Gryposaurus

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Not to be confused with Gyposaurus.

Gryposaurus
Temporal range:
Ma
↓
G. monumentensis skeleton in the Natural History Museum of Utah
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: †Ornithischia
Clade: †Ornithopoda
Family: †Hadrosauridae
Subfamily: †Saurolophinae
Tribe: †Kritosaurini
Genus: †Gryposaurus
Type species
†Gryposaurus notabilis
Lambe, 1914
Species
  • †G. notabilis
    Lambe, 1914
  • †G. latidens
    Horner, 1992
  • †G. monumentensis
    Sampson
    , 2007
  • †G. alsatei?
    Lehman, Wick, Wagner, 2016
Synonyms

Gryposaurus (meaning "hooked-nosed (

stages) of North America. Named species of Gryposaurus are known from the Dinosaur Park Formation in Alberta, Canada, and two formations in the United States: the Lower Two Medicine Formation in Montana and the Kaiparowits Formation of Utah. A possible additional species from the Javelina Formation
in Texas may extend the temporal range of the genus to 66 million years ago.

Gryposaurus is similar to

quadrupedal herbivore around 8 meters (26 feet) long, it may have preferred river
settings.

History of discovery

G. notabilis (formerly G. incurvimanus), collected 1918

Gryposaurus is

Lull and Wright monograph on hadrosaurs sealed the Kritosaurus/Gryposaurus question for nearly fifty years in favor of Kritosaurus. Reviews beginning in the 1990s, however, called into question the identity of Kritosaurus navajovius, which has limited material for comparison with other duckbills.[9]
Thus, Gryposaurus has once again been separated, at least temporarily, from Kritosaurus.

Skull, Royal Tyrrell Museum

This situation is made more confusing by old suggestions by some authors, including Jack Horner, that

Bearpaw Shale of Montana[10] (which have since fallen out of the literature), by 1990 he had changed his position, and was among the first to again use Gryposaurus in print.[9] Current thought is that Hadrosaurus, although known from fragmentary material, can be distinguished from Gryposaurus by differences in the upper arm and ilium.[14]

Further research has revealed the presence of a second species, G. latidens, from slightly older rocks in Montana than the classic gryposaur localities of Alberta. Based on two parts of a skeleton collected in 1916 for the

derived species.[16]

New material from the

predentary had enlarged prongs along its upper margin, where the lower jaw's beak was based. This new species greatly expands the geographic range of this genus, and there may be a second, more lightly built species present as well.[17] Multiple gryposaur species are known from the Kaiparowits Formation, represented by cranial and postcranial remains, and were larger than their northern counterparts.[18]

In Texas, specifically at the Javelina Formation and the El Picacho Formation, indeterminate hadrosaur remains resembling Kritosaurus and Gryposaurus have been unearthed for decades, but none were considered to be identifiable as a determined genus of hadrosaur, but do resemble some species of Kritosaurini or at least some species of Kritosaurus.[19] However, in 2016, a possibly forth valid species of Gryposaurus named G. alsatei, which was named after Alsate, who was the last leader of the Mescalero Apaches, was unearthed in the Javelina Formation in Texas. Further research is needed to confirm its validity.[20][21][22]

Species

G. monumentensis skull

As of 2016, there are currently three named species that are recognized as valid today: G. notabilis, G. latidens, and G. monumentensis.

saurolophine which closely resembles Saurolophus, but with a more solid crest.[29]

The dubious hadrosaurid Stephanosaurus marginatus[30] was considered a possible species of Kritosaurus, following the synonymy of Gryposaurus with Kritosaurus.[31][32][2] However, this synonymy was rejected in the 2004 edition of the Dinosauria, with Stephanosaurus being tabulated as dubious.[24]

Description

life restoration

Gryposaurus was a hadrosaurid of typical size and shape; one of the best specimens of this genus, the nearly complete

type specimen of Kritosaurus incurvimanus (now regarded as a synonym of Gryposaurus notabilis) came from an animal about 8.2 meters (27 feet) long.[33] This specimen also has the best example of skin impressions for Gryposaurus, showing this dinosaur to have had several different types of scalation: pyramidal, ridged, limpet-shaped scutes upwards of 3.8 centimeters long (1.5 inches) on the flank and tail; uniform polygonal scales on the neck and sides of the body; and pyramidal structures, flattened side-to-side, with fluted sides, longer than tall and found along the top of the back in a single midline row.[34] In 2016, Gregory S. Paul estimated the size of G. latidens at 7.5 metres (25 ft) in length and 2.5 metric tons (2.8 short tons) in body mass and the other two species (G. notabilis and G. monumentensis) at 8 metres (26 ft) in length and 3 metric tons (3.3 short tons) in body mass.[35]

