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Home , Eolambia, Iguanodon, Iguanodontia, Iguanodontidae, Matanuska Formation, Ouranosaurus

Asociación Paleontológica Argentina. Publicación Especial 7 ISSN 0328-347X VII International Symposium on Terrestrial : 107-111.Buenos Aires, 30-6-2001

Biogeographic histories and chronologies of derived iguanodontians

Jason J. HEADl and Yoshitsugu KOBAYASHp.2

Abstract. The geographic distributions, chronology, and phylogenetic relationships of derived iguan- odontians describe a biogeographic history of active intercontinental dispersal, which is tested via com- parison with eustatic sea level fluctuations. A revised phylogeny of derived iguanodontians does not sup- port a monophyletic , and produces a lineage culminating Hadrosauridae that is first recorded in the early Late of both and . This distributions suggests dis- persal between Asia and North America during the . Biogeographic hypotheses describ- ing isolation of North America during the are not supported by sea level data. Dispersal patterns among Late Cretaceous taxa are corroborated by short term regressive phases in sea levels, but no distinction can be made between hypotheses of dispersal in both directions, and repeated immigration of Asian taxa into North America.

Keywords. Cretaceous. Biogeography. Dispersa!. Sea levels. . Hadrosauridae.

Introduction Sea level histories can be used as an independent test of biogeographic hypotheses. On a geologic The purpose of this analysis is to incorporate a re- timescale, trans-continental distributions of taxa are vised phylogeny of derived iguanodontian di- contro11edby tectonic processes, induding resultant nosaurs (Hadrosauriformes sensu Sereno, 1999)into sea level fluctuations, which affect areas of emer- a biogeographic and chronological history, and to gence. Eustatic transgressive and regressive events test this history against concurrent sea level fluctua- altemately prohibit and facilitate active dispersal tions. Specifically,we: (1) construct a phylogeny of across seaways and landbridges. A11else being derived iguanodontians; (2) use that phylogeny to equal, pattems of distribution should be correlated augment biogeographic histories, and; (3) test both to sea level changes. First occurrences of hypotheti- previous and new hypotheses of Early and Late cal immigrants should be preceded by short- or long- Cretaceous biogeography by comparison with sea term regressive events, and periods of isolation levels as an indicator of potential for dispersal. should coincide with transgressions. Iguanodontians are Laurasian in origin, with active dispersal and local driving trans-conti- nental distributions (Brett-Surman, 1979; Norman Materials and methods 1998a). Iguanodontians dispersed into North Africa A phylogeny of derived iguanodontians (figure 1) at least once prior to the mid- (Taquet and was constructed from 12 taxa and 24 characters (ap- Russell, 1999),but our analysis focuses on Laurasian pendix 1). Critical assumptions of our phylogeny are biogeography. Timing and direction of dispersals are monophyly of Hadrosaurinae and not well resolved for a11higher order taxa, but phy- (Weishampel and Homer, 1990). Claosaurus and logenetic relationships and first occurrences suggest are poorly known, but their geographic and both an ancestral center of origin and a minimum temporal distributions are significant. They were timing of immigration for a lineage. Currently, how- manua11yplaced in our phylogeny, and their posi- ever, no additional test of dispersal biogeography tions are more tentative than other taxa. The phy- has been proposed. logeny was placed in a geographic and chronological context, and the Cretaceous eustatic sea level curves 'Department of Geological Sciences and Shuler Museum of of Haq et al., 1987(figure 2) were used to test the re- Paleonlology, Soulhern Melhodisl Ul\iv~rsity, Dallas TX 75275, sultant biogeographic hypotheses. We use the USA. 'Fukui Prefectural Museum, 51-11 Terao, Muroko, Westem Interior Seaway as the indicator of potential Katsuyama, Fukui 911-8601 [apan. dispersal and isolation because: (1) transgressive

©Asociación Paleontológica Argentina 0328-347X/01$00.00+50 108 J.J. Head and Y.Kobayashi events including initial completion of the Seaway lguanodon (102Ma) are temporally constrained, and can be cor- related to global sea levels to provide a measure of sea level required to isolate dispersal routes, and; (2) it is correlated to a well-sampled terrestrial fauna Fukui form (Jacobs and Winkler, 1998). Altirhinus

