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Journal of Vertebrate Paleontology 21(2):392–396, June 2001 q 2001 by the Society of Vertebrate Paleontology


A REANALYSIS OF THE PHYLOGENETIC POSITION OF EOLAMBIA CAROLJONESA (DINOSAURIA, IGUANODONTIA) JASON J. HEAD, Department of Geological Sciences and Shuler Museum of Paleontology, Southern Methodist University, Dallas, Texas 75275-0395

Eolambia caroljonesa was described as a basal, crestless lambeosaurine hadrosaurid on the basis of multiple disarticulated skeletons from the uppermost Cedar Mountain Formation (Albian–Cenomanian boundary, 98.39 6 0.07 Ma) of eastern Utah (Cifelli et al., 1997; Kirkland, 1998). The occurrence of a lambeosaurine at the Early–Late Cretaceous transition is significant as it indicates Early Cretaceous origins of both Hadrosauridae and other derived iguanodontians (e.g., Bactrosaurus, Telmatosaurus, Protohadros), for which there is no additional evidence (Weishampel et al., 1993; Godefroit et al., 1998; Head, 1998). The purpose of this analysis is to test the proposed phylogenetic status of Eolambia within derived iguanodontians (Iguanodon and all more derived taxa), based on reinterpretation of the character states of the taxon as well as description of additional remains. The hypodigm of Eolambia consists of specimens that are housed in the College of Eastern Utah Museum (CEUM), Price (holotype and paratype), and the Oklahoma Museum of Natural History (OMNH), Norman (paratype). CEUM specimens consist of two disarticulated, partial skeletons from two localities (Kirkland, 1998). This study emphasizes OMNH specimens in phylogenetic analysis however, because: (1) the majority of lambeosaurine synapomorphies reported for Eolambia are based on these specimens; (2) OMNH materials represent a greater proportion of the skeleton, including the skull, than reported CEUM specimens; and (3) only OMNH Eolambia localities have been geographically and stratigraphically correlated with each other and a radiometric datum in the literature (Cifelli et al., 1999). Oklahoma Museum specimens represent at least six individuals from five localities. The majority of elements in this analysis are from OMNH v824 (possibly a single individual) and OMNH v237, a locality including at least two individuals as indicated by two different scapular lengths (OMNH 4219 5 26 cm complete: OMNH 4221 5 33 cm incomplete). A right surangular (OMNH 4218) is described from OMNH v237 (not OMNH v824 Kirkland, 1998:287), and a sacrum (OMNH 27749) from OMNH v696 (Kirkland, 1998; Cifelli et al., 1999) is also incorporated in this study. DESCRIPTION Diagnostic cranial elements of Eolambia include a right premaxilla, right surangular, and basisphenoid. The majority of lambeosaurine cranial synapomorphies were reported from the premaxilla, but the surangular and basisphenoid have not been previously described. The premaxilla (OMNH 28919) possesses prominent premaxillary foramina that communicate through the dorsal, ventral, and anteromedial surfaces of the element. Ventrally, (Fig. 1B) two foramina are located toward the oral margin of the premaxilla, more anteriorly positioned than in other iguanodontians. A small channel extends between these foramina and the interpremaxillary articular surface. The foramina exit the premaxilla dorsally as an elongate fissure and secondary channel, posterior to the base of the ascending process. Dorsally, (Fig. 1A) a shallow embayment is present on the lateral surface of the premaxillary ascending process, dorsal to the narial foramen. The embayment receives an anterior projection of the nasals in other iguanodontians (Norman, 1986; Horner, 1992), indicating that the nasals formed the dorsolateral margins of the external nares in Eolambia. Medially (Fig. 1C), a longitudinal groove is present on the ventral and medial surfaces of the premaxilla, posterior to the beak. In ventral view, the groove is deep and antero-

