Convolosaurus enters the LRT basal to pachycephalosaurs

Originally it was considered a basal ornithopod.

FIgure 1. Convolosaurus from Andrzejewski, Winkler and Jacobs 2019, re built from a flock of juvenile specimens.

FIgure 1. Convolosaurus from Andrzejewski, Winkler and Jacobs 2019, re built from a flock of juvenile specimens.

Andrzejewski, Winkler and Jacobs 2019 report,
“The new ornithopod, Convolosaurus marri gen. et sp. nov., is recovered outside of Iguanodontia, but forms a clade with Iguanodontia exclusive of Hypsilophodon foxii. The presence and morphology of four premaxillary teeth along with a combination of both basal and derived characters distinguish this taxon from all other ornithopods.” 

Figure 2. Subset of the LRT focusing on the clade Phytodinosauria. Convolosaurus nests closer to the dome head dinosaurs, not the ornithopods.

Figure 2. Subset of the LRT focusing on the clade Phytodinosauria. Convolosaurus nests closer to the dome head dinosaurs, not the ornithopods.

By contrast
the large reptile tree (LRT, 1419 taxa) nests Convolosaurus basal to the Agilisaurus + Stegoceras at the base of the Pachycephalosauria (dome-head dinos). All these taxa were included in the original paper, but they did not nest together. Andrzejewski, Winkler and Jacobs 2019 did not nest their cladogram on Chilesaurus and Daemonosaurus, two taxa missing from their cladogram. This may have played a part in the different tree topologies.

Then again…
the LRT presently does not include Hypsilophodon or Thescalosaurus, taxa that nest with Convolosaurus in Andrzejewski, Winkler and Jacobs 2019. Soon they will be added. Then we’ll revisit this. 

Figure 3. Convolosaurus cladogram from Andrzejewski, Winkler and Jacobs 2019. Note the complete lack of consensus between the tree topology and figure 2.

Figure 3. Convolosaurus cladogram from Andrzejewski, Winkler and Jacobs 2019. Note the complete lack of consensus between this tree topology and the LRT in figure 2. In the LRT Haya and Pisanosaurus nest together near the base of the Ornithischia, but not here. 

Convolosaurus marri (Andrzejewski, Winkler and Jacobs 2019; SMU 72834; 2.5m in length) informally nicknamed the “Proctor Lake hypsilophodont”, this specimen is known from a flock of subadults.


References
Andrzejewski KA, Winkler DA and Jacobs LL 2019. A new basal ornithopod (Dinosauria: Ornithischia) from the Early Cretaceous of Texas. PLoS ONE. 14 (3): e0207935. doi:10.1371/journal.pone.0207935.

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Pampadromaeus in exquisite detail

Langer et al. 2019
bring us new data on the basal phytodinosaur, Pampadromaeus (Cabriera et al. 2011; Fig. 1). Pampadromaeus was a small (1m length) biped with a generalized basal dinosaur morphology.

The authors produced a cladogram
(Fig. 2) focusing on Pampadromaeus and kin. Due to taxon exclusion, they considered Pampadromaeus a basal sauropodomorpha. The LRT (subset Fig. 3) nests it as the Late Triassic last common ancestor (LCA) of Sauropodomopha + Ornithischia.

Figure 2. Basal ornithischia and Pampadroameus, a sister to their common ancestor. Daemonosaurus likely resembled Pampadromaeus, with its long neck.

Figure 1. Basal ornithischia and Pampadroameus, a sister to their common ancestor. Daemonosaurus likely resembled Pampadromaeus, with its long neck.

Unfortunately,
Langer et al. are using an old taxon list that is missing many taxa. In the large reptile tree (1406 taxa, LRT, subset Fig. 3) Marasuchus is a basal theropod, not a dinosaur outgroup. Silesaurus is an outgroup poposaur (a dinosaur-mimic), not a sister to Ornithischia. Ornithischia is a dinosaur in-group, nesting with basal phytodinosaurs and sauropodomorphs. Crocodylomorpha (not included in Langer et al.) is the outgroup for the Dinosauria in the LRT.

