Limits...
Supplementary cranial description of the types of Edmontosaurus regalis (Ornithischia: Hadrosauridae), with comments on the phylogenetics and biogeography of Hadrosaurinae

View Article: PubMed Central - PubMed

ABSTRACT

The cranial anatomy of the flat-skulled hadrosaurine Edmontosaurus regalis (Ornithischia: Hadrosauridae) is extensively described here, based on the holotype and paratype collected from the middle part of the Horseshoe Canyon Formation in southern Alberta. Focus is given to previously undocumented features of ontogenetic and phylogenetic importance. This description facilitates overall osteological comparisons between E. regalis and other hadrosaurids (especially E. annectens), and revises the diagnosis of E. regalis, to which a new autapomorphy (the dorsal half of the jugal anterior process bearing a sharp posterolateral projection into the orbit) is added. We consider the recently named Ugrunaaluk kuukpikensis from the upper Campanian/lower Maastrichtian of Alaska a nomen dubium, and conservatively regard the Alaskan material as belonging to Edmontosaurus sp.. A phylogenetic analysis of Hadrosauroidea using maximum parsimony further corroborates the sister-taxon relationship between E. regalis and E. annectens. In the strict consensus tree, Hadrosaurus foulkii occurs firmly within the clade comprising all non-lambeosaurine hadrosaurids, supporting the taxonomic scheme that divides Hadrosauridae into Hadrosaurinae and Lambeosaurinae. Within Edmontosaurini, Kerberosaurus is posited as the sister taxon to the clade of Shantungosaurus + Edmontosaurus. The biogeographic reconstruction of Hadrosaurinae in light of the time-calibrated cladogram and probability calculation of ancestral areas for all internal nodes reveals a significantly high probability for the North American origin of the clade. However, the Laramidia–Appalachia dispersals around the Santonian–Campanian boundary, inferred from the biogeographic scenario for the North American origin of Hadrosaurinae, are in conflict with currently accepted paleogeographic models. By contrast, the Asian origin of Hadrosaurinae with its relatively low probability resulting from the biogeographic analysis is worth seriously considering, despite the lack of fossil material from the Santonian and lower Campanian of Asia. Extra fossil collecting in appropriate geographic locations and stratigraphic intervals of Asia and Europe will help to clarify the biogeographic dynamics of hadrosaurine dinosaurs in the near future.

No MeSH data available.


Related in: MedlinePlus

Time-calibrated cladogram of Hadrosaurinae derived from the strict consensus tree shown in Fig 20, with probability estimation of ancestral continental regions for all nodes of the taxon.Blue stars indicate hadrosaurine species recovered from Appalachia, eastern North America.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5383305&req=5

pone.0175253.g021: Time-calibrated cladogram of Hadrosaurinae derived from the strict consensus tree shown in Fig 20, with probability estimation of ancestral continental regions for all nodes of the taxon.Blue stars indicate hadrosaurine species recovered from Appalachia, eastern North America.

Mentions: Since the 1980s, issues concerning the ancestral areas and dispersal dynamics of hadrosaurines during the latter half of the Late Cretaceous continue to be hotly debated [1, 2, 10, 30, 53–55]. Here, our temporally calibrated cladogram with probability calculation of ancestral areas provides some new insights into the biogeography of Hadrosaurinae (Fig 21). The results of our biogeographic analysis suggest the following information: Hadrosaurinae (node 1) has a considerably high probability (~81%) of having originated in North America; the first split of Hadrosaurinae is inferred to have occurred no later than the end of Santonian; Edmontosaurini (node 12) may originate in Asia, with a relatively high probability of 75%; during the latest Santonian–earliest Maastrichtian, multiple dispersals between Asia and western North America (i.e. Laramidia) would happen presumably via the Bering land bridge; the probabilities of the North and South American origins for Kritosaurini (node 6) are 75% and 25%, respectively (Fig 21).


Supplementary cranial description of the types of Edmontosaurus regalis (Ornithischia: Hadrosauridae), with comments on the phylogenetics and biogeography of Hadrosaurinae
Time-calibrated cladogram of Hadrosaurinae derived from the strict consensus tree shown in Fig 20, with probability estimation of ancestral continental regions for all nodes of the taxon.Blue stars indicate hadrosaurine species recovered from Appalachia, eastern North America.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383305&req=5

pone.0175253.g021: Time-calibrated cladogram of Hadrosaurinae derived from the strict consensus tree shown in Fig 20, with probability estimation of ancestral continental regions for all nodes of the taxon.Blue stars indicate hadrosaurine species recovered from Appalachia, eastern North America.
Mentions: Since the 1980s, issues concerning the ancestral areas and dispersal dynamics of hadrosaurines during the latter half of the Late Cretaceous continue to be hotly debated [1, 2, 10, 30, 53–55]. Here, our temporally calibrated cladogram with probability calculation of ancestral areas provides some new insights into the biogeography of Hadrosaurinae (Fig 21). The results of our biogeographic analysis suggest the following information: Hadrosaurinae (node 1) has a considerably high probability (~81%) of having originated in North America; the first split of Hadrosaurinae is inferred to have occurred no later than the end of Santonian; Edmontosaurini (node 12) may originate in Asia, with a relatively high probability of 75%; during the latest Santonian–earliest Maastrichtian, multiple dispersals between Asia and western North America (i.e. Laramidia) would happen presumably via the Bering land bridge; the probabilities of the North and South American origins for Kritosaurini (node 6) are 75% and 25%, respectively (Fig 21).

View Article: PubMed Central - PubMed

ABSTRACT

The cranial anatomy of the flat-skulled hadrosaurine Edmontosaurus regalis (Ornithischia: Hadrosauridae) is extensively described here, based on the holotype and paratype collected from the middle part of the Horseshoe Canyon Formation in southern Alberta. Focus is given to previously undocumented features of ontogenetic and phylogenetic importance. This description facilitates overall osteological comparisons between E. regalis and other hadrosaurids (especially E. annectens), and revises the diagnosis of E. regalis, to which a new autapomorphy (the dorsal half of the jugal anterior process bearing a sharp posterolateral projection into the orbit) is added. We consider the recently named Ugrunaaluk kuukpikensis from the upper Campanian/lower Maastrichtian of Alaska a nomen dubium, and conservatively regard the Alaskan material as belonging to Edmontosaurus sp.. A phylogenetic analysis of Hadrosauroidea using maximum parsimony further corroborates the sister-taxon relationship between E. regalis and E. annectens. In the strict consensus tree, Hadrosaurus foulkii occurs firmly within the clade comprising all non-lambeosaurine hadrosaurids, supporting the taxonomic scheme that divides Hadrosauridae into Hadrosaurinae and Lambeosaurinae. Within Edmontosaurini, Kerberosaurus is posited as the sister taxon to the clade of Shantungosaurus + Edmontosaurus. The biogeographic reconstruction of Hadrosaurinae in light of the time-calibrated cladogram and probability calculation of ancestral areas for all internal nodes reveals a significantly high probability for the North American origin of the clade. However, the Laramidia–Appalachia dispersals around the Santonian–Campanian boundary, inferred from the biogeographic scenario for the North American origin of Hadrosaurinae, are in conflict with currently accepted paleogeographic models. By contrast, the Asian origin of Hadrosaurinae with its relatively low probability resulting from the biogeographic analysis is worth seriously considering, despite the lack of fossil material from the Santonian and lower Campanian of Asia. Extra fossil collecting in appropriate geographic locations and stratigraphic intervals of Asia and Europe will help to clarify the biogeographic dynamics of hadrosaurine dinosaurs in the near future.

No MeSH data available.


Related in: MedlinePlus