Long known as hadrosaurines
(after Hadrosaurus, which instead seems to be more basal), and also known informally as the
"flat-headed duckbills" (a misnomer, since it will quickly become clear that
most "flat-heads" possess cranial ornamentation of some sort), saurolophines
could be better defined as lacking hollow crests. Unlike the lambeosaurines,
saurolophines are known from good remains to have existed at the very end of the Mesozoic.
Saurolophines may sort into several general groups, although the exact composition of these groups is uncertain (people have been largely leaving saurolophine phylogeny alone except for review articles and the occasional description of a new taxon, which is a shame given so much good material; results may vary). Given this, I'm just going to throw all the valid saurolophines together in one table, by alphabetical order no less. Here are two comparable but noticeably different phylogenies.
Saurolophinae: The "gryposaurins" (officially Kritosaurini) are known for their arched, flattened nasal regions, giving them a bulbous nose area in lateral view. It has been suggested that they may have used their nasal arches in nudging contests.
The "edmontosaurins" (just Edmontosaurus for certain at this point, but Kerberosaurus and Kundurosaurus may be East Asian examples) include the only truly flat-headed saurolophines, with expanded beaks and little bony cranial ornamentation. They have undergone a great deal of naming turmoil over the years, which could have at least been alleviated if Cope ("Diclonius mirabilis", eventually Anatosaurus or Anatotitan copei on its way to Edmontosaurus annectens) and Marsh (Claosaurus annectens, now Edmontosaurus annectens) had not belied their reputations and given their good specimens their own genera (or, in Cope's case, even a species! Four species of Dysganus and three of Diclonius just for teeth, but reusing Trachodon mirabilis for a complete skull and nearly complete skeleton? Come on!). The "saurolophins" are known for possessing a nasal crest without a gryposaur-like arch, sometimes forming a long spine that may have supported a skin sail, and sometimes forming small pyramidal shapes. As with other hadrosaurids, it has been suggested fleshy air sacs ran along the expanded nasal depressions, that could be inflated for display. The "maiasaurins" (officially Brachylophosaurini) had a unique broad, solid crest on the head.
|Taxon or Taxa:||Time/Place:||Comments:|
|Acristavus gagslarsoni Gates, Horner, Hanna, and Nelson, 2011||middle Campanian (LK) of Montana and Utah||Going by the traditional definitions, Acristavus is a rarity, a truly crestless "flat-headed hadrosaur". It was a brachylophosaurinid, sharing a prominent long and tall snout with Brachylophosaurus itself; however, anatomically it was closer to Maiasaura. It was named from a partial skull and skeleton from the Two Medicine Formation in Montana, with an additional skull roof referred to it from roughly equally-old rocks of the Wahweap Formation of southern Utah, giving it a substantial geographic distribution. Acristavus was one of the older hadrosaurines.|
|Barsboldia sicinskii Maryanska and Osmolska, 1981||early Maastrichtian (LK) of Mongolia||This animal is based upon most of the rear half of one individual. It has very tall neural spines with unique club-like expansions at the ends, possibly pathological in origin. It was long thought to be a lambeosaurine, possibly similar to Hypacrosaurus.|
|Brachylophosaurus canadensis Sternberg, 1953 (including B. goodwini Horner, 1988)||late middle Campanian (LK) of Alberta and Montana||An unusual and heretofore somewhat rare Judithian
saurolophine, Brachylophosaurus had a broad, solid, slightly
keeled but for the most part flat plate on top of the
head, with a short, spine-like projection over the rear of the skull. It has been
suggested this reinforced skull roof was used in intraspecific (same-species) pushing
contests. A new, essentially complete skeleton of a subadult
("Leonardo") has been found, with preservation of soft elements.
When first discovered in 1936, what would become the type skull was thought to belong to a Gryposaurus-type animal, which isn't too far off the mark. The snout is quite tall and compressed, like the latter's, but not arched.
In addition to the distinctive skull, the forearms are unusually long for a hadrosaur. Referred to the type species is B. goodwini, based on a skull with the typical brachylophosaur plate interrupted by a depression. There is a fair amount of variation within the genus.
|Edmontosaurus: Lambe, 1917 (including Anatotitan Brett-Surman vide Chapman and Brett-Surman, 1990)||E. regalis (type) Lambe, 1917 (including Thespesius edmontoni [aka edmontonensis] Gilmore, 1924)||latest Campanian (LK) of Alberta||This was a very plain animal, for a saurolophine, but also one of the largest at 30 to 40 feet
is fairly common, with remain belonging to at least a dozen individuals
known. With Triceratops, Edmontosaurus
dominated the dinosaurian herbivores at the end of the Cretaceous in
western North America.