medially angled. The groove receives a portion of the maxillary rostrodorsal process in other derived iguanodontians (e.g., Horner, 1992). The surangular (OMNH 04218) is elongate, with a strongly inflected retroarticular process in lateral view (Fig. 1E). A prominent surangular foramen is present at the base of the mandibular glenoid, and a smaller accessory foramen occurs anterodorsal to the surangular foramen. In dorsal view (Fig. 1D) the glenoid shelf is transversely expanded with an upturned lateral margin. The medial margin of the shelf is not preserved. In ventral view (Fig. 1F), the articular surface for the angular consists of a highly interdigitated, medially expanded shelf. The orientation of the articular surface for the angular (Fig. 1E, F) indicates that the angular was positioned ventrally as in Protohadros and more basal iguanodontians (Weishampel et al., 1993; Head, 1998). The basisphenoid (OMNH 28920) is nearly complete, missing only the left basipterygoid process. In ventral view, it is roughly triangular with a prominent, anteriorly projected parasphenoid process (Fig. 1G). Posteriorly, the contributions of the basisphenoid to the basal tuberae consist of widely spaced and ventrally deflected hemispherical processes whose posteroventral margins compose the articular surfaces for the basioccipital. In lateral view (Fig. 1H), the basipterygoid processes descend from the long axis of the element at an angle of approximately 328. This is a shallower angle than seen in lambeosaurines and most hadrosaurines (Weishampel and Horner, 1990). The vidian canal is present along the lateral surface of the basisphenoid, extending from just anterodorsal to the divergence of the basipterygoid processes to incomplete dorsal margin of the element. Diagnostic postcranial elements include a right ilium and incomplete right femur. The ilium of Eolambia (OMNH 04213) is dorsoventrally shallow in lateral view (Fig. 2B), with an elongate, ventrally deflected prepubic process. The dorsal margin is expanded and rugose. It is laterally reflected from the posterior extent of the prepubic process to the posterior margin of the element (Fig. 2B, C) for the attachment for the hindlimb adductor musculature, as in other iguanodontians (e.g., Norman, 1986). Ventrally, the pubic peduncle is elongate and anteriorly angled. The acetabulum is extremely large for the size of the ilium, larger than the condition reported for any ontogenetic stage in other iguanodontians (e.g., ‘‘Vectisaurus’’ Norman, 1990; Hypacrosaurus Horner and Currie, 1994). The ischiatic peduncle is similar to ‘‘hadrosauroid’’ (sensu Godefroit et al., 1998) grade iguanodontians, in that it is more poorly defined than seen in Iguanodon, Ouranosaurus, or Altirhinus (Taquet, 1976; Norman, 1986, 1998). The peduncle appears to extend to the posterior margin of the ilium. The ilium of Eolambia is unique in lacking a distinct postpubic (5postacetabular) region behind the ischiatic peduncle. In Camptosaurus, Iguanodon, Ouranosaurus, and Altirhinus, the postpubic region is continuous with the main body of the ilium, with an anteroventrally angled posterior margin. In more derived taxa (Gilmoreosaurus, Bactrosaurus, Hadrosaurinae, Lambeosaurinae), the postpubic region consists of a distinct, separate process that is free of the reflected dorsal margin of the ilium. The femur of Eolambia (OMNH 04202) is represented by a specimen that lacks the proximal extremity. Distally, the condyles are not as anteroposteriorly expanded as seen in other derived iguanodontians (e.g., Bactrosaurus, Gilmoreosaurus, Telmatosaurus, Hadrosaurinae, Lambeosaurinae), and are separated by a wide anterior intercondylar groove




FIGURE 1. Eolambia caroljonesa (paratype), cranial elements. Right premaxilla (OMNH 28919) in (A) lateral, (B) ventral, and (C) medial views; right surangular (OMNH 4218) in (D) dorsal, (E) lateral, and (F) ventral views; basisphenoid (OMNH 28920) in (G), ventral and (H), right lateral views. Abbreviations: mag, groove for articulation with maxillary rostrodorsal process; nas, articular surface for nasals. Scale bars equal 5 cm.

