Bipedal archosaur locomotion: Bates and Schachner 2011

Bates and Schachner 2011
report on bipedal archosaur locomotion with an emphasis on the basal poposaur, Poposaurus (Fig. 1).

Figure 1. Poposaurus skeleton and skull. Proportions indicate bipedal configuration.

Figure 1. Poposaurus skeleton and skull. Proportions indicate bipedal configuration.

Unfortunately,
Poposaurus
 and the Poposauridae (Fig. 2) nest just outside the Archosauria in the LRT (Fig. x). The basal croc, Pseudhesperosuchus, and the basal dinosaur, Herrerasaurus (Fig. 3), are valid candidates IF you want to stick to present definitions for the Archosauria.

Figure 1. Poposauridae revised for 2014. Here they are derived from Turfanosuchus at the base of the Archosauria, just before crocs split from dinos.

Figure 2. Poposauridae revised for 2014. Here they are derived from Turfanosuchus at the base of the Archosauria, just before crocs split from dinos.

We need a new name
for the unnamed clade Poposauria + Archosauria: Huperarchosauria (“more than Archosauria”). By just changing the title of Bates and Schachner 2011 to “Disparity and convergence in bipedal huperarchosaur locomotion,” the use of Poposaurus (Fig. 1) as an example becomes valid.

Figure 1. The origin of dinosaurs in the LRT to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.  Note the phylogenetic miniaturization at the origin of Archosauria (Crocs + Dinos).

Figure 3. The origin of dinosaurs in the LRT to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.  Note the phylogenetic miniaturization at the origin of Archosauria (Crocs + Dinos).

From the introduction:
“The clade Archosauria contains a staggering level of morphological, functional and ecological diversity that includes living birds and crocodilians, in addition to an array of enigmatic extinct forms such as dinosaurs and pterosaurs.”

Not pterosaurs. Those have nested apart from archosaurs for the last 20 years (Peters, 2000–2011). Over and over taxon exclusion prevents Bates and Schachner 2011 from understanding the phylogenetic context of their subject matter. For a more complete understanding of archosaur interrelations see the large reptile tree (LRT, 1734+ taxa; subset Fig. x).

Pterosaur and related fenestrasaur bipedalism, based on sprawling lepidosaur hind limbs, was not part of the Bates and Schachner study. Rather they concentrated on the erect hind limb bones and hypothetical muscles in Poposaurus and similar dinosaurs and birds.

Figure 1. Subset of the LRT focusing on Archosauriformes. Clade colors match figure 2 overlay.

Figure x. Subset of the LRT focusing on Archosauriformes. Clade colors match figure 2 overlay.

Add taxa to discover 
all the clade members within the Archosauria (= birds + crocs, their last common ancestor and all descendants). In the LRT Archosauria includes crocs + dinosaurs and nothing more. Poposaurs are the proximal outgroup. Pterosaur nest elsewhere, within Lepidosauria, far from these archosauriform taxa.


Addendum:
There were 10x more views of the recent post on bat origins than the next most popular blogpost this week. I hope these ‘bat’ blogposts help us all understand the transition of arboreal mammals to flapping flight.


References
Bates KT and Schachner ER 2011. Disparity and convergence in bipedal archosaur locomotion. Journal of The Royal Society Interface 9(71):1339–1353.
Farlow JO, Schachner ER, Sarrazin JC, Klein H and Currie PJ 2014.Pedal Proportions of Poposaurus gracilis: Convergence and Divergence in the Feet of Archosaurs. The Anatomical Record. DOI 10.1002/ar.22863
Gauthier JA, Nesbitt SJ, Schachner ER, Bever GS and Joyce WG 2011.
 The bipedal stem crocodilian Poposaurus gracilis: inferring function in fossils and innovation in archosaur locomotion. Bulletin of the Peabody Museum of Natural History 52:107-126.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos 7:11-41.
Peters D 2000b. A reexamination of four prolacertiforms with implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330.
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

 

https://pterosaurheresies.wordpress.com/2011/07/16/what-exactly-is-a-pterosaur-part-3-of-3/

Bipedal crocodylomorph (or giant pterosaur tracks?) from Korea

Kim et al. 2020 describe
sets of 18-24cm narrow-gauge tetradactyl (four-toed) bipedal tracks from the Early Cretaceous (Aptian?) coast of South Korea they name Batrachopus grandis (Figs. 1, 2) a new ichnospecies. The authors attribute the tracks to a large (3m) crocodylomorph. They also note: “Surprisingly, the trackways appear to represent bipedal progression which is atypical of all known smaller batrachopodid trackways.”

You might find their logic train interesting. (See below.)

By the way, such narrow-gauge tracks (Fig. 2) are also atypical for Cretaceous crocs and azhdarchid pterosaurs, like the Late Cretaceous trackmaker of the ichnospecies, Haenamichnus (Figs. 2, 3).

On the other hand, basalmost Triassic crocs were all narrow-gauge bipeds. None of these were large (but that can change), plantigrade (but that can change) or left tracks (that we know of).

Such narrow-gauge tracks were also typical for strictly bipedal pterosaurs, like the coeval (Early Cretaceous) Shenzhoupterus (Figs. 5–7), a taxon overlooked by Kim et al. 2018, 2020.

