Volcanic activity in the Halmahera Islands.

Halamahera is the largest of the Maluku islands in Indonesia; the term Halamahera Islands is used to imply Halamahera Island plus the smaller islands around it, particularly the string of islands running parallel to the main island's west coast.

The Halmahera Islands.

The northernmost of these islands is Ternate, a volcanic island that forms the tip of a vast, submerged volcano, Gamalama. Gamalama is a stratovolcano (a cone-shaped volcano made up of layers of ash and lava, the sort of volcano you see in a Hollywood movie), with three cones in a north-south line across the island, with the youngest in the north and the oldest in the south. Gamalama is a very active volcano, with several eruptions a decade; since 1990 it has erupted in June 1991, May 1993, January-October 1994, July-October 2003, August 2007 and May 2008. Almost all eruptions are from the summit cones, though eruptions from fissures on the flanks have been recorded, in 1763, 1770, 1775 and 1962-3.

1788 illustration of an eruption on Gamalama, by George Bernard.

Having been quiet since 2008, on 1 December 2011 a white plume was seen reaching 150 m above Gamalama. The summit was obscured by cloud on the 2nd and 3rd, but when this cleared the plume was still present. The Indonesian Pusat Vulkanologi Dan Mitigasi Bencani Geologi (Centre for Volcanology and Geological Hazard Mitigation) recorded a number of small Earth tremors on the island during this period. On the 5th and 6th a plume of ash was recorded rising 2.4-3.0 km above the island and drifting southeast by the Darwin Volcanic Ash Advisory Centre. This plume has persisted till the time of writing (21 December 2011) reaching as high as 6.1 km, though it has often been obscured by heavy cloud in the area.

Over a hundred kilometers to the northeast lies Dukono, on the northwestern limb of Halmahera Island. Dukono has been in more-or-less constant eruption since 1933. It has a complex structure, with multiple overlapping craters and numerous peaks. Explosive eruptions and lava-flows are a regular feature of Dukono. The most recent explosive eruptions took place in August this year, since when a plume of ash has been more-or-less constant over the area, reaching as high as 3 km above the volcano.

An ash cloud over Dukono in 1991.

There are 13 other volcanoes in the Halmahera Islands. Of these Tarakan, Tobaru, Todoku-Ranu, Jailolo, Hiri, Tidore, Mare, Moti, Tigalalu, Amasing and Bibinoi have not erupted in historical times. Ibu last erupted in 2009, Gamkonora in 2007 and Makian in 1988.

The volcanos of the Halmahera Islands.

The Halmahera Islands arc a volcanic arc; formed where one tectonic plate is being subducted beneath another, with the underlying plate being melted by the heat of the Earth's interior, and lighter minerals bubbling up through the overlying plate to form volcanoes. However the Halmahera Islands are unique in that they lie on a double subduction zone. The underlying plate, a northeaster extension of the Molucca Sea Plate, is being overridden form the Philippine Plate from the east and the Eurasian Plate from the west. The Halmahera volcanoes are located where the Philippine Plate is overriding the Molucca Sea Plate; to the west the Sangihe Islands lie where the Molucca Sea Plate is being overridden by the Eurasian Plate.

The disappearing Molucca Sea Plate is giving rise to two island arcs, as it is subducted from two directions.

See also What happens when a volcano meets a subduction zone? Manila shaken by mild Earthquake, Fresh eruption on Mount Karangetang and Volcanoes on Sciency Thoughts YouTube.

How did raptors use their claws? (and did it help them learn to fly?)

The Dromaeosaurs were a group of small, feathered dinosaurs closely related to the birds. They are commonly referred to as 'raptors' on account of an enlarged claw on each foot which was held clear of the ground when walking and is generally assumed to have been a weapon; this claw resembles that of a bird of prey, which are also referred to as 'raptors'. This claw was also present in the other group closely related to birds, the Troodontids, though in these it was not as prominent. The Troodontids were apparently adapted for pursuit of prey, placing additional demands upon their limbs that the Dromaeosaurs, thought to have been ambush predators, lacked. Thus the foot of a Troodontid is a compromise, that of a Dromaeosaur a more specialized tool.

A graphite drawing of Velociraptor, a typical Dromaeosaur, by artist Matt Martyniuk. (Note: this is probably a more realistic interpretation of this pheasant-sized dinosaur than the things in Jurassic Park).

