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The assembly of the avian body plan (Cau 2018) pt. 2 of 3

Wednesday, May 16, 2018 11:42
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Yesterday we looked at part 1 of the Cau 2018 cladogram of theropods (including birds). Certain taxa within this study were new to me, so I added several to the the large reptile tree (LRT, 1213 taxa). Today we’ll continue with Node 9, still within the Huxley stage of theropod evolution.

Figure 2. Zuolong skull revised with a backward tilting lacrimal and other minor modifications. ” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2018/05/zuolong-skull2.jpg?w=584&h=356?w=300″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2018/05/zuolong-skull2.jpg?w=584&h=356?w=584″ class=”size-full wp-image-30869″ src=”https://pterosaurheresies.files.wordpress.com/2018/05/zuolong-skull2.jpg?w=584&h=356″ alt=”Figure 2. Zuolong skull revised with a backward tilting lacrimal and other minor modifications.” width=”584″ height=”356″ srcset=”https://pterosaurheresies.files.wordpress.com/2018/05/zuolong-skull2.jpg?w=584&h=356 584w, https://pterosaurheresies.files.wordpress.com/2018/05/zuolong-skull2.jpg?w=150&h=91 150w, https://pterosaurheresies.files.wordpress.com/2018/05/zuolong-skull2.jpg?w=300&h=183 300w, https://pterosaurheresies.files.wordpress.com/2018/05/zuolong-skull2.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Zuolong skull revised with a backward tilting lacrimal and other minor modifications.

Node 9. Tetanurae: (Zuolong + Chilesaurus + Neotetanurae). Adding Zuolong to the LRT nests it as a basal theropod, basal to the rarely tested taxa in the Segisaurus + Marasuchus + Procompsognathus clade (Fig. 2). Zuolong is the first of these with a relatively complete skull. Cau 2018 nest Zuolong and the phytodinosaur, Chilesaurus, with Neotetanurae apparently by excluding certain relevant taxa.

Figure 1. Chilesaurus and kin, including Damonosaurus and basal phytodinosauria. ” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2015/04/chilesaurus-and-kin88.jpg?w=584&h=858?w=204″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2015/04/chilesaurus-and-kin88.jpg?w=584&h=858?w=584″ class=”size-full wp-image-18407″ src=”https://pterosaurheresies.files.wordpress.com/2015/04/chilesaurus-and-kin88.jpg?w=584&h=858″ alt=”Figure 1. Chilesaurus and kin, including Damonosaurus and basal phytodinosauria.” width=”584″ height=”858″ srcset=”https://pterosaurheresies.files.wordpress.com/2015/04/chilesaurus-and-kin88.jpg?w=584&h=858 584w, https://pterosaurheresies.files.wordpress.com/2015/04/chilesaurus-and-kin88.jpg?w=102&h=150 102w, https://pterosaurheresies.files.wordpress.com/2015/04/chilesaurus-and-kin88.jpg?w=204&h=300 204w, https://pterosaurheresies.files.wordpress.com/2015/04/chilesaurus-and-kin88.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2. Chilesaurus and kin, including Damonosaurus and basal phytodinosauria. No close relatives of theropods here!

Node 10. Chilesaurus + Neotetanurae: (See node 9). Cau also reports, “The parsimony analysis confirms the basal tetanuran affinities of the enigmatic Chilesaurus and dismisses ornithischian relationships suggested by Baron & Barrett (2017).” This is only true base on taxon exclusion. Add back the missing taxa, like Daemonosaurus , Jeholosaurus and Haya and the tree topology will change.