Figure 1. Batrachopodus grandis tracks from Kim et al. 2020. Note the digits are shorter than the metatarsals and the heel is half the maximum width of the foot, matching both Early Jurassic Protosuchus and coeval (Early Cretaceous) Shenzhoupterus.

Figure 2. Batrachopus tracks (2nd from left) compared to other croc tracks.

Figure 2. Batrachopodus tracks (2nd from left) compared to other croc tracks. Haenamichnus uhangriensis, azhdarchid quadrupedal pterosaur tracks shown at far right, with three fingered manus track, outside and slightly behind the oval (here at this scale) pedal track.

From the Kim et al. abstract:
“This interpretation helps solve previous confusion over interpretation of enigmatic tracks of bipeds from younger (? Albian) Haman formation sites by showing they are not pterosaurian as previously inferred. Rather, they support the strong consensus that pterosaurs were obligate quadrupeds, not bipeds.”

Consensus = current opinion. What you really want  and deserve is evidence! (…and not to overlook evidence that is already out there). Peters 2000, 2011 showed that many pterosaurs were bipedal. Specific beachcombing clades were quadrupedal secondarily.

Figure 2. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

Figure 3. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

Unfortunately,
basal crocodylomorph feet are almost entirely absent from the fossil record in tested taxa in the large reptile tree (LRT, 1697+ taxa). The only exception is bipedal and likely digitigrade, Terrestrisuchus (Fig. 4). We don’t get another complete set of toes for testing until quadrupedal and plantigrade Protosuchus (Fig. 4), a not so basal crocodylomorph, that had the slightly more gracile digit 4 common to all extant crocs. Digit 4 does not appear to be any more gracile than the other toes in the new South Korean tracks, but let’s overlook that trifle for the moment.

Figure 2. Same feet, reordered according to the large reptile tree. Only Terrestrisuchus and Protosuchus are croc-like archosaurs here. Poposaurs are basal dinosaurs.

Figure 4. Same feet, reordered according to the large reptile tree. Only Terrestrisuchus and Protosuchus are croc-like archosaurs here.

Perhaps that is why Kim et al. write:
“Lower Jurassic Batrachopus with foot lengths (FL) in the 2–8 cm range, and Cretaceous Crocodylopodus (FL up to ~9.0 cm) (Fig. 2) known only from Korea and Spain registered narrow gauge trackways indicating semi-terrestrial/terrestrial quadrupedal gaits. Both ichnogenera, from ichnofamily Batrachopodidae, have been attributed to Protosuchus-like semi-terrestrial crocodylomorphs.”

… with a wider-gauge quadrupedal track.

On that note: The type species for Batrachopus is much smaller, fleshy, quadrupedal, narrow-gauge, with pedal impressions just behind the much smaller manus impressions.

By the start of the Cretaceous all the earlier bipedal crocodylomorphs were extinct, according to the current fossil record. Shenzhoupterus, from China, was a nearby contemporary of the South Korean trackmaker with nearly identical feet and gait. Did I hear someone say, “Occam’s Razor“? Did someone mention, “taxon exclusion”?

Earlier Kim et al. 2012 described similar tracks
as pterosaurian. Back then they were matched here to a giant Shenzhoupterus (Figs. 5–7), a coeval (Aptian, Early Cretaceous) dsungaripterid relative found in nearby China, with forelimbs less likely to reach the ground. Later a partial skeleton of a giant Late Cretaceous pterosaur from France, Mistralazhdarcho (Vullo et al. 2018), was reidentified here as a giant shenzhoupterid, rather than an azhdarchid. So shenzhoupterids were not restricted in size.

Kim et al report on, “Distinguishing crocodilian from pterosaurian trackways.”
“An unexpected result of the discovery of B. grandis trackway has been to shed light on a the controversial issue of pterosaur locomotion debated since the 1980 and 1990s: were pterosaurs bipedal or quadrupedal?

The answer is some were bipedal. Others were quadrupedal (Peters 2000, 2011, not cited by Kim et al.). It all depends on the clade and their niche.

Kim et al continue:
“These debates, mainly concerning relatively small pterosaurian tracks, have largely been resolved in favor of quadrupedalism.

Largely? Does that mean Kim et al. recognize exceptions? If so, they were not cited. More importantly, look for any other distinguishing traits in what follows from the Kim et al. text.

Kim et al continue:
“However, some uncertainty remained regarding tracks of purported ‘giant’ pterosaurians that were described as ‘enigmatic’ and inferred to have progressed bipedally (Kim et al. 2012). These trackways from the Lower Cretaceous, Haman Formation, at the Gain-ri tracksite, Korea were named Haenamichnus gainensis and inferred to represent, large, plantigrade pterodactyloid pterosaurs that might have walked bipedally so that the long wings did not become mired in the substrate. It was further inferred they may have been wading in shallow water.”

amples from the Lower Cretaceous, Gain, Korea trackway

Figure 5. Samples from the Lower Cretaceous, Gain, Korea trackway (left) along with original tracings of photos, new color tracings of photos with hypothetical digits added in red, then candidate trackmakers from the monophyletic Shenzhoupterus/Tapejarid clade.

Estimating Gain pterosaur trackmakers from track sizes and matching taxa.