Figure 2. Cladogram from xx 2019, colors added. Marasuchus is not an outgroup to the Dinosauria. In the LRT it nests as a basal theropod.

Figure 2. Cladogram from xx 2019, colors added. Marasuchus is not an outgroup to the Dinosauria. In the LRT it nests as a basal theropod.

The differences between the tree topologies
in the Langer et al. cladogram and the LRT appear to result largely from the choice of outgroup. In the LRT the outgroups are not chosen, but are recovered from a list of 1400+ taxa. Oddly, some taxa in the LRT are not included in the Langer et al. study. These include Leyesaurus, Barberenasuchus, Eodromaeus, and one specimen of Buriolestes. The LRT includes no suprageneric taxa, like Ornithischia (Chilesaurus, Daemonosaurus, Jeholosaurus and their descendants).

Figure 4. Subset of the LRT focusing on the Phytodinosauria. Three sauropods are added here.

Figure 3. Subset of the LRT focusing on the Phytodinosauria. Three sauropods are added here.

Experiment with outgroups
If the taxon list for the LRT is reduced to more or less match that of Langer et al. 2019, AND Marasuchus is chosen as the outgroup, the result more closely approaches the Langer et al. tree topology (Fig. 4).

Figure 3. Matching the taxon list to that of xx 2019 and choosing Marasuchus for the outgroup results in this cladogram of basal dinosaur relationships.

Figure 4. Matching the taxon list to that of xx 2019 and choosing Marasuchus for the outgroup results in this cladogram of basal dinosaur relationships using LRT data and taxa.

Adding Euparkeria to this list
(Fig. 4) to create a more distant outgroup for  all included taxa moves Silesaurus outside the Dinosauria and moves Marasuchus and Guabisaurus into the Dinosauria. Basically this is what the LRT recovers with a taxon list similar to Langer et al. 2019.

Figure 5. Adding Euparkeria to figure 4 results in this tree where Silesaurus nests outside the Dinosauria, as it does in the LRT. Theropods nest together, as in the LRT. So do phytodinosaurs.

Figure 5. Adding Euparkeria to figure 4 results in this tree where Silesaurus nests outside the Dinosauria, as it does in the LRT. Theropods nest together, as in the LRT. So do phytodinosaurs.

Pampadromaeus barberenai (Cabriera et al. 2011) is a new dinosaur from the Late Triassic of Brazil. It was originally described as a stem sauropodomorph known from a partial disarticulated skeleton and most of the skull bones. The authors reported, “Based on four phylogenetic analyses, the new dinosaur fits consistently on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together with some neotheropod traits.”


References
Cabreira SF, Schultz CL, Bittencourt JS, Soares MB, Fortier DC, Silva LR and Langer MC 2011. New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil. Naturwissenschaften (advance online publication) DOI: 10.1007/s00114-011-0858-0
Langer MC, McPhee BW, Marsola JCdA, Roberto-da-Silva L, Cabreira SF 2019. Anatomy of the dinosaur Pampadromaeus barberenai (Saurischia—Sauropodomorpha) from the Late Triassic Santa Maria Formation of southern Brazil. PLoS ONE 14(2): e0212543.
https://doi.org/10.1371/journal.pone.0212543
Martínez RN and Alcober OA 2009. A basal sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the early evolution of Sauropodomorpha (pdf). PLoS ONE 4 (2): 1–12. doi:10.1371/journal.pone.0004397. PMC 2635939. PMID 19209223. online article

wiki/Panphagia
wiki/Pampadromaeus

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

 

 

SVP 2018: A super-matrix for an invalid ‘Thyreophora’

Raven, Maidment and Barrett 2018 report,
“The individual lineages, Ankylosauria and Stegosauria, have been studied thoroughly, but there has never before been a comprehensive whole-group cladistic analysis of Thyreophora.”

