Pinacosaurus

Pinacosaurus ("plank lizard") is a genus of medium-sized ankylosaur dinosaurs that lived from the late Santonian to the late Campanian stages of the late Cretaceous Period (roughly 80–75 million years ago), in Mongolia and China.

The type species Pinacosaurus grangeri was named in 1933. Pinacosaurus mephistocephalus named in 1999, is a second possibly valid species, differing from the type species in details of the skull armour. Of Pinacosaurus grangeri many skeletons have been found, more than of any other ankylosaur. These predominantly consist of juveniles that perhaps lived in herds roaming the desert landscape of their habitat.

Pinacosaurus was about five metres long and weighed up to two tonnes. Its body was flat and low-slung but not as heavily built as in some other members of the Ankylosaurinae. The head was protected by bone tiles, hence its name. Each nostril was formed as a large depression pierced by between three and five smaller holes, the purpose of which is uncertain. A smooth beak bit off low-growing plants that were sliced by rows of small teeth and then swallowed to be processed by the enormous hind gut. Neck, back and tail were protected by an armour of keeled osteoderms. The animal could also actively defend itself by means of a tail club.

Pinacosaurus
Temporal range: Late Cretaceous, 80–75 Ma
Pinacosaurus
Skeleton reconstruction of P. mephistocephalus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Family: Ankylosauridae
Subfamily: Ankylosaurinae
Genus: Pinacosaurus
Gilmore, 1933
Species
  • P. grangeri Gilmore, 1933 (type)
  • P.? mephistocephalus Godefroit et al., 1999
Synonyms[1]
  • Pinacosaurus ninghsiensis
    Young, 1935
  • Heishansaurus pachycephalus?
    Bohlin, 1953
  • Syrmosaurus viminocaudus
    Maleev, 1952

Discoveries

The American Museum of Natural History sponsored several Central Asiatic Expeditions to the Gobi Desert in Mongolia in the 1920s. Among the many paleontological finds from the "Flaming Cliffs" of the Djadokhta Formation in Shabarakh Usu were the original specimens of Pinacosaurus,[2] found by Walter Wallis Granger in 1923. In 1933, Charles Whitney Gilmore described a right ilium and a tail vertebra, without yet naming the animal.[3] In a later publication of the same year, he named and described the type species Pinacosaurus grangeri. The generic name is derived from Greek πίναξ, pinax, "plank", in reference to the small rectangular scutes covering the head. The specific name honours Granger, who accompanied the 1923 expedition as a paleontologist.[4]

The holotype, AMNH 6523, was found in a layer of the Djadokhta Formation, dating from the Campanian. It consists of a partially crushed skull, lower jaws, the first two neck vertebrae, and dermal bones collected in 1923.[4] The skull is still the largest known of the genus.

Saichania skeleton
Skeleton of specimen MPC 100/1305 with skull cast of Saichania holotype

Pinacosaurus is the best known Asian or worldwide ankylosaur with numerous specimens having been discovered.[5] From the original Flaming Cliffs or Shabarakh Usu several other fossils have been reported including ZPAL MgD II/1: a nearly complete skeleton; ZPAL MgD II/9: a postcranial skeleton; ZPAL MgD II/31: the handle of a tail club; and PIN 3780/3: a skull; PIN 614: a nearly complete postcranial skeleton (= Syrmosaurus viminocaudus); and possibly MPC 100/1305, a postcranial skeleton erroneously described in 2011 as belonging to Saichania. At another site, Alag Teeg, entire bonebeds have been uncovered of juvenile animals. Soviet-Mongolian expeditions in 1969 and 1970 reported thirty skeletons. Mongolian-Japanese expeditions added another thirty between 1993 and 1998. Forty were reported by Canadian expeditions between 2001 and 2006. The remains have not been all dug up and it is possible the reports partly pertain to the same material.[6] In Inner Mongolia at Bayan Mandahu, the Canada−China Dinosaur Project in 1987, 1988, and 1990 found specimens IVPP V16853: a skull with cervical halfrings; IVPP V16283: a partial skull, IVPP V16854: a nearly complete skeleton; IVPP V16346: a partial skull; and IVPP V16855: a skeleton. Other, as yet undescribed material included two finds of several juveniles huddled together, evidently killed by a sandstorm (Jerzykiewicz, 1993; Burns et al., 2011). Whereas ankylosaur skeletons have often been preserved laying on their back, most Pinacosaurus juveniles are found on their belly in a resting position, with the legs tucked in.[6]

Pinacosaurus juveniles
Juvenile specimens under excavation in 1990, with quarry map

Because of the many finds, in principle the entire juvenile skeleton is known. Pinacosaurus especially provides information on the build of the ankylosaurian skull, as in the juveniles the head armour has not yet fused with the skull proper and the sutures of the various elements are still visible. Modern studies have not yet fully covered the abundance of data. A well-preserved juvenile skull was described by Teresa Maryańska in 1971 and 1977.[7][8] In 2003, Robert Hill studied the juvenile specimen IGM 100/1014 (Hill, 2003). In 2011, Currie published a study on the hand and foot, body parts often incompletely known with other ankylosaurs.[6] The same year Michael Burns dedicated an article to four juveniles from the Bayan Mandahu ([9]). Also in 2011, the postcranial skeleton MPC 100/1305 was described in detail, though at the time referred to Saichania.[10] Most recently, Michael Burns and colleagues described and illustrated the original Alag Teeg material from the Soviet-Mongolian expeditions in 1969 and 1970.[11]

