Brocklehurst et al. 2021 review extinct and extant archosaur lungs

Brocklehurst et al. 2021 employed extant phylogenetic bracketing
to look at lung and rib design in extant taxa to understand extinct taxa, specifically archosaurs.

Unfortunately,
Brocklehurst et al. cherry-picked their phylogenetic bracket.

In other words
they added some taxa that should not be there and omitted some that should be there. In particular, the authors perpetuated the myth that pterosaurs are archosaurs. They haven’t been archosaurs for twenty one years (Peters 2000).

Furthermore
the authors consider the dinosaur-mimic Silesaurus an archosaur in-group taxon. In the large reptile tree (LRT, 1794+ taxa) Silesaurus nests just outside the Archosauria, in the Poposauria, Since basal poposaurs, like Poposaurus (Fig. 1), were also bipeds, this taxon should have been considered. The authors nest Euparkeria as the outgroup for the Archosauria. In the LRT Euparkeria is several nodes removed.

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

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

The authors note,
“Out-group comparisons show that heterogeneously partitioned lungs and a PPS are present in both archosaurs and turtles [29], and unidirectional flow is a basal diapsid character present in archosaurs, turtles and lepidosaurs [27].” 

In the LRT two unrelated clades
convergently developed a diapsid skull architecture, 1) lepidosaurs and 2) basal diapsid (Petrolacosaurus and kin). The last common ancestor of these otherwise unrelated ‘diapsids’ was Silvanerpeton, an amphibian-like reptile (= amniote) in the Viséan. Turtles and their ancestors are still not diapsids.  This yet another myth perpetuated by the Brocklehurst steam dispelled here.

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 2. 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).

If you’re going to study archosaur lungs
they must be seen in a valid phylogenetic context, somewhat lacking here. For instance, the swinging pubis of extant crocs is a novel trait not seen in basal bipedal crocs like Trialestes.

The authors state, 
“The crocodilian lung is thought to be a better representation of the ancestral lung morphology of archosaurs.”

Since only crocs and dinos comprise the Archosauria in the LRT, that is a reasonable consideration. However, basal bipedal crocs are sisters to basal bipedal dinosaurs (Fig. 2), so that puts ann overlooked crinkle in this hypothesis. Large, aquatic extant crocs are much more lethargic than their small, gracile, long-legged, active, bipedal ancestors were. In other words, look out for possible reversals here.

Figue 1. A new reconstruction of the basal bipedal croc, Pseudhesperosuchus based on fossil tracings. Some original drawings pepper this image. Note the interclavicle, missing in dinosaurs and the very small ilium, only wide enough for two sacrals. The posterior dorsals are deeper than the anterior ones.

Figue 1. A new reconstruction of the basal bipedal croc, Pseudhesperosuchus based on fossil tracings. Some original drawings pepper this image. Note the interclavicle, missing in dinosaurs and the very small ilium, only wide enough for two sacrals. The posterior dorsals are deeper than the anterior ones.

Don’t overlook the hallmark of flapping forelimbs,
the locked down stem-like coracoid, is present in the basal bipedal crocodylomorph, Pseudhesperosuchus (Fig. 1). Yes, they were THAT active, but that trait never really took off.  : – )

Co-author Emma Schacher talked about dinosaur lungs
in this 2019 Tedx Talk on YouTube:

References
Brocklehurst RJ, Schachner ER, Codd JR and Sellers WI 2020
Respiratory evolution in archosaurs. Philosphical Transactions of the Royal Society B 375: 20190140. http://dx.doi.org/10.1098/rstb.2019.0140
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.

Gracilisuchus 2020: Two new specimens added to the genus

Lucuona, Desojo and Cerda 2020 bring us new information
on Gracilisuchus (Figs. 1, 3), a basal bipedal crocodylomorph in the large reptile tree (LRT, 1734+ taxa; subset Fig. 2). Gracilisuchus was originally considered an ornithosuchid by Romer (1972). Others considered it to nest between Parasuchus and Stagonolepis (Benton and Clark 1988), as the sister to Postosuchus (Juul 1994) or as a sister to Postosuchus and Erpetosuchus (Benton and Walker 2002). All suffered from taxon exclusion.

Figure 4. The PVL 4597 specimen nests at the base of the Archosauria, not with Gracilisuchus.

Figure 1. The PVL 4597 specimen (above)  nests at the base of the Archosauria, not with Gracilisuchus (below). Gracilisuchus based on holotype  PULSR8 with the skull diagram (MCZ4117)  based on Romer 1971. See figure 3 for an update on that skull.