According to Wikipedia:
“Thyreophorans are characterized by the presence of body armor lined up in longitudinal rows along the body. Threophora (Nopsca 1915) has been defined (Sereno 1998) as the group consisting of all species more closely related to Ankylosaurus than to Triceratops. Thyreophoroidea was first named by Nopcsa in 1928 and defined by Sereno in 1986, as “ScelidosaurusAnkylosaurus, their most recent common ancestor and all of its descendants”. Eurypoda was first named by Sereno in 1986 and defined by him in 1998, as “Stegosaurus, Ankylosaurus, their most recent common ancestor and all of their descendants”.

Raven, Maidment and Barrett 2018 report,
“Here, the first species-level phylogenetic super matrix of the whole-group Thyreophora is presented, incorporating all previous known cladistic analyses of ankylosaurs, stegosaurs and basal thyreophorans and including all valid species within Thyreophora, for a total of 89 taxa and 338 characters.

Unfortunately
in the large reptile tree (LRT, 1308 taxa, Fig. 1) the last common ancestor of Ankylosauria and Stegosauria also includes among its descendants: heterodontosaurids, lesothosaurs, duckbills and horned dinosaurs.

So ‘Goodbye, Eurypoda and Thyreophora’
(unless these clades someday become more inclusive by consensus). The super-matrix of Raven, Maidment and Barrett 2018 probably does not include the LRT or the taxonomic tree it finds within the clade Ornithischia. So use their study to learn about the stegosaurs and the ankylosaurs, but not the last common ancestor of stegosaurs and ankylosaurs. That would be a sister to late-surviving Late Cretaceous Haya and/or Late Triassic Pisanosaurus.

Figure 4. Subset of the LRT focusing on the Phytodinosauria. Three sauropods are added here.

Figure 1. Subset of the LRT focusing on the Phytodinosauria. Scelidosaurus through Minmi are basal ankylosaurs. Lesothosaurus through Stegosaurus are basal stegosaurs.

References
Raven TJ, Maidment SC and Barrett PM 2018. The first phylogenetic super-matrix of the armored dinosaurs (Ornithischia, Thyreophora). SVP abstracts.

wiki/Thyreophora

Leptoceratops repairs an unresolved node

Earlier a skull only taxon, Auroraceratops, nested with a skull-less taxon, Stenopelix in the Ornithischia. Such non-overlapping trait pairings cannot be resolved. Does one nest basal to another? Or vice versa? Do they nest together? The cladogram cannot tell you, so you end up with 3 possible trees. Sometimes that happens.

Figure 1. Leptoceratops in situ 2x. This taxon resolves the headless and head only node at the base of the ceratopsians in the LRT.

Figure 1. Leptoceratops in situ 2x. This taxon resolves the headless and head only node at the base of the ceratopsians in the LRT. Those ribs are oddly straight. Did they produce a horned-lizard like torso (wider than deep)?

What helps is taxon addition.
Here Leptoceratops (Fig. 1), known from complete material (skull + post-crania) is added to the LRT and returns the basal ceratopsian node to resolution.

Leptoceratops gracilis (Brown 1914; Latest Cretaceous; 2m long) is a late surviving member of an early radiation of bipedal ceratopsians that probably browsed while quadrupedal. The ventral maxilla was convex. The skull was narrower than most. The ribs appear to have flared widely, not deeply, creating a horned-lizard-like torso.

References
Brown B 1914. Leptoceratops, a new genus of Ceratopsia from the Edmonton Cretaceous of Alberta. Bulletin of the AMNH 33, article 36.


Dr. David Unwin reports
the untimely death of Dr. Lü Junchang, author and co-author of dozens of publications coming out of China. I met Dr. Lü long ago when he was working in Texas, early in his career and studies. The pterosaur, Beipiaopterus, was the subject of an early paper in 2002. He was kind enough to send PDFs on his work at every request.

Aquilops americanus is not a neoceratopsian

Aquilops americanus was described 
by Farke et al. 2018, “The taxon is interpreted as a basal neoceratopsian closely related to Early Cretaceous Asian taxa, such as Liaoceratops and Auroraceratops.” This may be due to taxon exclusion.

