''Microhadrosaurus'' (meaning "small sturdy lizard" in

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

) 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 n ...

hadrosaurid Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which incl ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the

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 ...

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interv ...

-age

Upper 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'', ...

Yuanpu Formation (also known as the

Nanxiong Formation The Nanxiong Formation (also known as Yuanpu Formation) is a Late Cretaceous geologic formation in Guangdong Province. Dinosaur remains are among the fossils that have been recovered from the formation. Description It consists of continental si ...

) of

Guangdong Guangdong (, ), alternatively romanized as Canton or Kwangtung, is a coastal province in South China on the north shore of the South China Sea. The capital of the province is Guangzhou. With a population of 126.01 million (as of 2020 ...

, China. Although its name identifies it as a small hadrosaur, it is based on juvenile remains, and the size of the adult hadrosaur is unknown.

Description

Dong Zhiming Dong Zhiming ( Chinese: 董枝明, Pinyin: ''Dǒng Zhimíng''; born January 1937) is a Chinese vertebrate paleontologist formerly employed at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing. He began working at th ...

named this genus for

IVPP The Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; ) of China is a research institution and collections repository for fossils, including many dinosaur and pterosaur specimens (many from the Yixian Formation). As its name sugges ...

V4732, a partial

lower jaw 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 ...

from a juvenile hadrosaur. This partial bone, with 18 columns of stacked

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, te ...

in a typical hadrosaur tooth battery, measures 37 centimeters long (15 inches). Dong later estimated the length of the individual at 2.6 meters (8.5 feet).

History

Dong regarded this genus as much like ''

Edmontosaurus ''Edmontosaurus'' ( ) (meaning "lizard from Edmonton") is a genus of hadrosaurid (duck-billed) dinosaur. It contains two known species: '' Edmontosaurus regalis'' and '' Edmontosaurus annectens''. Fossils of ''E. regalis'' have been found in ro ...

'', albeit in tiny form. However, Michael K. Brett-Surman, a hadrosaur specialist, regarded the material as showing no characteristics that would allow it to be differentiated from other duckbills. The most recent review accepts Brett-Surman's position, and regards ''Microhadrosaurus'' as a dubious name.

Paleobiology

As a hadrosaurid, ''Microhadrosaurus'' would have been a

bipedal Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...

quadruped Quadrupedalism is a form of locomotion where four limbs are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four limbs is said to be a quadruped (from Latin ''quattuo ...

herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthp ...

, eating

plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...

s with a sophisticated skull that permitted a grinding motion analogous to

chewing Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, ...

, and was furnished with hundreds of continually-replaced teeth. Because it is only known from a partial jaw from a juvenile, little more than general information can be drawn from it at this point.

Paleoecology

Fauna and habitat

The

consists of a 2000-meter sequence of red sandstones and clays which has yielded dinosaur fossils, dinosaur footprints and abundant egg shells. ''Microhadrosaurus'' shared its paleoenvironment with the

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their ...

'' Gannansaurus'', the therizinosauroid '' Nanshiungosaurus'', the

tyrannosaurid Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to thirteen genera, including the eponymous ''Tyrannosaurus''. The exact number of genera ...

'' Qianzhousaurus'' and the

oviraptorid Oviraptoridae is a group of bird-like, herbivorous and omnivorous maniraptoran dinosaurs. Oviraptorids are characterized by their toothless, parrot-like beaks and, in some cases, elaborate crests. They were generally small, measuring between on ...

s '' Banji'', ''

Jiangxisaurus ''Jiangxisaurus'' is an extinct genus of oviraptorid theropod dinosaur from the Late Cretaceous Nanxiong Formation of southern China. It was similar to '' Heyuannia'', but with more strongly curved anterior claws and a thinner, frailer mandib ...

'', ''

Corythoraptor ''Corythoraptor'' () is a genus of oviraptorid dinosaur from the late Maastrichtian Nanxiong Formation of South China. It contains one species, ''C. jacobsi'', known from a single well-preserved skeleton, and named after paleontologist Louis L ...

'', ''

Ganzhousaurus ''Ganzhousaurus'' (meaning "Ganzhou lizard") is an extinct genus of oviraptorid dinosaur known from the Late Cretaceous Nanxiong Formation of Nankang County, Ganzhou City of Jiangxi Province, southern China. It was found in a Maastrichtian dep ...

'', ''

Huanansaurus ''Huanansaurus'' is an extinct genus of oviraptorid dinosaur that lived approximately 72 million years ago, between the Campanian and Maastrichtian, during the latter part of the Cretaceous period in what is now China, in the Nanxiong Formation ...

'', ''

Nankangia ''Nankangia'' is an extinct genus of caenagnathoid oviraptorosaurian dinosaur known from the Upper 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 ...

'' and ''

Tongtianlong ''Tongtianlong'' (meaning "Tongtianyan dragon") is a genus of oviraptorid theropod dinosaurs that lived in the late Maastrichtian epoch of the late Cretaceous period. It contains one species, ''T. limosus''. Description ''Tongtianlong'' was ...

''.

References

{{Taxonbar, from=Q988563 Hadrosaurs Late Cretaceous dinosaurs of Asia Taxa named by Dong Zhiming Fossil taxa described in 1979 Ornithischian genera

Description

History

Paleobiology

Paleoecology

Fauna and habitat

See also

References