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Parasaurolophus

Parasaurolophus is a genus of large, herbivorous ornithopod dinosaur belonging to the family Hadrosauridae, known for its distinctive elongated, tubular cranial crest that extends backward over the skull.^[1] This Late Cretaceous hadrosaur, which lived approximately 76.5 to 73 million years ago in what is now western North America, measured up to 10 meters (33 feet) in length and weighed around 2.5 metric tons, featuring a robust build adapted for both bipedal and quadrupedal locomotion.^[2]^[3]^[4] Fossils of Parasaurolophus have been discovered primarily in formations such as the Dinosaur Park Formation in Alberta, Canada, and the Kirtland Formation in New Mexico, USA, with additional specimens from Utah's Kaiparowits Formation, indicating it inhabited coastal floodplains and river valleys.^[1]^[5] The genus includes three recognized species: P. walkeri, P. tubicen, and P. cyrtocristatus, distinguished largely by variations in crest morphology, with recent analyses refining their taxonomy based on cranial remains.^[1] As a duck-billed dinosaur, it possessed a complex dental battery with hundreds of teeth for grinding tough plant material, supporting its role as a primary consumer in its ecosystem.^[3] The iconic crest of Parasaurolophus, formed by the premaxilla, nasal bones, and possibly other elements, housed extensions of the nasal passages, leading to hypotheses about its functions in acoustic communication, visual display, or thermoregulation, though ongoing research, including CT scans of skulls, continues to explore these adaptations.^[1]^[2]^[6] Ontogenetic studies reveal that the crest grew dramatically during maturity, changing from a smaller, rounded structure in juveniles to the full backward-curving tube in adults, potentially aiding in species recognition or social behaviors within herds.^[7] Paleopathological evidence from specimens also shows instances of injuries and diseases, such as fractured ribs and infections, providing insights into the dinosaur's biology and lifestyle.^[8]

Discovery and species

History of discovery

The genus Parasaurolophus was established based on a nearly complete skull and partial skeleton discovered in 1920 within the Dinosaur Park Formation of what is now Dinosaur Provincial Park, Alberta, Canada. This holotype specimen (ROM 768), collected by Levi Sternberg as part of a Royal Ontario Museum expedition, was formally described and named Parasaurolophus walkeri by William A. Parks in 1922, highlighting its resemblance to the related hadrosaur Saurolophus.^[9]^[10] In 1923, Levi Sternberg collected a partial skull from the Kirtland Formation in San Juan County, New Mexico, which became the holotype (PMU.R.1250) of Parasaurolophus tubicen. This specimen, shipped to the Paleontological Museum in Uppsala, Sweden, was named and described by Carl Wiman in 1931 based on its distinctive tubular crest extension.^[9] That same year, Charles H. Sternberg discovered another partial skull and skeleton in the Fruitland Formation near Fruitland, New Mexico, designated as the holotype (AMNH 5339) of Parasaurolophus cyrtocristatus and described by John H. Ostrom in 1961. Specimens of Parasaurolophus remained scarce for much of the 20th century, with additional fragmentary remains reported from formations in Alberta, Utah, and New Mexico, often housed at institutions such as the Royal Ontario Museum (holotype of P. walkeri), the American Museum of Natural History, and the Royal Tyrrell Museum of Palaeontology, which holds multiple associated skeletons from the Dinosaur Park Formation.^[11]^[10] A significant advance came in 2009 when high school student Kevin Marynowski discovered a nearly complete juvenile skeleton, including a well-preserved skull, in the Kaiparowits Formation of Grand Staircase–Escalante National Monument, Utah; announced publicly in 2013, this specimen (UMNH VP 16784, nicknamed "Joe") represents the most complete juvenile Parasaurolophus known and is housed at the Natural History Museum of Utah.^[12] In 2021, researchers described a new, nearly complete adult skull of P. cyrtocristatus (UMNH VP 21625) from the same region, the first such skull in nearly a century, providing key details on crest variation and housed at the Natural History Museum of Utah.^[13] In 2020, detailed analysis of the P. walkeri holotype revealed paleopathological lesions, including a dental abscess in the maxilla, fractured ribs, and ossified muscle trauma near the crest base, indicating this individual endured significant injury and infection during its life.^[14]

Valid species and synonyms

The genus Parasaurolophus is currently recognized as comprising three valid species, each distinguished by variations in cranial crest morphology and overall skull proportions. The type species, P. walkeri, is known from multiple specimens in the Dinosaur Park Formation of Alberta, Canada, and is characterized by a straight, backward-projecting crest formed by the premaxillae and nasals, with an estimated body length of about 9.5 meters. P. tubicen, described from the Kirtland Formation in New Mexico, features a longer, more curved crest that can reach up to 1.8 meters in length, accompanied by a more robust skull with expanded nasal passages. P. cyrtocristatus, from the Fruitland Formation in New Mexico and the Kaiparowits Formation in Utah, has a shorter, more curved crest and narrower skull proportions, though its distinction from other species is supported by consistent morphological differences in crest shape and size.^[1]^[15] A fourth species, P. jiayensis, was proposed in 2014 through the reclassification of Charonosaurus jiayensis from the Yuliangze Formation in northeastern China, following phylogenetic analyses that placed the Chinese specimens within the Parasaurolophus clade due to shared crest structure and dental traits; however, this assignment remains debated and is not universally accepted.^[16] This proposal would extend the geographic range of the genus to Asia and suggest a longer temporal span into the Maastrichtian stage. These species differ diagnostically in crest length and curvature—straight and moderate in P. walkeri, long and curved in P. tubicen, and short and curved in P. cyrtocristatus—along with subtle variations in skull proportions, such as the angle of the nasal-premaxillary suture and the size of the maxillary fenestra. If accepted, P. jiayensis shares the curved crest profile but exhibits proportionally longer nasals adapted to its Maastrichtian environment.^[1] Estimated distributions indicate that P. walkeri occupied northern Laramidia during the Campanian stage, while P. tubicen and P. cyrtocristatus are restricted to southern Laramidia, reflecting latitudinal provinciality in hadrosaurid evolution. The proposed P. jiayensis would represent an Asian offshoot, potentially indicating dispersal across Beringia.^[17]

