The foot of Tropidosuchus: Another Lagerpeton sister without a pedal digit 5

This post follows
an earlier one that found fault with Niedzwiedzki et al. (2013) and Brusatte et al. (2011), which attempted to match four-toed Lagerpeton (Fig. 2) to five-toed Prorotodactylus and Rotodactylus ichnites, claiming these tracks represented the earliest examples of dinosauromorphs in the fossil record. Beside the morphological mismatch, which they acknowledged yet based their papers on, the large reptile tree found Lagerpeton was not even a dinosaur ancestor, but nested far afield with another chanaresuchid, Tropidosuchus (Fig. 3). Here we’ll show another Lagerpeton/Tropidosuchus sister with a metatarsal 5 lacking a pedal digit 5 sealing the deal that neither Lagerpeton, nor any close sister, could have made Prorotodactylus or Rotodactylus tracks. Even a further distant sister, Chanaresuchus (Fig. 4), lacks pedal digit 5.

A skeleton attributed to Tropidosuchus, but shares traits with Lagerpeton.

Figure 1. An unidentified skeleton attributed to Tropidosuchus, but shares traits with Lagerpeton. No pedal digit 5 here.

Above is a specimen and its reconstruction attributed to Tropidosuchus (Bonaparte 1994), but notice the difference in the pedal proportions and other proportions. The foot morphology is much closer to Lagerpeton. This specimen also has a smaller humerus than Tropidosuchus. The pelvis is distinct from both genera. Chevrons are missing from this specimen. Chevrons may be missing form this clade, which otherwise shares a relatively wide tail base according to the caudal transverse processes.

Lagerpeton reconstructed.

Figure 2. Lagerpeton reconstructed. No pedal digit 5 here.

Tropidosuchus romeri (Arcucci 1990) Late Triassic was originally considered a lagosuchid like Marasuchus but here derived from a sister to BPI 2871 and Chanaresuchus. The pes of Tropidosuchus was quite similar to that of Chanaresuchus emphasizing digit 2 with a slender metatarsal 4. The tarsals did not have a calcaneal heel.

The holotype of Tropidosuchus retains the narrower digit 4 of Chanaresuchus.

Figure 3. The holotype of Tropidosuchus retains the narrower digit 4 of Chanaresuchus. No pedal digit 5 preserved here.

Chanaresuchus bonapartei (Romer 1971) Anisian, Early Middle Triassic is a sister to Tropidosuchus. The most robust metatarsal was mt 2 Digit 3 was the longest. Metatarsal IV was extremely gracile and digit V was absent.

Chanaresuchus a quadrupedal ancestor to Tropidosuchus and Lagerpeton and the third taxon.

Figure 4. Chanaresuchus a quadrupedal ancestor to Tropidosuchus and Lagerpeton and the third Tropidosuchus-like taxon. No pedal digit 5 here.

So, why are professors promoting such mismatches? Why are reviewers approving such mismatches? Better matches to Prorotodactylus and Rotodactylus can be found in several untested taxa, as we saw earlier here. There must be a syndicate operating here, friends helping friends. Sometimes Science needs critics, not friends.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

Arcucci A 1987. Un nuevo Lagosuchidae (Thecodontia- Pseudosuchia) de la fauna de Los Chañares (edad reptil Chañarense, Triásico Medio), La Rioja, Argentina. Ameghiniana 24, 89–94.
Bonaparte JF 1994. Dinosaurios de America del Sur. Impreso en Artes Gráficas Sagitario. Buenes Aires. 174pp. ISBN: 9504368581
Brusatte SL, Niedz´wiedzki G and Butler RJ 2011. Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic. Proceedings of the Royal Society B, 278, 1107–1113.
Niedzwiedzki G, Brusatte SL and Butler RJ 2013. Prorotodactylus and Rotodactylus tracks: an ichnological record of dinosauromorphs from the Early–Middle Triassic of Poland. Geological Society, London, Special Publications, first published April 23, 2013. doi 10.1144/SP379.12.


8 thoughts on “The foot of Tropidosuchus: Another Lagerpeton sister without a pedal digit 5

  1. “There must be a syndicate operating here, friends helping friends.”
    Really? Anyone who has spent a few minutes among scientists will tell you otherwise, everyone is at each others’ throats over everything. This sounds like the paranoid ramblings of any pseudo-scientist, saying “it’s not me, it’s them” and when pressed on who “they” are, starts making unsubstantiated claims about shadowy cabals trying to suppress some profound insight into the nature of the universe, all simply because a reviewer felt his work was wanting when it was submitted to a journal (something that happens all the time).
    If I could I would pay you to volunteer at a fossil prep lab (as long as you don’t take every unremarkable matrix feature to be part of the fossil), or to dissect some reptile specimens. It might help you to at the very least understand where everyone else is coming from. Hint: they work with physical specimens, they don’t just sit at a computer mucking about with shoddy photographs all day. Might some things be overlooked in physical examination that are later found with a cursory look at a photo? Yes, but that does not immediately mean the latter method suddenly becomes superior, superceding the former.
    The scientific community is not infallible, but it is made up of people, each with his or her own opinion, who have physically studied anatomy, taphonomy, and the complex theory behind cladistic analyses backwards and forwards for years, and have spent years, if not decades physically handling and examining fossil specimens for years if not decades. These are not people who are trying to feel good. The other guy is a Jon-Erik Beckjord who sees things in pixels and thinks a photo from a book with the halftone blurred out is a superior replacement to the specimen and has expended minimal effort into understanding the theory and mathematics that underlies those numbers-go-in-tree-comes-out cladistics programs and “just look at it” is a good argument for phylogenetic nesting of taxa. The arguments are not at the same level, and claiming they are, and claiming that there is some shadowy cabal shooting them down is a disservice to the entire field, professionals, amateurs, and interested laymen included, if not just outright dishonest.

