New species of stegosaur is oldest discovered in Asia, and possibly the
world
Bashanosaurus primitivus roamed Earth around 168 million years ago during
the Middle Jurassic period

Date:
March 3, 2022
Source:
Taylor & Francis Group
Summary:
Relatively small, but fearsome-looking stegosaur measured about
2.8 meters (9 feet) from nose to tail -- but scientists can't tell
whether the remains are those of an adult or juvenile.



FULL STORY ========================================================================== Relatively small, but fearsome-looking stegosaur measured about 2.8
metres (9 feet) from nose to tail -- but scientists can't tell whether
the remains are those of an adult or juvenile.


==========================================================================
A new species of one of the most recognisable types of dinosaur is the
oldest stegosaur ever found in Asia, and one of the earliest unearthed
anywhere in the world, according to research published today in the peer-reviewed Journal of Vertebrate Paleontology.

Remains of the stegosaur, which included bones from the back, shoulder,
thigh, feet, and ribs, as well as several armour plates, date to the
Bajocian stage of the Middle Jurassic period -- much earlier than most
known stegosaurs.

A team from the Chongqing Bureau of Geological and Mineral Resource
Exploration and Development in China and London's Natural History Museum
named it Bashanosaurus primitivus- "Bashan" in reference to the ancient
name for the area of Chongqing in China where the dinosaur was found,
and the Latin for 'first' -- primitivus.

The new dinosaur, which roamed the planet 168 million years ago, plays a
part in uncovering how the stegosaurs evolved -- of which, to this day,
little is known.

It has a smaller and less developed should blade, narrower and thicker
bases to its armour plates and other features that are different from
all other Middle Jurassic stegosaurs discovered so far. However, it does
have similarities with some of the first armoured dinosaurs, which are
over 20 million years older.



==========================================================================
"All these features are clues to the stegosaurs' place on the
dinosaur family tree," says Dr Dai Hui from Chongqing Bureau of
Geological and Mineral Resource Exploration and Development who led the research. "Bashanosauruscan be distinguished fromother Middle Jurassic stegosaurs, and clearly represents a new species.

"What's more, our analysis of the family tree indicates that it is one
of the earliest-diverging stegosaurs along with the Chongqing Lizard (Chungkingosaurus) and Huayangosaurus. These were all unearthed from
the Middle to Late Jurassic Shaximiao Formation in China, suggesting
that stegosaurs might have originated in Asia," adds Hui.

Instantly recognisable by the huge back plates, long tail spikes and tiny
head, stegosaurs were four-legged, plant-eating dinosaurs that lived
during the Jurassic and early Cretaceous periods. Stegosaur fossils
have been found on all continents except for Antarctica and Australia,
and 14 species of stegosaur have been identified so far.

Well-known members of Stegosauria include Huayangosaurus (one of the
most primitive stegosaurs), Gigantspinosaurus, notable for its enormous shoulder spines, and Miragaia for its extremely long neck. However,
the fragmentary fossil material has hindered attempts to understand how
the stegosaurs evolved and how they relate to one another.

With the discovery of this new species the mystery has started to
clear up.

Bashanosaurus primitivus has several primitive features that are similar
to the earliest stegosaurs like Huayangosaurus and Gigantspinosaurus
and early- branching thyreophorans (armoured dinosaurs). These include
longer tail vertebrae, a shoulder blade that is narrower and flares out,
and features of the back vertebrae that are similar to the early armoured dinosaur Scelidosaurus,which lived during the Early Jurassic.

The fossilised remains of Bashanosaurus also reveal a host of features
that make it unique from other known stegosaurs. For example, the bony
point at the end of the shoulder blade is small and less well developed
than in other stegosaurs; a bony projection of the thighbone (fourth trochanter) is positioned below the middle of the shaft; and the bases
of the armour plates curve outwards and are thicker than the plates on
the backs of its later relatives.

"The discovery of this stegosaur from the Middle Jurassic of China adds
to an increasing body of evidence that the group evolved in the early
Middle Jurassic, or perhaps even in the Early Jurassic, and as such
represent some of the earliest known bird-hipped dinosaurs," says Dr
Susannah Maidment, co-author and palaeontologist at London's Natural
History Museum.

"China seems to have been a hotspot for stegosaur diversity,
with numerous species now known from the Middle Jurassic right
the way through until the end of the Early Cretaceous period." ========================================================================== Story Source: Materials provided by Taylor_&_Francis_Group. Note:
Content may be edited for style and length.


========================================================================== Related Multimedia:
* Artist's_impression_of_Bashanosaurus_primitivus ========================================================================== Journal Reference:
1. Dai Hui, Li Ning, Susannah C. R. Maidment, Wei Guangbiao, Zhou
Yuxuan, Hu
Xufeng, Ma Qingyu, Wang Xunqian, Hu Haiqian, Peng Guangzhao. New
Stegosaurs from the Middle Jurassic Lower Member of the Shaximiao
Formation of Chongqing, China. Journal of Vertebrate Paleontology,
2022; DOI: 10.1080/02724634.2021.1995737 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220303215823.htm

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