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number centrosaurs preserved in the Hilda area ranged from several hundred to about 1,500 individuals. However, the presence of centrosaur bonebeds on both sides of the South
Saskatchewan River suggests that the river eroded away many fossil deposits that had originally been preserved there. Therefore the original size of the centrosaur herd was probably even larger than the estimate based on still-accessible fossils would suggest and may have included up to several thousand dinosaurs.
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the filled-in remains of an ancient body of flowing water. These contacts record where the channel cut down into the sediment now lithified as the fossil-bearing mudstone. The researchers couldn't find the bed's northern boundary, which they felt might extend north of the northernmost bonebed as part of a succession of stacked mudstone beds. An ancient channel cut all the way through the sediments now composing the mudstone, and its deposit forms the Hilda bonebed's southern boundary.
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56:. It was first described in the scientific literature by David Eberth, Donald Brinkman, and Vaia Barkas in 2010 after more than ten years of research. The Hilda mega-bonebed is significant because the behavior of the preserved dinosaurs themselves was the dominant cause of its existence, rather than the stratum's geological history like most bonebeds. It is also Canada's largest bonebed.
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because they are divided by ancient channel deposits. The only certainty regarding the number of events involved in the formation of the bone beds is that more than one occurred since at least one bonebed is known to be preserved in a rock stratum directly over another bonebed. The Hilda bonebeds distinguish themselves by being preserved in a single easily traceable stratum.
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each side of this central region of the bonebed being much sparser. The researchers took the average bone density of two excavations within H97-04, 1 individual per 3 square meters, and projected it over the 2,000 square meters of the H97-04 bonebed. They estimated that this core area preserved the remains of 667 centrosaurs.
144:, research at Hilda began in earnest. In only two days, researchers discovered 14 separate bonebeds in one mudstone bed that extended for at least 7 km, with 3.7 km worth of visible outcrops. By the conclusion of the research program, the scientists mapped the bonebeds and excavated the bonebed cataloged as H97-04.
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direction. As the migration progressed the family groups would gradually merge, becoming large herds, which may have protected them from predators on the journey. Eberth, Brinkman, and Barkas noted that Hilda is located roughly halfway between the ancient coast and the
Dinosaur Provincial Park bonebeds.
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After they died the dinosaurs's carcasses were deposited in clumps spread over kilometers. Variation in the location and concentration of centrosaur bones was caused by factors like force and dimensions of the flood, smoothness or roughness of local terrain, and the centrosaurs' distribution in life.
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Eberth, Brinkman, and Barkas also noted the presence of two beds in the mudstone hosting the Hilda bonebeds that weren't ceratopsian bonebeds, but rather they contained vertebrate microfossils. The first of these was H97-09, a natural part of the same stratum that hosted the ceratopsian bonebeds, but
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H97-04 represented the densest part of the Hilda mega-bonebed and formed the "core" of its fossil deposits. Nevertheless, the amount and quality of preserved bone was highly variable within this bed. The centrosaur fossils of H97-04 were most densely concentrated in its middle 50 m, with the 50 m on
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H97-04 is the largest of the fourteen bonebeds, at 150 m in width. If one assumes that H97-04's 150 m width is its longest linear dimension then it had an area of about 17,671 m. Bonebeds other than H97-04 were less than 50 m wide. These individual component bonebeds tend to have areas of only a few
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The bonebeds at Hilda and in
Dinosaur Provincial Park also preserve similar quantities and types of plant fossils. The two areas differed, however, in that all of the component bonebeds of the Hilda mega-bonebed, apart from H97-04, were smaller and preserved lower numbers of dinosaurs than those of
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Their eventful taphonomies suggests that the centrosaur carcasses were permanently buried by a later flood rather than the one that drowned them. These floods may actually have been common enough to be the primary means by which sediment was deposited in the Hilda area during the
Cretaceous. Eberth
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The researchers estimated the entire Hilda complex to be 2.3 square kilometers in area based on the length of its north-south and east-west axes. This is the size of about 280 football fields, and is one of the largest dinosaur bonebeds ever discovered. Bonebeds left by such large animals over wide
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The remaining 15,600 square meters of the Hilda mega-bonebed contained only about 10% of the fossil density observed in the "core" of H97-04. Assuming the periphery of H97-04 had this estimated average density, there would have been about 500-600 more centrosaurs overall. Thus, the total estimated
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The stratum hosting the mega-bonebed has different sorts of contacts with other strata at different locations across its extent. The most distinct boundaries separate the Hilda bonebed mudstone from other mudstones above and below it. Less clear boundaries occur where the bonebed mudstone contacts
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According to Eberth, Brinkman, and Barkas, the idea that several of these bonebeds could have formed together is "difficult to test", however. This difficulty emerges from the complicated nature of local stratigraphy as individual bonebeds are difficult to track for more than a few hundred meters
518:. These processes left the abrasion and toothmarks seen on the bones preserved at H97-02. Chemical reactions between the decaying dinosaur flesh and floodwaters caused iron to precipitate out of the water and formed the ironstone concretions commonly found in the mudrock hosting the mega-bonebed.
