The following is a link to a peer-reviewed paper, of an analysis of a
Cretaceous floodplain deposit which includes the remains of at least 4
tryrannosaurid individuals who likely died at the same time. This
suggests some degree of socialization, and the possibility of
pack-hunting behavior.

<https://peerj.com/articles/11013/>

The abstract:
**********************************************
Tyrannosaurids are hypothesized to be gregarious, possibly parasocial
carnivores engaging in cooperative hunting and extended parental care.
A tyrannosaurid (cf. Teratophoneus curriei) bonebed in the late
Campanian age Kaiparowits Formation of southern Utah, nicknamed the
Rainbows and Unicorns Quarry (RUQ), provides the first opportunity to
investigate possible tyrannosaurid gregariousness in a taxon unique to
southern Laramidia. Analyses of the site’s sedimentology, fauna,
flora, stable isotopes, rare earth elements (REE), charcoal content
and taphonomy suggest a complex history starting with the deaths and
transport of tyrannosaurids into a peri-fluvial, low-energy lacustrine
setting. Isotopic and REE analyses of the fossil material yields a
relatively homogeneous signature indicating the assemblage was derived
from the same source and represents a fauna living in a single
ecospace. Subsequent drying of the lake and fluctuating water tables
simultaneously overprinted the bones with pedogenic carbonate and
structurally weakened them through wet-dry cycling. Abundant charcoal
recovered from the primary bone layer indicate a low temperature fire
played a role in the site history, possibly triggering an avulsion
that exhumed and reburied skeletal material on the margin of a new
channel with minimal transport. Possible causes of mortality and
concentration of the tyrannosaurids include cyanobacterial toxicosis,
fire, and flooding, the latter being the preferred hypothesis.
Comparisons of the RUQ site with other North American tyrannosaur
bonebeds (Dry Island-Alberta; Daspletosaurus horneri-Montana) suggest
all formed through similar processes. Combined with ichnological
evidence, these tyrannosaur mass-burial sites could be part of an
emerging pattern throughout Laramidia reflecting innate tyrannosaurid
behavior such as habitual gregariousness
***********************************************

The Rainbows and Unicorns Quarry is one of three North American sites
which similarly preserve collections of multiple tyrannosaurids. These
sites are located on the coastal plains of Laramidia, a narrow stretch
of land between the Western Interior Seaway and the
uplifted regions of the early Laramide Orogeny, extending from the
Canadian Arctic and into Mexico.

On Monday, April 19, 2021 at 9:58:46 PM UTC-7, 69jp...@gmail.com wrote:
> The following is a link to a peer-reviewed paper, of an analysis of a
> Cretaceous floodplain deposit which includes the remains of at least 4
> tryrannosaurid individuals who likely died at the same time. This
> suggests some degree of socialization, and the possibility of
> pack-hunting behavior.
>
> <https://peerj.com/articles/11013/>
>
> The abstract:
> **********************************************
> Tyrannosaurids are hypothesized to be gregarious, possibly parasocial
> carnivores engaging in cooperative hunting and extended parental care.
> A tyrannosaurid (cf. Teratophoneus curriei) bonebed in the late
> Campanian age Kaiparowits Formation of southern Utah, nicknamed the
> Rainbows and Unicorns Quarry (RUQ), provides the first opportunity to
> investigate possible tyrannosaurid gregariousness in a taxon unique to
> southern Laramidia. Analyses of the site’s sedimentology, fauna,
> flora, stable isotopes, rare earth elements (REE), charcoal content
> and taphonomy suggest a complex history starting with the deaths and
> transport of tyrannosaurids into a peri-fluvial, low-energy lacustrine
> setting. Isotopic and REE analyses of the fossil material yields a
> relatively homogeneous signature indicating the assemblage was derived
> from the same source and represents a fauna living in a single
> ecospace. Subsequent drying of the lake and fluctuating water tables
> simultaneously overprinted the bones with pedogenic carbonate and
> structurally weakened them through wet-dry cycling. Abundant charcoal
> recovered from the primary bone layer indicate a low temperature fire
> played a role in the site history, possibly triggering an avulsion
> that exhumed and reburied skeletal material on the margin of a new
> channel with minimal transport. Possible causes of mortality and
> concentration of the tyrannosaurids include cyanobacterial toxicosis,
> fire, and flooding, the latter being the preferred hypothesis.
> Comparisons of the RUQ site with other North American tyrannosaur
> bonebeds (Dry Island-Alberta; Daspletosaurus horneri-Montana) suggest
> all formed through similar processes. Combined with ichnological
> evidence, these tyrannosaur mass-burial sites could be part of an
> emerging pattern throughout Laramidia reflecting innate tyrannosaurid
> behavior such as habitual gregariousness
> ***********************************************
>
> The Rainbows and Unicorns Quarry is one of three North American sites
> which similarly preserve collections of multiple tyrannosaurids. These
> sites are located on the coastal plains of Laramidia, a narrow stretch
> of land between the Western Interior Seaway and the
> uplifted regions of the early Laramide Orogeny, extending from the
> Canadian Arctic and into Mexico.

