Ankylosaurus magniventris: A redescription of an iconic Cretaceous Dinosaur.

Ankylosaurus magniventris was the first Ankylosaurid Dinosaur discovered, and consequently the species that gave the group its name. It is also the largest known species in the group, and, having lived at the very end of the Cretaceous, the last. Despite this the species is much less well known than many less familiar members of the group, with no complete specimens known, only a small amount of fragmentary material. Due to this lack of complete specimens our view of this Dinosaur has changed significantly in the hundred and ten years since it was first described, as new specimens have revealed more about its anatomy.

In a paper published in the journal Facets on 12 October 2017, Victoria Arbour of the Department of Palaeobiology at the Royal Ontario Museum, and the Department of Ecology and Evolutionary Biology at the University of Toronto, and Jordan Mallon of Palaeobiology at the Canadian Museum of Nature, present a new review of Ankylosaurus magniventris, based upon new material that has become available since the last such review in 2014.

Skull of CMN 8880, an Ankylosaurus magniventris specimen described in 2004, in (A) dorsal, (B) ventral, (C) left lateral, and (D) right lateral views. The skull is well preserved on the dorsal and left lateral surfaces. The right lateral surface has caved inwards slightly, and the premaxillary beak is missing. Left lower jaw in (E) lateral and (F) medial view. (G) Dentary tooth in labial view. Arbour & Mallon (2017).

The skull of Ankylosaurus magniventris resemblles that of other Late Cretaceous Ankylosaurids such as Anodontosaurus, Euoplocephalus, Scolosaurus, Ziapelta, and Zuul, though it can be distinguished in a number of ways. It has a distinct keel on its anterior and posterior supraorbital caputegulae (skull elements, which is also seen in some other species, but which, uniquely, is continued onto its squamosal horn, 34-36 teeth in its upper jaw, these teeth being proportionately small compared to other Ankylosaur species and rather variable in size within the species.

Skulls of Ankylosaurus, Euoplocephalus, and Nodocephalosaurus, in left anterolateral view. In Euoplocephalus, the supranarial caputegulum is rugose and forms an arch over the anteriorly placed nasal vestibule. In Ankylosaurus, the nasal vestibule and external naris is roofed by the loreal caputegulum, and the supranarial caputegulum is small and flush with the premaxilla. The holotype of Nodocephalosaurus is poorly preserved in the premaxillary region, but the external nares are also posteriorly placed and may be partly roofed by a ridge-like loreal caputegulum; the supranarial caputegulum is also ridged and projects anteriorly. asca, anterior supraorbital caputegulum; frca, frontal caputegulum; laca, lacrimal caputegulum; loca, loreal caputegulum; mnca, median nasal caputegulum; msca, middle supraorbital caputegulum; mx, maxilla; nasca, nasal caputegulum; nar, external naris; nav, nasal vestibule; nuca, nuchal caputegulum; o, orbit; pmx, premaxilla; psca, posterior supraorbital caputegulum; q, quadrate; qjh, quadratojugal horn; snca, supranarial caputegulum; sqh, squamosal horn. Arbour & Mallon (2017).

All Ankylosaurs are known to have long, complex nasal passages, which presumably also implies a highly developed sense of smell. The external nares (nostril openings in the skull) of Ankylosaurus magniventris are larger than those of other Ankylosaur species, and set further back and higher, and further apart on the skull. Nostrils placed higher on the skull of a terrestrial vertebrate are often a sign of a return to an aquatic or semi-aquatic lifestyle, however nothing else about the anatomy of Ankylosaurus magniventris supports this idea. Such nostril placement is also associated with the development of a flexible proboscis in modern animals such as Elephants, Tapirs and Saiga Antelope, however there is no evidence for any such structure in Ankylosaurus magniventris, and it would seem rather at odds with the beak of the animal, which appears to be its primary food-processing structure, and the use of which would presumably be hampered by the presence of a fleshy proboscis. It has also been suggested that the widely spaced nostrils of the living Moose could provide that animal with a stereolfactory capability, though it has never been shown that Moose have such a sense, or what they do with it if they have it. Ankylosaurus magniventris could presumably also have had stereolfaction, though it is even harder to assess what the advantage of this might have been to a poorly understood Cretaceous Dinosaur than it is to a living Deer.