Figure 6. Estimating Gain pterosaur trackmakers from track sizes and matching taxa. Note the Shenzhoupterus manus is a wee bit too short to touch the substrate as in Tupuxuara and many other derived pterosaurs.

Figure 1. Mistralazhdarcho compared to reconstructions of Shenzhoupterus and Nemicolopterus.

Figure 7. Mistralazhdarcho compared to reconstructions of Shenzhoupterus and Nemicolopterus.

Kim et al continue:
“We can now confirm confidently, that these tracks from the Gain-ri tracksite and others from Adu Island: are identical to poorly preserved large Batrachopus trackways. Thus, they should be removed from Haenamichnus and regarded as large poorly preserved batrachopodid tracks. The type specimen then tech- nically becomes Batrachopus gainensis (comb nov.). Thus, H. gainensis becomes a footnote to ichnotaxonomic history, shown to be an extramorphological expressions large of Batrachopus, only recognizable retrospectively after comparison with B. grandis. Therefore ichnologists may retrospectively choose to regard H. gainensis as a nomen dubium, and find little value in the trival name (gainensis). Alternatively they may simply refer to the Haman Formation tracks as Batrachopus cf. grandis.

Taken on its face, this is a rare instance of a paleontologist admitting a mistake. The other option is: both tracks are pterosaurian. So far, as you’ll note, the authors have not pointed to any factors, other than ‘bipedalism’, that would dissuade a pterosaurian trackmaker interpretation. I will admit and you can see (Figs. 4–5) that the pedes of Protosuchus and Shenzoupterus are rather close matches when covered with pads.

Kim et al continue:
“Note that the Gain-ri and Adu island trackways are from the Haman Formation and so these occurrences indicate a widespread distribution in space (three sites) and time (two formations) of this distinctive apparently bipedal morphotype. The pes tracks from the two Haman Formation sites are also larger (27.5–39.0 cm long), but with trackway proportions (step, stride, pace angulation etc.,) quite similar to those from the Jinju Formation.”

“The identification of the Haman Formation trackways as poorly preserved large batrachopodid tracks apparently suggests that the trackmakers habitually progressed bipedally. Alternatively the same speculative arguments for apparent rather than real bipedalism would have to be invoked as was the case with the Jinju material. Moreover, in almost all cases the trackways are very narrow gauge with a narrower straddle than seen in modern crocodylians. It is also of interest that least five subparallel more or less equally spaced trackways were registered on the level 4 surface. This suggests either that the trackmakers may have been gregarious, or that they were following a physically controlled route, such as a shoreline, defined by the paleoenvironment.”

Still no distinguishing traits, other than bipedalism, according to the authors. And note, they never considered the coeval and neighboring pterosaur, Shenzhoupterus, which is also a close match for the new tracks. They chose to invent a croc trackmaker rather than consider a pterosaurian trackmaker, evidently bowing to the consensus (their word, not mine, see above) and to follow Dr. Bennett’s curse and keep their blinders on. I wish they had dived deeper into the literature and evidence instead of following the crowd.


References
Hwang KG, Huh M, Lockley MG, Unwin DM and Wright JL 2002. New pterosaur tracks (Pteraichnidae) from the Late Cretaceous Uhangri Formation, southwestern Korea. Geology Magazine 139(4): 421-435.
Kim, JY et al. 2012. Enigmatic giant pterosaur tracks, and associated ichnofauna from the Cretaceous of Korea: implications for bipedal locomotion of pterosaurs. Ichnos 19, 50–65 (2012).
Kim KS, Lockley MG, Lim JD, Bae SM and Romilio A 2020. Trackway evidence for large bipedal crocodylomorphs from the Cretaceous of Korea. Nature Scientific Reports 10:8680 | https://doi.org/10.1038/s41598-020-66008-7
Lockley, MG et al. 2020. First reports of Crocodylopodus from Asia: implications for the paleoecology of the Lower Cretaceous.Cretaceous Research (2020) (online, March 2020).
Peters D 2000a. 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
Vullo R, Garcia G, Godefroit P, Cincotta A, and Valentin X 2018.
 Mistralazhdarcho maggii, gen. et sp. nov., a new azhdarchid pterosaur from the Upper Cretaceous of southeastern France. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1502670.

https://pterosaurheresies.wordpress.com/2012/03/25/giant-bipedal-pterosaur-tracks-from-korea/

https://pterosaurheresies.wordpress.com/2018/10/19/mistralazhdarcho-a-new-pterosaur-but-not-an-azhdarchid/

Former Gracilisuchus specimens: now closer to Trialestes

Over the last several weeks
the large reptile tree (LRT, 1660+ taxa, subset Fig. 1) was updated once again with a focus on the Crocodylomorpha. Two congeneric taxa known from a few scraps were eliminated. More insightful identification of skull bones (Figs. 1, 5) settled old issues. Over the next several posts some of the newly recovered hypothetical interrelationships will be presented for review.

We’ll start here
with a new nesting in the LRT (subset Fig. 1) for the small specimens (MCZ4116 and MCZ4118, Fig. 2) formerly assigned to Gracilisuchus (Figs. 4, 5). Now they nest either as hatchling Trialestes (Fig. 3), or, just as likely, as phylogenetically miniaturized Middle Triassic predecessors to the much larger and highly derived Late Triassic basal crocodylomorph, Trialestes. In either case, now Trialestes and its tiny doppelgänger nest together in the LRT, closer to each other than either is to any other taxon, despite a magnitude or two difference in size (Fig. 3). Gracilisuchus nests several nodes away in the next clade (Fig. 1).