(Fig. 2A). There is no indication of enclosure or roofing of the groove between the condyles. DISCUSSION Eolambia was united with Lambeosaurinae on the basis of the following synapomorphies; absence of premaxillary foramen, ‘‘partial enrollment of the premaxilla around the external nares’’; maxillary rostral shelf (absence of paired maxillary rostral processes); tall neural spines on caudal vertebrae; and an expanded distal ischium (Kirkland, 1998). Cranial synapomorphies were based on anatomical misinterpretation: the presence of premaxillary foramina is demonstrated in OMNH 28919, as are paired maxillary rostral processes of the maxilla, indicated by the presence of the medial groove for the articulation of the maxillary rostrodorsal process. The ‘‘partial enrollment of the premaxilla around the external nares’’ is actually the dorsoventral expansion of the premaxillary caudal process to form the lateral surface of the rostrum. The two postcranial synapomorphies are phylogenetically dubious: High neural spines on caudal vertebrae occur in Ouranosaurus and Bactrosaurus, neither of which is lambeosaurine. A distally expanded ischium is present in Camptosaurus, Iguanodon, Ouranosaurus, Gilmoreosaurus, Bactrosaurus, and Lambeosaurinae. Expansion of the distal ischium has recently been recently qualified as either ‘‘club-like’’

(Iguanodon, Ouranosaurus) or consisting of an ‘‘expanded foot’’ (Lambeosaurinae) (Casanovas et al., 1999). The ‘‘expanded foot’’ is not a lambeosaurine synapomorphy, however, as the condition in Corythosaurus and Lambeosaurus (Lull and Wright, 1942) is no more extensive or ‘‘footed’’ than the condition seen in either Iguanodon or Ouranosaurus (Taquet, 1976; Norman, 1986). Loss of the distal expansion appears to be synapomorphic for Hadrosaurinae (Weishampel and Horner, 1990), with the presence of the expansion plesiomorphic for derived iguanodontians. Additional hadrosaurid cranial synapomorphies described for Eolambia, including ‘‘miniaturized’’ dentary teeth (sensu Weishampel et al., 1993) that are symmetrical around a central carina, lack secondary ridges, and are arranged in tooth files that include at least three teeth per tooth file, are not supported by OMNH materials. A complete left dentary (OMNH 28511) possesses 18 toothfiles with a single tooth still articulated. The tooth is extremely broad and asymmetrical, with a mesially displaced primary ridge and a distal secondary ridge. The height of the exposed crown is approximately 1/2 the height of the battery, indicating a maximum of two fully formed teeth per tooth file. The number of teeth per file increases ontogenetically in hadrosaurids (Horner and Currie, 1994), and as OMNH 28511 represents a sub-adult animal, it is possible that three or more teeth per file were present in adults.



FIGURE 2. Eolambia caroljonesa (paratype), postcranial elements. A, right femur (OMNH 04202) in anterior view; right ilium (OMNH 4213) in (B) lateral, and (C) ventral views. Scale bars equal 10 cm.

FIGURE 3. A, strict consensus cladogram and geographic distributions of derived iguanodontians based on analysis of characters 1–26. B, single most parsimonious cladogram of derived iguanodontians incorporating all characters. Abbreviations: Af, Africa; As, Asia; Eu, Europe; Na, North America; Sa, South America.

