FIGURE 1. Stratigraphic section of John Day Basin showing where the described skull of Capacikala gradatus (JODA 621) was found. Dates according to Albright et al. (2008).
FIGURE 2. Skull of Capacikala gradatus, JODA 621, John Day Fossil Beds, Oregon in photographs and interpretive drawings. 2.1) Photo in dorsal view of the specimen, 2.2) photo of lateral view (mirror image), 2.3) photo in ventral view, and 2.4) photo in distal view of the specimen; Scale bar equals 1 cm; 2.5) drawing of the dorsal view, 2.6) drawing of the lateral view and 2.7) drawing of the ventral view.
aw – alisphenoidwing; bo – basioccipital; cf – crista facials; eam – external autidory meatus; f – frontal; hf – hypoglossal foramen; fo – foramen ovale; ifo – infraorbital foramen; imf – intermaxillary foramen; incf – incisive foramen; ip – interparietal; ipf – internal pterygoid fossa; j – jugal; m – mastoid; lf – lacerate foramen; mp – mastoid process; ms-bcf – masticatory-buccinator foramen; msp – masseter superfacialis process; mx – maxillary;
n – nasal; p – parietal; pal – palatine; pgf – postglenoid foramen; pfl – posterior lacerate foramen; pm – premaxillary; pp – paroccipital process; so – supraoccipital; sq – squamosum; tf – temporal foramen; ty – tympanic.
FIGURE 4. Photograph of the right mandible in lateral view 4.1) and interpretative drawings of the left mandible and dentition of Capacikala gradatus, JODA 621, John Day Fossil Beds, Oregon, in labial (4.2), and lingual (4.3) view. 4.3) dentition, p4-m3 sinister, in occlusal view (anterior is to the right). Abbreviations: as – angular shelf (masseter crest of Freye, 1959; linobl – linea obliquea; pf – pterygoid fossa. Scale bar equals 5 mm.
FIGURE 6. Comparative scatter diagram of the zygomatic width (zw) against the length of the skull of some fossil beavers (modified from Stefen 2010). Palaeocastor (Palaeoc.) sp. SDSM 4209, Capacikala gradatus (Capacik. grad.) JODA 621 and SDSM 5489, Capacikala parvus (Capacik. parvus) and "Capatanka" (Capat.) minor from Xu (1996, partially calculated from figure), Palaeocastor nebrascensis (Palaeoc. Nebrasc.) UCMP 114635 and "Capatanka" cankpeopi (Capat. cank.) LACM 22443., Palaeocastor (Palaeoc.) fossor, "Capatanka" (Capat.) magnus, Pseudopalaeocastor (Pseudopal.) barbouri, Euhapsis platyceps and E. ellicottae from Martin (1987).
FIGURE 7. Pterygoid region of a skull of Recent Castor fiber from the Senckenberg Natural History Collections Dresden to indicate some morphological features for which size and scale are irrelevant. 6.1) in ventral view and 6.2) in lateral view.
FIGURE 9. Schematic sketches of the fronto-parietal-sagittal crests of some specimens of Capacikala to show variations and similarities. The position of the orbita is only indicated not meant to give details on the form. 9.1) Capacikala parris, FAM 64552; 9.2) Capacikala sp. SDSM 53344; 9.3) SDSM 533515; 9.4) SDSM 5489; 9.5) Capacikala gradatus JODA 621. Abbreviations: orb – orbita; nc – nuchal crest.
FIGURE 10. Schematic sketches of the fronto-parietal-sagittal crests of some specimens of Capatanka. 10.1) Capatanka cankpeopi LACM 17692; 10.2) Capatanka sp. SDSM 53241; 10.3) SDSM 5672. Abbreviations as in Figure 9.
FIGURE 11. Schematic sketches of the fronto-parietal-sagittal crests of some specimens of Palaeocastor. 11.1) Palaeocastor wahlerti F:AM 64097; 11.2) Palaeocastor sp. SDSM 54209; 11.5) Palaeocastor nebrascensis UCMP 114635; Abbreviations as in Figure 9.