Phylogeny and biogeography

Our phylogeny is generally consistent with pub- lished studies, with two exceptions: Our study does L...- not support a monophyletic Iguanodontidae (Norman, 1998a), and Eolambia forms an unresolved trichotomy with Probactrosaurus and more derived L...- taxa, as opposed to being a lambeosaurine Gilmoreosaurus (Kirkland, 1998).We have achieved only limited res- L...- olution of the interrelationships among some taxa ------Claosaurus due, in part, to both the small number of characters used in our analysis and missing data. However, this - ---- Tanius lack of resolution also mirrors controversy among more exhaustive analysis (e.g., Norman 1998a, "--- Sereno, 1999). A new taxon, the Fukui form, from [apan (?-?Aptian) is significant because it ~L[Hadrosaurinae represents the first occurrence of characteristics pre- Lambeosaurinae viously considered diagnostic of more derived (Kobayashi and Azuma, 1999), and because it in- Figure 1. Strict consensus of 13 ( length = 37 steps, Cl. = creases the diversity of Early Cretaceous - .70, and R.l. = .65) of ingroup relationships determined via a tians. The low resolution of interrelationships of heuristic search in PAUP 3.1 (Swofford, 1993),exclusive of Tanius Iguanodon, Ouranosaurus, Altirhinus, and the Fukui and Claosaurus (dashed lines). , , and were used as successive outgroups. form limit biogeographic reconstructions. However, the phylogenetic polytomy of these taxa does not sig- These distributions suggest a biogeographic pat- nificantly alter current biogeographic hypotheses. tern of alternating intervals of dispersal between Norman (1998a) described a history of Laurasiatic North America and Asia from the beginning of the dispersal of Iguanodon prior to the Hauterivian, fol- Late Cretaceous to the , but the directions of lowed by North American isolation and European- dispersal are not constrained. Intervals of dispersal Asian connection by the Aptian. Isolation of North are separated by periods of endemism and in situ America is considered to have persisted until the lat- . Hypotheses of in situ evolution are sup- est (Kirkland et al., 1997), based on North ported by short phylogenetic distances that are re- American faunal endemicity. stricted to brief periods of time, and geographic con- Systematic relationships of more derived taxa currence shared between Eolambia and Protohadros placed in a chronological and biogeographic frame- (and possibly Claosaurus) and between work represent a progressive transition series culmi- Gilmoreosaurus, Bactrosaurus, and Tanius. nating in Hadrosauridae (sensu Forster, 1997). This Geographic distributions indica te a late Early grade begins with Probactrosaurus in the Early Cretaceous dispersal of Eolambia into North America, Cretaceous of Asia, and with early-middle Late with subsequent divergence of Protohadros and Cretaceous Eolambia and Protohadros lin North Claosaurus, and a second migration into Asia prior to America, and with a series of Asian hadrosauroids the Turonian, with subsequent divergence of (Godefroit et al., 1998)approximately coeval with the hadrosauroids, followed by Hadrosauridae. The first occurrences of Hadrosauridae in the Turonian of phylogenetic status of Telmatosaurus requires an ad- North America and Asia (Weishampel and Horner, ditional dispersal back into Asia, between the first oc- 1990;Pasch, 1995). Ages of Asian hadrosauriods are currences of Protohadros and Claosaurus. The system- ambiguous, but the first occurrence of atic status of Claosaurus is tentative, however, and the Hadrosauridae minimally constrains divergence necessity of additional dispersal into Asia can only be times (MDTs Weishampel et al., 1993) of successive determined once the relative positions of sister taxa to the base of the Turonian. Telmatosaurus and Claosaurus are resolved.

