropoda blog.

Moving on, Evers et al. also raise concerns about interpretations of Spinosaurus in context of Kem Kem fossil collecting practises. Museum exhibitions and PR exercises suggest that the Kem Kem yields complete skeletons of dinosaurs and other fossil vertebrates, but the reality is quite the opposite. Kem Kem vertebrates are typically preserved as isolated, often broken bones in multitaxic bone beds (that is, bone beds comprising many species). Associated skeletons of single individuals do occur, but they're relatively rare and rely on precise collecting documentation to prove their authenticity. Unfortunately, historic and recent records of Spinosaurus occurrences and excavation are often poor. We might chalk a lack of historic documentation to the practises and technological limitations of bygone times, but recent issues are caused primarily by the commercial value of Kem Kem fossils. The greater majority of Kem Kem fossils, including dinosaurs, are collected without extensive documentation and then sold by private dealers. Even if localities are recorded, ambiguity often surrounds association of fossil material prior to excavation. Several alleged associated Spinosaurus specimens are meant to have come from single localities, but being from the same place is really only half the battle if they stemmed from multitaxic assemblages. Concordant size of bones might suggest genuine association, but this is not always certain either: Evers et al. report practises where collectors sort loose material from disparate locations into type and size categories before sale - nefarious individuals making fossil skeletons more substantial with unassociated elements is a real problem the world over. It's sad but true that the monetary value associated with substantial vertebrate fossils makes ascertaining their authenticity crucial for subsequent credible interpretation.

Unfortunately, Evers et al. report these factors as affecting virtually all associated Spinosaurus material, including the 'neotype' and the other specimen key to the 2014 reconstruction, Spinosaurus B. In the case of the latter, all we have to go on to establish association are Stromer's notes, which are not quite as detailed as we might like. For the neotype, we know some of the specimen was directly collected in the field, and that other bits were purchased from dealers by two academic institutions over a two year period - exact documentation of this remains to be presented (hopefully it will in the 'neotype' monograph). Without strict certainty over how many individuals these specimens might represent, Evers et al. suggest some of the odd proportions in recent Spinosaurus reconstructions may reflect the marrying of mismatched bones to one another. That's not a certainty, of course, but it's also something which shouldn't be casually ignored.

Collectively, Evers et al. use these points to provide an alternative take on Spinosaurus to that presented in 2014. Ibrahim et al. argued that their new material helped simplify and integrate different interpretations of African spinosaurid material, but Evers et al. argue the opposite: they emphasise how poorly known Spinosaurus and kin are, and how interpreting fossils of north African spinosaurids is getting increasingly complex. Spinosaurus fossils remain very fragmentary to the point where most cannot be directly compared, they seem to hint at, but don't really crystalise, an apparent high species diversity, and are often of uncertain association or exact origin. At face value, that doesn't leave us with a lot to be confident about, although we'll have to see how this more despondent view goes down with other spinosaurid researchers. More complete and well documented discoveries will soon help smooth out bumps in our knowledge, but it seems likely that a lot of work and discussion remains to sort out what is really going on with north African, Late Cretaceous spinosaurids.

What does this mean for 'the Spinosaurus reboot'?

That's not quite the end of our discussion, however. It might be assumed that the points outlined above sound the death knell for the strangely proportioned 2014 Spinosaurus reconstruction, and that we should go back to our traditional interpretation of this animal. That might not be quite right, for two reasons. Firstly, given how distinctive many 'Spinosaurus' remains now seem to be, it's actually questionable what specimens should be considered Sp. aegyptiacus at all, other than the first specimen described by Stromer. A lot of referred isolated Spinosaurus specimens have been incorporated into our 'traditional' reconstructions in recent years, and we might need to think hard about their role in our interpretations of this animal. What we've become typically used to thinking of as Spinosaurus may not entirely be Spinosaurus!