Gracilisuchus stipanicicorum
(Romer 1972; Butler et al. 2014; Ladinian, Middle Triassic, ~230 mya, 30 cm long; holotype PULSR8) is a basal crocodilomorph. In the LRT Gracilisuchus was derived from a sister to Dibothrosuchus (Fig. 5), and preceded both Saltopus and Scleromochlus in the LRT. These three taxa are not mentioned in the Lucuona et al. text.

Taxon exclusion
is the major and continuing problem in vertebrate paleontology. The LRT is trying to repair that problem simply by adding taxa.

From the Lucuona et al. 2020 abstract:
“Gracilisuchus stipanicicorum Romer, 1972 is a basal suchian from the Late Triassic Chañares Formation (Argentina), nested in the recently erected Gracilisuchidae, along with Turfanosuchus dabanensis Young, 1973 and Yonghesuchus sangbiensis Wu et al., 2001 from China.”

Adding taxa separates these three genera in the LRT (subset Fig. 2) and invalidates any clade with only these three polyphyletic members. These three taxa and all their descendants do form an unnamed clade: Poposauria + Archosauria in the LRT, which was not their intention, nor that of Butler et al. 2014, who erected the clade with these three members with the same criticism about 5 years ago.

Figure 2. Subset of the LRT focusing on Crocodylomorpha. Matching Nesbitt et al. 2005, the LRT nests Redondavenator near the base of the Crocodylomorpha.

Figure 2. Subset of the LRT focusing on Crocodylomorpha. Matching Nesbitt et al. 2005, the LRT nests Redondavenator near the base of the Crocodylomorpha.

Continuing from the abstract:
“The six known specimens of Gracilisuchus Romer, 1972 preserve most of the skeleton, lacking only most of the shoulder girdle and forelimb. Our latest fieldwork has recovered two specimens that preserve previously unknown elements, including the humerus, radius, and ulna, as well as the femur, presacral vertebrae, and paramedian osteoderms.”

By contrast the LRT (Subset Fig. 2) separates the PVL 4597 specimen from the PULSR8 holotype. The former nests at the base of the Archosauria (Crocodylomorpha + Dinosauria) at least two nodes away at present.

By combining two or more specimens
Lecuona et al. 2020 created an unwanted and confusing chimaera. A better practice is to score each specimen individually and let those that nest together do so. THEN create a chimaera if warranted.

Figure 5. Gracilisuchus skull updated with new colors.

Figure 3. Gracilisuchus skull (MCZ 4117) updated. Note the slender fenestra between the premaxilla and maxilla, as in Dibothrosuchus.

The traditional short-faced Gracilisuchus specimen
MCZ 4116 (Fig. 4), was not mentioned in the Lecuona et al. 2020 text. Perhaps that’s a good thing since earlier the LRT nested the short-faced specimen with Trialestes.

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

Figure 4. The former Gracilisuchus specimens MCZ4116 and MCZ4118 with colors added.

Lecuona et al. consider Gracilisuchus to be a member
of the invalid clade, ‘Pseudosuchia’.

Bone histology studies
were performed on the two new specimens:

  1. CRILAR PV 480, “one and a half incomplete cervical centra articulated with each other and with two incomplete ribs, a series of three incomplete vertebrae articulated with one rib, dorsally in contact with the left row of the paramedian osteoderms, and posteriorly four ribs with no articulating vertebrae but in anatomical position (Fig. 2A, B), a series of six incomplete cervicodorsal vertebrae with some of their ribs preserved and half of a centrum attached posteriorly (Fig. 2C, D), and moulds of two short fragments of paramedian osteoderms”
  2. CRILAR PV 490, “two articulated cervical vertebra in contact with a short paramedian osteoderm series, one isolated dorsal vertebrae, left humerus, right ulna, right radius, left femur, and six histological sections of the femoral diaphysis and osteoderms”

Until phylogenetic analysis is performed on each specimen,
we can’t be sure that these are indeed Gracilisuchus specimens.

Figure 2. Images from Wu et al. 1993, colors and hind limbs added. Compare to skull in figure 1.

Figure 5. Images from Wu et al. 1993, colors and hind limbs added. Compare to skull in figure 1.