Interesting find. Note that Teratophoneus curriei is not the same animal as the more
famous Tyrannosaurus rex. (The former is considerable smaller, although it is a sizeable
critter). They are not coeval, with T rex coming probably several million years later. The paper
presents a reasonable argument that the animals in question *may* have been gregarious. They
were buried together at the same time. If they were flood concentrated, they have may have been
considerably separated in life, but probably not by large distances. "Not inconsistent" with
gregariousness, but but not conclusive seems the right call.

On Tue, 20 Apr 2021 21:29:22 -0700 (PDT), erik simpson
<eastside.erik@gmail.com> wrote:

>On Monday, April 19, 2021 at 9:58:46 PM UTC-7, 69jp...@gmail.com wrote:
>> The following is a link to a peer-reviewed paper, of an analysis of a
>> Cretaceous floodplain deposit which includes the remains of at least 4
>> tryrannosaurid individuals who likely died at the same time. This
>> suggests some degree of socialization, and the possibility of
>> pack-hunting behavior.
>>
>> <https://peerj.com/articles/11013/>
>>
>> The abstract:
>> **********************************************
>> Tyrannosaurids are hypothesized to be gregarious, possibly parasocial
>> carnivores engaging in cooperative hunting and extended parental care.
>> A tyrannosaurid (cf. Teratophoneus curriei) bonebed in the late
>> Campanian age Kaiparowits Formation of southern Utah, nicknamed the
>> Rainbows and Unicorns Quarry (RUQ), provides the first opportunity to
>> investigate possible tyrannosaurid gregariousness in a taxon unique to
>> southern Laramidia. Analyses of the site’s sedimentology, fauna,
>> flora, stable isotopes, rare earth elements (REE), charcoal content
>> and taphonomy suggest a complex history starting with the deaths and
>> transport of tyrannosaurids into a peri-fluvial, low-energy lacustrine
>> setting. Isotopic and REE analyses of the fossil material yields a
>> relatively homogeneous signature indicating the assemblage was derived
>> from the same source and represents a fauna living in a single
>> ecospace. Subsequent drying of the lake and fluctuating water tables
>> simultaneously overprinted the bones with pedogenic carbonate and
>> structurally weakened them through wet-dry cycling. Abundant charcoal
>> recovered from the primary bone layer indicate a low temperature fire
>> played a role in the site history, possibly triggering an avulsion
>> that exhumed and reburied skeletal material on the margin of a new
>> channel with minimal transport. Possible causes of mortality and
>> concentration of the tyrannosaurids include cyanobacterial toxicosis,
>> fire, and flooding, the latter being the preferred hypothesis.
>> Comparisons of the RUQ site with other North American tyrannosaur
>> bonebeds (Dry Island-Alberta; Daspletosaurus horneri-Montana) suggest
>> all formed through similar processes. Combined with ichnological
>> evidence, these tyrannosaur mass-burial sites could be part of an
>> emerging pattern throughout Laramidia reflecting innate tyrannosaurid
>> behavior such as habitual gregariousness
>> ***********************************************
>>
>> The Rainbows and Unicorns Quarry is one of three North American sites
>> which similarly preserve collections of multiple tyrannosaurids. These
>> sites are located on the coastal plains of Laramidia, a narrow stretch
>> of land between the Western Interior Seaway and the
>> uplifted regions of the early Laramide Orogeny, extending from the
>> Canadian Arctic and into Mexico.
>
>Interesting find. Note that Teratophoneus curriei is not the same animal as the more
>famous Tyrannosaurus rex. (The former is considerable smaller, although it is a sizeable
>critter). They are not coeval, with T rex coming probably several million years later. The paper
>presents a reasonable argument that the animals in question *may* have been gregarious. They
>were buried together at the same time. If they were flood concentrated, they have may have been
>considerably separated in life, but probably not by large distances. "Not inconsistent" with
>gregariousness, but but not conclusive seems the right call.

I noted the abstract's liberal use of "tyrannosaurid", and assumed it
was due to the authors' desires to associate this site with other
tyrannosaurid mass burials, even though they are of different species.

While reading the article, I recalled several extant species which
occasionally come together to take advantage of a large feeding
opportunity, ex. grizzly bears, crocodiles, but don't hunt
co-operatively. So it's not too surprising that extinct predators
would have behaved similarly.

Laramidia extended over a huge range of latitude, and so provided
several diverse habitats. My impression is RUQ was a floodplain with
meandering rivers with seasonal flooding and drying, similar to some
regions of modern Africa.

Also, Wikipedia tells me I should have referred to Sevier Orogeny and
not Laramide Orogeny.