Additional species and synonyms

Pinacosaurus mephistocephalus
P. mephistocephalus skeleton

Yang Zhongjian ("C.C. Young") discovered a new specimen in the Ningxia Province at Bayanmandahu, and described it as a new species Pinacosaurus ninghsiensis in 1935.[12] The rather complete skeleton lacks a present inventory number; it is now considered to be the same species as P. grangeri. The same is true of fragmentary remains, specimen PIN 614, described as Syrmosaurus viminocaudus by Evgenii Aleksandrovich Maleev in 1952.[13] Arbour, Burns and Sissons (2009) considered Heishansaurus pachycephalus ("thick-headed Black Mountain lizard") from the Minhe Formation, near Heishan (= "Black Mountain"), Gansu Province, which is known from poorly preserved cranial and postcranial fragments, to be a junior synonym of P. grangeri as well.[1] It was first described in 1953 as a pachycephalosaur and had been usually considered a nomen dubium. In 2014, Arbour again concluded it was a nomen dubium.[14]

In 1996, a Belgian-Chinese expedition discovered a large skeleton in the Bayan Mandahu, specimen IMM 96BM3/1. It was named as Pinacosaurus mephistocephalus by Pascal Godefroit et alii in 1999. The specific name is a contraction of Mephistopheles and Greek κεφαλή, kephalè, "head", in reference to the "devilish" squamosal horns.[15] In 2010, Gregory S. Paul suggested that P. mephistopheles were a junior synonym of P. grangeri.[16] It was considered a valid species by Robert Hill in 2012, based on the "secondary dermal" (squamosal) horns and narial characteristics.[5] Arbour and Michael Burns have confirmed that the species was valid.[9][14]

In 1995, Eric Buffetaut referred ankylosaurian remains found in Shandong to a Pinacosaurus sp.[17]

Description

Pinacosaurusbcn1
P. grangeri skull

Size and distinguishing traits

Pinacosaurus was a lightly built, medium-sized ankylosaur that reached a length of five meters (sixteen ft).[18] Paul estimated the weight of a five metres long animal at 1.9 tonnes.[16] The postcranial skeleton PIN 614 measures 366 centimetres from the first neck vertebrae to the end of the tail.[8]

Pinacosaurus
Juvenile skeleton displayed in the Hong Kong Science Museum

In 2014, Arbour established some distinguishing traits of the genus. The upper snout armour does not consist of distinct tiles, caputegulae, but of a fused mass. Adult individuals have a skull that is longer than wide. This trait is shared with the distant relatives Gobisaurus and Shamosaurus, but Pinacosaurus differs from those in the possession of extra openings in the nostril and a pointy protruding caputegula on the prefrontal, directed to the front. Pinacosaurus differs from Crichtonpelta in the lack of an ornamented rear edge of the skull roof and in the cheek horn not being curved upwards.[14]

Pinacosaurus grangeri size comparison
A P. grangeri specimen compared to an average human male

Arbour also provided a list of traits in which P. grangeri and P. mephistocephalus differed from each other. P. grangeri has a notch in the snout armour just above the innermost nostril opening. P. mephistocephalus has squamosal horns extending to behind beyond the rear of the skull roof, their points representing the widest point of the skull, instead of the upper rims of the eye sockets. P. mephistocephalus also has a clear transverse narrowing of the skull roof at level of the lacrimals, just in front of the eye sockets. It had been suggested that the rear skull roof of P. mephistocephalus was more convex but Arbour concluded it essentially had the same curvature.[14] The holotype of P. mephistocephalus has very long cheek horns but a juvenile specimen, MPC 100/1344, found as part of a P. grangeri group, shows a similar elongation.[6]

Skeleton

Pinacosaurus from behind
Hind view of mounted skeleton cast of P. mephistocephalus

The adult skulls known have a length of about thirty centimetres. Pinacosaurus has exceptionally smooth praemaxillae, front snout bones, forming the bone core of the upper beak, that was in life covered with a horn sheet. The maxilla bears about fourteen teeth.

A typical and remarkable element of ankylosaurine skulls is that the nostril is in the shape of a large "narial vestibule" in which several smaller oval holes are present. With Pinacosaurus there are at least three per side. Gilmore already noticed this configuration in the original specimen.[19] To allow a comparison between the holes of the several ankylosaurine species, they have been dubbed "A", "B" and "C". The top hole A seems to access the main air-passage of the nasal cavity. In P. grangeri this hole is visible in top view through a notch in the snout armour, whereas in P. mephistocephalus the armour overhangs the hole. The opening pattern is characteristic of the genus: in Pinacosaurus the C hole is below the A hole and the B opening is on the lower outer side of the vestibule. In Pinacosaurus juveniles the C hole seems to consist of secondary smaller openings of varying number: Godefroit et al. described four pairs of openings in total in 1999, and in 2003 a juvenile specimen with five pairs of openings was described.[20] The extra C openings have been named C2 and C3. The precise function of this arrangement is unclear. There are several chambers in the praemaxilla and maxilla to which these holes are connected but it has also been suggested that some extra holes are the result of damage.[20] The larger number with juveniles could be explained by cartilage sheets not having been ossified yet.