Until Lucuona et al. 2020 add pertinent taxa 
they will not understand the phylogenetic context of the holotype specimen, the referred specimens and all pertinent, but unrelated taxa. That means whatever they have to say about the new fossils has to be considered with some reservation. They think all this material belongs to Gracilisuchus. The LRT demonstrates at least one specimen nests apart from the holotype. Better to know with validation, than to guess.


References
Benton MJ and Clark JM 1988. Archosaur phylogeny and the relationships of the Crocodilia in MJ Benton (ed.), The Phylogeny and Classification of the Tetrapods 1: 295-338. Oxford, The Systematics Association.
Brinkman D 1981. The origin of the crocodiloid tarsi and the interrelationships of thecodontian archosaurs. Breviora 464: 1–23.
Butler RJ, Sullivan C, Ezcurra MD, Liu J, Lecuona A and Sookias RB 2014. New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and
the biogeography of the archosaur radiation. BMC Evolutionary Biology 14:1-16.
Juul L 1994. The phylogeny of basal archosaurs. Palaeontographica africana 1994: 1-38.
Lecuona A and Desojo, JB 2011. Hind limb osteology of Gracilisuchus stipanicicorum(Archosauria: Pseudosuchia). Earth and Environmental Science Transactions of the Royal Society of Edinburgh 102 (2): 105–128.
Lecuona A, Desojo JB and Pol D 2017. New information on the postcranial skeleton of Gracilisuchus stipanicicorum (Archosauria: Suchia) and reappraisal of its phylogenetic position. Zoological Journal of the Linnean Society XX:1–40.
Lecuona A, Desojo JB and Cerda IA 2020. New information on the anatomy and histology of Gracilisuchus stipanicicorum (Archosauria: Pseudosuchia) from the Chañares Formation (early Carnian), Argentina. Comptes Rendus Palevol 19 (3): 40-62. https://doi.org/10.5852/cr-palevol2020v19a3
Parrish JM 1993. Phylogeny of the Crocodylotarsi, with reference to archosaurian and crurotarsan monophyly. Journal of Vertebrate Paleontology 13(3):287-308.
Romer AS 1971. The Chañares(Argentina) Triassic reptile fauna. Two new bu incompletely known long-limbed pseudosuchians. Breviora 378:1–10.
Romer AS 1972. The Chañares (Argentina) Triassic reptile fauna. An early ornithosuchid pseudosuchian, Gracilisuchus stipanicicorum, gen. et sp. nov. Breviora 389:1-24.

wiki/Gracilisuchus

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/

Osteology of Carnufex 2015, 2016

Drymala and Zanno 2016 returned to their description of Carnufex,
(Fig. 1) a partial disarticulated basal crocodylomorph they published on a year earlier (Zanno, Drymala, Nesbitt and Schneider 2015; Fig. 2).

Figure 2. Data from Drymala and Zanno 2016 below. Elements colorized and moved around here above. It's always better NOT to use freehand illustrations.

Figure 1. Below: Data from Drymala and Zanno 2016. Above: Elements colorized and reconstructed  here. I prefer moving elements around to freehand illustration. The size of the lacrimal changes from the earlier paper (see figure 2).

There is also a strange data problem here. 
The 2015 paper included a reconstruction (Fig. 2) with a smaller lacrimal. The 2016 paper includes data and a reconstruction (Fig. 1) with a larger lacrimal.

Figure 3. Carnufex is basically a giant Pseudhesperosuchus. Here they are compared to one another to scale and with skulls side by side. Dark gray areas are imagined on the original at bottom by Zanno et al. Click to enlarge. With a skull 4x larger than that of Pseudhesperosuchus, Carnufex was a likely 4.4 meter long bipedal killer. Note the smaller orbit and deeper jugal. Both neural arches are missing a centrum.

Figure 2. Carnufex (from 2015 data) compared to Pseudhesperosuchus. Dark gray areas are imagined on the original at bottom by Zanno et al 2015. Compare to 2016 data in figure 1.

Unfortunately
their 2016 cladogram (Fig. 3) omitted several taxa key to understanding Carnufex and the clade Crocodylomorpha in the large reptile tree (LRT, 1697+ taxa; subset Fig. 4). For instance, in the LRT only Dinosauromorpha + Crocodylomorpha combine to form the clade Archosauria. So one wonders why no basal dinosaurs appear in the 2016 cladogram. Worse yet, a large number of basal bipedal crocodylomorphs are absent (list below in red at left).

Figure 1. Carnufex cladogram by Drymala and Zanno 2016. Color overlays added here.

