SVP 3 – The “more basal” ornithischian, Haya

News from
Barta and Norell (2015) on Haya, a basal ornithischian that nests with the L:ate Triassic Pisanosaurus in the large reptile tree despite the late survivor appearance of Haya in the Late Cretaceous.

From the abstract
“As one of the best-represented basal ornithischians, Haya griva forms a case study for investigating the influence of intraspecific variation on the hypothesized relationships of taxa. We scored nine specimens, including a juvenile. One analysis treated each specimen as a separate operational taxonomic unit (OTU), and the other treated all H. griva specimens as a single polymorphic composite OTU. The analysis with multiple H. griva OTUs resolved this taxon as sister to all orodromine and thescelosaurine ornithischians on the strict consensus tree, whereas the analysis with a single polymorphic composite OTU placed H. griva as an indeterminate basal neornithischian on a less-resolved strict consensus tree. The juvenile specimen groups with all other Haya specimens in the specimen-level analysis, suggesting that the current placement of H. griva is robust to at least some degree of ontogenetic variation. Collectively, these results suggest that 1) Haya griva exhibits a complex mosaic of character states relative to other basal ornithischians and may occupy a more basal position than previously thought, 2) proposed ornithischian dinosaur relationships remain unstable, 3) the phylogenetic placement of even well understood taxa may be altered when new specimens become available and a fuller range of variation is taken into account.”

Figure 1. Haya in lateral view.

Figure 1. Haya in lateral view.

Very interesting!
Haya in a more basal position than previously thought… that’s what you’ll find at the large reptile tree. Nice to get at least tentative validation.

The abstract does not say
whether or not the basal ornithischians, Daemonosaurus, Chilesaurus and Pisanosaurus were tested along with Haya. The first two originally were considered aberrant theropods by traditional paleontologists. Maybe their addition will settle the “unstable” aspect of their cladogram. It doesn’t hurt to try.

References
Barta DE and Norell MA 2015.
New specimens of Haya griva: impacts of novel anatomical information and specimen-level analysis on Ornithischian dinosaur phylogeny. Journal of Vertebrate Paleonotology Abstracts.

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