Description

Size and overall morphology

Parasaurolophus was a large ornithischian dinosaur, with adults typically measuring 9 to 10 meters in total length and reaching a height of 4 to 5 meters at the hips when standing bipedally.^[18] Body mass estimates, derived from volumetric models of skeletal reconstructions, range from 2.5 to 3 tonnes, reflecting its robust build adapted to terrestrial herbivory.^[19] These dimensions position Parasaurolophus among the larger members of the Hadrosauridae family, with proportions emphasizing a long tail comprising about half the body length and a relatively deep torso for efficient weight support. The dinosaur exhibited facultative locomotion, capable of both bipedal and quadrupedal gaits, as evidenced by its robust fore- and hindlimbs and broad pelvis that distributed body weight effectively during quadrupedal movement.^[20] Shared hadrosaurid traits included a flattened, duck-like bill for cropping low vegetation and a complex dental battery housing approximately 1,000 teeth arranged in functional rows for grinding tough plant matter.^[21] Distinctive to Parasaurolophus were elongated neural spines on the dorsal vertebrae, particularly over the hips, which elevated the back and potentially formed a low dorsal hump for muscle attachment or display.^[22] Sexual dimorphism in Parasaurolophus remains inconclusive, with limited fossil evidence suggesting possible subtle size variations between sexes but lacking robust statistical support to confirm such differences.^[23] Juveniles, including hatchlings estimated at around 1 meter in length based on limb bone proportions, underwent rapid early growth, reaching subadult sizes of over 2 meters within the first year.^[24] This accelerated ontogeny is inferred from histological analysis of growth rings in comparable hadrosaurid bones, indicating high metabolic rates during early life stages.^[18]

Skull and cranial crest

The skull of Parasaurolophus measured 1.1 to 1.3 meters in basicranial length, characterized by an expanded premaxilla that formed a broad, beak-like structure adapted for cropping vegetation, alongside complex nasal passages that extended into the distinctive cranial crest. The overall skull, including the crest, reached up to 1.6 meters in P. walkeri and over 2 meters in P. tubicen.^[7] The cranial crest was a hollow, tubular structure primarily composed of the fused premaxillae, nasals, and prefrontals, with the prefrontals contributing to the rear base. Internally, it featured a network of interconnected tubes—typically three pairs (median, lateral, and dorsal)—that originated from the external nares and extended to the crest's tip, forming resonant chambers linked to the nasal cavity.^[15] Bone surface texture indicates the crest's bony core was likely enveloped in a keratinous sheath, providing additional length and structural support.^[8] Crest morphology varied among species, reflecting differences in elongation and curvature. In P. walkeri, the crest curved backward and attained a height of approximately 1 meter. P. tubicen exhibited a more pronounced backward-curving crest reaching up to 1.8 meters in length. P. cyrtocristatus had a shorter, more curved crest. A 2024 physical modeling study, utilizing 3D-printed replicas at 1:3 scale derived from CT scans of fossils, confirmed the intricate tubular internal architecture of the crest across specimens.^[25]

Postcranial skeleton

The axial skeleton of Parasaurolophus is characterized by robust cervical vertebrae with low neural spines in the anterior region that become taller posteriorly, supporting the long neck typical of hadrosaurids.^[8] The dorsal vertebrae feature tall neural spines that contribute to the high back profile, while the sacral vertebrae are co-ossified to the ilia, forming a stable pelvic support; the caudal series is elongated and tapering, with chevron bones providing reinforcement for balance during locomotion, with only the first few caudals preserved in the type specimen of P. walkeri.^[8] The pectoral girdle includes a large, robust scapula measuring approximately 1 m in length, with a broad blade and acromion process adapted for weight-bearing in quadrupedal stance, and a coracoid that articulates closely with the scapula, though not fully fused as in some derived ornithischians. The forelimbs are shorter than the hindlimbs, comprising a stout humerus, radius, and ulna, with the manus featuring four digits where the central three bear hoof-like phalanges suited for quadrupedal support and the pollex reduced to a small splint-like element.^[8] The hindlimbs are more robust, with a femur reaching up to 1.2 m in length in large individuals, a reduced fibula that splints against the tibia, and a pes with three main weight-bearing digits (II–IV) ending in hoof-like unguals, enabling efficient bipedal progression. The pelvic girdle features a broad ilium with a pronounced preacetabular process and ischia that are straight and rod-like.^[8]

Classification

Phylogenetic position

Parasaurolophus belongs to the family Hadrosauridae, within the subfamily Lambeosaurinae, a group of ornithopod dinosaurs characterized by their hollow cranial crests derived from expanded nasal and premaxillary bones.^[26] This placement is supported by cladistic analyses that recover Lambeosaurinae as one of two major subclades of Hadrosauridae, alongside Saurolophinae, based on shared features such as thecausal neural arch morphology and specific dental battery structures.^[26] Within Lambeosaurinae, Parasaurolophus forms part of the tribe Parasaurolophini, a monophyletic group that includes close relatives such as Charonosaurus, with some recent studies nesting Charonosaurus jiayinensis deeply within Parasaurolophus and reassigning it as P. jiayensis, although this reassignment remains debated and is not universally accepted.^[16] This clade is positioned basal to more derived lambeosaurines like Corythosaurus and Hypacrosaurus, which share a common ancestor but differ in crest morphology and postcranial proportions.^[26] Key synapomorphies uniting Parasaurolophini include an elongated, tubular cranial crest formed by the fusion and extension of the premaxillae, nasals, and prefrontals, along with a unique configuration of the nasal tubes that extend posteriorly into the crest cavity.^[16] The premaxilla contacts the nasal solely along the nasal process, and the jugal contributes to wider orbital margins relative to the infratemporal fenestra.^[16] Phylogenetic trees derived from parsimony and Bayesian analyses, including comprehensive matrices from recent studies such as Gates et al. (2021), consistently recover a Parasaurolophus clade comprising P. walkeri, P. tubicen, P. cyrtocristatus, and P. jiayensis, with moderate to strong nodal support indicated by bootstrap values exceeding 70%.^[1] These analyses incorporate over 200 cranial and postcranial characters, emphasizing crest elongation and nasal passage complexity as diagnostic traits. Time-calibrated phylogenies, incorporating stratigraphic data from Campanian-Maastrichtian formations, suggest that the Parasaurolophus lineage originated approximately 80 million years ago during the early Campanian and underwent diversification throughout the stage, coinciding with environmental shifts in western North America and Asia.^[27]