An alternative explanation for the presence of high-set nostrils is a lifestyle that involves frequent digging. In modern Mammal species such as Pigs, Aardvarks, and Armadillos this is associated with the development of a flesh snout with nostrils mounted on a terminal disk, which again is unlikely in Ankylosaurus magniventris. However this trait is also seen in burrowing animals such as Blind Snakes and Amphisbaenians, which have shovel-like snouts. It is not proposed that Ankylosaurus magniventris is likely to have been a burrowing animal, but it is possible that it used its beak for some digging activity, possibly to search for buried food such as roots or tubers.

All Ankylosaurs posses structures called cervical half rings, armoured structures composed of composed of an underlying band of non-osteodermal bone and an overlying set of six large osteoderms, which provided protection for the neck and shoulders. However the cervical half rings of Ankylosaurus magniventris have been interpreted as having been split into two portions, effectively forming 'quater-rings'. However re-examination of this material by Arbour and Mollon suggests that these structures in fact had an underlying bony band which has not peen preserves and would have held them together as a single structure.

The tail club of Ankylosaurus magniventris is known only from smaller specimens, and is compatible in size to those of other similarly sized Ankylosaur species. However if this is scaled up proportionally to the largest members of the species it would imply a tail club with a width of 120 cm, far in excess of anything seen in any other Ankylosaur. Arbour and Mallon suggest that this is unlikely, as such a structure would place unreasonable stress upon the bones of the tail, and that the club is likely to have been proportionately smaller in the biggest animals.

Partial tail clubs of (A) Anodontosaurus (AMNH 5245) and (B) Ankylosaurus (AMNH 5214) in dorsal view. maj, major knob osteoderm; min, minor knob osteoderm; ns, neural spine; prz, prezygapophysis. Arbour & Mallon (2017).

Reconstructions of Ankylosaurus magniventris have changed considerably since the species was first described, when the tail club was unknown, and the cervical half rings were thought to be associated with the pelvis. While the overall shape of the species is now generally accepted, but reconstructions of the size and mass of the largest specimens still vary considerably. Arbour and Mallon estimate that the largest members of the species may have reached eight meters in length and seven and a half tonnes in mass, comparable to a large male African Elephant. They note that this is toward the upper end of size estimations for the species (something Dinosaur palaeontologists need to be wary of, as there is always a temptation to be the discoverer of the biggest member of any group), however they feel that some smaller interpretations (the smallest estimate gives a mass of only 1.7 tonnes) are considerably less plausible for an animal of elephantine proportions.

Ankylosaurus magniventris as reconstructed by Brown & Kaisen (1908) (far left), Ford (2003) (centre left), Carpenter (2004) (centre right), and Arbour & Mallon (2017) (far right). Brown & Kaisen proposed an arrangement in which the osteoderms are closely spaced and relatively uniform, with pelvic osteoderms united in coossified bands. Ford (2003) provided more space between the osteoderms overall, included a tail club knob, and hypothesised that a pelvic shield was present. Carpenter (2004) suggested that the cervical armour was arranged in quarter rings. Arbour & Mallon suggest that the cervical armour was united into more typical half rings, and provide an updated osteoderm arrangement based on preserved osteoderms in AMNH 5214, AMNH 5895, and AMNH 5866, and comparisons with related species. Arbour & Mallon (2017).

