An ethmoid exposure (os planum) in the orbit of Indri indri (Primates Lemuriformes).код для вставкиСкачать
I3 R IEF COMM UNI CAT10N An Ethmoid Exposure ( 0 s Planum) in the Orbit of lndri indri (Primates, Lemuriformes) M. CARTMILL AND P. D. GINGERICH Departments of Anatomy and Anthropology, Duke liniuersity, Durham, North Carolina 2771 0 and Museum of Paleontology, Uniuersity of Michigan, Ann Arbor, Michigan 48109 KEY WORDS Ethmoid Indri . Indriidae - 0 s planum - Orbit . Prosimians . ABSTRACT In 6 of 17 skulls of Indri indri retaining distinct sutures in the medial orbital wall, a small separate bony element intervenes between the frontal and the maxillolacrimal suture. This element is demonstrably continuous with the ethmoid on one such skull. The occurrence of an ethmoid exposure in the orbit of Indri suggests that this trait is not a simple function of orbital size and convergence. Since such an exposure is found in non-cheirogaleine lemuriforms, its distribution provides no support for the hypothesis that lorises and galagos are derived from cheirogaleines. J. F. Meckel, G. Cuvier, and other early students of the comparative anatomy of primates proposed that the 0s planum, or periorbital surface of the ethmoid, is a distinctive feature of higher primates which does not appear in prosimians. Major ('Ola,b) identified and figured an 0 s planum in the medial orbital wall of Tarsius, all the lorisiform prosimians, and the lemuriforms Microcebus, Lemur, Lepilemur, Hapalemur, Avahi, and Propithecus. Jones ('17) examined skulls of fetal and adult Lemur and concluded that the bone which Major had identified as the planum in Lemur catta was in reality the inflated presphenopalatine lamina of the palatine bone. Seeking support for his "tarsioid theory" of human origins, Jones mistakenly extended his findings to all strepsirhine prosimians (Jones, '29: p. 123), concluding that the strepsirhines uniformly lack an 0s planum and should be excluded from the order Primates by virtue of this and other respects in which they differ from the tarsier-anthropoid assemblage (Jones, '29: p. 144). A more nearly correct account was provided by Kollman ('20, '25), who used sectioned fetal material to prove that Major had correctly identified an 0s planum in the lorisiforms and Microcebus, but had mistaken the palatine for the ethmoid in Lemur, Lepilemur, and Avahi. Kollman was unable to find an 0s planum in juvenile or fetal specimens of Lemur fuluus, AM. J. PHYS. ANTHROP. (1978)48: 535-538. Hapalemur griseus, Lepilemur mustelinus, Phaner furcifer, Propithecus verreauni, Avahi, Zndri, or Daubentonia. He concluded that the 0s planum was a primitive primate feature that had been secondarily lost in all the Madagascar lemurs except Cheirogaleus and Microce bus. More recent authors have accepted Kollman's account as authoritative, although interpretations of his findings vary. Some authors follow Kollman in regarding the shared occurrence of t h e 0 s planum in lorisiforms and cheirogaleines as a primitive retention, reflecting the generally primitive character of these small nocturnal primates (Charles-Dominique and Martin, '70; Cartmill, '71). Others regard the planum as a convergence between cheirogaleines and lorisiforms (Simons and Russell, '60; Szalay, '71; Gingerich, '761, or as a shared specialization arguing for a recent derivation of Lorisiformes from a cheirogaleine ancestor (Cartmill, '75). These interpretations, however, presuppose that the 0s planum is unique to the cheirogaleines among Madagascar lemurs. We here report the occasional occurrence of an ethmoid element in the medial orbital wall of the indriid Zndri indri. We have examined 53 skulls of Indri in 7 museums in the United States and Europe. Of these, 17 (32%) retained unfused sutures in the medial orbital wall. In six of these 17 535 536 M. CARTMILL AND P. D. GINGERICH Fig. 1 Medial wall of left orbit of Indri indri, Leiden No. “H.” E, presumed ethmoid (0s planum); F, frontal; L, lacrimal; M, maxilla; P, palatine; Z, zygomatic. Fig. 2 Right orbital region of immature Indri indri, American Museum of Natural History No. 100509, lateral view. N, nasal; S, squamosal; other lettering as in figure 1. Scale indicates 5 mm. 0s PLANUM OF INDRI 08 537 Fig. 3 Indri indri, American Museum of Natural History No. 100509, ventral view. E, ethmoturbinal I; P, planum; R, roof of orbit (frontal bone) skulls (35x1, the frontal was separated from rated orbits (Cartmill, '70) tends to refute the the maxillo-lacrimal suture by a small dis- conjecture that the presence or absence of an crete bone (fig. 1). Damage to a specimen ethmoid element in the orbital mosaic de(No. 9.811-16) in the Cleveland Museum of pends wholly on the size and convergence of Natural History reveals this to be an exposure the orbits (Simons and Russell, '60; Cartmill, of a larger bony lamina directly underlying, '71; Gingerich, '76). The 0s planum's interest but not fused with, the orbital wing of the to systematists is correspondingly increased. frontal. This underlying element was most ex- However, its presence in Indri, coupled with tensively exposed in the orbit of an infant the occurrence of an apparently homologous Indri, American Museum of Natural History element in the orbital mosaic of some Adupis No. 100509, in which the orbital processes of (Gingerich and Martin, '78, in preparation), the maxilla and frontal remain partly unossi- suggests that a n 0s planum may be an anfied (fig. 21, although ossification has pro- cestral lemuroid character. If so, its occurceeded far enough to demonstrate that the rence in cheirogaleines and lorisiforms proupper end of the underlying element's exposed vides no support for the hypothesis that these part was in contact with the periorbita. Dam- two groups of prosimians share a more recent age to the left side of this skull reveals that common ancestry than either does with nonthis element is continuous with the ethmotur- cheirogaleid Madagascar lemurs (Szalay and binals (fig. 3). We conclude that the discrete Katz, '73; Tattersall and Schwartz, '74; Cartelement seen in some adult skulls a t this point mill, '75). We thank P. Napier (British Museum, also represents the ethmoid, and is therefore a true 0s planum. In most adult specimens, the Natural History); J. Lessertisseur (Institut planum has either fused with, or disappeared d'Anatomie Comparee, Paris) 1 L. B. Holthuis (Rijksmuseum van Naturlijke Historie, beneath the surrounding membrane bones. The occurrence of an 0s planum in Zndri, Leiden); F. A. Jenkins, Jr., D. McClearn, M. E. which has relatively small and widely-sepa- Rutzmoser, and A. C. Walker (Museum of 538 M. CARTMILL AND P. D. GINGERICH Comparative Zoology, Harvard) ; S. Anderson (American Museum of Natural History); C. Howe, D. C. Johanson, and W. Kimbel (Cleveland Museum of Natural History); and H. W. Setzer and R. W. Thorington, Jr. (U. S. National Museum), for facilitating our access to t h e collections of their respective museums. The senior author’s travel and research was made possible by NIH Grant l-KO4-HD0008301; t h a t of t h e junior author was aided by t h e Turner Fund of t h e University of Michigan’s Department of Geology. We thank K. Brown, R. F. Kay, and R. D. Martin for their help and suggestions. LITERATURE CITED Cartmill, M. 1970 The Orbits of Arboreal Mammals: A Reassessment of the Arboreal Theory of Primate Evolution. Ph.D. thesis, University of Chicago. 1971 Ethmoid component in the orbit of primates. Nature, 232: 566-567. 1975 Strepsirhine basicranial structures and the affinities of the Cheirogaleidae. In: Phylogeny of the Primates. W. P. Luckett and F. S. Szalay, eds. Plenum, New York, pp. 313-354. Charles-Dominique, P., and R. D. Martin 1970 Evolution of lorises and lemurs. Nature, 227: 257-260. Gingerich, P. D. 1976 Cranial anatomy and evolution of early Tertiary Plesiadapidae (Mammalia, Primates). Papers on Paleontol., Univ. Mich. Mus. Paleontol., 15: 1-140. Gingerich, P. D., and R. D. Martin (1978, in preparation) The Cambridge skull of Adapis parisiensis. Jones, F. W. 1917 The structure of the orhito-temporal region of the skull of Lemur. Proc. Zool. Soc. London, 1317: 323-329. 1929 Man’s Place Among the Mammals. E. Arnold and Co., London. Kollman, M. 1920 L’os planum des Lemuriens. Bull. SOC. Linn. Normandie, Ser. 7, 2: 216-219. 1925 Etudes sur lea Gmuriens. La fosse orhitotemporale e t 1’0splanum. Mem. SOC. Linn. Normandie n.s (Zool.), 1: 1-20. Major, C. I. F. 1901a On some characters of the skull in lemurs and monkeys. Proc. Zool. SOC.London, 1901: 129-153. 1901b On Lemur mongoz and Lemur rubriventer. Proc. Zool. SOC. London, 1901: 248-268. Simons, E. L., and D. E. Russell 1960 Notes on the cranial anatomy of Necrolemur. Breviora Mus. Comp. Zool. (Harvard), 127: 1-14. Szalay, F. S. 1971 Cranium of the late Palaeocene primate Plesiadapk tricuspidens. Nature, 230: 324-325. Szalay, F. S., and C. C. Katz 1973 Phylogeny of lemurs, galagos and lorises. Folia primatol., 19: 88-103. Tattersall, I., and J. H. Schwartz 1974 Craniodental morphology and the systematics of the Malagasy lemurs (Primates, Prosimii). Anthrop. Papers Am. Mus. Natur. Hist., 52: 139-192.