    • Approving the idea of a four-toed fossil fitting into a five-toed fossil that it couldn’t possible fit into is the issue here. But thanks for the rant if it helped you feel better about things.

      • I think Rob Gay gave that matter sufficient attention in the previous post. Ichnology is not a strightforward match-the-taxon-to-the-track endeavour, and it is not easy to determine pedal morphology from a footprint given that it is not a mould, but an impression left behind by an organism moving through an environment.
        It is not a bad thing to say “I don’t know” in science.
        Before you make an argument, please consider what you are saying and the implications involved. That post was filled with paranoid and completely unfounded claims about “agendas” and this claim about some “syndicate” is no better.

  2. You give ichnology too little credit. In some cases the impression is the next best thing to being there. With regards to favoritism and syndication, I’ve seen it, I’ve experienced, I’ve benefitted from it, I’ve been blackballed because of it. It’s real. Birds of a feather flock together. Odd man out. This is human nature, self preservation, running with the pack, etc.

  3. (ok, adding this sentence about half way through the post, realising how long it is and that I have more to say. feel free to take tea break around where I talk about Raup and Sepkoski)

    Has it occurred to you that when everyone disagrees with you, its because everyone disagrees with you, not because they’re in a gang and you’re not invited? The argument that scientists are desperately trying to preserve dogma is just as ridiculous when you use it as when creationists do. When you actually stop and think about how science works you will see how idiotic it is.

    Think of the most famous, respected palaeontologists in the field at the moment. Names like Robert Reisz, Mike Benton, John Alroy, Wolfgang Kiessling, Susan Evans, Jenny Clack…Are these the people who meekly sat in their offices repeating the Dogma? of course not! What scientist ever made their name bleating the wisdom of the ancients? When was the last time a high profile publication, or a scientific award, was given to someone for confirming what was known?

    Take one of the most well established ideas in quantitative palaeontology: the Raup and Sepkoski curves and their ideas about the evolutionary faunas. These have been the mainstay of people’s oppinions on diversity for decades, taught to every student, and the ideas on ecology and the 5 mass extinctions they promoted are still taken as a given. However, John Alroy and Wofgang Kiessling have, for the last decade or so, been attacking different aspects of these dogmas. Have they been vilified, blackballed, ignored? no, they are among the most highly respected quantitative palaeontologists out there, who have many high profile publications to their name. They have their critics, even among the ‘city fathers’. but no “syndicate” has appeared trying to shut them out.
    When Robert Reisz took apart Romer’s phylogeny of synamsids and rebuilt it from the ground up, was he shunned by a syndicate? When Susan Evans took a hack saw to Bob Carroll’s list of lepidosaurs, was she bundled into a corner? When Jenny Clack proposed that the tetrapod limb evolved in water (possibly the most radical idea of the previous generation) was she callously ignored?

    Scientists want to challenge dogma, want to change what is known. As a young scientist just getting started with my career, it is my dream to overturn what is known about even the tiniest portion of the amniote tree. If I could make the dramatic change you are trying to promote, I could die happy.

    The peer review process acts as a check against these emotions. It is brutal, and rightly so!!!!. No scientific idea should be published without first going through the most minute scrutiny, being challenged, nit-picked and generally torn to pieces. Everyone thinks their ideas are right, and it can be quite discouraging when someone rips into them. On my very first submission, one of the reviewers was the very man whose analysis I was criticising in my paper. I’m sure you, with your dim view of the peer review process, expect that he just chucked it in the bin. But no. His review was vicious, discouragingly so, but not only did he recommend acceptance (albeit with major modifications) but he even said in his review “It is fine and justified to put the boot through the [smith] analysis” (smith is a pseudonym).

    All new ideas in science should be subject to this criticism. Arguments put forward in the internet are just an excuse to sidestep review and to get your ideas out without the hurdles all scientists endure. If you want to change science, your ideas should be subject to the same scrutiny all of ours are. If you get a bad review, you should the criticism and examine it. more research is done into the points being raised. changes are made. if you think the reviewer is incorrect, you put forth your argument, not to the internet, but in your response to reviewers letter or in a new paragraph in your resubmitted publication.

    You do not storm off in a fit of pique and complain to the internet about how there is a conspiracy to drive you out.

  4. Thank you for your thoughts, Neil. When I see a mistake due to taxon exclusion, or when someone tries to shoehorn a four-toed taxon into a five-toed ichnite, I call attention to it. So, when paleontologists include thalattosaurs with Vancleavea studies…and when they include tritosaur lizards with pterosaur studies then I, too, will die happy. Keep following your noble calling. I wish you every success.

  5. Unrelated to the above conversations:
    I am confused as to how you end up with Tropidosuchus as a biped. Large head, long torso, skinny tail looks like it would end up with the CoM forward of the acetabulum. Lacking a lower forelimb doesn’t help anyone but I think that in the absence of evidence suggesting bipedality it should be assumed to be quadrupedal. Unless there is something I am missing?

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