The lambeosaurines are the
hollow-crested hadrosaurids. On the whole, they are more robust in build when
compared to the saurolophines, and tend to have more elongated neural spines than the
saurolophines, giving them more of a fin-back. In North America, they are most common in the
fauna (Corythosaurus could be the poster-hadrosaurid for Dinosaur
Provincial Park), are less common in the Edmontonian,
and finally are almost unknown in the Lancian (possible
remains in the Hell Creek Formation of Montana),
suggesting that they virtually disappear altogether before the end of the
Mesozoic. It had been thought that lambeosaurines went extinct in the early
Maastrichtian, based on North American remains. In recent years,
though, a diverse late Maastrichtian fauna from the Chinese-Russian border in
the Amur River region has been described, including Amurosaurus, Charonosaurus,
The function or functions of the lambeosaurine crest has long been debated. When hadrosaurids were considered to have been water-dwellers, the crests of lambeosaurines, especially that of Parasaurolophus, were drafted into service as possible snorkels or air-traps to increase underwater feeding time. Other proposed uses included foliage deflectors for aiding forest running, salt glands, and extra space for the sense of smell. Today, it is believed that they were primarily display and signaling devices, useful to gregarious animals, which hadrosaurids appear to be. The hollow spaces in the crests, connected to the windpipe and nostrils, could have produced low-pitched honks when the animal breathed in a certain way, and the crests themselves could have been very colorful or have provided attachments to colorful skin sails. In the better-known lambeosaurines, crest forms believed to belong to juveniles, adult males, and adult females have been identified, with the adult male crests most prominent and the female and juvenile gear more subdued. The crests appear to have begun growth from in front of the eyes as bulges, giving some juveniles a vague resemblance to Gryposaurus in external skull morphology.
It is also probable that beside signaling and display, the crests had other functions. Some auxiliary functions suggested include thermoregulation (somewhat like what some stegosaurians may have done with their plates), improving the sense of smell, and warming the air breathed in.
Lambeosaurines can be divided into two general groups: Parasaurolophini and Corythosaurini (which by priority should be Lambeosaurini, but I digress). Parasaurolophini is as yet not as well-defined or well-supported as Corythosaurini, which is composed of several closely-related taxa. In fact, it has been suggested that Lambeosaurus, Corythosaurus, and Hypacrosaurus are similar enough to each other to allow for them to be classified under the same genus: Hypacrosaurus.
|Taxon or Taxa:||Time/Place:||Comments:|
|Aralosaurus tuberiferous Rozhdestvensky, 1968||Turonian-Coniacian (LK) of Kazakhstan||Aralosaurus is known from much of a skull that preserves a distinctive arched nasal region. In the past, it has been tied to the "gryposaur" saurolophines, from the idea that the crest represented a gryposaur-style nasal arch, but recent research suggests that instead what we see is a small hollow lambeosaurine nasal crest, and that this is the most basal lambeosaurine.|
|Jaxartosaurus aralensis Riabinin, 1939||Turonian-?Santonian (LK) of Kazakhstan||This animal is based on a partial braincase from a young individual, showing the characteristic swelling in front where the crest grows.|
|Pararhabdodon isonensis Casanovas-Cladellas, Santafe-Llopis, and Isidoro Llorens, 1993 (?Koutalisaurus)||Maastrichtian (LK) of Spain and ?France||Pararhabdodon has gone through several reassessments. It was originally described as a basal iguanodontian somewhat like Rhabdodon, then as a small lambeosaurine, then as a basal hadrosaurid close to the saurolophine-lambeosaurine split, and now again a lambeosaurine, possibly in a clade with Tsintaosaurus.|
|Tsintaosaurus spinorhinus Yang, 1958||early-mid Maastrichtian (LK) of China||This animal is famous for the unicorn-like spine projecting from its skull. This has been called into question in the past, and accused of being created by skull-bone displacement after death, but other remains appear to show it existed, albeit in somewhat different form. A skin sail may have been attached to it. Tsintaosaurus is based on chimerical remains, belonging to both lambeosaurines and saurolophines. Today it is usually limited to the lambeosaurine remains. The saurolophine remains appear to come from an animal like Tanius. The name is not pronounced like how it looks like it may sound, but instead along the lines of "ching-dow saurus." Although here a more basal lambeosaurine, it could also be aligned with Parasaurolophus.|
|Amurosaurus riabinini Bolotsky and Kurzanov, 1991||late Maastrichtian (LK) of Russia||This is a large Russian lambeosaurine, based on a partial skull with a large amount of referred skeletal material (although Charonosaurus and Olorotitan surely muddy the waters as far noncranial material goes). The crest is not preserved, but has been restored in "corythosaur" mode based on the rest of the skull. It may be basal to the parasaurolophinid/corythosaurinid split.|
