|A cast of specimen PIN 3142/250, the holotype of T. teresae|
In 1970, a Polish-Mongolian expedition discovered an ankylosaurian skull near Khulsan.
In 1977, Teresa Maryańska named and described the type species Tarchia kielanae. The generic name is derived from Mongolian tarkhi, "brain" and Latin ~ia, in reference to a brain size presumed larger than that of the related form Saichania. The specific name honours Professor Zofia Kielan-Jaworowska, the leader of the expedition.
The holotype, ZPal MgD-I/111, was discovered in the Upper Cretaceous (possibly Campanian-Maastrichtian) Barun Goyot Formation (previously known as the 'Lower Nemegt Beds') of the Nemegt Basin of Mongolia. It consists of a skull roof, braincase and rear skull elements. Maryańska referred three additional specimens: ZPAL MgDI/43, a large postcranial skeleton containing three "free" tail vertebrae, twelve tail vertebrae of the "handle" of the tail club and a scute; ZPAL MgDI/49, a right humerus; and PIN 3142/251, a skeleton with skull, that as yet remains undescribed.
In 1977, Tatyana Tumanova named a second species: Tarchia gigantea. This was a renaming of Dyoplosaurus giganteus Maleev 1956, which had been based on specimen PIN 551/29. In 1987, Tumanova concluded that both species were identical. This would make Dyoplosaurus giganteus the senior synonym of Tarchia kielanae. This was generally accepted and Tarchia gigantea became the usual species name, as a combinatio nova replacing Tarchia kielanae. However, recent study by Victoria Megan Arbour indicates that D. giganteus is indistinguishable from other ankylosaurs from the late Campanian-Maastrichtian of Mongolia, and hence a nomen dubium; the study revived the name Tarchia kielanae. A rump with tail and club, specimen ZPAL MgD I/113, once referred to Dyoplosaurus giganteus and subsequently to Tarchia gigantea, was by Arbour seen as different from the D. giganteus holotype.
The study by Arbour also concluded that specimen PIN 3142/250, in 1977 referred to Tarchia by Tumanova, probably belonged to Saichania instead. This would radically change the common image of Tarchia as this exemplar had been by far the best preserved and most illustrations, museum mounts and indeed scientific research had been based on it. Arbour discovered that the holotype of Tarchia shared distinguishing traits with that of Minotaurasaurus Miles & Miles 2009, concluding that the latter is a junior synonym of Tarchia.
Subsequently, in 2016, a study conducted by Penkalski & Tumanova indicated that PIN 3142/250 is not referable to Saichania due to significant anatomical differences, but instead represents a new species of Tarchia, T. teresae. The study also recognized Minotaurasaurus as a distinct genus.
Size estimates of Tarchia have been largely based on Dyoplosaurus giganteus, the holotype of which is one of the largest ankylosaurian individuals known. This would make Tarchia the longest known Asian ankylosaur, with an estimated body length of 8 metres (26 ft). Confusingly, the skull size often mentioned, with a length of 40 centimetres (16 in) and width of 45 centimetres (18 in), was again based on specimen PIN 3142/250, a much smaller individual. The holotypes of Tarchia kielanae and Minotaurasaurus also indicate a medium size. In 2010, Gregory S. Paul had estimated a body length of 4.5 metres and a weight of 1.5 tonnes.
As an ankylosaurid, Tarchia would have had a broad, low-slung body, positioned on strong short legs. The body would have been protected by skin ossifications, named osteoderms. It probably had a bony tail club, for active defence against predators.
Tarchia had previously been distinguished from Saichania on the basis of its relatively larger basicranium, an unfused paroccipital process-quadrate contact and, based on PIN 3142/250, the fact that the premaxillary rostrum is wider than the maximum distance between the tooth rows in the maxillaries. In 2014, Arbour established two distinguishing traits apart from those known exclusively from the holotype of Minotaurasaurus; the back of the head is visible in top view; and deep groove runs along the front and outer side of the squamosal horn, and at the front it surrounds around an accessory osteoderm placed on the rear supraorbital, forming a deep furrow.