Finally a bit more clarity has emerged on the various species assigned to Edmontosaurus. For those of you arriving late, a half-dozen species spent decades (as far back as the 1880s) going between Anatosaurus, Anatotitan, Claosaurus, Diclonius, Edmontosaurus, Hadrosaurus, Thespesius, and Trachodon. It now appears that there were only two diagnostic species, the type species E. regalis and E. annectens. E. regalis includes Thespesius edmontoni, which surely wins a coveted prize as one of the most obscure dinosaurs to be based on good material. E. regalis is limited to the lower Horseshoe Canyon Formation of Alberta.
E. annectens was for a long time known under the guise of Anatosaurus. This is the species represented by the two "Sternberg mummies," one in the American Museum of Natural History and one in the Senckenberg Museum. Assigned to it are the fossils described as Thespesius saskatechwanensis and Anatotitan copei via Diclonius through Anatosaurus (it's a long story, hinging on Edward Drinker Cope defying all of his history by refraining to give a new name to an excellent specimen). It is known only from the very end of the Cretaceous, and differs from E. regalis most obviously by developing a very long flat skull with age.
Thespesius saskatchewanensis, also known as Anatosaurus saskatchewanensis, is based on a small skull and partial skeleton, with a few others referred to it. It doesn't get much press, and historically just shows up in reviews as its own species without much comment.
Anatotitan copei (better known before as one of the Anatosaurus species) was famous as the most duck-billed of the "duck-billed dinosaurs," with an amazingly long beak. Historically, it is known from the two mounted skeletons in the American Museum of Natural History. The (published) push to sink it into E. annectens began in 2004 with the hadrosaur chapter of The Dinosauria II, where the two skulls were described as more mundane skulls that had been crushed the same way, which seemed anticlimactic, to say the least. More recent work has found copei to be at the end of a continuum of annectens, which makes more sense.
A skeleton bearing small theropod nibbling about the jaws, indicating a survived attack on the neck, is known, and Edmontosaurus in general appears to have taken a fair amount of abuse from theropods (see for example a tail bitten by a tyrannosaurid and later healed).
Anatotitan is often given an upper length of 40 ft. However, that doesn't seem right if you track down the numbers; the 40 ft measurement comes from Cope's specimen ("Diclonius mirabilis", one of the two in the AMNH) which was later downsized substantially. I can't find any other 40-footers, unless the legendary Trachodon longiceps (a lower jaw of healthy proportions) is invoked. Did the original Cope estimate just stick? E. regalis is also usually depicted as reaching 40 ft, but finding a specimen measured at near this and not just estimated at 30 to 40 ft long is work.
Soft tissue remains, generally skin impressions, are known from several specimens, and cover much of the body (except, of course, for the face, unless somebody's holding out). There appears to have been some sort of odd non-bony ridge or bump at the back of the head.
|E. annectens (Marsh, 1892 [originally Claosaurus]) (including Thespesius saskatchewanensis Sternberg, 1926, Anatosaurus copei Lull and Wright, 1942, possibly Trachodon longiceps [N.D.] Marsh, 1890)||late Maastrichtian (LK) of Montana, Saskatchewan, South Dakota, and Wyoming|
|Gryposaurus: Lambe, 1914||G. notabilis (type) Lambe, 1914 (including Kritosaurus incurvimanus Parks, 1920)||late middle-early late Campanian (LK) of Alberta||Gryposaurus is very
the name Kritosaurus notabilis. For a long time Kritosaurus and Gryposaurus
were considered to be the same genus, but since about 1990 it has become
clear that the type material of Kritosaurus is not as diagnostic
as one would prefer, based as it is on a
fragmentary skull. Gryposaurus, meanwhile, is based on much better remains.
Interestingly, it now appears that Kritosaurus may actually be a
"saurolophinid", instead of a "gryposaurinid", illustrating the problems of establishing
hadrosaurid taxa on material that is either missing or has an inadequately preserved
skull. Gryposaurus is a fairly common Judithian saurolophine.
G. incurvimanus was often listed as its own species in the past. It was pretty much the same thing as G. notabilis, except its humerus was more robust, the rest of it was more gracile, and its nasal arch was farther forward; however, the G. incurvimanus skull is also somewhat smaller than those of G. notabilis, and the nasal crests move backwards with age in Prosaurolophus, so I'm willing to suggest that's what's happening here. G. incurvimanus was based on a nice skeleton with scale impressions.
