Mina the Parasaurolophus

Mina the Parasaurolophus

## Mina

Mina the Parasaurolophus Mina has a Green body. She has a Blue-crested Mina. She has a daughter named Mallow. Mina takes care of her daughter, Mallow.

Mina, 20 years old, works clean all the time. Mina is a Thai actress who makes merit. Mina has a beautiful face and likes to sing all the time.

## Information

***Parasaurolophus*** (/ˌpærəsɔːˈrɒləfəs, -ˌsɔːrəˈloʊfəs/; meaning "near crested lizard" in reference to *Saurolophus)* is a genus of hadrosaurid "duck-billed" dinosaur that lived in what is now western North America and possibly Asia during the Late Cretaceous period, about 76.5–73 million years ago. It was a large herbivore that could reach over 9 metres (30 ft) long and weigh over 5 metric tons (5.5 short tons), and were able to move as a biped and a quadruped. Three species are universally recognized: ***P. walkeri*** (the type species), ***P. tubicen***, and the short-crested ***P. cyrtocristatus***. Additionally, a fourth species, *P. jiayinensis*, has been proposed, although it is more commonly placed in the separate genus *Charonosaurus*. Remains are known from Alberta, New Mexico, and Utah, as well as possibly Heilongjiang if *Charonosaurus* is in fact part of the genus. The genus was first described in 1922 by William Parks from a skull and partial skeleton found in Alberta.

*Parasaurolophus* was a hadrosaurid, part of a diverse family of large Late Cretaceous ornithopods that are known for their range of bizarre head adornments, which were likely used for communication and increased hearing. This genus is known for its large, elaborate cranial crest, which forms a long curved tube projecting upwards and back from the skull in its largest form. *Charonosaurus* from China, which may have been its closest relative, had a similar skull and a potentially similar crest. Visual recognition of both species and sex, acoustic resonance, and thermoregulation have been proposed as functional explanations for the crest. It is one of the rarer hadrosaurids, known from only a handful of good specimens.

## Discovery and naming[edit]

Meaning "near crested lizard", the name *Parasaurolophus* is derived from the Greek words *para*/παρα ("beside" or "near"), *saurus*/σαυρος ("lizard"), and *lophos*/λοφος ("crest"). It is based on ROM 768, a skull and partial skeleton missing most of the tail and the back legs below the knees, which was found by a field party from the University of Toronto in 1920 near Sand Creek along the Red Deer River in Alberta. These rocks are now known as the Campanian age Late Cretaceous Dinosaur Park Formation. William Parks named the specimen *P. walkeri* in honor of Sir Byron Edmund Walker, the chairman of the Board of Trustees of the Royal Ontario Museum. *Parasaurolophus* remains are rare in Alberta, with only one other partial skull that is possibly from the Dinosaur Park Formation and three Dinosaur Park specimens lacking their skulls that possibly belong to the genus. In some faunal lists, there is a mention of possible *P. walkeri* material in the Hell Creek Formation of Montana, a rock unit of the late Maastrichtian age. This occurrence is not noted by Sullivan and Williamson in their 1999 review of the genus and has not been further elaborated upon elsewhere.

In 1921, Charles H. Sternberg recovered a partial skull (PMU.R1250) from what is now known as the slightly younger Kirtland Formation in San Juan County, New Mexico. This specimen was sent to Uppsala, where Carl Wiman described it as a second species, *P. tubicen*, in 1931. The specific epithet is derived from the Latin word *tǔbǐcěn*, meaning "trumpeter". A second, nearly complete *P. tubicen* skull (NMMNH P-25100) was found in New Mexico in 1995. Using computed tomography of this skull, Robert Sullivan and Thomas Williamson gave the genus a monographic treatment in 1999 that covered aspects of its anatomy and taxonomy, as well as the functions of its crest. Williamson later published an independent review of the remains that disagreed with the taxonomic conclusions.