Figure 1. Subset of the LRT focusing on the Crocodylomorpha, dorsal scutes, elongate proximal carpals, bipedality and clades.

Figure 1. Subset of the LRT focusing on the Crocodylomorpha, dorsal scutes, elongate proximal carpals, bipedality and clades. Images changes every 5 seconds.

Hatchling? Trialestes? (MCZ 4116, MCZ 4118, originally Gracilisuchus, Brinkman 1981; Middle Triassic; Fig. 2). These two specimens have a taller, narrow skull than Gracilisuchus (Figs. 4, 5) and a long list of other distinct traits and proportions that nest them with the very much larger Trialestes (Fig. 3) in the LRT (Fig. 1).

Figure 1. The former Gracilisuchus specimens MCZ4116 and MCZ4118 with colors added.

Figure 2. The former Gracilisuchus specimens MCZ4116 and MCZ4118 (Middle Triassic) with colors added.

Trialestes romeri (Bonaparte 1982Triassolestes (Reig, 1963/Tillyard 1918) Carnian, Late Triassic ~235 mya) is known from scattered parts here reconstructed and restored (Fig. 3). Clark, Sues and Berman (2000) redescribed the known parts and admitted the possibility that this taxon combined dinosaurian and crocodylomorph characters.

Figure 2. Trialestes reconstructed. At upper left is MCZ4116 to scale.

Figure 3. Trialestes (Late Triassic)  reconstructed. At upper left is MCZ4116 to scale.

Quadrupedal Trialestes
is indeed different than most basal bipedal crocodylomorphs (see Pseudhesperosuchus), but it has elongate proximal carpals (Fig. 3) and a long list of other croc clade traits. The elongate ilium is typical of bipedal taxa indicating a bipedal ancestry. Additional sacrals that would have filled out the sacral set between the ilia (Fig. 3) are not known, but likely were present.

Figure 4. Present reconstruction of Gracilisuchus with skull based on Romer 1971. See figure 4 for an updated on that skull.

Figure 4. Present reconstruction of Gracilisuchus with skull based on Romer 1971. See figure 4 for an updated on that skull.

In Trialestes
the vertebral centra had excavated lateral surfaces, for bird-like air sacs. The radius was longer than the humerus, a character otherwise known only in dinosaurs. The long radiale was slightly shorter than the ulnare. The fingers were tiny, another indicator of a bipedal ancestry. The pelvis was semi-perforated with a well-developed supraacetabular crest, as in basal dinosaurs. The femoral head was inturned, indicating an erect posture. The ankle joint had a crocodile normal configuration and a functionally pentadactyl pes.

Figure 5. Gracilisuchus skull updated with new colors.

Figure 5. Gracilisuchus (Middle Triassic) skull updated with new colors. Compare to figure 2.

The MCZ 4116 and MCZ 4118 specimens 
are coeval with Gracilisuchus in the Middle Triassic and similar in size, but share more traits in the LRT with highly derived Late Triassic Trialestes. As we’ve seen before, new morphologies often express their genesis in phylogenetically miniaturized taxa. That may be the case with the MCZ specimens, appearing millions of years before the much larger Trialestes. More discoveries, like an adult Trialestes in the Middle Triassic, will someday settle this ontogenetic and phylogenetic issue. This blogpost is where this issue starts. If this is not a novel hypothesis of interrelationships, let me know so I can promote the older citation.

Updates have been a continuing feature
of the LRT since its origin nine years ago, along with the steady addition of taxa to the present total of 1658 taxa, plus several hundred taxa in the pterosaur and therapsid cladograms. Correcting mistakes is standard practice in every science and every correction is another rewarding moment of discovery. Holding on to outdated and invalid hypotheses has been an acknowledged problem in paleontology.


References
Bonaparte JF 1982. Classification of the Thecodontia. Geobios Mem. Spec. 6, 99-112
Brinkman D 1981. The origin of the crocodiloid tarsi and the interrelationships of thecodontian archosaurs. Breviora 464: 1–23.
Clark JM, Sues H-D and Berman DS 2000. A new specimen of Hesperosuchus agilis from the Upper Triassic of New Mexico and the interrelationships of basal crocodylomorph archosaurs. Journal of Vertebrate Paleontology 20(4):683-704.
deFranca MAG, Bittencourt JdS and Langer MC 2013. Reavaliação taxonomica de Barberenasuchus brasiliensis (Archosauriformes), Ladiniado do Rio Grande do Sul (Zona-Assembleia de Dinodontosaurus). Palaenotogia em Destaque Edição Especial Octubro 2013: 230.
Irmis RB, Nesbitt SJ and Sues H-D 2013. Early Crocodylomorpha. Pp. 275–302 in Nesbitt, Desojo and Irmis (eds). Anatomy, phylogeny and palaeobiology of early archosaurs and their kin. The Geological Society of London. doi:10.1144/SP379.24.
Kischlat EE 2000. Tecodôncios: a aurora dos arcossáurios no Triássico. Pp. 273–316 in Holz and De Ros (eds.). Paleontologia do Rio Grande do Sul. Porto Alegre: CIGO/UFRGS.
Lecuona A, Ezcurra MD and Irmis RB 2016. Revision of the early crocodylomorph Trialestes romeri (Archosauria, Suchia) from the lower Upper Triassic Ischigualasto Formation of Argentina: one of the oldest-known crocodylomorphs. Papers in Palaeontology (advance online publication). DOI: 10.1002/spp2.1056
Reig, OA 1963. La presencia de dinosaurios saurisquios en los “Estratos de Ischigualasto” (Mesotriásico Superior) de las provincias de San Juan y La Rioja (República Argentina). Ameghiniana 3: 3-20.
Riff D et al. 2012. Crocodilomorfos: a maior diversidade de répteis fósseis do Brasil. TERRÆ 9: 12-40, 2012.
Zanno LE, Drymala S, Nesbitt SJ and Schneider VP 2015. Early Crocodylomorph increases top tier predator diversity during rise of dinosaurs. Scientific Reports 5:9276 DOI: 10.1038/srep09276.