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likely had poor swimming abilities most of the herd would have drowned during sufficiently severe flooding events. Centrosaurs not killed by the flooding would have been vulnerable to "flood-related disease" outbreaks in its aftermath. Tropical storm-induced floods were probably common sources of
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The migration hypothesis proposed by
Brinkman and the others was that centrosaurs bred near the coast and reared their young in small family groups. These groups would then migrate toward the west in order to avoid seasonal hazards like storms or to exploit seasonally available resources in that
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data from the bonebed H97-04, although all the others were also examined to check the quality and number of preserved bones. The research at Hilda was so complex that over ten years passed from the start of the project until David A. Eberth, Donald B. Brinkman, and Vaia Barkas published a formal
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and that centrosaur herds were sometimes significantly larger than previously thought, possibly containing numbers in the high hundreds to low thousands. The abundant mudstone beds in the Hilda area may imply that floods like the one drowned the centrosaurs at Hilda were common. The researchers
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The researchers found that the larger bones in each bonebeds tended to lie at the base of the stratum with fragments of bone becoming smaller and less concentrated at higher positions in the mudstone bed. Most of the bones were angled parallel to the plane of the bed. The researchers only found
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Burial was not always permanent as some remains seem to have been uncovered again by later flood activity only to be buried again by yet more later floods. The process of reworking and reburial might have occurred over decades or millennia before the remains were buried for good in their final
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For characterization of H97-12 as a lens, see Eberth, Brinkman, and Barkas (2010); "Bonebed
Taxonomic Composition, Bone Concentration, and Preliminary Taphonomy", page 502. For creeks as probable source of the sandstone lenses in the mudstone, see "Interpretations: Depositional History", page
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In H97-02 the researchers found that at least 6 individuals were discovered in a 20 square meter area, but suspected that this relatively high density was not uniform throughout the deposit. They concluded that the number of centrosaurs preserved at H97-02 was probably "in the low hundreds".
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traces. The root traces come at a variety of orientations ranging from horizontal to vertical. Some of these being the roots' original life position. The researchers concluded that the abundance of preserved plant material probably reflects the great abundance of local plant life during the
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Eberth, Brinkman, and Barkas tried to estimate the number of bones in the mega-bonebed in order to infer the number of animals that died together during the formation of the deposit. However, the complexity of a bonebed's geologic and taphonomic history can only allow for rough estimates.
269:. Eberth, Brinkman and Barkas estimated that in the Hilda area, the Dinosaur Park Formation was almost 60 m thick between the over- and under-lying formations, but glacial activity and slumping had removed all but 43 m of this at the field site. When the researchers examined the
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Previous research on
Albertan centrosaur bonebeds interpreted their formation in terms of a herd of dinosaurs drowning while trying to cross a swollen river. Eberth, Brinkman, and Barkas proposed a different explanation for the Hilda mega-bonebed, hypothesizing that a herd of
1223:
D.A. Eberth, D.B. Brinkman, V. Barkas, "A centrosaurine mega-bonebed from the Upper
Cretaceous of southern Alberta: Implications for behaviour and death events" in New Perspectives on Horned Dinosaurs: The Ceratopsian Symposium at the Royal Tyrrell Museum, September 2007
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in the 1990s because Hilda was an ideal location for maintaining physical continuity across the bonebeds' expanse. Physical continuity is important, because discontinuity in the rock strata can make it harder to tell if the bones were deposited at the same time or not.
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resting place, which was often in deposits left by channels of flowing water. Eberth, Brinkman, and Barkas thought that the above scenario "appl particularly well" so the Hilda bonebeds formed as a result of similar processes to those of
Dinosaur Provincial Park.