An animal the size of Ankylosaurus magniventris is likely to have been capable of consuming impressive amounts of vegetation. However an estimate of the energy requirements of an ectothermic animal ('cold blooded animal dependent on external sources for body heat) this size suggests that it would have required only 6 kg per day of course Fern material, which seems remarkably low. Alternatively an endothermic animal ('warm blooded' animal capable of generating its own body heat) of the same size would have required about 60 kg per day of similar material. The most common interpretation of Dinosaur physiology today is that they had energy requirements somewhere in between those of modern ectotherms and endotherms, giving Ankylosaurus magniventris  a requirement of between 6 and 60 kg of course fern material. However, while the species had a long digestive tract, clearly capable of dealing with low quality plant-matter such as Ferns, its specialist mouth parts, with numerous small teeth packed into a strong beak, suggests that it may have had a more specialized diet, possibly including higher energy foods such as fruits, which would have lowered its overall consumption, though it would increased its foraging time.

Modern Elephants play a significant role in habitat shaping, congregating in large groups which strip bark from trees and often push them over, serving to maintain an open habitat. Ankylosaurs were similar in size to Elephants, and might be expected to have played a similar role in their ecosystems. However there is no evidence that adult Ankylosaurs congregated in groups, as all fossil specimens of these animals found have been solitary. Nor do they appear to have been capable of significantly damaging trees, as their mouthparts seem poorly adapted to stripping bark, and their centre of gravity would have been to low to easily knock trees over. This suggests that Ankylosaurs were not a major influence on the landscape in which they lived, a role that was probably played by the smaller (though still large) and more numerous, herd-forming Hadrosaurs.

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Borealopelta markmitchelli: An exceptionally well preserved Nodosaurid Ankylosaur from the Early Cretaceous of Alberta, Canada.

Ankylosaurs were large, herbivorous Ornithischian Dinosaurs known from the Jurassic and Cretaceous. They are noted for their exceptional armour, with heads and bodies covered with thick plates of bone, their limbs by large spines which project from these plates, and their possession of weapons on their tails, either large bony clubs (Ankylosaurids) or large spines (Nodosaurids). This combination of large size, heavy armour and lethal-looking weaponry is surprising, as modern Mammals of comparable size to Ankylosaurs (basically Hippopotamus, Rhinoceros and Elephants) are largely ignored by even the largest predators, and Ankylosaurs lived alongside a range of smaller, less heavily armoured, and (presumably) generally more palatable Dinosaurs. This has led to the suggestion that the heavy armour and weaponry of Ankylosaurs may have been used in intra-specific competition (probably over mates) rather than to deter predators.

In a paper published in the journal Current Biology on 3 August 2017, Caleb Brown and Donald Henderson of the Royal Tyrrell Museum of Palaeontology, Jakob Vinther of the School of Biological Sciences and School of Earth Sciences at the University of Bristol, Ian Fletcher of the School of Mechanical and Systems Engineering at Newcastle University, and Ainara Sistiaga, Jorsua Herrera and Roger Summons of the Department of Earth, Atmospheric and Planetary Sciences at the Massachusetts Institute of Technology, describe a new and exceptionally well preserved Nodosaurid Ankylosaur from the Early Cretaceous Clearwater Formation of Alberta, Canada.

The specimen is described as a new species and named Borealopelta markmitchelli, where 'Borealopelta' means 'Northern Shield' and 'markmitchelli' honours Mark Mitchell, who spent more than 7000 hours preserving the specimen. This specimen is three dimensionally preserved and articulated, and comprises the head, most of the trunk, the right forelimb, most of the left forelimb, the hip joint, a foot, as well as much of the bony exoskeleton, including the soft tissue which covered it.

Borealopelta markmitchelli, (top) anterodorsolateral view, (bottom) anterodorsal view. Scale bar is 10 cm. Brown et al. (2017).

This specimen was preserved in soft mud in an inshore-marine environment. These rocks have previously produced Plesiosaurs and Ichthyosaurs, but this is the first known Dinosaur. The specimen shows no sign of scavenging (which is surprising as the sediments in which it was preserved were bioturbated). The specimen appears to have released body fluids explosively and subsequently collapsed shortly after burial.