Figure 3. Carnufex cladogram by Drymala and Zanno 2016. Color overlays added here. The phytosaur, Machaeoroprosopus does not belong in this list of euarchosauriformes. Turfanosuchus is a basal poposaur in the LRT. Gracilisuchus is a basal crocodylomorph in the LRT, so I suspect bad scores for those two taxa.

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

Figure 4. Subset of the LRT focusing on the Crocodylomorpha, dorsal scutes, elongate proximal carpals, bipedality and clades.

After all the scoring changes
the prior nesting in the LRT of Carnufex with Pseudhesperosuchus (Fig. 5) remains the same, evidence that sometimes changes are not that important taxonomically.

Figure 5. Skull of Pseudhesperosuchus, a basal bipedal crocodylomorph close to Carnufex.

Figure 5. Skull of Pseudhesperosuchus, a basal bipedal crocodylomorph close to Carnufex.

In the LRT
dinosaurs are the closest outgroup to the basal bipedal crocs. In the LRT Pseudhesperosuchus is the closest taxon to Carnufex. Together these exclusions from the two Carnufex papers are errors of omission that change some hypothetical relationships.

If you’re going to use a comprehensive list of pertinent taxa,
it’s best to figure out first which taxa are the most pertinent. That’s the value of the LRT, where more taxa solve more problems here than more characters and fewer taxa do in smaller studies. You can always delete unrelated taxa once you have the proper phylogenetic context and wish to increase the focus of your study.


References
Drymala SM and Zanno LE 2016. Osteology of Carnufex carolinensis (Archosauria: Psuedosuchia) from the Pekin Formation of North Carolina and Its Implications for Early Crocodylomorph Evolution. PLoS ONE 11(6): e0157528. doi:10.1371/journal.pone.0157528
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/Carnufex
wiki/Pseudhesperosuchus

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

Reassessment of Scleromochlus: Bennett 2020

SC Bennett 2020
followed Benton 1999 and others (citations below) in giving us a closer look at Scleromochlus taylori (Woodward 1907; Late Carnian, Late Triassic ~217 mya, 18 cm long; Figs. 1, 2), a tiny biped crocodylomorph derived from a sister to Gracilisuchus and Saltopus according to the large reptile tree (LRT, 1650+ taxa; Fig. 3).

Bipeds of the Triassic

Figure 1. Bipeds of the Triassic. Top to bottom: Cosesaurus, Scleromochlus, Marasuchus and Tropidosuchus. Each represents a distinct lineage of bipeds with bipedal sister taxa. This version of Scleromochlus was published in Peters 2002, based on Benton 1999.

Unfortunately,
despite the firsthand examination of this taxon, Bennett ignored sister taxa recovered by the LRT (Figs. 3, 4). His cladograms failed to recover a single node on which to nest Scleromochlus. In essence, he still doesn’t know what Scleromochlus is, despite his best efforts (see below for Bennett’s self assessment).

From Bennett’s 2020 introduction
“The first specimens were briefly described and named by Woodward (1907), who interpreted Scleromochlus as a small bipedal running or leaping dinosaur. Huene (1914) described the specimens more thoroughly and interpreted Scleromochlus as an arboreal climbing and leaping pseudosuchian close to the origin of pterosaurs. Swinton (1960), Brodkorb (1971) and Martin (1983) discussed Scleromochlus in relation to the origin of birds, whereas Padian (1984) suggested that Huene had it only half right and interpreted Scleromochlus as a digitigrade bipedal cursor close to the origin of pterosaurs and dinosaurs, a view that has gained general acceptance (Gauthier, 1986; Sereno, 1991; Benton, 1999; Fraser, 2006; Brusatte et al., 2010). Despite that, Bennett (1996, 1997) argued that Huene had only the other half right and Padian had it all wrong and that Scleromochlus was an arboreal leaper not close to pterosaurs.”

True to Bennett’s curse,
“You will never be published, and if you are published, you will not be cited,” Bennett 2020 did not cite Peters 2002, who wrote, “Among recent workers, Padian (1984), Sereno (1991) and Benton (1999) noted pterosaur similarities in the bipedal diapsid, Scleromochlus. The homoplasy is striking (Table I). However, figures by Benton (1999), which are reconstructed here (Fig. 8D), show that this archosauriform had a low, wide skull, a deep antorbital fossa, a terminal naris, a short neck of only six or seven cervicals, a long lumbar region, a small manus, a broadly separated pubis and ischium, a fibular flange, a calcaneal heel and a spike-like, digit-less metatarsal V. These characters are not found in pterosaurs. They are synapomorphies of basal bipedal crocodylomorphs, such as Gracilisuchus (Romer, 1972) and Saltoposuchus (Huene, 1921; Sereno and Wild, 1992).”