The 2016 redescription of Tarchia notes that it differs from Saichania in having a postorbital fossa (which separates the squamosal horn from the supraorbital) and an accessory osteoderm; the occiput being visible in dorsal view; the large, deep braincase; the foramen magnum being higher than it is wide; and the nuchal osteoderms being taller laterally than medially. In addition, it differs from both Saichania and Minotaurasaurus in that it lacks postocular caputegulae (or small, polygonal bony plates behind the orbit) and has a proportionally high occiput in caudal view. The study additionally found that PIN 3142/250 (i.e. T. teresae) can be distinguished from T. kielanae in that the accessory osteoderm is not fused to the roof of the skull, the quadrate and paroccipital process are not fused, the back of the skull roof is strongly sculptured, and the openings for the fourth to twelfth cranial nerves is bifurcated.
Much information given about Tarchia in older work refers to PIN 3142/250 (which was generally referred to Saichania until it was named as T. teresae in 2016). In 2001, it was stated that, in Tarchia, wear facets indicative of tooth-to-tooth occlusion are present; this likely does not refer to the holotype specimen, since in the holotype no teeth are preserved.
Vickaryous et alii in 2004 stated that Tarchia was basal to two distinct clades of Late Cretaceous ankylosaurids: one comprising North American taxa (Ankylosaurus, Euoplocephalus) and the other comprising Asian taxa (Pinacosaurus spp., Saichania, Tianzhenosaurus, Talarurus). However, this was again based on PIN 3142/250, the characters of which usually defined the operational taxonomic unit named Tarchia in the various cladistic analyses. Remarkably, Tarchia and Saichania nevertheless in these analyses often occupied very different positions.
A limited phylogenetic analysis conducted in the 2016 redescription of Tarchia, focusing on the interrelationships between Tarchia, Saichania, and Minotaurasaurus, is reproduced below.
The rocks in which Tarchia fossils were found likely represent eolian dunes and interdune environments, with small intermittent lakes and seasonal streams. Hence, we know that Tarchia was a desert animal. On the other hand, well-watered forest would have been present. Tarchia would have been preyed upon by Tarbosaurus.
Akainacephalus is a genus of herbivorous ankylosaurid dinosaur from the Campanian age Kaiparowits Formation of southern Utah. The type and only species is Akainacephalus johnsoni, known from the most complete ankylosaur specimen ever discovered from southern Laramidia, including a complete skull, tail club, a number of osteoderms, limb elements and part of its pelvis, among other remains.Ankylosauridae
Ankylosauridae () are a family of the armored dinosaurs within Ankylosauria, and 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.Anodontosaurus
Anodontosaurus is an extinct genus of ankylosaurid dinosaurs within the subfamily Ankylosaurinae. It is known from the entire span of the Late Cretaceous Horseshoe Canyon Formation (mid Late Campanian to "middle" Maastrichtian stage, about 72.8-67 Ma ago) of southern Alberta, Canada. It contains two species, A. lambei and A. inceptus.Barun Goyot Formation
The Barun Goyot Formation (West Goyot Formation) is a geological formation dating to the Late Cretaceous Period. It is located within and is widely represented in the Gobi Desert Basin, in the Ömnögovi Province of Mongolia.Dongyangopelta
Dongyangopelta is an extinct genus of nodosaurid ankylosaurian dinosaur known from the "middle" Cretaceous Chaochuan Formation (Albian or Cenomanian stage) of Dongyang, Zhejiang Province, China. Dongyangopelta was first named by Rongjun Chen, Wenjie Zheng, Yoichi Azuma, Masateru Shibata, Tianliang Lou, Qiang Jin and Xingsheng Jin in 2013 and the type species is Dongyangopelta yangyanensis. It differs from Zhejiangosaurus, the second nodosaurid from southeast China, in the characters of presacral rod, ilium, and femur. Donyangopelta is distinguishable from Zhejiangosaurus only on the basis of the morphology of its pelvic shield.Euoplocephalus
Euoplocephalus ( yoo-OP-loh-SEF-ə-ləs) is a genus of very large, herbivorous ankylosaurian dinosaurs, living during the Late Cretaceous of Canada. It has only one named species, Euoplocephalus tutus.