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bonebed, the study of the fossils preserved in the Hilda mega-bonebed provides additional data that will help scientists estimate the size of ceratopsid herds and therefore better understand ceratopsid social behavior. Hilda increases the evidence for herding in
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are common in late
Cretaceous strata of central and southern Alberta. The close proximity of such a large number of bonebeds has fueled suspicions in some experts that some of the different bonebeds may have actually formed simultaneously in the same events.
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In two 2005 scientific papers, Eberth, Getty, and Currie formulated a hypothesis for the formation of the centrosaur bonebeds of Dinosaur Provincial Park. They envisioned common flooding events drowning large numbers of local wildlife, including herds of
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of the Hilda site they found that the fourteen bonebeds occupied identical positions in the stratigraphic column. This continuity in the mudstone was what allowed them to infer that each bonebed was actually a component of a single large "mega-bonebed".
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bonebeds of Dinosaur Provincial Park likely formed simultaneously in a manner analogous to the formation of the Hilda bonebeds, which the researchers estimated to be spread over 2.3 km. The researchers only collected fossils and
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can be found scattered throughout the bed, but were most abundant where fossils were also common. Fossils are most common in the lowest parts of the bed. There are signs of deformation in the sediment composing the mudstone.
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The second was a lens of sandstone that formed after the ceratopsian bonebeds cataloged as H97-12. This lens of sandstone penetrated down into the bed that hosted the ceratopsian bonebeds, probably deposited by a
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contended that the existence of a single mega-bonebed with 14 individual components at Hilda may imply that some of the bonebeds of Dinosaur Provincial Park may themselves be components of larger mega-bonebeds.
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hundred to a few thousand square feet and would have maximum areas of somewhat less than 2,000 square meters. The individual bonebeds at Hilda were generally smaller than those at Dinosaur Provincial Park.
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the park. The centrosaur bonebeds of Dinosaur Provincial Park were often more than 10,000 square meters in area. These bonebeds tended to preserve centrosaurs in the "hundreds to low thousands" apiece.
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The Hilda Mega-bonebed is about 76 million years old, the same age as the lower Dinosaur Park Formation outcrops of the Dinosaur Provincial Park strata. Monodominant bonebeds of horned dinosaurs like
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Eberth and the other researchers considered Hilda a prime site for a continuous bonebed for two reasons, one related to its history, one related to its present geography. First, during the
230:. The individual bonebeds in the complex are recognizable as dense concentrations of ceratopsid bones. Research on the bonebeds of Dinosaur Provincial Park has discovered that
832:
For geographic information, see Eberth, Brinkman, and Barkas (2010); "Introduction", page 496. For timing of glaciation, see "Interpretations: Depositional History", page 504.
482:. These floods would have been large enough to entirely submerge the coastal lowland plains that the dinosaurs were living on, leaving nowhere to hide or escape to. Because
140:, the Royal Tyrell Museum finally performed a preliminary survey of the area studied by Langston and Taylor and entire new bonebeds were discovered. The next year, in
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At its thinnest point the mudstone bed hosting the centrosaur fossils is 25 cm thick and it measures 1 m at its thickest. Eberth, Brinkman and Barkas observed
109:) oversaw the collection of fossils from yet another bonebed in the same region. These prospective bonebeds attracted the attention of scientists working for the
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Brinkman and Barkas observed evidence that the sediment was deformed and contorted near the top and bottom before it hardened into the mudstone it is today.
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Eberth, Brinkman, and Barkas (2010); "Bonebed Taxonomic Composition, Bone Concentration, and Preliminary Taphonomy", page 502 and "The Site",
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for general range and Eberth, Brinkman, and Barkas (2010); "Interpretations: Death Assemblage Size Estimates", page 506, for maximum area.
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near the ancient coast, while the famous centrosaur bonebeds of Dinosaur Provincial Park were all preserved in more inland habitats.
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areas are a rare discovery. However, completely excavating the bonebed would be too huge and complex an undertaking to be practical.
364:. Nevertheless, every single ceratopsian fossil that could be identified from the bonebeds had features closely resembling those of
176:
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The mega-bonebed is located 25 kilometers west of the town of Hilda, Alberta in a "steep-walled" valley cut into the landscape by
491:. According to David Eberth, smaller local wildlife were better equipped to escape the floodwaters than centrosaurs, noting that
1034:
Eberth, Brinkman, and Barkas (2010); "Bonebed Taxonomic Composition, Bone Concentration, and Preliminary Taphonomy", page 502,
238:
deposits tended to be circular to ovular in shape when viewed from above, so the similar Hilda bonebeds probably were as well.
