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Minotaurasaurus

January 01, 1970

Minotaurasaurus (meaning “Minos'-bull reptile”) is a monospecific genus of ankylosaurid dinosaur that lived in Mongolia during the Late Cretaceous (late Campanian stage, ~75-71 Ma) in what is now the Djadochta Formation. The type and only species, Minotaurasaurus ramachandrani, is known from two skulls, a cervical vertebra and a cervical half ring. It was named and described in 2009 by Clifford Miles and Clark Miles. The first fossils of Minotaurasaurus were illegally exported out of Mongolia.[citation needed]It has been suggested to be a synonym of Tarchia but more recent publications consider it as a distinct genus.

Minotaurasaurus
Temporal range: Late Cretaceous, 75–71 Ma
↓
Cast of the holotype skull of Minotaurasaurus.
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: †Ornithischia
Clade: †Thyreophora
Clade: †Ankylosauria
Family: †Ankylosauridae
Subfamily: †Ankylosaurinae
Genus: †Minotaurasaurus
Miles & Miles, 2009
Species:
†M. ramachandrani
Binomial name
†Minotaurasaurus ramachandrani
Miles & Miles, 2009

Minotaurasaurus was a medium-sized ankylosaurid, with an estimated length of 4.2 metres (13.8 feet), although it may have reached larger sizes as the type specimen represents an immature individual. Although not a lot of postcranial material is known, it would have had a tail club that may have been used for protection against predators or interspecific combat and would have been covered in protective osteoderms. It would have also had a barrel-like body, and short, robust limbs based on close relatives.

Discovery and Naming edit

 
Fossil localities in Mongolia. Minotaurasaurus fossils have been collected at Uhkaa Tolgod (area B)

In 2003, a skull of an ankylosaurid was purchased for US$10,000 by the private fossil collector and neuroscientist Vilayanur S. Ramachandran while accompanied by Clifford Miles at the Tucson Gem, Mineral and Fossil Showcase, Arizona. The skull was put on display by Robert Gaston for the fossil poacher Hollis Butts, who Ramachandran purchased it from[citation needed]. The stratigraphic position was stated as being from the Gobi Desert of either Mongolia or China due to the provenance being unknown at the time. In 2006, Clifford Miles and his brother Clark Miles attempted to publish the description of the skull in a Polish Journal but was promptly rejected as the specimen was seemingly obtained illegally from Mongolia. Two years later, the authors stated that the specimen had come from the Barun Goyot Formation but later stated that they could not confirm its origin. The skull would later be described and named in 2009. The publication was later criticised by palaeontologists such as Mark Norell, Phillip J. Currie and Bolortsetseg Minjin due to the questionable origins of the specimen.[1] The holotype specimen, INBR21004, consists of a skull with lower jaws and predentary. The type specimen is currently housed at the Victor Valley Museum in Apple Valley, California.[2]

The generic name, Minotaurasaurus, is derived from the Minotaur and the Greek word "sauros" (lizard), in reference to the bull-like appearance of the holotype skull. The specific name, ramachandrani, honours V. S. Ramachandran, who purchased the type specimen.[2]

In 2013, a Society of Vertebrate Paleontology abstract book mentioned the discovery of a second specimen of Minotaurasaurus (MAE 98 179) from the Uhkaa Tolgod locality of the late Campanian Djadochta Formation in the Nemegt Basin. The specimen consists of a skull, axis and first cervical half-ring, and it is part of the collection of the Mongolian Academy of Sciences. MAE 98 179 was reported as having insect burrows that continues into a pattern which is only seen in Late Cretaceous Gobi deposits.[3] Penkalski & Tumanova (2016) would later describe the specimen, which was used to establish the stratigraphic position of the type specimen and the validity of the taxon, as before it was suggested by Arbour et al. (2014) and Arbour & Currie (2015) to be from the Barun Goyot Formation and a junior synonym of Tarchia kielanae.[4][5][6] Its validity was also tested by Arbour & Currie (2012) by using a retrodeformation and finite element analysis, which found that many of its diagnostic features were likely not caused by deformation.[7]

Description edit

Size and distinguishing traits edit

 
Diagram of the holotype skull

Miles & Miles (2009) gave Minotaurasaurus an estimated length of at least 4.2 metres (13.8 feet), although it may have attained larger sizes as the type specimen, and only known specimen at the time, represents an immature individual based on the unfused osteoderms.[2]

Penkalski & Tumanova (2016) established numerous distinguishing traits of Minotaurasaurus. The paroccipital processes are not present laterally to the squamosal horns due to presence of a small and dorsoventrally shallow occiput. The skull roof possessing an unfused occiput. Basioccipital foramen that are either small or absent. Highly sculptured squamosal horns that are dorsoventrally narrow and cylindrical in shape. Non prominent nuchal caputegulae that angle caudolaterally. The presence of two distinct supraorbital apices. Frontal caputegulae that aren't arranged at right angles but with nasofrontal caputegulae that are elongated transversely and are ridge-like. The presence of a deep notch in the lacrimal. The presence of two pairs of internarial osteoderms, unlike the presence of a single osteoderm as in Tarchia and Saichania. An overall small skull that is broad. A more horizontal pterygoid body. A mandibular osteoderm that extends towards the front end of the tooth row. Other distinguishing traits include the occiput being more visible in dorsal view, an occipital condyle that is protrudes less towards the underside in caudal view and a skull that is proportionally lower and wider than that of Tarchia.[4]