Secondly, while some aspects of the 2014 interpretation of Spinosaurus have clearly been challenged by the Evers et al. paper, not all proportional aspects of the recent Spinosaurus reinvention are obviously erroneous. Last year, Ibrahim et al. noted that both Spinosaurus B and the 'neotype' have reduced hindlimbs with respect to their associated vertebrae, and used this fact as support for the diminutive legs in their reconstruction. Although arguing that there is no longer evidence for short hindlimbs in Spinosaurus itself, Evers et al. don't completely dismiss the notion of some African spinosaurids being short legged. The hindlimb proportions of those specimens is very similar despite the vagaries surrounding fossilisation and exhumation of ancient animal remains, maybe more similar than you'd expect from chance alone. If it is coincidence, it's certainly a startling one.

Stromer's 'Spinosaurus B' material: proportionally similar to the 'neotype' specimen, but does that tell us anything about spinosaurid proportions? Another image borrowed from Theropoda.
However, Evers et al. also attach some important caveats to this point. Stromer's notes clearly state that he did not consider the 'Spinosaurus B' material to represent one individual, and his testimony is the closest thing we have to a report on the excavation of the material. He specifically comments on the hindlimb being too small and slender to match the vertebrae, and thus interpreted them as representing a second individual. Other workers have agreed that this material must represent multiple animals or even several types of dinosaur (discussions about the possibly chimeric nature of Stromer's spinosaur specimens are not new - e.g. Rauhut 2003; Novas et al. 2005). Interpretation of the Spinosaurus B material as representing one animal is thus against some current thought and, of course, Stromer's original declaration. While the 'neotype' specimen might make a case for Stromer being mistaken, we really need to know more about the collection history to ascertain that. We're left with an intriguing set of measurements hinting at the reduced hindlimbs proposed by Ibrahim et al., but little in the way of objective information to explain their significance. The discovery of new specimens is needed to establish whether some spinosaurids were really short-legged, or if confusion of specimen inventories just made it look that way. In short, and no-doubt to the disdain of people who lose sleep about 'what science has done' to one of their favourite theropods, there's still something to play for with these short-legged spinosaurids.

So that's the latest chapter of research in Spinosaurus, then: I don't doubt that it's going to cause a lot of discussion in popular and academic circles. My personal take-home is that we seem to know less about Spinosaurus than might have been recently suggested, or at least that some issues need to be ironed out before we can develop a clear picture of what Spinosaurus is, and what sort of lifestyle it led. I don't know that any recent proposals about this animal have been shot down entirely yet, although clear gauntlets have been established for some of the more extreme ideas suggested in the last few years. It's going to be very interesting to see how others interpret these latest developments in the ongoing Spinosaurus saga, and where our understanding of this animal moves to next.

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References


  • Evers, S. W., Rauhut, O. W. M, Milner, A. C, McFeeters, B, & Allain R. (2015) A reappraisal of the morphology and systematic position of the theropod dinosaur Sigilmassasaurus from the “middle” Cretaceous of Morocco. PeerJ 3:e1323
  • Ibrahim, N., Sereno, P. C., Dal Sasso, C., Maganuco, S., Fabbri, M., Martill, D. M., & Zouhri, S., Myhrvold, N. and Iurino, D. A. (2014). Semiaquatic adaptations in a giant predatory dinosaur. Science, 345(6204), 1613-1616.
  • Novas, F., Dalla Vecchia, F., & Pais, D. (2005). Theropod pedal unguals from the Late Cretaceous (Cenomanian) of Morocco, Africa. Revista del Museo Argentino de Ciencias Naturales nueva serie, 7(2), 167-175.
  • Rauhut, O. W. M. (2003). Special Papers in Palaeontology, The Interrelationships and Evolution of Basal Theropod Dinosaurs (No. 69). Blackwell Publishing.

29 comments:

  1. "Our principle Spinosaurus material fell victim to Allied bombing raids in World War II and was completely destroyed. Stromer's detailed illustrations and descriptions are all that remains of this material."

    Didn't some casts also turn up?

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    1. Not to my knowledge. Photographs of the mounted holotype were discovered in the mid 1990s, and I think they remain the most direct representation of that material.

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    2. We don't have any casts, unfortunately. Stromer's descriptions are decent/good, and the few illustrations help (and so do the photographs).