John Ostrom described another good specimen (FMNH P27393) from New Mexico as *P. cyrtocristatus* in 1961. It includes a partial skull with a short, rounded crest and much of the postcranial skeleton except for the feet, neck, and parts of the tail. Its specific name is derived from the Latin words *curtus*, meaning "shortened" and *cristatus*, meaning "crested". The specimen was found in either the top of the Fruitland Formation or, more likely, the base of the overlying Kirtland Formation. The range of this species was described in 1979, when David B. Weishampel and James A. Jensen described a partial skull with a similar crest (BYU 2467) from the Campanian age Kaiparowits Formation of Garfield County, Utah. Since then, another skull has been found in Utah with the short, rounded *P. cyrtocristatus* crest morphology.

### Species[edit]

*Parasaurolophus* is known from three certain species: *P. walkeri*, *P. tubicen*, and *P. cyrtocristatus*. All of them can be clearly distinguished from each other and have many differences. The first named species, therefore the type, is *P. walkeri*. One certain specimen from the Dinosaur Park Formation is referred to it, but many more are almost certainly referable. Like stated above, it is different from the other two species, with it having a simpler internal structure than *P. tubicen*, along with a straighter crest and different internal structuring than *P. cyrtocristatus*.

The next named species is *P. tubicen*, which is the largest of the *Parasaurolophus* species. It lived in New Mexico, where three specimens are known, and can be differentiated from its other species. It possesses a long and straight crest, with a very complex interior compared to the other species. All known specimens of *P. tubicen* come from the De-Na-Zin Member of the Kirtland Formation.

In 1961, the third species, *P. cyrtocristatus* was named by John Ostrom. Its three known specimens have been found in the Fruitland and Kaiparowits formations of Utah and New Mexico. The second specimen, the first known from the Kaiparowits Formation, was originally unassigned to a specific taxon. Of the *Parasaurolophus* species, *P. cyrtocristatus* is the smallest and has the most curved crest. Because of its possession of the two above features, it has often been speculated that it was a female of *P. walkeri* or *P. tubicen*, which were all thought to be males, although *P. tubicen* lived approximately a million years later. As noted by Thomas Williamson, the type material of *P. cyrtocristatus* is about 72% the size of *P. tubicen*, close to the size at which other lambeosaurines are interpreted to begin showing definitive sexual dimorphism in their crests (~70% of adult size). Even though many scientists have supported the possible fact of *P. cyrtocristatus* being a female, many other studies have found that it is not because of the differences in age, distribution, and the large differences in the crest and its internal structure.

A study published in *PLoS ONE* in 2014 found that one more species could be referred to *Parasaurolophus*. This study, led by Xing, found *Charonosaurus jiayensis* was actually nested deeply inside *Parasaurolophus*, which created the new species *P. jiayensis*. If this species is indeed inside *Parasaurolophus*, then the genus therefore lasted until the K-Pg extinction and is known from two continents.

## Description[edit]

Like most dinosaurs, the skeleton of *Parasaurolophus* is incompletely known. The length of the type specimen of *P. walkeri* is estimated at 9.45 metres (31.0 ft), and allometry-based body mass estimates indicate that a 9 metres (30 ft) long individual would have weighed more than 5 metric tons (5.5 short tons). Gregory S. Paul estimated that an average adult individual of the type species would measure 7.5 metres (25 ft) long and weigh 2.6 metric tons (2.9 short tons). Its skull is about 1.6 m (5 ft 3 in) long, including the crest, whereas the type skull of *P. tubicen* is over 2 m (6 ft 7 in) long, indicating it was a larger animal. Its single known arm was relatively short for a hadrosaurid, with a short but wide shoulder blade. The thighbone measures 103 cm (41 in) long in *P. walkeri* and is robust for its length when compared to other hadrosaurids. The upper arm and pelvic bones were also heavily built.

Like other hadrosaurids, it was able to walk on either two legs or four. It probably preferred to forage for food on four legs, but ran on two. The neural spines of the vertebrae were tall, as was common in lambeosaurines. At their tallest over the hips, they increased the height of the back. Skin impressions are known for *P. walkeri*, showing uniform tubercle-like scales, but no larger structures.