Evolutionary relationships

Parasaurolophus originated as part of the lambeosaurine radiation within Hadrosauridae during the mid-Campanian stage of the Late Cretaceous, approximately 80 million years ago, evolving from earlier lambeosaurine ancestors on the continent of Laramidia in western North America.^[28] This emergence coincided with increasing provinciality among hadrosaurids, as the persistent Western Interior Seaway fragmented Laramidia into northern and southern regions, fostering isolated populations.^[27] The genus's initial diversification is marked by the appearance of distinct species across these regions, with fossil evidence from formations such as the Oldman and Dinosaur Park in the north and the Fruitland and Kirtland in the south, reflecting adaptive responses to varying coastal plain environments.^[15] A notable aspect of Parasaurolophus evolution is the observed north-south cline in cranial crest morphology, where northern forms like P. walkeri exhibit elongated, backward-curving crests, while southern species such as P. tubicen and P. cyrtocristatus display more robust, laterally curved structures.^[15] This variation likely arose from geographic isolation imposed by the narrowing Western Interior Seaway and the onset of Laramide orogeny, which created barriers to gene flow and promoted regional adaptations in display structures potentially used for acoustic or visual signaling.^[27] Related genera, such as the southern Laramidian Magnapaulia laticaudus from the El Gallo Formation of Baja California, represent transitional forms bridging Parasaurolophus-like tubular crests with broader lambeosaurine diversity, forming a monophyletic southern clade that highlights latitudinal endemism.^[29] The evolutionary history of Parasaurolophus concluded by the late Campanian, around 73 million years ago, as lambeosaurines declined across Laramidia and were progressively replaced by more generalized saurolophine hadrosaurids in the Maastrichtian stage. This turnover may reflect ecological shifts, including changing floral resources and competitive pressures from expanding saurolophine lineages better suited to inland habitats.^[30] The fossil record reveals significant gaps, particularly in Asia, where only the late Campanian to Maastrichtian P. jiayensis (formerly Charonosaurus jiayinensis) from the Yuliangze Formation of northeastern China provides evidence of the genus's presence beyond Laramidia, suggesting potential undiscovered species that could illuminate intercontinental dispersal patterns.^[31]

Paleobiology

Growth and ontogeny

Parasaurolophus exhibited rapid growth typical of hadrosaurid dinosaurs, with bone histology indicating high initial growth rates that slowed in later ontogeny. Analysis of long bones and ribs from related hadrosaurids, such as Hypacrosaurus and Maiasaura, reveals fibrolamellar bone tissue with vascular canals oriented parallel to the bone surface in juveniles, transitioning to more lamellar-zonal tissue in adults marked by lines of arrested growth (LAGs).^[7]^[32] These LAGs, representing annual pauses in growth, suggest that individuals reached subadult sizes of approximately 5 meters in length within 3–5 years, with full skeletal maturity attained by 10–15 years, and potential lifespans exceeding 20 years based on up to 20 or more LAGs in mature specimens.^[33] Ontogenetic changes in Parasaurolophus are well-documented through a juvenile specimen (RAM 14000) from the Kaiparowits Formation, estimated at less than 1 year old and measuring about 2 meters in length, or roughly 25% of adult body size. Histological examination of its tibia shows densely vascularized woven bone without LAGs or annuli, confirming its young age and rapid early growth phase comparable to modern birds. The skull underwent significant elongation with age, and the cranial crest, which was small but present in this hatchling, expanded dramatically in subadults to form the characteristic tube-like structure, indicating peramorphic development relative to other hadrosaurids where crest initiation occurs later.^[7] Evidence for sexual maturity in Parasaurolophus is indirect, as medullary bone—a calcium reservoir tissue diagnostic of gravid females in birds and some dinosaurs—has not been identified in known specimens.^[34] In related hadrosaurids, sexual maturity likely occurred at 60–70% of adult body size, around 2–3 years of age, based on the onset of reproductive traits and growth curve inflections before full somatic maturity.^[34] Compared to contemporaneous ceratopsians, Parasaurolophus displayed faster overall growth rates, achieving larger body sizes more quickly due to sustained high metabolic rates evidenced by denser vascularization in hadrosaurid bone tissue, whereas ceratopsians exhibited more moderate rates with earlier onset of remodeling.^[35]^[36] This pattern aligns with other hadrosaurids, supporting a shared life history strategy of rapid juvenile growth to evade predation.^[32]

Diet and feeding

Parasaurolophus was a herbivorous dinosaur whose diet consisted primarily of low-lying vegetation, including ferns, horsetails, and cycads, as inferred from the dominant plant fossils in its Late Cretaceous habitats and dental microwear patterns indicating consumption of tough, fibrous materials.^[37]^[38] Jaw mechanics further support adaptation to grinding such abrasive plants, with no direct evidence of gastroliths in Parasaurolophus but possible reliance on oral processing for initial breakdown.^[39] The feeding mechanism involved a complex dental battery comprising approximately 300 teeth per jaw side, arranged in tightly interlocked rows to form a dynamic grinding surface capable of transverse jaw motion guided by palatal flanges on the upper jaw.^[39] These teeth, featuring asymmetrical enamel for efficient wear, were replaced continuously at a rate of less than two months per tooth due to rapid eruption and heavy abrasion from processing fibrous vegetation.^[40] This conveyor-belt-like replacement ensured a perpetually functional occlusal surface for pulverizing plant matter. Parasaurolophus exhibited a bite force sufficient for shearing and crushing tough, low-fiber plants but inadequate for high browsing on woody material.^[41] As a facultative quadruped, it could adopt a four-legged stance to access vegetation up to 2 meters high while primarily browsing on all fours at ground level, occupying a niche distinct from higher-reaching herbivores like ceratopsians.^[42]