The first fossil of Euoplocephalus was found in 1897 in Alberta. In 1902, it was named Stereocephalus, but that name had already been given to an insect, so it was changed in 1910. Later, many more ankylosaurid remains were found from the Campanian of North America and often made separate genera. In 1971, Walter Coombs concluded that they all belonged to Euoplocephalus which then would be one of the best-known dinosaurs. Recently however, experts have come to the opposite conclusion, limiting the authentic finds of Euoplocephalus to about a dozen specimens. These include a number of almost complete skeletons, so much is nevertheless known about the build of the animal.
Euoplocephalus was about five and a half meters long and weighed about two and a half tonnes. Its body was low-slung and very flat and wide, standing on four sturdy legs. Its head had a short drooping snout with a horny beak to bite off plants that were digested in the large gut. Like other ankylosaurids, Euoplocephalus was largely covered by bony armor plates, among them rows of large high-ridged oval scutes. The neck was protected by two bone rings. It could also actively defend itself against predators like Gorgosaurus using a heavy club-like tail end.Minotaurasaurus
Minotaurasaurus is a genus of ankylosaurine ankylosaurid dinosaur that lived during the Late Cretaceous. It was named in 2009 by Clifford A. Miles and Clark J. Miles and the type species is Minotaurasaurus ramachandrani. The generic name is explained by the describers as meaning "man-bull lizard"; the specific epithet honours Vilayanur S. Ramachandran who purchased the fossil for $10,000 from the trader Hollis Butts, based in Japan, and made it available to science. It is known only from a complete skull of unknown provenance, but probably recovered from the Gobi Desert. While it had a distinctive armored bull-like head and a more primitive braincase, it shares the typical features of an ankylosaurid.
A controversy has surfaced around the provenance of this skull. Some paleontologists claim that this fossil was removed from the Gobi desert without the permission of the Chinese government and sold without proper documentation. V.S. Ramachandran, who purchased the fossil in Tucson, Arizona (United States), says that he would be happy to repatriate the fossil to the appropriate nation, if someone shows him "evidence it was exported without permit". For a short time, the specimen was on loan to the Victor Valley Museum in Apple Valley, California, but in 2007, Ramachandran reacquired it.A 2014 study by Victoria Arbour, Philip Currie, and Demchig Badamgarav concluded that Minotaurasaurus ramachandrani is probably a junior synonym of Tarchia kielanae; a redescription of the cranial anatomy of Tarchia in 2016, however, concluded that Minotaurasaurus was a distinct taxon.Nemegt Formation
The Nemegt Formation (or Nemegtskaya Svita) is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. It overlies and sometimes interfingers with the Barun Goyot Formation. Interfingering has been noted at the stratotype (Red Walls) and Khermeen Tsav. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, and a diverse fauna of dinosaurs, including birds. The climate associated with it was wetter than when preceding formations were deposited; there seems to have existed at least some degree of forest cover. Fossilized trunks have been also found.
