Abstract
BackgroundEolambia caroljonesa is the most abundant dinosaur in the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation of Utah, and one of the most completely known non-hadrosaurid iguanodontians from North America. In addition to the large holotype and paratype partial skulls, copious remains of skeletally immature individuals, including three bonebeds, have been referred to E. caroljonesa. Nevertheless, aspects of the postcranial anatomy of this taxon, particularly the pelvic girdle, have remained ambiguous due to the lack of associated postcranial material of larger, more mature individuals.Methodology/Principal findingsHere we describe a recently discovered associated partial postcranial skeleton of a large Eolambia caroljonesa. This specimen, FMNH PR 3847, provides new anatomical data regarding the vertebral column and pelvic girdle, supplementing previous diagnoses and descriptions of E. caroljonesa. A new phylogenetic analysis incorporating information from FMNH PR 3847 places E. caroljonesa as a basal hadrosauromorph closely related to Protohadros byrdi from the Cenomanian Woodbine Formation of Texas. Histological analysis of FMNH PR 3847 reveals that it represents a subadult individual eight to nine years of age. Taphonomic analysis indicates that FMNH PR 3847 was preserved in a crevasse splay deposit, along with an unusual abundance of small crocodylomorph material.Conclusions/SignificanceFMNH PR 3847 provides a wealth of new morphological data, adding to the anatomical and systematic characterization of Eolambia caroljonesa, and histological data, revealing new information on growth history in a basal hadrosauromorph. Taphonomic characterization of FMNH PR 3847 and associated vertebrate material will allow comparison with other vertebrate localities in the Mussentuchit Member of the Cedar Mountain Formation.
Highlights
The early Late Cretaceous (Cenomanian–Santonian [1]) was a poorly understood interval in iguanodontian dinosaur evolution
Eolambia caroljonesa is the most abundant dinosaur in the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation of Utah, and one of the most completely known non-hadrosaurid iguanodontians from North America
Eolambia is by far the most completely known, with two large partial skulls and extensive juvenile material, with nearly every skeletal element represented by multiple examples in the College of Eastern Utah Prehistoric Museum (CEUM), Sam Noble Oklahoma Museum of Natural History (OMNH) [18,20], and Field Museum of Natural History (FMNH) collections
Summary
The early Late Cretaceous (Cenomanian–Santonian [1]) was a poorly understood interval in iguanodontian dinosaur evolution This was due to the scarcity of fossils with wellconstrained ages that postdate the rich Early Cretaceous basal iguanodont record [2,3,4,5,6] and predate the extensive hadrosaurid record from the latter half of the Late Cretaceous (Campanian–Maastrichtian [7,8]). Eolambia caroljonesa is the most abundant dinosaur in the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation of Utah, and one of the most completely known non-hadrosaurid iguanodontians from North America. Aspects of the postcranial anatomy of this taxon, the pelvic girdle, have remained ambiguous due to the lack of associated postcranial material of larger, more mature individuals
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