Bennett 2020 failed to mention
or include Junggarsuchus, Pseudhesperosuchus, Gracilisuchus and Saltposuchus in his taxon list. He only mentioned Saltopus as a coeval predator. These are all bipedal basal crocodylomorpha, a clade  ignored by Bennett 2020.

Figure 2. From Bennett 2020 showing in dorsal view the skull of Scleromochlus with DGS overlays colorizing the bones. At right, Bennett's drawing of same.

Figure 2. From Bennett 2020 showing in dorsal view the skull of Scleromochlus with DGS overlays colorizing the bones. At right, Bennett’s drawing of same. A compression crack across the fragile frontal was identified as the only suture in the skull, between the nasal and frontal, by Bennett 2020.

Back to Bennett’s 2020 introduction
“In 2013 I came to suspect that Bennett (1997), too, had it at least half wrong. By happy coincidence, I had shortly before perfected my technique for studying small slab specimens, so I took another look at the evidence and after several years of study gained some confidence in interpreting the specimens. This article is not a thorough redescription of the osteology of Scleromochlus but rather is a reassessment of the osteological evidence that has been used to interpret Scleromochlus’s mode of life, locomotion, and phylogenetic relationships.”

Again, the major shortcoming
in Bennett’s phylogenetic analysis is taxon exclusion. And Bennett’s “perfected technique” is not perfect (Fig. 2). His outmoded freehand technique overlooks many bones and sutures.

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.

Concluding Bennett’s 2020 introduction
“A principal component analysis of skeletal measurements of Scleromochlus and other vertebrates of known locomotor type was done to examine the locomotion of Scleromochlus, and it was found to plot with frogs. Based on osteological evidence, including previously overlooked evidence from the specimens, and the principal component analysis, Scleromochlus is interpreted as a sprawling quadrupedal hopper analogous to frogs. Phylogenetic analyses found that Scleromochlus was not an ornithodiran, but rather either within the Doswelliidae or outside the clade consisting of the most recent common ancestor of the Erythrosuchidae and Archosauria and all its descendants.”

Pretty vague…
If the best Bennett can do is nest tiny bipedal Scleromochlus with giant, quadrupedal  Doswellia OR Erythrosuchus, then Bennett should have added taxa to his cladogram. If Bennett would have just added archosaur taxa that were small, bipedal and with flat skulls and osteoderms, he would have nailed it.

Other than the proportions, size, skeletal details and osteoderms
of Scleromochlus, the anterior lean of the long quadrate is also a crocodylomorph trait overlooked by all prior workers, except Peters 2002 (Figs. 1,2). Bennett traced the quadrate in stereo, but identified it with a question mark (Fig. 2). Whenever that happens, the technique has not been, as Bennet reported, “perfected.’


References
Bennett SC 1996. The phylogenetic position of the Pterosauria within the Archosauromorpha. Zoolological Journal of the Linnean Society 118: 261–308.
Bennett SC 1997. The arboreal leaping theory of the origin of pterosaur flight. Historical Biology 12(3–4):265–290
Bennett SC 2020. Reassessment of the Triassic archosauriform Scleromochlus taylori: neither runner nor biped, but hopper. PeerJ 8:e8418 DOI 10.7717/peerj.8418
Benton MJ 1999. Scleromochlus taylori and the origin of the pterosaurs. Philosophical Transactions of the Royal Society London, Series B 354 1423-1446. Online pdf
Clark JM 2011. A new shartegosuchid crocodyliform from the Upper Jurassic Morrison Formation of western Colorado. Zoological Journal of the Linnean Society. 163 (s1): S152–S172.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Padian K. 1984. The Origin of Pterosaurs. Proceedings, Third Symposium on Mesozoic Terrestrial Ecosystems, Tubingen 1984. Online pdf
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Hist Bio 15: 277–301.
Senter P 2003. Taxon Sampling Artifacts and the Phylogenetic Position of Aves. PhD dissertation. Northern Illinois University, 1-279.
Sereno PC 1991. Basal archosaurs: phylogenetic relationships and functional implications. Journal of Vertebrate Paleontology 11 (Supplement) Memoire 2: 1–53.
Woodward AS 1907. On a new dinosaurian reptile (Scleromochlus taylori, gen. et sp. nov.) from the Trias of Lossiemouth, Elgin. Quarterly Journal of the Geological Society 1907 63:140-144.

wiki/Scleromochlus

Meet Gnathovorax: the most primitive herrerasaur/dinosaur

Pacheco et al. 2019
introduce Gnathovorax cabreirai (Figs. 1), a new herrerasaurid (Fig. 2) based on “an exquisite specimen” (Fig. 3)

Figure 1. Gnathovorax compared to Herrerasaurus, PVL 4597 and Decuriasuchus.