Cranial crest structure and functions

The cranial crest of Parasaurolophus features a complex internal structure characterized by highly branched nasal passages that extend through the hollow bony tube, forming multiple resonant chambers capable of modifying airflow and sound production.^[1] These passages originate from the external nares at the front of the skull, loop posteriorly and dorsally within the crest, and connect to the trachea via an S-shaped pathway, allowing for intricate acoustic tuning without compromising respiratory function.^[43] Recent 3D modeling based on CT scans of well-preserved specimens confirms this configuration, with the branched tubes creating multiply resonant spaces that could amplify specific sound frequencies.^[44] In November 2024, researchers presented findings from a 3D-printed physical model of the crest at a 1:3 scale, demonstrating its ability to produce low-frequency sounds, further supporting acoustic functions.^[25] Acoustic studies have tested the crest's potential as a vocal resonator, with physical and digital models indicating it produced low-frequency calls suitable for long-distance communication. A 2016 digital model of P. tubicen predicted fundamental resonant frequencies around 30 Hz, extending into a range of 30–300 Hz for modulated low calls, consistent with infrasonic or deep rumbling tones that could carry over kilometers in forested environments.^[45] These findings support behavioral functions, including species recognition and display calls during mating or social interactions, as the unique tube length and branching in Parasaurolophus crests differ from those in related lambeosaurines like Corythosaurus, producing distinct resonant profiles.^[46] For instance, P. tubicen specimens with longer crests generated deeper tones compared to the shorter-crested P. walkeri, enabling auditory differentiation among species.^[7] Ontogenetic changes further influenced crest resonance, as juveniles exhibited shorter, more rounded crests with higher-pitched potential outputs that lowered as the structure elongated during growth, aligning with maturation of social signaling needs.^[7] Evidence from vascular traces on fossil crests, including numerous foramina indicating dense blood vessel networks, has led to hypotheses of thermoregulation, where the large surface area facilitated heat exchange to cool the brain via a possible neural connection.^[10] Models integrating these vascular patterns suggest the crest acted as a heat sink, absorbing warmth by day and dissipating it at night, a function observed in comparative studies of other hollow-crested lambeosaurines.^[47] Alternative functions, such as aiding respiration or serving as a snorkel for aquatic feeding, have been rejected based on anatomical evidence; the nasal passages terminate internally near the throat, not at the crest tip, precluding external air access while submerged.^[1] Soft tissue reconstructions propose a keratinous sheath or frill covering the crest, potentially enhancing sound projection by directing acoustics, though direct fossil evidence remains limited.^[8] Pathological specimens, including those with healed fractures and infections in the crest, show no significant disruption to nasal passage integrity, indicating robust functional redundancy even under injury.^[48] Overall, integrative evidence from acoustic simulations, histological analysis of vascularization, and comparisons with lambeosaurine relatives underscores the crest's primary role in multimodal signaling, blending auditory and thermal elements for survival in Late Cretaceous ecosystems.^[49]

Sensory and behavioral adaptations

Parasaurolophus, like other lambeosaurine hadrosaurs, exhibited adaptations for enhanced visual acuity, with large orbits and expansive sclerotic rings indicating sizable eyes capable of detecting predators at a distance.^[49] The forward-facing orientation of the eyes provided a degree of binocular overlap, facilitating stereoscopic vision for improved depth perception during foraging or evasion maneuvers.^[50] Color vision was likely tetrachromatic, similar to that of modern birds, allowing differentiation of foliage and environmental cues in its coastal plain habitat.^[51]^[50] Auditory capabilities were tuned to low-frequency sounds, as evidenced by the elongate cochlea in the inner ear, which complemented potential resonant calls produced via the cranial crest for intraspecific communication over distances.^[52] This adaptation suggests sensitivity to infrasonic or deep rumbles, useful for herd coordination or predator alerts in vegetated environments. Olfaction played a secondary role, with reduced olfactory bulbs relative to cerebral hemispheres indicating limited reliance on smell compared to vision and hearing.^[52] Endocranial reconstructions of Parasaurolophus specimens confirm these small bulbs, measuring approximately 14 mm in width and comprising less than half the cerebrum's thickness.^[7] Behavioral inferences from hadrosaur bonebeds, including those of related lambeosaurines, support gregarious herding, where individuals likely traveled and foraged in groups to enhance vigilance against predators like tyrannosaurids. Parental care is suggested by nesting colonies in sympatric hadrosaurs such as Maiasaura, with juveniles remaining dependent in structured sites, implying similar protective behaviors for Parasaurolophus young near coastal nesting grounds.^[53] Limited seasonal migration along Late Cretaceous coastal plains is indicated by strontium isotope data from hadrosaur tooth enamel, revealing home ranges of about 80 km rather than extensive continental treks.^[54] Locomotor adaptations enabled both bipedal and quadrupedal gaits, with a stable quadrupedal stance for efficient travel and foraging, transitioning to bipedalism for bursts of speed estimated at 20-25 km/h based on limb proportions and trackway analogies.^[55] These capabilities supported escape strategies from ambush predators, leveraging herd dynamics for collective defense.^[56]

Paleopathology

Paleopathological evidence in Parasaurolophus fossils is limited due to the relative scarcity of well-preserved specimens, but documented cases reveal insights into injuries and diseases affecting these hadrosaurids. The holotype of P. walkeri (ROM 768), a nearly complete skeleton from the Dinosaur Park Formation in Alberta, Canada, exhibits multiple lesions indicative of trauma and infection. These include healed fractures on the fourth, fifth, and sixth left dorsal ribs, characterized by callus formation and remodeling, suggesting the individual survived the injury for months or years. Additionally, the specimen shows signs of periodontal disease in the left maxilla, with swollen bone and dental lesions likely resulting from bacterial infection in the gums, as well as myositis ossificans traumatica—a heterotopic ossification—on the left ilium and adjacent vertebrae, where abnormal bone growth formed in response to soft tissue trauma.^[14]^[8] Other Parasaurolophus specimens provide further examples of skeletal trauma. In ROM 768, a discoidal bony overgrowth above the neural spines of the third and fourth dorsal vertebrae is interpreted as a secondary response to the rib injuries, possibly involving ligament damage. A notch in the neural spines near the base of the cranial crest in the same specimen may represent a pathological deformation, potentially from repeated contact or impact, though this could be unique to the individual. Dental wear patterns across hadrosaurid fossils, including Parasaurolophus, often show heavy abrasion consistent with processing tough, fibrous vegetation, but excessive wear linked to pathology is noted in the type's periodontal case, where infection exacerbated tooth battery degradation.^[14]^[8]^[57] Pathologies in the cranial crest are rare and not well-documented beyond potential impact-related features in P. walkeri. No confirmed non-fatal deformations of the nasal tube have been reported in P. tubicen or other species. Overall, paleopathological prevalence in Parasaurolophus appears low compared to other hadrosaurids like Edmontosaurus or Corythosaurus, which show higher incidences of tail injuries and infections; this may reflect fewer preserved individuals rather than inherently robust health, as large-bodied ornithopods generally exhibit elevated trauma rates.^[58]^[57]^[8] These injuries imply that Parasaurolophus individuals endured significant physical stress, with rib fractures and soft tissue damage likely stemming from intraspecific combat—such as head-butting or flank-raking—or predator attacks by theropods like Gorgosaurus. The presence of healing in most cases indicates resilience, allowing survival post-trauma in a Late Cretaceous environment fraught with risks.^[14]^[8]^[59]