Figure 1. The origin of birds cladogram according to Cau 2018. Taxon exclusion forces a mixup of basal taxa. ” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2018/05/cau2018cladogram.jpg?w=584&h=1415?w=124″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2018/05/cau2018cladogram.jpg?w=584&h=1415?w=423″ class=”size-full wp-image-30799″ src=”https://pterosaurheresies.files.wordpress.com/2018/05/cau2018cladogram.jpg?w=584&h=1415″ alt=”Figure 1. The origin of birds cladogram according to Cau 2018. Taxon exclusion forces a mixup of basal taxa. ” width=”584″ height=”1415″ srcset=”https://pterosaurheresies.files.wordpress.com/2018/05/cau2018cladogram.jpg?w=584&h=1415 584w, https://pterosaurheresies.files.wordpress.com/2018/05/cau2018cladogram.jpg?w=62&h=150 62w, https://pterosaurheresies.files.wordpress.com/2018/05/cau2018cladogram.jpg?w=124&h=300 124w, https://pterosaurheresies.files.wordpress.com/2018/05/cau2018cladogram.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. The origin of birds cladogram according to Cau 2018. Taxon exclusion forces a mixup of basal taxa.

Node 11. Neotetanurae (Carnosauria + Coelurosauria): The Cau tree and LRT share many taxa here, including Allosaurus with Sinraptor and Acrocanthosaurus. The Cau tree has only one Compsognathus. The LRT has two, each at the base of its own clade. The Cau tree nests Megalosaurus between the phytodinosaur, Chilesaurus, and the small compsognathid, Aorun, which is odd on the face of it (= no gradual accumulation of traits).

Node 12. Coelurosauria: The LRT indicates that Sinocalliopteryx does not belong in this clade, as Cau recovers it, but Sinocalliopteryx nests much more primitively, basal to Coelophysis and kin.

Nodes 13. Compsognathid grade + Tyrannoraptora: The spinosaurs and kin are not present in the Cau taxon list. When present these long rostrum taxa attract Guanllong and Megaraptor to more primitive theropods, away from tyrannosaurs, despite convergent traits.

Node 14. Sinocalliopteryx + Tyrannoraptora: See Node 13.

Node 15. Tyrannoraptora: (Tyrannosauroids and maniraptoromorphs) See Node 13.

Node 16. Maniraptoromorpha: (includes Vultur, excludes Tyrannosaurus). This definition is a little vague. Wish it had at least one included basal taxon. In the Cau tree Coelurus is a basal taxon. Unfortunately, too little of it is known to add it to the LRT.

Node 17. Ornitholestes + Maniraptoriformes: Distinct from the Cau tree, Ornitholestes is basal to microraptorids and tyrannosaurs, as well as dromaeosaurs, troodontids and birds.

Node 18. Maniraptoriformes: (Ornithomimosauria + Maniraptora). Distinct from the Cau tree, ornithomimosaurs in the LRT are derived directly from the holotype of Compsognathus, separate from oviraptorids and dromaeosaurs, closer to tyrannosaurs and kin. The LRT nests Ornitholestes and kin on the bird side of therizinosaurus + oviraptorids. The Cau tree does the opposite.

Figure 1. Cladogram subset of the LRT focusing on Theropoda. ” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2018/02/theropod_clades588.jpg?w=584&h=1867?w=94″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2018/02/theropod_clades588.jpg?w=584&h=1867?w=320″ class=”size-full wp-image-29466″ src=”https://pterosaurheresies.files.wordpress.com/2018/02/theropod_clades588.jpg?w=584&h=1867″ alt=”Figure 1. Cladogram subset of the LRT focusing on Theropoda.” width=”584″ height=”1867″ srcset=”https://pterosaurheresies.files.wordpress.com/2018/02/theropod_clades588.jpg?w=584&h=1867 584w, https://pterosaurheresies.files.wordpress.com/2018/02/theropod_clades588.jpg?w=47&h=150 47w, https://pterosaurheresies.files.wordpress.com/2018/02/theropod_clades588.jpg?w=94&h=300 94w, https://pterosaurheresies.files.wordpress.com/2018/02/theropod_clades588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2. Cladogram subset of the LRT focusing on Theropoda.

Part 3 tomorrow.

References
Cau A 2018. The assembly of the avian body plan: a 160-million-year long process. Invited Paper, Bollettino della Societa Paleontologica Italiana 57(1):1–25.



Source: https://pterosaurheresies.wordpress.com/2018/05/17/the-assembly-of-the-avian-body-plan-cau-2018-pt-2-of-3/

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