Hypacrosaurus ‭(‬near the highest lizard‭)‬

Short Info

Hypacrosaurus ‭(‬near the highest lizard‭)‬

Phonetic : Hie-pak-roe-sore-us.

Named By : Barnum Brown‭ ‬-‭ ‬1923

Diet : Herbivore

Size : Estimated 9 meters long

Type of Dinosaur : Euornithopod

Type Species : H.‭ ‬altispinus‭ (‬type‭)‬,‭ ‬H.‭ ‬stebingeri

Found in : Canada‭ ‬-‭ ‬Alberta‭ ‬-‭ ‬Horseshoe Canyon Formation.‭ ‬USA‭ ‬-‭ ‬Montana‭ ‬-‭ ‬Two Medicine Formation

When it Lived : Late Cretaceous, 70 million years ago

Hypacrosaurus, which means “nearest the highest lizard” (Greek upo, hypo- = less + Akros, akros), was a genus that contained duckbill dinosaurs similar to Corythosaurus. It had a tall hollow-rounded crest similar to Corythosaurus. However, its crest was not as straight and large. It is based on the remains of two species, which date back to 75 to 67 millions years ago in the Late Cretaceous of Alberta and Montana, Canada. This is the most recent hollow-crested duckbill found from North America. It was an obscure genus before the discovery of nests, eggs and hatchlings from H. stebingeri in the 1990s.

Hypacrosaurus Royal TyrrellEtemenanki3, CC BY-SA 4.0, via Wikimedia Commons

Barnum Brown, American Museum of Natural History, collected the type remains of Hypacrosaurus in 1910. A partial postcranial skull consisting of several vertebrae, and a partial pelvis (AMNH 524) was found along the Red Deer River, Alberta, Canada. It was formed from rocks in the Horseshoe Canyon Formation (early Maastrichtian; Upper Cretaceous). Brown described the remains in conjunction with other postcranial bone fragments in 1913 as a new species that he compared to Saurolophus. Two skulls, however, were discovered quickly and later described.

The remains of small hollow-crested duckbills from this time period were identified as their own species and genera. Cheneosaurus Tolmanensis was the first to be included in the history of Hypacrosaurus. It was based on a skull, assorted limb bones and pelvic bones of the Horseshoe Canyon Formation. Nelda Wright and Richard Swann Lull identified a skeleton from the American Museum of Natural History (AMNH 5461), as a Procheneosaurus specimen shortly after. These taxa and others were accepted as valid genera up until the 1970s when Peter Dodson demonstrated that it was more likely the “cheneosaurs”, were juveniles of established lambeosaurines. He was primarily concerned with the Dinosaur Park Formation genera Corythosaurus & Lambeosaurus. However, he suggested Cheneosaurus might be composed of young Hypacrosaurus Altispinus. Although this idea is accepted [9], it has not been formally tested. The Two Medicine Procheneosaurus was, however, not like the other Procheneosaurus samples studied by Dodson. This was due to its more similarity to H. stebingeri, a species that was not named until 1994.

Hypacrosaurus altispinus, headD. Gordon E. Robertson, CC BY-SA 3.0, via Wikimedia Commons

Hypacrosaurus can be distinguished from other hollow-crested duckbills by its tall neural spines, and its crest. The neural spines extend from the top of each vertebrae. This would give Hypacrosaurus a high profile back. The hollow crest of the skull is similar to that of Corythosaurus. However, it is shorter at its top and wider on both sides. It also has a small bony point at its rear. The passages to the airways are not curved in the crest, unlike other lambeosaurines. It is believed that the animal measured 9.1 metres (30 feet) in length and weighed in at 4.0 tonnes (4.4 tonnes). Although its skeleton is not very remarkable, it is similar to most duckbills. However, there are some distinctive pelvic details. It was bipedal/quadrupedal herbivore, just like other duckbills. H. altispinus, and H. stebingeri are not distinguished in the usual method. However, H. stebingeri has unique characteristics. H. stebingeri is described as a transitional species between the Lambeosaurus and the Hypacrosaurus.

Source: Wikipedia