Schematic Line Drawing of Borealopelta markmitchelli, Illustrating Preservation of the Different Tissue Types (A) Schematic of complete specimen in dorsal view. (B and C) Skull in dorsal (B) and left lateral (C) views. (D) Close-up view of the neck, illustrating alternating cervical osteoderm bands (and preserved keratinous sheaths) and polygonal scales. (E) Close up view of flank illustrating lateral thoracic osteoderms (with keratinous coverings) and polygonal scales. (F) Close-up view of sacral shield counterpart illustrating osteoderms and scales. (G) Close-up view of antebrachium including osteoderms and keratinous coverings. (D’–G’) Interpretive line drawings of the corresponding panels (D)–(G). Scale bars in (B)–(G), 10 cm. Brown et al. (2017).

A number of spectrographic analyses techniques were used on the organic material covering the exoskeleton of Borealopelta markmitchelli, which revealed the presence of (amongst other things) significant amounts of benzothiazole, a derivative of pheomelanin, a pigment molecule found in melanosomes (dark pigment cells), with a deep reddish-brown colour.

Ambient and UV fluorescent photographs of preserved spine sheaths. Photographs and line drawings of cervical osteoderm sheath in dorsal view (A-D), and right lateral view and left parascapular spine (E-H). (A) Dorsal view of osteoderm under visible light. (B) Inset in visible light showing parallel light coloured longitudinal striae and subtle darker bands. (C) Inset showing strong ultraviolet fluorescence of light striae. (D) Interpretative line drawing of (B). (E) Left lateral view posterior cervical and anterior thoracic regions in cross-polarised light. (F) Ultraviolet fluorescence showing same view as (E). (G) Inset showing ultraviolet fluorescence of parascapular spine. (H) Interpretative line drawing of (G) showing area of fluorescence. Brown et al. (2017).

This pigment is  not evenly distributed, but rather suggests that the living Dinosaur was darker on its upper side and lighter below, a pattern called countershading, which provides camouflage to animals which have it. That an animal as large as Borealopelta markmitchelli (estimated to have had a mass of at least 1600 kg, similar in size to an Indian or White Rhinoceros) had camouflage is quite remarkable, as such patterns only appear when they provide an advantage which natural selection can favour, i.e. making the animal harder for a predator to spot or track. This suggests that evolutionary pressures were very different in the Mesozoic, with predators willing and able to hunt large, armoured, prey such as Ankylosaurs, which in turn supports the idea that the armour and weaponry was indeed used for defence against predators.

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Zuul crurivastator: A new and exceptionally well preserved Ankylosaur from the Late Cretaceous Judith River Formation of northern Montana.

The Ankylosaurids were large armoured Dinosaurs from the Cretaceous of Europe, Asia and North America. Their bodies were encased in heavy armour forming an effective shell and they had large bony clubs on the ends of their tails. They are believed to have been entirely herbivorous, and had beak-like mouths, occasionally with residual teeth. Despite the extensive armour of the Ankylosaurids, which gives them excellent preservational potential, complete skeletons of these Dinosaurs are rare, hampering our understanding of the group.

In a paper published in the journal Royal Society Open Science on 10 May 2017, Victoria Arbour and David Evans of the Department of Palaeobiology at the Royal Ontario Museum and the Department of Ecology and Evolutionary Biology at the University of Toronto, describe a new and exceptionally well preserved Ankylosaurid Dinosaur from the Late Cretaceous Judith River Formation of Hill County in Montana.

The Judith River Formation was laid down between 75 and 80 million years ago on what was then a coastal plain on the Bear Paw Sea coast of the island of Laramida, and is now northern Montana. It is roughly equivalent in age to the Oldman and Dinosaur Park formations of southern Alberta and the Two Medicine Formation of Montana. These strata have been excavated for Dinosaur remains since the early nineteenth century, though the majority of material produced from the Judith River Formation has been fragmentary in nature.