No hadrosaurid postcranial synapomorphies are present in Eolambia. The sacrum of Eolambia (OMNH 27749) is composed of seven fused vertebrae as opposed to eight or more in derived hadrosaurids. An ‘‘incipient’’ iliac antitrochanter was reported for Eolambia, based on an expansion on the posterolateral surface of the reflected iliac dorsal margin. This expansion is restricted toward the lateral margin of the shelf, does not extend along either the ventral margin of the shelf or onto the body of the ilium, and is less expanded than the condition in either Ouranosaurus or Altirhinus (Fig. 2B, C; Taquet, 1976; Norman, 1998). Eolambia was considered to possess a fully enclosed anterior intercondylar groove, based on an isolated femur from the Cedar Mountain Formation (Galton and Jensen, 1979); however, OMNH 04202 does not possess either an enclosed intercondylar groove or the anteroposteriorly expanded condyles seen in the specimen described in Galton and Jensen (1979). OMNH 04202 is a subadult; however, there is no indication that enclosure of the anterior intercondylar groove is ontogenetically variable. These differences are significant both in determining character states for Eolambia, and in indicating the presence of another, possible more derived, iguanodontian taxon from the Cedar Mountain Formation. The revised character states of Eolambia were incorporated into the phylogenetic analysis of derived iguanodontians of Head (1998), with seven additional characters included (Appendices 1, 2). Analysis was performed using PAUP 3.1.1 (Swofford, 1993), with Iguanodon and Ouranosaurus employed as dual outgroups (Tenontosaurus and Camptosaurus were included as outgroups in a separate analysis in an attempt to preserve the monophyletic Iguanodontidae of Norman, 1998, with no differences in tree topology). Branch and Bound analysis produced three equally parsimonious trees (TL 5 41 steps, CI 5 0.66, RI 5 0.77; Fig. 3A). Eolambia does not form a monophyletic relationship with Lambeosaurinae, and is excluded from all known definitions of Hadrosauridae in every tree. Addition of a single character, the presence of anteroposteriorly shortened supratemporal fenestrae results in monophyly of Eolambia and Probactrosaurus (TL 5 40 steps, CI 5 0.68, RI 5 0.78; Fig. 3B). Monophyly of Eolambia and Probactrosaurus must be currently considered a tentative hypothesis because Probactrosaurus is poorly known, and because the hypothesis is supported only by a single character. Eolambia is not the only iguanodontian taxon erroneously referred to as a basal lambeosaurine. Bactrosaurus was considered to represent the oldest and most primitive lambeosaurine for 65 years, prior to the recent description of a nearly complete specimen indicating that it is basal with respect to hadrosaurines and lambeosaurines (Gilmore, 1933; Godefroit et al., 1998). Pararhabdodon isonensis, from the Maastrichtian of Spain, was recently redescribed as a basal lambeosaurine on the basis of possession of a medial maxillary shelf, truncated, rounded maxillary-

