''Montanazhdarcho'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

azhdarchoid Azhdarchoidea (or azhdarchoids) is a group of pterosaurs within the suborder Pterodactyloidea, more specifically within the group Ornithocheiroidea. Pterosaurs belonging to this group lived throughout the Early and Late Cretaceous periods, with o ...

pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 ...

from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

period (

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

stage) of what is now the state of

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

. ''Montanazhdarcho'' is known from only one species, ''M. minor''.

Discovery

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

specimen, MOR 691 ( Museum of the Rockies), was found by Robert W. Harmon in Glacier County, in the territory of the Blackfoot, in sandstone of the Upper

Two Medicine Formation The Two Medicine Formation is a geological formation, or rock body, in northwestern Montana and southern Alberta that was deposited between and (million years ago), during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky M ...

, a layer about 74 million years old. The genus name ''Montanazhdarcho'' was first given informally in 1993 by

Kevin Padian Kevin Padian (born 1951) is a Professor of Integrative Biology at the University of California, Berkeley, Curator of Paleontology, University of California Museum of Paleontology and was President of the National Center for Science Education fro ...

, Armand de Ricqlès, and Jack Horner. It was then named formally in 1995 by the same researchers, and was fully described in 2002. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

is ''Montanazhdarcho minor''. The generic name refers to the state of

and to the related species ''

Azhdarcho ''Azhdarcho'' is a genus of azhdarchid pterosaur from the late Cretaceous Period of the Bissekty Formation (middle Turonian stage, about 92 million years ago) of Uzbekistan, as well as the Zhirkindek Formation of Kazakhstan. It is known from ...

''. The specific name means "the smaller one" in

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

, a reference to the relatively small size in comparison to closely related forms.

Description

''Montanazhdarcho'' was a relatively small pterosaur, reaching in wingspan. 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 A symphysis (, pl. symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing togethe ...

of the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

. The jaws were edentulous, i.e. they lacked teeth.

Classification

Significant pterosaur discoveries in western North America

''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 In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

, and

carpal The carpal bones are the eight small bones that make up the wrist (or carpus) that connects the hand to the forearm. The term "carpus" is derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In human anatomy, the ...

suggest an animal with a wingspan. Its

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

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. However, in 2018, Nicholas Longrich and colleagues had recovered ''Montanazhdarcho'' within the Azhdarchidae again, though placed in the basalmost position. Their phylogenetic analysis is shown below:

References

{{Portal bar, Paleontology, Cretaceous, United States Late Cretaceous pterosaurs of North America Azhdarchoids Fossil taxa described in 1995 Taxa named by Kevin Padian Taxa named by Armand de Ricqlès Taxa named by Jack Horner

Discovery

Description

Classification

See also

References