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Description
Torosaurus latus

At the end of the Cretaceous, large-bodied ceratopsids were the most numerous herbivorous dinosaurs from Western North America (also known as Laramidia). During the last two million years of the Mesozoic, a tribe of Chasmosaurines known as Triceratopsins was the most common. Inhabiting the various ecosystems from as far north as Canada to as far south as Mexico.
Triceratopsins grew to larger sizes than other Ceratopsids, but unique to this group was an evolutionary trend where they began to solidify their frill structure. Rather than having massive "gaps" or "holes" in their frills (known as Fenestra) their frill would be comprised of solid bone.

One of the most unique, and some would consider a controversial member of this Chasmosaurine tribe is Torosaurus latus.

History and Naming:

Torosaurus was a byproduct of the infamous Bone Wars in the late 1800s. The feud between Othniel Charles Marsh and Edward Drinker Cope to see who could describe the most species from the fossil record. Ultimately, while many iconic dinosaurs from North America were described, it ruined the reputation of both men and left a black mark on American Paleontology that would remain decades after the two men passed away.
In 1891, Fossil Hunter John Bell Hatcher uncovered a pair of frills in Southeastern Wyoming. He sent them to his employer, O.C. Marsh for description. Both paleontologists identified the fossils as ceratopsid frills and they both had rather pronounced fenestra on the frills.
Marsh named two distinct ceratopsid species from the specimens. The first, and more complete skull he dubbed, "Torosaurus latus". The genus name means "Perforated Lizard". Whereas the species name means "wide one", thus, its name means "Wide Perforated Lizard". He also described the second frill as "Torosaurus gladius" meaning "Sword Perforated Lizard". Mainly because he thought the elongated squamosal (frill) signified an additional species, but it was later assigned back to T.latus.
It's been frequently also called "bull lizard" because the prefix of the genus name has been attributed to "Toro" meaning bull in Spanish and derived from the Latin word "Taurus". However, it's likely Marsh attributed the genus name to the Greek word "Toreo" meaning perforation after the large fenestra in the skull.
An additional species, Torosaurus utahensis has also been named. Described in 1946 from fossils found in Utah, where it derives its species name from. Fossils have also been found in more southern regions like New Mexico. The biggest difference is that it's smaller than T.latus, and a review of the species from 2005 suggests that it's older than T.latus. However, as of 2021, no further analysis has been given to these fossils to consider if these are distinctive, a growth stage of T.latus or another, more familiar ceratopsid (as will be discussed later).

As previously stated, Torosaurus is unique among Triceratopsins in that it has pronounced fenestra in the frills of specimens. Reminiscent of their older Chasmosaurine relatives. Their subfamily name literally means "opening/hollow lizards" in reference to their fenestra in their frills. However, Torosaurus retains this trait from its more basal cousins (albeit with less prominent fenestra). Whereas other Triceratopsins such as Triceratops began to have frills that were comprised of solidified bone.
The size of the fenestra varies from specimen to specimen. However, they greatly increase the size of the frill and the skull itself. In fact, T.latus possesses the largest skull of any known terrestrial vertebrate, with the largest skulls reaching 10ft.
Furthermore, in some specimens, while some have rostral (nasal) horns, a lot of the skulls have had their rostral horns compressed into growths of bone, also known as "bosses". Reminiscent to their distant Centrosaurine relative Pachyrhinosaurus. The shape of their brow horns varied from individual to individual as well. However, for the most part, the horns were straight and tapered to curving forward toward the tips of the horns.

