Fig 1.
Schematic of measurements used to evaluate giraffid cervical vertebrae.
(A) Drawing of the C3 vertebra of Okapia johnstoni in lateral view. (B) Drawing of the C3 vertebra of Okapia johnstoni in dorsal view. (C) Drawing of the C3 vertebra of Giraffa camelopardalis in lateral view. Lines in red represent measurements taken to quantify serial morphologic features. 1- centrum length, 2- maximum length, 3- minimum width, 4- spinous process height, 5- Length of spinous process at base, 6- length of spinous process, 7- angle of spinous process, 8- angle of ventral tubercle, 9- length:width of cranial articular process.
Fig 2.
The atlas and axis of the okapi and giraffe.
(A) Okapia johnstoni (AMNH 51197) atlas in dorsal view. (B) Okapia johnstoni axis in ventral view. The scale bar corresponds to 100 mm. (C) Giraffa camelopardalis (AMNH 82001) atlas in dorsal view. (D) Giraffa camelopardalis axis in ventral view. The scale bar corresponds to 200 mm.
Fig 3.
Anatomic Terminology of the giraffe and okapi vertebrae.
(A) Labeled C3 vertebra of Okapia johnstoni (AMNH 51197). (B) Labeled C3 vertebra of Giraffa camelopardalis (AMNH 82001). The anterior arch is drawn in green; O. johnstoni has a continuous arch, and G. camelopardalis has an interrupted arch. The post-tubercular ridge of O. johnstoni is drawn in blue. 1- cranial bulge, 2- cranial articular process, 3- ventral tubercle, 4- cranial opening of the foramen transversarium, 5- caudal opening of the foramen transversarium, 6- spinous process, 7- transverse process, 8- intertubercular plate, 9- dorsal tubercle, 9’-accessory dorsal tubercle, 10- caudal articular facet, 11- post-tubercular ridge, 12- ventral ridge, 13- pars interarticularis, 14- caudal extremity, 15- lamina. [18].
Fig 4.
The sixth cervical vertebra of the okapi and giraffe.
(A) Okapia johnstoni (AMNH 51197) C6 in lateral view. (B) Okapia johnstoni C5 in ventral view. The scale bar corresponds to 100 mm. (C) Giraffa camelopardalis (AMNH 82001) C6 in lateral view. (D) Giraffa camelopardalis C6 in ventral view. The scale bar corresponds to 100 mm.
Table 1.
Selected measurements of Giraffa camelopardalis C1-T1 vertebrae.
Table 2.
Selected measurements of Okapia johnstoni C1-T1 vertebrae.
Table 3.
Coefficient of variation of C3-C6 for eleven measurements in G. camelopardalis and O. johnstoni.
Fig 5.
Complete articulated necks of the giraffe and the okapi.
(A) Lateral view of C1-T2 of Giraffa camelopardalis (AMNH 82001). (B) Lateral view of C1-T2 of Okapia johnstoni (NMNH 399337). The black line demarcates the actual length of the O. johnstoni neck in relation to that of G. camelopardalis. The scale bar corresponds to 200 mm.
Fig 6.
Lateral views of the okapi and giraffe vertebrae showing morphologic characters.
(A) Lateral view of Okapia johnstoni C5 vertebra. (B) Lateral view of Okapia johnstoni C6 vertebra. (C) Lateral view of Okapia johnstoni C7 vertebra. (D) Lateral view of Giraffa camelopardalis C5 vertebra. (E) Lateral view of Giraffa camelopardalis C6 vertebra. (F) Lateral view of Giraffa camelopardalis C7 vertebra. The outline of the spinous process is drawn in purple, the cranial articular process is highlighted in orange, the position of the dorsal tubercle is marked in blue, and the orientation of the ventral tubercle is drawn in green. The Okapia johnstoni C6 and C7 vertebrae lack a ventral tubercle (typical of ruminants). The characters drawn suggest homogenization of the G. camelopardalis cervical vertebrae, relative to O. johnstoni.
Fig 7.
Ventral views of okapi and giraffe vertebrae showing morphologic characters.
(A) Ventral view of Okapia johnstoni C5 vertebra. (B) Ventral view of Okapia johnstoni C6 vertebra. (C) Ventral view of Okapia johnstoni C7 vertebra. (D) Ventral view of Giraffa camelopardalis C5 vertebra. (E) Ventral view of Giraffa camelopardalis C6 vertebra. (F) Ventral view of Giraffa camelopardalis C7 vertebra. The shape of the ventral vertebral body and intertubercular plate is shown in blue, and the ventral ridge, when present, is drawn in green.