Skull edit

 
Skull of Minotaurasaurus (far right) compared to other ankylosaurids

The holotype skull measures 30 centimetres (11.8 inches) long and has a width of 43 centimetres (17 inches). Excluding the squamosal horns, the skull is longer than wide. The skull roof has its widest point formed by the squamosal horns. Unlike other ankylosaurids, the squamosal horns are more gracile and tapering. Pyramid-shaped caputegulae cover most of the surface of the skull, with the exception of an area of the skull roof that is near the orbits. The caputegulae are arranged roughly bi-symmetrically on the skull, with two sharp-keeled caputegulae projecting laterally above the orbits and similar caputegulae being present near the prefrontal. Partially fused to unfused caputegulae are present on parts of the skull.[2] Present near the squamosal horn is a furrow, or unfused caputegulum, that is also seen in Tarchia kielanae. The furrow is an artefact of the postorbital osteoderm being within the postorbital fossa. However, unlike Tarchia, the supraoccipital is co-ossified to the parietals.[4] The skull's orbit is tear drop-shaped with a tapered end that points towards the front. The osteoderms of the narial region create a flared look due to how large and ornamented they are, and project towards the front and sides. Present in the narial region are three apertures and the external nasal cavity, which is bound by a single osteoderm. The surface of the premaxillary beak is covered partially by secondary dermal ossifications. An inverted, triangular osteoderm is coossified to the premaxilla along the ventral margin of the narial opening. A sharp premaxillary beak is present as a result of the palatal portions of the premaxillae changing shape from the front end to the back end. Unlike most ankylosaurids, the vomer extends below the maxillary tooth crowns. All teeth are leaf-shaped. There are a total of 17 teeth and alveoli in the left maxilla and 16 in the right maxilla. The maxillary teeth are up to 25% larger than the dentary teeth and have crowns that are variable.[2]

The epipterygoid, a small, triangular structure, separates the pterygoid from the maxilla. Instead of being vertical or even slightly overturned as seen in most ankylosaurids, the main body of the pterygoids is near horizontal which, as a result, makes the interpterygoid vacuity in palatal view. The occipital condyle lacks a neck and is heart-shaped. The occiput is low and rectangular in shape. The paroccipital processes fall well short of the medial edge of the squamosal horn. Both the basisphenoid and basioccipital are fused together, with the sutural area being expanded as a ridge. This ridge marks the insertion for the rectus capitis and longus capitis muscles. Both the left and right jugal horns thrust more towards the sides than towards the underside. Towards the sides of the tooth row is a broad maxillary shelf that extends beneath the middle of the orbit. A long, narrow osteoderm is partially fused along each side of the mandible but does not extend dorsally onto the lateral surface. The tooth row is positioned along the margins of the dentary. The ventral half of the mandible has a rough texture on the lateral surface, while the dorsal half of the mandible has a smooth texture. The position of the cheeks on the lower jaws is marked by the boundary between the smooth and the textured surfaces during occlusion as it is opposite to the lateral edge of the maxillary shelf. The coronoid process is small and low, and is present towards the front of the base of the process. The predentary is subtriangular in cross-section and bears numerous nutrient foramina to serve the rhamphotheca on the dorsal surface. The left dentary preserves 15 teeth and alveoli in the left dentary and 16 in the right dentary.[2]

Classification edit

 
Type specimen of Tarchia teresae, a taxon closely related to Minotaurasaurus

Miles & Miles (2009) interpreted Minotaurasaurus as an ankylosaurid, but did not conduct a phylogenetic analysis.[2] A phylogenetic analysis performed by Thomas et al. (2012) recovered it as sister taxon to Pinacosaurus grangeri, a position also recovered by Han et al. (2014).[8][9] Arbour et al. (2014) considered Minotaurasaurus as a junior synonym of Tarchia kielanae due to the shared presence of a furrow near the squamosal horn, a conclusion also met by Arbour & Currie (2015).[5][6] However, Penkalski & Tumanova (2016) noted that it differs from Tarchia by a number of characteristics, such as differences in the squamosal horns and caputegulae, and stated that it should therefore be considered as a valid taxon. Penkalski & Tumanova (2016) also conducted a phylogenetic analysis which found Minotaurasaurus as being at the base of a clade containing Zaraapelta, Saichania and Tarchia.[4] Park et al. (2021) also had similar results to Penkalski & Tumanova (2016), while Wiersma & Irmis (2018) recovered it within a polytomy with Tarchia kielanae and Shanxia.[10][11]

A limited phylogenetic analysis conducted Penkalski & Tumanova (2016) is reproduced below.[4]

The results of an earlier analysis by Thompson et al. (2012) are reproduced below.[8]

Paleobiology edit

Feeding edit

 
Snout morphology and diet of Mongolian ankylosaurids; M. ramachandrani in left

Minotaurasaurus was, like other Mongolian ankylosaurines, herbivorous and a low-level bulk feeder based on its sub-rectangular broad muzzle.[10] Instead of oral processing, ankylosaurids living in dry environments such as Minotaurasaurus may have relied more on hindgut fermentation for digestion or, alternatively, consumed succulent plants that did not require complex chewing. These ankylosaurids may have also been restricted to simple orthal pulping and might have had to deal with more grit during feeding compared to ankylosaurs that lived in tropical to subtropical climates, as indicated by the microwear pits.[12] Park et al. (2021) suggested that there was a shift from bulk feeding to selective feeding in Mongolian ankylosaurines during the Campanian and Maastrichtian stages which may have either been caused by the change in habitat, as the climate changed from semi-arid and arid to humid, or interspecific competition with saurolophine hadrosaurids that immigrated from North America to Central Asia during the Campanian stage.[10]

The type specimen of Minotaurasaurus may have had a pair of small osteoderms below the orbits that were homologous to the posterior cheek plates of nodosaurids such as Panoplosaurus and Edmontonia. The presence of these osteoderms at the level of the last three maxillary teeth suggests that either the bucca did not extend as anteriorly as in Panoplosaurus and Edmontonia or an anteriorly extended bucca was present but did not embed extensive cheek plates.[12]

Paleoenvironment edit

 
Restoration of Minotaurasaurus in paleoenvironment

The remains of Minotaurasaurus were likely recovered from the Ukhaa Tolgod locality at the Djadochta Formation.[3][4] The formation is divided into two members, the lower Bayn Dzak Member and the upper Turgrugyin Member. The Bayn Dzak Member consists of moderate reddish orange, crossbedded, and structureless sandstones, with subordinate deposits of brown siltstone and mudstone. The mudstone and siltstone represents an interdune facies deposited by fluvial action, while the crossbedded and structureless sandstones represent eolian dunes and fluvial deposits or sandslides that occurred on the dune faces. The Turgrugyin Member consists of very pale orange to light gray sands, which also represents a crossbedded dune facies and a structureless sandslide facies. Magnetostratigraphic datings from the Bayn Dzak and Tugriken Shireh localities suggest that the formation dates to the late Campanian stage of the Late Cretaceous, ca. ~75-71 Ma.[13] Based on the strata, rock facies, sedimentation and coeval units, the Djadochta Formation represents an arid environment consisting of sand dunes and short-lived water bodies with a warm, semiarid climate.[14]