The new Dinosaur is named Zuul crurivastator, where 'Zuul' refers to 'Zuul the Gatekeeper' a monster in the 1984 film Ghostbusters, and 'crurivastator' means 'destroyer of shins' in Latin, in reference to the large tail-club of the specimen. The species is described from a single specimen located during the excavation of a Tyraosaurus specimen by a commercial fossil extraction company and later acquired by the Royal Ontario Museum. The specimen comprises two blocks recovered from the overturned above the Tyranosaurus specimen (i.e. material that was removed because it was above that specimen), one containing the head and torso and the other the tail.. The specimen had been exposed prior to discovery and was partially eroded away, nevertheless it appears to be fairly complete (it has not yet been completely extracted from the rock matrix) with an almost complete skull and some soft tissue preservation.

Well-preserved skull and jaws of Zuul crurivastator showing quality of preservation. Arbour & Evans (2017).

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A new species of Ankylosaurid Dinosaur from the Late Cretaceous of New Mexico.

Ankylosaurids were large, heavily armoured Ornithischian Dinosaurs, which appeared in the Early Cretaceous and persisted to the end of the period. They had bony shells comprised of fused osteoderms (bony plates that develop within the skin) that enclosed their torsos in a similar way to the shells of tortoises and turtles, but appear to have been more active, with limbs built for an upright stance and a large bony club on their tail, presumably used for defence against the large carnivores of the Cretaceous.

In a paper published in the journal PLoS One on 24 September 2014, Victoria Arbour and Michael Burns of the Department of Biological Sciences at the University of Alberta, Robert Sulivan, Spencer Lukas and Amanda Cantrell of the New Mexico Museum of Natural History and Science, Joshua Fry of the Department of Geosciences at Fort Hays State University and Thomas Suazo, also of the New Mexico Museum of Natural History and Science describe a new species of Ankylosaurid Dinosaur from the Late Cretaceous Kirtland Formation at Hunter Wash in San Juan County, New Mexico.

The new species is named Ziapelta sanjuanensis, where ‘Zia’ refers to the stylised sun on the flag of New Mexico (which is derived from the Zia sun symbol of the indigenous Zia people of the state) and ‘pelta’ means a small shield, in reference to the animals osteoderms, while ‘sanjuanensis’ means ‘from San Juan’.Ziapelta sanjuanensis is described from an largely complete skull plus two partial cervical vertebrae (neck bones) and some fragmentary osteoderms.

Ziapelta sanjuanensis, complete skull. (A) Dorsal view; (B) ventral view; (C) anterior view; (D) occipital view; and (E) left lateral view. Abbreviations: asca, anterior supraorbital caputegulum; bas, basioccipital; ch, choana; fm, foramen magnum; j, jugal; laca, lacrimal caputegulum;loca, loreal caputegulum; ltf, laterotemporal fenestra; mnca, median nasal caputegulum; nar, externalnaris; oc, occipital condyle; orb, orbit; pal, palatine; par, parietal; parocc, paroccipital process; pmx, premaxilla; psca, posterior supraorbital caputegulum; pt, pterygoid; q, quadrate; qj, quadratojugal; qjh, quadratojugal horn; snca, supranarial caputegulum; socc, supraoccipital; sqh, squamosal horn; tr, tooth row; v, vomer. Arbour et al. (2014).

Speculative life restoration of Ziapelta sanjuanensis. Sydney Mohr in Arbour et al. (2014).

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Nodosaurid teeth from the Early Cretaceous of southern England.

The Nodosaurids were a group of Ankylosaurid Dinosaurs that differed from other members of the group in having spines, rather than bony clubs, on the ends of their tails, and additional large spines on their...

A new species of Ankylosaurid Dinosaur from the Late Cretaceous of Montana.

The Ankylosaurids were large armoured Dinosaurs from the Cretaceous of Europe, Asia and North America...

New description of an Ankylosaurid Dinosaur from Mongolia.

