10 



S.E. CHURCHILL AND T.W. HOLLIDAY 



the necks also lack the crests seen on the fifth ribs. The articular 

 tubercles are primarily interiorly directed and round in shape (right- 

 side 9.7 mm PD by 9.5 mm internal-external (IE) , left-side 9.4 mm 

 PD by 9.5 mm IE). The nonarticular tubercles are almost absent, 

 appearing as small dorsosuperior extensions of the articular facets. 

 The M. iliocostalis lines are not rugose nor marked. The attachments 

 for M. levator costae can be seen as crests on the superior edges of 

 the ribs running distally from the level of the tubercles and blending 

 into the M. iliocostalis lines. The subcostal grooves are clear and 

 distinct. The head/neck axis to shaft axis angle is roughly 135° in 

 both ribs. 



R1B7 



The right seventh rib is preserved as a 181.1 mm-long fragment of 

 the body, from somewhere distal of the posterior angle to just distal 

 of the anterior angle. Judging from the size and curvature of the left 

 side antimere, the proximal break occurred right at the distal end of 

 the posterior angle. The left-side rib is represented by a 185.0 mm 

 long-fragment, complete from the head to the region of the anterior 

 angle. 



The secondary centre of ossification for the head of the left rib is 

 unfused and missing. The neck is short and has a tubercle and crest 

 on its superior surface for the superior costotransverse ligament. The 

 neck has a large foramen or pit (plugged with matrix) on its dorsal 

 surface. The M. levator costae crest is pronounced. The articular 

 facet is dorsoinferiorly directed and oval in shape (10.8 mm PD by 

 8.4 mm IE). The nonarticular tubercle is poorly defined but is larger 

 than that of the 6th rib. The M. iliocostalis line is non-rugose and 

 poorly defined. On both sides the proximal bodies are quite thick and 

 form a 'roof over the subcostal groove along the proximal shaft. The 

 subcostal grooves are very clearly defined along the proximal por- 

 tions of the shafts. In the left-side rib, the head/neck axis to body axis 

 angle is strong (approximately 109°). 



Rib 8 



The right eighth rib is preserved as a 198 mm-long fragment, 

 complete from the head to the area of the anterior angle. The left rib 

 is preserved as a 190.3-mm long fragment of the body, retaining a 

 small portion of the nonarticular tubercle proximally. Distally the 

 left-side rib is broken somewhere proximal of the anterior angle. 



On the right rib the head is unfused and missing. The neck is short 

 and has a tubercle and crest on its superior surface for the superior 

 costotransverse ligament. This crest is continuous with the insertion 

 of M. levator costae and blends with the superior portion of the M. 

 iliocostalis line distally. The same morphology can be seen in the 

 left-side rib from the area of the M. levator costae insertion (the most 

 proximally preserved portion of the shaft) down to the M. iliocostalis 

 line. The inferior surface of the right-side neck also has a clearly 

 defined crest, perhaps reflecting the attachment of an expanded 

 accessory ligament from the head and neck of the subjacent rib 

 (Williams & Warwick, 1980) or a distal extension of the radiate 



Table 8 Dimensions (mm) of ribs 8-11. 





R8 



L8 



R9 



L9 



Rll 



Lll 



Neck length 1 



(26.7) 2 



_ 



(22.5) 3 



(23.1)- 



_ 



_ 



Proximal thickness (M-2) 



10.2 



9.3 



8.4 



8.2 



- 



- 



Proximal height (M-l) 



9.8 



9.2 



9.7 



9.1 



- 



- 



Shaft thickness 3 



- 



10.6 



- 



7.9 



6.9 



6.3 



Shaft height 3 



- 



11.4 



- 



15.3 



13.2 



13.8 



'Distance from the middle of the head to the middle of the articular tubercle. 

 -Head unfused. measurement taken from middle of epiphyseal surface for head. 

