AMNH 4908: at the genesis of Nyctosaurus and Pteranodon

Bennett 2017 described AMNH 4908:
“The smallest relatively complete previously known specimen of Pteranodon, AMNH 4908, consists of a partial trunk skeleton and tail, scapulocoracoid, humerus through WP2, both femora and tibiae, and a disarticulated foot (Bennett, 2001; Table 1), had an estimated wingspan in life of 3.33 m.”

AMNH 4908 is small because
it is primitive (Figs. 1–3), closer to its smaller germanodactylid ancestors (Fig. 4), not because it is ontogenetically young. That point was overlooked by Bennett 2017 who decided not to include a comprehensive phylogenetic analysis then or earlier (Bennett 1991, 1992). He thought smaller specimens, like AMNH 4908, were female.

Figure 1. The Niobrara specimen AMNH4908 in situ.

Figure 1. The Niobrara specimen AMNH4908 in situ. See figure 3 for reconstruction.

It is worth noting
AMNH 4908 has a type of pelvis with unfused ischia, a morphology common to Nyctosaurus. Earlier Bennett 1991, 1992 decided a large Nyctosaurus pelvis belonged to a female Pteranodon, which started that gender myth. Unfortunately, Bennett never used phylogenetic analysis to lump and split Pteranodon, the subject of his 1991 PhD thesis. Instead he relied on a statistical analysis, which led him astray. The large pterosaur tree (LPT, 246 taxa) is the only published pterosaur cladogram to include more than one or two Pteranodon and Nyctosaurus taxa. When you really want to know something in systermatics, use a comprehensive cladogram, not a graph.

Figure 2. Subset of the LPT focusing on pterandontids and their ancestors going back to Late Jurassic germanodactylids. AMNH 4908 nests between the Nyctosaurus clade and the Pteranodon clade.

Figure 2. Subset of the LPT focusing on pterandontids and their ancestors going back to Late Jurassic germanodactylids. AMNH 4908 nests between the Nyctosaurus clade and the Pteranodon clade.

Also worth noting
is the deltopectoral crest of the humerus in AMNH 4908, which has a round tongue shape like that of its predecessors among Eopteranodon and Germanodactylus (Fig. 4), rather than the hatchet shape found in Nyctosaurus or the warp found in Pteranodon.

Figure 3. AMNH 4908 pterosaur reconstructed. Transitional between Nyctosaurus and Pteranodon. Note the big feet, tiny sternal complex and round tip deltopectoral crest. Note the massive radius + ulna.

Figure 3. AMNH 4908 pterosaur reconstructed. Transitional between Nyctosaurus and Pteranodon. Note the big feet, tiny sternal complex and round tip deltopectoral crest. Note the massive radius + ulna.

Of course, any taxon basal to Nyctosaurus and Pteranodon
is also going to be close to the SMNK PAL 6592 specimen (Fig. 4) attributed to Germanodactylus.

Matching YPM 1179 to the post-crania of SMU 76476 (Myers 2010) and overprinted with SMNK PAL 6592. The resemblance is indeed remarkable.

Figure 4. Matching YPM 1179 to the post-crania of SMU 76476 (Myers 2010) and overprinted with SMNK PAL 6592. The resemblance is indeed remarkable.

Ever since 2003, traditional pterosaur workers (with PhDs)
have been linking toothless pteranodontids to toothy ornithocheirids. That they continue to do so, (due to taxon exclusion) is embarrassing to the profession.

Figure 2. The Tanking-Davis specimen compared to other forms. Specimen w and specimen z appear to be the closest to the Tanking-David specimen. Specimen 'w' = Pteranodon sternbergi? USNM 12167 (undescribed). Specimen 'z' = Pteranodon longiceps? Dawndraco? UALVP 24238. Click to enlarge.

Figure 5. Pteranodon and Nyctosaurus skulls. Click to enlarge.

Figure 6. AMNH 4908 specimen compared to a large Pteranodon specimen UNSM 50036.

Figure 6. AMNH 4908 specimen compared to a large Pteranodon specimen UNSM 50036.

In similar fashion and shame,
traditional paleontologists continue to insist that pterosaurs arose from Euparkeria, Scleromochlus or Erythrosuchus according to several authors, or from Macrocnemus bassaniiPostosuchus kirkpatricki and Herrerasaurus ischigualastensis according to Dalla Vecchia 2019. More closely related taxa (LangobardisaurusCosesaurus, Sharovipteryx and Longisquama) were validated as better pterosaur ancestors in four phylogenetic analyses 20 years ago.


References
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 2017. New smallest specimen of the pterosaur Pteranodon and ontogenetic niches in pterosaurs. Journal of Paleontology. pp.1-18. 0022-3360/15/0088-0906
doi: 10.1017/jpa.2017.84
Dalla Vecchia FM 2019. Seazzadactylus venieri gen. et sp. nov., a new pterosaur (Diapsida: Pterosauria) from the Upper Triassic (Norian) of northeastern Italy. PeerJ 7:e7363 DOI 10.7717/peerj.7363

Thanks to Alex Schiller for posting this specimen on Facebook.

https://pterosaurheresies.wordpress.com/2012/04/09/female-pterosaurs/

http://www.reptileevolution.com/pteranodon-postcrania.htm

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