|Sahaliyania elunchunorum Godefroit, Hai S., Yu T., and Lauters, 2008||Maastrichtian (LK) of China||Sahaliyania marks the fourth new lambeosaurine from the Amur River region, which is suddenly becoming quite the hotspot for these things. As in several other cases, its remains come from a very productive bonebed of multiple individuals, and we don't have a complete crest.|
|Taxon or Taxa:||Time/Place:||Comments:|
|Angulomastacator daviesi Wagner and Lehman, 2009||late Campanian (LK) of Texas||Angulomastacator is based only on a partial maxilla, but it's pretty distinctive. It's curved downward (halfway between a boomerang and a banana in shape), with the tooth row curved to match. This leaves the interesting question of what it was doing that made bending the front of its face and jaws 45° down useful. Its name "bend chewer" has a double meaning, referring both to the facial geometry and to its being found from Big Bend.|
|Arenysaurus ardevoli Pereda-Suberbiola, Canudo, Cruzado-Caballero, Barco, López-Martínez, Oms, and Ruiz-Omeñaca, 2009||late Maastrichtian (LK) of Spain||Arenysaurus is a basal lambeosaurine, possibly basal to Amurosaurus. It is known from cranial and postcranial remains (frustratingly, we've now got several basal lambeosaurines with good skeletons, but we don't have much for their crests yet). It was one of the last hadrosaurids.|
|?Arstanosaurus akkurganensis (N.D.) Suslov and Shilin, 1982||Santonian-Campanian (LK) of Kazakhstan||This animal was originally described as a hadrosaurid, but is sometimes referred to as a neoceratopsian; the teeth were initially described as double-rooted, like those of ceratopsids, but this has turned out to be in error. Referred juvenile remains from the Santonian of Mongolia also may belong here.|
|Blasisaurus canudoi Cruzado-Caballero, Pereda-Suberbiola, and Ruiz-Omeñaca, 2010||late Maastrichtian (LK) of Spain||Blasisaurus is known from skull and jaw bones from an animal closely related to Arenyasaurus.|
|"Hadrosaurus" paucidens (N.D.) Marsh, 1889||late middle Campanian (LK) of Montana||This animal, based on a squamosal and maxilla, appears to be a lambeosaurine hadrosaurid, although at one point it was thought to be a ceratopsid.|
|Koutalisaurus kohlerorum Prieto-Márquez, Gaete, Rivas, Galobart, and Boada, 2006 (?Pararhabdodon)||Maastrichtian (LK) of Spain||Koutalisaurus is based on a distinctive dentary that is steeply curved inward and down, giving it a spoon-shaped jaw. The type had been referred to the contemporaneous Pararhabdodon, and the two may be synonyms.|
|Nanningosaurus dashiensis Mo J., Zhao Z., Wang W., and Xu X., 2007||LK of China||The first named valid hadrosaurid from southern China, Nanningosaurus seems to be a basal lambeosaurine, featuring expanded ischial tips. It is based on a partial skeleton including skull bones, a partial scapula, both humeri and tibiae, an ischium, a femur, and a cervical.|
|Nipponosaurus sachalinensis Nagao, 1936||late Santonian-early Campanian (LK) of "Russia"||Found on Sakhalin Island, which was at the time of discovery a Japanese holding (now owned by Russia), hence the name, this animal is a juvenile lambeosaurine. It may be the same as another lambeosaurine. Recent research suggests it could be particularly close to Hypacrosaurus.|
|"Procheneosaurus" convincens (N.D.) Rozhdestvensky, 1968||Turonian-Santonian (LK) of Kazakhstan||This indeterminate taxon, based on a nearly complete skeleton, may be an early lambeosaurine, or the same as Jaxartosaurus.|
|Taxon or Taxa:||Time/Place:||Comments:|
|Charonosaurus jiayinensis Godefroit, Zan, and Jin, 2000||late Maastrichtian (LK) of China||Charonosaurus, the first definite Late Maastrichtian lambeosaurine, and the first good-quality lambeosaurine skull from Asia, is known from a partial skull with a possibly Parasaurolophus-like tube crest and bonebed material. It was quite large, with one femur measuring 135 cm (about 53 inches) long. A few probable synonyms are floating around, including the lengthy "Heilongjiangosaurus". Even more odd is the possibility that it is synonymous with Mandschurosaurus (better known here as "Trachodon" amurensis).|
|Parasaurolophus: Parks, 1922||P. walkeri (type) Parks, 1922||late middle Campanian (LK) of Alberta||Parasaurolophus is a rare but famous
lambeosaurine, instantly recognizable from the long bony tube projecting from the top-rear
of the skull in a graceful curve. This tube has a number of internal
passages, and is more complex than previously thought.
The main passages start at the nostril, head back the length of the crest, turn
around in the end, head down the underside of the crest towards the head, and leave the
crest back in the skull. At times it has been restored with a skin-sail between the
crest and neck, although that seems to have fallen out of favor.
The taxonomy of Parasaurolophus are unusually convoluted for a genus with only three species; suffice it to say that there appears to have been separate northern and southern populations. The crest of P. tubicen is more complicated than that of the type, while P. cyrtocristatus' is small, suggesting a juvenile or female (if females had smaller crests than males).