Description:

In terms of size, they have roughly the same dimensions as their contemporary cousin, Triceratops. However, most estimates put them lower in terms of mass. Modern estimates place the mass of Triceratops around 8-10 tons, however, Torosaurus clocks in at around 6.5 tons.
Their habitat would have been lush floodplains and conifer forests of various Maastrichtian ecosystems from as far north as Canada to as far south as Texas and New Mexico.
In terms of predators, in Hell Creek (where most Torosaurus skeletons have been found) their primary predator would have been Tyrannosaurus rex. In fact, in 2020, a recent discovery of a small Torosaurus specimen; specimen number: DMNS EPV. 128000, dubbed "Tiny" was put on display in the Denver Museum of Natural History. Found in association with it was a T.rex tooth. Juveniles could have also been preyed upon by Dromaeosaurs like Dakotaraptor and the various crocodilians that inhabited the rivers of the various habitats.
Their jaws were similar to other Ceratopsids. Tipped with a beak and batteries of teeth designed to process fibrous plants. Their diet would have consisted of cycad, horsetail, and palm trees.
It has been assumed that they used their massive frills and horns for display and intimidation towards predators or rivals during mating or territorial disputes. However, it should be noted that no evidence of intraspecific combat has been on Torosaurus skulls. Thus, it's not clear if they locked horns as posited in other ceratopsids such as their cousin Triceratops, or as shown in the documentary series, Walking With Dinosaurs. However, since evidence of this behavior was found in Triceratops, it could be inferred Torosaurus did this as well.

Toroceratops, a debate that led to nowhere:

In recent years, some in the paleontological community have called into question the validity of the type species, Torosaurus latus, and think it is not a distinctive species.

In 2010, a study published by the famous Dr.Jack Horner and his graduate student John Scannella from Montana State University proposed that Triceratops and Torosaurus were in fact ontogenetic morphs of the same species. Torosaurus would represent the fully grown ontogenetic stage of Triceratops. This story was misread by people online and in the media and caused a flurry of reports stating that "Triceratops does not exist!". However, if this was true, this would just make Torosaurus synonymous with Triceratops given that Triceratops was described in 1889, thus the older name would take precedent over Torosaurus.
They based their study primarily on the various Torosaurus and Triceratops skulls in their collection at the Museum of the Rockies. They noted that Torosaurus have more mature and developed bone structure than Triceratops. Whereas the Triceratops in their collection has immature bone. Given that Triceratops has been shown to change drastically while they mature, they hypothesized that it was not beyond reason that the skull could have changed, even more, resulting in a so-called "Toromorph" for older Triceratops.
Furthermore, another ceratopsid, "Nedoceratops hatcheri" has been proposed as a transitional form between Triceratops and Torosaurus. With the individual having fenestra in on the sides of its frill. Scannella proposed that this was where the fenestra was starting to form on the side of the frill and as the subadult Triceratops mature into fully grown adults, the hole would shift to the center. It seemed that Torosaurus would just be a synonym of Triceratops and another example of the taxonomic mess made during the Bone Wars.

Two years later, paleontologist Dr.Nicholas Longrich from Yale performed an analysis of other Triceratops and Torosaurus skulls in an attempt to refute Horner and Scannella's Toromorph theory.

Through the principle of falsification, for Torosaurus to be an ontogenetic morph of triceratops, three predictions had to be met:
First and foremost, they had to overlap in range. For the most part, this was granted by Longrich. While both Triceratops and Torosaurus overlap in the Rockies and Northern plains such as the Hell Creek and parts of Canada like the Frenchman Formation, Triceratops are absent from the south. However, poor sampling and preservation could be attributed to this fact. Most fossils from the American South, even in large formations like Ojo Alamo are fragmentary. So Longrich stated this condition was met given that they could overlap.
The second point was that all Torosaurus had to be mature adults and Triceratops had to be immature subadults. Longrich pointed out that there were mature Triceratops specimens. Their bones had fully fused and were shown to be mature. Specifically, he used a fossil skull; specimen number: YPM 1822 which was a fully grown Triceratops prorsus specimen and was shown to be ontogenetically mature. In terms of Torosaurus specimens, Longrich found that one of the specimens of Torosaurus at Yale; specimen number: YPM 1831 was shown to be immature. Mainly because the rostral bone was unfused as were the sides of the skull and the texture of the skull was indicative of immature bone. He concluded this part of the theory was not met.
Finally, and most importantly, there had to be good transitional forms: Longrich noted that the Nedoceratops specimen was a diseased individual of its own species. The reason being is that the fenestra is asymmetric on the skull, even for a fossil specimen where distortions are common after millions of years in the ground. It was found that the fenestra did not emerge gradually and pierce through thin bone as would be expected if this was ontogenetic changes, but was surrounded by thick, swollen bone growths. They proposed that this was not a growth stage, but an individual who had its frill pierced, possibly during an altercation in its life or just a diseased individual. No other viable transitional forms have been put forward, so Longrich determined that this point was not met.