wiki/Trialestes

Lepidosaur bipedality and pelvis morphology: Grinham and Norman 2019

Grinham and Norman 2019
brings us a new look at 34 lepidosaur pelves with an emphasis on trends associated with bipedal locomotion. The authors illustrated 11 pelves (Fig. 1, white and yellow areas).
Figure 1. On the left, lepidosaur pelves from Grinham and Norman 2019, reordered phylogenetically here. On the right several tritosaur pelves and prepubes, most of which strongly demonstrate bipedal traits (elongate anterior ilium, increased sacral number). Yellow boxes indicate facultatively bipedal extant lepidosaurs.

Figure 1. On the left, lepidosaur pelves from Grinham and Norman 2019, reordered phylogenetically here. On the right several tritosaur pelves and prepubes, most of which strongly demonstrate bipedal traits (elongate anterior ilium, increased sacral number). Yellow boxes indicate facultatively bipedal extant lepidosaurs.

From the Grinham and Norman abstract:
“Facultative bipedality is regarded as an enigmatic middle ground in the evolution of obligate bipedality and is associated with high mechanical demands in extant lepidosaurs. Traits linked with this phenomenon are largely associated with the caudal end of the animal: hindlimbs and tail. The articulation of the pelvis with both of these structures suggests a morphofunctional role in the use of a facultative locomotor mode. Using a three-dimensional geometric morphometric approach, we examine the pelvic osteology and associated functional implications for 34 species of extant lepidosaur. Anatomical trends associated with the use of a bipedal locomotor mode and substrate preferences are correlated and functionally interpreted based on musculoskeletal descriptions. Changes in pelvic osteology associated with a facultatively bipedal locomotor mode are similar to those observed in species preferring arboreal substrates, indicating shared functionality between these ecologies.”
Unfortunately, Grinham and Norman omitted
tritosaur lepidosaurs from their study. In the Triassic many of them became bipeds and among these, pterosaurs achieved bipedalism supported with four, five and more sacral vertebrae between horizontally elongate ilia, convergent with dinosaurs. The addition of the prepubis virtually extended the anchorage for the puboischial muscles. After achieving flight, beach-combing pterosaurs reverted to a quadrupedal configuration with finger 3 pointing posteriorly. Giant Korean bipedal pterosaur tracks are best matched to large dsungaripterid/tapejarid clade taxa.
Unfortunately, Grinham and Norman reported,
“A recently published molecular-based time-calibrated phylogeny for Squamata was pared down to match the species in our dataset.” Their genomic cladogram bears little to no resemblance to the large reptile tree (LRT, 1635+ taxa), which tests traits, not genes. Once again, genes produce false positives. 
The authors’ principal component analysis of the pelvis failed 
to isolate bipedal lepidosaurs from the rest. Grinham and Norman reported, “The shape of the pelvis in facultatively bipedal extant lepidosaurs falls within the overall morphospace of lepidosaurs generally.” This is also visible in their illustrated pelves (Fig. 1). They also reported, However, it is generally found in a very concentrated area of that morphospace.” And Conclusions can be drawn regarding pelvic morphology and substrate use, although not with the same clarity as for locomotor mode.”
Grinham and Norman 2019 conclude,
“we have used 3D landmark-based geometric morphometrics to demonstrate that the overall morphospace for the lepidosaur pelvis is broad and wide-ranging. Within this overall morphospace, a small region is occupied by facultative bipeds. The vast majority of this smaller morphospace overlaps that occupied by species that show a preference for arboreal habitats. Pelvic morphological adaptations relevant for living in an arboreal environment are similar to those necessary to facilitate facultative bipedality.”
That’s interesting with regard to
the arboreal abilities of volant basal bipedal pterosaurs and their ancestors. Maybe next time Grinham and Norman will expand their study to include tritosaur lepidosaurs.

References
Grinham LR and Norman DB 2019. 
The pelvis as an anatomical indicator for facultative bipedality and substrate use in lepidosaurs. Biological Journal of the Linnean Society, blz190 (advance online publication) doi: https://doi.org/10.1093/biolinnean/blz190
https://academic.oup.com/biolinnean/advance-article-abstract/doi/10.1093/biolinnean/blz190/5687877Â
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Snyder RC 1954. The anatomy and function of the pelvic girdle and hind limb in lizard locomotion. American Journal of Anatomy 95:1-46.

