Лиаонингозавр: необычный анкилозаврид из Китая

Extinct genus of dinosaurs

Liaoningosaurus (meaning "Liaoning lizard") is an unusual genus of basal ankylosaurid dinosaur from the Liaoning Province, China that lived during the Early Cretaceous (late Barremian to early Aptian stages, ~125.4 to 118.9 Ma) in what is now the Yixian and Jiufotang Formation. The type and only species, Liaoningosaurus paradoxus, is known from more than 20 specimens, with some representing juveniles. It was named in 2001 by Xu, Wang and You. L. paradoxus was unusual among ornithischian dinosaurs in that it is speculated to have hunted or scavenged, with preserved gut contents showing that it may have eaten fish. Additionally, some features of its skeleton may suggest that it was partially aquatic. However, not all paleontologists agree with this interpretation. It is the oldest ankylosaurid to have had a tail club and had a wide paleogeographic and stratigraphic distribution in western Liaoning. Both Liaoningosaurus and Chuanqilong show various similarities with one another, with the latter being suggested to be a later growth stage.

The remains of a juvenile ankylosaur were collected by members of the Western Liaoning expedition team of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) from the Baicaigou locality in the Liaoning Province, China. It was recovered from the Dawangzhangzi Bed of the Yixian Formation, which dates to the late Barremian to early Aptian stages of the Early Cretaceous period. The specimen was named and described in 2001 by Xing Xu, Xiao Lin Wang and Hai Lu You. The generic name, Liaoningosaurus, is derived from the Liaoning Province and the Greek word "sauros" (lizard). The specific name is derived from the Latin word "paradoxus", in reference to a suite of highly unusual traits for an ankylosaur. The type specimen, IVPP V12560, consists of a nearly complete, articulated skeleton measuring approximately 34 centimetres (1 ft 1 in) in length that was preserved with the ventral surface exposed on a slab.

In 2016, a nearly complete skeleton of Liaoningosaurus was described by Ji Qiang, Wu Xiaochun, Cheng Yennien, Ten Fangfang, Wang Xuri and Ji Yannan. The specimen, XHPM 1206, was collected from the Jianshangou Bed of the Yixian Formation, about 160 km west from the holotype locality. The authors noted that the specimen was slightly larger than the holotype and shows features that were either previously unknown or not accurately described in the holotype such as the humerus being almost as long as the femur or tibia and the presence of five digits rather than four on the manus (hand). It is currently housed at the Xinghai Museum of Paleontology. Arbour & Currie (2015) referred two specimens; CYGYB 208, a nearly complete skeleton that is preserved on a slab with the dorsal (upper side) surface exposed; and CYGYB 237, a nearly complete skeleton that is preserved on a slab with the ventral (underside) surface exposed. In 2022, Chang Fu Zhou, Qing Liu, Xinyue Wang and Honggang Zhang described a nearly complete, associated skeleton (PMOL AD00105) of Liaoningosaurus from the Jiufotang Formation of the Liaoning Province, China. The authors considered that the presence of Liaoningosaurus in the Jiufotang Formation supports the possibility of a wide paleogeographic and stratigraphic distribution in western Liaoning. A Canadian Society of Vertebrate Palaeontology abstract book that was published in 2019 mentioned that about 20 specimens had been collected from four different localities of the Yixian Formation, and one locality from the nearby Jiufotang Formation.

The type specimen of Liaoningosaurus has an estimated length of about 34 centimetres (1 ft 1 in). It has a skull sacral length of 17.2 centimetres (6.77 inches), while a second specimen, XHPM 1206, has a skull sacral length of 19.3 centimetres (7.6 in). The largest specimen, GPMA 12 045, has a total body length of less than 45 centimetres (1 ft 5 in) and a skull sacral length of 21 centimetres (8 in), and the smallest specimen, NGMC 98 003, has a preserved length of 22 centimetres (8.66 in) with a skull sacral length of about 16 centimetres (6.299 in). The teeth have a shelf like cingulum at their bases, and a palmate crown which bears vertical flutes that coincide with the notches between marginal cusps.

With the exception of a few sub triangular plates found near the cervical and pectoral region, it completely lacks osteoderms on its body. Xu et al. (2001) identified a large bony plate present ventral to the right pelvic girdle and noted that it was covered in small tubercles. These tubercles are hexagonal and rhombic in shape, and have a diameter of about 0.5 mm. This ‘shell like’ ventral bony plate was noted as being present in no other ankylosaur.

Arbour and Currie (2015) considered the type specimen to represent a juvenile individual on basis of unfused neural arches, small size and the absence of post cervical osteoderms. It represents a freshwater lacustrine environment, lacking rivers and deltas among other variable features of freshwater settings. Such environments lacking these features include shallow lakes. The yearly temperature averaged about 10 °C (50 °F) and was temperate, with distinct wet and dry seasons. The fluctuations in the climate are due to orbital forcing. Conifers related to species that are found in modern subtropical and temperate upland forests dominated the landscape, with ferns, cycads, horsetails, and a small number of flowering plants also being present. The deconstruction and reconstruction of biotic components occurred frequently due to periodic mortality events such as volcanic eruptions, wildfires, and noxious gases erupting from the lakes. Fossils of gastropods, bivalves, ostracods, insects, amphibians, pterosaurs, dinosaurs, birds and mammals have been recovered from the Yixian Formation. Ornithischians from the formation are represented by the hadrosauroids Bolong and Jinzhousaurus; the ceratopsian Psittacosaurus; and the basal neornithischian Jeholosaurus. Saurischians include the sauropods Dongbeititan and Liaoningotitan; the dromaeosaurids Sinornithosaurus and Tianyuraptor; the troodontids Mei and Sinovenator; the therizinosaur Beipiaosaurus; the oviraptorosaurs Caudipteryx and Incisivosaurus; the ornithomimosaurs Hexing and Shenzhousaurus; the compsognathid Sinosauropteryx; and the tyrannosaurs Dilong and Yutyrannus.

One specimen of Liaoningosaurus was retrieved from the Jiufotang Formation of the Jehol Group. It overlies the Yixian Formation, and is composed of mudstones, siltstones, shales, sandstones and tuffs. Similar to the Yixian Formation, it represents a lacustrine environment lacking rivers and deltas. The Jiufotang Formation experienced less volcanism compared to its underlying formation, and fluctuated seasonally between semi arid and mesic conditions. Zhou et al. (2022) suggested that the Jehol ecosystem (the Yixian and Jiufotang Formations) may have been more suitable for the survival of juvenile ankylosaurs based on the lack of adult specimens and abundance of juvenile specimens. The Jiufotang Formation has yielded specimens of the basal ankylosaurid Chuanqilong, the ceratopsian Psittacosaurus, the dromaeosaurid Microraptor, the oviraptorosaur Similicaudipteryx, the jeholornithiforms Jeholornis and Kompsornis, and the tyrannosaur Sinotyrannus. Other vertebrate fossils found in the formation included fish, mammaliamorphs such as Fossiomanus and Liaoconodon, the choristoderans Philydrosaurus and Ikechosaurus, pterosaurs like Liaoningopterus, Sinopterus, and Guidraco, enantiornithines such as Longipteryx, Sinornis and Yuanchuavis, and a variety of early birds like Yanornis and Yixianornis.