Prorotodactylus and Rotodactylus: Produced by a Dinosauromorph Archosaur or a Lepidosaur?

There were some strange footprints
in the Early and Middle Triassic in the Holy Cross Mountains of Poland. These are covered in a new paper by Niedzwiedski et al. (2013). They report, “The first body fossil evidence of dinosauromorphs is a few million years younger than the youngest Polish tracks, so Prorotodactylus and Rotodactylus tracks currently provide the oldest record of dinosauromorph morphology, biology and evolution. Here, in this monographic treatment, we provide a detailed documentation of the Polish Prorotodactylus  and Rotodactylus record from the late Early (Olenekian) early Middle (Anisian) Triassic.”

Peabody (1948) introduced us to Rotodactylus from the Moenkopi formation. Haubold (1966, 1967) cataloged several types.

Prorotodactylus“Diagnosis (based on Ptaszyn´ski 2000a; Brusatte et al. 2011; Klein & Niedz´wiedzki 2012). Long striding trackways with small lacertoid pentadactyl pes and manus imprints. Manus overstepped laterally by the pes. Pes outwardly and manus inwardly rotated with respect to the midline. Digitigrade pes with digits I–IV increasing in length, II–IV subparallel and tightly ‘bunched’ with distinct straight metatarsal–phalangeal axis (i.e. straight posterior margin of the preserved digit imprints), digit I everted. Digit V rarely impressed, and if present, located in a posterolateral position and relatively short in comparison to digits I–IV. Manus semiplantigrade or plantigrade, of chirotheroid shape, compact and rounded with posterolaterally positioned digit V mostly impressed. Digit III longest, followed by IV, II and I, which is shortest. The main difference between Prorotodactylus and Rotodactylus is the position and shape of digits V in both the manus and pes imprints of Prorotodactylus.”

Figure 1. Click to enlarge. Chronology of ichnites, from Niedzwieczki et al. 2013. My notes in red. Blue ichnites have been flipped for consistency (now they're all righties, no lefties). Note the middle traces include a manus in which digit 4 is longer than 3, distinct from the others, but overlooked by Niedzwieczki et al. 2013.

Figure 1. Click to enlarge. Chronology of ichnites, from Niedzwieczki et al. 2013. My notes in red. Blue ichnites have been flipped for consistency (now they’re all righties, no lefties). Note the middle traces include a manus in which digit 4 is longer than 3, distinct from the others, but overlooked by Niedzwieczki et al. 2013.

Unfortunately,
The only derived and small archosauriforms with pedal digit 4 longer than 3 include lagerpetids, like Tropidosuchus and Lagerpeton (Fig. 4), two taxa not related to dinos, according to the large reptile tree. Neither these two nor its closest sister, Chanaresuchus, has pedal digit 5. None of these three preserved the manus. Metatarsal and phalangeal proportions do not match the ichnite either. You have to go all the way back to Proterosuchus to find an archosauriform with pedal digit 4 longer than 3, a plesiomorphic trait of basal reptiles.

The combination of manus digit 3 > 4 and pedal digit 4 > 3 is the key to discovering the trackmaker of Prorotodactylus. Here we’ll find that very few taxa are a good match for Rotodactylus and Prorotodactylus ichnites. Several have that formula, but few have the much smaller manus and short fingers.

Figure 2. Click to enlarge. Among the few taxa that have a longer manual digit 3 than 4 AND a longer pedal digit 4 than 3 include Owenetta, Emeroleter, Sphenodon, Cosesaurus and Tanystropheus.

Figure 2. Click to enlarge. Among the few taxa that have a longer manual digit 3 than 4 AND a longer pedal digit 4 than 3 include Owenetta, Emeroleter, Sphenodon, Cosesaurus and Tanystropheus.

And more here:

More reptiles with the unusual manual digit 3 longer than 4 AND pedal digit 4 longer than 3.

Figure 3. More reptiles with the unusual manual digit 3 longer than 4 AND pedal digit 4 longer than 3 include the basal lizards, Liushusaurus and the Daohougo lizard, plus Lazarussuchus. None of these taxa were even considered by Niedzwiedski et al. (2013).