A.P.A. PublicaciónEspecial7,2001 Biogeography of derived iguanodontians 109 Distributions of hadrosaurids indicate Laurasian dis- dispersal routes, resulting in intercontinental faunal persals by the Turonian, followed by migration into similarity. There are six intervals in the Late South America by the , and Antarctica by Cretaceous when sea levels fall below completion of the (Brett-Surman, 1977; Case et al., the WIS, presumably reflecting intervals of greater 1998). likelihood for intercontinental dispersal, and fauna s should represent alternating periods of endemicity Comparison with sea levels and immigration. Lowered Early Cretaceous sea levels are inconsis- Long- and short term trends in Cretaceous sea tent with hypotheses of isolation and endemicity levels are described in figure 2. Sea levels increased during the Early Cretaceous. We offer two alternate during the Albian, with a maximum transgressive explanations: (1) Ecological or additional tectonic highstand during the Turonian. All else being equal, events (e.g., the opening of the North Atlantic by the lowered sea levels should facilitate dispersal of ter- Hauterivian Ziegler, 1988). restricted dispersals, de- restrial organisms, and conversely highstands should spite lowered sea levels: or (2) Apparent faunal en- inhibit terrestrial dispersal. If these assumptions are demicity is an artifact of insufficient sampling of low- generally true, sea level at the completion of the er Cretaceous terrestrial deposits, or comparing fau- , which formed a physical nas that are not coeval. Recent discoveries of iguan- barrier separating eastern and western North odontian remains in the mid-Aptian of (figure America, can be taken as an arbitrary measure to 2) (Iacobs and Winkler, 1998),as well as the range ex- which comparisons can be made. By this measure, tension of the Asian ?mid-Aptian triconodont sea levels prior to 102 Ma should provide access to Gobiconodon in North America (Ienkins and Schaff,

200 100 O(m) Eurasia N. America

(Ma) Maa 70

Cmp 80

San Con 90 Tur

Cen Protohadros

100 Eolambia

Alb

11 Probactrosaurus gen. et sp. indet. Apt Altirhinus

20 Fukui Form

Bar

lguanodon

Figure 2. Temporal and geographic distributions of iguanodontians compared to PGIS (Ross, 1991) paleogeographic reconstructions and eustatic sea level curves of Haq et al., 1987. 5haded regíons of temporal and geographic distnbutions indicate known ranges for hadrosaurids (dark), and lguanodon (light). For sea level curves, dashed line indicates sea level at completion of the Western Interior Seaway (Jacobs and Winkler, 1998), and shaded regions of short and long term curves indicate periods of open dispersal routes. For maps, darkest grey indicates highlands, medium gray indicates lowlands, lightest gray indicates continental seaways.