Figure 1. Gnathovorax compared to Herrerasaurus, PVL 4597 and Decuriasuchus. Phylogenetic miniaturization occurred at the genesis of bipedalism in PVL 4597.

Unfortunately,
taxon exclusion prevented Pacheco et al. from understanding and appreciating the micro-evolution now documented at the base of the Dinosauria (Fig. 1) based on the large reptile tree (LRT, 1594 taxa). The authors omitted basal bipedal crocs, like Pseudhesperosuchus (Fig. 4), the basalmost archosaur PVL 4597 (Fig. 1) and the basal poposaur, Decuriasuchus (Fig. 1).

Figure 2. Cladogram from Pacheco et al. 2019. Colors added over the nodes to show where taxa nest in the LRT.

Figure 2. Cladogram from Pacheco et al. 2019. Colors added over the nodes to show where taxa nest in the LRT where Ornithischia and Sauropodomorpha are derived from basal Phytodinosauria.

Lacking pertinent taxa
also prevents Pacheco et al. (Fig. 2) from recovering the clade Phytodinosauria, which splits from basal Theropoda in the LRT.

Figure 3. Gnathovorax in situ from Pacheco et al. 2019. Green bones belong to other taxa.

Figure 3. Gnathovorax in situ from Pacheco et al. 2019. Green bones belong to other taxa.

Between Euparkeria (Fig. 4) and Dinosauria
are several transitional taxa not listed by Pacheco et al. The phylogenetic miniaturization at the base of the Archosauria is a common phenomenon at the origin of major vertebrate clades.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 4 The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus,  Pseudhesperosuchus, Herrerasaurus, Tawa and Eoraptor.The LRT is here for researchers to use
as a taxon checklist to make sure they are including all pertinent taxa in their smaller, more focused studies. Just because you’re a traditional paleontologist does not mean you have to omit non-traditional taxa.


References
Pacheco C, Müller RT, Langer M, Pretto FA, Kerber L and Dias da Silva S 2019. Gnathovorax cabreirai: a new early dinosaur and the origin and initial radiation of predatory dinosaurs. PeerJ 7:e7963 http://doi.org/10.7717/peerj.7963

SVP abstracts – Earliest avemetatarsalian?

Patellos et al. 2019 brings us
news of the earliest archosaur in the lineage of birds (rather than crocs).

Okay. That’s already wrong. In the large reptile tree (LRT, 1592 taxa) only crocs and dinos make up the Archosauria. Nesbitt et al. does not understand that hypothesis of interrelationships due to taxon exclusion and poor scoring going back to Nesbitt 2011. The purported clade, ‘Avemetatarsalia’ (= Ornithodira) was invalidated by the LRT.

From their abstract:
“Understanding of the evolution of the earliest avemetatarsalian (bird-line) archosaurs and the morphology of the hypothetical common ancestor of Archosauria is hampered by a poor fossil record.”
Incorrect. The common ancestor of Archosauria has been identified in the LRT as the PVL 4597 specimen wrongly attributed to Gracilisuchus. After that: Turfanosuchus (Fig. 1).
Figure 2. Skull of Turfanosuchus compared to Herrerasaurus, the basalmost dinosaur.

Figure 1. Skull of Turfanosuchus compared to Herrerasaurus, the basalmost dinosaur.