Aquilops is much more primitive
than neoceratopsians, like Chasmosaurus and Triceratops, according to the large reptile tree (LRT, 1304 taxa; subset Fig. 1) which nests Aquilops between Laquintasaura and Hexlinusaurus, both basal to the psittacosaur – ceratopsian split. Both were excluded from the Farke et al. study.

Figure 1. Aquilops nests at the base of psittacosaurs + ceratopsians in the LRT. Pachycephalosaurs, like Stegoceras, are not the sisters to ceratopsians.

Figure 1. Subset of the LRT focusing on the Ornithischia where Aquilops nests at the base of psittacosaurs + ceratopsians in the LRT. Pachycephalosaurs, like Stegoceras, are not the sisters to ceratopsians.

Distinct from Laquintasaura,
Aquilops has an eagle-like hooked rostral bone (Fig. 2) and retains an antorbital fenestra with fossa. It was likely a biped, based on phylogenetic bracketing. Here (Fig. 1) skull only Auroraceratops nests with skull-less Stenopelix at the base of the Neoceratopsia. Liaoceratops nests with Psittacosaurus and Yinlong. We’ll look at them in future posts.

Figure 2. Aquilops skull as restored and as discovered.

Figure 2. Aquilops skull as restored and as discovered. The squamosal has been artificially restored with a parietal shield in the restoration, traits not preserved in the partial material. 

References
Farke AA, Maxwell WD, Cifelli RL and Wedel MJ 2014. A Ceratopsian Dinosaur from the Lower Cretaceous of Western North America, and the Biogeography of Neoceratopsia. PLoS ONE. 9 (12): e112055. doi:10.1371/journal.pone.0112055

wiki/Aquilops
https://p3d.in/G34T8+welcome
https://samnoblemuseum.ou.edu/collections-and-research/vertebrate-paleontology/discovering-aquilops-americanus/

Dr. Baron tip-toes around the radiation of dinosaurs

Last year, Dr. Matthew Baron,
not even a year out from his PhD thesis, placed himself in the middle of controversy when Baron, Norman and Barrett 2017 resurrected the clade Ornithoscelida, wrongly uniting plant-eating Ornithischia with meat-eating Theropoda to the exclusion of plant-eating Sauropodomorpha, an invalid (due to taxon exclusion) hypothesis of relationships, we discussed earlier here.

Dr. Baron guessed,Maybe Ornithischia is actually so far removed from the base of the dinosaur tree that no studies, including my own, have been able to properly place them… Its an intriguing thought and one that needs examining properly.” By his own words, Dr. Baron is not yet an authority on the subject. That authority can only come from a wide gamut analysis that minimizes taxon exclusion, like the large reptile tree (LRT, 1236 taxa), which is something that anyone can produce. As noted last year (see citations below), Dr. Baron’s team excluded several relevant taxa.

Figure 2. Look familiar? Here are the pelves of Jeholosaurus and Chilesaurus compared. As discussed earlier, this is how the ornithischian pelvis evolved from that of Eoraptor and basal saurorpodomorpha.

Figure 1. Look familiar? Here are the pelves of Jeholosaurus and Chilesaurus compared. As discussed earlier, this is how the ornithischian pelvis evolved from that of Eoraptor and basal phytodinosauria.

Later Langer et al. 2017 argued against the Baron, Norman and Barrett interpretation. Baron, Norman and Barrett agued back, stating in Baron’s summary, “Langer et al.’s response showed that the alternative arrangement, that preserved the traditional model, was not statistically significantly different to our own hypothesis, and that was with much of our data having been altered, in ways that we perhaps disagree with strongly.”

Baron is correct is noting that Seeley’s original division, uniting sauropodomorphs with theropods based on pelvis orientation “just because a subgroup have gone on to lose a feature that was the ancestral condition for the wider group, it does not mean that we can then say that the other subgroups who have ‘hung on’ to the feature should be grouped together to the exclusion of the experimental group, at least based on that feature’s absence/presence, without other evidence.” Plus it would be one more example of pulling a Larry Martin.