The 1971 Polish-Mongolian Palaeontological Expedition to the Gobi Desert unearthed a great deal of dinosaurian material, including the partial skeleton of an...

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Nodosaurid teeth from the Early Cretaceous of southern England.

The Nodosaurids were a group of Ankylosaurid Dinosaurs that differed from other members of the group in having spines, rather than boney clubs, on the ends of their tails, and additional large spines on their shoulders. Most known Nodosaurids have been discovered in North America, but specimens are known from China, Antarctica and England.

In a provisional paper to be published in the journal Acta Palaeontologica Polonica and available online from 13 March 2013, William Blows of the Department of Applied Biological Sciences at City University London and Kerri Honeysett of Bexhill on Sea in East Sussex describe four Nodosaurid teeth from the Isle of Wight and Bexhill on Sea. 

These are distinctive enough to state that they are from a Nodosaurid, but are not assigned to species level, since none of the Nodosaurid specimens known from England has preserved teeth, making it impossible to assign the teeth with confidence to any previously described species, or to say with confidence that they belong to a new species.

The first specimen comes from a plant dedris bed within the the Sudmore Point Sandstone at Sudmore Point east of Brook Chine on the Isle of Wight. It is Barremian in age (between 125 and 129.4 million years old). The Sudmore Point Sandstone is interpreted as having formed on a flat floodplain, with the debris bed representing a flood event. It contains large amounts of disarticulated plant and animal remains. The tooth is nearly complete, comprising both the crown and root, with a total length of 17 mm, 6 mm of which is the crown. 

The Isle of Wight specimen in (A) labial(?) view, (B) distal view and (C) lingual(?) view. Scale bar is 4 mm. Blows and Honeysett (2013).

The other three teeth come from Ashdown Quarry at Bexhill on Sea, where they were located by David Brockhurst, a noted amateur palaeontologist employed at the quarry. They were located within a conglomerate within the Wadhurst Clay Formation, of Valanginian age, making them between 132.9 and 139.8 million years old. 

The first of these is a 20.5 mm tooth with both crown and root, the crown comprising 7 mm of the total. The second is a partial crown 5 mm in heigh, without any root. The third is a 17 mm tooth of which 5 mm is the crown and the remainder is the root; the crown of this tooth appears somewhat worn down.

The first Bexhill on Sea specimen, complete tooth in (A1) lingual(?) view and  (A2) labial(?) view. Blows and Honeysett (2013).

The second and third Bexhil on Sea specimens. Partial tooth in shown in opposite views (B1 and B2), and complete tooth in (C1) lingual(?) view, (C2) distal view, (C3) labial(?) view. Blows and Honeysett (2013).

See also A new species of Ankylosaurid Dinosaur from the Late Cretaceous of Montana, New description of an Ankylosaurid Dinosaur from Mongolia and The Ashdown Maniraptoran. 

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A new species of Ankylosaurid Dinosaur from the Late Cretaceous of Montana.

The Ankylosaurids were large armored Dinosaurs from the Cretaceous of Europe, Asia and North America. Their bodies were encased in heavy armor forming an effective shell and they had large bony clubs on the ends of their tails. They are believed to have been entirely herbivorous, and had beak-like mouths, occasionally with residual teeth.

In a preliminary paper published on the journal Acta Palaeontologica Polonica's website on 4 February 2013, Paul Penkalski of The Geology Museum in Madison Wisconsin describes a new species of Ankylosaurid from the Late Cretaceous Two Medicine Formation of northern Montana.

The new Dinosaur is named Oohkotokia horneri, where 'Oohkotokia' means 'child of stone' in latinized Blackfoot and 'horneri' honours Jack Horner, a distinguished palaeontologist and expert on the Dinosaurs of Montana. The species is described from two partial skulls, a partial pelvis, some forelimb and hindlimb elements and an osteoderm (bony plate formed within the skin).

