Scapulocoracoid and humerus ‘assigned’ to Lagerpeton might belong to Procompsognathus

McCabe and Nesbitt 2021
assigned a disarticulated Late Triassic scapulocoracoid and humerus (MCZ 101542) to Lagerpeton (Fig. 1) in the absence of any pervious similar bones for the Lagerpeton holotype.

Gutsy.
Workers have been trying to rebuild a chimaera of Lagerpeton from disassociated parts for several years now, hoping it will somehow shed some insight into dinosaur and pterosaur origins.

This is all for naught because Lagerpeton is a bipedal chanaresuchid that ran on two toes, not an archosaur (dinosaurs + crocs) or fenestrasaur (pterosaurs and their ancestors).

Figure 1. Tropidosuchus and Lagerpeton compared to the new material (MCZ 101542).

How can McCabe and Nesbitt assign that pectoral girdle?
The holotype of Lagerpeton lacks any pectoral girdle material. So we can only imagine missing elements based on phylogenetic bracketing and comparative anatomy.

Figure 2. MCZ 101542 scapulocoracoid and humerus compared to Dromomeron humerus.

Given that,
does the MCZ 101542 material closely resemble comparable bones in closely related taxa? In the large reptile tree (LRT, 1810+ taxa) Lagosuchus nests with Tropidosuchus (Fig. 1), not with dinosaurs or pterosaurs.

A problem arises.
Tropidosuchus (Fig.1) has a larger, hourglass-shaped scapula with a short ‘waist’. By contrast the MCZ 101542 scapula (Fig. 1) has a smaller, straighter, narrower, more rectangular shape. So, maybe we should look for a better match… if there is one.

Figure 2. MCZ 101542 compared to Marasuchus and Lagosuchus.

Is material from another taxon a little more similar?
Marasuchus (Fig. 2; PVL 3871) has a more robust, but otherwise similarly straight scapulocoracoid with a dinosaurian deltopectoral crest located about a third the way down the slender humerus, and more similar in scale. Lagosuchus (Fig. 2; UPLR 090) has a similarly gracile scapulocoracoid (at least what’s left of it). It’s all iffy.

McCabe and Nesbitt also make comparisons
when they note, “Compared to Lagosuchus talampayensis (PVL 3871), the scapular blade of MCZ 101542 is much more strap-like (near parallel anterior and posterior side) and the distal end expands more in Lagosuchus talampayensis.” 

Their table 2 lists ‘species’ Marasuchus‘ with specimen number PVL 3871. So their Marasuchus (PVL 3871) is not Lagosuchus (UPLR 090; Fig. 2).

McCabe and Nesbitt also write
“The glenoid of MCZ 101542 is directed posteroventrally like that of other avemetatarsalians (e.g., lagerpetids, Lagosuchus talampayensis, silesaurids, dinosaurs).”

In the LRT Avemetatarsalia is a junior synonym for Reptilia because it also include pterosaurs. Lagerpetids are proterochampsids, not dinosaur relatives. And, once again the authors’ Table 2 does not match their text with regard to nomenclature and specimen numbers.

Figure 3. Ixalerpeton compared to MCZ 101542.

The protorosaur, Ixalerpeton, 
(Fig. 3) is similar in size to MCZ 101542, but the shapes are slightly different.

The authors note,
“Within Lagerpetidae, the humerus of Ixalerpeton polesinensis (ULBRA-PVT059) is more robust than MCZ 1010541 (Fig. 4), with proportionally much larger proximal and distal expansions. The proportions of the humerus of Lagosuchus talampayensis (PVL 3871) matches that of MCZ 101541, with overall weakly expanded articular ends.”

Would you like to see a ‘Hail Mary’ pass based on taxon exclusion?
The authors report, “Overall, the gracile proportions of MCZ 101541 (= MCZ 101542 = the humerus) are unlike early archosaurs and their close relatives.”

When workers give up like this,
it’s usually due to taxon exclusion, whether intentional or not.

Figure 4. Procompsognathus has proportions that precisely fit the MCZ 101542 material.

 

In this case there is a close match for the gracile proportions
of MCZ 101542 and it comes from a taxon that happens to be missing the scapulocoracoid and humerus, the Late Triassic theropod from Germany, Procompsognathus (Fig. 4), a taller relative of Marasuchus in the LRT. Like a lock and a key, a Yin and a Yang, the MCZ material is a perfect fit including the narrow, but deep anterior torso required to fit the narrow but deep scapula and coracoid. The authors did not mention Procompsognathus. So taxon exclusion continues to be a problem here. If inappropriate, at least it should have been considered and eliminated.

