Boyer diss 2009 1046..
Boyer diss 2009 1046.. Boyer diss 2009 1046..
many cases the g4 groove actually intersects the g3 groove. The promontorium is flanked on its medial side by rostral and medial tympanic processes (Fig. 2.4: 20), which are abruptly broken off at their roots. There are three visible ridge-like bony projections (or septa) that rise from the tympanic processes to buttress the ballooning pars cochlearis. The most anterior of these is termed the second septum here (Fig. 2.4: s2) because it is medial to the “first septum” (Fig. 2.4: s1), which is more laterally positioned and obscured by matrix in this particular specimen (but visible with HRxCT). Note that terminology employed here differs from similar terminology used by Russell (1964) for some of these septa. Russell (1964: p.94, fig. 15) uses uses “S1” for s2, and “S2” for s1. One characteristic of g3, introduced above, is that it leads to the ventral apex of, or to the medial side of s2 (Fig. 2.4). The most posterior of the three visible septa houses the cochlear canaliculus (Fig. 2.4: cc), a tube that connects endocranial space above the inferior petrosal sinus to the spiral cochlea (MacPhee, 1981). In fairly complete specimens the ventral surface of this septum often is marked by a groove that ends medially and laterally in foramina (Fig. 2.4: 21, 22). This feature is visible on the left side of UALVP 46685, where it appears as a groove on the septum for the cc that ends laterally at a foramen on the promontorium. This groove and foramen represent the tympanic canaliculus. Between the s2 and the ridge over the cochlear canaliculus, is the third septum (Fig. 2.4: s3), which is oriented mediolaterally and is the smallest of the three. Posterolateral to the cochlear canaliculus, the remnants of yet another septum are visible on the right side of UALVP 46685. This is the “blister-like” sheet of bone (e.g., Szalay et al., 1987; also referred to as the “posterior septum” by MacPhee, 1981) that often stems from the promontorium medial to the fenestra cochleae and arches laterally 42
eneath it while also extending posteriorly to meet the posterior wall of the auditory bulla. The most significant aspect of this feature is that its ventral margin often marks the canal and/or course of the internal carotid plexus, which may include only nerves, but possibly also the internal carotid artery (Fig. 2.4: ps). Its presence and position demonstrate that the internal carotid plexus had an intratympanic, transpromontorial course (Fig. 2.4) and that it entered the tympanic cavity from a position posterior and slightly lateral to the promontorium, instead of medial to it. Digital extraction of the left petrosal allows visualization of the oval window, also called the aperture for fenestra vestibuli (Fig. 2.4: av), which measures about 1.17 mm by 0.60 mm in its diameters. This leads into the spiral cochlea measuring 15.60 mm in maximum length, after completing two and a half turns. The aperture for the round window, or fenestra cochleae (ac) is not visible in this specimen. The primary facial foramen is visible anterolateral to the fenestra vestibuli (Fig. 2.4: 23). It measures 1.07 mm by 0.44 mm. The s1 is visible, assisting in identification of more easily observable morphology (e.g., s2) as described above. The right promontorium is obscured everywhere except its medial side. The lateral, anterior, posterior and ventral aspects are mostly covered by a flattened plate of what appears to be bulla-forming bone and remnants of the ectotympanic (Figs. 2.1-3, 5: 24). The g4, a variably present groove, s2, s3, and cochlear canaliculus can be seen on the exposed medial surface (Fig. 2.5). Furthermore, the broken edge of the medial tympanic process reveals that it was comprised of two bony laminae (Fig. 2.5: 25, 26). This may indicate the presence of more than one bone (i.e., the bulla may not have been entirely or even partly petrosally derived). The presence of two distinct laminae 43
- Page 19 and 20: Craniodental material of Plesiadapi
- Page 21 and 22: Figure 2.25. MNHN CR 965 Plesiadapi
- Page 23 and 24: Figure 4.24. UM 87990 Plesiadapis c
- Page 25 and 26: Table List Chapter 2 Table 2.1. Num
- Page 27 and 28: Table 4.30. Caudal vertebrae measur
- Page 29 and 30: CHAPTER 1: INTRODUCTION Plesiadapif
- Page 31 and 32: primates, sharing many dental featu
- Page 33 and 34: were acquired. Specifically, the
- Page 35 and 36: of the plesiadapiform skeleton. Ext
- Page 37 and 38: Gervais, M.P., 1877. Enumération d
- Page 39 and 40: Szalay, F.S., 1972. Cranial morphol
- Page 41 and 42: CHAPTER 2: A REEVALUATION OF CRANIA
- Page 43 and 44: Information on the cranium of basal
- Page 45 and 46: petrosal bulla predicts that a sutu
- Page 47 and 48: History of descriptive study of ple
- Page 49 and 50: Gingerich (1971) rebutted Szalay (1
- Page 51 and 52: 9c, Gingerich (1976) labeled a groo
- Page 53 and 54: portion of the bulla medial to the
- Page 55 and 56: Bloch and Silcox (2006) described t
- Page 57 and 58: MATERIALS AND METHODS Material exam
- Page 59 and 60: whitening, dark and light areas on
- Page 61 and 62: SYSTEMATIC PALEONTOLOGY Class MAMMA
- Page 63 and 64: efore meeting a large, anteroposter
- Page 65 and 66: The canine is a simple, single-root
- Page 67 and 68: existence and/or nature of contacts
- Page 69: outlined. This includes description
- Page 73 and 74: y a pair of parallel grooves (Fig.