Ankylosaurid skull anatomy
The skull elements of a juvenile Pinacosaurus on the left, compared with those of Anodontosaurus lambei

The visible sutures of the skull elements in juvenile specimens allowed for the first time to determine their precise arrangement. They generally consisted of indistinctly formed simple shapes. Several skull openings like the antorbital fenestra and the temporal fenestrae apparently closed at a very young age for they are no longer visible even in the juveniles found. The squamosal horn does not cover the entire squamosal, creating the illusion that an additional skull bone is present in front of the horn.[14] Maryańska in 1977 thought that this was a tabular bone, otherwise unknown in dinosaurs, proving that the Ankylosauria had independently evolved from the Aetosauria,[8] a hypothesis today entirely discarded. Godefroit in 1999 called it a "secondary dermal squamosal".[15] A real distinctive trait is that the quadratojugal touches the postorbital, whereas in other Thyreophora for which the condition is known, these bones are separated by the jugal. Usually it is assumed that this configuration is not unique for Pinacosaurus but a synapomorphy of the Ankylosauridae as a whole.

In 2015, a juvenile specimen was described showing a complex hyoid bone or tongue bone apparatus. It included paraglossalia at the sides, paired first and second ceratobranchials and higher epibranchials. Also the bone structure suggested that in the middle a cartilaginous basihyal was present. The strong development of the hyoid would indicate that a powerful tongue compensated for the weakly developed dentition. It was inferred that all dinosaurs had such complex tongue bones but that these were generally lost during fossilisation.[21]

Pinacosaurus metacarpus
Metacarpus of a juvenile specimen

The postcranial skeleton of the known fossils is rather lightly built. Most of these represent juveniles, however: even specimen IMM 96BM3/1, the P. mephistocephalus holotype, is no longer than about three metres. Juveniles had four rear back vertebrae fused into a "sacral rod", three true sacrals, and a tail base of seven vertebrae possessing transverse processes. Behind these about eight "free" vertebrae are present, followed by about twenty vertebrae stiffened by projections and forming the "handle" of the tail club. Like all ankylosaurids, Pinacosaurus had a bony club at the end of its tail which it likely used as a defensive weapon against predators.[22] This club was relatively small.

Pinacosaurus grangeri
A reconstruction of Pinacosaurus grangeri based on the armor of specimen MPC 100/1305 and various skeletal and fossil mounts

The torso is very flat. The forelimbs are moderately robust; the P. mephistocephalus holotype has a quite robust humerus and ulna, however. The hand is completely known, which is exceptional for ankylosaurids. It has five digits, and the phalangeal formula is 2-3-3-3-2, meaning that the innermost finger of the forelimb has two bones, the next has three, etc. The metatarsals are closely appressed and held vertical. The claws are hoof-shaped.[6]

Pinacosaurus limb elements
Limb bones

In the pelvis, the ilia flare strongly outwards to the front. The ischium is thin and curves forwards. The hindlimbs are moderately robust. The shinbone has a wide underside with well-formed condyles. Currie therefore assumed that the lower leg articulated directly with the metatarsus, the inner part of the astragalus and the entire calcaneum being absent or non-ossified cartilage elements. As in all known ankylosaurids, the foot has three toes, not four as Maryańska assumed in 1977, misled by the damaged specimen ZPAL MgD−II/9. The phalangeal formule of the toes is variable: most individuals have 0−3−3−4−0 but some exemplars possess an extra penultimate phalanx in the third toe, resulting in 0-3-4-4-0, while others lack a phalanx in the fourth toe, which causes a 0-3-3-3-0 configuration.[6]

Osteoderms

The configuration of the skin ossifications, or osteoderms, of the body is partly known: no single specimen conserves a complete set. Additional information can be gleaned from the larger specimen MPC 100/1305, a possible Pinacosaurus exemplar. The neck is protected by two cervical halfrings, consisting of keeled rectangular segments fused to an underlying bone band. This band is completely ossified even in juvenile individuals. Godefroit assumed Pinacosaurus differed from other species in having three or four segments instead of the usual six, but Arbour concluded that the normal number was in fact present.[14]

Pinacosaurus skeleton
MPC 100/1305 with Saichania skull cast, showing armour on back and limbs

The sides of the rump and the tail were occupied by moderately long, flat, recurved, triangular spikes. Parallel rows of smaller oval keeled osteoderms were present on the back. A continuous "sacral shield" on the hip, made of fused plates, is absent.

Phylogeny

Originally placed in the Nodosauridae by Gilmore,[23] Pinacosaurus is now considered to be an ankylosaurid and a likely member of the Ankylosaurinae.

