Prehistoric Park Animal Field Guide Volume 1

by WildExpert24

As a Prehistoric Park employee, you get the privilege to work with the likes of previously extinct animals. However, if you want to survive longer than five minutes, then you need to know its inhabitants. From the world of Cartoon's Prehistoric Park, this Guide will give you info on behavior, diet, lifespan, and more. Welcome to the Ultimate Prehistoric Guidebook.

20. Pachycephalosaurus

Pachycephalosaurus

Scientific Classification

Scientific Classification

Kingdom: Animalia

Phylum: Chordata

Clade: Dinosauria

Order: Ornithischia

Family: Pachycephalosauria

Subfamily: Pachycephalosauridae

Tribe: Pachycephalosaurini

Genus: Pachycephalosaurus

Described by Barnum Brown and Erich Maren Schlaikjer, 1943

Type Species: Pachycephalosaurus wyomingensis meaning "Thick-headed Lizard."

Synonyms:

-Tylosteus ornatus
Leidy, 1872 (rejected name)

-Troodon wyomingensis
Gilmore, 1931

-Pachycephalosaurus grangeri
Brown & Schlaikjer, 1943

-Pachycephalosaurus reinheimeri
Brown & Schlaikjer, 1943

-Stenotholus kohleri
Giffin, Gabriel & Johnson, 1988

-Stygimoloch spinifer?
Galton & Sues, 1983

-Dracorex hogwartsia?
Bakker et al., 2006

Current Park Population: (18; 12 adults, 6 youngsters; 6 male, 12 female)

Park Diet: Cycads, Ferns, Conifers, Apples, Banana leaves, mealworms, crickets, thawed mice, waxworms, ostrich feed, emu feed, and sheep feed.

Natural Diet: Cycads, Ferns, Conifers, small insects, and animals.

Lifespan: 28 years

Habitat: Open areas like floodplain swamps, fern prairies, semi-arid scrubland, and open-canopy forests with large amounts of food.

Native Ecosystem: Western North America, on what was then an island continent known as Laramidia. Hell Creek Formation, Lance Formation, Denver Formation, Scollard Formation, Southwestern Alberta, Canada, Montana, South Dakota, Wyoming, 70-66 Million Years Ago, Maastrichtian Stage.

Breeding Season: April-June

Gestation Period: Four-Five months

Eggs Laid: 8-20 eggs

Hatching Time: Three-Five weeks

Danger Level: Proceed with Caution, 8 out of 10.

Summary: One of the most unusual dinosaurs of the Cretaceous was the Pachycephalosaurus, known for its dome-shaped head. This bipedal herbivore became the center of debate between scientists in terms of what the head was used for and how some separate species are a single species. These were the bighorn sheep of the Cretaceous and they were quite ill-tempered towards anything they see as a threat.

History of Research:

Remains attributable to Pachycephalosaurus may have been found as early as the 1850s. As determined by Donald Baird, in 1859 or 1860, Ferdinand Vandeveer Hayden, an early fossil collector in the American West, collected a bone fragment in the vicinity of the head of the Missouri River, from what is now known to be the Lance Formation of southeastern Montana. This specimen, ANSP 8568, was described by Joseph Leidy in 1872 as belonging to the dermal armor of a reptile or an armadillo-like anima. It became known as Tylosteus. Its actual nature wasn't found until Baird studied it again over a century later and identified it as a squamosal (bone from the back of the skull) of Pachycephalosaurus, including a set of bony knobs corresponding to those found on other specimens of Pachycephalosaurus. Because the name Tylosteus predates Pachycephalosaurus, according to the International Code of Zoological Nomenclature Tylosteus would normally be preferred. In 1985, Baird successfully petitioned to have Pachycephalosaurus used instead of Tylosteus because the latter name had not been used for over fifty years, was based on undiagnostic materials, and had poor geographic and stratigraphic information. This may not be the end of the story, however. Robert Sullivan suggested in 2006 that ANSP 8568 is more like the corresponding bone of Dracorex than that of Pachycephalosaurus. The issue is of uncertain importance, though, if Dracorex represents a juvenile Pachycephalosaurus, as has been recently proposed.