Niedzwiedski et al. (2013) in their quest for a trackmaker to fit Rotodactylus published this image of Lagerpeton, which is an obvious mismatch that doesn't even have a pedal digit 5.  Plenty of other taxa are better matches (Figs. 3,4) but those weren't published, tested or promoted.

Figure 4. Niedzwiedski et al. (2013) in their quest for a trackmaker to fit Rotodactylus published this image of Lagerpeton, which is an obvious mismatch that doesn’t even have a pedal digit 5. And the pedal digit 5 impression does not include an ungual (Peabody 1948). The ungual impression was added with hope, not data. Plenty of other taxa are better matches (Figs. 3,4) but those weren’t published, tested or promoted.

To their credit,
Niedzwiedski et al. (2013) reported, “As Lagerpeton is only known from South America and the Ladinian, it is unlikely that this particular genus was responsible for the Polish footprints. Furthermore, there are specific differences between the foot skeleton of Lagerpeton and the Prorotodactylus and Rotodactylus footprints. Our argument, however, is not that Lagerpeton itself made the Polish footprints, but rather that the Prorotodactylus and Rotodactylus tracks were made by a non-dinosaurian dinosauromorph closely related to, and sharing derived characters with, Lagerpeton.”

Talk about bad science. 
You can see by the above confession that Niedzwiedski et al. (2013) agreed this was a bad match. So why did they promote this? And only this? This is the core result of their entire paper and its predecessor (Brusatte et al. 2011). They also virtually ignored and dismissed the absolutely perfect match provided by Peters (2000, Fig. 6). They also ignored every other taxon that could have made these tracks (Figs, 2,3) better than Lagerpeton. Evidently, someone had a point to prove, and doggone it, facts were not going to get in the way of this hypothesis!

The best matches to Prorotodactylus and Rotodactylus. In this case, something between a small Tanystropheus and an even smaller Cosesaurus provides the best matches in all regards.

Figure 5. The best matches to Prorotodactylus and Rotodactylus. In this case, something between a small Tanystropheus and an even smaller Cosesaurus in the digitigrade configuration provides the best matches in all regards. These taxa were not even mentioned by Niedwiedcki et al. (2013). Skeletal fossils are known from geographically and chronologically similar sediments. Both of these taxa are tritosaur lizards, not archosaurs and not protorosaurs and certainly not non-archosaur archosauriforms. Other sister candidates include langobardisaurs, which also have a wide distribution.

Niedzwiedski et al. (2013) refer to Brusatte et al. (2011) supplementary materials for further explanations regarding trackmaker selection. Unfortunately they had their bias blinders on. They did not include any lizards, but focused only on their favorite archosaurs.

Niedzwiedski et al. (2013) grant, “Some other recent authors have presented alternative identifications of the Rotodactylus trackmaker. Lockley & Hunt (1995) considered the trackmaker to be a lepidosauromorph with a specialized gait. Peters (1996, 1997) briefly discussed (in abstracts) a potential close relationship between Rotodactylus and pterosaurs, while Peters (2000) identified Rotodactylus as being made by a nonarchosaurian archosauromorph.” (BS! I said it was a perfect match to Cosesaurus, which is not a nonarchosaurian archosauromorph! I’ve never used that term. See how twisted paleontologists can get? (more examples here and here). It’s shameful and creepy.)

Niedzwiedski et al. (2013) report, “Regardless of the precise affinities of Rhynchosauroides, a lepidosauromorph or non-archosaurian archosauromorph would not be expected to possess footprints that formed narrow gauge trackways and are consistently digitigrade, with reduced outer digits and tightly bunched central digits.” [See the bias! The Jayne labs prove that fast-moving lizards are narrow-gauge and digitigrade. And these were no ordinary lepidosaurs. They were well on their way toward bipedal locomotion. This group certainly did not exhaust the possibilities (Figs. 3, 4). They kept their blinders on. Now I know exactly how Branch Rickey felt when others were verbally attacking his best ballplayers!] Just because the taxa I promote come from the other side of reptile family tree doesn’t mean they can’t play.

Cosesaurus matched to Rotodactylus from Peters 2000.

