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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