| Lingyuanosaurus | |
|---|---|
 | |
| Holotype specimen as originally preserved in slabs of rock before preparation | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | Maniraptora |
| Clade: | †Therizinosauria |
| Genus: | †Lingyuanosaurus Yaoet al., 2019 |
| Type species | |
| †Lingyuanosaurus sihedangensis Yaoet al., 2019 | |
Lingyuanosaurus is agenus oftherizinosauriantheropod from theEarly Cretaceous ofLiaoning Province,China. The type and only species isL. sihedangensis. It was uncovered within one of the formations that make up theJehol biota, although the exact geological formation — and therefore also its precise geological age — is unknown.[1]
Theholotype ofLingyuanosaurus, given the designationIVPP V 23589, was discovered at a fossil locality near a town calledSihedang. The specimen was recovered inside of seven rock slabs of varying sizes. The locality is just outside of the city ofLingyuan inLiaoning Province. The precise age of this locality is uncertain. The strata from which the holotype was found are a part of theJehol Group, but it is not known for certain if they belong to theYixian Formation or to theJiufotang Formation. Given the fact that the entire specimen was found in a one-square-meter area, no other fossils were found in proximity, there were no duplicated elements, and all thebones had the same color and preservation, the fossils are regarded as belonging to a single individual.[1]
Lingyuanosaurus was formally described and named in 2019 in a publication authored by Xi Yao, Chun-Chi Liao, Corwin Sullivan, andXu Xing. Thegeneric name,Lingyuanosaurus, is in reference tocounty-levelcity ofLingyuan, and theAncient Greek wordsaûros (σαῦρος), Latinized assaurus, meaning "lizard". Thespecific name,sihedangensis, is in reference to its place of discovery as well, thetown of Sihedang.[1]
Lingyuanosaurus was a relatively smalltherizinosaurian, similar in size to the closely relatedBeipiaosaurus at about 2.2 m (7.2 ft) long.[1][2] Thefemur of the specimen was only 200 mm (7.9 in) long, and Yao and colleagues used its circumference to estimate a weight of about 12 kg (26 lb).Lingyuanosaurus also had a mix of both basal and derived features, indicating that therizinosauroids were undergoing an evolutionary transition around the time that these three taxa lived.[1]
Theholotype, and only specimen, IVPP V 23589 consists of several bones of the postcranial skeleton including thevertebral centrum of acervical vertebra, five partial vertebrae (dorsals,sacrals, andcaudals), a single complete caudal vertebrae, severalribs from the middle and lower back, the proximal half of the righthumerus, the distal half of the left humerus, twomanual unguals, a mostly completeilium, part of anischium, the rightfemur, part of the lefttibia, part of the rightastragalus, and several pieces of bone that could not be identified. The anatomy preserved in these bones allowed the describers to nameLingyuanosaurus as a new taxon, distinct from bothBeipiaosaurus and the closely-related and roughly contemporaneousJianchangosaurus.Lingyuanosaurus can be distinguished from all other therizinosaurs by the followingcombination of traits: alamina (or "plate") present on the dorsal vertebrae separating the two infradiapophysealfossae, unique anatomy of thehyposphene-hypantrum articulation, and an ilium with a strongly convex upper edge and a concave lower edge, and the presence of a roughly triangle-shaped fossa just above thepubic peduncle.[1]
In their description ofLingyuanosaurus, Yao and colleagues suggested that the specimen was probably not fully-grown when it died. They inferred this from the fact that the vertebrae that are preserved are eithercentra orneural arches, suggesting that these elements had not become fully co-ossified yet while the animal was alive, which is a condition seen in somatically-mature dinosaurs. The only vertebra to be fully co-ossified in the specimen is the caudal vertebra, which indicates that the specimen, while young, was almost certainly not a hatchling.[1]
In their description ofLingyuanosaurus, Yao and colleagues conducted aphylogenetic analysis based on the dataset used by Hans Dieter-Sues and Alexander Averianov in their description of the so-called "Bissekty therizinosaur" in2016. Because of its incompleteness, they were only able to assign 45 character states toLingyuanosaurus (out of a total of over 300), however their results using multiple methodologies and datasets confirmed the genus' place withinTherizinosauria. An abbreviated version of the consensus tree found in their analysis is shown below.[1]
| Therizinosauria |