Thus, Longrich and his colleagues determined that Torosaurus was a valid species of Ceratopsid and not a growth stage of Triceratops.

Future studies on the recently described Tiny and other specimens that are being unearthed across America could help clear up this theory. On Tiny itself, its age has not been determined, however, given that it's smaller than other specimens, it could be a juvenile individual and offer more insight into Torosaurus ontogeny.

Whatever its status as a species, Torosaurus remains a unique and iconic dinosaur from Late Cretaceous North America. And the debate around its synonymy with Triceratops shows the arguments and debates paleontologists conduct when researching these long-dead animals.
___________________________________________________________________________________________

NOTE: OUTDATED. Proper Profile see here:

So, I never did Torosaurus on its own, and the more I read up on it, and with newer discoveries of this interesting dinosaur, thought I'd give it its own profile.

I actually did do some changes from my old model from my ontogeny series for Torosaurus and I updated it as well with newer models.
Torosaurus Growth Series by Davidy12 on DeviantArt

I hope this offers the best insight as to why Torosaurus should be considered a distinct species of ceratopsid and not just a growth stage for Triceratops.

This was one of my favorite dinosaurs growing up and I'm so glad I got to depict it in a profile and eventually in Past Meets Present.

In terms of the changes I made, I gave the adult a more prominent boss on its rostrum, changed the frill shape slightly, and boom got a better and more accurate Torosaurus model.

Original Triceratops by Tyranachu:
Triceratops (Tyranachu) | ZT2 Download Library Wiki | Fandom

Skin taken inspiration from cisiopurple and model has been modified by me.

For Past Meets Present:
Past Meets Present (Pt4 is Up) - The ZT2 Round Table

Description
Torosaurus latus

At the end of the Cretaceous, large-bodied ceratopsids were the most numerous herbivorous dinosaurs from Western North America (also known as Laramidia). During the last two million years of the Mesozoic, a tribe of Chasmosaurines known as Triceratopsins was the most common. Inhabiting the various ecosystems from as far north as Canada to as far south as Mexico.
Triceratopsins grew to larger sizes than other Ceratopsids, but unique to this group was an evolutionary trend where they began to solidify their frill structure. Rather than having massive "gaps" or "holes" in their frills (known as Fenestra) their frill would be comprised of solid bone.

One of the most unique, and some would consider a controversial member of this Chasmosaurine tribe is Torosaurus latus.

History and Naming:

Torosaurus was a byproduct of the infamous Bone Wars in the late 1800s. The feud between Othniel Charles Marsh and Edward Drinker Cope to see who could describe the most species from the fossil record. Ultimately, while many iconic dinosaurs from North America were described, it ruined the reputation of both men and left a black mark on American Paleontology that would remain decades after the two men passed away.
In 1891, Fossil Hunter John Bell Hatcher uncovered a pair of frills in Southeastern Wyoming. He sent them to his employer, O.C. Marsh for description. Both paleontologists identified the fossils as ceratopsid frills and they both had rather pronounced fenestra on the frills.
Marsh named two distinct ceratopsid species from the specimens. The first, and more complete skull he dubbed, "Torosaurus latus". The genus name means "Perforated Lizard". Whereas the species name means "wide one", thus, its name means "Wide Perforated Lizard". He also described the second frill as "Torosaurus gladius" meaning "Sword Perforated Lizard". Mainly because he thought the elongated squamosal (frill) signified an additional species, but it was later assigned back to T.latus.
It's been frequently also called "bull lizard" because the prefix of the genus name has been attributed to "Toro" meaning bull in Spanish and derived from the Latin word "Taurus". However, it's likely Marsh attributed the genus name to the Greek word "Toreo" meaning perforation after the large fenestra in the skull.
An additional species, Torosaurus utahensis has also been named. Described in 1946 from fossils found in Utah, where it derives its species name from. Fossils have also been found in more southern regions like New Mexico. The biggest difference is that it's smaller than T.latus, and a review of the species from 2005 suggests that it's older than T.latus. However, as of 2021, no further analysis has been given to these fossils to consider if these are distinctive, a growth stage of T.latus or another, more familiar ceratopsid (as will be discussed later).

