Jianianhualong tengi (Xu et al. 2017; Early Cretaceous; DLXH 1218) originally considered a non-avian troodontid, Jianianhualong nests bertween Sapeornis and Archaeopteryx recurva. It is a troodontid-like bird, not a bird-like troodontid. Note the odd scapula shape, like that in Sapeornis. Note the retrovered pedal digit 1, showing this taxon was derived from perching birds. The tall naris and long tibia are autapomorphies.

Xu et al. 2014 made a headline out of the asymmetric feathers found with Jianianhualong. In the present context, Jianianhualong is derived from volant ancestors. So asymmetry is not exceptional, but expected. This is the earliest known large flightless bird.

Liaoningventor curriei (Shen et al. 2017; DNHM D3012; Dalian Natural History Museum; Early Cretaceous) was also originally described as a non-avian troodontid, but nests with Jianianhualong as a bird.

Solnhofen specimen #11 - private - nests at the base of the genus Sapeornis (Foth et al 2014).

In the above illustration
the following taxa are non-avian troodontids: Eosinopteryx, Sinovenator, Anchiornis and Sinornithoides. They are shown for comparison to the other taxa, early flightless birds.

Liaoningvenator and Jianianhualong bird traits (distinct from troodontids):

1. Ventral aspect of premaxilla > 1/3 preorbit length
2. Ascending process of premaxilla extends beyond naris and contacts frontals
3. Lacrimal deeper than maxilla
4. Major axis of naris 30-90º
5. Posterolateral premaxilla absent (also in Xiaotingia and Eosinopteryx)
6. Nasals not longer than frontals (also in Xiaotingia and Eosinopteryx)
7. Antorbital fenestra without fossa
8. Manual mc2 and 3 do not align with joints on digit 1
9. Metatarsal 5 not shorter than pedal digit 5

 

Sapeornis chaoyangensis (Zhou and Zhang 2002. 2003; Early Cretaceous; IVPP V13276) is a basal ornithurine bird, the clade that gave rise to modern birds. The short tail was tiped with a pygostyle and afan of feathers. The coracoids were oddly wide and relatively short. Manual digit 3 is a vestige. The claws on the remaining digits are all raptorial. Another specimen, DNHM-F3078 (Gao et al. 2012) was smaller, considered a juvenile based on bone texture, lived 3-5 million years earlier and a pubic boot.

Foth C, Tischlinger H and Rauhut OWM 2014. New specimen of Archaeopteryx provides insights into the evolution.of pennaceous feathers. Nature 511:79–83.DOI: 10.1038/nature13467

Gao C, Chiappe LM, Zhang F, Pomeroy DL, Shen C, Chinsamy A and Walsh MO 2012. A subadult specimen of the Early Cretaceous bird Sapeornis chaoyangensis and a taxonomic reassessment of sapeornithids. Journal of Vertebrate Paleontology. 32(5): 1103–1112.

Shen C-Z, Zhao B, Gao C-L, Lü J-C and Kundrat 2017. A New Troodontid Dinosaur (Liaoningvenator curriei gen. et sp. nov.) from the Early Cretaceous Yixian Formation in Western Liaoning Province. Acta Geoscientica Sinica 38(3):359-371.

Xu X, Currie P, Pittman M, Xing L, Meng QW-J, Lü J-C, Hu D and Yu C-Y 2017. Mosaic evolution in an asymmetrically feathered troodontid dinosaur with transitional features. Nature Communications DOI: 10.1038/ncomms14972.

Zhou Z and Zhang F-C 2003. Anatomy of the primitive bird Sapeornis chaoyangensis from the Early Cretaceous of Liaoning, China. Canadian Journal of Earth Sciences 40(5): 731–747.

wiki/Sapeornis
wiki/Jianianhualong
wiki/Liaoningvenator