Still, this is only a gutsy guess.
See how reconstructions can help?

The LRT uses more complete taxa
whenever possible. To assign two bones to a specific genus is getting close to “Pulling a Larry Martin.” Be careful when you go there. It’s worth a shot (Fig. 4), but it’s easy to be wrong.

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References
McCabe MB and Nesbitt SJ 2021. The first pectoral and forelimb material assigned to the lagerpetid Lagerpeton chanarensis (Archosauria: Dinosauromorpha) from the upper portion of the Chañares Formation, Late Triassic. Palaeodiversity, 14(1) : 121-131.

wiki/Procompsognathus

SVP abstracts – First largepetid pectorals and forelimbs

McCabe and Nesbitt 2019 present
the first pectorals and forelimbs for Lagerpeton (Fig. 1), a taxon previously known from hind limbs and pelvic region, plus some dorsals, some caudal vertebrae only.

From the abstract:
“The posture of the earliest dinosaurs is thought to be bipedal whereas their
pseudosuchian relatives and stem archosaurs are thought to be typically quadrupedal.”

The large reptile tree (LRT, 1592 taxa) invalidates the traditional clade ‘pseudosuchia.’ All basal archosaurs are bipeds in the LRT. So are some tropidosuchids by convergence. Nesbitt has never tested a large enough taxon list to reveal this. He and others have been traditionally confused by this convergence.

“Therefore, the transition from quadrupedality to bipedality lies somewhere between the origin of Avemetatarsalia (bird-line archosaurs) and Dinosauria.”

The LRT invalidates the traditional clade Avemetatarsalia and shows exactly where quadrupeds became bipeds.

“However, studying this transition is hampered by the lack of forelimb fossils from many of the close relatives of dinosaurs and it is not clear if the morphology of the few dinosauromorphs that have forelimb material are unique or represent the plesiomorphic condition leading to dinosaurs.”

The LRT showed back in 2011 that Lagerpeton is a dinosaur mimic, related to the proterochampsid (Fig. 2) Tropidosuchus, not dinosaurs. So the premise of this abstract is completely wrong, based on invalid Nesbitt 2011 cladogram.

“New forelimb fossils of dinosaur relatives and careful assessments of their osteology is sorely needed to help address this knowledge gap.

We have forelimbs for dinosaur relatives. Pseudhesperosuchus is close. So is Turfanosuchus. We’re glad to see forelimbs for Lagerpeton. Just don’t imagine that they have anything to do with the origin of dinosaurs.

“Here we present the first pectoral (left scapulocoracoid) and forelimb (right humerus) bones of the important early dinosauromorph Lagerpeton chanarensis.”

Not a dinosauromorph.

“The bones were prepared from a concretion that only consisted of Lagerpeton bones and from the cynodont Massetognathus. We identify the bones as belonging to Lagerpeton because the distal end of the femur possesses an inflated crista tibiofibularis – a lagerpetid character state – and the newly recognized pectoral and forelimb bones are generally similar to those of the lagerpetid Dromomeron romeri and Ixalerpeton with tall and
constricted anteroposteriorly narrow scapular blade and a humerus with a highly asymmetrical proximal part of the humerus.”

Sounds good.

Figure 1. The closest kin of Tropidosuchus are the much larger Chanaresuchus (matching Nesbitt 2011) and the smaller Lagerpeton.

McCabe and Nesbitt continue:

“The scapulocoracoid of Lagerpeton has a tall, but anteroposteriorly narrow scapular blade more like Dromomeron romeri than Ixalerpeton.

And more like the omitted Tropidosuchus (based on the above description). McCabe, Nesbitt: why not test Lagerpeton against Tropidosuchus? Novas and Agnolin reported it as a proterochampsian, too. BTW, Ixalerpeton is a protorosaur in the LRT, based on the few bones known.

“The length of humerus and the proportions of the proximal and distal end in Lagerpeton are also more similar to that of Dromomeron romeri. Overall, the scapulocoracoids and humeri of lagerpetids are similar in proportion across taxa, but comparing the length of the forelimbs to the hindlimbs is hampered by the lack of articulated or unambiguously associated individuals of any member of the group. Currently, it is still not clear if the anatomy of the pectoral girdle and forelimb of lagerpetids, and thus posture, is unique for lagerpetids or represents the ancestral condition for dinosauromorphs.”

