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Giant Camels from the Cenozoic of North America

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Giant Camels from the Cenozoic of North America SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY • NUMBER 57 Giant Camels from the Cenozoic of North America Jessica A. Harrison SMITHSONIAN INSTITUTION PRESS City of Washington 1985 ABSTRACT Harrison, Jessica A. Giant Camels from the Cenozoic of North America. Smithsonian Contributions to Paleobiology, number 57, 29 pages, 17 figures, 1985.—Seven genera of giant camels occurred in North America during the interval from the late Clarendonian to the early Holocene. Aepycamelus was the first camel to achieve giant size and is the only one not in the subfamily Camelinae. Blancocamelus and Camelops are in the tribe Lamini, and the remaining giant camels Megatylopus, Titanotylopus, Megacamelus, Gigantoca- melus, and Camelus are in the tribe Camelini. Megacamelus is a late Hemphil­ lian giant camel most closely related to Gigantocamelus. Titanotylopus is reserved for the brachyodont form from the Irvingtonian of Nebraska, and Gigantocamelus is reinstated for the broad-chinned, Blancan form. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The trilobite Phacops rana Green. Library of Congress Cataloging in Publication Data Harrison, Jessica A. Giant camels from the Cenozoic of North America. (Smithsonian contributions to paleobiology ; no. 57) Bibliography: p. Supt. of Docs, no.: SI I.30:.57 \. Camels, Fossil. 2. Paleontology—Cenozoic. 3. Paleontology—North Amer­ ica. I. Title. II. Series. QE701.S56 no. 57 [QE882.U3] 560s [599.73'6] 84-600303 Contents Page Introduction I Acknowledgments I Phylogenetic Relationships 1 Aepycamelus 4 Megatylopus 5 Titanotylopus 7 Gigantocamelus 8 Megacamelus 10 Megacamelus merriami, new combination II Camelus 21 Blancocamelus 23 Camelops 24 Summary 24 Literature Cited 26 111 FRONTISPIECE.—Reconstruction ofthe head of Megacamelus merriami. Giant Camels from the Cenozoic of North America Jessica A, Harrison Introduction (UCMP), the University of Nebraska State Mu­ seum (UNSM), and the University of Kansas Throughout the later Cenozoic, camels often Museum of Natural History (KUVP). I very figure as an abundant and diverse element of any much appreciate careful and constructive reviews fauna in which they occur. Until the late Pleis­ by George Corner, Michael Voorhies, John tocene, when the group fell on hard times, the Breyer, and Robert Emry. Drs. Corner and Camelidae must be accounted one of the more successful ungulate families. As in many other Voorhies were particularly generous in sharing herbivore families, the earliest members of the with me their new information on Titanotylopus. Camelidae were of small body size. However, a The frontispiece was done by Robert Hynes. trend toward gigantism can be observed throughout the later Cenozoic, from the Clar­ endonian into the Holocene. Phylogenetic Relationships Descriptions of very large camels are almost as The cladogram in Figure 1 summarizes rela­ abundant in the literature as their remains in late tionships within the Camelinae. It is interesting Cenozoic faunas. The confusing taxonomic his­ to note that the trend toward gigantism is far tory of the giant camels is such that, for every more apparent in the Camelini than in the Lam­ specific identification, there are many more re­ ini. All of the genera comprising the Camelini ferrals to "camelid, large, gen. et sp. indet." The can be called giants, but only two of the Lamini, purpose of this paper is to provide a temporal, Camelops and Blancocamelus, achieve a formida­ geographic, and systematic framework for the ble body size. Aepycamelus, the only noncameline large, late Cenozoic camels. genus, represents the camels' earliest experimen­ ACKNOWLEDGMENTS.—I am grateful for the tation with gigantism. use of specimens from the Frick Collection, De­ The characters appearing at nodes 1 through partment of Vertebrate Paleontology, American 35 in the cladogram are listed below. The com­ Museum of Natural History (F:AM), the Univer­ position and apomorphies of the Protolabidini sity of California Museum of Paleontology are from Honey and Taylor (1978:419-420), whereas those of the Lamini and Camelini ap­ Jessica A. Harrison, formerly Department of Paleobiology, Na­ peared in part in Harrison (1979:3-8). More tional Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, now Research Associate, Department detailed discussion of the characters may also be of Geosciences, University of Arizona, Tucson, Arizona 85721. found in those papers. SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Camelinae 1 Protolabidini Lamini Camelini Tr 1 r T .^ <# 9 J> x'^ ..^ ^^ ^/ V<?^°"' #y <?<?yX/M" <^* ^^®" <^'^''" <?* " \?^" /^'^''' /^' // //// FIGURE 1.