A.P.A. Publicación Especial 7, 2001 110 J.J. Head and Y. Kobayashi 1988), suggests connection between Asia and North WQQQlmrne, M,O, 199a, The fir t IwgrQ~ª1Jr {fQl11Antí\r~ti~í\, America during the Aptian, and supports the second [ournal of Vertebrate 18 (suppl. to 3): 32A. Forster, C. M. 1997. Phylogeny of the Iguanodontia and explanation. Hadrosauridae. [ournal of Vertebrate Paleontology 17(suppl. Application of sea level histories to Late 3):47A. Cretaceous iguanodontian biogeography provides Godefroit, P., Dong, Z.-M., Bultynck, P. and Feng, 1. 1998. Sino- temporal constraint to patterns of dispersal, indicates Belgian Cooperation Program, Cretaceous and mammals from . 1. New Bactrosaurus multiple episodes immigration, but does not neces- (Dinosauria: ) material from Iren Dabasu sarily support hypotheses of in situ evolution. Short (Inner Mongolia, P.R China). Bu/letin De L' Institut Royal des term regressions preceded the first occurrences of Sciences Nature/les de Be/gique 68: 1-70. Eolambia, Protohadros, Claosaurus, and Hadrosauridae Haq, B. U., Hardenbol, J. and Vail, P.R 1987. Chronology of fluc- tuating sea levels since the . Science 235: 1156-1167. (figure 2). Based on the youngest ages for Eolambia Head, J.J. 1998. A new species of basal hadrosaurid (Dinosauria, (98.3Ma, Kirkland, 1998),immigration from Asia oc- ) from the of Texas. [ournal of curred prior to the 102Ma transgression. The first oc- Vertebrate Paleontology 18: 718-738. currence of Protohadros (""95.5 Ma) after a short term Head, J.J. 1999. A reassessment of the phylogenetic status of Eolambia caroljonesa (Ornithischia: Iguanodontia), with com- regression implies dispersal. Currently, however, ments on the North American Iguanodontian record. [ournal of there is no Asian equivalent to Protohadros. The oc- Vertebrate Paleontology 19 (suppl. to 3): 50A currence and timing of Claosaurus is ambiguous: if Horne, G.5. 1994. A mid-Cretaceous ornithopod from central basal to Telmatosaurus, it may be a represent a contin- Honduras. [ournal Vertebrate Paleontology 14: 147-150. [acobs.L, 1. and Winkler, O. A. 1998.Mammals, archosaurus, and uation of the North American record, which requires the Early to Late Cretaceous transition in North-Central Texas. a dispersal into Asia prior to the divergence of more In: Tomida, Y.,Flynn, 1. J. and [acobs, L. 1. (eds.), Advances in derived hadrosauroids. If more derived than Vertebrate Paleontology and Geochronology. National Science Telmatosaurus, it may represent a late-surviving, im- Museum Monographs 14, Tokyo, pp. 253-280. [enkins, F.A. jr. and Schaff, C.R 1988. The Early Cretaceous migrant hadrosauroid from Asia, with potential dis- Mammal Gobiconodon (Mammalia, Triconodonta) from the persal either concurrent with Hadrosauridae or dur- Cloverly Formation in Montana. [oumal of Vertebrate ing the Coniacian. The Laurasiatic distribution of Paleontology 8: 1-24. Hadrosauridae is correlated with the pronounced Kirkland, J.r. 1998. A new hadrosaurid from the upper (Albian-Cenomanian: Cretaceous) of Turonian regression (figure 2). This phase may have eastern -the oldest known hadrosaurid (Larnbeo- also provided dispersal routes into Central America saurinae?). In: Lucas, S.G., Kirkland, J.r. and Estep, J.w. (eds.), for North American iguanodontians (Horne, 1994). Lower and Middle Cretaceous Terrestrial Ecosystems. New Mexico Museum of Natural History and Science Bulletin 14, pp. 283- 295. Conc1usions Kirkland, J.I, Cifelli, R1. and Elder, w.P. 1997. Land-bridge be- tween Asia and North America: Oating its latest Albian A revised phylogeny of derived iguanodontians (Cretaceous) origins and its migration induced extinctions. Geological Society of América, Abstracts with Papers 29:A-462. increases the diversity of Early Cretaceous taxa, but Kobayashi, Y. and Azuma, Y. 1999. Cranial material of a new cannot resolve their interrelationships. Late iguanodontian dinosaur from the Early Cretaceous Kitadani Cretaceous taxa include both North American and Formation of Japan. [oumal ofVertebrate Paleontology 19 (suppl. Asian representatives, suggesting alternating periods to 3): 57A. Norman, O.B. 1998a. On Asian ornithopods (Dinosauria: of dispersal and in situ evolution between the two Ornithischia). 3. A new species of iguanodontid dinosauro continents. Sea levels during the Early Cretaceous Zoological [ournal of the Linnean Society 122:291-348. permit dispersal, despite hypotheses of isolation and Norman, O.B. 1998b. Probactrosaurus from Asia and the origin of hadrosaurs. [ournal of Vertebrate Paleontology 18 (suppl. to 3): endemicity. Short term regressive phases correlate to 66A. patterns of first occurrence during the Late Pasch, A.O. 1995. The significance of a new hadrosaur Cretaceous, suggesting intervals of dispersal. (Hadrosauridae) from the Matanuska Formation (Cretaceous) Distributions of Late Cretaceous taxa may result in south central Alaska. [ournal of Vertebrate Paleontology 15 from either multiple Asian dispersals into North (suppl. to 3): 48A. Ross, M.r. 1991. PGIS / Mac 1.3: Paleogeographic Information America, or dispersals in both directions between the System, version 4.0. Earth In Motion Technologies. continents. Sereno, P. C. 1999.Evolution of dinosaurs. Science 284: 2137-2147. Swofford, O.L. 1993. PAUP: Phylogenetic Analysis Using Parsimony, version 3.1. Computer program distributed by the References Illinois Natural History Survey, Champaign, Illinois. Taquet, P., and Russell, O.A. 1999. A massively-constructed Brett-Surrnan, M.K. 1979. Phylogeny and paleobiogeography of iguanodont from Gadoufaouna, lower Cretaceous of . hadrosaurid dinosaurs. Nature 277: 560-562. Annales du Palaéontologie 85: 85-96. Carpenter, K., Oilkes, O. and Weishampel, O.B. 1995. The di- Weishampel, O.B. and Horner, J.R 1990. Hadrosauridae. In: nosaurs of the Niaobrara Chalk Formation (Upper Weishampel, O.B., Dodson P. and Osmolska, H. (eds.), The Cretaceous, Kansas). [ournal of Vertebrate Paleontology 15: 275- Dinosauria. University of California Press, Berkeley, pp. 534- 297. 561. Case, J.A., Martín, J.E., Chaney, 0.5., Reguero, M. and Weishampel, O.B, Grigorescu, O. and Norman, O.B. 1993.