In 1890, during the Bone Wars between Othniel Charles Marsh and Edward Drinker Cope, one of Marsh's collectors, John Bell Hatcher, collected a partial left squamosal (YPM VP 335) later referred to Stygimoloch spinifer near Lance Creek, Wyoming in the Lance Formation. Marsh described the squamosal along with the dermal armor of Denversaurus as the body armor of Triceratops in 1892, believing that the squamosal was a spike akin to the plates on Stegosaurus. The squamosal spike was even featured in Charles Knight's painting of Cope's ceratopsid Agathaumas, likely based on Marsh's hypothesis. Marsh also named a species of now-dubious ankylosaur Palaeoscincus in 1892 based on a single tooth (YPM 4810), collected by Hatcher from the Lance. The tooth was named Palaeoscinus latus, but in 1990, Coombs found the tooth to be from a pachycephalosaurid, possibly even Pachycephalosaurus itself. Hatcher also collected several additional teeth and skull fragments while working for Marsh, though these have yet to be described.

P. wyomingensis, the type and currently only valid species of Pachycephalosaurus, was named by Charles W. Gilmore in 1931. He coined it for the partial skull USNM 12031, from the Lance Formation of Niobrara County, Wyoming. Gilmore assigned his new species to Troodon as T. wyomingensis. At the time, paleontologists thought that Troodon, then known only from teeth, was the same as Stegoceras, which had similar teeth. Accordingly, what is now known as pachycephalosaurids were assigned to the family Troodontidae, a misconception that was not corrected until 1945 by Charles M. Sternberg.

In 1943, Barnum Brown and Erich Maren Schlaikjer, with newer, more complete material, established the genus Pachycephalosaurus. They named two species: Pachycephalosaurus grangeri, the type species of their new genus, and Pachycephalosaurus reinheimeri. P. grangeri was based on AMNH 1696, a nearly complete skull from the Hell Creek Formation of Ekalaka, Carter County, Montana. P. reinheimeri was based on what is now DMNS 469, a dome, and a few associated elements from the Lance Formation of Corson County, South Dakota. They also referred to the older species "Troodon" wyomingensis as their new genus. Their two newer species have been considered synonymous with P. wyomingensis since 1983.

In 2015, some pachycephalosaurid material and a domed parietal attributable to Pachycephalosaurus were discovered in the Scollard Formation of Alberta, implying that the dinosaurs of this era were cosmopolitan and didn't have discrete faunal provinces.

Description: Adults can be about ten feet long, covered with brown scaly skin with the upper part being dark brown with rows of black osteoderms on its body and tail on the scales, light underbelly, and a skin membrane behind their hind legs, gray cheek horns, Individuals have black markings, spots, and stripes over their bodies and dome heads, with bronze yellow long bristle-like quill filaments on the upper portion of their body and running down to the tails.

Males are brightly colored orange domes, taller spikes, dark blue faces and necks, an orange line running down the sides of the neck, a black neck collar patch, and a red-orange throat pouch

Females and young males had pale-colored dome heads and with the young males being pale orange. Females have smoother dome-shaped heads.

Adolescents have small horns on the tip of their noses, and long sharp-looking spikes surrounding the edges of their dome, but were flat, light brown with black stripes and spots and tan bristles.

Juveniles are tan along with their bristle quills with black stripes and spots.

Hatchlings are identical to the juveniles but are grayish brown.

Size: Pachycephalosaurus was bipedal and possibly the largest of all pachycephalosaurids. It has been estimated that Pachycephalosaurus was about 4.5 meters (14.8 ft) long and weighed about 370–450 kilograms (820–990 lb). Based on other pachycephalosaurids, it probably had a fairly short, thick neck, short arms, a bulky body, long legs, and a heavy tail that was likely held rigid by ossified tendons.

Skull: The anatomy of Pachycephalosaurus itself is poorly known, as only skull remains have been described. Pachycephalosaurus is famous for having a large, bony dome on top of its skull, up to 25 cm (10 in) thick, which safely cushioned its brain. The dome's rear aspect was edged with bony knobs and short bony spikes projected upwards from the snout. However, the spikes were probably blunted, not sharp.