The Dromaeosaurs, Troodontids and Birds together are referred to as the Paraves; all three groups show certain similarities, that were presumably present in the common ancestor, including advanced plumage, wings with flight feathers and prominent hooked claws on their feet. The presence of wings with flight feathers in Dromaeosaurs and Troodontids is interesting, as neither of these groups appears to have been able to fly, implying that these strictures predated that ability in birds. Unraveling what these structures were used for in Dromaeosaurs and Troodontids would therefore provide useful insight into the evolution of the first birds.

The use of the enlarged claw by Dromaeosaurs and Troodontids has been a subject of discussion for decades. It has been widely speculated that this was used as a slashing weapon, enabling the dinosaurs to dispatch prey with one or more lethal kicks. Another theory was that the claws were used to leap onto and even climb up much larger prey in pack attacks by the small dinosaurs.

A paper by a team lead by Denver Fowler of the Musuem of the Rockies and the Department of Earth Sciences at Montana State University, published in the journal PLoS ONE on 14 December 2011, examines the use of the raptorial claw in the small Dromeosaur Dienonychus, using modern Raptors as an ecological model.

Modern Raptors do not use their claws to slash at their prey (some do kick, but they hold their claws clear when they do so), nor do they use their claws to overcome prey larger than themselves; they do not generally attack animals larger than themselves at all. The preferred method of attack by birds of prey is to hit it very hard with either their feet (not their claws) or their beak, killing it straight away, then use the claws to carry it off. Where this is not possible they hold prey down with their claws, while they dispatch it with their beaks. This is the strategy that Fowler et al. believe was adopted by Dienonychus. When holding down struggling prey, modern Raptors use their wings to stabilize themselves, flapping vigorously to maintain their balance. Many also 'mantle' their prey, using their wings to cover it while they eat it, so that it is hidden from rivals or larger predators; some do this with still living prey, which is believed to deprive the prey of sight, making it harder to escape.

Both of these tactics would have worked perfectly well with wings that were not capable of flying, which provides a plausible explanation for the evolution of wings, flight feathers and flapping muscles in early Paravians, prior to the evolution of flight. Thus Fowler et al. believe that birds were pre-adapted to flight before they took to the air.

Illustration from Fowler et al. (2011) showing feeding in Dienonychus as they interpret it. (A) Grasping foot holds onto prey. (B) Large claws used to maintain grip on prey. (C) Predators bodyweight pins down victim. (D) Elongated tail acts as balance. (E) Rear of foot held low to help restrain victim. (F) Wings flapped to maintain stable posture. (G) Arms encircle ('mantle') prey to prevent prey seeking escape route. (H) Head reaches between feet, tearing of strips of flesh.

See also A new Troodontid Dinosaur with an injured toe, Dinosaur feathers preserved in amber, Giant Bird from the Cretaceous of Kazakhstan and Dinosaurs on Sciency Thoughts YouTube.

Russian oil rig capsizes and sinks in under 20 minutes in the Sea of Othotsk.

On Sunday 18 December 2011 the Kolskaya exploration platform capsized in Sea of Othotsk in the Russian Far East, near the island of Sakhalin, while being towed towards the Kamchatka Peninsula, after completing a round of experimental drillings. The rig was carrying 67 people, of whom (at the time of writing) seven have been confirmed dead and 14 recovered alive, though suffering from acute hypothermia. The platform sank in under 20 minutes after running into trouble, before a helecopter dispatched to remove the crew arrived; lifeboats have been seen in the water without survivors, suggesting that the crew did not have time to evacuate properly. The rig was carrying only a small amount of fuel oil, so a major ecological disaster is not foreseen; the Sea of Othotsk is regarded by Russians as the world's richest fishery, so a major oil spill there would be a major problem for the authorities.

Russian Television report on the disaster.

The Finnish built Kolskaya was operated by ArktikMorNefteGazRazvedka, a company specializing in offshore exploration in the Arctic, on behalf of the state-controlled hydrocarbons giant Gazprom.

The Sea of Okhotsk lies between Kamchatka in the east and the Kuril Islands in the west; to the north it borders on the south Siberian Coast, and in the south the north coast of Hokkaido. It's deepest point is over 3000 m below the surface, but most of the Sea is less than 1000 m deep, giving it excellent potential for offshore exploration, despite it's harsh climate. It is estimated that there are 324 million tonnes of oil and 997 million tonnes of gas buried on the Sakhalin Island Shelf, the area where Kolskaya had been operating.