The following cladogram is based on a 2015 phylogenetic analysis of the Ankylosaurinae conducted by Arbour and Currie:[24]

Ankylosaurinae

Crichtonpelta

Tsagantegia

Zhejiangosaurus

Pinacosaurus

Saichania

Tarchia

Zaraapelta

Ankylosaurini

Dyoplosaurus

Talarurus

Nodocephalosaurus

Ankylosaurus

Anodontosaurus

Euoplocephalus

Scolosaurus

Ziapelta

Pinacosaurusbcn2
Skull of juvenile P. grangeri
Pinacosaurus skull
P. mephistocephalus skull

The cladogram below follows the most resolved topology from a 2011 analysis by paleontologists Richard S. Thompson, Jolyon C. Parish, Susannah C. R. Maidment and Paul M. Barrett.[25]

Ankylosauridae

Minmi

Liaoningosaurus

Cedarpelta

Gobisaurus

Shamosaurus

Ankylosaurinae

Tsagantegia

Zhongyuansaurus

Shanxia

Crichtonsaurus

Dyoplosaurus

Pinacosaurus mephistocephalus

Ankylosaurus

Euoplocephalus

Minotaurasaurus

Pinacosaurus grangeri

Nodocephalosaurus

Talarurus

Tianzhenosaurus

Tarchia

Saichania

The difference in the relative position of the two Pinacosaurus species between the respective analyses, is influenced by the fact that the best preserved P. grangeri skulls are from juveniles, while the holotype of P. mephistocephalus is an adult with a skull that is longer than it is wide, which might cause a more basal position of the latter.

Paleobiology

Pinacosaurus in Japan
Specimen displayed in Japan

The habitat of Pinacosaurus consisted of a semi-desert interspersed with oases. No large theropods are known to have inhabited the ecosystem, though smaller ones like Velociraptor were present. It has been suggested that the relatively light build of Pinacosaurus was an adaptation to gain agility to better fight small theropods, the moderately large club being fast enough to hit these swift targets.[16]

In the group of juveniles found together at Bayan Mandahu, the individuals were all oriented into the same direction, suggesting they represent a travelling true herd simultaneously killed and covered by a sandstorm. It is remarkable that the members of such groups are all of about the same age, having an average length of circa 1.5 metres. This could be explained by the larger individuals being able to extract themselves from the sand, leaving the small members of the herd behind but in that case it is strange that no very young animals were found, the smallest being about one metre in length. The concentration of fossils at Alag Teeg has been explained as caused by a drying pool, but later research showed the sediments were deposited during a flood.[6] During their ontogenetic development, in juveniles at first the ribs fused with their vertebrae. The forelimbs strongly increased in robustness, while the hindlimbs did not become larger relative to the rest of the skeleton, indicating that the arms bore most of the weight. In the cervical halfrings, the underlying bone band developed outgrowths connecting it with the underlying osteoderms, which simultaneously fused to each other.[11] On the skull, the caputegulae first ossified at the snout and the rear rim; gradually the ossification extended towards the middle regions. On the rest of the body, the ossification process progressed from the neck onwards in the direction of the tail.[6]

A juvenile specimen of Pinacosaurus preserves large paraglossalia (triangular bones or cartilages located in the tongue) which show signs of muscular stress, and it is thought this was a common feature of ankylosaurs. Pinacosaurus and other ankylosaurs likely relied heavily on muscular tongues and hyobranchia (tongue bones) when feeding, since their teeth were fairly small and were replaced at a relatively slow rate. Some modern salamanders have similar tongue bones, and use prehensile tongues to pick up food. Though Pinacosaurus may not have fed on fibrous and woody plants, they may have had a more varied diet, including tough leaves and pulpy fruits. Inversely, this might suggest ant-eater-like insectivorous behaviour.[21]