NOTES jugal contact, and angular deltopectoral crest of the humerus (Casanovas et al., 1999). A truncated or rounded maxillary-jugal contact has not been demonstrated as a lambeosaurine synapomorphy (a truncated, rounded rostral jugal is considered a lambeosaurine synapomorphy by Weishampel et al., 1993, but the jugal is not known for Pararhabdodon, and the authors have not demonstrated how this character is reflected in maxillary morphology). An angular deltopectoral crest of the humerus is present primitively in iguanodontians (Norman, 1998). Additionally, the number of maxillary and dentary tooth positions (approximately 35 in each) is lower than seen in hadrosaurines or lambeosaurines (Forster, 1997), suggesting that Pararhabdodon may be basal with respect to both. The systematic relationships presented in this analysis are reinforced via congruence with the known stratigraphic distributions of included taxa (Head, 1998). Additionally, the chronological and geographic occurrence of Eolambia indicates: (1) restriction of the temporal range of Hadrosauridae to the Late Cretaceous; (2) an extended record of North American iguanodontians; and (3) a more complex biogeographic history of derived iguanodontians than previously recognized. Currently, there is no single definition of Hadrosauridae (Weishampel et al., 1993; Forster, 1997; Head, 1998). With the removal of Eolambia from Lambeosaurine, even the most inclusive definition (Head, 1998) is constrained to a maximum age of middle Cenomanian (ø95.5 Ma). Derived iguanodontians are considered to be Eurasian in origin with only limited North American occurrences prior to the Late Cretaceous (Norman, 1998). If derived iguanodontians did disperse from Asia, then the North American record represents, potentially, multiple episodes of Asian immigration during the Early to Late Cretaceous transition. The geographic distributions of Eolambia and Protohadros (Fig. 3A) suggest either: multiple events if Eolambia is basal with respect to, or the sister taxon of, Probactrosaurus; or, a single immigration event and subsequent endemicity, if Eolambia is more derived than Probactrosaurus. Conversely, the North American record may be more substantial than currently recognized. Fragmentary remains that can be differentiated from Eolambia by femoral morphology from the Cedar Mountain (uppermost Albian) and Dakota (Aptian–Cenomanian) formations (Galton and Jensen, 1979), as well as an indeterminate taxon from the Antlers Formation (Aptian–Albian) of Texas (Jacobs and Winkler, 1998) indicate an extended North American representation of derived iguanodontians during the late Early Cretaceous. This combined with discoveries of the oldest representation of lineages considered Asian in origin from North America (Chinnery et al., 1998), suggest that further analysis of North American Early Cretaceous deposits may produce radically different biogeographic hypotheses. Acknowledgments This study has benefited greatly from communications with Catherine Forster, Jack Horner, Jim Kirkland, David Norman, and David Weishampel. Rich Cifelli, Nick Czaplewski, and Randy Nydam provided access to specimens as well as cheerful encouragement. Jim Kirkland provided unpublished data and the initial opportunity to study Eolambia. Louis Jacobs and Dale Winkler critically reviewed the manuscript and made many significant contributions. LITERATURE CITED Casanovas, M. L., X. Pereda Suberbiola, J. V. Santafe, and D. B. Weishampel. 1999. First lambeosaurine hadrosaurid from Europe: palaeobiogeographical implications. Geological Magazine 136:205– 211. Chinnery, B. J., T. R. Lipka, J. I. Kirkland, J. M. Parrish, and M. K. Brett-Surman. 1998. Neoceratopsian teeth from the lower to middle Cretaceous of North America; pp. 297–302 in S. G. Lucas, J. I. Kirkland, and J. W. Estep (eds.), Lower and Middle Cretaceous Terrestrial Ecosystems. New Mexico Museum of Natural History and Science Bulletin, 14. Cifelli, R. L., J. I. Kirkland, A. Weil, A. L. Deino, and B. J. Kowallis. 1997. High-precision 40Ar/39Ar geochronology and the advent of North America’s Late Cretaceous terrestrial fauna. Proceedings of the National Academy of Sciences, USA 94:11163–11167. ———, R. L. Nydam, J. D. Gardner, A. Weil, J. G. Eaton, J. I. Kirkland, and S. K. Madsen. 1999. Medial Cretaceous vertebrates from the Cedar Mountain Formation, Emory County, Utah: the Mussentuchit local fauna; pp. 219–242 in D. D. Gillette (ed.), Vertebrate Pale-