Specimens of Minotaurasaurus likely originated from the lower Bayn Dzak Member of the Djadochta Formation, which have also yielded specimens of the dromaeosaurids Velociraptor mongoliensis and Tsaagan;[15][16] the halszkaraptorine Halszkaraptor;[17] the troodontids Byronosaurus and Saurornithoides;[18][19] the oviraptorids Citipati, Oviraptor and Khaan;[20][21] the alvarezsaurid Shuvuuia;[22] the ankylosaurid Pinacosaurus grangeri;[23] the ceratopsian Protoceratops;[24] an indeterminate hadrosauroid;[25] and an indeterminate azhdarchid.[26] The upper Turgrugyin Member has yielded the dromaeosaurid Velociraptor mongoliensis;[15] the halszkaraptorine Mahakala;[27] the ornithomimosaurs Aepyornithomimus and an indeterminate ornithomimosaur;[28][29][30] the oviraptorosaur Avimimus;[31] the ceratopsians Protoceratops and Udanoceratops;[32][33] and an indeterminate tyrannosaurid.[34]

References edit

  1. ^ Rex Dalton (2 February 2009). "Paper sparks fossil fury". Nature. Retrieved 27 June 2011.
  2. ^ a b c d e f g Miles, Clifford A.; Miles, Clark J. (2009). "Skull of Minotaurasaurus ramachandrani, a new Cretaceous ankylosaur from the Gobi Desert" (PDF). Current Science. 96 (1): 65–70.
  3. ^ a b Alicea, Justy; Loewen, Mark (2013). "New Minotaurasaurus material from the Djodokta Formation establishes new taxonomic and stratigraphic criteria for the taxon" (PDF). Journal of Vertebrate Paleontology. 33: 76.
  4. ^ a b c d e f Penkalski, P.; Tumanova, T. (2017). "The cranial morphology and taxonomic status of Tarchia (Dinosauria: Ankylosauridae) from the Upper Cretaceous of Mongolia". Cretaceous Research. 70: 117–12. doi:10.1016/j.cretres.2016.10.004.
  5. ^ a b Arbour, V.M.; Currie, P.J.; Badamgarav, D. (2014). "The ankylosaurid dinosaurs of the Upper Cretaceous Baruungoyot and Nemegt formations of Mongolia". Zoological Journal of the Linnean Society. 172 (3): 631–652. doi:10.1111/zoj.12185.
  6. ^ a b 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. S2CID 214625754.
  7. ^ Arbour, V. M.; Currie, P. J. (2012). Dodson, Peter (ed.). "Analyzing Taphonomic Deformation of Ankylosaur Skulls Using Retrodeformation and Finite Element Analysis". PLOS ONE. 7 (6): e39323. doi:10.1371/journal.pone.0039323. PMC 3382236. PMID 22761763.
  8. ^ a b Richard S. Thompson, Jolyon C. Parish, Susannah C. R. Maidment and Paul M. Barrett, 2012, "Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)", Journal of Systematic Palaeontology 10(2): 301–312
  9. ^ Han, F.; Zheng, W.; Hu, D.; Xu, X.; Barrett, P.M. (2014). "A New Basal Ankylosaurid (Dinosauria: Ornithischia) from the Lower Cretaceous Jiufotang Formation of Liaoning Province, China". PLOS ONE. 9 (8): e104551. Bibcode:2014PLoSO...9j4551H. doi:10.1371/journal.pone.0104551. PMC 4131922. PMID 25118986.
  10. ^ a b c Park JY, Lee YN, Kobayashi Y, Jacobs LL, Barsbold R, Lee HJ, Kim N, Song KY, Polcyn MJ (2021). "A new ankylosaurid from the Upper Cretaceous Nemegt Formation of Mongolia and implications for paleoecology of armoured dinosaurs". Scientific Reports. 11 (1): Article number 22928. doi:10.1038/s41598-021-02273-4. PMC 8616956. PMID 34824329.
  11. ^ Jelle P. Wiersma; Randall B. Irmis (2018). "A new southern Laramidian ankylosaurid, Akainacephalus johnsoni gen. et sp. nov., from the upper Campanian Kaiparowits Formation of southern Utah, USA". PeerJ. 6: e5016. doi:10.7717/peerj.5016. PMC 6063217. PMID 30065856.
  12. ^ a b Ősi, Attila; Prondvai, Edina; Mallon, Jordan; Bodor, Emese Réka (2016-07-20). "Diversity and convergences in the evolution of feeding adaptations in ankylosaurs (Dinosauria: Ornithischia)". Historical Biology. 29 (4): 539–570. doi:10.1080/08912963.2016.1208194. ISSN 0891-2963. S2CID 55372674.
  13. ^ Dashzeveg, D.; Dingus, L.; Loope, D. B.; Swisher III, C. C.; Dulam, T.; Sweeney, M. R. (2005). "New Stratigraphic Subdivision, Depositional Environment, and Age Estimate for the Upper Cretaceous Djadokhta Formation, Southern Ulan Nur Basin, Mongolia" (PDF). American Museum Novitates (3498): 1−31. doi:10.1206/0003-0082(2005)498[0001:NSSDEA]2.0.CO;2. hdl:2246/5667. S2CID 55836458.
  14. ^ Dingus, L.; Loope, D. B.; Dashzeveg, D.; Swisher III, C. C.; Minjin, C.; Novacek, M. J.; Norell, M. A. (2008). "The Geology of Ukhaa Tolgod (Djadokhta Formation, Upper Cretaceous, Nemegt Basin, Mongolia)" (PDF). American Museum Novitates (3616): 1−40. doi:10.1206/442.1. hdl:2246/5916. S2CID 129735494.
  15. ^ a b Norell, M. A.; Makovicky, P. J. (1999). "Important Features of the Dromaeosaurid Skeleton II: Information from Newly Collected Specimens of Velociraptor mongoliensis". American Museum Novitates (3282): 1−45. hdl:2246/3025. OCLC 802169086.