Pterosaur prebubis

 

‘Prehistoric Life – Animated size comparison’ on YouTube

Figure 1. Click to enlarge. Pteranodon scene from Prehistoric Life video from Dane Pavitt. Incredible, excellent video, hearkening back to Giants of Land, Sea & Air - Past & Present (Peters 1986). Just a tweak or two necessary for the included Pteranodon. Extend those metacarpals and elevate that stance!

Figure 1. Click to enlarge. Pteranodon scene from Prehistoric Life video from Dane Pavitt. Incredible, excellent video, hearkening back to Giants of Land, Sea & Air – Past & Present (Peters 1986). Just a tweak or two necessary for the included Pteranodon. Extend those metacarpals and elevate that stance!

Another incredible YouTube video from animator Dane Pavitt!
Click below to view both of them.

I’m just nit-picking here…
In Dane Pavitt’s Pteranodon scene just a tweak or two is necessary to match the otherwise excellent presented data. Elongate those metacarpals and elevate that stance, as shown by the added Pteranodon data (Fig. 2). The small medial fingers, alas, could not contact the substrate (given available data), but this is one instance in which, perhaps, the big wing finger could. More likely Pteranodon was bipedal, only resting on its big wings.

Post-crania Pteranodon

Figure 2. Click to enlarge. Various Pteranodon specimens known from post-crania. Note the yellow box includes one of the largest specimens, but it has an unfused extensor tendon process, which may mean it is a very large Nyctosaurus with fingers.

Remember,
pterosaurs were bipeds originally and often. Typically pterosaur beach-combers and waders made quadrupedal tracks. They had different proportions. We have  bipedal tracks for the germanodactylid ancestors of Pteranodon.

Earlier (March 2016) Dane Pavitt premiered
an incredible march of dinosaurs video (click to view below) now with 17+ million views.

I’m delighted to see these videos
continuing and expanding in action and scope a concept presented in book form over 30 years ago (Peters 1986). I wonder if Dane Pavitt had a copy as a child.

References
Peters D 1986. Giants of Land, Sea & Air – Past & Present. A. Knopf. Click here to view.

Figure 1. The cover of Giants, the book that launched my adult interest in dinosaurs, pterosaurs and everything inbetween.

Figure 3. The cover of Giants, the book that launched my adult interest in dinosaurs, pterosaurs and everything in-between. Click to view and/or download the book.

Looking for a vestigial toe 5 on Jeholosaurus

Jeholosaurus is a small Early Cretaceous sister
to the Late Jurassic Chilesaurus and Late Triassic Daemonosaurus. All three nest as basalmost Ornithischia in the large reptile tree (LRT, 1399 taxa).

Phylogenetic bracketing indicates
a likely pedal digit 5 with a few phalanges should be found on all three taxa. Prior studies failed to reveal it. Current data does not include the pes for Daemonosaurus, nor show the ventral aspect of Chilesaurus, but Jeholosaurus does present the view we’re looking for (Fig. 1). I failed to notice pedal 5 before. I think others have overlooked it as well. Here it is:

Figure 1. Jeholosaurus pes in ventral aspect. DGS colors identify parts of pedal digit 5 disarticulated and broken on the sole of the foot and reconstructed at right.

Figure 1. Jeholosaurus pes in ventral aspect. DGS colors identify parts of pedal digit 5 disarticulated and broken on the sole of the foot and reconstructed at right. This observation is awaiting confirmation or refutation. Phylogenetic bracketing indicates this foot had a pedal digit 5 in vivo.

Finding pedal digit 5 on Jeholosaurus
was made a bit more difficult due to the vestige nature of the digit and its crushed and broken pieces, disarticulated from its traditional alignment lateral to pedal digit 4. This observation based on this photo awaits confirmation or refutation.


References
Han F-L, Barrett PM, Butler RJ and Xu X 2012. Postcranial anatomy of Jeholosaurus shangyuanensis (Dinosauria, Ornithischia) from the Lower Cretaceous Yixian Formation of China. Journal of Vertebrate Paleontology 32 (6): 1370–1395.
Xu X, Wang and You 2000. A primitive ornithopod from the Early Cretaceous Yixian Formation of Liaoning. Vertebrata PalAsiatica 38(4:)318-325.

wiki/Jeholosaurus
wiki/Daemonosaurus

 

 

Pelecanimimus joins the LRT

Yes, it is the basalmost ornithomimosaur,
(of three tested), but from whence did the theropod dinosaur, Pelecanimimus (Figs. 1-3), arise?

Figure 1. Rough tracing and reconstruction of Pelecanimimus based on low rez photos from 1994 paper.

Figure 1. Rough tracing and reconstruction of Pelecanimimus based on low rez photos from 1994 paper.

 

In the original paper
Pérez-Moreno et al. 1994 tested only Allosaurus, Albertosaurus, Deinonychus and Troodontidae in order of decreasing distance as outgroup taxa to Pelecanimimus + Ornithomimosauria using 22 characters. In the early days of PAUP this is all that most workers did back then… sort of testing the phylogenetic waters.