The skull was short and possessed large, rounded eye sockets that faced forward, suggesting that the animal had binocular vision. Pachycephalosaurus had a small muzzle that ended in a pointed beak. The teeth were tiny, with leaf-shaped crowns. The head was supported by an "S"- or "U"-shaped neck. Younger individuals of Pachycephalosaurus might have had flatter skulls and larger horns projecting from the back of the skull. As the animal grew, the horns shrunk and rounded out as the dome grew.

Classification: Pachycephalosaurus gives its name to Pachycephalosauria, a clade of herbivorous ornithischian dinosaurs that lived during the Late Cretaceous period in North America and Asia. Despite their bipedal stance, they were a part of Marginocephalia, thus being likely more closely related to the ceratopsians than the ornithopods.

Pachycephalosaurus is the most famous member of Pachycephalosauria, even if it's not the best-preserved member. The clade also includes Stenopelix, Wannanosaurus, Goyocephale, Stegoceras, Homalocephale, Tylocephale, Sphaerotholus, and Prenocephale. Within the tribe, Pachycephalosaurini, Pachycephalosaurus is most closely related to Alaskacephale. Dracorex and Stygimoloch have also been synonymized with Pachycephalosaurus.

In 2010, Gregory S. Paul proposed that, while Stygimoloch and Dracorex possibly represent different growth stages of Pachycephalosaurus, Stygimoloch might represent a different species, P. spinifer. This idea has been regarded as a way of interpretation by Mark Witton and Thomas Holtz. A phylogenetic analysis from 2021 by Evans and colleagues accepted the validity of the genus Stygimoloch based on it being found in later rock layers than Pachycephalosaurus but agreed with the consensus that Dracorex represents an ontogimorph instead of a distinct taxon. However, David Evans himself noted in a Twitter post that he and his colleagues would also consider Stygimoloch as P. spinifer.

Based on the Research by Japanese Lead Scientist, Dr. Akio Yama has confirmed that Stygimoloch and Dracorex are life stages of Pachycephalosaurus based on DNA analysis.

Paleobiology

Social Behavior: Pachycephalosaurus live in harem herds with one Dominant Bull, seven to fifteen females or more led by a dominant female, one to four subordinate young males, sometimes the dominant males' brothers or sons, and their offspring.

There is also a dominant female and it's a hierarchy rank order from the large stronger high ranking females to the smaller low ranking females based on the flatness of their dome heads, All females of the herd take care of their young and will defend them from predators. The dominant male has to maintain order and control and whenever a male within the herd or outside the herd tries to take over, it results in a head-bashing clash which results in the loser being put in his place or exile. A lone Pachycephalosaurus is vulnerable without a herd due to the many predators in Hell Creek.

Living alone is dangerous for one Pachycephalosaurus who often avoids large predators like T. Rex and Dakotaraptor, and Males often live in bachelor herds which consist of males who left or are kicked out of their family herds and spar with one another to practice being dominant males.

Growth and ontogeny: Aside from Pachycephalosaurus itself, two other pachycephalosaurs were described from the latest Cretaceous of the northwestern United States: Stygimoloch spinifer ("thorny Moloch of the Styx") and Dracorex hogwartsia ("dragon king of Hogwarts"). The former is only known from a juvenile skull with a reduced dome and large spikes, while the latter, also known from only a juvenile skull, had a seemingly flat head with short horns. Due to their unique head ornamentation, they were seen as separate species for several years. However, in 2007, they were proposed to be juvenile or female morphologies of Pachycephalosaurus. At that year's meeting of the Society of Vertebrate Paleontology, Jack Horner of Montana State University presented evidence, from analysis of the skull of the Dracorex specimen, that it may be a juvenile form of Stygimoloch. In addition to this, he presented data that indicates that both Stygimoloch and Dracorex may be juvenile forms of Pachycephalosaurus. Horner and M.B. Goodwin published their findings in 2009, showing that the spike and skull dome bones of all three "species" exhibit extreme plasticity and that both Dracorex and Stygimoloch are known only from juvenile specimens, while Pachycephalosaurus is known only from adult specimens. These observations, in addition to the fact that all three forms lived in the same time and place, led them to conclude that Dracorex and Stygimoloch were simply juvenile Pachycephalosaurus, which lost spikes and grew domes as they aged. A 2010 study by Nick Longrich and colleagues also supported the hypothesis that all flat-skulled pachycephalosaur species were juveniles of the dome-headed adults, such as Goyocephale and Homalocephale.