  16. ^ Norell, M. A.; Clark, J. M.; Turner, A. H.; Makovicky, P. J.; Barsbold, R.; Rowe, T. (2006). "A New Dromaeosaurid Theropod from Ukhaa Tolgod (Ömnögov, Mongolia)". American Museum Novitates (3545): 1–51. doi:10.1206/0003-0082(2006)3545[1:ANDTFU]2.0.CO;2. hdl:2246/5823.
  17. ^ Cau, A.; Beyrand, V.; Voeten, D. F. A. E.; Fernandez, V.; Tafforeau, P.; Stein, K.; Barsbold, R.; Tsogtbaatar, K.; Currie, P. J.; Godefroit, P. (2017). "Synchrotron scanning reveals amphibious ecomorphology in a new clade of bird-like dinosaurs". Nature. 552 (7685): 395−399. Bibcode:2017Natur.552..395C. doi:10.1038/nature24679. PMID 29211712. S2CID 4471941.
  18. ^ Norell, M.A., Makovicky, P.J. & Clark, J.M., 2000, "A new troodontid theropod from Ukhaa Tolgod, Mongolia", Journal of Vertebrate Paleontology 20(1): 7-11
  19. ^ Norell, M. A.; Makovicky, P. J.; Bever, G. S.; Balanoff, A. M.; Clark, J. M.; Barsbold, R.; Rowe, T. (2009). "A review of the Mongolian Cretaceous dinosaur Saurornithoides (Troodontidae, Theropoda)". American Museum Novitates (3654): 1−63. doi:10.1206/648.1. hdl:2246/5973.
  20. ^ Clark, J. M.; Norell, M. A.; Barsbold, R. (2001). "Two new oviraptorids (Theropoda: Oviraptorosauria) from the Late Cretaceous Djadokta Formation, Ukhaa Tolgod". Journal of Vertebrate Paleontology. 21 (2): 209–213. doi:10.1671/0272-4634(2001)021[0209:TNOTOU]2.0.CO;2. JSTOR 20061948. S2CID 86076568.
  21. ^ Osborn, H. F. (1924). "Three new Theropoda, Protoceratops zone, central Mongolia". American Museum Novitates (144): 1−12. hdl:2246/3223. OCLC 40272928.
  22. ^ Chiappe, L.M., Norell, M. A., and Clark, J. M. (1998). "The skull of a relative of the stem-group bird Mononykus." Nature, 392(6673): 275-278.
  23. ^ Gilmore, C. W. (1933). "Two new dinosaurian reptiles from Mongolia with notes on some fragmentary specimens". American Museum Novitates (679): 1–20. hdl:2246/2076.
  24. ^ Brown, B.; Schlaikjer, E. M. (1940). "The Structure and Relationships of Protoceratops". Annals of the New York Academy of Sciences. 40 (3): 133−266. Bibcode:1940NYASA..40..133B. doi:10.1111/j.2164-0947.1940.tb00068.x. OCLC 1673730.
  25. ^ Barsbold, R.; Perle, A. (1983). "On taphonomy of joint burial of juvenile dinosaurs and some aspects of their ecology". Transactions of the Joint Soviet-Mongolian Paleontological Expedition (in Russian). 24: 121−125.
  26. ^ Hone, D.; Tsuihiji, T.; Watabe, M.; Tsogtbaatr, K. (2012). "Pterosaurs as a food source for small dromaeosaurs". Palaeogeography, Palaeoclimatology, Palaeoecology. 331–332: 27. Bibcode:2012PPP...331...27H. doi:10.1016/j.palaeo.2012.02.021.
  27. ^ Turner, A. H.; Pol, D.; Clarke, J. A.; Erickson, G. M.; Norell, M. A. (2007). "A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight". Science. 317 (5843): 1378−1381. Bibcode:2007Sci...317.1378T. doi:10.1126/science.1144066. PMID 17823350.
  28. ^ Chinzorig, T.; Kobayashi, Y.; Tsogtbaatar, K.; Currie, P. J.; Watabe, M.; Barsbold, R. (2017). "First Ornithomimid (Theropoda, Ornithomimosauria) from the Upper Cretaceous Djadokhta Formation of Tögrögiin Shiree, Mongolia". Scientific Reports. 7 (5835): 5835. Bibcode:2017NatSR...7.5835C. doi:10.1038/s41598-017-05272-6. PMC 5517598. PMID 28724887.
  29. ^ Makovicky, P. J.; Norell, Mark A. (1998). "A partial ornithomimid briancase from Ukhaa Tolgod (Upper Cretaceous, Mongolia)". American Museum Novitates (3247): 1–16.
  30. ^ Ksepka, Daniel T.; Norell, Mark A. (2004). "Ornithomimosauria cranial material from Ukhaa Tolgod (Omnogov, Mongolia)". American Museum Novitates (3448): 1–4. doi:10.1206/0003-0082(2004)448<0001:ocmfut>2.0.co;2. hdl:2246/2813. ISSN 0003-0082. S2CID 55019144.
  31. ^ Kurzanov, S. M. (1981). "An unusual theropod from the Upper Cretaceous of Mongolia". Transactions, Joint Soviet–Mongolian Palaeontological Expedition (in Russian). 15: 39−49.
  32. ^ Chiba, K.; Ryan, M. J.; Saneyoshi, M.; Konishi, S.; Yamamoto, Y.; Mainbayar, B.; Tsogtbaatar, K. (2020). "Taxonomic re-evaluation of Protoceratops (Dinosauria: Ceratopsia) specimens from Udyn Sayr, Mongolia" (PDF). Journal of Vertebrate Paleontology. Program and Abstracts.
  33. ^ Kurzanov, S. M. (1992). "A giant protoceratopsid from the Upper Cretaceous of Mongolia". Paleontological Journal (in Russian): 81−93.
  34. ^ Longrich, N. R.; Currie, P. J.; Dong, Z. (2010). "A new oviraptorid (Dinosauria: Theropoda) from the Upper Cretaceous of Bayan Mandahu, Inner Mongolia". Palaeontology. 53 (5): 945−960. doi:10.1111/j.1475-4983.2010.00968.x.