Paleoecology

Formation and environments

Parasaurolophus fossils are known primarily from three Campanian-age (approximately 76–73 million years ago) geological formations in western North America, reflecting a broad distribution across the landmass of Laramidia.^[7] The Dinosaur Park Formation of Alberta, Canada, consists of fluvial channel-belt, floodplain, and coal deposits that record sedimentation on an alluvial plain near a coastal setting, with meandering rivers, levees, and forested areas supporting diverse vegetation.^[60] Sediments include mudstones, sandstones, and carbonaceous shales indicative of periodic flooding and well-drained landscapes.^[61] In the southern United States, the Kirtland Formation of New Mexico represents alluvial and fluvial environments on coastal plains, characterized by seasonal rivers, overbank deposits, and swampy lowlands, as evidenced by interbedded sandstones, mudstones, and coal seams from the underlying Fruitland Formation transition.^[62] The Kaiparowits Formation of Utah, meanwhile, comprises a thick sequence of fluvial, crevasse splay, lacustrine, and overbank deposits in a deltaic system, with extensive swamps and channels fostering lush, fern- and conifer-dominated vegetation.^[63] These formations developed under a warm, humid subtropical climate across Laramidia, marked by wet-dry seasonal cycles and high precipitation that supported dense forests and wetlands, as inferred from abundant coal, mudstones, and paleosol evidence of subhumid to humid conditions.^[64] Taphonomic patterns in Parasaurolophus remains typically involve burial in floodplain settings, where rapid overbank sedimentation during floods preserved articulated skeletons with minimal disarticulation or weathering.^[7] The genus's distribution was confined to western North America.^[1]

Contemporaneous biota

Parasaurolophus shared its Late Campanian habitats in western North America with a diverse array of vertebrates and plants, primarily documented from the Oldman and Dinosaur Park formations of Alberta, Canada. Among herbivores, other hadrosaurids such as Gryposaurus notabilis and Prosaurolophus maximus were common, occupying similar ecological niches as mid-sized browsers in floodplain environments. Ceratopsians, including Chasmosaurus russelli and Centrosaurus apertus, formed large social groups and competed for mid-level vegetation, while armored ankylosaurids like Euoplocephalus tutus foraged on low-lying plants and defended against threats with their bony armor.^[65] Carnivorous dinosaurs posed significant predation pressure on Parasaurolophus and its contemporaries. In northern assemblages, such as the Dinosaur Park Formation, the tyrannosaurid Gorgosaurus libratus was the dominant large predator, preying on hadrosaur herds and ceratopsians. Further south, in formations like the Oldman, Daspletosaurus torosus filled a similar apex role, with evidence of bite marks on hadrosaur bones indicating active hunting. Smaller theropods, including troodontids like Troodon formosus, likely targeted juveniles or scavenged remains, contributing to a complex food web.^[66] The broader fauna included aquatic and semi-aquatic reptiles adapted to riverine settings, such as turtles (e.g., Adocus) and crocodilians (e.g., Leidyosuchus canadensis), which inhabited channels and wetlands alongside fish like gars and bowfins. Small mammals, particularly multituberculates such as Paracimexomys, represented the diminutive mammalian component, possibly nesting in burrows or feeding on insects and seeds.^[67]^[68] The vegetation supporting this ecosystem comprised a mix of gymnosperms and early angiosperms, with conifers (e.g., Libocedrus) dominating the canopy and ferns forming a dense understory, as revealed by pollen and macrofossil records. Angiosperm pollen indicates the presence of diverse flowering plants, providing nutritional variety for herbivores like Parasaurolophus.^[69]^[70] Ecological interactions among these taxa were shaped by resource competition and predation dynamics; for instance, overlapping diets among hadrosaurids and ceratopsians likely drove niche partitioning in browsing heights, while tyrannosaurid attacks may have favored herd formation in Parasaurolophus for collective defense.^[65]

Distribution and taphonomy

Fossils of Parasaurolophus are known primarily from Late Cretaceous deposits spanning a north-south gradient of approximately 1,500 km across western North America, from southern Alberta in Canada to northern New Mexico in the United States, with additional occurrences in Utah.^[10]^[7] This distribution is confined to the western interior, with no known remains from the eastern Appalachian region, reflecting the dinosaur's restriction to coastal plain environments along the Western Interior Seaway.^[10] Taphonomic patterns for Parasaurolophus indicate predominantly isolated or partially articulated skeletons preserved in fluvial channel and overbank deposits, rather than large monotypic bone beds, which are rare compared to those of sympatric hadrosaurs like Edmontosaurus.^[71]^[1] Disarticulation is common, often attributed to post-mortem scavenging and transport in river systems, with elements showing abrasion and weathering consistent with exposure on floodplains before burial.^[71] Southern sites, such as those in New Mexico, exhibit higher rates of erosion and fragmentation due to arid post-burial conditions, leading to poorer preservation compared to northern locales in Alberta.^[1] The fossil record of Parasaurolophus shows a strong bias toward adult individuals, with juveniles historically under-sampled until the discovery of a nearly complete juvenile skeleton (nicknamed "Joe") from the Kaiparowits Formation in 2009, published in 2013, which provided the first detailed ontogenetic data.^[7] This underrepresentation likely stems from taphonomic size bias, where smaller juvenile bones are more susceptible to destruction by weathering, predation, or fluvial transport, resulting in fewer preservable remains.^[71] No significant new juvenile finds have altered this pattern as of 2025.^[72] Paleo-distribution models suggest Parasaurolophus exhibited migratory behavior along the margins of the Western Interior Seaway, with latitudinal movements inferred from intra-tooth variations in oxygen isotopes (δ¹⁸O) in hadrosaur enamel, including lambeosaurines closely related to Parasaurolophus.^[73] These δ¹⁸O fluctuations indicate seasonal shifts between cooler northern coastal areas and warmer southern floodplains, supporting a pattern of long-distance travel to exploit varying vegetation and avoid seasonal stressors.^[73]^[74]

