TABLE 1. Key cranial characteristics of a variety of istiodactylids. A ‘0’ indicates a character is absent, ‘1’ is present, and ‘-” is unknown. *The anterior tip of the jaw is missing and this is estimated for this calculation. **The tip of the jaw is missing and more teeth were likely present, probably 12 in total. ‘’ I. latidens has 25 teeth in the lower jaw with a tooth positioned medially at the front. Information taken from Howse et al., 2001; Andres and Ji, 2006; Wang et al., 2005, 2011; Lü et al., 2008; Arbour and Currie, 2011; Zhou et al., 2019 and examination of BMNH R8377 (referred specimen of I. latidens) and IVPP V 13288 (holotype of Nurhachius ignaciobritoi).
| L. xingzhe | I. latidens | I. sinensis | Longchenpterus | N. ignaciobritoi | N. luei | Liaoxipterus | Hongshanopterus | |
| Dorsal expansion / upturn of anterior rostrum | 0 | 0 | 1 | 1 | 1 | 1 | - | - |
| Length-height ratio of rostrum anterior and ventral to NAOF | 0.11* | 0.14 | 0.17 | 0.09 | 0.10 | 0.09 | - | - |
| Posterior teeth very well-spaced in the jaw | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 1 |
| Number of teeth posterior to the NAOF in the upper jaw | 1 | 0 | 1 | 0 | 0 | 0 | - | - |
| Number of teeth in the upper jaw (one side) | 9** | 12 | 15 | 14 | 9 | 12 | - | 17-19 |
| Number of teeth in the lower jaw (one side) | 12 | 12/13’’ | 15 | 13 | 9 | 11 | 13 | - |
| Relatively long and thin symphysis: (over 4:1) | 1 | 0 | - | 1 | 0 | 0 | 0 | - |
| Long and narrow rami of the mandible in dorsal view (20:1) | 1 | - | - | 0 | 0 | - | 0 | - |