As previously stated, Torosaurus is unique among Triceratopsins in that it has pronounced fenestra in the frills of specimens. Reminiscent of their older Chasmosaurine relatives. Their subfamily name literally means "opening/hollow lizards" in reference to their fenestra in their frills. However, Torosaurus retains this trait from its more basal cousins (albeit with less prominent fenestra). Whereas other Triceratopsins such as Triceratops began to have frills that were comprised of solidified bone.
The size of the fenestra varies from specimen to specimen. However, they greatly increase the size of the frill and the skull itself. In fact, T.latus possesses the largest skull of any known terrestrial vertebrate, with the largest skulls reaching 10ft.
Furthermore, in some specimens, while some have rostral (nasal) horns, a lot of the skulls have had their rostral horns compressed into growths of bone, also known as "bosses". Reminiscent to their distant Centrosaurine relative Pachyrhinosaurus. The shape of their brow horns varied from individual to individual as well. However, for the most part, the horns were straight and tapered to curving forward toward the tips of the horns.

Description:

In terms of size, they have roughly the same dimensions as their contemporary cousin, Triceratops. However, most estimates put them lower in terms of mass. Modern estimates place the mass of Triceratops around 8-10 tons, however, Torosaurus clocks in at around 6.5 tons.
Their habitat would have been lush floodplains and conifer forests of various Maastrichtian ecosystems from as far north as Canada to as far south as Texas and New Mexico.
In terms of predators, in Hell Creek (where most Torosaurus skeletons have been found) their primary predator would have been Tyrannosaurus rex. In fact, in 2020, a recent discovery of a small Torosaurus specimen; specimen number: DMNS EPV. 128000, dubbed "Tiny" was put on display in the Denver Museum of Natural History. Found in association with it was a T.rex tooth. Juveniles could have also been preyed upon by Dromaeosaurs like Dakotaraptor and the various crocodilians that inhabited the rivers of the various habitats.
Their jaws were similar to other Ceratopsids. Tipped with a beak and batteries of teeth designed to process fibrous plants. Their diet would have consisted of cycad, horsetail, and palm trees.
It has been assumed that they used their massive frills and horns for display and intimidation towards predators or rivals during mating or territorial disputes. However, it should be noted that no evidence of intraspecific combat has been on Torosaurus skulls. Thus, it's not clear if they locked horns as posited in other ceratopsids such as their cousin Triceratops, or as shown in the documentary series, Walking With Dinosaurs. However, since evidence of this behavior was found in Triceratops, it could be inferred Torosaurus did this as well.

Toroceratops, a debate that led to nowhere:

In recent years, some in the paleontological community have called into question the validity of the type species, Torosaurus latus, and think it is not a distinctive species.

In 2010, a study published by the famous Dr.Jack Horner and his graduate student John Scannella from Montana State University proposed that Triceratops and Torosaurus were in fact ontogenetic morphs of the same species. Torosaurus would represent the fully grown ontogenetic stage of Triceratops. This story was misread by people online and in the media and caused a flurry of reports stating that "Triceratops does not exist!". However, if this was true, this would just make Torosaurus synonymous with Triceratops given that Triceratops was described in 1889, thus the older name would take precedent over Torosaurus.
They based their study primarily on the various Torosaurus and Triceratops skulls in their collection at the Museum of the Rockies. They noted that Torosaurus have more mature and developed bone structure than Triceratops. Whereas the Triceratops in their collection has immature bone. Given that Triceratops has been shown to change drastically while they mature, they hypothesized that it was not beyond reason that the skull could have changed, even more, resulting in a so-called "Toromorph" for older Triceratops.
Furthermore, another ceratopsid, "Nedoceratops hatcheri" has been proposed as a transitional form between Triceratops and Torosaurus. With the individual having fenestra in on the sides of its frill. Scannella proposed that this was where the fenestra was starting to form on the side of the frill and as the subadult Triceratops mature into fully grown adults, the hole would shift to the center. It seemed that Torosaurus would just be a synonym of Triceratops and another example of the taxonomic mess made during the Bone Wars.