References

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19.8A). Parasaurolophus was the first dinosaur to be identified from the Kaiparowits Formation, based upon a highly eroded, partial skull (BYU 2467; Weishampel ...<|control11|><|separator|>
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Parasaurolophus, one of the dinosaurs that appeared in the films Jurassic Park and The Lost World, lived during the Late Cretaceous Period, about 75 million ...
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The rare lambeosaurine Parasaurolophus is described for the first time from the upper Maestrichtian Kaiparowits Formation of southern Utah.
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Digital paleontology: Producing the sound of the Parasaurolophus ...
Dec 19, 1997 · The dinosaur had a bony tubular crest that extended back from the top of its head. Many scientists have believed the crest, containing a ...
[7]
Ontogeny in the tube-crested dinosaur Parasaurolophus ...
The tube-crested hadrosaurid dinosaur Parasaurolophus is remarkable for its unusual cranial ornamentation, but little is known about its growth and development.
[8]
Description and etiology of paleopathological lesions in the type ...
Dec 1, 2020 · The fossilized lesions in Parasaurolophus walkeri comprise periodontal disease, fractured ribs, and myositis ossificans traumatica in a number ...
[9]
[PDF] New Mexico Museum of Natural History and Science - ResearchGate
The first specimen of Parasaurolophus was discovered by L. W.. Dippell, and collected by Levi Sternberg, in 1920 in the Dinosaur Park. Formation (formerly ...
[10]
The Real Parasaurolophus - Philip J. Currie Dinosaur Museum
The holotype specimen of this dinosaur was found in Dinosaur Provincial Park in 1920 by a team from the Royal Ontario Museum. ... Sternberg, Charles M. (1935). “ ...Missing: 1923 | Show results with:1923
[11]
Collections | Royal Tyrrell Museum
About 3000 specimens are added to our collection each year. The online collections database can be viewed through our eMuseum site. Researchers interested in ...
[12]
High school student discovers skeleton of baby dinosaur
Detailed study of the skeleton of "Joe" identified it as the most complete specimen yet known for Parasaurolophus (pronounced PAIR-uh-SORE-AH- ...
[13]
Description and rediagnosis of the crested hadrosaurid ... - PeerJ
Jan 25, 2021 · Parasaurolophus walkeri (Parks, 1922) is known from a single complete skull and almost complete skeleton from the Dinosaur Park Formation ...
[14]
Description and etiology of paleopathological lesions in the type ...
Dec 1, 2020 · The fossilized lesions in Parasaurolophus walkeri comprise periodontal disease, fractured ribs, and myositis ossificans traumatica in a ...
[15]
(PDF) A new skull of Parasaurolophus (Dinosauria - ResearchGate
Dec 4, 2015 · A new skull of Parasaurolophus (Dinosauria: Hadrosauridae) from the Kirtland Formation of New Mexico and a revision of the genus. January 1999.
[16]
A New Basal Hadrosauroid Dinosaur (Dinosauria - Research journals
Jun 5, 2014 · Hadrosauridae is the monophyletic group consisting of Saurolophus osborni, Parasaurolophus walkeri, their most recent common ancestor, and all ...
[17]
Phylogenetic and biogeography analysis of Mexican hadrosauroids
This work provides a review of the taxonomic diversity, phylogenetic relationships, and historical biogeography of the seven described hadrosauroids from ...
[18]
Ontogeny in the tube-crested dinosaur Parasaurolophus ... - PeerJ
Oct 22, 2013 · The tube-crested hadrosaurid dinosaur Parasaurolophus is remarkable for its unusual cranial ornamentation, but little is known about its ...Missing: Xing | Show results with:Xing
[19]
New perspectives on body size and shape evolution in dinosaurs
May 8, 2025 · Depending on the size and shape of the soft tissue envelope estimated by different researchers, body mass estimates based on volumetric models ...
[20]
(PDF) Limb-Bone Scaling Indicates Diverse Stance and Gait in ...
PDF | Background: The most primitive ornithischian dinosaurs were small bipeds, but quadrupedality evolved three times independently in the clade. The.
[21]
How duck-billed dinosaurs evolved to have more than - Earth Archives
Besides having toothless duck-like bills, hadrosaurs had large heads with hundreds of teeth packed into what's called a dental battery, large bodies, and the ...Missing: traits | Show results with:traits
[22]
The origins of neural spine elongation in iguanodontian dinosaurs ...
Aug 21, 2025 · Possible explanations for neural spine elongation in Ankylopollexia include biomechanical advantage, perhaps related to greater mass and a ...
[23]
The evolution of 'bizarre structures' in dinosaurs: biomechanics ...
Dec 22, 2010 · Unfortunately the statistical evidence that supports sexual dimorphism as an explanation for these differences is problematic. For example ...
[24]
(PDF) The humerus of a hatchling lambeosaurine (Dinosauria
Oct 21, 2015 · A small left humerus of a lambeosaurine (Hadrosauridae), measuring 41 mm in length, is identified as a hatchling individual that probably ...
[25]
Parasaurolophus pipes: Modeling the dinosaur's crest to study its ...
Nov 22, 2024 · Lin created a physical setup made of tubes to represent a mathematical model that will allow researchers to discover what was happening ...
[26]
https://academic.oup.com/zoolinnean/article/159/2/435/2622978
[27]
Tlatolophus galorum, gen. et sp. nov., a parasaurolophini dinosaur ...
= 0.720. Our phylogenetic results reveal that Parasaurolophini is a monophyletic group of the family Hadrosauridae, the group Saurolophidae, and the ...
[28]
Mountain Building Triggered Late Cretaceous North American ...