—Relationships within the Camelinae. Node 1. Aepycamelus shares with the Camelinae a. hypsodont molars a. metastylid present on the lower molars b. anteroposteriorly elongate Mi Node 2. Aepycamelus is distinguished by c. very weak to absent metastylid on lower molars a. extremely elongate limbs d. ventrally produced mandibular angle with weak b. extremely elongate cervical vertebrae to strong lateral flare c. metapodials longer than the basal length of the e. fused metapodials skull f. elongate proximal phalanx with distal articular Node 3. The Camelinae are united by surface anteriorly extended weak buccinator fossa Node 8. Michenia is derived relative to Protolabis in hav­ b. elongate rostrum ing Node 4. The Protolabidini are united by a. short braincase a. narrow rostrum b. weak P-C', small Ci b. laterally expanded anterior nares c. shallow .symphysis Node 5. Tanymykter is distinguished by d. inflection of mandibular angle suppressed a. closely appres,sed Pj roots Node 9. The Camelinae exclusive of the Protolabidini Node 6. Protolabis and Michenia are derived relative to are united by Tanymykter by a. metacarpal length exceeds metatarsal length a. the absence of elongate basioccipital tuberosities b. metapodials completely fused b. P" without strong, continuous lingual cingulum c. I' absent c. auditory bulla less inflated with medial plates Node 10. Procamelus is the sister taxon to the remaining more compressed camelines. d. moderate to strong buccinator fossa It retains several primitive characters but has Node 7. Protolabis is distinguished by almost completed the loss of I*"^ NUMBER 57 Node 11. The Lamini share with the Camelini Ps absent a. I'^ absent dorsal surface of the mandibular condyle trans­ b. Pi absent versely concave c. raised posterolateral edges on the proximal end suspensory ligament scar extends to center of of the proximal phalanx proximal phalanx and has a raised center Node 12. The Lamini are united by Node 27. The Camelini are united by a. in cross section the anterior end of the nasals a. angular process on mandible enlarged and form a high, bilobed arch (Harrison, 1979, fig. strongly inflected 3) large postglenoid foramen b. anteroexternal style (= llama buttress) present long postglenoid process on skull with corre­ on lower molars spondingly large facet on mandibular condyle Node 13. Pliauchenia, Hemiauchenia, {?)Blancocamelus, Pa- Cl enlarged and rounded in cross section, espe­ laeolama. Lama, and Vicugna share cially in males a. reduced lacrimal vacuity e. ventrally flattened auditory bulla b. shortened rostrum f diastemal crest on mandible low and rounded Node 14. Pliauchenia is primitive in all known characters g- reduced maxillary fossa h. to the remaining Lamini. thickened, heavy premaxilla Node 15. Hemiauchenia, {})Blancocamelus, Palaeolama, Node 28. Megatylopus and Titanotylopus share Lama, and Vicugna are united by a. reduced Pi a. small Pi b. reduced P3 b. small or absent P3 Node 29. Megatylopus is distinguished by Node 16. Hemiauchenia and Blancocamelus share a. reduced P' a. extremely elongated metapodials b. cheek teeth higher crowned than Titanotylopus Node 17. Hemiauchenia is distinguished by Node 30. Titanotylopus is derived relative to Megatylopus in a. extremely elongated cervical vertebrae having Node 18. fi/a7icocaOT^/u.j is distinguished by a. P] absent a. great size b. P3 more reduced than in Megatylopus Node 19. Palaeolama, Lama, and Vicugna share c. larger body size than Megatylopus a. ?! absent Node 31. Megacamelus, Gigantocamelus, and Camelus share b. reduced maxillary fossa a. metapodials shorter in relation to basal length c. moderate to strong anteroexternal style on lower ofthe skull molars cheek teeth more hypsodont than Megatylopus or Node 21. Lama and Vicugna are derived relative to Palaeo­ Titanotylopus lama in having Node 32. Megacamelus and Gigantocamelus share a. P3 absent a. spatulate lower incisors b. metacarpal length subequal to metatarsal length b. splayed Ci c. strong anteroexternal style on lower molars Node 33. Megacamelus is primitive in all characters relative d. greatly reduced lacrimal vacuity to Gigantocamelus except for e. extremely retracted nasals a. 1' enlarged and caniniform f. greatly reduced P4 Node 34. Gigantocamelus is distinguished by Node 22. Lama is distinguished by a. short, blunt chin with a shortened ramal sym­ a. callosities on the inner foreleg physis Node 23. Vicugna is distinguished by b. greater size than Megacamelus a. hypsodont lower incisors c. lower incisors arrayed almost transversely Node 24. Alforjas and Camelops are derived relative to d. 1' absent or vestigial other lamines in having Node 35. Camelus is distinguished by a. moderately hypsodont to very hypsodont molars a. reduced paroccipital process b. cheek teeth narrow in relation to
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