See also edit

January 01, 1970
minotaurasaurus, meaning, minos, bull, reptile, monospecific, genus, ankylosaurid, dinosaur, that, lived, mongolia, during, late, cretaceous, late, campanian, stage, what, djadochta, formation, type, only, species, ramachandrani, known, from, skulls, cervical,. Minotaurasaurus meaning Minos bull reptile is a monospecific genus of ankylosaurid dinosaur that lived in Mongolia during the Late Cretaceous late Campanian stage 75 71 Ma in what is now the Djadochta Formation The type and only species Minotaurasaurus ramachandrani is known from two skulls a cervical vertebra and a cervical half ring It was named and described in 2009 by Clifford Miles and Clark Miles The first fossils of Minotaurasaurus were illegally exported out of Mongolia citation needed It has been suggested to be a synonym of Tarchia but more recent publications consider it as a distinct genus MinotaurasaurusTemporal range Late Cretaceous 75 71 Ma PreꞒ Ꞓ O S D C P T J K Pg N Cast of the holotype skull of Minotaurasaurus Scientific classification Domain Eukaryota Kingdom Animalia Phylum Chordata Clade Dinosauria Clade Ornithischia Clade Thyreophora Clade Ankylosauria Family Ankylosauridae Subfamily Ankylosaurinae Genus MinotaurasaurusMiles amp Miles 2009 Species M ramachandrani Binomial name Minotaurasaurus ramachandraniMiles amp Miles 2009 Minotaurasaurus was a medium sized ankylosaurid with an estimated length of 4 2 metres 13 8 feet although it may have reached larger sizes as the type specimen represents an immature individual Although not a lot of postcranial material is known it would have had a tail club that may have been used for protection against predators or interspecific combat and would have been covered in protective osteoderms It would have also had a barrel like body and short robust limbs based on close relatives Contents 1 Discovery and Naming 2 Description 2 1 Size and distinguishing traits 2 2 Skull 3 Classification 4 Paleobiology 4 1 Feeding 5 Paleoenvironment 6 References 7 See alsoDiscovery and Naming edit nbsp Fossil localities in Mongolia Minotaurasaurus fossils have been collected at Uhkaa Tolgod area B In 2003 a skull of an ankylosaurid was purchased for US 10 000 by the private fossil collector and neuroscientist Vilayanur S Ramachandran while accompanied by Clifford Miles at the Tucson Gem Mineral and Fossil Showcase Arizona The skull was put on display by Robert Gaston for the fossil poacher Hollis Butts who Ramachandran purchased it from citation needed The stratigraphic position was stated as being from the Gobi Desert of either Mongolia or China due to the provenance being unknown at the time In 2006 Clifford Miles and his brother Clark Miles attempted to publish the description of the skull in a Polish Journal but was promptly rejected as the specimen was seemingly obtained illegally from Mongolia Two years later the authors stated that the specimen had come from the Barun Goyot Formation but later stated that they could not confirm its origin The skull would later be described and named in 2009 The publication was later criticised by palaeontologists such as Mark Norell Phillip J Currie and Bolortsetseg Minjin due to the questionable origins of the specimen 1 The holotype specimen INBR21004 consists of a skull with lower jaws and predentary The type specimen is currently housed at the Victor Valley Museum in Apple Valley California 2 The generic name Minotaurasaurus is derived from the Minotaur and the Greek word sauros lizard in reference to the bull like appearance of the holotype skull The specific name ramachandrani honours V S Ramachandran who purchased the type specimen 2 In 2013 a Society of Vertebrate Paleontology abstract book mentioned the discovery of a second specimen of Minotaurasaurus MAE 98 179 from the Uhkaa Tolgod locality of the late Campanian Djadochta Formation in the Nemegt Basin The specimen consists of a skull axis and first cervical half ring and it is part of the collection of the Mongolian Academy of Sciences MAE 98 179 was reported as having insect burrows that continues into a pattern which is only seen in Late Cretaceous Gobi deposits 3 Penkalski amp Tumanova 2016 would later describe the specimen which was used to establish the stratigraphic position of the type specimen and the validity of the taxon as before it was suggested by Arbour et al 2014 and Arbour amp Currie 2015 to be from the Barun Goyot Formation and a junior synonym of Tarchia kielanae 4 5 6 Its validity was also tested by Arbour amp Currie 2012 by using a retrodeformation and finite element analysis which found that many of its diagnostic features were likely not caused by deformation 7 Description editSize and distinguishing traits edit nbsp Diagram of the holotype skull Miles amp Miles 2009 gave Minotaurasaurus an estimated length of at least 4 2 metres 13 8 feet although it may have attained larger sizes as the type specimen and only known specimen at the time represents an immature individual based on the unfused osteoderms 2 Penkalski amp Tumanova 2016 established numerous distinguishing traits of Minotaurasaurus The paroccipital processes are not present laterally to the squamosal horns due to presence of a small and dorsoventrally shallow occiput The skull roof possessing an unfused occiput Basioccipital foramen that are either small or absent Highly sculptured squamosal horns that are dorsoventrally narrow and cylindrical in shape Non prominent nuchal caputegulae that angle caudolaterally The presence of two distinct supraorbital apices Frontal caputegulae that aren t arranged at right angles but with nasofrontal caputegulae that are elongated transversely and are ridge like The presence of a deep notch in the lacrimal The presence