Oil reserves currently being exploited on the Sakhalin Island Shelf (orange), and with the potential for future exploitation (yellow).

See also The UN reports on oil pollution in Ogoniland, Drilling for oil on the Ningaloo Reef and Greenpeace activists occupy the offices of Cairn Energy.


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Earthquake in Texas attributed to fracking. 17 December 2011.

Slightly after 8.45 am on Saturday 17 December 2011, the city of Snyder in Scurry County, Texas was shaken by an Earthquake. The quake was small, with a magnitude of 3.2 on the Richter Scale, but extremely shallow, about 5 km bellow the ground according to the United States Geological Survey, and took place about 9 km north of the city.

Location of the 17 December Quake, from the USGS.

Texas does have a small fault zone, which passes through El Paso and Van Horn and causes the occasional minor earthquake, 110 between 1847 and 1994, but this does not pass within 400 km of Snyder, so Earthquakes should be quite rare around the city. Unfortunately Snyder has suffered dozens of Earthquakes in the last four years, which does require an explanation.

Hydraulic Fractionation (Fracking) os a process by which water and chemicals are forced into rocks at high pressure in order to release hydrocarbons, usually natural gas but in Texas the process is also used by oil extractors. The process has been in use in Texas since 2005, and has been credited with creating a major local economic boom (no pun intended), and Texas has always been the US state most friendly to the hydrocarbons industry. Nevertheless people are upset.

Fracking causes earthquakes. This is the point of fracking. Blasting pressurized liquids into subterranean strata is just the same as dynamiting surface deposits, it is intended to fracture the rocks explosively. A fracking operation that did not cause earthquakes would not achieve anything else. Where the industry disagrees with its critics is the scale of earthquakes produced. Fracking operators are typically trying to cause earthquakes with a magnitude of less than 1.0 on the Richter Scale. The Richter Scale is logarithmic, so a magnitude 2.0 quake is 10 times as powerful as a magnitude 1.0 quake, and a magnitude 3.0 quake is 10 times as powerful as a magnitude 2.0 quake and 100 times as powerful as a 1.0 quake. A quake with a magnitude of over 3.0 is thus between a hundred and a thousand times as powerful as a quake of under 1.0, not something that one would expect as an accidental consequence. Despite this fracking operations across the world have been associated with a sharp rise in the number of quakes locally, with quakes in excess of magnitude 3.0 not uncommon. Simply denying responsibility for these quakes is not really an answer; in order to avoid being held responsible the industry will need to provide a plausible alternative explanation for the rise in quake activity.

Earthquakes are not the only problem that the fracking industry has been associated with. Earlier this month the United States Environmental Protection Agency produced a draft report indicating that natural gas extractor Encana was directly responsible for contaminating a drinking water aquifer in Wyoming, something that opponents of fracking have long accused the industry of. The principle behind this concern is quite simple; water for drinking is obtained from aquifers running through subterranean strata; these are sometimes described as 'underground rivers' but this is misleading, the water is running through porous rocks, typically sandstone or chalk, rather than free flowing as in a river. The pressure blasts used in fracking are intended to shatter rocks containing natural gas in order to release the gas, but do not stop at stratigraphic boundaries; they quite happily shatter other rocks too, allowing the chemicals used in the fracking process to permeate into the water bearing rocks, contaminating the water. Again the fracking industry has argued that there is no proof that they are responsible for the contamination, but has failed to provide an alternative explanation.

Simplified diagram illustrating the potential connection between fracking and aquifer contamination.

Texas is extremely drought prone, and Texans are sensitive about water, so many people in Texas have been following events in Wyoming quite closely. The industry in Texas has been quick to point out that the natural gas bearing rocks are deeper beneath the water bearing aquifers in Texas than in Wyoming, but they are also causing larger earthquakes than can be accounted for, so people's concerns will not be dropped easily.

As well as the potential for contaminating aquifers, the fracking industry also uses a great deal of water. The Texas Water Development Board estimated that the industry used 51.1 billion liters of water in 2010. At the same time farms and cities in Texas were suffering extreme water shortages. It is estimated that the water needs of the fracking industry will double by 2020. Potentially brackish water from deep aquifers could be used by the industry, but it is cheeper and easier to use potable water from the shallow aquifers that provide Texas with its water for agriculture and domestic use.