Patellos et al. 2019 continue:
“The earliest-diverging avemetatarsalians known, such as Teleocrater, are separated from the earliest diverging pseudosuchian (crocodylian-line) archosaurs, and the closest outgroups of Archosauria by a clear morphological gap.”
The LRT invalidates the traditional clade, ‘Pseudosuchia.’ Crocodylian-line archosaurs are Crocodylomorphs, distinct from bird-line archosaurs, dinosaurs. Remember, these authors consider the lepidosaurian pterosaurs to be closely related to dinosaurs, a theory with as much evidence as tail-dragging dinosaurs.
“Here we describe a potential early-diverging avemetatarsalian from the Middle Triassic (~ 230 Ma) “Basal Isalo II” beds of Madagascar, which appears to bridge these gaps. This new taxon is represented by a well-preserved partial skeleton including articulated cervical
vertebrae with articulated osteoderms; a scapulocoracoid; a partial femur; isolated trunk, sacral, and caudal vertebrae; and an ilium.”
“Noteworthy features of the neck region include: anteroposteriorly elongated vertebrae with laterally expanded dorsal ends of the neural spines, and an articulated set of osteoderms dorsal to the vertebrae. The cervical osteoderms, three pairs per vertebra, arranged in paramedian row, and bear tapering anterior processes.” 
“Potential synapomorphies of this specimen with avemetatarsalians include: femur with an incipient anterior trochanter, 1st sacral vertebra with a dorsoventrally expanded sacral rib, and ilium possessing a notch on the articulation surface with the ischium. This combination of features places the new taxon represented by this specimen at the base of Avemetatarsalia, outside aphanosaurs + dinosaurs, but this position is poorly supported.”
The best known members of the invalid Aphanosauria include Yarasuchus and Teleocrater (Fig. 2), taxa nested with a long line of non-Aphanosauria by the LRT between Rauisuchia and Archosauria.
Figure 3. Yarasuchus, Qianosuchus and Turfanosuchus nest together in Nesbitt et al. 2017 after rescoring.

Figure 2. Yarasuchus, Qianosuchus and Turfanosuchus nest together in Nesbitt et al. 2017 after rescoring.

Patellos et al. 2019 continue:
“More broadly, this new specimen indicates that cervical osteoderms were present in the earliest avemetatarsalians and were soon lost in the lineage.”
There’s no need for such phylogenetic gymnastics in the LRT.
“The generally plesiomorphic morphology of the new taxon also underscores the difficulty of identifying early avemetatarsalians from incomplete skeletons. Presence of an early diverging avemetatarsalian together with a lagerpetid and silesaurid in the “Basal Isalo II” beds of Madagascar documents the co-occurrence of multiple avemetatarsalian subgroups in Gondwana during the Triassic.”
They wish. The LRT resolves all such problems with high resolution. Blame S. Nesbitt for relying on his own poorly scored cladogram, inventing the ‘Aphanosauria’ and supporting the ‘Avemetatarsalia.’ Blame M. Benton for inventing the clade ‘Avemetatarsalia’.
Don’t trust those clades. Don’t trust the LRT. Run your own tests so you’ll know. In science this is the first, last and best option to resolve all such disagreements.

References
Patellos E et al. 2019. A new reptile from the ?Middle Triassic of Madagascar may represent the earliest-diverging avemetatarsalian (Archosauria). Journal of Vertebrate Paleontology abstracts.

The skull of PVL 4597 joins its post-crania in the LRT

The PhD thesis of Agustina Lecuona 2013
on the several specimens attributed to the Middle Triassic Gracilisuchus (Fig. 2) is online (PDF). It includes the previously unpublished skull of PVL 4597 (Figs. 1, 2), which the large reptile tree (LRT, 1592 taxa) nests apart from Gracilisuchus, as the last common ancestor of all archosaurs (crocs + dinos only) with or without its skull. We reviewed Gracilisuchus yesterday, so this addition to the LRT is timely.

Figure 1. The skull of PVL 4597 in several views from the 2013 PhD thesis of A. Leucona. Colors added.

Figure 1. The skull of PVL 4597 in several views from the 2013 PhD thesis of A. Lecuona. Colors added.

The differences between PVL 4597 and Gracilisuchus are few (Fig. 2).
So, it is not a surprise that Lecuona considered them congeneric.

However,
the differences are fewer between PVL 4597 and its ancestor, Turfanosuchus (Fig. 4), and  its descendant, Herrerasaurus, the last common ancestor of dinosaurs traditionally and in the LRT. 19 additional steps are added when PVL 4597 is forced to nest with Gracilisuchus in the LRT.

FIgure 2. Comparing PVL 4597 to Gracilisuchus. Despite their many similarities, these two do not nest together in the LRT.

FIgure 2. Comparing PVL 4597 to Gracilisuchus. Despite their many similarities, these two do not nest together in the LRT. Taxon exclusion is the issue with the PhD dissertation and the use of an invalidated analysis from Nesbitt 2011.