This pectoral girdle does not represent the ancestral condition for dinosauromorphs. Nor is it unique to lagerpetids (sans Tropidosuchus). McCabe, Nesbitt, look at Tropidosuchus before pushing your hypothesis over the edge.

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References
McCabe MB and Nesbitt SJ 2019. The first pectoral and forelimb material assigned to the lagerpetid Lagerpeton chanarensis: comparing to other lagerpetids and other avemetatarsalians. Journal of Vertebrate Paleontology abstracts.

Novas FE and Agnolin FL 2016 Lagerpeton chanarensis Romer (Archosauriformes): A derived proterochampsian from the middle Triassic of NW Argentina. Simposio. From Eventos del Mesozoico temprano en la evolución de los dinosaurios”. Programa VCLAPV. Conferencia plenaria: Hidrodinámica y modo de vida de los primeros vertebrados. Héctor Botella (Universitat de València, España) 2016

A unique Late Triassic dinosaur assemblage

Cabreria et al. 2016
bring us two new taxa, Ixalerpeton and Buriolestes from the Late Triassic. Originally considered a lagerpetid and a carnivorous sauropodomorph. “This is the first time nearly complete dinosaur and non-dinosaur dinosauromorph remains are found together in the same excavation, clearly showing that these animals were contemporaries since the first stages of dinosaur evolution.”

Figure 1. Ixalerpeton bones (above) as originally reconstructed (below) and a new reconstruction (middle) as a protorosaur with a small scapula, as in Malerisaurus, and short cervicals, as in Boreopricea.

Ixalerpeton polesinensis
(ULBRA-PVT059) was originally considered a laterpetid (close to Lagerpeton, which they considered a dinosauromorph), but distinct from Lagerpeton in several ways. The large reptile tree (LRT) nests Ixalerpeton among the basal protorosaurs. Protorosaurs were not part of the original inclusion set presented by Cabreira et al., so taxon exclusion may be an issue here. As in the protorosaur, Malerisaurus, the scapula was not large in Ixalerpeton. As in another protorosaur, Boreopricea, the cervicals were not elongated.

Cabreira et al. report
“The parietal and frontal bones of Ixalerpeton polesinensis form a skull roof broader than that of most early dinosaurs. A large postfrontal fits laterally to the frontal, as more common to non-archosaur archosauromorphs.” In other words, these are clues that the inclusion set needs to be expanded. Taking a look at the pelves of candidate sisters provides some clues to the affinities of Ixalerpeton, but, of course, all the traits count.

Figure 2. Ixalerpeton pelvis compared to Lagerpeton, Tropidosuchus, Chanaresuchus, Prolacerta and the SAM K 7710 specimen of Youngina. The latter two are taxa that frame Ixalerpeton in the LRT. No perfect matches here, but the vertical pubis on two of them match them.

Buriolestes schultzi
(ULBRA-PVT280) was originally considered a carnivorous basal sauropodomorph. Several cladograms were presented based on the addition of these taxa to prior analyses. The LRT nests Buriolestes with the basal theropod, Tawa, which was part of their analyses, but none of their topologies match the topology of the LRT, in many regards based on taxon exclusion.

Figure 2. Buriolestes reconstructed along with skeletal elements, some of which have been colorized for segregation.

Cabreira et al. report
“Buriolestes schultzi corresponds to a sauropodomorph dinosaur, as indicated by

1. a mandible tip with a ventrally inclined dorsal surface
2. a deltopectoral crest that extends for more than 40% of the humeral length.”

Drawings of Tawa (Fig. 4) indicate a straight or elevated mandible tip, but the fossil has a ventrally inclined dorsal surface.

Indeed Tawa does not have a 40% deltopectoral crest, but it also does not have a reduced antebrachium. Similarly in T. rex, Segisaurus and other reduced forelimb theropods the deltopectoral crest extends relatively further down the short humerus.

Figure 4. Skull of Tawa. Note the descending mandible tip not reflected in the drawing.