The discovery of baby skulls assigned to Pachycephalosaurus that was described in 2016 from two different bone beds in the Hell Creek Formation has been presented as further evidence for this hypothesis. The fossils, as described by David Evans and Mark Goodwin et al are identical to all three supposed genera in the placement of the rugose knobs on their skulls, and the unique features of Stygimoloch and Dracorex are thus instead morphologically consistent features on a Pachycephalosaurus growth curve.

It has been noted that morphological differences between Stygimoloch and Pachycephalosaurus may also partly be due to slight stratigraphic differences. The few Stygimoloch specimens that have reliable stratigraphic data were all collected from the upper part of the Hell Creek Formation, whereas Pachycephalosaurus morphs were all collected from the lower part. This has also led to suggestions that Stygimoloch might represent its own species, P. spinifer. In their 2021 redescription of Sinocephale bexelli, Evans and his colleagues treated Stygimoloch (but not Dracorex) as a separate taxon based on their phylogenetic analysis. However, Evans himself has noted that he and his colleagues support the idea of P. spinifer.

Dome Function: It has been widely hypothesized for decades that Pachycephalosaurus and its relatives were the ancient, bipedal equivalents of bighorn sheep or musk oxen, where male individuals would ram each other headlong and they would horizontally straighten their head, neck, and body in order to transmit stress during ramming. However, there have also been alternative suggestions that the pachycephalosaurs could not have used their domes in this way.

The primary argument that has been raised against head-butting is that the skull roof may not have adequately sustained impact associated with ramming, as well as a lack of definitive evidence of scars or other damage on fossilized Pachycephalosaurus skulls. However, more recent analyses have uncovered such damage (see below). Furthermore, the cervical and anterior dorsal vertebrae show that the neck was carried in an "S"- or "U"-shaped curve, rather than a straight orientation and that it might have been unfit for transmitting stress from direct head-butting. Lastly, the rounded shape of the skull would lessen the contacted surface area during head-butting, resulting in glancing blows.

Alternatively, Pachycephalosaurus and other pachycephalosaurids may have engaged in flank-butting during intraspecific combat. In this scenario, an individual may have stood roughly parallel or faced a rival directly, using intimidation displays to cow its rival. If intimidation failed, the Pachycephalosaurus would bend its head downward and to the side, striking the rival on its flank. This hypothesis is supported by the relatively broad torso of most pachycephalosaurs, which would have protected vital organs from trauma. The flank-butting theory was first proposed by Sues in 1978 and expanded upon by Ken Carpenter in 1997.

In 2012, a study showed that cranial pathologies in a P. wyomingensis specimen were likely due to agonistic behavior. It was also proposed that similar damage in other pachycephalosaur specimens (previously explained as taphonomic artifacts and bone absorptions) may instead have been due to such behavior. Peterson et al. (2013) studied cranial pathologies among Pachycephalosauridae and found that 22% of all domes examined had lesions that are consistent with osteomyelitis, an infection of the bone resulting from penetrating trauma or trauma to the tissue overlying the skull that leads to an infection of the bone tissue. This high rate of pathology lends more support to the hypothesis that pachycephalosaurid domes were employed in intra-specific combat. Pachycephalosaurus wyomingensis specimen BMR P2001.4.5 was observed to have 23 lesions in its frontal bone and P. wyomingensis specimen DMNS 469 was observed to have 5 lesions. The frequency of trauma was comparable across the different genera in the pachycephalosaurid family, even though these genera vary concerning the size and architecture of their domes and the fact that they existed during varying geologic periods. These findings were in stark contrast with the results from analysis of the relatively flat-headed pachycephalosaurids, where there was an absence of pathology. This would support the hypothesis that these individuals represent either females or juveniles, where intra-specific combat behavior is not expected.