G. monumentensis is based on a skull and a good chunk of the skeleton with skin impressions, and is a more robust species. There may also be a gracile gryposaur in the same Kaiparowits beds.
|G. latidens Horner, 1992||late Santonian-early Campanian (LK) of Montana|
|G. monumentensis Gates and Sampson, 2007||early late Campanian (LK) of Utah
|Kerberosaurus manakini Bolotsky and Godefroit, 2004||?late Maastrichtian (LK) of Russia||Another new LK hadrosaur from the far-eastern Amur region of Russia, Kerberosaurus is based on a braincase with referred remains that together make up much of a skull. What is known of the nasal indicates no large Gryposaurus-style arch or other extreme ornamentation. It, Kundurosaurus, and Edmontosaurus may form a clade.|
|Kritosaurus: Brown, 1910 (including Anasazisaurus, Hunt and Lucas, 1993)||K. navajovius (type) Brown, 1910||middle late Campanian (LK) of New Mexico||Sometimes featured in older
dinosaur books as a saurolophine with a Gryposaurus-type nasal
arch, this animal is based on a skull that does not preserve a complete
nasal area and was originally restored in a flat manner. Chunks of
it show some sort of ornamentation, but at the time, Brown didn't know
what to do with them, having only what would become Edmontosaurus
annectens and copei to go on as skull models. Indeed,
people are still piecing bits onto the skull from the collected fragments.
It is often pictured with a Gryposaurus nasal
arch because for several decades, it was thought to be the same thing as
the much better known Canadian taxon. It may have been closer to Saurolophus,
and differs from Gryposaurus in age, location, and cranial details
(although the new Utah material muddies the location waters; what we
really need are a few good K. navajovius skulls with the adult
Material from the earliest middle Campanian of Texas, including a skull and hand, may belong to a new species. Material from Mexico may indicate a species 20% larger than K. navajovius, around 11 m long, but at this time the material does not have distinctive characteristics.
In 1993, Hunt and Lucas took two skulls that Horner had just assigned to K. navajovius and gave them their own genera: Anasazisaurus and Naashoibitosaurus. Both are largely based on skulls missing the lower jaw and beak (Naashoibitosaurus has some postcrania, too) with nasal crests that grossly are halfway between Prosaurolophus and Gryposaurus in form, sort of tabs between the eyes. Anasazisaurus is known from slightly older rocks than K. navajovius and its crest overhangs the eyes, like a little handle. My opinion had been that Anasazisaurus horneri could be considered a species of Kritosaurus, and Naashoibitosaurus a partially grown example of K. navajovius, but only the first has been borne out so far.
|K. horneri (Hunt and Lucas, 1993 [originally Anasazisaurus])|
|Kundurosaurus nagornyi Godefroit, Bolotsky, and Lauters, 2012||late? Maastrichtian (LK) of Russia||Kundurosaurus, a less-abundant contemporary of the lambeosaurine Olorotitan, is known from partial cranial and postcranial (mostly pectoral, pelvic, and arm material) remains. Much of the skull has been found, showing an Edmontosaurus-like crestless profile.|
|Latirhinus uitstlani Prieto-Márquez and Serrano Brañas, 2012||late Campanian (LK) of Mexico||Latirhinus is among the saurolophines with an exaggerated, arched nasal. It is based on a partial skull and skeleton; I suspect it may have something to do with other saurolophines from the same region, such as large PASAC-1, but this will have to wait.|
|Maiasaura peeblesorum Horner and Makela, 1979||middle-late Campanian (LK) of Montana||Known from nesting colonies and copious skeletal remains
found in the last quarter-century, Maiasaura has a short, broad projection
somewhat akin to a shelf above the eyes. It is known to have congregated in groups,
possibly in numbers upward of 10,000 in some cases, and is famous for the care it appears
to have given its young in the nest. It is part of a distinctive subset of the
Judithian fauna, from the Two Medicine Formation.
Studies of the young indicate a shift from bipedality to quadrupedality with age; this may hold true for hadrosaurids in general.
|Naashoibitosaurus ostromi Hunt and Lucas, 1993||middle late Campanian (LK) of New Mexico||Naashoibitosaurus is based on a skull previously described as Kritosaurus, and which I have described as probably just a juvenile Kritosaurus navajovius. Naashobitosaurus, when given a new genus, was thought to be from much younger strata than Kritosaurus (which gave it its name), but this turned out to be incorrect.|
|Prosaurolophus maximus Brown, 1916 (including P. blackfeetensis Horner, 1992)||middle-early late Campanian (LK) of Alberta and Montana||A somewhat nondescript large saurolophine, Prosaurolophus
had a short pyramid between the eyes. It is known from remains
belonging to over 30 individuals of a variety of ages, including
juveniles, and has been suggested as the ancestor of Saurolophus,
hence the name.