The Cabreira et al. study finds:

1. Dinosauromorpha is composed of Lagerpetidae and Dinosauriformes. (but see this recent post in which Novas and Agnolin 2016 nest Lagerpeton with Tropidosuchus in the Chanaresuchidae)
2. Lagerpetidae is composed of Lagerpeton, Ixalerpeton, and Dromomeron. (but see above)
3.  Ixalerpeton and Dromomeron are sister taxa. (not when tested with protorosaurs)
4. Dinosauriformes includes Marasuchus and a clade with all other members of the group. (Marasuchus nests with a clade of theropods that are not often included in analyses in the LRT.
5. Saltopus, Lewisuchus, and Pseudolagosuchus form a polytomy with Dinosauria. (additional taxa in the LRT disrupt this polygamy and other taxa nest as outgroups to Dinosauria).
6. Dinosauria of composed of the Saurischia and Orithischia lineages. (in the LRT the division is between Theropoda and Phytodinosauria).
7. Asilisaurus is the sister group of all the other ornithischians, including Silesauridae. (in the LRT Asilisaurus and Silesaurus are poposaurs, not related to ornithischians.)
8. Silesauridae is composed of Eucoelophysis, Silesaurus, Sacisaurus, and Diodorus. (only Silesaurus and Sacisaurus are tested in the LRT)
9. Silesauridae is the sister-clade of the group composed of broadly accepted ornithischians. (not in the LRT)
10.  Herrerasauria is the sister group to all other saurischian dinosaurs. (in the LRT, all other dinosaurs)
11.  Herrerasauridae is composed of Staurikosaurus, Herrerasaurus, and Sanjuansaurus. (not in the LRT where Staurikosaurus is close, but at the base of the Marasuchus clade at the base of the Theropoda)
12.  Herrerasaurus and Sanjuansaurus are sister taxa (not tested in the LRT)
13.  Tawa and Chindesaurus are sister taxa. (not tested in the LRT)
14.  Guaibasaurus, Eodromaeus, Tawa + Chindesaurus, and Daemonosaurus are saurischians belonging neither to Theropoda nor to Sauropodomorpha (i.e. non-Eusaurischia). (in the LRT Daemonosaurus nests at the base of the Ornithischia.)
15. Eusaurischia is composed of the theropod and sauromopodorph branches. (paraphyletic in the LRT)
16. Buriolestes is the sister group of all other sauropodomorphs. (nests with the basal theropod Tawa in the LRT)
17. Eoraptor is the sister group of all other sauropodomorphs with the exception of Buriolestes. (Eoraptor is close to the base of the Phytodinosauria in the LRT).
18. Pampadromaeus is the sister group of Panphagia, Saturnalia + Chromogisaurus, and all other sauropodomorphs. (confirmed in the LRT, but Pampadromaeus is also the sister group of the Ornithischia in the LRT)

References
Cabreira SF et al. (13 authors) 2016. A unique Late Triassic dinosauromorph assemblage reveals dinosaur ancestral anatomy and diet. Current Biology (2016), http://dx.doi.org/10.1016/j.cub.2016.09.040

You heard it here first: Lagerpeton is NOT a dinosauromorph

Thanks to Dr. Max Langer
for sending this abstract.

Five years after
Lagerpeton was removed from the Dinosauromorpha online here, Novas and Agnolin 2016 follow suit by nesting Lagerpeton with Tropidosuchus, among the Proterochampsidae.

This is confirmation of methodology
and the value of a large gamut analysis in reducing a priori bias and the influence of paradigm. You don’t have to see the fossil firsthand to make a contribution to paleontology. The Science is in the testing of heretical hypotheses. The Pseudoscience is in the critical blackwashing of results without testing.

Not sure how the critics will take this news.
I know they hate it every time testing reveals something that is not in their paradigm.

From the Novas and Agnolin 2016? abstract
“The relationships of basal ornithodirans [1] constitute a hotly debated topic of vertebrate evolution. Among one of the most important basal ornithodirans is the enigmatic Lagerpeton chanarensis, coming from the Middle Triassic Los Chañares Formation, Talampaya National Park, La Rioja Province, Argentina. With the aim to evaluate the phylogenetic position of this taxon, a detailed comparison with other Triassic archosauriforms was conducted. Surprinsingly, extensive similarities between Lagerpeton and proterochampsids, particularly Tropidosuchus, were found. Because of that, an integrative phylogenetic analysis including Lagerpeton and several archosauriform clades was constructed. The analysis resulted in the recognition of Lagerpeton as a basal archosaurifom nested within Proterochampsidae, and nearly related to the genus
Tropidosuchus.

