User:Vulpestooth/Dinosaur reproduction

The content is relevant but it focuses mostly on care. Dinosaur reproduction probably included more migration to areas to mate, mating performances, dimorphism, and parental care. It is written neutrally and claims do have sources.

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Dinosaur reproduction shows correlation with archosaur and avian physiology, with newborns hatching from eggs that were laid in nests. Dinosaurs did not nurture their offspring as mammals typically do, and because dinosaurs did not nurse, it is likely that most dinosaurs were capable of surviving on their own after hatching. Although, parental care may have been require for some dinosaur species, as shown by fossil evidence. Dinosaur reproduction also required a mate; evidence of sexual dimorphism and courting displays have been found from fossil scrapings in sandstone and feathers on dinosaurs that lacked flight.

Dinosaur Mating displays

Sexual Dimorphism

Research and modern day birds suggest that dinosaurs had various methods of acquiring mates, ranging from biological traits such as sexual dimorphism, to mating displays such as dancing. Some dinosaurs, like Ornithomimids, had feathered arms resembling wings but their bodies were too heavy for flight. These wings were potentially used in mating displays, like some birds plumage does today. Older studies also suggest that dinosaurs like the Lambeosaurus may have used their specialized hollow horn structures to create vocalizations specific to mating. Both male and female fossils have been found, indicating these horn structures were not specific to one gender but these specialized hollow horns could have been brightly colored in order to distinguish males from females of the same species. Stegosaurus fossils have potential sexual dimorphism in the shape of their back plates, with males having rounder and wider back plates while female's have taller more diamond shaped back plates. These plates may have displayed colors and been a sign of health in males, while female's plates acted as defense, like a cow's horns.

Mating Behavior

Large scrapes in the sandstone of Colorado suggests that dinosaurs may have danced in order to impress a potential mate, a behavior seen in their successors, birds. The scrapings in the sandstone were interpreted to be evidence of mating displays areas or courtship sights, as there was no evidence of eggs in the area.

Psittacosaurus nest

Parental Care

Many dinosaurs fossils reflect instances of parental care and egg care. One fossil of the Pisttacosaurus sp. shows thirty-four juveniles of similar size buried along with an adult, a presumed care-taker. The bone development of the juveniles suggests a slow growth rate, and the overall amount of young found together, indicates post-hatching growth that was dependent on extensive parental care. An assemblage of Protoceratops Andrewsi juveniles were found of similar size and age, suggesting that they were from the same nest. These dinosaurs were found without the presence of egg shells in an oval-shaped nest, meaning that these animals grew together after hatching, potentially with some parental care.

An Oviraptorosaurian nest, species unidentified.

Nest Building

Two main types of nest construction have been highlighted in fossils. Mound-nesting, as seen in modern archosaurs, were built-up nests made of mostly plant materials or soil. Eggs were then laid in the mound and covered to incubate through organic heat sources like decomposition of the plant material. These mound nests would allow the eggs to incubate without needing to be sat on and rotated. Mound-nesting was the only option for larger dinosaurs, like sauropods, that were unable to sit on their eggs to provide warmth. The eggs of hadrosaurs have been associated with fine-grain pedogenic sediments, where eggs were left to incubate via microbial respiration. Early dinosaur eggs also lacked color, suggesting that the eggs did not need to blend in with the environment to avoid predation, as they were hidden in mounds while incubation occurred. Other dinosaurs may have incubated their eggs using their body heat and feathers, like oviraptors and troodontids which have been documented sitting over their eggs in semi-open nests that were at least partly exposed during incubation.