See also

Footnotes

  1. ^ a b Arbour, V. M.; Burns, M. E.; Sissons, R. L. (2009). "A redescription of the ankylosaurid dinosaur Dyoplosaurus acutosquameus Parks, 1924 (Ornithischia: Ankylosauria) and a revision of the genus". Journal of Vertebrate Paleontology. 29 (4): 1117. doi:10.1671/039.029.0405.
  2. ^ Hill et al. 2003, p. 2–4.
  3. ^ Gilmore, C.W., 1933, "On the dinosaurian fauna of the Iren Dabasu Formation", Bulletin of the American Museum of Natural History 67: 23–78
  4. ^ a b Gilmore 1933
  5. ^ a b Hill et al. 2003, p. 2.
  6. ^ a b c d e f g h Currie, P.J., Badamgarav, D., Koppelhus, E.B., Sissons, R., and Vickaryous, M.K., 2011, "Hands, feet, and behaviour in Pinacosaurus (Dinosauria: Ankylosauridae)", Acta Palaeontologica Polonica 56(3): 489–504
  7. ^ Maryańska T., 1971, "New data on the skull of Pinacosaurus grangeri (Ankylosauria)", Palaeontologia Polonica 25: 45-53
  8. ^ a b c T. Maryańska, 1977, "Ankylosauridae (Dinosauria) from Mongolia", Palaeontologia Polonica 37: 85-151
  9. ^ a b Burns, Michael; Arbour, Victoria; Sissons, Robin; Currie, Philip (2011). "Juvenile specimens of Pinacosaurus grangeri Gilmore, 1933 (Ornithischia: Ankylosauria) from the Late Cretaceous of China, with comments on the specific taxonomy of Pinacosaurus". Cretaceous Research. 32 (2011): 174–186. doi:10.1016/j.cretres.2010.11.007.
  10. ^ Carpenter, K., Hayashi, S., Kobayashi, Y., Maryanska, T., Barsbold, R., Sato, K., and Obata, I., 2011, "Saichania chulsanensis (Ornithischia, Ankylosauridae) from the Upper Cretaceous of Mongolia", Palaeontographica, Abteilung A, 294(1-3): 1-61
  11. ^ a b Burns, Michael; Tumanova, Tatiana; Currie, Philip (Jan 2015). "Postcrania of juvenile Pinacosaurus grangeri (Ornithischia: Ankylosauria) from the Upper Cretaceous Alagteeg Formation, Alag Teeg, Mongolia: implications for ontogenetic allometry in ankylosaurs". Journal of Paleontology. 89 (1): 168–182. doi:10.1017/jpa.2014.14.
  12. ^ Young 1935.
  13. ^ Hill et al., p. 2 refers to Maleev 1952.
  14. ^ a b c d e f Arbour, Victoria Megan, 2014, Systematics, evolution, and biogeography of the ankylosaurid dinosaurs. Ph.D thesis, University of Alberta
  15. ^ a b P. Godefroit, X. Pereda-Suberbiola, H. Li and Z. Dong, 1999, "A new species of the ankylosaurid dinosaur Pinacosaurus from the Late Cretaceous of Inner Mongolia (P.R. China)", Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre 69(supplement): 17-366
  16. ^ a b c Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 232
  17. ^ Buffetaut, E., 1995, "An ankylosaurid dinosaur from the Upper Cretaceous of Shandong (China)", Geological Magazine 132: 683-692
  18. ^ Hill et al. 2003, p. 4.
  19. ^ Gilmore 1933, p. 5 and Fig. 1.
  20. ^ a b Hill et al. 2003
  21. ^ a b Robert V. Hill, Michael D. D'Emic, G. S. Bever and Mark A. Norell, 2015, "A complex hyobranchial apparatus in a Cretaceous dinosaur and the antiquity of avian paraglossalia", Zoological Journal of the Linnean Society (advance online publication) DOI: 10.1111/zoj.12293
  22. ^ Martin, A.J. (2006). Introduction to the Study of Dinosaurs. Second Edition. Oxford, Blackwell Publishing. 560 pp. ISBN 1-4051-3413-5.
  23. ^ Gilmore 1933, p. 9.
  24. ^ Arbour, V. M.; Currie, P. J. (2015). "Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs". Journal of Systematic Palaeontology. 14 (5): 1–60. doi:10.1080/14772019.2015.1059985.
  25. ^ Thompson, R. S.; Parish, J. C.; Maidment, S. C. R.; Barrett, P. M. (2012). "Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)". Journal of Systematic Palaeontology. 10 (2): 301. doi:10.1080/14772019.2011.569091.

References

  • Dixon, Dougal. 'The Complete Book of Dinosaurs.' Hermes House, 2006.
  • Fukui Prefectural Dinosaur Museum : the web site — Pinacosaurus grangeri
  • Gilmore, C. W. (December 4, 1933). "Two new dinosaurian reptiles from Mongolia with notes on some fragmentary specimens". American Museum Novitates (679): 1–20.
  • Hill, R. V.; Witmer, L. W.; Norell, M. A. (2003). "A New Specimen of Pinacosaurus grangeri (Dinosauria: Ornithischia) from the Late Cretaceous of Mongolia: Ontogeny and Phylogeny of Ankylosaurs". American Museum Novitates. 3395 (3395): 1–29. doi:10.1206/0003-0082(2003)395<0001:ansopg>2.0.co;2. hdl:2246/2821.
  • Maleev, E. A. (1952). "Novoe semeystvo pantsirnich dinosavrov is verchnego mela Mongolii" [A new family of armored dinosaurs from the Upper Cretaceous of Mongolia]. Doklady Akademii Nauk SSSR (in Russian). 87: 131–134.
  • Young, C. C. (1935). "On a new nodosaurid from Ninghsia". Palaeontologica Sinica, Series C (11): 5–27.
  • Burns, M. B.; Currie, P. J.; Sissons, R. L.; Arbour, V. M. (2011). "Juvenile specimens of Pinacosaurus grangeri Gilmore, 1933 (Ornithischia: Ankylosauria) from the Late Cretaceous of China, with comments on the specific taxonomy of Pinacosaurus". Cretaceous Research. 32 (2): 174–186. doi:10.1016/j.cretres.2010.11.007.

External links

1933 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1933.

Animantarx

Animantarx ( ann-i-MAN-tarks; meaning 'living citadel') is a genus of nodosaurid ankylosaurian dinosaur from the Upper Cretaceous of western North America. Like other nodosaurs, it would have been a slow-moving quadrupedal herbivore covered in heavy armor scutes, but without a tail club. The skull measures approximately 25 cm (10 inches) in length, suggesting the animal as a whole was no more than 3 meters (10 feet) long.

Ankylosauridae

Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. Ankylosaurids appeared 122 million years ago and went extinct 66 million years ago during the Cretaceous–Paleogene extinction event. These animals were mainly herbivorous and were obligate quadrupeds, with leaf-shaped teeth and robust, scute-covered bodies. Ankylosaurids possess a distinctly domed and short snout, wedge-shaped osteoderms on their skull, scutes along their torso, and a tail club.Ankylosauridae is exclusively known from the northern hemisphere, with specimens found in western North America, Europe, and East Asia. The first discoveries within this family were of the genus Ankylosaurus, by Peter Kaiser and Barnum Brown in Montana in 1906. Brown went on to name Ankylosauridae and the subfamily Ankylosaurinae in 1908.