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    3. I think erection of a neotype if done according to the code's recommendations is final. Ie the original material on which the name was based is NO LONGER the name bearing material - that of the neotype is. Thus even if those whom erected the neotype made an error (such as the neotype is actually not the same species as the original - something one cannot know unless the original turns up again), the species name Spinosaurus aegyptiacus applies to the new Kem Kem specimen. People can complain all they want, but the name Spinosaurus aegyptiacus now applies to the specimen described in 2014 and that material described by Stromer is now irrelevant to this name. This is the point of erecting a neotype - now the name applies to an actual specimen that folk can examine! Trevor Worthy

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  2. Oh, maybe that's what I was thinking of.

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  3. Thanks for making a succinct summary, I don't have the time & effort to slog through that paper...

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  4. Sorry, but no. Paragraph 75 of the ICZN regulates the erection of a neotype. Among others, it says:
    "75.3. A neotype is validly designated when there is an exceptional need and only when that need is stated expressly and when the designation is published with the following particulars:"
    This clearly states that there has to be an exceptional need, something that we consider to be not the case, as the description and illustrations by Stromer are sufficient to define the taxon.
    "75.3.5. evidence that the neotype is consistent with what is known of the former name-bearing type from the original description and from other sources"
    This has not been demonstrated by Ibrahim et al. Indeed, they do not refer to Stromer's description of the type of Sp. aegyptiacus, but rather to his "Spinosaurus B" - which he explicitly did not consider to be Sp. aegyptiacus.
    "75.3.6. evidence that the neotype came as nearly as practicable from the original type locality [Art. 76.1] and, where relevant, from the same geological horizon ... as the original name-bearing type"
    The localities are more than 3000 km apart, there probably was a seaway separating them at that time, the evidence for the Kem Kem being the exact geological age as Baharyia is sparse at best, and, as we point out, there is actually no real faunal overlap otherwise between the two areas. Thus, this criterion is definitely not met.
    As we therefore point out in our paper, we consider that the formal requirements of neotype designation were not met in the Ibrahim et al. paper, and their designation of a neotype is therefore not valid.

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  5. Will someone clear up the mess that is the biggest theropod ever?

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  6. Yes, someone will.

    But it will be someone who has seen all the material, and invested significant time in studying it and comparing it to other theropod material. Which means it's not going to happen overnight.

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  7. It seems like this paper is trying its damnedest to imply that the shorter limbs are incorrect, and yet at the same time they fail to give any convincing evidence of this. Even if we remove the elements not associated with Spinosaurus aegyptiacus we are left with a short legged Spinosaurus, just one missing a lot more spinal material. And if we go so far as to remove the nomen dubium Spinosaurus maroccanus that leaves us with two species of Spinosaurus, one with short legs (maroccanus) and one with no legs for which the conservative assumption is still to give it short legs (aegyptiacus). So for however lengthy this paper is it fails to give any evidence to support it's claims regarding limb validity.

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    1. "It seems like this paper is trying its damnedest to imply that the shorter limbs are incorrect,"

      That's not really true. The focus of the Evers et al. paper isn't the limb proportions at all, but the taxonomy of north African spinosaurids and the validity of Sigilmassasaurus. Their findings have implications for the short limbed Spinosaurus reconstruction, but the proportions presented in the 2014 paper are only briefly mentioned.

      "Even if we remove the elements not associated with Spinosaurus aegyptiacus we are left with a short legged Spinosaurus,"

      Well, not really. The take-home interpretation of Evers et al. is that we _might_ have short-limbed spinosaurids, but that we can't be confident about alleged Spinosaurus limb material actually belonging to this genus. They're quite clear in their taxonomic conclusions, and it doesn't match what you outline here.

      "So for however lengthy this paper is it fails to give any evidence to support it's claims regarding limb validity."

      With respect, have you read the paper in detail? It doesn't make any 'claims regarding limb validity'. Limb proportions are mentioned in (writing from memory) a couple of paragraphs, the discussion about the 'neotype' and Spino B mostly concerning aspects of association, preservation, taxonomy etc. This is not a paper about how to reconstruct Spinosaurus.

