Talarurus

Talarurus (/ˌtæləˈrʊərəs/ 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.

Talarurus
Temporal range: Late Cretaceous, 90 Ma
Dinosaurium, Talarurus plicatospineus 2
Front view of skeleton
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Family: Ankylosauridae
Subfamily: Ankylosaurinae
Genus: Talarurus
Maleev, 1952
Species:
T. plicatospineus
Binomial name
Talarurus plicatospineus
Maleev, 1952

Discovery

Talarurus plicatospineus skull 2
The skull of the PIN mount; only the top is authentic

Talarurus remains have been discovered in the southeastern parts of the Gobi Desert in what is now Mongolia. The type specimen PIN 557-91 was discovered in 1948 by a joint Soviet-Mongolian Paleontological Expedition, and recovered from sandy, red calcareous claystone at the Bayn Shire locality of the Bayan Shireh Formation. Specimen PIN 557, the original holotype designated by Maleev, included a fragmentary skull with the posterior part of the skull roof, including the occipital region and the basicranium, numerous vertebrae, several ribs, a scapulocoracoid, a humerus, a radius, an ulna, a nearly complete manus, a partial ilium, an ischium, a femur, a tibia, a fibula, a nearly complete pes, and assorted armor and scutes. In fact it consisted of fragmentary remains of six individuals discovered at the site. Elements of all these specimens were combined into a skeletal mount exhibited at the Moscow Palaeontological Institute. The skull was restored after the model of Pinacosaurus. In some respects the mount is outdated: e.g. it shows the forelimbs as strongly splayed. Elements were also incorrectly combined: segments of the halfrings protecting the neck were added to the side of the rump, on the ribcage, and the composite foot was restored with four toes, though likely only three were present.[1] In 1977, Teresa Maryańska chose PIN 557-91, the rear of the skull, as the lectotype.[2]

The genus name Talarurus means "basket tail", and is derived from the Greek word talaros (τάλαρος), and the Latinized form "urus" of the Greek word οὐρά, oura, meaning "tail". The genus name is a reference to the club end of the tail which bears resemblance to a wicker basket, and the length of the tail which consists of interlaced bony struts, reminiscent of the weave that is employed when making wicker baskets. The type and only valid species known today is Talarurus plicatospineus. The specific name "plicatospineus" is derived from the Latin words plicatus which means "folded" and spineus which means "thorny". This is a reference to the corrugated spines which are present on the surface of its armor plates.[3][4] Talarurus was described and named by Russian paleontologist Evgeny Maleev in 1952.[5]

Talarurus plicatospineus - MUSE
Skeleton at MUSE - Science Museum in Trento

Specimen PIN 3780/1 was collected from terrestrial sediments at the Bayshin-Tsav locality of the Bayan Shireh Formation, by a joint Soviet-Mongolian Paleontological Expedition in 1975 and is now reposited at the Paleontological Institute, Russian Academy of Sciences, in Moscow.[6] This material was assigned to Talarurus and is also considered to date from the Turonian stage of the Cretaceous. This specimen consists of the top of a skull and a fragmentary skeleton.

Since 2006, in the context of the Korea-Mongolia Joint International Dinosaur Project, numerous additional specimens have been referred to Talarurus, found at the Bayan Shireh and at Shine Us Khudag. These in 2014 were still undescribed.[1]

Talarurus is now known from at least a dozen individual specimens, from various localities at the Bayan Shireh Formation. Specimen PEN AN SSR 557 consists of a dorsal vertebra with an attached rib, and a dermal scute. Another specimen referred to this genus from the Bayshin-Tsav locality is composed of an (undescribed) incomplete skull with cranial roof, occipital part and braincase. A second undescribed specimen, collected at the Baga Tarjach locality, consists of a fragment of a maxilla with eight teeth.