“Lagerpeton resembles proterochampsids in several derived features, including 1) proximal pubis with robust ambiens process; 2) lateral margin of pubis sigmoid in anterior view; 3) acetabulum cup-like and ellipsoidal shaped; 4) transverse processes on caudal vertebrae long and narrow; 5) femoral 4th trochanter proximodistally expanded; 6) caudal surface of distal tibia with a middle tubercle surrounded by two shallow concavities; 7) astragalus with anteromedial corner acute; and 8) metatarsal II tranversely thick. Furthermore, Lagerpeton and Tropidosuchus share elongate and compact metatarsus with metatarsal V reduced and devoid of phalanges, and with articular surface for distal tarsal 4 subparallel to the longitudinal axis of shaft, and metatarsal IV longer than III. In spite of the similarities noted above, Lagerpeton differs from proterochampsids and resembles dinosauriforms in having a well-defined and proximally convex femoral head, and absence of osteoderms.

“Previous authoritative papers by J. Bonaparte and P. Sereno and A. Arcucci have illustrated the hindlimbs of Lagerpeton as vertically positioned. However, manual articulation of the femoral head within the deep and elliptical-shaped acetabulum avoids a parasagittal position of the entire hindlimb. On the contrary, the most unforced position of the hindlimbs in Lagerpeton depicts its femora in a sprawling posture. In this position, distal femoral condyles orientate almost ventrally to articulate with tibia and fibula. In lateral view, the articulated hindlimb is oblique, being subhorizontally oriented. In these respects, Lagerpeton resembles basal archosauriforms, including proterochampsids, but differs from the parasagittal posture of ornithodirans.

“The exclusion of Lagerpeton from the dinosaur lineage results in the removal of the clade Dinosauromorpha, [2, 3] which was originally conceived to encompass Lagerpeton plus Dinosauriformes. The recognition of Lagerpeton as a derived proterochampsian widens the morphological radiation that this clade of basal archosauriforms manifested during mid-Triassic times.”

Notes

1. Ornithodira is still an invalid clade encompassing pterosaurs and dinosaurs and their kin, which, in the LRT, encompasses all Reptilia.
2. We may want to resurrect a clade name for the archosaur outgroups to the Dinosauria listed here and discussed and illustrated here and here.
3. Dinosauromorpha was also removed here five years ago.

References
Novas FE and Agnolin FL 2016 Lagerpeton chanarensis Romer (Archosauriformes): A derived proterochampsian from the middle Triassic of NW Argentina. Simposio. From Eventos del Mesozoico temprano en la evolución de los dinosaurios”. Programa VCLAPV. Conferencia plenaria: Hidrodinámica y modo de vida de los primeros vertebrados. Héctor Botella (Universitat de València, España) 2016

Lagerpeton: foot configurations modeled in cardboard

Earlier discussions about the pes of Lagerpeton and the ichnite it would have produced inspired these tests. Here a cardboard model of the Lagerpeton pes has been raised to low (Fig. 1) and high (Fig. 2) digitigrade configurations.

Figure 1. Lagerpeton model right pes raised to a low digitigrade configuration in which pedal digit 2 would have impressed in line with the metacarpophalangeal joints of 3 and 4. Digit 4 completely impresses and digit 3 is slightly raised proximally.

Figure 2. Lagerpeton raised to a high digitigrade configuration. Here only two digits would have impressed with raised proximal phalanges. Either both of these configurations were part of the step cycle or just this one was. We have no Lagerpeton ichnites at present. Rotodactylus and Prorotodactylus ichnites impress five digits. These one likely impressed just two.

Figure 3. Click to enlarge. Niedwickski 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.

These models emphasize the impossibility that anything like Lagerpeton could have produced Prorotodactylus or Rotodactylus ichnites (contra Brusatte et al. 2013). Better matches can be found in Cosesaurus, Tanystropheus and kin as shown earlier.

The Ascending Process
On dinosaurs the ascending process of the astragalus is in front of the ankle. It advances upwards and ultimately covers the lower tibia.

By contrast, in Lagerpeton the ascending process is in back. This is a key difference that goes unrecognized by those who promote a dinosauromorph nesting for Lagerpeton. A small posterior ascending process can also be found in the chanaresuchid, Tropidosuchus.