of two pairs of internarial osteoderms unlike the presence of a single osteoderm as in Tarchia and Saichania An overall small skull that is broad A more horizontal pterygoid body A mandibular osteoderm that extends towards the front end of the tooth row Other distinguishing traits include the occiput being more visible in dorsal view an occipital condyle that is protrudes less towards the underside in caudal view and a skull that is proportionally lower and wider than that of Tarchia 4 Skull edit nbsp Skull of Minotaurasaurus far right compared to other ankylosaurids The holotype skull measures 30 centimetres 11 8 inches long and has a width of 43 centimetres 17 inches Excluding the squamosal horns the skull is longer than wide The skull roof has its widest point formed by the squamosal horns Unlike other ankylosaurids the squamosal horns are more gracile and tapering Pyramid shaped caputegulae cover most of the surface of the skull with the exception of an area of the skull roof that is near the orbits The caputegulae are arranged roughly bi symmetrically on the skull with two sharp keeled caputegulae projecting laterally above the orbits and similar caputegulae being present near the prefrontal Partially fused to unfused caputegulae are present on parts of the skull 2 Present near the squamosal horn is a furrow or unfused caputegulum that is also seen in Tarchia kielanae The furrow is an artefact of the postorbital osteoderm being within the postorbital fossa However unlike Tarchia the supraoccipital is co ossified to the parietals 4 The skull s orbit is tear drop shaped with a tapered end that points towards the front The osteoderms of the narial region create a flared look due to how large and ornamented they are and project towards the front and sides Present in the narial region are three apertures and the external nasal cavity which is bound by a single osteoderm The surface of the premaxillary beak is covered partially by secondary dermal ossifications An inverted triangular osteoderm is coossified to the premaxilla along the ventral margin of the narial opening A sharp premaxillary beak is present as a result of the palatal portions of the premaxillae changing shape from the front end to the back end Unlike most ankylosaurids the vomer extends below the maxillary tooth crowns All teeth are leaf shaped There are a total of 17 teeth and alveoli in the left maxilla and 16 in the right maxilla The maxillary teeth are up to 25 larger than the dentary teeth and have crowns that are variable 2 The epipterygoid a small triangular structure separates the pterygoid from the maxilla Instead of being vertical or even slightly overturned as seen in most ankylosaurids the main body of the pterygoids is near horizontal which as a result makes the interpterygoid vacuity in palatal view The occipital condyle lacks a neck and is heart shaped The occiput is low and rectangular in shape The paroccipital processes fall well short of the medial edge of the squamosal horn Both the basisphenoid and basioccipital are fused together with the sutural area being expanded as a ridge This ridge marks the insertion for the rectus capitis and longus capitis muscles Both the left and right jugal horns thrust more towards the sides than towards the underside Towards the sides of the tooth row is a broad maxillary shelf that extends beneath the middle of the orbit A long narrow osteoderm is partially fused along each side of the mandible but does not extend dorsally onto the lateral surface The tooth row is positioned along the margins of the dentary The ventral half of the mandible has a rough texture on the lateral surface while the dorsal half of the mandible has a smooth texture The position of the cheeks on the lower jaws is marked by the boundary between the smooth and the textured surfaces during occlusion as it is opposite to the lateral edge of the maxillary shelf The coronoid process is small and low and is present towards the front of the base of the process The predentary is subtriangular in cross section and bears numerous nutrient foramina to serve the rhamphotheca on the dorsal surface The left dentary preserves 15 teeth and alveoli in the left dentary and 16 in the right dentary 2 Classification edit nbsp Type specimen of Tarchia teresae a taxon closely related to Minotaurasaurus Miles amp Miles 2009 interpreted Minotaurasaurus as an ankylosaurid but did not conduct a phylogenetic analysis 2 A phylogenetic analysis performed by Thomas et al 2012 recovered it as sister taxon to Pinacosaurus grangeri a position also recovered by Han et al 2014 8 9 Arbour et al 2014 considered Minotaurasaurus as a junior synonym of Tarchia kielanae due to the shared presence of a furrow near the squamosal horn a conclusion also met by Arbour amp Currie 2015 5 6 However Penkalski amp Tumanova 2016 noted that it differs from Tarchia by a number of characteristics such as differences in the squamosal horns and caputegulae and stated that it should therefore be considered as a valid taxon Penkalski amp Tumanova 2016 also conducted a phylogenetic analysis which found Minotaurasaurus as being at the base of a clade containing Zaraapelta Saichania and Tarchia 4 Park et al 2021 also had similar results to Penkalski amp Tumanova 2016 while Wiersma amp Irmis 2018 recovered it within a polytomy with Tarchia kielanae and Shanxia 10 11 A limited phylogenetic analysis conducted Penkalski amp Tumanova 2016 is reproduced below 4 Minotaurasaurus Zaraapelta Saichania T kielanae T teresae Pinacosaurus The results of an earlier analysis by Thompson et al 2012 are reproduced below 8 Huayangosaurus taibaii Stegosaurus armatus Nodosauridae Ankylosauridae Minmi paravertebra Liaoningosaurus paradoxus Cedarpelta bilbeyhallorum