| Lambeosaurines | |
|---|---|
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| Skeleton FMNH P-27393 ofParasaurolophus cyrtocristatus,Field Museum of Natural History | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Ornithopoda |
| Family: | †Hadrosauridae |
| Clade: | †Euhadrosauria |
| Subfamily: | †Lambeosaurinae Parks,1923[1] |
| Subgroups | |
| Synonyms | |
Lambeosaurinae/ˌlæmbiəˈsɔːraɪniː/ (meaning 'lambe's lizards') is an extinct group of crestedhadrosauriddinosaurs.
Uncertainty surrounds the size of lambeosaurs from the European continent. Hadrosaurs found there, alongside other dinosaurs, have traditionally been considered representatives of the phenomenon ofinsular dwarfism, as the continent was then made up of many smaller islands. Many fossil remains from the continent are smaller than those of hadrosaurs found elsewhere in the world, with only isolated remains indicating individuals of adult size by the standards of their relatives inNorth America andAsia. It remains possible, however, that at least some cases instead represent misidentification of juvenile remains.[8][9] The presence of genuine dwarfed taxa has been validated in some cases;[8][10] adults of the genusMinqaria, for example, are thought to be around 3.5 metres (11 ft) in length.[11] Contrastingly, the genusPararhabdodon has a projected adult size similar to those of hadrosaurs on other continents, and known remains ofAdynomosaurus and hadrosaurs from theBasturs Poble bonebed are of this adult size themselves.[12] Why hadrosaurs of such variable sizes co-exist, despite being subject to the same environmental pressures, remains unclear.[10]
The first material ofhadrosaurids were found in the 1850s and named by American paleontologistJoseph Leidy:Trachodon mirabilis fromMontana andThespesius occidentalis fromSouth Dakota in 1856, andHadrosaurus foulkii fromNew Jersey in 1859. Numerous additional genera and species were described throughout the following decades, with the first discoveries inAlberta in the late 1890s and early 1900s by Canadian paleontologistLawrence M. Lambe being ascribed toTrachodon under the subgenusPteropelyx.[5] The first hadrosaur to preserve a crest on the skull wasSaurolophus named in 1912 by American paleontologistBarnum Brown for a skeleton from Alberta.[13] It was toSaurolophus that Lambe found the greatest similarities for new specimens described from Alberta in 1914, which preserved a prominent crest on top of the skull. These remains he assigned toStephanosaurus, a new genus name forTrachodon marginatus he had named earlier for material from the 1900s expeditions. While the crest ofSaurolophus projected backwards, that of the material assigned toStephanosaurus projected upwards above the eye.[14] Brown followed up in 1914 with the description of some nearly complete skeletons from Alberta that he namedCorythosaurus casuarius, which showed a tall and rounded crest atop the skull, and with him questioning the generic status ofStephanosaurus. AsStephanosaurus marginatus was named for incomplete material from the skeleton, Brown did not find the referral of the crested skulls to the taxon justifiable, suggesting they could belong to the genusCorythosaurus but as a distinct species. Brown also separatedTrachodontidae into two subfamilies for the first time, uniting the taxa with crested skulls intoSaurolophinae while other genera were contained withinTrachodontinae.[15]
Lambe subsequently revised the classification of Hadrosauridae (the older name for Trachodontidae) in 1920 following the description of the new generaCheneosaurus,Edmontosaurus, andProsaurolophus and the discovery of a new skull he referred toStephanosaurus in the interim, identifying that the crests ofSaurolophus andProsaurolophus were formed of different bones than the other crested genera and as a result separatingCorythosaurus,Cheneosaurus,Hypacrosaurus andStephanosaurus (including the crested skulls) into the new subfamily Stephanosaurinae.[6] In 1923 the crested skulls were again removed fromStephanosaurus, this time by Canadian paleontologistWilliam A. Parks, who established the new taxonLambeosaurus lambei for them in honor of Lambe who had first described them. AsStephanosaurus could no longer be shown to be a crested hadrosaur, Parks also named the subfamily Lambeosaurinae to replace Stephanosaurinae for the group.[1] This separation was further supported by American paleontologistCharles W. Gilmore the next year, who found thatStephanosaurus could be better referred to the genusKritosaurus and was a member ofHadrosaurinae rather than Lambeosaurinae. Gilmore could not identify which subfamilyTrachodon should belong in due to its very limited material, so he supported the separation of Hadrosauridae into Hadrosaurinae (rather than Trachodontinae), Saurolophinae, and Lambeosaurinae, the latter of which now also includedParasaurolophus.[16]