### Skull[edit]

The most noticeable feature was the cranial crest that protruded from the rear of the head and was made up of the premaxilla and nasal bones. The crest was hollow, with distinct tubes leading from each nostril to the end of the crest before reversing direction and heading back down the crest and into the skull. The tubes were simplest in *P. walkeri*, and more complex in *P. tubicen*, where some tubes were blind and others met and separated. While *P. walkeri* and *P. tubicen* had long crests with slight curvature, *P. cyrtocristatus* had a short crest with a more circular profile.

### Diet and feeding[edit]

As a hadrosaurid, *Parasaurolophus* was a large bipedal and quadrupedal herbivore, eating plants with a sophisticated skull that permitted a grinding motion analogous to chewing. Its teeth were continually being replaced and were packed into dental batteries containing hundreds of teeth, but only a relative handful of which were in use at any time. It used its beak to crop plant material, which was held in the jaws by a cheek-like organ. Vegetation could have been taken from the ground up to a height of around 4 m (13 ft). As noted by Robert Bakker, lambeosaurines have narrower beaks than hadrosaurines, implying that *Parasaurolophus* and its relatives could feed more selectively than their broad-beaked, crestless counterparts. *Parasaurolophus* had a diet consisting of leaves, twigs, and pine needles which would imply that it was a browser.

### Growth[edit]

*Parasaurolophus* is known from many adult specimens, and a juvenile described in 2013, numbered RAM 140000 and nicknamed Joe, after a volunteer at the Raymond M. Alf Museum of Paleontology (RAM). The juvenile was discovered in the Kaiparowits Formation in 2009. Excavated by the joint expedition by museum and The Webb Schools, the juvenile has been identified as around only one year old when it died. Referred to *Parasaurolophus* sp., the juvenile is the most complete, as well as youngest *Parasaurolophus* ever found, and measures 2.5 m (8.2 ft). This individual fits neatly into the currently known *Parasaurolophus* growth stages, and lived approximately 75 million years ago. Even though no complete skull of the intermediate age between RAM 14000 and adult *Parasaurolophus* has been found yet, a partial braincase of about the right size is known. At 25% of the total adult size, the juvenile show that crest growth of *Parasaurolophus* began sooner than in related genera, such as *Corythosaurus*. It has been suggested that *Parasaurolophus* adults bore such large crests, especially when compared to the related *Corythosaurus*, because of this difference in age between when their crests started developing. Its age also means that *Parasaurolophus* had a very fast growth rate, which took place in about a year. The crest of the juvenile is not long and tubular like the adults, but low and hemispherical.

The skull of RAM 14000 is almost complete, with the left side only lacking a piece of the maxilla. However, the skull was split down the middle by erosion, possibly when it was resting on the bottom of a river bed. The two sides are displaced slightly, with some bones of the right being moved off the main block, also by erosion. After reconstruction, the skull viewed from the side resembles other juvenile lambeosaurines found, being roughly a trapezoid in shape.

A partial cranial endocast for RAM 14000 was reconstructed from CT scan data, the first ever for a *Parasaurolophus* of any ontogenetic stage. The endocast was reconstructed in two sections, one on the portion of the braincase articulated with the left half of the skull and the remainder on the disarticulated portion of the braincase. Their relative position was then approximated based on cranial landmarks and comparison with other hadrosaurids. Because of weathering, many of the smaller neural canals and foramina could not be identified for certain.

### Cranial crest[edit]

Many hypotheses have been advanced as to what functions the cranial crest of *Parasaurolophus* performed, but most have been discredited. It is now believed that it may have had several functions: visual display for identifying species and sex, sound amplification for communication, and thermoregulation. It is not clear which was most significant at what times in the evolution of the crest and its internal nasal passages.