Histological examination reveals that pachycephalosaurid domes are composed of a unique form of fibrolamellar bone that contains fibroblasts, which play a critical role in wound healing and are capable of rapidly depositing bone during remodeling. Peterson et al. (2013) concluded that taken together, the frequency of lesion distribution and the bone structure of frontoparietal domes lends strong support to the hypothesis that pachycephalosaurids used their unique cranial structures for agonistic behavior. CT scan comparisons of the skulls of Stegoceras validum, Prenocephale prenes, and several head-striking artiodactyls have also supported pachycephalosaurids as being well-equipped for head-butting.

Based on our observations, we can confirm Pachycephalosaurus use head-butting and flank-hitting tactics, but based on a discovery in 2022, they use their tails as a tripod like a kangaroo and they slam their chests, wrestle with their arms, bite or hit one another with their heads, and kick with their back legs in a third tactic, kick-boxing.

Other functions of the dome could be used as a visual display to signal rank status, intimidate rivals, and attract mates, a battering ram to push down small trees for food, and ramming the side of predators.

Diet: Scientists do not yet know what these dinosaurs ate. Having very small, ridged teeth, they could not have chewed tough, fibrous plants like flowering shrubs as effectively as other dinosaurs of the same period. It is assumed that pachycephalosaurs lived on a mixed diet of leaves, seeds, and fruits. The sharp, serrated teeth would have been very effective for shredding plants. It has also been suspected to a degree that it may have included meat in its diet. The most complete fossil jaw shows that it had serrated blade-like front teeth, reminiscent of those of carnivorous theropods. The meat part of their diet would consist of Insects, small amphibians, reptiles, fish, and mammals. Sometimes they would scavenge dead carcasses and gnaw on bones for calcium.

Reproduction: Male Pachycephalosaurus would engage in kickboxing, head butting, and side-flanking each other in the heads, and sides, and kicking with their legs in the chest. During migration, herds of Pachycephalosaurus would gather, and young males would challenge dominant males to win the favor of allowing their daughters to join the young males to form a herd, sometimes a young male would overthrow the dominant male and after driving him out would become the new herd leader.

But there are sneaky males, young males that resemble females would go unnoticed as the male's rut, he would mate with a female behind their backs.

Paleoecology: Nearly all Pachycephalosaurus fossils have been recovered from the Lance Formation and Hell Creek Formation of the northwestern United States. Pachycephalosaurus possibly coexisted alongside additional pachycephalosaur species of the genera Sphaerotholus, as well as Dracorex and Stygimoloch, though these last two genera may represent different growth stages of Pachycephalosaurus itself. Other dinosaurs that shared its time and place include Thescelosaurus, the hadrosaurid, Edmontosaurus, and a possible species of Parasaurolophus, ceratopsians like Triceratops, Torosaurus, Nedoceratops, Tatankaceratops, and Leptoceratops, the ankylosaurid Ankylosaurus, the nodosaurids, Denversaurus and Edmontonia, and the theropods Acheroraptor, Dakotaraptor, Ornithomimus, Struthiomimus, Anzu, Leptorhynchos, Pectinodon, Paronychodon, Richardoestesia, and Tyrannosaurus.

Interactions with other species: They normally keep to themselves, but will form mixed-species herds with Triceratops, Torosaurus, Edmontosauurs, Ornithomimus, Thescelosaurus, and Ankylosaurus. But during times of drought over low water or food sources, they can be territorial and would nip or ram the other dinosaurs or they're in their way. Exceptions with the Edmontosaurus, Triceratops, Torosaurus, and Ankylosaurus, they demonstrate their strengths in size both in mass, and numbers, horns, frills, and club tails to tell the Pachys to back off.

They are hostile to predators even the juveniles and adolescents are no pushovers as they would mob together against small predators like Pectinodons and Acheroraptors. Mostly packs of Dromaeosaurus, Pectinodons, and Dakotaraptors can take down an adult Pachycephalosaurus although they must face the bash wrath from their dome heads of the herd.