1056:
Eberth, Brinkman, and Barkas (2010); "Bonebed Taxonomic Composition, Bone Concentration, and Preliminary Taphonomy", page 503.
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Eberth, Brinkman, and Barkas (2010); "Bonebed Taxonomic Composition, Bone Concentration, and Preliminary Taphonomy", page 502.
467:. The researchers concluded that all of the component bonebeds of the Hilda complex formed during the same individual flood.
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After being deposited in their final resting places the carcasses were torn apart, had their bones trampled and chewed by
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The region around the Western Interior Seaway was prone to tropical storm activity, many of which could become full-scale
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102:
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Eberth, Brinkman, and Barkas (2010); "Introduction", page 496 and "Origin and Significance of the Hilda Mega-Bonebed",
583:. Flowing water would distribute these remains across the local floodplain, where they would be buried by later floods.
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in addition to its centrosaur fossils. The Excavation B site at H97-04 preserved a fish scale and two theropod teeth.
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The mudstone hosting the Hilda mega-bonebed preserves large quantities of plant fossils throughout the bed as well as
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skull and H97-19 had a partial ceratopsian tail. As such, they regarded such higher quality specimens as very rare.
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participated in seasonal migrations, travelling from east to west. Brinkman and others proposed this hypothesis in
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These variations likely coincided with the presence of small "sub-environments" commonly found between rivers like
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At the conclusion of their research program, Eberth, Brinkman and Barkas were unable to identify the bonebeds'
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330:. Like H97-09, H97-12 contained only fragmentary remains of aquatic vertebrates like crocodiles and turtles.
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Eberth, Brinkman, and Barkas (2010); "Interpretations: Death Assemblage Size Estimates", pages 505-506.
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Map of North America and the Western Interior Seaway in the Late Cretaceous (~ 75 million years ago)
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They concluded that the Hilda bonebeds formed simultaneously when a herd consisting of thousands of
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Eberth, Brinkman, and Barkas (2010); "Interpretations: Death Assemblage Size Estimates", page 506,
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Eberth, Brinkman, and Barkas (2010); "Interpretations: Death Assemblage Size Estimates", page 506.
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Eberth, Brinkman, and Barkas (2010); "Interpretations: Death Assemblage Size Estimates", page 505.
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Eberth, Brinkman, Brinkman, and Barkas (2010); "Interpretations: Depositional History", page 505.
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Eberth, Brinkman, and Barkas (2010); "Geological Setting and Depositional Context", page 497.
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Eberth, Brinkman, and Barkas (2010); "Interpretations: Depositional History", pages 504-505.
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The Hilda mega-bonebed may also support the previously suggested notion that some kinds of
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370:. They consequently felt confident that the bonebed was mostly composed of that species.
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Eberth, Brinkman, and Barkas (2010); "Interpretations: Depositional History", page 504.
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terrain that breaks up many probably equivalent deposits in Dinosaur Provincial Park.
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associated or articulated fossils at two of Hilda's bone beds; H97-03 had a partial
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See Eberth, Brinkman, and Barkas (2010); "Abstract", page 495 for authorship and
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Eberth, Brinkman, and Barkas (2010); "Introduction", page 497 and "The Site",
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Eberth, Brinkman, and Barkas (2010); "Introduction", page 496 and "The Site",
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Eberth, Brinkman, and Barkas (2010); "Mega-Bonebed Host Bed", pages 500-502.
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drowned in a flood. The researchers further speculated that some of the 17
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Eberth, Brinkman, and Barkas (2010); "Mega-Bonebed Host Bed", page 502.
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Eberth, Brinkman, and Barkas (2010); "Mega-Bonebed Host Bed", page 500.
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Eberth, Brinkman, and Barkas (2010); "Discussion", pages 506-507.
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H97-04's excavation site Excavation A preserved shed teeth from
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Eberth, Brinkman, and Barkas (2010); "Abstract", page 495 and
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Eberth, Brinkman, and Barkas (2010); "Introduction", page 497.
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Eberth, Brinkman, and Barkas (2010); "Introduction", page 496.
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to explain why ceratopsians represented a greater portion of
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Eberth, Brinkman, and Barkas (2010); "Discussion", page 507.
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Eberth, Brinkman, and Barkas (2010); "Discussion", page 506.