There has been no absolute dating of the Nemegt Formation. It is, however, almost certainly early Maastrichtian c 71-70 Ma. Gradzinski and others considered a Campanian age possible but more recent research indicates otherwise. A Campanian age no longer seems credible, because the Alagteegian (or lower Djadokhtan, at the locality "Chuluut Uul") has been radiometrically dated at about 73.5 Ma or even younger (a more recent K/Ar date is 71.6 +/- 1.6 Ma). The c 73.5 (or perhaps 72) Ma Alagteegian is separated from the Nemegt by the "classic" Djadokhtan (e.g. Bayan Dzag), later Djadohktan (represented by Ukhaa Tolgod) and Barungoyotian (Khulsan). All these intervening horizons almost certainly represent more than the 1.5 million years between the dated Alagteegian level and the onset of Maastrichtian time (72.1 million Ma according to current dating). Ergo the Nemegt is entirely Maastrichtian. See also Shuvalov, Sochava and Martinsson The Age of Dinosaurs in Russia and Mongolia. The presence of Saurolophus further supports an early Maastrichtian age as the same genus occurs in the early Maastrichtian Horseshoe Canyon formation.Nodocephalosaurus
Nodocephalosaurus is a genus of herbivorous ankylosaurine ankylosaurid dinosaur from Upper Cretaceous (late Campanian stage) deposits of San Juan Basin, New Mexico. The holotype was recovered from the Late Campanian De-na-zin Member of the Kirtland Formation and consists of an incomplete skull. Nodocephalosaurus (Greek nodus = knob, kephale = head and sauros = lizard) is a monotypic genus, including only the type species, Nodocephalosaurus kirtlandensis. Dinosaurs like Nodocephalosaurus resembled Asian forms, and may be evidence for Asian dinosaurs migrating to North America in the Late Cretaceous.Nodosaurinae
Nodosaurinae is a group of ankylosaurian dinosaurs named in 1919 by Othenio Abel.Nodosaurus
Nodosaurus (meaning "knobbed lizard") is a genus of herbivorous ankylosaurian dinosaur from the Late Cretaceous, the fossils of which are found in North America.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.Silvisaurus
Silvisaurus, from the Latin silva "woodland" and Greek sauros "lizard", is a nodosaurid ankylosaur from the middle Cretaceous of Kansas.T. gigantea
T. gigantea may refer to:
Tarchia gigantea, an ankylosaurid dinosaur species from the late Cretaceous of Mongolia
Tegenaria gigantea, the giant house spider, a spider species
Thargelia gigantea a moth species found in Morocco, Algeria, Libya, Israel and the Sinai
Tritonia gigantea, a marine nudibranch gastropod species
Tyto gigantea, an extinct barn owl species from what is now Gargano, Italy, dating back to the late MioceneTatisaurus
Tatisaurus is a genus of ornithischian dinosaur from the Early Jurassic from the Lower Lufeng Formation in Yunnan Province in China. Little is known as the remains are fragmentary.Teresa Maryańska
Teresa Maryańska is a Polish paleontologist who has specialized in Mongolian dinosaurs, particularly pachycephalosaurians and ankylosaurians. Peter Dodson (1998 p. 9) claims that in 1974 Maryanska together with Halszka Osmólska were among the first "women to describe new kinds of dinosaurs". She is considered not only as one of Poland's but also one of the world's leading experts on dinosaurs.A member of the 1964, 1965, 1970, and 1971 Polish–Mongolian expeditions to the Gobi Desert, she has described many finds from these rocks, often with Halszka Osmólska. Among the dinosaurs she has described are:
Saichania and Tarchia (1977)
with Osmólska, Homalocephale, Prenocephale, and Tylocephale (and Pachycephalosauria) (1974), Bagaceratops (1975), and Barsboldia (1981)
and with Osmόlska and Altangerel Perle, Goyocephale (1982).Alan Feduccia notes that Maryanska and her colleagues (Osmólska and Wolsan) produced in 2002 the "most impressive analysis of the oviraptorosaurs".Amongst her many publications are contributions to three chapters of the 2nd edition of the highly respected The Dinosauria: the chapters on the Therizinosauroidea, the Ankylosauria and on the Pachycephalosauria.As of 2004, she was affiliated with the Muzeum Ziemi of the Polska Akademia Nauk. She was assistant director of Muzeum Ziemi.Zaraapelta
Zaraapelta is an extinct genus of herbivorous ankylosaurid thyreophoran dinosaur from the Late Cretaceous of Mongolia. The type species is Zaraapelta nomadis, named and described by Arbour et alii in 2014. Zaraapelta is known from a single skull from the Barun Goyot Formation. It was found to be closest to Tarchia in the phylogenetic analysis within its description.