Gobisaurus domoculus Shamosaurus scutatus Zhongyuansaurus luoyangensis Tsagantegia longicranialis Shanxia tianzhensis Crichtonsaurus benxiensis Dyoplosaurus acutosquameus Pinacosaurus mephistocephalus Ankylosaurus magniventris Euoplocephalus tutus Minotaurasaurus ramachandrani Pinacosaurus grangeri Nodocephalosaurus kirtlandensis Talarurus plicatospineus Tianzhenosaurus youngi Saichania chulsanensis Tarchia giganteaPaleobiology editFeeding edit nbsp Snout morphology and diet of Mongolian ankylosaurids M ramachandrani in left Minotaurasaurus was like other Mongolian ankylosaurines herbivorous and a low level bulk feeder based on its sub rectangular broad muzzle 10 Instead of oral processing ankylosaurids living in dry environments such as Minotaurasaurus may have relied more on hindgut fermentation for digestion or alternatively consumed succulent plants that did not require complex chewing These ankylosaurids may have also been restricted to simple orthal pulping and might have had to deal with more grit during feeding compared to ankylosaurs that lived in tropical to subtropical climates as indicated by the microwear pits 12 Park et al 2021 suggested that there was a shift from bulk feeding to selective feeding in Mongolian ankylosaurines during the Campanian and Maastrichtian stages which may have either been caused by the change in habitat as the climate changed from semi arid and arid to humid or interspecific competition with saurolophine hadrosaurids that immigrated from North America to Central Asia during the Campanian stage 10 The type specimen of Minotaurasaurus may have had a pair of small osteoderms below the orbits that were homologous to the posterior cheek plates of nodosaurids such as Panoplosaurus and Edmontonia The presence of these osteoderms at the level of the last three maxillary teeth suggests that either the bucca did not extend as anteriorly as in Panoplosaurus and Edmontonia or an anteriorly extended bucca was present but did not embed extensive cheek plates 12 Paleoenvironment edit nbsp Restoration of Minotaurasaurus in paleoenvironment The remains of Minotaurasaurus were likely recovered from the Ukhaa Tolgod locality at the Djadochta Formation 3 4 The formation is divided into two members the lower Bayn Dzak Member and the upper Turgrugyin Member The Bayn Dzak Member consists of moderate reddish orange crossbedded and structureless sandstones with subordinate deposits of brown siltstone and mudstone The mudstone and siltstone represents an interdune facies deposited by fluvial action while the crossbedded and structureless sandstones represent eolian dunes and fluvial deposits or sandslides that occurred on the dune faces The Turgrugyin Member consists of very pale orange to light gray sands which also represents a crossbedded dune facies and a structureless sandslide facies Magnetostratigraphic datings from the Bayn Dzak and Tugriken Shireh localities suggest that the formation dates to the late Campanian stage of the Late Cretaceous ca 75 71 Ma 13 Based on the strata rock facies sedimentation and coeval units the Djadochta Formation represents an arid environment consisting of sand dunes and short lived water bodies with a warm semiarid climate 14 Specimens of Minotaurasaurus likely originated from the lower Bayn Dzak Member of the Djadochta Formation which have also yielded specimens of the dromaeosaurids Velociraptor mongoliensis and Tsaagan 15 16 the halszkaraptorine Halszkaraptor 17 the troodontids Byronosaurus and Saurornithoides 18 19 the oviraptorids Citipati Oviraptor and Khaan 20 21 the alvarezsaurid Shuvuuia 22 the ankylosaurid Pinacosaurus grangeri 23 the ceratopsian Protoceratops 24 an indeterminate hadrosauroid 25 and an indeterminate azhdarchid 26 The upper Turgrugyin Member has yielded the dromaeosaurid Velociraptor mongoliensis 15 the halszkaraptorine Mahakala 27 the ornithomimosaurs Aepyornithomimus and an indeterminate ornithomimosaur 28 29 30 the oviraptorosaur Avimimus 31 the ceratopsians Protoceratops and Udanoceratops 32 33 and an indeterminate tyrannosaurid 34 References edit Rex Dalton 2 February 2009 Paper sparks fossil fury Nature Retrieved 27 June 2011 a b c d e f g Miles Clifford A Miles Clark J 2009 Skull of Minotaurasaurus ramachandrani a new Cretaceous ankylosaur from the Gobi Desert PDF Current Science 96 1 65 70 a b Alicea Justy Loewen Mark 2013 New Minotaurasaurus material from the Djodokta Formation establishes new taxonomic and stratigraphic criteria for the taxon PDF Journal of Vertebrate Paleontology 33 76 a b c d e f Penkalski P Tumanova T 2017 The cranial morphology and taxonomic status of Tarchia Dinosauria Ankylosauridae from the Upper Cretaceous of Mongolia Cretaceous Research 70 117 12 doi 10 1016 j cretres 2016 10 004 a b Arbour V M Currie P J Badamgarav D 2014 The ankylosaurid dinosaurs of the Upper Cretaceous Baruungoyot and Nemegt formations of Mongolia Zoological Journal of the Linnean Society 172 3 631 652 doi 10 1111 zoj 12185 a b 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 S2CID 214625754 Arbour V M Currie P J 2012 Dodson Peter ed Analyzing Taphonomic Deformation of Ankylosaur Skulls Using Retrodeformation and Finite Element Analysis PLOS ONE 7 6 e39323 doi 10 1371 journal pone 0039323 PMC 3382236 PMID 22761763 a b Richard S Thompson Jolyon C Parish Susannah C R Maidment and Paul M Barrett 2012 Phylogeny of the ankylosaurian dinosaurs Ornithischia Thyreophora Journal of Systematic Palaeontology 10 2 301 312 Han F Zheng W Hu D Xu X Barrett P M 2014 A New Basal Ankylosaurid Dinosauria Ornithischia from the Lower Cretaceous Jiufotang Formation of Liaoning Province China PLOS ONE 9 8 e104551 Bibcode 2014PLoSO 9j4551H doi 10 1371 journal pone 0104551 PMC 4131922 PMID 25118986 