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Eberth, Brinkman, and Barkas (2010); "Abstract", page 495.
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The Hilda mega-bonebed lies within the bottom 25 m of the
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where more sediment would have been deposited than at
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1085:"Origin and Significance of the Hilda Mega-Bonebed".
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967:"Origin and Significance of the Hilda Mega-Bonebed".
463:, as well as other local wildlife, were killed by a
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360:remains to a rank more specific than the subfamily
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1211:"Alberta Dinosaur Bonebed is Largest Ever Found"
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474:. Similar weather events occur today in the
430:of differing size, champsosaur vertebrae, a
93:bonebed near Hilda, Alberta. Later, between
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1213:. Royal Tyrell Museum. June 17, 2010.
7:
1218:Hilda Dinosaur Mega-Bonebed, Alberta
121:the area was situated closer to the
76:Royal Tyrrell Museum of Paleontology
35:is a complex of fourteen probable
16:Fossil locality in Alberta, Canada
14:
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596:, another ceratopsid known from
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526:Comparison with other bonebeds
495:could escape by flight, while
169:Geographic location and extent
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438:clam, and two unidentifiable
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1220:. The Canadian Encyclopedia.
103:Provincial Museum of Alberta
44:discovered near the town of
642:biodiversity at sites like
593:Pachyrhinosaurus canadensis
540:, which is also known from
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250:Lithology and stratigraphy
537:Styracosaurus albertensis
228:South Saskatchewan River
127:Dinosaur Provincial Park
617:Although not the first
267:Dinosaur Park Formation
259:Dinosaur Park Formation
123:Western Interior Seaway
89:recorded evidence of a
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163:scientific literature
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1294:1959 in paleontology
1284:Geography of Alberta
600:bonebeds in Alberta.
544:bonebeds in Alberta.
489:Centrosaurus apertus
461:Centrosaurus apertus
367:Centrosaurus apertus
350:Centrosaurus apertus
232:ceratopsian bonebeds
200:class=notpageimage|
149:Centrosaurus apertus
107:Royal Alberta Museum
68:Inaccurate model of
38:Centrosaurus apertus
1169:Royal Tyrell Museum
1087:Royal Tyrell Museum
1071:Royal Tyrell Museum
1040:Royal Tyrell Museum
934:Royal Tyrell Museum
821:Royal Tyrell Museum
644:Unity, Saskatchewan
511:, ponds or creeks.
487:mass mortality for
418:, wood debris, and
161:description in the
111:Royal Tyrell Museum
60:History of research
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339:Centrosaur remains
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101:Don Taylor of the
87:Wann Langston, Jr.
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33:Hilda mega-bonebed
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23:Restoration of a
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1256:Paleontology
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613:Implications
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312:crocodilians
308:champsosaurs
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271:stratigraphy
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203:Location of
153:Centrosaurus
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91:Centrosaurus
90:
80:
71:Ornithomimus
69:
36:
32:
30:
25:Centrosaurus
24:
408:champsosaur
358:ceratopsian
290:concretions
221:Pleistocene
219:during the
1278:Categories
1205:References
516:scavengers
480:Bangladesh
472:hurricanes
440:coprolites
432:fish scale
158:taphonomic
119:Cretaceous
1244:Dinosaurs
675:Footnotes
669:Taphonomy
590:Skull of
446:Formation
428:theropods
287:Ironstone
283:claystone
279:siltstone
658:See also
501:reptiles
436:pisidiid
236:mudstone
217:glaciers
42:bonebeds
1230:Portals
1224:(2010).
497:mammals
320:turtles
261:strata.
209:Alberta
131:badland
50:Alberta
1268:Canada
1196:Eberth
1165:Eberth
1153:Eberth
1122:Eberth
1083:Eberth
1069:, and
1067:Eberth
1038:, and
1036:Eberth
965:Eberth
887:Eberth
765:Eberth
752:Eberth
717:Eberth
701:Eberth
509:splays
318:, and
54:Canada
493:birds
465:flood
328:creek
224:epoch
205:Hilda
191:Hilda
46:Hilda
1167:and
1025:504.
885:See
636:1998
577:and
560:and
499:and
478:and
434:, a
420:root
416:coal
316:fish
142:1997
138:1996
99:1966
97:and
95:1964
83:1959
31:The
646:or
136:In
81:In
48:in
1280::
1176:^
1094:^
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682:^
554:,
406:A
322:.
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