AP.A. Publicación Especial 7, 2001 Biogeography of derived iguanodontians 111

Telnuuosaurus transsylvanicus from the Late Cretaceous of and Kobayashi and Azuma, 1999. They are: 17) Secondary suran- Romania: the most basal hadrosaurid dinosauro Palaeontology guiar foramen (Present=Ü, Absent=L}; 18) Dental battery extends 36: 361-385 posteriorly beyond coronoid (A=O,P=l); 19) Eight or more sacral Wiman, C. 1929. Die Kreide-Dinosaurier aus Shantung. vertebrae (A=O, Pel ): 20) Prominent iliac antitrochanter (A=O, Palaeontologica Sinica (series C), 6: 1-67. P=l); 21) Femoral anterior intercondylar groove fully enclosed Ziegler, p.A. 1988. Evolution of the Arctic-North Atlantic and the (A=O,Pel): 22) Conical pollex spike (A=O,Pe l): 23) Well-devel- Western Tethys. American Associalion 01 Pelroleum Geologisls oped, discrete iliac postpubíc process (A=O, P=l); 24) Elongate Memoir 34, 198 p. "finger-like" jugal process of the (A=O;P=l).

Accepted: February 1", 200l. 10 20

APPENDIX 1 lguanodon 00000 00000 00000 01000 O 1 O 1 Ouranosaurus 10010 00001 00000 00000 0101 Characters and data matrix used in phylogenetic analysis. Fukui form 00100 00000 00000 OOO?? O??O Characters and states 1- 16 are from Head (1998-minus characters Altirhinus O O O/?OO 00001 10000 00001 ? 101 Probactrosallrus OOOO? ? ? ? ? O 11100 O?OO? 01?0 4, 7, 12, and 20). Additional states are from sources in Appendix 1 Eolambia 00000 O?OOO 11100 00000 O?OO of Head (1998), and the following: Fukui form (Kobayashi and Protohadros 10 1 O O 01001 11100 0100? ???O Azuma, 1999); Altirhinus (Norrnan, 1998a); Probactrosaurus Telmatosaurus 00101 01110 11100 0100? 1?? O (Norman, 1998b);Eolambia (Head, 1999);Bactrosaurus (Godefroit el Gilmoreosaurus ?? 1 ?? O???O 11101 0?001 1?10 al., 1998). Claosaurus and Tanius (Fig. 1) are based on Carpenter el Bactrosallrlls O 11 O 1 0?110 11 10 1 01101 10 1 O al. (1995), and Wiman (1929), respectively. Characters 17-24 are Hadrosaurinae 101 1 1 11111 11 1 1 1 11 1 11 10 1 O Lambeosaurinae from Weishampel and Horner, 1990;Norman, 1998a;Sereno, 1999; 111 1 1 11111 111 1 1 11 1 11 1010

A.P.A. Publicación Especial 7, 2001