Sinopterus IVPP V 23388 in detail

Zhang et al. 2019 bring us
a beautiful, virtually complete pterosaur specimen from the Early Cretaceous of China: Sinopterus atavismus (Fig. 1). Despite a thorough description, some small parts here and there were overlooked.

Figure 1. Sinopterus atavismus, matrix removed. Snout tip, fingers and toes enlarged to show detail.

Figure 1. Sinopterus atavismus, matrix removed. Snout tip, fingers and toes enlarged to show detail. The lack of fusion in the scapula + coracoid has nothing to do with ontogeny, just phylogeny, as in other lepidosaurs

‘Toothless’ pterosaurs retain one tooth
at the tip of their premaxilla and dentary (Fig. 1). We looked at that trait earlier here in 2011. Mainstream paleontologists still don’t look for it. The evolution of these procumbent teeth are documented in tiny Solnhofen ancestors.

Manual digit 5 is not lost,
but it remains as a tiny vestige in pterosaurs. In this case manual digit 5 was so prominent Zhang et al. traced it without labeling it. Here it is (Fig. 1) in situ and unfolded. We looked at that trait earlier here in 2011. Mainstream paleontologists still don’t look for it.

Pedal digit 5 likes to tuck itself behind the ankle
in situ as it does here (Fig. 1). It was not hard to find, if you don’t set out to ignore it. We looked at that trait earlier here in 2012 (Peters 2011). Mainstream paleontologists still don’t look for it.

Extended tail vertebrae are easy to overlook,
but if you look for them, you will find them on this pterodactyloid-grade tapejarid. We looked at that trait earlier here in 2013. Mainstream paleontologists still don’t look for it.

Figure 2. The new IVPP Sinopterus specimen in situ with original interpretation and DGS colors used to find the 'missing' pteroids. The cervicals are numbered anew. The sternal complex (not just the sterum) borders are identified or reidentified.

Figure 2. GIF animation of the new IVPP Sinopterus specimen in situ with original interpretation and DGS colors used to find the ‘missing’ pteroids. The cervicals are numbered anew. The sternal complex (not just the sterum) borders are identified or reidentified.

Where are the missing pteroids?
Zhang et al. report the pteroids and all sesamoids are missing from this specimen. Digital Graphic Segregation (DGS) is helpful by eliminating all the other bones by color until the pteroids appear by default (Fig. 2).

Figure 3. Sinopterus skulls presented by Zhang et al. 2019.

Figure 3. Sinopterus skulls presented by Zhang et al. 2019.

Juvenile?
The new IVPP V 23388 specimen is considered a juvenile, despite being one of the largest Sinopterus specimens (Fig. 3). The lack of fusion in the scapula + coracoid has nothing to do with ontogeny, just phylogeny, as in other lepidosaurs, as we learned earlier here.


References

Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification Ichnos 18(2):114-141.
Zhang X-J, Jiang S-X, Cheng X and Wang X-L 2019.
New Material of Sinopterus (Pterosauria, Tapejaridae) from the Early Cretaceous Jehol Biota of China. Anais da Academia Brasileira de Ciências (2019) 91(Suppl. 2): e20180756 (Annals of the Brazilian Academy of Sciences). Printed version ISSN 0001-3765 / Online version ISSN 1678-2690
http://dx.doi.org/10.1590/0001-376520192018756

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