One exception would be Tyrannosaurus Rex, Pachys could ram and drive away juveniles and adolescents, but an Adult even a pack of them, the pachys are no match for their sharp teeth and strong jaws along with the intelligence and pack-hunting behavior of the Tyrannosaurs.

There has been an observation of Batesian mimicry in two small other Pachycephalosaurs found in the same formation, Sphaerotholus buchholtzae and Platyholus. The Platyholus mimics the colors of the adolescent Pachycephalosaurs while Sphaerotholus mimics the colors of juvenile Pachycephalosaurus. The different shading of their bodies and their different colored dome shape heads is the best way to tell them apart. They often hang out with Pachycephalosaurus for protection as if they were their own offspring defending them from predators.

Extinction: Pachycephalosaurus might have used their heads for banging and displaying, but they never thought of how they would survive when the K-PG Extinction event came. They would soon succumb and suffer from starvation with the lack of plants as their main source of food same with the other herbivores like Edmontosaurus, Triceratops, Torosaurus, Ankylosaurus, Ornithomimus, and Thescelosaurus, although they could eat the insects and mammals, but wouldn't be enough for them.

Danger Tip: The Number#1 rule with Pachycephalosaurus is never to whistle loudly at them. They are highly sensitive to high-pitch noises and will charge at that threat and if you get too close it's even worse, they will ram you with their dome heads even at the vehicles and fences, and such an impact would leave you with broken bones or possibly death.

Significant Events: The Pachycephalosaurus herd sighted on the Rescue Team's second day alongside other herbivores including Edmontosaurus, Triceratops, Torosaurus, Ornithomimus, and Thescelosaurus gathered at a clearing with a creek close to camp during Day 2 of the Rescue Team's Mission, males were observed head-butting one another. The Next day, a pack of Tyrannosaurus attacked the multi-species herd, and the Pachycephalosaurus herd ran off from the large predators, a few defended themselves by ramming with their dome heads.

On the day when the asteroid hits, the Pachycephalosaurs joined by the Ornithomimus, and Thescelosaurus feeding on insects disturbed by the large feet of the large herbivores of Edmontosaurus, Triceratops, and Torosaurus, in the valley, are pursued by the Female T. Rex stampede down the hill and are funneled by the river on the left side and a wall of fallen logs and debris into the portal to the park. They now reside in the Hell Creek Herbivore Paddock.

Head Scientist Akio Yama, had the herd gathered at the holding pens to take samples of their skin, keratin, saliva, blood, and bristle filament from each individual for each life stage for DNA analysis before returning to their paddock. To test if Stygimoloch and Dracorex are the life stages of the same species, Pachycephalosaurus. It has been proven correct and he hopes to do the same with the other dinosaurs like T. Rex and Nannotyrannus

Hell Creek Herbivore Paddock: The Pachycephalosaurus herd lives alongside the other herbivores including Edmontosaurus, Triceratops, Torosaurus, and Ornithomimus in the large multi-species paddock. The Pachycephalosaurus is often seen in the fern plains and shrubland section of the paddock browsing and sparring with one another.

Notable Individuals:

Friar Tuck: He is the Dominant Male Pachycephalosaurus of the herd.

Belinda: A dominant Female Pachycephalosaurus and Friar Tuck's sister

Einstein: A young mischievous male Pachycephalosaurus, who loves apples, and pulls tricks with the staff. He forms a bond with Lynn Loud Jr.

Copernicus: A young female Pachycephalsoaurus that Einstein plays around with.

Conclusion: Pachycephalosaurus stands out as one of the most unusual dinosaurs both in the scientific community and in the public eye due to their bald dome heads used to ram and display. They make a great and bizarre addition to Paleo Park.

The Field Guide might take a long time, like structuring and writing descriptions of the creatures, but also my time in college and spending time with my family. So you can suggest additional information quotes, descriptions, and natural or speculative behaviors for the prehistoric animals that I can edit and you send your suggestions either in reviews or Private Messages.

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