American paleontologistsRichard Swann Lull and Nelda E. Wright published areview article of Hadrosauridae in 1942 where they supported the subfamilies of Gilmore with the addition of Cheneosaurinae, which they named for small-bodied crested generaCheneosaurus andProcheneosaurus. Cheneosaurins had small rounded crests while lambeosaurines possessed more elaborate crests of different forms between the genera.[5] Both Lambeosaurinae and Cheneosaurinae were elevated to family rank as Lambeosauridae and Cheneosauridae by German paleontologistFriedrich von Huene in 1948 and 1956 respectively.[17][18] However, American paleontologistCharles Mortram Sternberg in 1953 recognized that the divisions of previous studies were not useful, separating genera based on an arbitrary decision of feature significance, especially the separation of Cheneosaurinae from Lambeosaurinae. As a result, he condensed Hadrosauridae into only two subfamilies: Hadrosaurinae and Lambeosaurinae, with saurolophines being members of Hadrosaurinae, and cheneosaurines being members of Lambeosaurinae. Within Lambeosaurinae he includedLambeosaurus,Corythosaurus,Hypacrosaurus,Parasaurolophus,Cheneosaurus,Tetragonosaurus, andTrachodon; a classification he reiterated in 1954.[19][20]
Work by American paleontologistPeter Dodson in 1975 revised the taxonomy of Lambeosaurinae by recognizing thatCheneosaurus andProcheneosaurus were not distinct genera but rather juveniles of other taxa that were not old enough to have fully-developed crests. The species ofProcheneosaurus were identified as synonyms of eitherLambeosaurus orCorythosaurus, whileCheneosaurus was identified as a juvenile ofHypacrosaurus.[21] Following the recognition of cheneosaurs as juveniles ofLambeosaurus,Corythosaurus, andHypacrosaurus, American palaeontologistMichael K. Brett-Surman published a phylogeny of all accepted genera of Hadrosauridae in 1979, and expanded Lambeosaurinae to also includeTsintaosaurus, withJaxartosaurus andBactrosaurus as early members, andLambeosaurus,Corythosaurus andHypacrosaurus as one another's closest relatives.[22] A 1990 review of hadrosaurs by American paleontologistsDavid B. Weishampel andJohn R. Horner was unable to conclude ifTsintaosaurus was a lambeosaurine or hadrosaurine, but added the Asian generaBarsboldia andNipponosaurus to Lambeosaurinae.[23] The content of Lambeosaurinae expanded over the next decades before the second review by Horner in 2004. During this period, the Asian generaAmurosaurus,Charonosaurus, andOlorotitan were named and added to Lambeosaurinae, and the status ofTsintaosaurus as a lambeosaurine was solidified.[24]
Lambeosaurines have been traditionally split into the tribes or cladesParasaurolophini (Parasaurolophus,Charonosaurus, others (?).) andLambeosaurini (Corythosaurus,Hypacrosaurus,Lambeosaurus, others.).[25] Corythosaurini (synonym of Lambeosaurini, see below) and Parasaurolophini as terms entered the formal literature in Evans and Reisz's 2007 redescription ofLambeosaurus magnicristatus. Corythosaurini was defined as alltaxa more closely related toCorythosaurus casuarius than toParasaurolophus walkeri, and Parasaurolophini as all those taxa closer toP. walkeri than toC. casuarius. In this study,Charonosaurus andParasaurolophus are parasaurolophins, andCorythosaurus,Hypacrosaurus,Lambeosaurus,Nipponosaurus, andOlorotitan are corythosaurins.[26] However, later researchers pointed out that due to the rules of priority set forth by theICZN, Any tribe containingLambeosaurus is properly namedLambeosaurini, and that therefore the name "Corythosaurini" is a junior synonym, and the definition hadCorythosaurus casuarius changed toLambeosaurus lambei, and the same for Parasaurolophini.[27] In more recent yearsTsintaosaurini (Tsintaosaurus +Pararhabdodon) andAralosaurini (Aralosaurus +Canardia) have also emerged.[28]
A 2013 study describing the genusCanardia found it to form a grouping withAralosaurus, therein named as Aralosaurini and defined as the most exclusive clade of hadrosaurs containing bothCanardia andAralosaurus.[3] Though one 2022 study recovered the tribe asmonophyletic,[29] most modern analyses fail to recover a natural grouping between the two genera.[30][31][32] Daniel Madzia and colleagues registered the name underPhylocode in a 2021 study and redefined it as "the largest clade containingAralosaurus tuberiferus andCanardia garonnensis but notLambeosaurus lambei,Parasaurolophus walkeri, andTsintaosaurus spinorhinus".[4]