Ankylosaurinae

Ankylosaurinae is a subfamily of ankylosaurid dinosaurs, existing from the Early Cretaceous about 105 million years ago until the end of the Late Cretaceous, about 66 mya. Many genera are included in the clade, such as Ankylosaurus, Pinacosaurus, Euoplocephalus, and Saichania.

Ankylosaurus

Ankylosaurus is a genus of armored dinosaur. Its fossils have been found in geological formations dating to the very end of the Cretaceous Period, about 68–66 million years ago, in western North America, making it among the last of the non-avian dinosaurs. It was named by Barnum Brown in 1908; the only species in the genus is A. magniventris. The genus name means "fused lizard", and the specific name means "great belly". A handful of specimens have been excavated to date, but a complete skeleton has not been discovered. Though other members of Ankylosauria are represented by more extensive fossil material, Ankylosaurus is often considered the archetypal member of its group, despite having some unusual features.

Possibly the largest-known ankylosaurid, Ankylosaurus is estimated to have been between 6 and 8 metres (20 and 26 ft) long and to have weighed between 4.8 and 8 tonnes (4.7 and 7.9 long tons). It was quadrupedal, with a broad, robust body. It had a wide, low skull, with two horns pointing backward from the back of the head, and two horns below these that pointed backward and down. Unlike other ankylosaurs, its nostrils faced sideways rather than towards the front. The front part of the jaws was covered in a beak, with rows of small, leaf-shaped teeth farther behind it. It was covered in armor plates, or osteoderms, with bony half-rings covering the neck, and had a large club on the end of its tail. Bones in the skull and other parts of the body were fused, increasing their strength, and this feature is the source of the genus name.

Ankylosaurus is a member of the family Ankylosauridae, and its closest relatives appear to be Anodontosaurus and Euoplocephalus. Ankylosaurus is thought to have been a slow-moving animal, able to make quick movements when necessary. Its broad muzzle indicates it was a non-selective browser. Sinuses and nasal chambers in the snout may have been for heat and water balance or may have played a role in vocalization. The tail club is thought to have been used in defense against predators or in intraspecific combat. Ankylosaurus has been found in the Hell Creek, Lance, Scollard, Frenchman, and Ferris formations, but appears to have been rare in its environment. Although it lived alongside a nodosaurid ankylosaur, their ranges and ecological niches do not appear to have overlapped, and Ankylosaurus may have inhabited upland areas. Ankylosaurus also lived alongside dinosaurs such as Tyrannosaurus, Triceratops, and Edmontosaurus.

Charles W. Gilmore

Charles Whitney Gilmore (March 11, 1874 – September 27, 1945) was an American paleontologist who gained renown in the early 20th century for his work on vertebrate fossils during his career at the United States National Museum (now the National Museum of Natural History). Gilmore named many dinosaurs in North America and Mongolia, including the Cretaceous sauropod Alamosaurus, Alectrosaurus, Archaeornithomimus, Bactrosaurus, Brachyceratops, Chirostenotes, Mongolosaurus, Parrosaurus, Pinacosaurus, Styracosaurus ovatus (now Rubeosaurus) and Thescelosaurus.

Crichtonpelta

Crichtonpelta is a genus of extinct herbivorous ankylosaurid dinosaur from the Cretaceous of China.In 2007, Lü Junchang, Ji Qiang, Gao Yubo and Li Zhixin named and described a second species of Crichtonsaurus: Crichtonsaurus benxiensis. The specific name refers to the Benxi Geological Museum.The holotype, BXGMV0012, is a skull found near Beipiao in a layer of the Sunjiawan Formation probably dating from the Albian. Specimen BXGMV0012-1, a skeleton lacking the skull, discovered in the same quarry as the holotype, was referred to the species. Furthermore, a skeleton with skull, displayed by the Sihetun Fossil Museum as a Crichtonsaurus bohlini specimen, was in 2014 referred to Crichtonpelta. In 2017, a fourth specimen was described, from the same quarry as the holotype, G20090034, consisting of a skull lacking the front snout.In 2014, Victoria Arbour concluded that Crichtonsaurus were a nomen dubium. Therefore, she named a separate genus for its second species: Crichtonpelta. The generic name combines a reference to Michael Crichton, the author of Jurassic Park, with a Greek πέλτη, peltè, "small shield". At the time this was an invalid nomen ex dissertatione. However, in 2015, Crichtonpelta was validly named by Arbour and Philip John Currie. The type species is Crichtonsaurus benxiensis; the combinatio nova is Crichtonpelta benxiensis. There was a possibility that, though Crichtonsaurus bohlini was a nomen dubium, its fossil material in fact belonged to Crichtonpelta. Arbour however, noted clear differences in the scapula and humerus between BXGMV0012-1 and LPM 101, a specimen previously referred to Crichtonsaurus bohlini: the scapula of the former has a tab-like acromion and its humerus a much longer deltopectoral crest.Arbour established several distinguishing traits. One of these was an autapomorphy, unique derived trait: the apex of the (quadrato)jugal, or cheek, horn, is pointing upwards. Also a unique combination of in themselves not unique traits is present. The upper snout armour forms an amorphous mass, not clearly separated into distinctive tiles. The jugal bone is deeper than that of Pinacosaurus. The skull roof is not notched at the lacrimal bone as in Pinacosaurus grangeri. The squamosal horns are shorter than those of Pinacosaurus mephistocephalus. However, these horns are longer and more pointed than those of Gobisaurus or Shamosaurus. The point of the cheek horn is located on the rear edge. The transverse crest on the top of the rear skull has two points.The holotype of Crichtonpelta is somewhat larger than Crichtonsaurus, itself about three to four metres long. It is uncertain whether Crichtonpelta already possessed a tail club.Crichtonpelta was, within the Ankylosauridae, placed in the Ankylosaurinae, in a basal position. If correct, this makes it the oldest known ankylosaurine.

