A new ornithischian, Changmiania, enters the LRT

Meet a new fossorial fossil dinosaur,
perfectly preserved in its own burrow.

Yang et al. 2020 bring us
self-buried specimens of Changmiania liaoningensis (Yixian, Early Creteceous; Figs. 1–3).

Figure 1. Changmiania in situ and illustrated in situ from Yang et al. 2020.

Figure 1. Changmiania in situ and illustrated in situ from Yang et al. 2020.

The authors nest this ornithischian
as the basalmost member of the clade Ornithopoda (= duckbills, etc.; Fig. y).

Figure y. Cladogram of the Ornithischia from Yang et al. 2020. Colors added. Green= related taxa in the LRT. Yellow = taxa share with the LRT.

Figure y. Cladogram of the Ornithischia from Yang et al. 2020. Colors added. Green= related taxa in the LRT. Yellow = taxa share with the LRT. Compare to figure x which includes more outgroup taxa to polarize the basal taxa.

By contrast,
the large reptile tree (LRT, 1733+ taxa; subset Fig. x) nests Changmiania (Figs. 1–3) with Kulindadromeus (Fig. 4) and Heterodontosaurus (Fig. 5). That’s several nodes apart from the clade Ornithopoda in the LRT (Fig. x).

Figure x. Subset of the LRT focusing on Ornithischia. This cladogram differs considerably from that published in Yang et al. 2020.

Figure x. Subset of the LRT focusing on Ornithischia. This cladogram differs considerably from that published in Yang et al. 2020. Here Haya is a basal ornithischian. In Yang et al. Haya is deep within the Ornithopoda.

Digging (fossorial behavior)
traits found in Changmiania proposed by the authors include:

  1. fused premaxillae
  2. nasal laterally expanded overhanging the maxillas
  3. shortened neck formed by only six cervical vertebrae;
  4. neural spines of the sacral vertebrae completely fused together, forming a craniocaudally-elongated continuous bar;
  5. fused scapulocoracoid with prominent scapular spine;
  6. and paired ilia symmetrically inclined dorsomedially, partially
    covering the sacrum in dorsal view.
Figure 2. Changmiania skull in dorsal view.

Figure 2. Changmiania skull in dorsal view from Yang et al. 2020. Colors added here.

Figure 3. Changmiania skull in lateral view from Yang et al. 2020. Colors added here.

Figure 3. Changmiania skull in lateral view from Yang et al. 2020. Colors added here.

Several ornithischian taxa
(Orodromeus, Oryctodromeus, and Zephyrosaurus) have also demonstrated (or suggested by phylogenetic bracketing) fossorial behavior. Heterodontosaurus (Figs. 5, 6) shares traits #1, 2 and 3. Heterodontosaurus has longer fingers #2 and #3 (for digging?).

Figure 1. Kulindadromaeus, a sister to Heterodontosaurus with proto-feathers. Images from and traced from Godefroit et al. 2014. Since theropods and heterodontosaurs both had something like feathers, if they were the same kind of feathers, their last common ancestor had feathers. That last common ancestor was a herrerasaur or its proximal predecessor. Note the Godefroit et al. skull does not match their description but has a standard maxilla ascending process. See color overlays for correct ed interpretation.

Figure 4. Kulindadromaeus, a sister to Heterodontosaurus with proto-feathers. Images from and traced from Godefroit et al. 2014. Since theropods and heterodontosaurs both had something like feathers, if they were the same kind of feathers, their last common ancestor had feathers. That last common ancestor was a herrerasaur or its proximal predecessor. Note the Godefroit et al. skull does not match their description but has a standard maxilla ascending process. See color examples for correct ed interpretation. Click to enlarge.

Figure 7. Heterodontosaurus skull. Note the fused premaxillae, overhanging nasals and pmx/mx notch for a lower fang.

Figure 5. Heterodontosaurus skull. Note the fused premaxillae, overhanging nasals and pmx/mx notch for a lower fang. The general layout of the skull is very much like that of Changmiania. See figures 2 and 3.

Figure 1. Heterodontosaurus with feather quills arising from the lower back, sacrum and proximal tail.Figure 1. Heterodontosaurus with feather quills arising from the lower back, sacrum and proximal tail.

Figure 6. Heterodontosaurus with feather quills arising from the lower back, sacrum and proximal tail.

It’s worth noting
that many extant birds dig burrows, too. They use their bills to peck and their feet to sweep. Progress is often slow. Here’s an online article discussing birds that use and dig burrows.

Figure 7. Changmiania, both specimens in situ.

Figure 7. Changmiania, both specimens in situ.

Here’s a YouTube video
of a belted kingfisher working on its own burrow. Much is not shown, but the feet are back-kicking out the rubble, presumably produced by the pecking of the strong beak at the back wall of the burrow.

References
Yang Y, Wu W, Dieudonne P-E and Godefroit P 2020. A new basal ornithopod dinosaur from the Lower Cretaceous of China. PeerJ 8:e9832 DOI 10.7717/peerj.9832

Changmiania publicity:
naturalsciences.be/en/news/item/19274