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Lingyuanosaurus is believed to represent an evolutionary transition within therizinosaurs. Its ilium shows the strongly upturnediliac crest of later-diverging therizinosaurs, in contrast to the roughly contemporaryJianchangosaurus andBeipiaosaurus. It also has a relatively robustfemur and a very deepacetabular process in comparison with those taxa and withFalcarius — which was believed to be more cursorial than later-diverging therizinosaurs. The relative shortness of thetibia relative to the femur ofLingyuanosaurus also suggests that it was not a very adept runner. However, the authors note that the evolution of these adaptations was probably not a linear process and may have involved multiple evolutions of each of these features.[1] A later publication centered on the genusBeipiaosaurus remarked that the pre-acetabular blades on the ilium ofLingyuanosaurus are very well-developed and share a similar morphology with that of the derived generaSegnosaurus andNanshiungosaurus.[3]
A study of the functional morphology of the claws oftherizinosaurs andalvarezsauroids was published by Yoshitsugu Kobayashi and colleagues in their description of the taxonParalitherizinosaurus. Their study, which examined the specific morphology of the claws on the first two digits of the fingers of all therizinosaurs from which this part of the anatomy is known. Their conclusion was that the hypertrophied manual claws of taxa likeTherizinosaurus were not of much functional use due to the lack of a dorsal lip on the proximal part of the claw which could serve as a site for muscle attachment.[4]
However, this "proximodorsal lip" is present in basal therizinosaur taxa such asLingyuanosaurus andFalcarius. This may have permitted the claws of these taxa to be used to assist in feeding, digging, or locomotion, although the authors do not suggest any such specific uses for the claws inLingyuanosaurus.[4]
No remains of theskull ofLingyuanosaurus are known, so the dietary habits of the animal are not directly known. However, most knowntherizinosaurs are believed to have been herbivorous, so it is possible thatLingyuanosaurus was as well. This genus also possibly coexisted with the similarly sized therizinosaursBeipiaosaurus andJianchangosaurus, and it may have specialized to have unique dietary habits to avoid direct competition with these taxa. However, more detailed inferences can only be made if additional specimens are discovered.[1]
Studies suggest that thepaleoenvironment of theJehol Group involved seasonal climate fluctuations, and was warm and humid, punctuated by dry seasons, in which the environment became more arid.[5] The average yearly temperature during the time ofLingyuanosaurus was 10 °C (50 °F), with relatively cold winters for the generally warm Mesozoic era.[6] A study by Wu et al. 2013 concluded thatorbital forcing, which is the effect on climate caused by shifts in the tilt of the Earth's axis and by the shape of the Earth's orbit, contributed to the climate fluctuations of this formation.[7]
It is not known with certainty to which formation the Sihedang locality belongs. Some publications list it as being a part of theYixian Formation,[8] while others consider it to be part of theJiufotang Formation.[9][10]
The Sihedang locality preserves a variety of other fossil animals. Most of these fossils belong to other dinosaurs. Among these are the smalldromaeosauridZhongjianosaurus, theconfuciusornithiformYangavis, theenantiornithineMonoenantiornis, and severalornithuromorphs such asChangzuiornis,Dingavis,Gansus, andIteravis. A genus of turtle,Jeholochelys, is also known from this locality.[9]
The Jehol biota generally preserves a wide variety of small-bodied animals. It is most famous for its well-preservedbird and other dinosaur fossils which preserve traces of feathers. Exemplars of this phenomenon includeConfuciusornis,Psittacosaurus,Microraptor,Yutyrannus, andSinosauropteryx. Other reptiles, includingchoristoderes, turtles,squamates, and a great diversity ofpterosaurs have been found from this period in large numbers. The Jehol biota also preserves a variety of mammals, includingRepenomamus – one of the largest knownMesozoic mammals – andEomaia, which is believed to be related to the common ancestor ofplacentals andmarsupials. The abundance of fish, insect, and mollusc fossils make the strata comprising the Jehol biota among the most productive fossil assemblages anywhere in the world.[11][12][13]
Media related toLingyuanosaurus at Wikimedia Commons
Data related toLingyuanosaurus at Wikispecies.jpg)
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