In a competing study
the large reptile tree (LRT) tests 1370+ taxa and recovers the holotype of Compsognathus as the proximal outgroup. In the same study members of the Troodontidae nest closer to birds (birds nest within the clade that includes some traditional troondontids, but not others).

Unique indeed…
The long down-curved jaws of Pelecanimimus are not found in either ancestral compsognathids nor descendant ornithomimosaurs. The wrist appears to be made of tiny bones, capable of minimal movement. ‘On the other hand’ the fingers are provided with large cylindrical joints for substantial flexion and extension.

Figure 2. DGS tracings from 1994 paper focusing on skull and manus of Pelecanimimus.

Figure 2. DGS tracings from 1994 paper focusing on skull and manus of Pelecanimimus.

A gular sac and cranial soft tissue are present
on the specimen. Not sure if we’re seeing radiating patterns of soft tissue aft of the ulna, or are those preparator chisel marks? Nothing glows in the UV image (Fig. 1), so let’s go with the latter.

Figure 4. Pelecanimimus to scale with Struthiomimus and Compsognathus.

Figure 3. Pelecanimimus to scale with Struthiomimus and Compsognathus.

References
Pérez-Moreno BP et al. (5 co-authors) 1994. A unique multi-toothed ornithomimosaur dinosaur from the Lower Cretaceous of Spain. Nature 370(4):363–367.

wiki/Pelecanimimus

A fourth Langobardisaurus: Saller et al. 2013

Not sure how I missed this five years ago,
knowing my fondness and fascination with the Tritosauria. I learned about the following paper while reading Franco Saller’s doctoral thesis on Macrocnemus and its allies. (More on this later).

Saller et al. 2013
describe a fourth Langobardisaurus (Late Triassic, Norian; Figs. 1-2; P10121), wrongly described as a protorosaurian reptile. Langobardisaurs are tritosaur lepidosaurs in the large reptile tree (LRT, 1326) which tests and includes more taxa.

Figure 1. Langobardisaurus #4, P10121, in situ with bones identified using the DGS method. Reconstruction in figure 2.

Figure 1. Langobardisaurus #4, P10121, in situ with bones identified using the DGS method. Reconstruction in figure 2. Note the sprawling lepidosaur femora. The pectoral girdle is shown in situ. Colors match reconstruction in figure 2.

Saller et al. report: “Reappraisal of all the specimens assigned to the genus Langobardisaurus reveals no significant differences between L. pandolfii and L. tonelloi, allowing to consider the latter as a junior synonym of the former.” I haven’t tested more than one Langobardisaurus in phylogenetic analysis…yet… but I will as I wonder about the validity of this Saller et al. conclusion, which does not appear to be validated given the variety present in these three reconstructions (Fig. 2).

Addendum December 4, 2018:
I just added three new Langobardisaurus specimens to the LRT. The P10121 specimen is basal, nesting between the small Macrocnemus BES SC111 specimen and Cosesaurus, but definitely in the lineage of derived langobardisaurs and having a few derived traits itself. The Langobardisaurus holotype MCSNB 2883 splits next. The MFSN 1921 specimen nests with the MCSNB 4860 specimen (Fig. 2). 

Figure 1. Four Langobardisaurus specimens compared to scale. Contra Saller et al. 2013, these four specimens do not appear to be conspecific.

Figure 2. Four Langobardisaurus specimens compared to scale. Contra Saller et al. 2013, these four specimens do not appear to be conspecific.

Historically,
Langobardisaurus was the first specimen in which tracing elements in a photo using a mouse on a computer monitor revealed more than was observed firsthand and published in the original paper. Specifically the overlooked skull and cervicals were traced hiding beneath the torso (Fig. 3).

Langobardisaurus pandolfi

Figure 3. Langobardisaurus pandolfi referred specimen, MCSNB 4860.

The Langobardisaurus pectoral girdle
is transitional between the walking morphology of HuehuecuetzpalliMacrocnemus and flapping morphology of Cosesaurus (Fig. 4), as we learned earlier here. The P10121 specimen exposes the wide sternum, strap-like scapulae, disc-like coracoids and cruciform interclavicle first seen in L. tonneloi (Figs. 4, 5).

Three pectoral girdles demonstrating the evolution of the elements from the plesiomorphic basal lizard, Huehuecuetzpalli through Langobardisaurus tonelloi to the basal fenestrasaur, Cosesaurus.

Figure 4. Three pectoral girdles demonstrating the evolution of the elements from the plesiomorphic basal lizard, Huehuecuetzpalli through Langobardisaurus tonelloi to the basal fenestrasaur, Cosesaurus.

Bipedal Langobardisaurus
Like aquatic Tanystropheus and flapping Cosesaurus, Langobardisaurus was often bipedal, using its long neck as a survival advantage. Like Cosesaurus, this specimen of Langobardisaurus has prepubes (Fig. 6), which add femoral muscle anchors to the pelvis.

Figure 5. Pectoral girdle of the fourth Langobardisaurus in situ. Blue-scapulae. Yellow-sternum. Tan-interclavicle. Violet-coracoid. Green-humerus.