In 1977, Maryańska renamed Syrmosaurus disparoserratus (Maleev, 1952) into a second species: Talarurus disparoserratus.[2] In 1987, this was made the separate genus Maleevus.[7]

Description

Talarurus and Achillobator
Restoration of Talarurus being surrounded by Achillobator

The skull of Talarurus measured approximately 24 centimetres (9.4 in) in length by approximately 22 centimetres (8.7 in) wide, and its body length has been estimated at 4 to 6 metres (13 to 20 ft). In 2010, Gregory S. Paul estimated the length at five metres, the weight at two tonnes.[8]

Talarurus was described by Malejev as having had five fingers on the hand and four toes on the foot. However, a four-toed foot was not found in articulation; the mounted foot is a composite and three is the more likely number as all other known ankylosaurids show three toes; earlier reports that Pinacosaurus also possessed four are incorrect.[1] Another presumed diagnostic characteristics: that the osteoderms had a furrowed ornamentation, making for a specially formidable armour, with each plate adorned with additional pleated spines, was also based on a misunderstanding. These were segments of the halfrings protecting the neck, with their typical low keels. The mount has the further peculiarity that it shows Talarurus as built like a hippopotamus, with a barrel-shaped thorax, not with the characteristic ankylosaurid low and wide body type. This was caused by an incorrect positioning of the ribs as if they were appending instead of sticking out sideways; this mistake also prevented a mounting of the wide upper pelvic elements.

Authentic traits of Talarurus include dorsal vertebrae with transversely broad hypapophyses, swellings of the lower front centrum rims. There is a sacral rod of four rear dorsal vertebrae, connected to the true sacrum consisting of four sacrals and a caudo-sacral. The tail club of the mount is rather small.

Distinguishing anatomical features

Talarurus plicatospineus skull
The skull of the mount shows the V-shaped zone between the eyes, the only known autapomorphy of Talarurus

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism.

Diagnoses provided by Malejev in 1956 and Tumanova in 1987, were of limited utility as they largely listed traits shared with many other ankylosaurids.[1]

According to Coombs and Maryańska (1990), Talarurus can be distinguished based on the following characteristics:[9]

  • The skull is relatively long and narrow
  • The occipital condyle is partially visible when observed from above, meaning the back of the head is not strongly inclined to the rear
  • The maxillary teeth, of the upper jaw, have swollen bases cut on the labial, outer, side by W-shaped furrows
  • The presence of a pentadactyl manus, and a tetradactyl pes, thus of five fingers in the hand and four toes in the foot
  • The postcranial bones, those behind the skull, are wide relative to their length
  • The armor plates are ribbed
  • The tail club is relatively small

Arbour noted in 2014 that the foot in fact had three toes. She established a single autapomorphy: on the frontals, at the middle skull roof, a raised V- shaped region is present. Also she determined that Talarurus differed from all known ankylosaurids with the exception of the American Nodocephalosaurus in the possession of caputegulae, head armour tiles, on the frontals and nasals, that are cone-shaped with a circular base.[1]

Classification and phylogeny

Talarurus plicatospineus tail
Tail

Talarurus was assigned to the Ankylosauridae by Maleev in its original description in 1952. In 1978, Walter Preston Coombs posited that it was the same dinosaur as Euoplocephalus although subsequent study did not support this assertion.[10] Maryańska in 1977 demonstrated that it differed from Euoplocephalus, citing the shape of the skull, the morphology of the palate, and the presence of four pedal digits.[2]

Ankylosaurid phylogenetic relations are hard to determine because many taxa are only partially known, the exact armour configuration has rarely been preserved, fused osteoderms obscure many details of the skull and the Ankylosauridae are conservative in their postcranial skeleton, showing little variation in their vertebrae, pelves and limbs. Previously it was assumed that as one of the oldest known ankylosaurids, Talarurus possessed some basal characters that are shared with nodosaurids but were later lost in more advanced ankylosaurs, such as the presence of four toes. However, the presumed "primitive" traits proved to be largely artefacts of the initial skeletal restoration. Recent phylogenetic analysis provides evidence for an assignment of Talarurus to the Ankylosaurinae, a derived ankylosaurid group. This can be reconciled with its relatively old geological age by the possibility that the Ankylosauridae as a whole appeared much earlier during the Early Jurassic, which must have been true if they were the sister group of the Nodosauridae in the sense proposed by Coombs in 1978; i.e. if all polacanthines were nodosaurids.