ontology in Utah. Utah Geological Survey Miscellaneous Publication 99-1. Forster, C. M. 1997. Phylogeny of the Iguanodontia and Hadrosauridae. Journal of Vertebrate Paleontology 17(3, suppl.):47A. Galton, P. M., and J. A. Jensen. 1979. Remains of ornithopod dinosaurs from the Lower Cretaceous of North America. Brigham Young Studies in Geology 25:1–10. Gilmore, C. W. 1933. On the dinosaurian fauna of the Iren Dabasu Formation. Bulletin of the American Museum of Natural History 67:23–78. Godefroit, P., Z.-M. Dong, P. Bultynck, and L. Feng. 1998. Sino-Belgian Cooperation Program, Cretaceous dinosaurs and mammals from Inner Mongolia. 1. New Bactrosaurus (Dinosauria: Hadrosauroidea) material from Iren Dabasu (Inner Mongolia, P.R. China). Bulletin De L’ Institut Royal des Sciences Naturelles de Belgique 68:1–70. Head, J. J. 1998. A new species of basal hadrosaurid (Dinosauria, Ornithischia) from the Cenomanian of Texas. Journal of Vertebrate Paleontology 18:718–738. Horner, J. R. 1992. Cranial morphology of Prosaurolophus (Ornithischia: Hadrosauridae) with descriptions of two new hadrosaurid species and an evaluation of hadrosaurid phylogenetic relationships. Museum of the Rockies Occasional Papers 2:1–119. ———, and P. J. Currie. 1994. Embryonic and neonatal morphology and ontogeny of a new species of Hypacrosaurus (Ornithischia, Lambeosauridae) Montana and Alberta; pp. 312–336 in K. Carpenter, K. F. Hirsch, and J. R. Horner (eds.), Dinosaur Eggs and Babies. Cambridge University Press, New York. Jacobs, L. L., and D. A. Winkler. 1998. Mammals, archosaurs, and the Early to Late Cretaceous transition in North-Central Texas; pp. 253–280 in Y. Tomida, L. J. Flynn, and L. L. Jacobs (eds.), Advances in Vertebrate Paleontology and Geochronology. National Science Museum Monographs 14, Tokyo. Kirkland, J. I. 1998. A new hadrosaurid from the upper Cedar Mountain Formation (Albian-Cenomanian: Cretaceous) of eastern Utah—the oldest known hadrosaurid (lambeosaurine?); pp. 283–295 in S. G. Lucas, J. I. Kirkland, and J. W. Estep (eds.), Lower and Middle Cretaceous Terrestrial Ecosystems. New Mexico Museum of Natural History and Science Bulletin, 14. Kobayashi, Y., and Y. Azuma. 1999. Cranial material of a new iguanodontian dinosaur from the Early Cretaceous Kitadani Formation of Japan. Journal of Vertebrate Paleontology 19 (3, suppl.):57A. Lu, J. 1997. A new iguanodontidae (Probactrosaurus mazongshanensis, sp. nov.) from Mazongshan area, Gansu Province, China; pp. 27– 47 in Z. Dong (ed.), Sino-Japanese Silk Road Dinosaur Expedition. China Ocean Press, Beijing. Lull, R. S., and N. E. Wright. 1942. The hadrosaurian dinosaurs of North America. Geological Society of America Special Papers 40: 1–242. Norman, D. B. 1986. On the anatomy of Iguanodon atherfieldensis (Ornithischia: Ornithopoda). Bulletin de L’Institut Royal des Sciences Naturelles de Belgique 56:281–372. ——— 1990. A review of Vectisaurus valdensis, with comments on the Iguanodontidae; pp. 147–161 in K. Carpenter and P. J. Currie (eds.), Dinosaur Systematics: Perspectives and Approaches. Cambridge University Press, New York. ——— 1998. On Asian ornithopods (Dinosauria: Ornithischia). 3. A new species of iguanodontid dinosaur. Zoological Journal of the Linnean Society 122:291–348. Swofford, D. L. 1993. PAUP: Phylogenetic Analysis Using Parsimony, version 3.1. Computer program distributed by the Illinois Natural History Survey, Champaign, Illinois. Taquet, P. 1976. Geologie et paleontologie du gisement de Gadoufaoua (Aptien du Niger). Editions du Centre National de la Recherche Scienfitique Cashiers de Paleontologie, Paris:1–191. Weishampel, D. B., and J. R. Horner. 1990. Hadrosauridae; pp. 534– 561 in D. B. Weishampel, P. Dodson, and H. Osmolska (eds.), The Dinosauria. University of California Press, Berkeley. ———, D. Grigorescu, and D. B. Norman. 1993. Telmatosaurus transsylvanicus from the Late Cretaceous of Romania: the most basal hadrosaurid dinosaur. Palaeontology 36:361–385. Received 24 January 2000; accepted 20 November 2000.



