Re: [dinosaur] Changmiania, new ornithopod from Lower Cretaceous of China (free pdf)

[Tim Williams <tijawi@gmail.com>]

The phylogeny in this paper is interesting, for a number of reasons. If _Changmiania_ is a fossorial/burrowing ornithopod, then it suggests this behavior is primitive for Ornithopoda; this is because the next outgroup (Orodrominae) also comprises fossorial burrowers (as the paper makes clear). Further, it's been suggested elsewhere that _Drinker_ lived in burrows, although this has yet to be published (and likely never will):

http://dml.cmnh.org/1998Mar/msg00313.html

_Drinker_ has since been referred to _Nanosaurus_ (Carpenter and Galton, 2018). According to Yang et al.'s phylogeny, _Nanosaurus_ belongs to a more derived clade, an unnamed sister group to Clypeodonta.

Also noteworthy (and novel, AFAIK) is that _Kulindadromeus_ comes up as the sister taxon to Marginocephalia (Ceratopsia + Pachycephalosauria), outside Ornithopoda.

Finally, I don't understand why Yang et al. use so many subfamily-based names for their ornithopod clades: Orodrominae, Jeholosaurinae, Parksosaurinae. Subfamilies are subdivisions of families - but Yang et al. do not use them this way.Â

Orodrominae should be Orodromidae - the attribution doesn't change (the subfamily and family are both Brown et al., 2013). Sensibly, Brown et al. (2013) explicitly defined Orodrominae as being a clade of thescelosaurids. Since Yang et al. recovered Orodrominae outside Thescelosauridae, there is no reason to retain Orodrominae. Â

Jeholosaurinae should be Jeholosauridae, following Han et al. (2012).Â

Parksosaurinae should be Hypsilophodontidae, because it includes _Hypsilophodon_. There is already a family Hypsilophodontidae available, and has been for donkey's years (it goes back to Dollo, 1882).

The use of a stand-alone subfamily also popped up in the recent monograph on pennaraptoran theropods (Bulletin of the AMNH), where Anchiornithinae was used in preference to Anchiornithidae, even though Anchiornithinae didn't belong in any family: it was recovered as the most basal clade of the Avialae. The reason given was that "Anchiornithinae: we use this stem-based taxon containing _Anchiornis_ instead of Anchiornithidae because the former was proposed earlier [Xu et al. 2016])". But if Anchiornithinae becomes Anchiornithidae, Xu et al. (2016) still get credit (despite Foth and Rauhut [2017] later naming Anchiornithidae). It's not clear why Xu et al. (2016) chose to call this clade Anchiornithinae rather than Anchiornithidae; at the time, the authors may have believed _Anchiornis_ was a troodontid.

I think the basic problem is that coordinated family-level taxa are hierarchial (superfamily, family, subfamily, tribe), so this hierarchy should be taken into account when coming up with phylogenetic definitions for these clades. Often this doesn't happen, so subfamilies can end up outside of families (as happened with Yang et al.); and families can end up inside other families (as has happened with some hadrosaur trees, which have Saurolophidae inside Hadrosauridae).

Â

On Wed, Sep 9, 2020 at 12:59 AM Ben Creisler <bcreisler@gmail.com> wrote:

Ben Creisler

bcreisler@gmail.com

A new paper with free pdf:

Changmiania liaoningensis gen. et sp. nov.

ÂYuqing Yang, Wenhao Wu, Paul-Emile Dieudonnà & ÂPascal Godefroit (2020)
A new basal ornithopod dinosaur from the Lower Cretaceous of China.
PeerJ 8:e9832
doi: https://doi.org/10.7717/peerj.9832
https://peerj.com/articles/9832/

A new basal ornithopod dinosaur, based on two nearly complete articulated skeletons, is reported from the Lujiatun Beds (Yixian Fm, Lower Cretaceous) of western Liaoning Province (China). Some of the diagnostic features of Changmiania liaoningensis nov. gen., nov. sp. are tentatively interpreted as adaptations to a fossorial behavior, including: fused premaxillae; nasal laterally expanded, overhanging the maxilla; shortened neck formed by only six cervical vertebrae; neural spines of the sacral vertebrae completely fused together, forming a craniocaudally-elongated continuous bar; fused scapulocoracoid with prominent scapular spine; and paired ilia symmetrically inclined dorsomedially, partially covering the sacrum in dorsal view. A phylogenetic analysis places Changmiania liaoningensis as the most basal ornithopod dinosaur described so far. It is tentatively hypothesized that both Changmiania liaoningensis specimens were suddenly entrapped in a collapsed underground burrow while they were resting, which would explain their perfect lifelike postures and the complete absence of weathering and scavenging traces. However, further behavioural inference remains problematic, because those specimens lack extensive sedimentological and taphonomic data, as it is also the case for most specimens collected in the Lujiatun Beds so far.

Virus-free. www.avg.com