Cardboard models
In the absence of 3D and wire modeling (which I used for Pteranodon), cardboard feet make quick models for difficult subjects. I’ve used them earlier (Peters 2000, 2011) to model various pterosaur feet. Here (Figs. 1, 2)  the model pes of Lagerpeton can be raised or lowered to test a variety of possible configurations. You can even split the metatarsals if appropriate. That enables one to arc the metatarsals, like teepee tent poles. In every configuration the PILs (parallel interphalangeal lines) can be drawn on the base/substrate. Those that are the most continuous typically reflect the actual pedal configuration. Here (Fig. 1) the more upright two-digit implant configuration, produces an ostrich-like pes with PILs at right angles to the proposed direction of movement, reflecting that stage in the step-cycle. My guess is this is the more likely candidate.

The evolution of a longer pedal digit 4 in chanaresuchids
In ancestral quadrupedal taxa, like Chanaresuchus (Fig. 3) and Tropidosuchus (Fig. 4) pedal digit 4 is so slender as to appear vestigial.

Figure 4. Chanaresuchus a quadrupedal ancestor to Tropidosuchus and Lagerpeton and the third Tropidosuchus-like taxon.

In derived taxa, like the other purported Tropidosuchus (Fig. 5), the pes does not appear to be so derived.

Figure 5. Tropidosuchus in its two variants. In the holotype (above) the humerus is more robust and pedal digit 4 is gracile, as in Chanaresuchus (Fig. 3). In the referred specimen of Tropidosuchus (below) the humerus is smaller and pedal digit 4 is longer than 3, as in Lagerpeton. The rise to a bipedal configuration appears to coincide with the change in pedal proportions. This is reptile evolution at work.

This apparent reversal to a more primitive condition appears to coincide with the reduction of the forelimb, and, in Lagerpeton to the elongation of the hind limb relative to the size of the pelvis.

Figure 6 The closest kin of Tropidosuchus are the much larger Chanaresuchus (matching Nesbitt 2011) and the larger and taller Lagerpeton.

Besides, the foot mismatch, Lagerpeton is a pretty large animal, at least twice the size of Tropidosuchus and a maginitude larger than the Rotodactylus trackmaker.

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.
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.

wiki/Lagerpeton

Non-dinosaurian Dinosauromorpha (Langer et al. 2013)

Continuing to push Lagerpeton as a “dinosauromorph” (which is traditional thinking), Langer et al. (2013) continues to ignore certain basic facts starting in the feet that divide pararchosauriforms (including Lagerpeton) and euarchosauriforms (including dinosaurs) into two major clades.

Figure 1. Click to enlarge. The feet of Euarchosauriformes (above in white) and Pararchosauriformes (below in grey). No higher euarchosauriformes have a longer digit 4 than 3. Both clades share more foot traits with each other, which removes Lagerpeton from the lineage of dinosaurs in the Euarchosauriformes, and puts it in the line of descent from Diandongosuchus (with its long digit 4) and/or Proterochampsa (with its short digit 1). Also note that the ascending process of the astragalus is posterior in Lagerpeton, anterior in dinosaurs.

Euarchosauriformes
It’s unfortunate that so few euarchosauriform feet are known that include a complete digit 4, but what we do know demonstrates that digit 4 is always shorter than 3 and metatarsal 4 is always shorter than mt3.

Pararchosauriformes
In this clade pedal digit 4 can sometimes be longer than 3 and metarsal 4 is never shorter than mt3. Sometimes pedal digit 4 is reduced to a vestige, other times, even within a genus, it is not. In any case, Lagerpeton belongs in this clade, a small biped at the acme of a  large, flat-headed, quadrupedal clade. It does not belong with dinosaurs or their short pedal digit 4 kin. In Lagerpeton, the astragalus flange rises in back of the tibia, not in the front, as in dinosaurs.

The way to separate the Euarchosauriformes from the Pararchosaurifomes
is to introduce protorosaurs, Youngina, Youngoides, Choristodera, Doswellia and the traditional archosauriformes, as demonstrated by the large reptile tree.

Mistaking Early Triassic bipedal lizard tracks for dinosauromorph tracks
Earlier we discussed the mistakes of Brusatte et al. (2012) who claimed that certain ichnites related to Rotodactylus in the Early Triassic belonged to lagerpetids, when in reality they belong to cosesaurids, in the ancestry of pterosaurs.

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
Langer MC, Nesbitt SJ, Bittencourt JS and Irmis RB 2013.  Non-dinosaurian Dinosauromorpha.  Geological Society, London, Special Publications v.379, first published February 13, 2013; doi 10.1144/SP379.9 From: Nesbitt SJ, Desojo JB and Irmis RB eds) Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379, http://dx.doi.org/10.1144/SP379.9 # The Geological Society of London 2013.