a b c Park JY Lee YN Kobayashi Y Jacobs LL Barsbold R Lee HJ Kim N Song KY Polcyn MJ 2021 A new ankylosaurid from the Upper Cretaceous Nemegt Formation of Mongolia and implications for paleoecology of armoured dinosaurs Scientific Reports 11 1 Article number 22928 doi 10 1038 s41598 021 02273 4 PMC 8616956 PMID 34824329 Jelle P Wiersma Randall B Irmis 2018 A new southern Laramidian ankylosaurid Akainacephalus johnsoni gen et sp nov from the upper Campanian Kaiparowits Formation of southern Utah USA PeerJ 6 e5016 doi 10 7717 peerj 5016 PMC 6063217 PMID 30065856 a b Osi Attila Prondvai Edina Mallon Jordan Bodor Emese Reka 2016 07 20 Diversity and convergences in the evolution of feeding adaptations in ankylosaurs Dinosauria Ornithischia Historical Biology 29 4 539 570 doi 10 1080 08912963 2016 1208194 ISSN 0891 2963 S2CID 55372674 Dashzeveg D Dingus L Loope D B Swisher III C C Dulam T Sweeney M R 2005 New Stratigraphic Subdivision Depositional Environment and Age Estimate for the Upper Cretaceous Djadokhta Formation Southern Ulan Nur Basin Mongolia PDF American Museum Novitates 3498 1 31 doi 10 1206 0003 0082 2005 498 0001 NSSDEA 2 0 CO 2 hdl 2246 5667 S2CID 55836458 Dingus L Loope D B Dashzeveg D Swisher III C C Minjin C Novacek M J Norell M A 2008 The Geology of Ukhaa Tolgod Djadokhta Formation Upper Cretaceous Nemegt Basin Mongolia PDF American Museum Novitates 3616 1 40 doi 10 1206 442 1 hdl 2246 5916 S2CID 129735494 a b Norell M A Makovicky P J 1999 Important Features of the Dromaeosaurid Skeleton II Information from Newly Collected Specimens of Velociraptor mongoliensis American Museum Novitates 3282 1 45 hdl 2246 3025 OCLC 802169086 Norell M A Clark J M Turner A H Makovicky P J Barsbold R Rowe T 2006 A New Dromaeosaurid Theropod from Ukhaa Tolgod Omnogov Mongolia American Museum Novitates 3545 1 51 doi 10 1206 0003 0082 2006 3545 1 ANDTFU 2 0 CO 2 hdl 2246 5823 Cau A Beyrand V Voeten D F A E Fernandez V Tafforeau P Stein K Barsbold R Tsogtbaatar K Currie P J Godefroit P 2017 Synchrotron scanning reveals amphibious ecomorphology in a new clade of bird like dinosaurs Nature 552 7685 395 399 Bibcode 2017Natur 552 395C doi 10 1038 nature24679 PMID 29211712 S2CID 4471941 Norell M A Makovicky P J amp Clark J M 2000 A new troodontid theropod from Ukhaa Tolgod Mongolia Journal of Vertebrate Paleontology 20 1 7 11 Norell M A Makovicky P J Bever G S Balanoff A M Clark J M Barsbold R Rowe T 2009 A review of the Mongolian Cretaceous dinosaur Saurornithoides Troodontidae Theropoda American Museum Novitates 3654 1 63 doi 10 1206 648 1 hdl 2246 5973 Clark J M Norell M A Barsbold R 2001 Two new oviraptorids Theropoda Oviraptorosauria from the Late Cretaceous Djadokta Formation Ukhaa Tolgod Journal of Vertebrate Paleontology 21 2 209 213 doi 10 1671 0272 4634 2001 021 0209 TNOTOU 2 0 CO 2 JSTOR 20061948 S2CID 86076568 Osborn H F 1924 Three new Theropoda Protoceratops zone central Mongolia American Museum Novitates 144 1 12 hdl 2246 3223 OCLC 40272928 Chiappe L M Norell M A and Clark J M 1998 The skull of a relative of the stem group bird Mononykus Nature 392 6673 275 278 Gilmore C W 1933 Two new dinosaurian reptiles from Mongolia with notes on some fragmentary specimens American Museum Novitates 679 1 20 hdl 2246 2076 Brown B Schlaikjer E M 1940 The Structure and Relationships of Protoceratops Annals of the New York Academy of Sciences 40 3 133 266 Bibcode 1940NYASA 40 133B doi 10 1111 j 2164 0947 1940 tb00068 x OCLC 1673730 Barsbold R Perle A 1983 On taphonomy of joint burial of juvenile dinosaurs and some aspects of their ecology Transactions of the Joint Soviet Mongolian Paleontological Expedition in Russian 24 121 125 Hone D Tsuihiji T Watabe M Tsogtbaatr K 2012 Pterosaurs as a food source for small dromaeosaurs Palaeogeography Palaeoclimatology Palaeoecology 331 332 27 Bibcode 2012PPP 331 27H doi 10 1016 j palaeo 2012 02 021 Turner A H Pol D Clarke J A Erickson G M Norell M A 2007 A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight Science 317 5843 1378 1381 Bibcode 2007Sci 317 1378T doi 10 1126 science 1144066 PMID 17823350 Chinzorig T Kobayashi Y Tsogtbaatar K Currie P J Watabe M Barsbold R 2017 First Ornithomimid Theropoda Ornithomimosauria from the Upper Cretaceous Djadokhta Formation of Togrogiin Shiree Mongolia Scientific Reports 7 5835 5835 Bibcode 2017NatSR 7 5835C doi 10 1038 s41598 017 05272 6 PMC 5517598 PMID 28724887 Makovicky P J Norell Mark A 1998 A partial ornithomimid briancase from Ukhaa Tolgod Upper Cretaceous Mongolia American Museum Novitates 3247 1 16 Ksepka Daniel T Norell Mark A 2004 Ornithomimosauria cranial material from Ukhaa Tolgod Omnogov Mongolia American Museum Novitates 3448 1 4 doi 10 1206 0003 0082 2004 448 lt 0001 ocmfut gt 2 0 co 2 hdl 2246 2813 ISSN 0003 0082 S2CID 55019144 Kurzanov S M 1981 An unusual theropod from the Upper Cretaceous of Mongolia Transactions Joint Soviet Mongolian Palaeontological Expedition in Russian 15 39 49 Chiba K Ryan M J Saneyoshi M Konishi S Yamamoto Y Mainbayar B Tsogtbaatar K 2020 Taxonomic re evaluation of Protoceratops Dinosauria Ceratopsia specimens from Udyn Sayr Mongolia PDF Journal of Vertebrate Paleontology Program and Abstracts Kurzanov S M 1992 A giant protoceratopsid from the Upper Cretaceous of Mongolia Paleontological Journal in Russian 81 93 Longrich N R Currie P J Dong Z 2010 A new oviraptorid Dinosauria Theropoda from the Upper Cretaceous of Bayan Mandahu Inner Mongolia Palaeontology 53 5 945 960 doi 10 1111 j 1475 4983 2010 00968 x See also edit nbsp Dinosaurs portal Timeline of ankylosaur research Retrieved from https en wikipedia org w index php title Minotaurasaurus amp oldid 1211448687, wikipedia, wiki, book, books, library,

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