SDUST-V1003 is not Forfexopterus

Zhou, Wang and Zhou 2020 describe a new pterosaur specimen
based on a single articulated wing (SDUST-V1003; (Fig. 1), which they assigned to Forfexopterus (Fig. 2)… with this odd reservation: “It is only about 75% the size of the immature holotype.”

By contrast
in the large pterosaur tree (LPT, 251 taxa) the SDUST-V1003 (Fig. 1) nests with a slightly earlier and smaller Yixian Formation pre-azhdarchid pterosaur, Beipiaopterus (Fig. 3).

Figure 1. SDUST-V1003, formerly Forfexopterus, in situ and reconstructed.

Figure 1. SDUST-V1003, formerly Forfexopterus, in situ and reconstructed. Note the slender free fingers and giant unguals. The radius was taphonomically displaced. A tiny wing finger claw is present. Metacarpus 4 was split and splintered. perhaps during axial wing rotation during taphonomy.

Zhou, Wang and Zhou 2020 considered the following pterosaurs
ctenochasmatids. Most are not when you add more taxa, as in the LPT.

  1. EosipterusElanodactylus – Germanodactylidae
  2. Feilongus, Pterofiltrus, MoganopterusCycnorhamphidae
  3. Beipiaopterus, Forfexopterus  pre-Azhdarchidae
  4. Gegepterus, Gladocephaloideus – Ctenochasmatidae
  5. Cathayopterusnot tested yet
Figure 2. Forfexopterus compared to sisters Huanhepterus and Ardeadactylus and the BYU specimen of Mesadactylus.

Figure 2. Forfexopterus compared to sisters Huanhepterus and Ardeadactylus and the BYU specimen of Mesadactylus.

The SDUST pterosaur is known from
a slab containing a complete wing (lacking manual 2.2, 2.3, 3.2, 3.3 and 3.4; Fig. 1) with somewhat different proportions than the holoytpe Forfexopterus (Fig 2), The differences turn out to be enough to separate the two in the LPT. The referred specimen (SDUST V1003) nests two nodes apart from Forfexopterus, so the two cannot be congeneric.

Figure 3. Beipiaopterus to scale with the SDUST pterosaur. Beipiaopterus wing enlarged to match the SDUST pterosaur.

Figure 3. Beipiaopterus to scale with the SDUST pterosaur. Beipiaopterus wing enlarged to match the SDUST pterosaur. Note how relatively tiny the free fingers are in these taxa.

From the Zhou, Wang and Zhou abstract:
“In the Jehol Biota, the filter-feeding ctenochasmatid pterosaurs flourished with a high biodiversity. Here, we report a new wing skeleton of the ctenochasmatid Forfexopterus from the Early Cretaceous Jiufotang Formation in Jianchang, western Liaoning, China. The specimen exhibits the sole autapomorphy, the first wing phalanx shorter than the second and longer than the third.”

Other pterosaurs also share this trait. As long-time readers will readily realize, Zhou, Wang and Zhou were “Pulling a Larry Martin” by relying on this single trait, or a dozen traits.

“Interestingly, it exhibits a skeletal maturity with co-ossified elements, but it is only about 75% the size of the immature holotype.”

Here the authors reveal they were misinformed on the subject of pterosaur  phylogeny and ontogeny Pterosaurs are tritosaur lepidosaurs with isometric growth patterns and phylogenetic (not ontogenetic) ossification patterns. Thus for good reason, pterosaurs don’t follow archosaur growth and ossification patterns.

“This discrepancy reveals developmental variation of Forfexopterus, but its relationship with sexual dimorphism needs to be certain by more available material.”

Pterosaurs have not yet shown sexual variation in their skeletons. Not yet.

The holotype Forfexopterus jeholensis
(Jiang et al. 2016; Early Cretaceous; Fig. 2) was originally considered an Archaeopterodactyloid. There is no such valid clade in the LPT. Here Forfexopterus nests with Ardeadactylus and Huanhepterus (Fig. 2) and other tall, slender pterosaurs basal to Azhdarchidae.


References
Jiang S, Cheng X, Ma Y and Wang X 2016. A new archaeopterodactyloid pterosaur from the Jiufotang Formation of western Liaoning, China, with a comparison of sterna in Pterodactylomorpha. Journal of Vertebrate Palaeontology: e1212058.
Zhou C-F, Wang J and Zhou Z 2020. A new wing skeleton of Forfexopterus (Pterosauria: Ctenochasmatidae) from the Early Cretaceous Jehol Biota reveals a developmental variation. Fossil Record 23:191–196,

wiki/Huanhepterus
wiki/Forfexopterus
wiki/Ardeadactylus
wiki/Beipiaopterus

 

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