The three named species of Gryposaurus differ in details of the skull and lower jaw.[2] The prominent nasal arch found in this genus is formed from the paired nasal bones. In profile view, they rise into a rounded hump in front of the eyes, reaching a height as tall as the highest point of the back of the skull.[3] The skeleton is known in great detail,[36] making it a useful point of reference for other duckbill skeletons.

Classification

Size comparison of three species of Gryposaurus.
G. alstasei restoration

Gryposaurus was a saurolophine (hadrosaurine of older references) hadrosaurid, a member of the duckbill subfamily without hollow head crests.[24] The general term "gryposaur" is sometimes used for duckbills with arched nasals.[9] Tethyshadros was once thought to fall into this group as well, before it was described (then known under the nickname "Antonio").[37] A subfamily, Gryposaurinae, was coined by Jack Horner as part of a larger revision that promoted Hadrosaurinae to family status,[16] but is not now in use. A rough equivalent is Kritosaurini, as used by Alberto Prieto-Márquez.[38] Kritosaurus has been proposed to be a synonym of Gryposaurus, but it is slightly younger. Additionally, while the skull of Kritosaurus is incompletely known, lacking most of the bones in front of the eyes, it was very similar to that of Gryposaurus.[5]

The following is a cladogram based on the phylogenetic analysis conducted by Prieto-Márquez and Wagner in 2012, showing the relationships of Gryposaurus among the other kritosaurins:[38]

 Kritosaurini

Wulagasaurus

Kritosaurus

Gryposaurus latidens

Gryposaurus notabilis

Gryposaurus monumentensis

Paleobiology

Restored head of G. notabilis.

As a

dental batteries that contained hundreds of teeth, only a relative handful of which were in use at any time. Plant material would have been cropped by its broad beak, and held in the jaws by a cheek-like organ. Its feeding range would have extended from the ground to about 4 m (13 ft) above.[24] The paleontologists who unearthed G. monumentensis back in the 2000s brought the fact that this creature dined on tough, fibrous plant material which would imply that Gryposaurs was both a grazer and a browser.[39][40][41][42][43]

Like other bird-hipped dinosaurs of the Dinosaur Park Formation, Gryposaurus appears to have only existed for part of the duration of time that the rocks were being formed. As the formation was being laid down, it recorded a change to more marine-influenced conditions. Gryposaurus is absent from the upper part of the formation, with Prosaurolophus present instead. Other dinosaurs known from only the lower part of the formation include the horned Centrosaurus and the hollow-crested duckbill Corythosaurus.[25] Gryposaurus may have preferred river-related settings.[24]

Nasal arch

The distinctive nasal arch of Gryposaurus, like other cranial modifications in duckbills, may have been used for a variety of social functions, such as identification of sexes or species and social ranking.[24] It could also have functioned as a tool for broadside pushing or butting in social contests, and there may have been inflatable air sacs flanking it for both visual and auditory signaling.[44] The top of the arch is roughened in some specimens, suggesting that it was covered by thick, keratinized skin,[44] or that there was a cartilaginous extension.[16]

Paleoecology

Restoration of G. monumentensis (left background) and other animals of the Kaiparowits Formation

Utah

Argon-argon radiometric dating indicates that the Kaiparowits Formation was deposited between 76.1 and 74.0 million years ago, during the Campanian stage of the Late Cretaceous period.[45][46] During the Late Cretaceous period, the site of the Kaiparowits Formation was located near the western shore of the Western Interior Seaway, a large inland sea that split North America into two landmasses, Laramidia to the west and Appalachia to the east. The plateau where dinosaurs lived was an ancient floodplain dominated by large channels and abundant wetland peat swamps, ponds and lakes, and was bordered by highlands. The climate was wet and humid, and supported an abundant and diverse range of organisms.[47] This formation contains one of the best and most continuous records of Late Cretaceous terrestrial life in the world.[48]

Gryposaurus monumentensis shared its

multituberculates, marsupials, and insectivorans.[50]

See also

References

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