On a lighter note: there are at least two distinct pronunciations circulating. The minority (including me), at least among professionals, say: pare-ah-ser-RAUH-loh-fus, while the majority say par-ah-saur-ah-LOH-fus.
|P. tubicen Wiman, 1931 (including P. cyrtocristatus Ostrom, 1961)||late middle-?middle late Campanian (LK) of New Mexico and ?Utah|
Corythosaurini: These animals have amazingly convoluted taxonomies, due to the fact that in the earlier days of dinosaur paleontology each skull that was a little different from a type specimen was given a new species name, when it probably was just a variant due to age, gender, or preservation. In older works, you may see these animals referred to as the "hooded duckbills." You may also see reference to the "cheneosaurs," based on the genera Cheneosaurus and Procheneosaurus, which were thought to represent small crested adult hadrosaurids, but actually were the juveniles of various corythosaurins.
|Taxon or Taxa:||Time/Place:||Comments:|
|Magnapaulia laticaudus Prieto-Márquez, Chiappe, and Joshi, 2012 (originally Lambeosaurus laticaudus Morris, 1981)||Campanian (LK) of Mexico||For much of its history before about 2010 or so, this taxon was known as an obscure, tall-spined lambeosaurine of generous proportions (Morris suggested that it could be over 50 feet long and 20 tons, based on referred material, but it was probably closer to 40 feet and not nearly so ample). The original generic assignment was tentative, which wasn't helped by the absence of the crest.|
|Velafrons coahuilensis Gates, Sampson, Delgado de Jesús, Zanno, Eberth, Hernandez-Rivera, Aguillón Martínez, and Kirkland, 2007||late Campanian (LK) of Mexico||Velafrons is based on a mostly complete juvenile skull with one of those crests that looks like a little dome leaning over the eyes, just about to extend backward on the skull. My first question was how does it relate to ?Lambeosaurus [now Magnapualia] laticaudus; they are not the same thing, based on the form of the premaxilla. They do share one thing striking, though; ?L. laticaudus was immense, and the type individual of Velafrons was large for a lambeosaurine of its growth stage, suggesting it too was a big lambeosaurine. This is not confined to one branch of Hadrosauridae; Kritosaurus sp. from Mexico is also significantly larger than its cousins elsewhere.|
|Lambeosaurus: Parks, 1923||L. lambei (type) Parks, 1923||early late Campanian (LK) of Alberta||L. lambei is recognized from its crest, which is hatchet shape up front over the beak and has a short solid spine going back over the rear of the skull. A contemporary of Corythosaurus, it is also known from remains belonging to over twenty individuals. Like several other hadrosaurids endowed with spine-like projections, it has been suggested that a skin sail was attached to the spine.|
|L. magnicristatus Sternberg, 1935||early late Campanian (LK) of Alberta||A much rarer species, L. magnicristatus has a large, rounded and greatly expanded hatchet crest, with much less of a spine at the rear.|
|Corythosaurus casuarius Brown, 1914||late middle-early late Campanian (LK) of Alberta||One of the best-known hadrosaurids, with remains including skin impressions for most of the body, Corythosaurus is most famous for its helmet or half dinner plate-like crest. It is known from remains belonging to at least twenty individuals, and is a characteristic Judithian dinosaur. Perhaps not surprisingly, certain individuals (not the biggest, presumably adults, but still good-sized) have crests which provide Hypacrosaurus foreshadowing with the shallower angle at the transition between the beak and the main part of the skull, and a small pointed process at the caudal end (this actually can be seen in some of the largest individuals, but it's not near as prominent as in Hypacrosaurus). Although sexual dimorphism has been a standard explanation for skull variation in adults, better stratigraphic data suggests time-successive species (as yet not formally defined). C. intermedius is apparently now valid again based on stratigraphic grounds, but it's one of those unpublished "open secrets".|
|"Hypacrosaurus" stebingeri Horner and Currie, 1994||early late Campanian (LK) of Montana and Alberta||This taxon is considered by its describers to be transitional between the other lambeosaurines and Hypacrosaurus, although it may not belong to Hypacrosaurus. I'm taking it out to be on the safe side, because it tends to sort outside of a monophyletic relationship with the type species. It is known from remains including juveniles and eggs.|
|Hypacrosaurus altispinus Brown, 1913||middle Maastrichtian (LK) of Alberta||A characteristic Edmontonian dinosaur, H. altispinus has a crest that resembles a shorter and more triangular Corythosaurus crest, with a short spine jutting back in the rear. It also has very tall neural spines, giving it a slight fin-back. Remains from between five and ten individuals have been found.|
|Olorotitan arharensis Godefroit, Bolotsky, and Alifanov, 2003||late? Maastrichtian (LK) of Russia||Based on a partial skeleton of a hadrosaur possibly 12 meters long, I originally thought this animal was going to turn out to be a saurolophine (by allusion to Anatotitan [Edmontosaurus]), but it's a lambeosaurine. It has a tall corythosaurin-type crest, but pushed back on the skull and given a fan-like expansion; by comparison to Lambeosaurus, it has its "hatchet" on backwards.|
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