Djadochta Formation

The Djadochta Formation (sometimes transcribed Djadokhta) is a geological formation situated in central Asia (Gobi Desert), dating from the Late Cretaceous Period. Laid down in the early Campanian, possibly starting in the latest Santonian, it is dated somewhat uncertainly at about 75-71 mya (million years ago). The type locality are the famous "Flaming Cliffs", locally known as Bayanzag ("rich in Haloxylon") or Ulaan-Ereg ("red cliffs").

It preserves an arid habitat of sand dunes, with little freshwater apart from oases and arroyos. In fact, the present-day climate at most Djadochta Formation sites differs little from what it was some 80 mya, except by being somewhat warmer and perhaps a bit less arid then. This is testimony to the fact that the location has long been so far from any major source of evaporation that little rainfall reached it, even before the Himalayas were uplifted which bar clouds from reaching today's Gobi desert.

Most notable fossil discoveries have been the first confirmed dinosaur eggs (a clutch, probably of Oviraptor) and several dinosaur finds, Protoceratops, Pinacosaurus and Velociraptor being the most prominent.

Heishansaurus

Heishansaurus, meaning "Heishan lizard" after the area in China where it was discovered, is the name given to a dubious genus of herbivorous ornithischian dinosaur.

In 1930, Swedish palaeontologist Anders Birger Bohlin discovered dinosaur fossils, in the context of the Swedish-Chinese expeditions headed by Sven Hedin, near Jiayuguan ("Chia-Yu-Kuan"), in the west of Gansu Province.

In 1953, Bohlin named these as the type species Heishansaurus pachycephalus. The generic name refers to the Heishan, the "Black Mountains". The specific name pachycephalus, meaning "thick-headed", was inspired by Bohlin's identification of the taxon as a pachycephalosaur. Today this dinosaur is more probably considered an ankylosaur. The fossils, from the Minhe Formation dating from the Late Cretaceous (Campanian or Maastrichtian stage), were fragmentary. The type is the only known specimen. The material consisted of poorly preserved cranial and postcranial fragments plus some dermal scutes. It contained skull fragments including a maxilla, teeth, vertebrae from the neck, back and tail, osteoderms and spikes. Today, the specimen is lost. Of one dorsal vertebra a cast remains, preserved in the American Museum of Natural History with the inventory number AMNH 2062.Bohlin considered the species to be a member of the pachycephalosaurians because he mistook an osteoderm for the thick skull roof typical of this group. The material is probably ankylosaurid. It has been seen as a junior synonym of Pinacosaurus but the genus is more generally considered a nomen dubium, especially since Bohlin's description can only be checked by comparison with his published drawings.

Jinyunpelta

Jinyunpelta ("Jinyun shield") is a genus of herbivorous ankylosaurine thyreophoran dinosaur from the Cretaceous Liangtoutang Formation of Jinyun County, Zhejiang, China; it has one species, the type species J. sinensis. This species is the basalmost ankylosaur known to have had a proper tail club.

Maleevus

Maleevus is a genus of herbivorous ankylosaurid dinosaur from the late Cretaceous, around 90 million years ago, of Mongolia.

Between 1946 and 1949, Soviet-Mongolian expeditions uncovered fossils at Shiregin Gashun. In 1952, Soviet palaeontologist Evgenii Aleksandrovich Maleev named some ankylosaurian bone fragments as a new species of Syrmosaurus: Syrmosaurus disparoserratus. The specific name refers to the unequal serrations on the teeth.The holotype, PIN 554/I, was found in a layer of the Bayan Shireh Formation dating from the Cenomanian-Santonian. It consists of two upper jawbones, left and right maxillae. Maleev erroneously assumed these represented the lower jaws. Referred was specimen PIN 554/2-1, the rear of the skull of another individual.In 1977, Teresa Maryańska noted a similarity with another Mongolian ankylosaur, Talarurus, in that both taxa have separate openings for the ninth to twelfth cerebral nerve; she therefore renamed the species as Talarurus disparoserratus. Having determined that Syrmosaurus is a junior synonym of Pinacosaurus, Soviet palaeontologist Tatyana Tumanova named the material as a new genus Maleevus in honor of Maleev in 1987. The type species remains Syrmosaurus disparoserratus, the combinatio nova is Maleevus disparoserratus. In 1991, George Olshevsky named the species as a Pinacosaurus disparoserratus. In 2014, Victoria Megan Arbour determined that the rear skull was not different from that of many other ankylosaurids and that the single distinguishing trait of the teeth, a zigzag pattern on the cingulum, was shared with Pinacosaurus. She concluded that Maleevus was a nomen dubium.The preserved maxillae have length of about twelve centimetres. This indicates that Maleevus was a medium-sized ankylosaur.

Syrmosaurus disparoserratus was by Maleev placed in the Syrmosauridae. Today it is seen as a member of the Ankylosauridae.