The major speciation events of North American taxa within both the Prosaurolophus and Gryposaurus subclades are unambiguously inferred to have been the result ...<|control11|><|separator|>
[29]
Diversity, Relationships, and Biogeography of the Lambeosaurine ...
Jul 26, 2013 · We provide a thorough re-evaluation of the taxonomic diversity, phylogenetic relationships, and historical biogeography of the lambeosaurine ...
[30]
The Lambeosaurine Dinosaur Magnapaulia laticaudus from the Late ...
Jun 12, 2012 · The lambeosaurine fossil record is widespread in Europe, Asia, and the Americas, spanning the Santonian through the late Maastrichtian ...<|separator|>
[31]
Deep-time biodiversity patterns and the dinosaurian fossil record of ...
Jun 23, 2021 · We quantitatively investigated faunal provinciality in ceratopsid and hadrosaurid dinosaurs using a biogeographic network approach and investigated sampling ...
[32]
Charonosaurus jiayinensis ng, n.sp.,a lambeosaurine dinosaur from ...
Large bonebeds have been excavated in the Late Maastrichian Yuliangze Formation near Jiayin (Heilongjang Province, northeastern China).Missing: origins | Show results with:origins
[33]
(PDF) The bone histology of the hadrosaurid dinosaur Maiasaura ...
Aug 10, 2025 · By the sub-adult stage, lines of arrested growth (LAGs) begin to appear regularly. Resorption lines and substantial Haversian substitution in ...
[34]
Testing size–frequency distributions as a method of ontogenetic ...
Aug 1, 2020 · Using these data, Brinkman (2014) concluded that hadrosaurids from the DPF had a rapid growth rate, attaining adult size within 3 years of age.<|control11|><|separator|>
[35]
Sexual maturity in growing dinosaurs does not fit reptilian growth ...
One exception is medullary bone (MB), which is an ephemeral bony tissue that forms before ovulation in the marrow cavities of birds as a calcium source for ...Missing: hadrosaur | Show results with:hadrosaur
[36]
Revisiting the Estimation of Dinosaur Growth Rates | PLOS One
Quantitative comparison of the mass growth rates estimated here to ... ceratopsians, hadrosaurs, sauropods and prosauropods. This latter conclusion ...
[37]
A comprehensive osteohistological analysis of Triceratops ...
This study expands the current ceratopsian histological database and helps to better understand ceratopsid growth patterns.
[38]
[PDF] Microwear patterns on the teeth of northern high latitude hadrosaurs
This reduction in metabolic rate during the winter months may have been facilitated if these animals were inertial homeotherms. (i.e., of a low surface: mass ...
[39]
Quantitative analysis of dental microwear in hadrosaurid dinosaurs ...
Jul 7, 2009 · In terms of jaw mechanics, these data indicate an isognathic, near-vertical posterodorsal power stroke during feeding; near-vertical jaw opening ...Missing: Parasaurolophus | Show results with:Parasaurolophus
[40]
Ontogeny reveals function and evolution of the hadrosaurid ...
Jul 28, 2016 · The hadrosaurid dental battery has up to 300 teeth, with unique tooth-to-tooth attachment, and is a dynamic matrix of living and dead teeth.
[41]
Plant-eating dinosaurs evolved backup teeth to eat tough food
Aug 27, 2024 · New research has revealed just how voracious these dinosaurs were, with their average tooth worn away in less than two months as they consumed enormous amounts ...
[42]
A Comparison of the Jaw Mechanics in Hadrosaurid and Ceratopsid ...
Aug 26, 2009 · Although hadrosaurs possessed a relatively weaker bite force, their torque-adapted jaws were suited for processing more fibrous vegetation ...Abstract · ANATOMICAL REVIEW OF... · RESULTS · DISCUSSION
[43]
Feeding height stratification among the herbivorous dinosaurs from ...
Hadrosaurids were uniquely capable of feeding up to 2 m quadrupedally, or up to 5 m bipedally. There is no evidence for either feeding height stratification ...
[44]
Nasal cavity homologies and cranial crest function ... - ResearchGate
Aug 6, 2025 · The nasal passage of lambeosaurines is apomorphically enclosed by thin sheets of bone (hollow cranial crests), extending caudodorsally and ...
[45]
The Parasaurolophus' Pipes: Modeling the Dinosaur's Crest To ...
Nov 21, 2024 · Hongjun Lin from New York University will present results on the acoustic characteristics of a physical model of the Parasaurolophus' crest Thursday.
[46]
(PDF) A digital acoustic model of the lambeosaurine hadrosaur ...
Apr 22, 2016 · This model predicts steady-state frequency spectra, and can depict specific vocalizations. The crest is multiply resonant, with a main, shortest path from ...
[47]
Dinosaurian Cacophony
Indeed, these crests house an extremely modified nasal cavity, complete with all of its inte- gral, if bizarrely arranged and shaped, components. Perhaps the ...
[48]
Endocranial Anatomy of Lambeosaurine Hadrosaurids (Dinosauria ...
Aug 26, 2009 · Most hadrosaurine hadrosaurids have enlarged narial regions, suggesting that thermoregulation may have factored in the early evolution of the ...
[49]
Description and etiology of paleopathological lesions in the type ...
Dec 1, 2020 · Among these, the crested hadrosaurid Parasaurolophus walkeri is one of the most famous, largely due to its dramatic elongated and tubular nasal ...
[50]
The evolution of cranial display structures in hadrosaurian dinosaurs
Hadrosaur cranial crests were visual and acoustical display organs, with hollow crests also acting as vocal resonators, and served as premating genetic ...
[51]
(PDF) Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit ...
We show that the eyes of Mesozoic archosaurs were adapted to all major types of diel activity (that is, nocturnal, diurnal, and cathemeral)Missing: hadrosaur sclerotic
[52]
[PDF] Endocranial Anatomy of Lambeosaurine Hadrosaurids (Dinosauria