#### Differences in crests[edit]

As for other lambeosaurines, it is believed that the cranial crest of *Parasaurolophus* changed with age and was a sexually dimorphic characteristic in adults. James Hopson, one of the first researchers to describe lambeosaurine crests in terms of such distinctions, suggested that *P. cyrtocristatus*, with its small crest, was the female form of *P. tubicen*. Thomas Williamson suggested it was the juvenile form. Neither hypothesis became widely accepted. As only six good skulls, one juvenile braincase, and one recently discovered juvenile skull are known, additional material will help clear up these potential relationships. Williamson noted that in any case, juvenile *Parasaurolophus* probably had small, rounded crests like *P. cyrtocristatus*, that probably grew faster as individuals approached sexual maturity. Recent restudy of a juvenile braincase previously assigned to *Lambeosaurus*, now assigned to *Parasaurolophus*, provides evidence that a small tubular crest was present in juveniles. This specimen preserves a small upward flaring of the frontal bones that was similar to but smaller than what is seen in adult specimens; in adults, the frontals formed a platform that supported the base of the crest. This specimen also indicates that the growth of the crest in *Parasaurolophus* and the facial profile of juvenile individuals differed from the *Corythosaurus*-*Hypacrosaurus*-*Lambeosaurus* model, in part because the crest of *Parasaurolophus* lacks the thin bony 'coxcomb' that makes up the upper portion of the crest of the other three lambeosaurines.

#### Rejected function hypotheses[edit]

Many early suggestions focused on adaptations for an aquatic lifestyle, following the hypothesis that hadrosaurids were amphibious, a common line of thought until the 1960s. Thus, Alfred Sherwood Romer proposed it served as a snorkel, Martin Wilfarth that it was an attachment for a mobile proboscis used as a breathing tube or for food gathering, Charles M. Sternberg that it served as an airtrap to keep water out of the lungs, and Ned Colbert that it served as an air reservoir for prolonged stays underwater.

Other proposals were more mechanical in nature. William Parks, in 1922, suggested that the crest was joined to the vertebrae above the shoulders by ligaments or muscles, and helped with moving and supporting the head. This is unlikely, because in all modern archosaurs, the nuchal ligament attaches to the neck or base of the skull. Othenio Abel proposed it was used as a weapon in combat among members of the same species, and Andrew Milner suggested that it could be used as a foliage deflector, like the helmet crest (called a 'casque') of the cassowary. Still, other proposals made housing specialized organs the major function. Halszka Osmólska suggested that it housed salt glands, and John Ostrom suggested that it housed expanded areas for olfactory tissue and much improved sense of smell of the lambeosaurines, which had no obvious defensive capabilities.

Most of these hypotheses have been discredited or rejected. For example, there is no hole at the end of the crest for a snorkeling function. There are no muscle scars for a proboscis and it is dubious that an animal with a beak would need one. As a proposed airlock, it would not have kept out water. The proposed air reservoir would have been insufficient for an animal the size of *Parasaurolophus*. Other hadrosaurids had large heads without needing large hollow crests to serve as attachment points for supporting ligaments. Also, none of the proposals explain why the crest has such a shape, why other lambeosaurines should have crests that look much different but perform a similar function, how crestless or solid-crested hadrosaurids got along without such capabilities, or why some hadrosaurids had solid crests. These considerations particularly impact hypotheses based on increasing the capabilities of systems already present in the animal, such as the salt gland and olfaction hypotheses, and indicate that these were not primary functions of the crest. Additionally, work on the nasal cavity of lambeosaurines shows that olfactory nerves and corresponding sensory tissue were largely outside the portion of the nasal passages in the crest, so the expansion of the crest had little to do with the sense of smell.

#### Temperature regulation hypothesis[edit]

The large surface area and vascularization of the crest also suggests a thermoregulatory function. The first to propose the cranial crests of lambeosaurines related to temperature regulation was Wheeler (1978). He proposed that there was a nerve connection between the crest and the brain, so that the latter could be cooled by the former. The next people to publish a related idea were Teresa Maryańska and Osmólska, who realized that like modern lizards, dinosaurs could have possessed salt glands, and cooled off by osmo-regulation. In 2006 Evans published an argument about the functions of lambeosaurine crests, and supported why this could be a causing factor for the evolution of the crest.

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