See also Fracking linked to Earthquakes in Lancashire, northeast England.

Identifying Triassic footprints.

Brachychirotherium is a type of fossil footprint found in Triassic sedimentary rocks throughout the world (fossil tracks are named as if they were species of animals rather than geological structures, because of their clear biological origin). Ichnologists (scientists that study fossil tracks) have long considered them to have been produced by a large quadruped archosaur (the group that includes dinosaurs and crocodiles) with an upright gait. While it would not be possible to identify the exact animal that made the prints (and it is unlikely to be the work of a single species), it should be possible to name a group of animals responsible, in the same way that a modern tracker could tell that a trail was made by a big cat and not a dog or a bear, but not wether it was made by a tiger or a lion.

Brachychirotherium foot prints from the Redonda Formation in New Mexico.

There were roughly seven groups of Archosaurs living during the Triassic (classification systems vary slightly depending on author, and some individual species have not been placed in any group with confidence yet). There were the Phytosaurs, the Aetosaurs, the Rauisuchians, the Crocodylomorophs, the Ornithosuchians, the Pterosaurs and the Dinosauromorphs. Of these the Phytosaurs had a sprawling gait similar to modern crocodiles, the Orinthosuchians and Dinosauromorphs had bipedal gaits (some later dinosaurs became secondarily quadruped) and the Pterosaurs were winged, flying animals that produced very distinctive tracks when walking on the ground, leaving just three groups that could potentially have made the tracks.

Statue of a Phytosaur in Kings Park, Perth, Western Australia, by artist Travis Tischler.

Modern crocodilians have a sprawling gait and a semi-aquatic lifestyle, but Triassic Crocodylomorphs (the ancestors of modern crocodilians) were smaller, fast moving animals with an upright gait, thought to have resembled reptilian cheetahs or greyhounds; crocodilians only adopted a sprawling, semi-aquatic lifestyle in the Jurassic, after the extinction of the Phytosaurs. These early, upright, Crocodylomorphs could conceivably have made a track like Brachychirotherium, but the tracks are widespread throughout the Triassic, then disappear at the beginning of the Jurassic, whereas upright Crocodylomorphs persist throughout the Jurassic, declining throughout the Period and disappearing before the Cretaceous. This is a poor fit for the ditribution of Brachychirotherium, and would require a good explanation before Crocodylomorphs could be attributed as the creators of these prints.

Dibothrosuchus elaphros, an Early Jurassic upright Crocodylomorph from China. From X.-C. Wu, and S. Chatterjee (1993).

The Aeotosaurs were upright, heavily armored, herbivorous animals with a global distribution (this is less impressive in the Triassic than today, since all the continents were fused together in a single super-continent, Pangea; anything that could walk could get anywhere in the world). They have a good fossil record, with over 20 described genera, but most of these are known from their armored bodies; the armor-less feet have a much poorer fossil record.

A reconstruction of the Aetosuar Desmatosuchus spurensis, from the Late Triassic of the southwestern United States, by Jeff Martz of the Paleontology Division at Texas Tech University.

The other group that might have plausibly created the Brachychirotherium footprints are the Rauisuchians. This is the group from which the Crocodylomorphs arose, so technically the Crocodylomorphs should be considered to be Rauisuchians, though the Crocodylomorphs are sufficiently different from the other Rauisuchians that they can be regarded as a separate group in this context. The Rauisuchians were carnivorous animals with an upright gait that were widespread throughout the Triassic then went extinct abruptly at the end of the Period. As carnivores the Rauisuchians were likely to be less numerous than the herbivorous Aetosaurs, but studies on food webs in other Periods have found that carnivores often leave more footprints than herbivores, even though they are less numerous.

Reconstruction of the Rauisuchian Batrachotomus kupferzellensis by artist Dmitri Bogdanov.

Earlier this week (12 December 2011) a paper appeared in the journal Ichnos by Spencer Lucas, of the New Mexico Museum of Natural History and Science, and Andrew Heckert, of the Department of Geology at the Appalachian State University, in which they re-examine the Brachychirotherium footprints, in the light of the recent discovery of two new specimens of the Aerosaur, Typothorax coccinarum from New Mexico, with intact and well preserved feet.