Basal members of large clades
are sisters to basal members of sister clades (Fig. 3). We compare those taxa with one another, ignoring the more derived members.

Figure 3. Subset of the LRT focusing on basal archosaurs and their immediate ancestors.

Figure 3. Subset of the LRT focusing on basal archosaurs and their immediate ancestors.

Here (Fig. 4) are the skulls of
Turfanosuchus and Herrerasaurus, taxa closer to PVL 4597 than PVL 4597 is to Gracilisuchus is in the LRT. The long-awaited skull confirms the nesting of the post-crania.

Figure 2. Skull of Turfanosuchus compared to Herrerasaurus, the basalmost dinosaur.

Figure 4. Skull of Turfanosuchus compared to Herrerasaurus, the basalmost dinosaur.

Without PVL 4597, 
the LRT still nests Turfanosuchus and basal bipedal crocs close to the base of the Dinosauria, contra the results of other studies that generally do not include those taxa.

Unfortunately,
Lecuona’s PhD thesis employed a borrowed and flawed cladogram on which she mistakenly trusted in: Nesbitt 2011. Even though Lecuona’s revised cladogram includes the basal bipedal crocs (which nest at derived nodes in her thesis), earlier we dismantled Nesbitt 2011 in a 7-part series ending here. Rescored Nesbitt 2011 resembles the LRT.


References
Lecuona A 2013. Anatomía y relaciones filogenéticas de Gracilisuchus stipanicorum y sus implicancias en el origen de Crocodylomorpha. PhD thesis. PDF
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.

wiki/Gracilisuchus

Late Triassic Kwanasaurus: another poposaur close to Silesaurus

…but only in the LRT.
There is no reference to the Poposauria (Fig. 2) in the Martz and Small 2019 text. They describe their new taxon, Kwanasaurus wiliamparkeri (Fig. 1), known from scattered bits and pieces from young and old individuals, and nest it with Silesaurus (Fig. 2). The authors consider Silesaurus a dinosauromorph.

By contrast
in the large reptile tree (LRT, 1566 taxa; subset Fig. 3) the clade Dinosauromorpha is a junior synonym for Archosauria because only crocs and dinos make up the Archosauria. This recovery is distinct from all other studies that suffer from taxon exclusion and poor scoring.

FIgure 1. Large image from Martz and Small 2019. Small image scaled using scale bars. Dark image slightly modified to fit ilium length, humerus, etc.

FIgure 1. Large image from Martz and Small 2019. Small image scaled using scale bars. Dark image slightly modified to fit ilium length, humerus, etc.

The authors report:
“We have opted to utilize the data matrix of Peecook et al. (2013), acquiring the Nexus file from Morphobank. The matrix of Peecook et al. (2013) is slightly modified from the matrix of Nesbitt et al. (2010).” Earlier in a 7-part series we looked at scoring problems with Nesbitt inspired cladograms.

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.

In the LRT
(subset Fig. 3) the clade Poposauria (including Silesaurus and kin) nest as the first outgroup to the Archosauria. So dinosaurs and polosaurs are very close, as everyone agrees. Just keep adding taxa, especially basal bipedal crocs, to fine tune the tree topography.

Figure 5. Subset of the LRT focusing on the Poposauria and surrounding clades.

Figure 3. Subset of the LRT focusing on the Poposauria and surrounding clades.

Here’s a cladogram from Martz and Small 2019
(Fig. 4) missing many pertinent taxa and including five irrelevant taxa, like pterosaurs and lagerpetids (proterochampsids). That and a raft of bad scores mess things up as demonstrated by the lack of similarity between putative sister taxa below. There is no such problem in the LRT (Fig. 3) where microevolution is documented between sisters.

Figure 6. Three cladograms from Martz and Small 2019 nesting Kwanasaruus with silesaurids.

Figure 4. Three cladograms from Martz and Small 2019 nesting Kwanasaruus with silesaurids. Yellow green are poposaur in the LRT. Yellow tint are dinosaurs in the LRT. Brown are lagerpetids in the LRT. Gray are lepidosaur pterosaurs in the LRT. 

References
Martz JW and Small BJ 2019. Non-dinosaurian dinosauromorphs from the Chinle Formation (Upper Triassic) of the Eagle Basin, northern Colorado: Dromomeron romeri (Lagerpetidae) and a new taxon, Kwanasaurus williamparkeri (Silesauridae).
PeerJ 7:e7551 DOI 10.7717/peerj.7551