Unfortunately
Dr. Baron pulls out a bad example as his example of the above. He states, “In fact, Cetacea is more closely related to Carnivora than either group are to the Primates.” In counterpoint, in the large reptile tree (LRT, 1236 taxa) there is no clade “Cetacea.” Odontoceti arise from tenrecs and elephant shrews. Mysticeti arise from hippos and desmostylians. Carnivora split apart in the first dichotomy in Eutheria. Thus all other eutherians, including primates, odontocetes and mysticetes have a last common ancestor that is not a member of the Carnivora.

Unfortunately
Dr. Baron bases the above quote on a phylogenetic error when he states, “Like I said before, you need to look at TOTAL EVIDENCE to come to this quite obvious conclusion, which means focusing on more anatomical evidence.” While this may sound reasonable and correct, a focus on anatomical evidence may lead to confusion due to convergence. Bottom line, it is more important to look at the phylogenetic placement of a taxon in order to determine what it is. This has to be done in the context of a wide gamut analysis that minimizes taxon exclusion using at least 150 (sometimes multi-state) characters (the LRT uses 238). Otherwise you’re cherry-picking taxa, something Baron, Norman and Barrett were guilty of by excluding bipedal crocs and several basal dinosaurs from their study (and we know this since the LRT includes them). Baron also cherry-picks traits in part 3 of his argument, pulling a Larry Martin several times in doing so. In a good phylogenetic analysis, like the LRT, you’ll see a gradual accumulation of traits. That means you’ll get a pubis with a transitional phase, a tiny predentary and other traits in gradual accumulation among the outgroups to Ornithischians.

Figure 1. Chilesaurus and kin, including Damonosaurus and basal phytodinosauria.

Figure 2. Chilesaurus and kin, including Damonosaurus and basal phytodinosauria.

Baron promises
“I will eat my shoes!” if Seeley’s dichotomy is correct. That’s an easy promise to make knowing there is a third hypothesis out there: the Theropod/Phytodinosaur dichotomy presented by Bakker (1986) and confirmed by the LRT in 2011.

Pertinent to this discussion
sometimes what a paleontologist does not say about a particular subject can be more important that what a paleontologist does say. I lump taxon exclusion and citation exclusion in the category of ‘what is not said.’

References
Bakker RT 1986. The Dinosaur Heresies.New Theories Unlocking the Mystery of the Dinosuars and Their Extinction. Illustrated. 481 pages. William Morrow & Company.
Baron MG and Barrett PM 2017. A dinosaur missing-link? Chilesaurus and the early evolution of ornithischian dinosaurs. Biology Letters 13, 20170220.
Baron MG, Norman DB and Barrett PM 2017.
A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature 543: 501–506;  doi:10.1038/nature21700
Baron MG, Norman DB and Barrett PM 2017. Baron et al. reply. Nature 551: doi:10.1038/nature24012
Langer et al. (8 co-authors) 2017. Untangling the dinosaur family tree. Nature 551: doi:10.1038/nature24011
Novas FE et al. 2015. An enigmatic plant-eating theropod from the Late Jurassic period of Chile. Nature 522(7556), 331.

Relevant blogposts and theses from Dr. Baron:

https://www.academia.edu/36002282/THE_ORIGIN_AND_EARLY_EVOLUTION_OF_THE_DINOSAURIA

What I think about Ornithischia

Thoughts on Ornithoscelida … over one year on … (part 1)

Thoughts on Ornithoscelida … over one year on … (part 2)

Chilesaurus – what is it?

https://pterosaurheresies.wordpress.com/2017/03/23/new-radical-dinosaur-cladogram-baron-norman-and-barrett-2017

https://pterosaurheresies.wordpress.com/2017/03/24/baron-2017-21-unambiguous-theropodornithischian-synapomorphies-dont-pan-out/

https://pterosaurheresies.wordpress.com/2015/06/25/the-dinosaur-heresies-nytimes-book-review-from-1986/

https://pterosaurheresies.wordpress.com/2017/11/03/dinosaur-family-tree-langer-et-al-responds-to-baron-et-al-2017-in-nature/

https://pterosaurheresies.wordpress.com/2017/08/16/you-heard-it-here-first-chilesaurus-is-a-basal-ornithischian-confirmed/