Figuure 6. Cosesaurus matched to Rotodactylus from Peters 2000. This a perfect match with no imagination or excuses added. Why didn’t Niedwiedski et al. (2013) acknowledge this? They obviously had a preset agenda. Their conclusions ruled their data. Dinosaurs are cool, they make the news. Cosesaurus, fenestrasaurs, tritosaurs are bench players in their mind, not worth considering. The proximal pahalanges were elevated because the metatarsophalangeal joint was a butt joint, retained by the pterosaur Dimorphodon(?) weintraubi, among other sister taxa.

Niedzwiedski et al. (2013) report, “Furthermore, a pterosaur identification for the Polish tracks is also unlikely, because the feet of Triassic pterosaurs retain elongate pedal digits I and V, unlike dinosauromorphs, and the digits are splayed distally, unlike the tracks of Prorotodactylus and Rotodactylus and the feet of Lagerpeton (e.g. Wild 1978; Dalla Vecchia 2009).”

The patron saint of "No Respect", Rodney Dangerfield.

Figure 8. The patron saint of “No Respect”, Rodney Dangerfield.

This is a red-herring!
Niedzwiedski et al. (2013) argued against something that wasn’t even promoted. Peters (2000) matched Cosesaurus to Rotodactylus because it is a good match! Yes, pterosaurs descended from Cosesaurus and basal forms made similar tracks (Peters 2011), with pedal digit 5 impressing behind the other four digitigrade digits, sometimes splayed, sometimes not. So, why would good paleontologists turn a blind eye to all the best possibilities and force fit a bad match to their discovery?

I keep asking myself the same thing almost every day I write this blog. Unfortunately, this sort of thing happens all the time. For now it’s just grist for the mill.

ADDENDUM
The following was added after original publication. These are examples of how pedal digit 5 operated in basal pterosaurs. Note the impression varies from a single round knuckle impression far behind the digits to a complete phalanx impression (Peters 2011, will send on request).

Digitigrade pterosaur pedes. This is how pedal digit 5 worked in pterosaur taxa with a pedal digit 5. We have ichnites that match anurognathid pedes. See them in the digitigrade pterosaur pedes post linked in the text.

Addendum figure: Digitigrade pterosaur pedes. This is how pedal digit 5 worked in pterosaur taxa with a pedal digit 5. We have ichnites that match anurognathid pedes. See them in the digitigrade pterosaur pedes post linked in the text. PILs (parallel interphalangeal lines are easy to gauge here).

I also encourage you to check out an earlier post on digitigrade pterosaur pedes.

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.

References
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.
Haubold H 1966. Therapsiden- und Rhynchocephalien-Fahrten aus dem Buntsandstein Sudthuringens: Hercynia, N. F., v. 3, p. 147-183.
Haubold H 1967. Eine Pseudosuchier-Fahrtenfauna aus dem buntsanstein Sudthurigens: Hall. Jb. Mitteldt. Erge, v. 8, p. 12-48.
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
Peabody FE 1948.  Reptile and amphibian trackways from the Lower Triassic Moenkopi formation of Arizona and Utah.  University of California Publications, Bulletin of the  Department of Geological Sciences 27: 295-468.
Peters D 2000. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification.Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605.

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5 thoughts on “Prorotodactylus and Rotodactylus: Produced by a Dinosauromorph Archosaur or a Lepidosaur?

  1. Your choices would seem to imply a seriously dislocated DV. In that regard they are no more useful than a foot with no DV. It is obvious that whatever made these tracks had a pedal morphology unlike what you have presented as well as the prior publication.

  2. Yeah, Digit 5. In Figure 4 of this post it is clear that there is one digit that is pointing caudally. Based on the metatarsals of the organisms you have shown (compact bundles) I don’t see how any of your proposed trackmakers are any more reasonable than the ones you are arguing against. In one case there is a missing 5th digit, in the other there is a far posterior digit. Neither case is represented in the body fossil record.

  3. I have added several examples of “far posterior digits” from the Pterosauria to this post and I sent you the “Catalog of Pterosaur Pedes” which includes ichnites and fenestrasaur examples.

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