Structure of the Ear Region in Living and Subfossil Lemurs

Saban, R

doi:10.1007/978-1-4684-2121-7_6

Cited by 9 publications

(14 citation statements)

References 6 publications

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“…Researchers have usually assumed that canal enlargement or reduction correlates with arterial patency, importance of the artery in nourishment of its destination structures, and/or the size of the target structures of the traversing artery (Saban, 1963(Saban, , 1975Gingerich, 1973;Szalay, 1975;Bugge, 1980;MacPhee and Cartmill, 1986;MacPhee et al, 1988;Gingerich, 2012). Since the primary and only consistent function of the promontorial artery (when patent) is thought to be to supply the brain with blood (Bugge, 1974) our results indicate that future discussions of enlargement or reduction of the promontorial canal may be understood partly as a function of evolutionary changes in absolute brain size.…”

Section: By What Criteria Can Ica Branch Size Be Evaluated?mentioning

confidence: 99%

“…The promontory artery, named for its course adjacent to the promontorium of the petrosal (i.e., the bulge of the cochlea into the middle ear space), supplied blood to the brain via the cerebral arterial circle (of Willis) (Saban, 1963(Saban, , 1975Bugge, 1974;MacPhee and Cartmill, 1986). The stapedial artery, named for its passage through the obturator foramen of the stapes, supplied blood to the meninges, eye, orbit, and parts of the face (Saban, 1963;Bugge, 1974;Wible, 1987).…”

Section: Introductionmentioning

confidence: 99%

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Internal carotid arterial canal size and scaling in Euarchonta: Re-assessing implications for arterial patency and phylogenetic relationships in early fossil primates

Boyer

Kirk

Silcox

et al. 2016

Journal of Human Evolution

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a b s t r a c tPrimate species typically differ from other mammals in having bony canals that enclose the branches of the internal carotid artery (ICA) as they pass through the middle ear. The presence and relative size of these canals varies among major primate clades. As a result, differences in the anatomy of the canals for the promontorial and stapedial branches of the ICA have been cited as evidence of either haplorhine or strepsirrhine affinities among otherwise enigmatic early fossil euprimates. Here we use micro X-ray computed tomography to compile the largest quantitative dataset on ICA canal sizes. The data suggest greater variation of the ICA canals within some groups than has been previously appreciated. For example, Lepilemur and Avahi differ from most other lemuriforms in having a larger promontorial canal than stapedial canal. Furthermore, various lemurids are intraspecifically variable in relative canal size, with the promontorial canal being larger than the stapedial canal in some individuals but not others. In species where the promontorial artery supplies the brain with blood, the size of the promontorial canal is significantly correlated with endocranial volume (ECV). Among species with alternate routes of encephalic blood supply, the promontorial canal is highly reduced relative to ECV, and correlated with both ECV and cranium size. Ancestral state reconstructions incorporating data from fossils suggest that the last common ancestor of living primates had promontorial and stapedial canals that were similar to each other in size and large relative to ECV. We conclude that the plesiomorphic condition for crown primates is to have a patent promontorial artery supplying the brain and a patent stapedial artery for various nonencephalic structures. This inferred ancestral condition is exhibited by treeshrews and most early fossil euprimates, while extant primates exhibit reduction in one canal or another. The only early fossils deviating from this plesiomorphic condition are Adapis parisiensis with a reduced promontorial canal, and Rooneyia and Mahgarita with reduced stapedial canals.

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Section: By What Criteria Can Ica Branch Size Be Evaluated?mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Internal carotid arterial canal size and scaling in Euarchonta: Re-assessing implications for arterial patency and phylogenetic relationships in early fossil primates

Boyer

Kirk

Silcox

et al. 2016

Journal of Human Evolution

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“…To these cases may be added the much more recent Archeoindris, Paleopropithecus, and Megaladapis, three of the sub-fossil Malagasy lemurs. In these forms the ectotympanic is joined to the petrosal and forms a long bony meatus [Saban, 1963[Saban, , 1975. Saban suggests that there may be a correlation between gigantism, the hyperdevelopment of certain muscles originating near the meatus, and the exteriorization of the ectotympanic (which he regards as an evolved feature).…”

Section: Discussion the Production O F The Ectotympanic-petrosal Platmentioning

confidence: 99%

“…Van K am pen , 1905; Steh l in , 1912; V an der K l a a u w , 1931; Saban, 1956Saban, -57, 1963Saban, , 1975; L eG ros C l a r k , 1959; Van Valen, 1965]. Ontogenetic investigation, however, shows that there is strong reason to doubt that the 'annulus membrane' exists (or for that matter, has existed) in lemurs, at least as a structure separate from the membranous meatus or the mucosal lining of the tympanic cavity.…”

Section: Gross Features O F the Development O F The Ectotympanic-petrmentioning

confidence: 99%

Ontogeny of the Ectotympanic-Petrosal Plate Relationship in Strepsirhine Prosimians

MacPhee¹

1977

IJFP

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The two major groups of living strepsirhine prosimians (the lorises and lemurs) display two different forms of the ectotympanic-petrosal plate relationship (EPPR). Ontogenetically, the factors producing this difference primarily relate to (1) the degree of elaboration of the sutural tissues at the ectotympanic-petrosal plate interface and (2) the method of pneumatization of the petrosal bone. These two processes are, in all likelihood, the same ones which determined the EPPRs of fossil strepsirhines as well. The important theoretical point which emerges is that the transition from the intrabullar to the extrabullar condition of the ectotympanic (or vice versa) was probably effected partly or wholly in young rather than adult stages of ancestral strepsirhines.

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“…In this canal lies the internal carotid nerve (sym pathetic trunk) which had also entered the bulla through the carotid foramen alongside the internal carotid artery. Although other authors have mentioned the fact that the tympanic nerve (nerve of Jacobsen) entered the carotid foramen in Lemur [Saban, 1963[Saban, , 1975Szalay and K a t z , 1973] there is no report of the internal carotid nerve lying in the promontory canal in strep sirhines in particular or in interpretations of fossil primates in general.…”

mentioning

confidence: 99%

Middle Ear Morphology of Lemur variegatus

Conroy¹,

Wible

1978

IJFP

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The middle ear morphology of Lemur variegatus, a strepsirhine primate, is described. Although no promontory branch of the internal carotid artery appears, there is a well-developed ‘promontory canal’ containing a nerve trunk. This structure, which is previously undescribed in strepsirhines, is made up of the tympanic nerve and the internal carotid nerve. The implications of this discovery for paleontology, systematics, and future research are discussed.

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Structure of the Ear Region in Living and Subfossil Lemurs

Cited by 9 publications

References 6 publications

Internal carotid arterial canal size and scaling in Euarchonta: Re-assessing implications for arterial patency and phylogenetic relationships in early fossil primates

Internal carotid arterial canal size and scaling in Euarchonta: Re-assessing implications for arterial patency and phylogenetic relationships in early fossil primates

Ontogeny of the Ectotympanic-Petrosal Plate Relationship in Strepsirhine Prosimians

Middle Ear Morphology of Lemur variegatus

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