Cranial endocasts, the three-dimensional casts of the cavity that encapsulated the brain and associated tissues, provide a wealth of information on the shape of.
[53]
Neonatal state and degree of necessity for parental care in ... - Nature
Jul 10, 2025 · Pre-hatching parental care in the saurolophine Maiasaura is evident through its nests, and might be widespread in hadrosaurs as we also ...
[54]
New application of strontium isotopes reveals evidence of limited ...
Mar 4, 2020 · Hadrosaurs are therefore considered as one of the more likely dinosaur groups to undertake long-distance migrations.Missing: plains | Show results with:plains
[55]
Speeds and gaits of dinosaurs - ScienceDirect.com
Larger bipedal dinosaurs were probably restricted to walking or slow trotting gaits, with maximum speeds in the range 15–20 km/h. Most quadrupedal dinosaurs ...Missing: hadrosaur | Show results with:hadrosaur
[56]
[PDF] Osteological correlates for quadrupedality in ornithischian dinosaurs
Sep 21, 2012 · The evolution of quadrupedality from bipedal ancestors is an exceptionally rare transition in tetrapod evolution, but it has.Missing: papers | Show results with:papers
[57]
Paleopathology in Late Cretaceous Hadrosauridae from Alberta ...
May 31, 2016 · Hadrosaurs account for about 60% of all dinosaur paleopathology seen in Royal Tyrrell Museum collections (higher % in the field), the world's ...<|control11|><|separator|>
[58]
https://www.sciencedirect.com/science/article/pii/S2589004225020000
[59]
Iconic Dinosaur's injuries come to light through Queen's-led research
Dec 2, 2020 · ... Parasaurolophus, iguanodons and other smaller species, were prone to a range of injuries and diseases. “In the case of the ROM 768, torn ...
[60]
A ceratopsid-dominated tracksite from the Dinosaur Park Formation ...
The Dinosaur Park Formation at the Park is characterized by fluvial channel-belt, floodplain, and coal deposits that record sedimentation on an alluvial plain ...Missing: forests | Show results with:forests
[61]
Calibrating the zenith of dinosaur diversity in the Campanian of the ...
Sep 26, 2022 · It consists of a variety of fluvial and floodplain facies deposited seasonally across a relatively well-drained landscape. A subsequent ...
[62]
[PDF] Stratigraphy, paleontology and age of the Fruitland and Kirtland ...
The Fruitland is the source of the most im- portant coal resources in New Mexico. Together, these two formations have yielded the largest and most diverse ...
[63]
Facies architecture and depositional environments of the Upper ...
The Kaiparowits Formation is ∼ 860 m thick and constitutes nearly half of the 2 km thick succession of Upper Cretaceous strata exposed on the Kaiparowits ...Missing: Parasaurolophus | Show results with:Parasaurolophus
[64]
Revisiting the equable climate problem during the Late Cretaceous ...
Cretaceous soil carbonate clumped isotopes suggest hot summer temperatures >30 °C. Mid-latitude Cretaceous mean annual range in temperature (MART) was 21–29 °C.
[65]
(PDF) A HISTORICAL AND BIOGEOGRAPHICAL EXAMINATION OF ...
Beginning in 1979, partial skulls of Parasaurolophus were discovered, mostly attributed to P. ... Overall, the Parasaurolophus material from the Kaiparowits ...
[66]
Palaeoenvironmental drivers of vertebrate community composition ...
Nov 15, 2016 · The similarity of the dinosaur faunal assemblages between the time-equivalent portions of the Dinosaur Park Formation and Oldman Formation ...
[67]
An unusual hadrosaurid braincase from the Dinosaur Park ...
Aug 8, 2025 · The tube-crested lambeosaurine Parasaurolophus walkeri makes a rare appearance in the Dinosaur Park Formation of Alberta around 76 Ma, which ...
[68]
Dinosaur Provincial Park - Parks Canada
Sep 19, 2023 · Countless creatures flourished there - fish, amphibians, reptiles, birds, primitive mammals and about 35 species of dinosaur. When some of these ...<|control11|><|separator|>
[69]
Dinosaur Provincial Park | Research Starters - EBSCO
Plant fossils identified include fern fronds, conifer needles, and plant pollen and spores. Non-dinosaur animal fossils found include teeth and bone fragments ...
[70]
[PDF] High local variability in elevation of the Oldman-Dinosaur Park ...
The sedimentary layers of the Dinosaur Park. Formation are interpreted as successive channel meander belts cutting into (then migrating along) a wide floodplain ...Missing: forests | Show results with:forests
[71]
Flora in the Time of Chasmosaurs (botany for paleoartists, part IV)
Oct 19, 2014 · Appendix: A list of microfossil plants of Dinosaur Provincial Park · 1 species of boxwood (Buxaceae) an evergreen shrub. · 1 species of gunnera ( ...
[72]
(PDF) Description and rediagnosis of the crested hadrosaurid ...
Aug 13, 2025 · Description and rediagnosis of the crested hadrosaurid (Ornithopoda) dinosaur Parasaurolophus cyrtocristatus on the basis of new cranial remains.
[73]
EVIDENCE FOR TAPHONOMIC SIZE BIAS IN A MODEL MESOZOIC ...
Aug 10, 2025 · Taphonomy and Suggested Structure of the Dinosaurian ... Parasaurolophus from the Belly River Group (Campanian), Alberta, Canada.
[74]
12 Days of Dinosaurs: An NHMU Holiday Celebration
Dec 1, 2024 · Utah has the greatest number of Parasaurolophus fossils currently discovered, so the species is a favorite among NHMU's Paleontology team.
[75]
Hadrosaurid migration: inferences based on stable isotope ...
Apr 8, 2016 · Decreases in carbon and oxygen isotope ratios were observed in hadrosaur enamel from east to west, and overlap in isotope ratios occurred only ...
[76]
[PDF] Preservation-of-primary-stable-isotope ... - Colorado College Sites
Assuming that. δ18O of hadrosaur tooth enamel is reflecting that of ingested surface water, these patterns can be used to study hydrological conditions of the ...