Montanazhdarcho

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Montanazhdarcho
Temporal range: Late Cretaceous, 74 Ma
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Montanazdarco.jpg
Reconstructed skeletons
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Order: †Pterosauria
Suborder: †Pterodactyloidea
Clade: †Azhdarchoidea
Genus: †Montanazhdarcho
Padian, de Ricqlès & Horner, 1995
Type species
†Montanazhdarcho minor
Padian, Ricqlès & Horner, 1995

Montanazhdarcho is a genus of azhdarchoid pterosaur from the Late Cretaceous period (Campanian stage) of what is now the state of Montana, United States. Montanazhdarcho is known from only one species, M. minor.

History and etymology[]

The genus was named in 1993 by Kevin Padian, Armand de Ricqlès, and Jack Horner,[1] again published by the same authors in 1995[2] and fully described in 2002.[3]

Map showing global distribution of faunas containing small-medium and giant-sized azhdarchids

The type species is Montanazhdarcho minor. The generic name refers to the state of Montana and to the related species Azhdarcho. The specific name means "the smaller one" in Latin, a reference to the relatively small size in comparison to closely related forms.

Description[]

The holotype specimen of Montanazhdarcho, MOR 691 (Museum of the Rockies), was found by in Glacier County, in the territory of the Blackfoot, in sandstone of the Upper Two Medicine Formation, a layer about 74 million years old. The fossil is largely uncompressed and that of an adult exemplar, as established by a study of the bone by de Ricqlès. It consists of a partial left wing, lacking the outer three wing finger phalanges, a complete shoulder girdle, a crushed cervical vertebra and two fragments of the symphysis of the mandible. The jaws were edentulous, i.e. they lacked teeth.

Classification[]

Location of the discovery of Montanazhdarcho (top; USA)

Montanazhdarcho was by the authors assigned to the Azhdarchidae, mainly based on the elongated form of the neck vertebra. Compared to other azhdarchids however, it was small; the fragments of humerus, radius, and carpal suggest an animal with a 2.5 meter wingspan (8 ft). Its ulna was longer than the wing metacarpal, which is atypical for azhdarchids. In addition to this, a phylogenetic study in 2015 has disagreed to its phylogenetic position, and reassigned Montanazhdarcho as a non-azhdarchid azhdarchoid.[4] However, in 2018, Nicholas Longrich and colleagues had recovered Montanazhdarcho within the Azhdarchidae again, though placed in the basalmost position.[5] Their phylogenetic analysis is shown below:

Azhdarchidae
 

Montanazhdarcho

 
 
 

Azhdarcho

 
 
 
 

Phosphatodraco

 
 

Aralazhdarcho

 
 
 
 

Eurazhdarcho

 
 
 

aff. Quetzalcoatlus

 
 
 

Zhejiangopterus

 
 
 

Arambourgiania

 
 

Hatzegopteryx

 
 

Quetzalcoatlus

 
 
 
 
 
 
 
 

See also[]

References[]

  1. ^ Padian, K., Horner, J.R., and de Ricqlès, A.J. (1993). "A new azhdarchid pterosaur from the Two Medicine Formation (Late Cretaceous, Campanian) of Montana, identified on the basis of bone histology." Journal of Vertebrate Paleontology, 13: 52A
  2. ^ K. Padian, A. J. de Ricqlès, and J. R. Horner (1995), "Bone histology determines identification of a new fossil taxon of pterosaur (Reptilia: Archosauria)", Comptes Rendus de l’Academie des Science, Serie II (320): 77-84
  3. ^ McGowen, M.R.; Padian, K.; de Sosa, M.A.; Harmon, R.J. (2002). "Description of Montanazhdarcho minor, an azhdarchid pterosaur from the Two Medicine Formation (Campanian) of Montana". PaleoBios. 22 (1): 1–9.
  4. ^ Carroll, Nathan (2015). "Reassignment of Montanazhdarcho minor as a non-azhdarchid member of the Azhdarchoidea". Journal of Vertebrate Paleontology. 35: 104.
  5. ^ Longrich, Nicholas R.; Martill, David M.; Andres, Brian; Penny, David (2018). "Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary". PLOS Biology. 16 (3): e2001663. doi:10.1371/journal.pbio.2001663. PMC 5849296. PMID 29534059.
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