Numerous members of the clade Lambeosaurinae are known from Europe, dating to the end of theCretaceous period.[3] These various namedtaxa have traditionally been found to group into numerous different lambeosaur lineages, includingAralosaurini,Tsintaosaurini,Lambeosaurini,[3][31] andParasaurolophini.[33] However, a study by Nick Longrich and colleagues proposed European lambeosaurs to form a singularmonophyletic group, therein named Arenysaurini, based upon a phylogenetic analysis incorporating data based on geographic origin. They phylogenetically defined the tribe as all hadrosaurids closer toArenysaurus ardevoli thanTsintaosaurus spinorhinus,Parasaurolophus walkeri, orLambeosaurus lambei. In addition to the various named genera, indeterminate remains from across the continent including theBasturs Poble bonebed were proposed to represent arenysaurs.[31]
The existence of a tsintaosaur clade of lambeosaurines was first recognized by palaeontologists Albert Prieto-Márquez and Johnathan R. Wagner, who in 2009 published a paper recognizing aphylogenetic relationship betweenTsintaosaurus andPararhabdodon based both on shared anatomical traits and aphylogenetic analysis.[34] A 2013 study by Prieto-Márquez corroborated the existence of this grouping, and coined thetribe Tsintaosaurini to refer to it. Thetype genus isTsintaosaurus, and it was defined as the smallestclade containingTsintaosaurus spinorhinus andPararhabdodon isonensis.[3] Several studies since have corroborated the existence of the clade,[4][35][36] though some others have failed to recover it, instead finding the two genera in apolytomy of basal lambeosaurs.[4][37][30] A 2021 paper by Daniel Madzia and other ornithischian researchers, focused on a revising ornithischian nomenclature and converting existing group names intoPhylocode-compliant clades, re-formalized the coining of Tsintaosaurini and revised its definition to be the most inclusive group includingT. spinorhinus andP. isonensis, but notAralosaurus tuberiferus,Lambeosaurus lambei, orParasaurolophus walkeri.[4] Longrich and colleagues instead consider the two genera unrelated, withPararhabdodon being part of Arenysaurini.[31]
The term Corythosaurini was first used by Brett-Surman in 1989, who characterized the taxon via reference to the premaxilary expansion into a hollow helmet-like cranial crest, as well as higher neural spines.[38] The clade was formally defined via phylogenetic analysis by Evans and Reisz in 2007,[39] and this was confirmed by multiple other analyses.[40] In 2011, Sullivan et al. observed that by therules of priority set by theInternational Code of Zoological Nomenclature, the name of the tribe ought to be Lambeosaurini due to its containing the defining type genus (Lambeosaurus) of its superior taxon (Lambeosaurinae).[41] It is defined as all lambeosaurines closer toLambeosaurus lambei than toParasaurolophus walkeri,Tsintaosaurus spinorhinus, orAralosaurus tuberiferus.[4]
The followingcladogram was recovered in a 2022 phylogenetic analysis by Xing Hai, and colleagues.[29]
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Lambeosaurines originated on the continent ofLaurasia during theLate Cretaceous, being initially found throughout modern Europe and Asia. Around theCampanian stage, lambeosaurines of the tribeCorythosauria colonized the landmass ofLaramidia (modern western North America) viaBeringia and spread as far south as Mexico, radiating into a diverse array of a body plans, including famous taxa such asParasaurolophus andLambeosaurus. They appear to have also colonized the eastern landmass ofAppalachia at some point, based on indeterminate lambeosaurine remains from the late Campanian/Maastrichtian-agedKanguk Formation of Nunavut.[42][43]
For unknown reasons, lambeosaurines largely disappeared from North America around the Campanian/Maastrichtian boundary (the last remaining confirmed American member beingHypacrosaurus), but continued their dominance in Laurasia up to the end of the Cretaceous, with some members such asAjnabia andMinqaria even colonizing northern Africa from Europe. However, fragmentary remains, including a partial humerus, resembling those of lambeosaurines have been reported from the late Maastrichtian-agedNew Egypt Formation ofNew Jersey, USA. If these are lambeosaurine remains, these specimens are unique both for representing the one of the very few records of lambeosaurines from the landmass of Appalachia (suggesting that lambeosaurines had managed to migrate eastwards to Appalachia during the Maastrichtian, following the partial closure of theWestern Interior Seaway), and potentially representing one of the latest records of the group from North America.[42][43]