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    2. I read between the lines and fixated a bit strongly on that point, I do gather the intention of the paper wasn't primarily of this point. My apologies for coming across rather strong.

      I don't quite follow the evidence against the placement of the remains in the Spinosaurus genus. The remains applied to the neotype are very similar from what I can tell from diagrams and while I do acknowledge they may not be synonymous I would hesitate to place it outside of the genus. We also have the issue of the name possibly migrating to the neotype, which similar to the issue of Tyrannosaurus would dictate that the specimen recognized under the name would be attribute to it.

      I do follow where you're going and I appreciate the conclusions of the paper, but I still feel that the conservative conclusion is that neither maroccanus nor Sigilmassasaurus are different enough to warrant a separate genus. And more pertinently that regardless of genus status given that they are invariably the closest related remains the Ibrahim et al reconstruction is still the safe assumption we have for any of the species given.

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    3. ^ I think the point that Misheru Misaki is trying to make is that for a paper that - as you put it Mark is primarily about the validity of Sigilmassasaurus/taxonomy - to go into the issue of the potential chimeric nature of FSAK-11888 is a little off-topic and not really needed. Furthermore they come at this issue with a definite negative slant. While Evers et al. mention the dubious history of fossil collectors and mixed remains in the Kem-Kem Evers et al. omit to mention that there is no duplication of material in FSAK-11888 and that the bone histology of FSAK-11888 (in supp. material Ibrahim et al.) suggests "subadult" in both the vertebral AND appendicular elements (i.e. not suggestive of chimera of several different growth stages). For me this is a troublesome omission, especially in such a large paper, and that the paper would have been better served if it just left the bits out casting aspersions on FSAK-11888, which as you say Mark, is not really the take-home message anyways.

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    4. Sorry Duane, I think you're wrong here. The taxonomy of Sigilmassasaurus is intimately entwined with that of Spinosaurus, and understanding whether the two are distinct is reliant on a concrete understanding of what Spinosaurus is. We have to make sure type specimens are authentic, reliable reflections of single individuals in order to do this, and when this in doubt - as it is for Spinosaurus - it is perfectly reasonable for authors to express their concerns about it.

      "Furthermore they come at this issue with a definite negative slant."

      I don't think this is the case at all - seems to me the comments are made clearly, without bias, and appropriate to the current state of play on spinosaurid taxonomy. Paraphrasing Tom Holtz: "we're not in this business to make people happy: we're scientists, dammit."

      "Evers et al. omit to mention that there is no duplication of material in FSAK-11888 and that the bone histology of FSAK-11888 (in supp. material Ibrahim et al.) suggests "subadult" in both the vertebral AND appendicular elements (i.e. not suggestive of chimera of several different growth stages)."

      This is certainly another chalk in the column for Spino B and the neotype being genuine representations of single individuals, but it isn't a deal clincher. For one, growth stages are hard to pin down precisely in fossil animals. It's easy to recognise very old or very young animals, but the vast majority of fossils fall into a nebulous void between, which we often term 'late-stage juvenile' or 'subadult'. It can be hard to determine anything more specific for this even in species with well-known growth trajectories. It's not a precise art, is what I'm saying, and law of averages dictates that any two random specimens will almost always be of 'subadult' growth stages. Secondly, this point does not resolve the most pressing issue of this discussion, the lack of field data for all relevant Spinosaurus specimens. Until such data is presented, all these points made about specimen association, proportions, ontogenetic stages etc. reflect probabilities, hunches and supposition - none of which make a basis for particularly robust science.

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  8. I would like to see more skeletons to be able to know for certain whether Spinosaurus was a quadraped.

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    1. I have a hard time accepting that limbs could be so short on an adult spinosaurus. I also have a hard time believing that a theropod could be quadrupedal. It seems very unlikely.

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  11. Searching about the facts and what was the timeline some of the important questions that you have to ask from yourself to the beginning that will make you feel more comfortable to some aspects you are going to read about. writing a research proposal

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  12. To me as an engineer from an unrelated field it is still unclear weather the correct procedure to claim Spinosaurus 2014 as *the* Spinosaurus, dismissing Stromer's find, has been followed. Sorry, I got lost in the arguments.

