Abstract
Background Eolambia caroljonesa is known from copious remains from the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation in eastern Utah; however, the taxon has been only briefly described. Thus, we present herein a complete osteological description of Eolambia.Methodology/Principal FindingsThe description of Eolambia presented here is based upon the holotype partial skeleton (CEUM 9758), paratype partial skull (CEUM 5212), and abundant disarticulated elements from two bonebeds that contain juvenile individuals. These remains allow the skeletal anatomy of Eolambia to be documented almost fully and a revised diagnosis to be proposed.Conclusions/SignificanceThe description provided here facilitates comparisons between Eolambia and other iguanodontians and allows Eolambia to be coded for additional characters in phylogenetic analyses. The close affinity between Eolambia and Probactrosaurus gobiensis from the Early Cretaceous of China supports previous hypotheses of faunal interchange between Asia and North America in the early Late Cretaceous.
Highlights
The fossil record of non-hadrosaurid members of Iguanodontia, i.e. basal iguanodonts, from North America has grown dramatically in recent years and rivals those of Europe and eastern Asia
Three basal iguanodonts are known from the early Late Cretaceous of North America: Eolambia from the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation [8,9], Protohadros from the middle Cenomanian Woodbine Formation [10], and Jeyawati from the middle Turonian Moreno Hill Formation [11]
Two of the six characters that comprise the unique combination of features diagnostic of Eolambia caroljonesa can be observed only in juvenile specimens
Summary
The fossil record of non-hadrosaurid members of Iguanodontia, i.e. basal iguanodonts, from North America has grown dramatically in recent years and rivals those of Europe and eastern Asia. Both processes project caudodorsally in lateral and medial views and are roughly parallel (Fig. 7C, D), forming the dorsal and ventral rims of the external naris.
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