Figure 5. Pectoral girdle of the fourth Langobardisaurus in situ. Blue-scapulae. Yellow-sternum. Tan-interclavicle. Violet-coracoid. Green-humerus.

Figure 6. Pelvic area in the fourth Langobardisaurus. Cyan-ischia. Deep green-pubes. Indigo-prepubes. Red-sacrals. Tan-ilia.

Figure 6. Pelvic area in the fourth Langobardisaurus. Cyan-ischia. Deep green-pubes. Indigo-prepubes. Red-sacrals. Tan-ilia. Also note the feathery soft tissue in orange and lime yellow. For those interested in the DGS method, this is how it works.

Figure 7. Fourth Langobardisaurus reconstruction.

Figure 7. Fourth Langobardisaurus P10121 reconstruction based on DGS tracings in figure 1.

References
Muscio G 1997. Preliminary note on a specimen of Prolacertiformes (Reptilia) from the Norian (Late Triassic) of Preone (Udine, north-eastern Italy). Gortania – Atti del Museo Friulano di Storia Naturale 18:33-40.
Renesto S 1994. A new prolacertiform reptile from the Late Triassic of Northern Italy. Rivista di Paleontologia e Stratigrafia 100(2): 285-306.
Renesto S and Dalla Vecchia FM 2000. The unusual dentition and feeding habits of the Prolacertiform reptile Langobardisaurus (Late Triassic, Northern Italy). Journal of Vertebrate Paleontology 20: 3. 622-627.
Renesto S and Dalla Vecchia FM 2007. A revision of Langobardisaurus rossii Bizzarini and Muscio, 1995 from the Late Triassic of Friuli (Italy)*. Rivista di Paleontologia e Stratigrafia 113(2): 191-201. online pdf
Renesto S, Dalla Vecchia FM and Peters D 2002. Morphological evidence for bipedalism in the Late Triassic Prolacertiform reptile Langobardisaurus. Senckembergiana Lethaea 82(1): 95-106.
Saller F, Renesto S and Dalla Vecchia FM 2013. First record of Langobardisaurus (Diapsida, Protorosauria) from the Norian (Late Triassic) of Austria, and a revision of the genus. Neues Jahrbuch für Geologie und Paläontologie 268(1):83–95.
Wild R 1980. Tanystropheus (Reptilia: Squamata) and its importance for stratigraphy. Mémoires de la Société Géologique de France, N.S. 139:201–206.

uninisubria/Langobardisaurus
wiki/Langobardisaurus
http://reptileevolution.com/langobardisaurus.htm

SVP 2018: Junggarsuchus µCT scans

Ruebenstahl and Clark 2018
pull new data from the basalmost crocodylomorph, Junggarsuchus (Fig. 1) using µCT scans. They consider it a sphenosuchian nesting uneasily deep within Crocodylomorpha. I hope they test it with basal bipedal crocs listed in the large reptile tree (LRT, 1315 taxa, subset Fig. 3). PVL 4597 is a LRT sister that will provide clues to the hind quarters of Junggarsuchus, currently missing.

Figure 8. The CAPPA specimen of Buriolestes compared to the more primitive Junggarsuchus, basal to the other branch of archosaurs, the crocs.

Figure 1 The CAPPA specimen of Buriolestes (a dinosaur) compared to the more primitive Junggarsuchus, basal to the other branch of archosaurs, the crocs.

The authors report, “In addition to braincase characters, we also identify a unique morphology in the palate and pterygoid of Junggarsuchus, which, although similar to the condition in other sphenosuchians, has several aspects that are unlike anything reported in any ‘sphenosuchians’, including a far reaching anterior process of the pterygoid.” A similar pterygoid is found in the basal dinosaur, Herrerasaurus (Fig. 2) and the poposaur, Silesaurus.

Figure 1. The basalmost dinosaur, Herrerasaurus. Note the palate and the long pterygoid.

Figure 2. The basalmost dinosaur, Herrerasaurus. Note the palate and the long pterygoid.

Ruebenstahl and Clark 2018
provide no indication that they understand the close relationship of Junggarsuchus to basal dinosaurs, basal poposaurs and Decuriasuchus. If the authors only see croc interrelationships it’s time to add taxa.

Figure 2. Subset of the LRT focusing on Crocodylomorpha (basal Archosauria) including Armadillosuchus.

Figure 3. Subset of the LRT focusing on Crocodylomorpha (basal Archosauria) including Armadillosuchus.

References
Ruebenstahl AA and Clark JM 2018. Junggarsuchus sloani: a transitional ‘sphenosuchian’ and the evolution of the crocodilian skull.” SVP abstracts.

SVP 2018: Study says: Hatchling Massospondylus a likely biped

Earlier we looked at a Massospondlylus embryo and a reconstruction that appeared to be quadrupedal based on various limb and torso proportions (Fig. 1).

FIgure 1. Massospondylus embryo in situ and reconstructed.

FIgure 1. Massospondylus carinatus embryo in situ and reconstructed.

Chapelle et al. ((3 co-authors) 2018 report,
“Our results clearly show that M. carinatus was a biped from hatching, and possessed bipedal skeletal proportions even in ovo.”

This is a judgement call. Up to you.

References
Chapelle KE, et al. 2018. Locomotory shfits in dinosaurs during ontogeny. SVP abstracts.