Characters and character state polarities used to determine the phylogenetic status of Eolambia caroljonesa. Characters 1–20 and references for taxon character states are from Head (1998), and Norman, 1998 for Altirhinus. 21. Accessory surangular foramen: 0 5 present; 1 5 absent (Kobayashi and Azuma, 1999). An accessory surangular foramen located anterior to the surangular foramen is present primitively in Iguanodon, Ouranosaurus, Altirhinus, and Eolambia. 22. Eight or more sacral vertebrae: 0 5 absent; 1 5 present (Weishampel and Horner, 1990). A sacrum composed of eight vertebrae or more occurs in lambeosaurines and hadrosaurines. 23. Ventral sacral ridge: 0 5 absent; 1 5 present (Weishampel et al., 1993; Kirkland, 1998). A longitudinal ridge extending along the midline of the ventral surface of the sacrum occurs in Ouranosaurus, Lambeosaurinae, and Telmatosaurus. A shallow groove occurs in the same position in all other derived iguanodontians for which the sacrum is known (The sacrum illustrated for Probactrosaurus does not reveal either condition, Lu, 1997: 38). 24. Iliac antitrochanter: 0 5 absent; 1 5 present (Weishampel and Horner, 1990). A prominent ‘‘antitrochanter’’ originating from both the lateral and dorsal margins of the ilium is located posteriodorsally to the acetabulum in Bactrosaurus, Gilmoreosaurus, Hadrosaurinae, and Lambeosaurinae. 25. Separate iliac postpubic process: 0 5 absent; 1 5 present. A distinct, separate postpubic process that is excluded from the reflection of the iliac dorsal margin, and often possesses an elongate anterior ‘‘neck’’ is present in Bactrosaurus, Gilmoreosaurus, Hadrosaurinae, and Lambeosaurinae. 26. Enclosed femoral anterior intercondylar groove: 0 5 absent; 1 5 present (Weishampel and Horner, 1990; Weishampel et al., 1993). Enclosure or near enclosure of the distal anterior intercondylar groove of the femur occurs in Telmatosaurus, Gilmoreosaurus, Bactrosaurus, Hadrosaurinae, and Lambeosaurinae. 27. Anteroposteriorly shortened supratemporal fenestrae: 0 5 absent; 1 5 present. Supratemporal fenestrae that are approximately rounded are present in Ouranosaurus, Probactrosaurus, CEUM specimens referred to Eolambia, and Lambeosaurinae.

APPENDIX 2 Data matrix of iguanodontian dinosaurs incorporated in determining the phylogenetic status of Eolambia caroljonesa. Character state distributions for characters 1–20 are from Head (1998), except for characters 17 and 19 which were rescored in accordance with the character descriptions of Forster (1997). Bold numbers represent character states for Eolambia based on observations of OMNH specimens. All other states are from Kirkland (1998, pers. comm.). Characters states prefaced by ‘‘?/’’ for Eolambia and Bactrosaurus indicate states based on interpretations in Kirkland (1998) and Godefroit et al. (1998). Character Taxon Iguanodon Ouranosaurus Altirhinus Probactrosaurus Eolambia Protohadros Telmatosaurus Gilmoreosaurus Bactrosaurus Hadrosaurinae Lambeosaurinae

10 0 1 0 0 0 1 1 ? 1 1 1

0 0 0 ? 0 0 0 ? 1 0 1

0 0 0/? 0 ? 1 1 1 ?/1 1 1

0 0 0 ? 0 0 0 0 0 0 1

0 1 0 0 0 0 1 0 0 1 1

0 0 0 0 0 0 0 0 0 ? ? ? 0 ? 0 0 0 0 1 0/? 0 1 0 0 1 1 0 1 1 1 1 1 1

0 0 0 0 ? 1 1 1 ?/0 1 1

0 0 0 ? 0 0 1 ? 1 1 1

20 0 0 0 ? 0 0 1 ? 1 1 1

0 0 0 0 0 0 0 0 0 0 1

0 1 1 0 0 1 0 0 0 1 1

0 0 1 1 ?/1 1 1 1 1 1 1

0 0 1 1 1 1 1 1 1 1 1

0 0 0 1 1 1 1 1 1 1 1

0 0 0 0 0 0 0 0 0 1 1

0 0 0 0 0 0 0 1 1 1 1

0 0 0 ? 0 0 0 ? 0 1 1

1 0 0 ? 0 0 0 ? 0 1 0

27 0 0 0 ? 0 1 1 1 1 1 1

0 0 0 0 0 ? ? 0 0 1 1

0 1 0 0 0 ? 1 0 0 0 1

0 0 0 0 0 ? ? 1 1 1 1

0 0 0 0 0 ? ? 1 1 1 1

0 0 0 1 0 0/? 0 1 0 1 ? ? 1 0 1 0 1 0 1 0 1 1

Head, 2001