A second valid species, S. angustirostris, is represented by numerous specimens from Mongolia, and was described by Anatoly Konstantinovich Rozhdestvensky.

Initial remains were not promising; a partial fragmentary ischium from Heilongjiang, China, that Riabinin named S.

[8] S. angustirostris also had a distinctive row of rectangular scales along the midline of the back and tail, known as 'midline feature-scales'; these are not currently preserved in S. osborni.

In S. angustirostris, the scales on the tail flank were arranged in vertical patterns, which may have corresponded to striped coloration in life.

This area was covered in radial scale patterns in S. osborni, possibly indicating a more mottled or spotted coloration.

Bell found in a publication earlier in the year that the two previous studies of S. angustirostris, by Rozhdestvensky in 1952, and Maryanska and Osmolska in 1981, do not provide a comprehensive enough description to compare the species with S.

[13] Saurolophus is known from material including nearly complete skeletons, giving researchers a clear picture of its bony anatomy.

The most unusual feature for a hadrosaurine is the long, protruding, solid crest that extends upwards diagonally from the back of the skull roof.

[18] The following cladogram of hadrosaurid relationships was published in 2013 by Alberto Prieto-Márquez et al. in Acta Palaeontologica Polonica:[19] Acristravus gagstarsoni Brachylophosaurus canadensis Maiasaura peeblesorum Shantungosaurus giganteus Edmontosaurus regalis Edmontosaurus annectens Kerberosaurus manakini Sabinas OTU Prosaurolophus maximus Saurolophus morrisi (now Augustynolophus) Saurolophus osborni Saurolophus angustirostris Wulagasaurus dongi Kritosaurus navajovius Big Bend UTEP OTU Secernosaurus koerneri Willinakaqe salitralensis Gryposaurus latidens Gryposaurus notabilis Gryposaurus monumentensis As a hadrosaurid, Saurolophus would have been a bipedal/quadrupedal herbivore, eating a variety of plants.

Brown compared it to the crest of a chameleon, and suggested it could provide an area for muscle attachment and a connection point for a nonbody back frill like that seen in the basilisk lizard.

[20] Maryańska and Osmólska, noting the hollow base, suggested that the crest increased the surface area of the respiratory cavity, and helped in thermoregulation.

[21] This idea has been picked up by authors of popular dinosaur works, such as David B. Norman, who discussed hadrosaurid display at length and included a life restoration of such an adaptation in action.

Based on these juveniles, Dewaele and team indicated that during the ontogeny of S. angustirostris the distinct crest found in adults was poorly developed in infancy, the snout grew proportionally longer, the orbit became more oval-shaped, the doming of the frontal became less prominent, and the coronoid process became higher.

[23] Bell and team in 2018 described the famous Dragon's Tomb assambleage of the Altan Uul II locality, Nemegt Formation, which contains a large-sized bonebed of S. angustirostris.

Hone and Mahito Watabe in 2011 reported the left humerus of a nearly complete S. angustirostris skeleton (MPC-D 100/764) from the Bügiin Tsav locality of the Nemegt Formation, which was heavily damaged from bite marks attributed to the sympatric Tarbosaurus.

As suggested by the lack of damage to the rest of the skeleton (such as large wounds in skeletal remains indicative of predation), this tyrannosaurid was likely scavenging an already dead S. angustirostris.

[25] Comparisons between the scleral rings of Saurolophus and modern birds and reptiles suggest that it may have been cathemeral, active throughout the day at short intervals.

The formation is interpreted as having a significant marine influence, due to an encroaching Western Interior Seaway, the shallow sea that covered the midsection of North America through much of the Cretaceous.

[7] It lived alongside other dinosaur species including the ornithopods Hypacrosaurus altispinus and Parksosaurus warreni, ankylosaurid Anodontosaurus lambei, pachycephalosaurid Sphaerotholus edmontonense, ornithomimids Dromiceiomimus brevitertius and an unnamed species of Struthiomimus, small theropods including Atrociraptor marshalli and Albertonykus borealis, and the tyrannosaurid Albertosaurus sarcophagus.

[30] S. angustirostris was one of the largest herbivores of the Nemegt Formation, which lacked large ceratopsians, but had sauropods and a more diverse theropod fauna.

[27] When examined, the rock facies of the Nemegt formation suggest the presence of stream and river channels, mudflats, and shallow lakes.

Sediments also indicate that a rich habitat existed, offering diverse food in abundant amounts that could sustain Cretaceous dinosaurs.

By comparison, S. osborni was rare in the Horseshoe Canyon Formation, and faced competition from other duckbills (genus Hypacrosaurus).