 'Rib thickness (internal-external diameter, measured in the plane of rib curvature) 

 and height (supero-inferior diameter, taken perpendicular to the plane of curvature of 

 the rib) at the point where the M, iliocostalis line meets the inferior edge of the rib. 



ligament. The neck has a foramen or pit on the dorsal surface just 

 proximal to the articular facet. The articular facet is oval (11.6 mm 

 PD by 9.3 mm IE) and is primarily inferiorly directed. The 

 nonarticular tubercle is poorly defined and blends with the proximal 

 end of the M. iliocostalis line. The M. iliocostalis lines are non- 

 rugose and poorly defined on both ribs. Small, mildly rugose 

 depressed areas can be seen on the superior margins of the shafts just 

 distal to the M. iliocostalis lines, likely marking the proximal extent 

 of the insertion of the intercostal muscles. The subcostal grooves are 

 very clear along the proximal halves of the ribs. The head/neck axis 

 to body axis angle of the right-side rib is 122°. 



Rib 9 



The right ninth rib is a 79.6 mm-long fragment of the proximal end, 

 complete from the head to the region of the posterior angle. The left 

 rib is preserved as a 150.5 mm-long fragment, complete from the 

 head to somewhere below midshaft. 



The centres of ossification for the heads are unfused and missing. 

 The necks are relatively short. In the right-side rib, a small tubercle 

 is evident on the superior surface of the neck, perhaps reflecting an 

 attachment for an accessory ligament that ran superiorly to the crest 

 on the inferior surface of the neck of the right eighth rib. The crests 

 for M. levator costae are clearly defined on both ribs. The articular 

 facets are oval shaped (measuring 8.9 mm PD by 7.7 mm IE on the 

 right, 8.9 mm PD by 8.0 mm IE on the left) and are inferodorsally 

 directed. The nonarticular tubercles arise from the articular tubercles 

 and are relatively small. The M. iliocostalis lines are not pronounced. 

 The costal grooves are wide supero-inferiorly and shallow. The 

 head/neck axis to shaft axis angle is 116° in both ribs. 



Rib 11 



The right eleventh rib is represented by a 130.5 mm-long fragment, 

 complete from the head to somewhere near the anterior angle. The 

 left-side rib is preserved as a 102.5 mm-long fragment, complete 

 from the head to 37 mm below the posterior angle. The shaft of the 

 left rib is eroded and damaged. 



The heads are unfused and missing on both sides. The ribs present 

 neither articular nor nonarticular tubercles, but crests for the cos- 

 totransverse ligaments are visible on the superior margins of the 

 proximal bodies. Narrow, oval insertion scars for the intercostal 

 muscles are visible on both the inferior and superior edges at the 

 posterior angle. The M. iliocostalis lines are indistinct, but bulging 

 tubercles are visible at the posterior angle in each rib for the attach- 

 ment of this muscle. 



Rib 12 



The right twelfth rib is complete, and has a total length of 96.6 mm. 

 The area of the internal intercostal muscle attachment on the superior 

 edge is eroded away, but otherwise the bone is well preserved. 



The head appears to be unfused. The rib has a clear crest on the 

 superior surface of the neck for the costotransverse ligament. There 

 is also a sulcus on the inferior edge of the internal surface of the 

 proximal shaft for M. quadratus lumborum. The diaphragm attach- 

 ment is indistinct. There is a long (19 mm), narrow scar on the 

 inferior edge of the distal shaft forM serratus posterior inferior, and 

 on the superior external surface some rugosity is visible that may 

 represent the attachment site of M. latissimus dorsi. The right twelfth 

 rib is 95.9 mm long (M-4: Martin, 1928) and has an external arc 

 length (M-3: Martin, 1928) of 54 mm. 



Unidentified shaft fragment 



This is a 58.2 mm-long fragment of the distal end of a rib body, 

 including the sternal end. The subcostal groove is not preserved, and 

 thus the side cannot be determined. The fragment is somewhat 

 damaged and has some areas of plaster reconstruction. The supero- 



