Liaoningosaurus
Encyclopedia
Liaoningosaurus is a very unusual ankylosaur from the Lower Cretaceous
. The holotype
IVPP
V12560 (Institute of Vertebrate
Paleontology
and Paleoanthropology
, Beijing
), an essentially complete juvenile skeleton
compressed on a slab, was collected from the Yixian Formation
(Aptian
stage) of Liaoxi, Yixian County, Liaoning
Province, People's Republic of China
.
The type species
Liaoningosaurus paradoxus was named by Xu Xing, Wang Xiaolin and You Hailu in 2001. The generic name refers to Liaoning. The specific name refers to the confusing mix of nodosaurid and ankylosaurid features shown by the specimen.
The articulated skeleton measures approximately 34 cm in length, giving it the distinction of being the smallest-known ankylosaur specimen. The specimen is unique among all known ankylosaur fossils in the retention of the external mandibular fenestra. Antorbital fenestra
e may also be present. Both are likely juvenile traits, just as the relatively large teeth, the retention of teeth in the praemaxilla, long feet, long lower legs and the possession of long sharp claws on the hand and feet. A real feature unique to the taxon
, or autapomorphy
might be the trapezoid
form of the breast bone
Another new feature is the presence of ventral armor plating, two very large paired osteoderms covering the entire abdomen and having a surface structure sculpted with small hexagonal and rhombic elevations. Such plates had never been found with other ankylosaurians, of which the belly armor is poorly known, however. Smaller triangular osteoderms were found on the shoulder, the scapula showing the onset of a shoulder spike.
Determining the relations of Liaoningosaurus is difficult because of the young age of the individual specimen and the presence of traits both typical of ankylosaurids and nodosaurids. Xu et al. (2001) published a cladistic analysis, placing Liaoningosaurus basal within the Nodosauridae
, while Vickaryous et al. (2004) have provisionally assigned it to the Ankylosauria
incertae sedis
. A new cladistic analysis performed by Thompson et al., 2011 suggests that Liaoningosaurus is a very basal
ankylosaurid.
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
IVPP
Institute of Vertebrate Paleontology and Paleoanthropology
The Institute of Vertebrate Paleontology and Paleoanthropology of China is a prominent research institution and collections repository for fossils, including many dinosaur and pterosaurand cat poo specimens...
V12560 (Institute of Vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
Paleontology
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
and Paleoanthropology
Paleoanthropology
Paleoanthropology, which combines the disciplines of paleontology and physical anthropology, is the study of ancient humans as found in fossil hominid evidence such as petrifacted bones and footprints.-19th century:...
, Beijing
Beijing
Beijing , also known as Peking , is the capital of the People's Republic of China and one of the most populous cities in the world, with a population of 19,612,368 as of 2010. The city is the country's political, cultural, and educational center, and home to the headquarters for most of China's...
), an essentially complete juvenile skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
compressed on a slab, was collected from the Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
(Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
stage) of Liaoxi, Yixian County, Liaoning
Liaoning
' is a province of the People's Republic of China, located in the northeast of the country. Its one-character abbreviation is "辽" , a name taken from the Liao River that flows through the province. "Níng" means "peace"...
Province, People's Republic of China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
.
The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
Liaoningosaurus paradoxus was named by Xu Xing, Wang Xiaolin and You Hailu in 2001. The generic name refers to Liaoning. The specific name refers to the confusing mix of nodosaurid and ankylosaurid features shown by the specimen.
The articulated skeleton measures approximately 34 cm in length, giving it the distinction of being the smallest-known ankylosaur specimen. The specimen is unique among all known ankylosaur fossils in the retention of the external mandibular fenestra. Antorbital fenestra
Antorbital fenestra
An antorbital fenestra is an opening in the skull, in front of the eye sockets. This skull formation first appeared in archosaurs during the Triassic Period. Living birds today possess antorbital fenestrae, but the feature has been lost in modern crocodilians...
e may also be present. Both are likely juvenile traits, just as the relatively large teeth, the retention of teeth in the praemaxilla, long feet, long lower legs and the possession of long sharp claws on the hand and feet. A real feature unique to the taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
, or autapomorphy
Autapomorphy
In cladistics, an autapomorphy is a distinctive anatomical feature, known as a derived trait, that is unique to a given terminal group. That is, it is found only in one member of a clade, but not found in any others or outgroup taxa, not even those most closely related to the group...
might be the trapezoid
Trapezoid
In Euclidean geometry, a convex quadrilateral with one pair of parallel sides is referred to as a trapezoid in American English and as a trapezium in English outside North America. A trapezoid with vertices ABCD is denoted...
form of the breast bone
Another new feature is the presence of ventral armor plating, two very large paired osteoderms covering the entire abdomen and having a surface structure sculpted with small hexagonal and rhombic elevations. Such plates had never been found with other ankylosaurians, of which the belly armor is poorly known, however. Smaller triangular osteoderms were found on the shoulder, the scapula showing the onset of a shoulder spike.
Determining the relations of Liaoningosaurus is difficult because of the young age of the individual specimen and the presence of traits both typical of ankylosaurids and nodosaurids. Xu et al. (2001) published a cladistic analysis, placing Liaoningosaurus basal within the Nodosauridae
Nodosauridae
Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous Period of what are now North America, Asia, Antarctica and Europe.-Characteristics:...
, while Vickaryous et al. (2004) have provisionally assigned it to the Ankylosauria
Ankylosauria
Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are first known to have appeared in the early Jurassic Period of...
incertae sedis
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
. A new cladistic analysis performed by Thompson et al., 2011 suggests that Liaoningosaurus is a very basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
ankylosaurid.