Two years later, paleontologist Dr.Nicholas Longrich from Yale performed an analysis of other Triceratops and Torosaurus skulls in an attempt to refute Horner and Scannella's Toromorph theory.

Through the principle of falsification, for Torosaurus to be an ontogenetic morph of triceratops, three predictions had to be met:
First and foremost, they had to overlap in range. For the most part, this was granted by Longrich. While both Triceratops and Torosaurus overlap in the Rockies and Northern plains such as the Hell Creek and parts of Canada like the Frenchman Formation, Triceratops are absent from the south. However, poor sampling and preservation could be attributed to this fact. Most fossils from the American South, even in large formations like Ojo Alamo are fragmentary. So Longrich stated this condition was met given that they could overlap.
The second point was that all Torosaurus had to be mature adults and Triceratops had to be immature subadults. Longrich pointed out that there were mature Triceratops specimens. Their bones had fully fused and were shown to be mature. Specifically, he used a fossil skull; specimen number: YPM 1822 which was a fully grown Triceratops prorsus specimen and was shown to be ontogenetically mature. In terms of Torosaurus specimens, Longrich found that one of the specimens of Torosaurus at Yale; specimen number: YPM 1831 was shown to be immature. Mainly because the rostral bone was unfused as were the sides of the skull and the texture of the skull was indicative of immature bone. He concluded this part of the theory was not met.
Finally, and most importantly, there had to be good transitional forms: Longrich noted that the Nedoceratops specimen was a diseased individual of its own species. The reason being is that the fenestra is asymmetric on the skull, even for a fossil specimen where distortions are common after millions of years in the ground. It was found that the fenestra did not emerge gradually and pierce through thin bone as would be expected if this was ontogenetic changes, but was surrounded by thick, swollen bone growths. They proposed that this was not a growth stage, but an individual who had its frill pierced, possibly during an altercation in its life or just a diseased individual. No other viable transitional forms have been put forward, so Longrich determined that this point was not met.

Thus, Longrich and his colleagues determined that Torosaurus was a valid species of Ceratopsid and not a growth stage of Triceratops.

Future studies on the recently described Tiny and other specimens that are being unearthed across America could help clear up this theory. On Tiny itself, its age has not been determined, however, given that it's smaller than other specimens, it could be a juvenile individual and offer more insight into Torosaurus ontogeny.

Whatever its status as a species, Torosaurus remains a unique and iconic dinosaur from Late Cretaceous North America. And the debate around its synonymy with Triceratops shows the arguments and debates paleontologists conduct when researching these long-dead animals.
___________________________________________________________________________________________

NOTE: OUTDATED. Proper Profile see here:

So, I never did Torosaurus on its own, and the more I read up on it, and with newer discoveries of this interesting dinosaur, thought I'd give it its own profile.

I actually did do some changes from my old model from my ontogeny series for Torosaurus and I updated it as well with newer models.
Torosaurus Growth Series by Davidy12 on DeviantArt

I hope this offers the best insight as to why Torosaurus should be considered a distinct species of ceratopsid and not just a growth stage for Triceratops.

This was one of my favorite dinosaurs growing up and I'm so glad I got to depict it in a profile and eventually in Past Meets Present.

In terms of the changes I made, I gave the adult a more prominent boss on its rostrum, changed the frill shape slightly, and boom got a better and more accurate Torosaurus model.

Original Triceratops by Tyranachu:
Triceratops (Tyranachu) | ZT2 Download Library Wiki | Fandom

Skin taken inspiration from cisiopurple and model has been modified by me.

For Past Meets Present:
Past Meets Present (Pt4 is Up) - The ZT2 Round Table