The following cladogram is based on a 2015 phylogenetic analysis of the Ankylosaurinae conducted by Arbour and Currie:[11]

Ankylosaurinae

Crichtonpelta

Tsagantegia

Zhejiangosaurus

Pinacosaurus

Saichania

Tarchia

Zaraapelta

Ankylosaurini

Dyoplosaurus

Talarurus

Nodocephalosaurus

Ankylosaurus

Anodontosaurus

Euoplocephalus

Scolosaurus

Ziapelta

Vickaryous et al. (2004) note the presence of two distinct ankylosaurid clades during the Late Cretaceous, "one consisting of North American taxa and the other restricted to Asian taxa. The oldest member of the Asian clade...is Talarurus plicatospineus."[12] However, Arbour in 2014 recovered trees in which Talarurus was more closely related to North-American forms than to Asian ankylosaurids. In some of these Talarurus was the sister species of Nodocephalosaurus.[1]

Paleoecology

Sediments found in the Bayan Shireh Formation are thought to date from the late Turonian or early Santonian stage of the Late Cretaceous period, about 90 to 85 million years ago. The age of these sediments has been determined by trying to find comparable remains in layers elsewhere.

Existing evidence suggests that the habitat that Talarurus lived in were lowland floodplains. It shared its paleoenvironment with carnivorous dromaeosaurids, therizinosaurs, and other ankylosaurians, like Tsagantegia

See also

References

  1. ^ a b c d e f Arbour, Victoria Megan, 2014. Systematics, evolution, and biogeography of the ankylosaurid dinosaurs. Ph.D thesis, University of Alberta
  2. ^ a b c Teresa Maryańska, 1977. "Ankylosauridae (Dinosauria) from Mongolia". Palaeontologia Polonica 37: 85-151
  3. ^ Liddell, Henry George and Robert Scott (1980). A Greek-English Lexicon (Abridged Edition). United Kingdom: Oxford University Press. ISBN 0-19-910207-4.
  4. ^ Dinochecker. "Talarurus". Retrieved 23 April 2014.
  5. ^ Maleev, Evgeny A. (1952). "Noviy ankilosavr is verchnego mela Mongolii" [A new ankylosaur from the Upper Cretaceous of Mongolia]. Doklady Akademii Nauk SSSR. 87 (2): 273–276.
  6. ^ S. M. Kurzanov and T. A. Tumanova. 1978. "The structure of the endocranium in some Mongolian ankylosaurs". Paleontological Journal 1978(3):369-374.
  7. ^ T.A. Tumanova, 1987, "Pantsirnyye dinozavry Mongolii", Trudy Sovmestnaya Sovetsko-Mongol'skaya Paleontologicheskaya Ekspeditsiya 32: 1-80
  8. ^ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 231
  9. ^ Coombs, WP, Jr. & T Maryanska (1990), Ankylosauria in DB Weishampel, P Dodson, & H Osmólka (eds), The Dinosauria. Univ. Calif. Press, pp. 456-483.
  10. ^ Coombs WP Jr (1978) The families of the ornithischian dinosaur order Ankylosauria. Palaeontology 21: 143–170.
  11. ^ Arbour, V. M.; Currie, P. J. (2015). "Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs". Journal of Systematic Palaeontology: 1–60. doi:10.1080/14772019.2015.1059985.
  12. ^ Vickaryous, Maryanska, and Weishampel 2004. Chapter Seventeen: Ankylosauria. in The Dinosauria (2nd edition), Weishampel, D. B., Dodson, P., and Osmólska, H., editors. University of California Press.
1952 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 1952.