    I'm trying to convey paleontology as a very much alive discipline to my son and this sounds like an important aspect for this instance.

    Also it is very cool being able to casually stumble upon in-depth discussions with the real scientists when all I wanted was a little background prior to seeing the new Spinosaurus model on exhibition in Berlin :)

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    1. It's a little unclear for most of us at the moment! There are competing ideas and interpretations of the Spinosaurus material, and this area should be considered 'in flux' for the time being. One fairly consistent theme in recent papers is scepticism of the 2014 reconstruction being accurate. It's since been well demonstrated that many spinosaurines lived in the same area, and it's likely the 2014 reconstruction is a composite of multiple species. That's not to say that some of the more unusual elements of it - like the short hindlimbs - are erroneous, but do those legs belong to Spinosaurus or another spinosaurine? We may not have the fossils to answer that with yet, but this is an active area of research, and new analyses and discoveries may change that soon.

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  13. My theory on looking through substantial material is that there were no actual reptiles until near the end of the Permian. Thus, Dimetrodon and Edaphosaurus were amphibians or at least "pre-reptiles". (Wait, I'm getting there.) The purpose of their sails would thus have been to add moist skin surface area for respiration. (See "Turquoise Energy News #100" for more on this.)

    So just to add to the confusion here's an off the wall theory: Could Spinosaurus have been a big latter day amphibious "Dimetrodon" knock-off? (Bone microanatomy saying low metabolic rate? Heavy sternum? Wide throat?) Okay, it sounds pretty wild to me too. But that sail...?

    Also: Might a marine/swimming coast dweller have swum across N. Africa from Egypt to Morrocco where land dwellers were blocked by some obstacle(s)?

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  14. One problem bruce lee, Petrolacosaurus kansensis was a diapsid reptile and it lived before the Permain, so there were reptiles around in the Permain period, also Dimetrodon and Edaphosaurus were stem-mammals, not reptiles. That and the sails are now thought to be sexual display.

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  16. All the above mentioned seem to have the heavy sternum and clavicles that I now associate with amphibians - to anchor the buccal breathing muscles. And early diapsids like Petrolacosaurus differ from "neodiapsids" in a number of ways, so I think it's a leap to simply assume they were reptiles on the basis of the skull having two extra holes for jaw muscles. Then, more primitive, generalized amphibian features may perhaps superficially seem 'more mammalian' than more specialized reptilian features. Anyway that's my take on it.

    One must remember that in the 1800s until maybe around 1960(?) there was no class called "amphibia" and that turtles and otters were generally called amphibians because they lived in and out of the water. (I remember in grade school being told of the new definition.) Thus, a salamander fossil might easily be called a 'reptile'. And then later the meaning of 'reptile' became more exclusive. But at that point someone would have to figure out very specifically that it was actually in the new class of 'amphibian' before the classification would be changed - perceptions once formed die hard. I am suggesting that that is the case with all "reptiles" until the near end of the Permian, and that the change of nomenclature is a part of the original problem, distorting everyones' perspective.

    And it makes more sense from an evolutionary timeline perspective, too.

    Anyway I've gone on far too long. Whether Spinosaurus was amphibian or reptile, it now looks more and more like a sort of aquatic creature that filled the role of a piscivorous crocodile. Perhaps there was a giant lake or system of waterways in Northern Africa in the Cretaceous, geographically isolated from regular crocodiles, so a dinosaur (or ?) evolved to fill that niche in waters teeming with big fish?

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  17. I'm not agreeing with you that Dimetrodon and Edaphosaurus were amphibians. I go by modern standards of their classification, and I have read from several reputable sources that both of those animals are stem-mammals, not amphibians

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  18. Have there been any recent breakthroughs regarding this issue? Are there any ongoing research investigations into Spinosaurus aegyptiacus and the neotype? If so, who's running them? Has anyone been able to return to Stromer's original site in Egypt in order to look for more examples of S. aegyptiacus?

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