Saichania

Saichania (Mongolian meaning "beautiful one") is a genus of herbivorous ankylosaurid dinosaur from the Late Cretaceous period of Mongolia and China.

The first fossils of Saichania were found in the early 1970s in Mongolia. In 1977 the type species Saichania chulsanensis was named. The description of this species has been based on limited fossil material; especially the rear of the animal is not well known.

Saichania was over five metres long and weighed over two tonnes. It was more robustly built than other members of the Ankylosauridae. Neck vertebrae, shoulder girdle, ribs and breast bones were fused or firmly connected. Its body was flat and low-slung, standing on four short legs. The forelimbs were very powerful. The head was protected by bulbous armour tiles. It could defend itself against predators like Tarbosaurus with a tail-club. On the torso keeled osteoderms were present. Saichania bit off plants in its desert habitat with a horny beak and processed them in its wide hindgut.

Scolosaurus

Scolosaurus is an extinct genus of ankylosaurid dinosaurs within the subfamily Ankylosaurinae. It is known from either the lower levels of the Dinosaur Park Formation or upper levels of the Oldman Formation (the location of the type specimen's quarry is uncertain) in the Late Cretaceous (latest middle Campanian stage, about 76.5 Ma ago) of Alberta, Canada. It contains two species, S. cutleri and S. thronus.

Talarurus

Talarurus ( TAL-ə-ROOR-əs; meaning "Wicker tail") is an extinct genus of ankylosaurid dinosaur that lived approximately 90 million years ago during the latter part of the Cretaceous Period in what is now Mongolia. Talarurus was a hippopotamus-sized, heavily built, ground-dwelling, quadrupedal herbivore, that could grow up to an estimated 6 m (19.7 ft) long. Like other ankylosaurs it had heavy armour and a club on its tail. Along with Tsagantegia, Talarurus is one of the oldest known ankylosaurines from Asia and one of the better-known ankylosaurs from Mongolia.

Tanius

Tanius (meaning "of Tan") is a genus of hadrosauroid dinosaur. It lived in the Late Cretaceous of China. The type species, named and described in 1929 by Carl Wiman, is Tanius sinensis. The generic name honours the Chinese paleontologist Tan Xichou ("H.C. Tan"). The specific epithet refers to China. In 2010 Gregory S. Paul estimated the length of Tanius at seven metres and the weight at two tonnes.

Tarchia

Tarchia (meaning "brainy one") is a genus of herbivorous ankylosaurid dinosaur from the late Cretaceous of Mongolia.

Tianzhenosaurus

Tianzhenosaurus (Tianzhen + Greek sauros="lizard") is a genus of ankylosaurid dinosaurs discovered in Tianzhen County, at Kangdailiang near Zhaojiagou Village, in Shanxi Province, China, in the Late Cretaceous Huiquanpu Formation. Thus far, a virtually complete skull and postcranial skeleton have been assigned to the genus, which is monotypic (T. youngi Pang & Cheng, 1998).

This was a medium-sized ankylosaurian, the skull measuring 28 cm (11 in) in length, with a total body length around 4 m (13 ft).

Vickaryous et al. (2004) placed Tianzhenosaurus within the Ankylosauridae, nested as the sister group to Pinacosaurus. Some authors have suggested that Tianzhenosaurus is actually a junior synonym of Saichania chulsanensis.

Timeline of ankylosaur research

This timeline of ankylosaur research is a chronological listing of events in the history of paleontology focused on the ankylosaurs, quadrupedal herbivorous dinosaurs who were protected by a covering bony plates and spikes and sometimes by a clubbed tail. Although formally trained scientists did not begin documenting ankylosaur fossils until the early 19th century, Native Americans had a long history of contact with these remains, which were generally interpreted through a mythological lens. The Delaware people have stories about smoking the bones of ancient monsters in a magic ritual to have wishes granted and ankylosaur fossils are among the local fossils that may have been used like this. The Native Americans of the modern southwestern United States tell stories about an armored monster named Yeitso that may have been influenced by local ankylosaur fossils. Likewise, ankylosaur remains are among the dinosaur bones found along the Red Deer River of Alberta, Canada where the Piegan people believe that the Grandfather of the Buffalo once lived.The first scientifically documented ankylosaur remains were recovered from Early Cretaceous rocks in England and named Hylaeosaurus armatus by Gideon Mantell in 1833. However, the Ankylosauria itself would not be named until Henry Fairfield Osborn did so in 1923 nearly a hundred years later. Prior to this, the ankylosaurs had been considered members of the Stegosauria, which included all armored dinosaurs when Othniel Charles Marsh named the group in 1877. It was not until 1927 that Alfred Sherwood Romer implemented the modern use of the name Stegosauria as specifically pertaining to the plate-backed and spike-tailed dinosaurs of the Jurassic that form the ankylosaurs' nearest relatives. The next major revision to ankylosaur taxonomy would not come until Walter Coombs divided the group into the two main families paleontologists still recognize today; the nodosaurids and ankylosaurids. Since then, many new ankylosaur genera and species have been discovered from all over the world and continue to come to light. Many fossil ankylosaur trackways have also been recognized.

Wangshi Group

The Wangshi Group (Chinese: 王氏群; pinyin: Wángshì Qún) is a geological Group in Shandong, China whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the group.

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