- Page 75 and 76: the skull (Fig. 2.1). The length of
- Page 77 and 78: margin clearly had a posteriorly pr
- Page 79 and 80: groove measures about 0.29 mm in di
- Page 81 and 82: 2.13: 50). The suture with the supr
- Page 83 and 84: preserved (Fig. 2.15: 55). In fact,
- Page 85 and 86: the posterior septum, a deeply inci
- Page 87 and 88: Plesiadapis tricuspidens MNHN CR 12
- Page 89 and 90: is roughly 2.8 mm long. Medial to t
- Page 91 and 92: is not convoluted like many other s
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- Page 95 and 96: two regions for the internal jugula
- Page 97 and 98: ventral to the sinuous suture (132)
- Page 99 and 100: provides measurements of these and
- Page 101 and 102: of the promontorium of the Pellouin
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- Page 107 and 108: canaliculus are present on the sept
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- Page 113 and 114: REFERENCES Beard, K.C., 1993. Phylo
- Page 115 and 116: Russell, D.E., 1959. Le crâne de P
- Page 117 and 118: TABLES Table 2.1. Numerical list of
- Page 119 and 120: 81 - Occipital/petrosal suture (Fig
eneath it while also extending posteriorly to meet the posterior wall of the auditory<br />
bulla. The most significant aspect of this feature is that its ventral margin often marks the<br />
canal and/or course of the internal carotid plexus, which may include only nerves, but<br />
possibly also the internal carotid artery (Fig. 2.4: ps). Its presence and position<br />
demonstrate that the internal carotid plexus had an intratympanic, transpromontorial<br />
course (Fig. 2.4) and that it entered the tympanic cavity from a position posterior and<br />
slightly lateral to the promontorium, instead of medial to it.<br />
Digital extraction of the left petrosal allows visualization of the oval window,<br />
also called the aperture for fenestra vestibuli (Fig. 2.4: av), which measures about 1.17<br />
mm by 0.60 mm in its diameters. This leads into the spiral cochlea measuring 15.60 mm<br />
in maximum length, after completing two and a half turns. The aperture for the round<br />
window, or fenestra cochleae (ac) is not visible in this specimen. The primary facial<br />
foramen is visible anterolateral to the fenestra vestibuli (Fig. 2.4: 23). It measures 1.07<br />
mm by 0.44 mm. The s1 is visible, assisting in identification of more easily observable<br />
morphology (e.g., s2) as described above.<br />
The right promontorium is obscured everywhere except its medial side. The<br />
lateral, anterior, posterior and ventral aspects are mostly covered by a flattened plate of<br />
what appears to be bulla-forming bone and remnants of the ectotympanic (Figs. 2.1-3, 5:<br />
24). The g4, a variably present groove, s2, s3, and cochlear canaliculus can be seen on<br />
the exposed medial surface (Fig. 2.5). Furthermore, the broken edge of the medial<br />
tympanic process reveals that it was comprised of two bony laminae (Fig. 2.5: 25, 26).<br />
This may indicate the presence of more than one bone (i.e., the bulla may not have been<br />
entirely or even partly petrosally derived). The presence of two distinct laminae<br />
43
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