Muzquizopteryx: a small nyctosaurid from Mexico

Muzquizopteryx coahuilensis is a small nyctosaurid pterosaur from laminated limestones of Coahuila, north-eastern Mexico. Its type, UNAM IGM 8621, is an articulated skeleton with preserved soft-tissue traces and an estimated wingspan of about two metres. A separate partial wing from younger Late Turonian beds resembles the type but lacks enough diagnostic features for a species-level identification; researchers referred to it as cf. Muzquizopteryx. The pterosaur catalogue keeps the named species distinct from this tentative second record.

Quick facts

The type from El Rosario

Eberhard Frey and colleagues described Muzquizopteryx coahuilensis in 2006 from the El Rosario quarry area of Coahuila, north-eastern Mexico. Holotype UNAM IGM 8621 is a small, nearly complete, articulated nyctosaurid skeleton preserved on a slab and counterslab. The paper assigned it to the Lower Coniacian and estimated an adult wingspan of about two metres.

The limestone preserves more than bone outlines. Mineralised tendons remain close to the wing elements, and the wrist bones retain a useful in-place arrangement. Those details allowed the authors to discuss the position of the pteroid and reconstruct aspects of the wing’s supporting anatomy. They do not preserve every muscle or show the exact range of motion in life.

Small size and skeletal maturity

The type’s modest span does not indicate that it was a juvenile. The original authors interpreted UNAM IGM 8621 as an adult and considered it the smallest known adult nyctosaurid at the time. The approximately two-metre wingspan was calculated from the preserved arm and wing proportions, rather than measured across an intact outstretched wing.

Nyctosaurids are toothless pterodactyloids. Their wing and shoulder anatomy helps distinguish them from other flying reptiles, while debates over their higher-level relationships have continued. The family assignment of Muzquizopteryx is based on a combination of anatomical features, not on size alone.

A second wing, a more cautious name

Frey and colleagues later described a separate partial right wing from the Múzquiz quarry region. It includes the humerus, radius and ulna, carpus, wing-finger metacarpal and part of the first wing-finger phalanx. The host deposits were dated to the Late Turonian. Its humerus resembles that of M. coahuilensis, but the specimen lacks diagnostic features that would establish the same species. The authors therefore used cf. Muzquizopteryx rather than assigning it outright.

This referred wing should not be combined with the articulated type to create a single larger skeleton or a growth series. It is a separate animal from a different horizon, and its identification remains tentative. The Late Turonian age was presented as an early record for nyctosaurids in that study, while the type species itself is Lower Coniacian.

What the fossils leave open

The preserved tendons, wrist and wing bones provide unusually direct evidence about anatomy. A marine limestone setting makes flight over water plausible, but no stomach contents show a precise diet, and the fossil does not document a particular foraging manoeuvre. The safest picture is a small adult nyctosaurid with an approximately two-metre estimated span, accompanied in the broader regional record by a distinct, tentatively assigned wing.