On Wed, 21 Apr 2021 06:34:12 -0400, jillery <69jpil69@gmail.com>
wrote:

>On Tue, 20 Apr 2021 21:29:22 -0700 (PDT), erik simpson
><eastside.erik@gmail.com> wrote:
>
>>On Monday, April 19, 2021 at 9:58:46 PM UTC-7, 69jp...@gmail.com wrote:
>>> The following is a link to a peer-reviewed paper, of an analysis of a
>>> Cretaceous floodplain deposit which includes the remains of at least 4
>>> tryrannosaurid individuals who likely died at the same time. This
>>> suggests some degree of socialization, and the possibility of
>>> pack-hunting behavior.
>>>
>>> <https://peerj.com/articles/11013/>
>>>
>>> The abstract:
>>> **********************************************
>>> Tyrannosaurids are hypothesized to be gregarious, possibly parasocial
>>> carnivores engaging in cooperative hunting and extended parental care.
>>> A tyrannosaurid (cf. Teratophoneus curriei) bonebed in the late
>>> Campanian age Kaiparowits Formation of southern Utah, nicknamed the
>>> Rainbows and Unicorns Quarry (RUQ), provides the first opportunity to
>>> investigate possible tyrannosaurid gregariousness in a taxon unique to
>>> southern Laramidia. Analyses of the site’s sedimentology, fauna,
>>> flora, stable isotopes, rare earth elements (REE), charcoal content
>>> and taphonomy suggest a complex history starting with the deaths and
>>> transport of tyrannosaurids into a peri-fluvial, low-energy lacustrine
>>> setting. Isotopic and REE analyses of the fossil material yields a
>>> relatively homogeneous signature indicating the assemblage was derived
>>> from the same source and represents a fauna living in a single
>>> ecospace. Subsequent drying of the lake and fluctuating water tables
>>> simultaneously overprinted the bones with pedogenic carbonate and
>>> structurally weakened them through wet-dry cycling. Abundant charcoal
>>> recovered from the primary bone layer indicate a low temperature fire
>>> played a role in the site history, possibly triggering an avulsion
>>> that exhumed and reburied skeletal material on the margin of a new
>>> channel with minimal transport. Possible causes of mortality and
>>> concentration of the tyrannosaurids include cyanobacterial toxicosis,
>>> fire, and flooding, the latter being the preferred hypothesis.
>>> Comparisons of the RUQ site with other North American tyrannosaur
>>> bonebeds (Dry Island-Alberta; Daspletosaurus horneri-Montana) suggest
>>> all formed through similar processes. Combined with ichnological
>>> evidence, these tyrannosaur mass-burial sites could be part of an
>>> emerging pattern throughout Laramidia reflecting innate tyrannosaurid
>>> behavior such as habitual gregariousness
>>> ***********************************************
>>>
>>> The Rainbows and Unicorns Quarry is one of three North American sites
>>> which similarly preserve collections of multiple tyrannosaurids. These
>>> sites are located on the coastal plains of Laramidia, a narrow stretch
>>> of land between the Western Interior Seaway and the
>>> uplifted regions of the early Laramide Orogeny, extending from the
>>> Canadian Arctic and into Mexico.
>>
>>Interesting find. Note that Teratophoneus curriei is not the same animal as the more
>>famous Tyrannosaurus rex. (The former is considerable smaller, although it is a sizeable
>>critter). They are not coeval, with T rex coming probably several million years later. The paper
>>presents a reasonable argument that the animals in question *may* have been gregarious. They
>>were buried together at the same time. If they were flood concentrated, they have may have been
>>considerably separated in life, but probably not by large distances. "Not inconsistent" with
>>gregariousness, but but not conclusive seems the right call.
>
>
>I noted the abstract's liberal use of "tyrannosaurid", and assumed it
>was due to the authors' desires to associate this site with other
>tyrannosaurid mass burials, even though they are of different species.
>
>While reading the article, I recalled several extant species which
>occasionally come together to take advantage of a large feeding
>opportunity, ex. grizzly bears, crocodiles, but don't hunt
>co-operatively. So it's not too surprising that extinct predators
>would have behaved similarly.
>
>Laramidia extended over a huge range of latitude, and so provided
>several diverse habitats. My impression is RUQ was a floodplain with
>meandering rivers with seasonal flooding and drying, similar to some
>regions of modern Africa.
>
>Also, Wikipedia tells me I should have referred to Sevier Orogeny and
>not Laramide Orogeny.

Related to the OP is this older video I only recently noticed. It's
an hour-long lecture by Dr. Scott Sampson sponsored by the Denver
Museum of Nature and Science, and titled "Dinosaurs of the Lost
Continent", alluding to Burrough's literary work to refer to
Laramidia.

<https://www.youtube.com/watch?v=BBFw9ymd78k>

A relevant highlight is his description of Laramidia's productive
ecology. Despite its relatively small area compared to modern
continents, it was populated by over two dozen species whose adult
size exceeded 1000 kg.

There were many different ecosystems in Laramidia, from the Arctic to
the Gulf, and each ecosystem supported a tyrannosaurid, a ceratopsian,
a hadrosaur, etc, but each ecosystem had a different species
representative from those families, likely filling similar roles
within the different ecosystems. This may be why 3 different North
American lagerstatten contain different tyrannosaurid species.