A reconstruction of Typothorax coccinarium based upon the New Mexico material. (A) one of the specimens (NMMH P-56299) as it was found preserved. (B) Side view of the living animal. (C) View of the animal from above. (D) Front view. (E) Rear View.

Brachychirotherium is described as a trackway in which all five digits are present on both fore- and hindlimb impressions, where these are complete (not all vertebrate tracks show this, many animals have lost digits), the hind-prints are 40% larger than the fore-prints, the angle between digits I and II (thumb and first finger on a human hand) is greater than 4o°, digit III is the longest and digit II the second longest.

Brachychirotherium footprints (A-C) and trackway (D).

Typothorax is a relatively well documented Aetosaur in the American Southwest, though this is the first time its feet have been documented; in most known specimens only the armored body is preserved. The feet of Typothorax confirm well to the Brachychirotherium morphology, although many of the recorded Brachychirotherium tracks are to large to have been made by Typothorax, there are other Aetosaurs that are large enough to have produced the Brachychirotherium prints. After comparison of the feet of Typothorax, the Crocodylomorph Terrestrisuchus, and the Rauisuchian Postosuchus, Lucas and Heckert conclude that Brachychirotherium is the work of Aetosaurs.

The fore- (above) and hindlimb (below) bones of Terrestrisuchus, Postosuchus, and Typothorax, and the Brachychirotherium impressions.

Brachychirotherium is most abundant in Late Triassic sediments, there are records from Early and Middle Triassic Strata, but these are considered dubious, and Lucas and Hekert reject them completely. There are no records of Brachychirotherium from post-Triassic rocks; the fossil disappears at the end of the Triassic, and is often used to establish a Triassic date for rocks. Aetosaurs appeared in the Late Triassic and flourished up until the end of the Period, when they went extinct abruptly. There is also a strong calibration in geographical distribution between Brachychirotherium and Aetosaurs; the trace fossil is most abundant in locations where the bones have also been found, whereas Rauisuchian bones are absent from some areas where Brachychirotherium is abundant. This in itself would not be considered good enough evidence to attribute Brachychirotherium to Aetosaurs, but it is strong supporting evidence.

The distribution of Brachychirotherium and Aetosaur remains in the Late Triassic.

See also Dinosaur footprints discovered in Southwest Arkansas.

Art from human body parts.

This month an exhibition opened at the GV Art gallery in Marylebone, London, by American artist Andrew Krasnow, consisting of a sculpture of a heart made out of human skin. This is clearly intended to shock, and has attracted criticism from a number of sources including some US politicians. Krasnow seems keen to play on this, issuing statements to the effect that he only uses white skin since most of the suffering in America is caused by white people; which is silly, slightly racist and bound to upset someone.

Heart made from human skin by Andrew Krasnow.

Modern artists often insist that the purpose of art is to shock and provoke thought. Beyond the obvious fact that this is clearly wrong, since much perfectly good art does nothing of the sort (you may or may not like Constable, but his skill as an artist is hard to deny), it does occur that many artists have been relying on shock for over a century now, and that treading the same path as Mann Ray, Peiro Manzoni and Tracy Emin is not so much 'thought provoking' as 'safe'.

For art to have any real value as a thought provoking device it needs to extend beyond a gallery art enthusiasts go to be shocked in a safe environment and reach a wider audience. Thus Dickens and Hardy were able to shock a wide audience by inserting images of searing poverty into novels and HG Wells could shock by describing the fall of the British Empire in a science fiction story. Of course these artists also created paths that have become well worn by others; storytellers still use poverty to shock (Ben Okri's Famished Road, Danny Boyle's Slumdog Millionaire) or hide disturbing thoughts in science fiction (James Cameron's Avatar, Neill Blomkamp's District 9). The most shocking form of art we encounter in our daily lives is probably photojournalism, which brings us face-to-face with disturbing facts about the world we live in, rather than concept based instillation art like Krasnow's.

This image by photojournalist Jodi Bieber, of a young Afghan woman who had had her nose cut off for leaving her husband, is incredibly powerful and reached a very wide audience, appearing on the cover of Time, a magazine that appears on newsstands throughout the world, and winning the prestigious World Press Photo award.