Acantholipan

Acantholipan is a genus of herbivorous nodosaurid dinosaur from Mexico from the early Santonian age of the Late Cretaceous. It includes one species, Acantholipan gonzalezi.

Achillobator

Achillobator ( ə-KIL-ə-BAY-tor) is a dromaeosaurid theropod dinosaur that lived roughly 93 to 80 million years ago during the Late Cretaceous in what is now Mongolia, in Asia. It was among the largest dromaeosaurs; the holotype and only known individual of Achillobator is estimated at 5 to 6 m (16.4 to 19.7 ft) long. Achillobator was a moderately-built, ground-dwelling, bipedal carnivore. It would have been an active predator, hunting with the enlarged, sickle-shaped claw on the second toe.

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.

Bienosaurus

Bienosaurus (meaning "Bien's lizard") is a genus of thyreophoran dinosaur from the Lower Jurassic (probably Sinemurian) Lower Lufeng Formation in Yunnan Province in China.

Bissektipelta

Bissektipelta is a genus of herbivorous ankylosaurid dinosaur from the Upper Cretaceous of Uzbekistan. Bissektipelta is monospecific, containing only the species B. archibaldi.

Evgeny Maleev

Evgeny/Evgenii Aleksandrovich Maleev [1] (Russian: Евгений Александрович Малеев, pronounced [jɪˈvɡenʲɪj ɐlʲɪˈksandrəvʲɪtɕ mɐˈlʲeɪf]; 25 February 1915 – 12 April 1966) was a Soviet paleontologist who named the ankylosaur Talarurus; the theropods Tarbosaurus and Therizinosaurus; and the family Therizinosauridae.

Maleev did research on Tarbosaurus brains by cutting open fossilized braincases with a diamond saw. Modern researchers use computer tomography scans and 3D reconstruction software to visualize the interior of dinosaur endocrania, thus eliminating the need to damage valuable specimens.Two dinosaurs — Maleevus and Maleevosaurus — have been named for Maleev.

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.

Mongolostegus

Mongolostegus is a genus of stegosaur from the Early Cretaceous (Aptian-Albian) of Mongolia. The type and only species is M. exspectabilis, known from a single specimen previously under the nomen nudum Wuerhosaurus mongoliensis.

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.

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.

Tarchia

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

Tatisaurus

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.

Texasetes

Texasetes (meaning "Texas resident") is a genus of ankylosaurian dinosaurs from the late Lower Cretaceous of North America. This poorly known genus has been recovered from the Paw Paw Formation (late Albian) near Haslet, Tarrant County, Texas, which has also produced the nodosaurid ankylosaur Pawpawsaurus. Texasetes is estimated to have been 2.5–3 m (8–10 ft) in length. It was named by Coombs in 1995.

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.

Tsagantegia

Tsagantegia (; meaning "of Tsagan-Teg"; Tumanova, 1993) is a genus of medium-sized ankylosaurid dinosaur from the Late Cretaceous of Mongolia, during the Cenomanian stage.

The holotype specimen (GI SPS N 700/17), a complete skull, was recovered from the Bayan Shireh Formation (Cenomanian-Santonian), at the Tsagan-Teg ("White Mountain") locality, Dzun-Bayan, in the southeastern Gobi Desert, Mongolia. The genus is monotypic, including only the type species, T. longicranialis.

Turonian

The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by the Cenomanian stage and underlies the Coniacian stage.At the beginning of the Turonian an anoxic event took place which is called the Cenomanian-Turonian boundary event or the "Bonarelli Event".

Zuul

Zuul is a genus of herbivorous ankylosaurine dinosaur from the Campanian Judith River Formation of Montana. The type species is Zuul crurivastator. It is known from a complete skull and tail, which represents the first ankylosaurin known from a complete skull and tail club, as well as the most complete ankylosaurid specimen thus far recovered from North America. The specimen also preserved in situ osteoderms, keratin, and skin remains.

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