P. blackfeetensis was differentiated from P. maximus by details of the nasal pertaining to crest size and extent of the depression around the nostril; essentially, it had a taller skull profile and bonebed remains.
|Saurolophus: Brown, 1912||S. osborni (type) Brown, 1912||middle Maastrichtian (LK) of Alberta||A characteristic Edmontonian dinosaur, S. osborni is known from the remains of at least three individuals. It had a prominent rear-facing spine between its eyes.|
|S. angustirostris Rozhdestvensky, 1952||early Maastrichtian (LK) of Mongolia||Usually considered solidly Saurolophus, this animal is one of the most common Nemegt dinosaurs. Like S. osborni, there is a prominent rearward spine projecting from between the eyes. Some workers have suggested that it belongs in its own genus, while others believe it could be the same as S. osborni.|
|S. morrisi Prieto-Márquez and Wagner, 2010||late Maastrichtian (LK) of California||S. morrisi is known from two partial skeletons. It is outside of the S. osborni+S. angustirostris group, but shares the "pinching" of the end of the snout that gives Saurolophus a slight "kissy face". (I guess I'd always thought that it was some sort of preservational thing, but it's actually real)|
|Secernosaurus koerneri Brett-Surman, 1979 (including Kritosaurus australis Bonaparte, Franchi, Powell, and Sepulveda, 1984)||late Campanian-early Maastrichtian (LK) of Argentina||For several decades, the named hadrosaurids of South America were limited to Secernosaurus, which was generally overlooked because it was based on a fragmentary skeleton, and Kritosaurus australis, which was generally overlooked as well. In hindsight, it's a little difficult to see how it acquired a nasal hump in skeletal mount form given that no nasal bone is mentioned among the material, except via comparison with North American Kritosaurus; fair enough, I suppose, but these display characteristics are variable, and even if they are closely related, they shouldn't necessarily be expected to have the same arch. Secernosaurus had more of a claim to fame, being the first hadrosaurid described from South America, but K. australis had much more material available. Upon further review, though, it turns out that they are the probably the same genus and species.|
|Shantungosaurus giganteus Hu, 1973 (?Edmontosaurus) (?including Zhuchengosaurus maximus Zhao X., Li D., Han G., Hao H., Liu F., Li L., and Fang X., 2007, and Huaxiaosaurus aigahtens Zhao X., Wang K., and Li D. J., 2011)||?early-middle Maastrichtian (LK) of China||Possibly the largest known ornithopod at around fifty feet
(15 meters) in length and several tons in weight for an average adult, this animal is based on
nearly complete skeletal remains from five individuals, which are said to differ from Edmontosaurus regalis
mainly in size-related details, and so could be a species of Edmontosaurus.
It had an
Zhuchengosaurus maximus is another giant hadrosaurid, coincidentally from the same rocks and the same place. It was thought to differ from Shantungosaurus based on vertebral count (particularly having one fewer sacral) and being slightly larger. It is more probable that the two are the same, especially given the disarticulated nature of the fossils. Huaxiasaurus is in almost exactly the same boat.
|Willinakaqe salitralensis Valieri, Haro, Fiorelli, and Calvo, 2011||late Campanian-early Maastrichtian (LK) of Argentina||Formerly known as the "Salitral Moreno" taxon, and even farther back as a possible lambeosaurine, Willinakaqe is known from a variety of cranial and postcranial materials corresponding to multiple growth stages. This genus was closely related to the other South American hadrosaurid, Secernosaurus. It is not known if it had any cranial ornamentation. The neural spines on the sacrals and caudals were tall.|
|Wulagasaurus dongi Godefroit, Hai S., Yu T., and Lauters, 2008||Maastrichtian (LK) of China||Wulagasaurus is a basal saurolophine known from isolated remains found in the Sahaliyania bonebed; such remains include partial upper and lower jaws, braincases, part of the pectoral and pelvic girdles, and humeri. It was described as the basalmost saurolophine, which would suggest an Asian origin for Saurolophinae and Hadrosauridae.|
|Taxon or Taxa:||Time/Place:||Comments:|
|"Trachodon" amurensis (N.D.) Riabinin, 1925 (Mandschurosaurus)||early-mid Maastrichtian (LK) of China, ?Coniacian-?Maastrichtian (LK) of Russia||Better known as Mandschurosaurus, this is based on large, very fragmentary remains of at least one type of hadrosaurid (a saurolophine), lacking a well-preserved skull, almost a death sentence for hadrosaurid taxa, as they often can only be told apart by their skulls. New material is apparently known, though, although the proliferation of Amur River region hadrosaurids makes cleanly assigning anything an interesting proposition.|
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