All of which is slightly beside the point. I am not, and do not pretend to be, an art expert. What did strike me about the Krasnow exhibition however was the statement to the effect that Krasnow used skin from bodies donated to science. Donating one's body to science is a highly commendable thing to do. Much of our modern medical knowledge comes from work by anatomists, and work on bodies has become essential in fields such as forensics. But donating your body to science is not the same as just saying you do not want it anymore so you don't mind what happens to it. If we give money to a charity collector who turns out to be spending the money themselves we become upset, and possibly call the police. Worse still we may become discouraged from making future charitable donations. The same surely applies to donating a body to science. It might be that Krasnow specifically obtains permission from his subjects before they pass away, but this is not obvious. By stating that he uses material from bodies donated to science Krasnow may be discouraging other people from donating their bodies to science, thereby denying resources to scientists working for the greater good of all humanity. Which would of course be shocking.

An American Titanosaur.

Sauropod dinosaurs were massive, long-necked, long-tailed creatures that have long been regarded as the largest land animals ever to have lived. They reached their most diverse in the Late Jurassic, with only two groups surviving into the Cretaceous, and only one of those groups and only one of those groups surviving till the end of the period. However the group that did, the Titanosaurs, grew to become the very largest of the group, with the largest known, Argentinosaurus reaching an estimated weight of 78 000 kg.

Argentinosaurus as depicted by Argentinean artist Jorge Antonio Gonzalez.

These super-sized sauropod dinosaurs were first recognized in South America, and have subsequently been found in Eurasia and Africa. No North American titanosaurs have been formally recorded, although scattered remains of therapod dinosaurs have been found from the Maastrichtian (Latest Cretaceous) of the Southwestern United States since at least the 1920s. These have been assigned to the species Alamosaurus sanjuanensis, but have generally been considered to fragmentary to allow detailed studies of their taxonomic affinities.

The latest edition of the journal Acta Palaeontologica Polonica contains a paper by Denver Fowler of the Museum of the Rockies and the Department of Earth Sciences at Montana State University and Robert Sullivan of The State Museum of Pennsylvania in which they re-examine A. sanjuanesis and publish a description of new material gathered from the Ojo Alamo Formation in New Mexico by field crews from the State Museum of Pennsylvania.

Like previous material assigned to A. sanjuanensis the Ojo Alamo material is extremely fragmentary. It clearly contains material from more than one animal, and this is either from parts of the animal that have not previously been discovered, or that are to badly damaged for easy comparison. This is not unusual when dealing with the bones of a large sauropod dinosaur; in order for the animal to be preserved well it needs to be buried fairly quickly, unlikely with a creature of this size.

The absence of a direct comparison between specimens prevents 100% confidence that the new material belongs to the same species as the previously discovered material, however in other parts of the world there is typically only one species of large sauropod dinosaur living at any one time, and there is no evidence to suggest that the Southwestern United States was any different in this respect, so Fowler and Sullivan have assigned the new material to A. sanjuanensis.

The femur of Alamosaurus sanjuanensis in the location where it was found.

Some of the new material is also considerably larger that previously discovered specimens assigned to A. sanjuanensis, suggesting that it came from a much bigger animal. If all the material is considered to come from members of the same species, then the only way that this can be explained is if all previous material has come from juvenile individuals. This is not as great a presumption as it sounds.

Earlier this year David Varricchio of Montana State University published a paper in the journal Historical Biology articulating the view, long held by many palaeontologists, that dinosaurs, and in particular vert large dinosaurs, may have had a life cycle in which a large number of young were produced and the overwhelming majority of individuals died before they reached full maturity. The implication of this is twofold. Firstly the majority of fossil dinosaurs discovered will be juveniles, smaller than fully grown adult individuals. Secondly, as in modern birds, these individuals are unlikely just to be smaller versions of the adult animals, they will almost certainly lack some morphological traits seen in the adults, such as sexual characteristics.

Comparison of the size of a new vertebra found by the Pennsylvania team allows a direct comparison of the size of A. sanjuanensis with other titanosauran sauropods. It has previously been suggested that A. sanjuanensis might weigh slightly over 32 500 kg, but examination of the new material suggests that it may well have grown to sizes rivaling Argentinosaurus. Fowler and Sullivan do not make a claim for the absolute size of A. sanjuanensis, but they do observe that it was almost certainly the largest dinosaur ever to roam North America.

See also New dinosaurs from old drawers, Nesting behavior and parental care in an Ornithischian Dinosaur? Dinosaur footprints discovered in Southwest Arkansas and Dinosaurs on Sciency Thoughts YouTube.