Skull of Oohkotokia horneri in dorsal view with interpretive drawing. Penkalski (2013).

Skull of Oohkotokia horneri in ventral (A₁) and lateral (A₃) views with interpretive drawings (A₂ & A₄). Scale bar is 10 cm. Penkalski (2013).

Postcranial material of Oohkotokia horneri. (A) Partial cervical vertebra; well-preserved fourth or fifth free caudal in (B) distal and (C) left lateral view; (D) lateral plate in two views; (E) conical osteoderm; (F) oval, low-keeled osteoderm in external view; (G) partial scapula; (H) stereo pair of two osteoderms; (I) opposite (=cranial) view of conical osteoderm shown in (H); (J) ribbed subconical osteoderm. Scale bar is 10 cm. Penkalski (2013).

Sacrum (or sacra) associated with Oohkotokia horneri. (A) Presacral rod(?) in ventral view; (B) dorsosacral(?) centra in dorsal (left) and ventral views; (C) posterior sacrals with reattached ?s3 rib in ventral view; (D–F) sacral ribs in cranial view; (G) fused neural arches in ventral and dorsal views; (H) nodosaurid sacral fragment. Scale bars in centimeters. Penkalski (2013).

See also A new species of Ceratopsid Dinosaur from the Late Cretaceous of southern Alberta, New species of End Cretaceous Hadrosaur from the Russian Far East, Cranial development in an Ornithischian Dinosaur, Head injury in a pachycephalosaur and A Heterodontosaurid Dinosaur from the Late Jurassic of Colorado.

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New description of an Ankylosaurid Dinosaur from Mongolia.

The 1971 Polish-Mongolian Palaeontological Expedition to the Gobi Desert unearthed a great deal of dinosaurian material, including the partial skeleton of an Ankylosaurid Dinosaur, which was given the specimen number ZPAL MgD I/113 and referred to the genus Dyplosaurus, but not properly prepared or described. Ankylosauridd were armored Ornithischian Dinosaurs from the Cretaceous. They typically had a thick covering of fused boney plates that enclosed their torsos in a sort of shell, which could be adorned with a variety of spikes and lumps. They also had armored heads, with a beak-like mouth that had teeth only at the rear, and often had a fused, boney lump at the end of their tales, which apparently served as a weapon.

In 1998 the specimen was sent to the Geological Museum of Oslo for preparation and study, and it is formally described in a forthcoming paper in the journal Acta Palaeontologica Polonica by a team of scientists led by Victoria Arbour of the Department of Biological Sciences at the University of Alberta.

Part of the posterior of the trunk of specimen ZPAL MgD I/113, showing boney scutes and impressions of soft armor. Scale bar is 10 cm. From Arbour et al. (2012).

Arbour et al. assigned specimen ZPAL MgD I/113 to the species Tarchia gigantea (there is currently dispute as to whether Dyplosaurus is a valid taxon at all), an 8-8.5 m, 4.5 tonne (probably) Ankylosaurid well documented from a number of other Mongolian specimens.

Reconstruction of Tarchia gigantea by Mineo Shiraishi.

Although there are several more complete specimens of Tarchia gigantea in various museum collections, ZPAL MgD I/113 does show some features not previously seen in the species, notably impressions of the keratinous scales that overlaid the armor plates, and an almost complete tail, which reveals T. gigantea to have had the longest known tail of any Ankylosaurid Dinosaur.

Two blocks from ZPAL MgD I/113 showing Large osteoderms (asterisks), scale impressions (arrowhead) and dark, shiny ossicles (arrow). From Arbour et al. (2012).

The tail of ZPAL MgD I/113 (A) and Saichania (B), another common Ankylosaurid Dinosaur from Mongolia. (2) Sharp osteoderms with a triangular cross section. (8)Nearly flat, elongated oval-shaped osteoderms. Scale bar is 10 cm. From Arbour et al. (2012).

See also Nesting behavior and parental care in an Ornithischian Dinosaur?