Vestigial fingers on the UNSM 93000 Nyctosaurus

The UNSM 93000 specimen attributed to Nyctosaurus
has only three wing phalanges and the tiny vestigial free fingers have never been looked at using DGS methods before. Well, here they are (Fig. 1).

Figure 1. Closeup of the UNSM 93000 specimen of Nyctosaurus focusing on three vestige free fingers.

Figure 1. Closeup of the UNSM 93000 specimen of Nyctosaurus focusing on three vestige free fingers. This is what happens when you no longer need these fingers. You can tell Nyctosaurus from Pteranodon in that the former never fuses the sesamoid (extensor tendon process) to phalanx 4.1. Other wrongly consider this a trait of immaturity.

Nyctosaurus sp. UNSM 93000 (Brown 1978, 1986) was derived from a sister to Nyctosaurus gracilis and phylogenetically preceded the crested Nyctosaurus specimens. Except for the rostral tip, the skull and cervicals are missing. Distinct from Nyctosaurus gracilis, the dorsals of the Nebraska specimen relatively shorter. The scapula and coracoid were more robust. The deltopectoral crest of the humerus most closely resembled that of Muzquizopteryx. Fingers I-III were tiny vestiges. Manual 4.1 extended to mid ulna when folded. Manual 4.4 was probably fused to m4.3 or it was missing and m4.3 became curved.

Figure 1. The UNSM specimen of Nyctosaurus, the only one for which we are sure it had only three wing phalanges.

Figure 2. The UNSM specimen of Nyctosaurus, the only one for which we are sure it had only three wing phalanges.

The pubis and ischium did not touch, as in more primitive nyctosaurs. It would have been impossible for the forelimb to develop thrust during terrestrial locomotion. It was likely elevated or used like a ski-pole.


The family tree of the Ornithocephalia and Germanodactylia is here. The expanded family tree of the Pterosauria is here.


References
Brown GW 1978. Preliminary report on an articulated specimen of Pteranodon Nyctosaurusgracilis. Proceedings of the Nebraska Academy of Science 88: 39.
Brown GW 1986. Reassessment of Nyctosaurus: new wings for an old pterosaur. Proceedings of the Nebraska Academy of Science 96: 47.

 

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