Restudy of Haopterus fails to identify it as an adult ornithocheirid

Xu, Jiang and Wang 2025 wrote,
“The referral of Haopterus gracilis has been a subject of debate since its discovery. Various phylogenetic analyses have suggested different positions for Haopterus gracilis, including the sister taxon of the Ornithocheiroidea or placed differently in the Pteranodontoidea.”

Haopterus has teeth surrounding its jaw lines (Fig 1). So do all members of the Ornthocheiridae. By direct contrast, all members of Pteranodontidae (= Nyctosaurus + Pteranodon) are toothless.

Case closed? Not for pterosaur experts since 2003. No one can explain this anomaly.

Figure 6. Haopterus is close to Mimodactylus and provides a bauplan for a bipedal stance. Note the tiny feet and palate morphology. ” data-image-caption=”

Figure 6. Haopterus is close to Mimodactylus and provides a bauplan for a bipedal stance. Note the tiny feet and palate morphology.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/08/haopterus588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/08/haopterus588.jpg?w=584″ class=”size-full wp-image-1459″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/08/haopterus588.jpg” alt=”Figure 6. Haopterus is close to Mimodactylus and provides a bauplan for a bipedal stance. Note the tiny feet and palate morphology.” width=”584″ height=”380″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/08/haopterus588.jpg?w=584&h=380 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/08/haopterus588.jpg?w=150&h=98 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/08/haopterus588.jpg?w=300&h=195 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/08/haopterus588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Haopterus is close to Mimodactylus and provides a bauplan for a bipedal stance. Note the tiny feet and palate morphology.

Xu, Jiang and Wang 2025 wrote,
“Recent research has proposed that Haopterus gracilis is the sister-taxon of the Lebanese istiodactyliform Mimodactylus libanensis.”

The large pterosaur tree (LPT, 264 taxa, subset Fig 3) confirms this pairing (Fig 2).

“Here we redescribe the holotype and only specimen of Haopterus gracilis, a relatively complete skeleton of a juvenile individual in detail using Micro-CL scanning.”

Juvenile? Not in the LPT (subset Fig 3), where Mimodactylus and Haopterus are small basal ornithocheirids. Derived clade members get bigger.

Figure 2. The origin of Ornithocheiridae in the LPT includes small Mimodactylus and Haopterus all derived from tiny scaphognathids. ” data-image-caption=”

Figure 2. The origin of Ornithocheiridae in the LPT includes small Mimodactylus and Haopterus all derived from tiny scaphognathids.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/mimodactylus-haopterus588.jpg?w=111″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/mimodactylus-haopterus588.jpg?w=380″ class=”size-full wp-image-92220″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/mimodactylus-haopterus588.jpg” alt=”Figure 2. The origin of Ornithocheiridae in the LPT includes small Mimodactylus and Haopterus all derived from tiny scaphognathids.” width=”584″ height=”1573″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/mimodactylus-haopterus588.jpg?w=584&h=1573 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/mimodactylus-haopterus588.jpg?w=56&h=150 56w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/mimodactylus-haopterus588.jpg?w=111&h=300 111w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/mimodactylus-haopterus588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2. The origin of Ornithocheiridae in the LPT includes small Mimodactylus and Haopterus all derived from tiny scaphognathids.

The authors report,
“Lots of evidence indicates the holotype of Haopterus a juvenile individual, including several bones remaining unfused,”

The authors list no other evidence other than lack of fusion at various joints. They don’t understand the phylogeny and ontogeny of pterosaurs in which lack of fusion is a phylogenetic trait. Some tiny adult pterosaurs have fused joints. This growth strategy arises with neotony = precocial sexual maturity = cessation of growth at smaller sizes (Peters 2007).

In the LPT pterosaur clades (e.g. Fig 3) all start small and evolve larger members. All major clades had their origins in neotony = sexual maturity at smaller sizes = phylogenetic miniaturization (Fig 2). Pterodaustro studies showed sexual maturity occurring at half maximum size (Chinsamy, Codorniú and Chiappe 2008.). A series of such precocial parents results in much smaller progeny, which is what we see as transitional taxa between all major clades.

When academics refuse to include tiny taxa, imagining them to be allometric juvenile archosaurs, those academics hobble their own phylogenetic studies.

When independent researchers include tiny taxa (and all well-preserved larger taxa), those amateurs make discoveries like this (Fig 2).

Taxon exclusion is the number one problem in paleontology.
Don’t exclude the little ones.

“The new analysis revealed Haopterus in the Pteranodontoidea and, within this clade, it was an istiodactyliform.”

The LPT does not confirm this nesting. In the LPT (subset Fig 3), istiodactylids are also members of the Ornithocheiridae, all derived from little Late Jurassic scaphognathids. Cycnorhampids are sister taxa. Toothless pteranodontids are not related to toothed ornithocheirids. They arose from germanodactylids that lose their teeth at the transition.

Figure 3. Subset of the LPT focusing on Haopterus, a basal ornithocheirid. ” data-image-caption=”

Figure 3. Subset of the LPT focusing on Haopterus, a basal ornithocheirid.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/ornithocheiridae2025.jpg?w=196″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/ornithocheiridae2025.jpg?w=584″ class=”size-full wp-image-92222″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/ornithocheiridae2025.jpg” alt=”Figure 3. Subset of the LPT focusing on Haopterus, a basal ornithocheirid.” width=”584″ height=”894″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/ornithocheiridae2025.jpg?w=584&h=894 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/ornithocheiridae2025.jpg?w=98&h=150 98w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/ornithocheiridae2025.jpg?w=196&h=300 196w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/04/ornithocheiridae2025.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 3. Subset of the LPT focusing on Haopterus, a basal ornithocheirid.

The ‘Kryptodrakon’ problem reappears here.
The authors outgroup taxon ‘Kryptodrakon‘ is based on pieces of the dorygnathid Sericipterus from the same locality assembled to resemble a pterodactylid in an example of wish fulfillment = everyone wants to make a major discovery. Sometimes mistakes happen. Details here:

New basal pterodactyloid(?) Kryptodrakon = Sericipterus, a dorygnathid

References
Chinsamy A, Codorniú L and Chiappe LM 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters, 4: 282-285.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Xu Y, Jiang S and Wang X 2024. The restudy of Haopterus gracilis from the Yixian Formation, Liaoning, China. Cretaceous Research 162(2024) 105933
Wang X and Lü J 2001. Discovery of a pterodactylid pterosaur from the Yixian Formation of western Liaoning, China. Chinese Science Bulletin 46(13):1-6.

wiki/Haopterus