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Volume 27.1
January–April 2024
Full table of contents
ISSN: 1094-8074, web version;
1935-3952, print version
Recent Research Articles
See all articles in 27.1 January-April 2024
See all articles in 26.3 September-December 2023
See all articles in 26.2 May-August 2023
See all articles in 26.1 January-April 2023
Clara Stefen
Senckenberg Naturhistorische Sammlungen Dresden
Museum of Zoology
Königsbrücker Landstrasse 159
01109 Dresden
Germany
Clara.Stefen@senckenberg.de
Clara Stefen is curator of mammals at the Senckenberg Natural History Collections Dresden and works on recent and fossil mammals. Part of my research is focused on Castoridae, others on Carnivora, generally on Morphology, Taxonomy and Evolution but also on local faunistic and ecological aspects.
TABLE 1. Overview on some systematic assignments of castorid taxa by different authors on the level of genera only. In blue those genera that are assigned to the Palaeocastorinae by Korth (1994). Flynn and Jacobs (2008) refer to the North American Fauna only.
Stirton 1935 |
Simpson 1945 |
Korth 1994 |
McKenna & Bell 1997 |
Korth 2001 |
Rybczynski 2007 |
Flynn & Jacobs 2008 |
|
semi flattened incisors |
Uncertain subfam. |
Agnotocastorinae |
basal castorids |
||||
Agnotocastor |
Agnotocastor |
Agnotocastorini |
Agnotocastor |
||||
Palaeocastor |
Hystricops |
Agnotocastor |
Agnotocastor |
Neatocastor |
|||
Euhapsis |
Neatocastor |
Anchitheriomys |
Oligotheriomys |
||||
Chalicomys |
Hystricops |
Anchitheriomys |
|||||
Castor |
Anchiteriomyini |
||||||
Convex incisors |
Anchitheriomys |
||||||
Steneofiber |
Propalaeocastor |
||||||
Monosaulax |
Oligotheriomys |
||||||
Eucastor |
Castorinae |
Castorinae |
Castorinae |
Castorinae |
Castorinae |
Castorinae |
|
Dipoides |
Agnotocastor |
Castor |
Agnotocastor |
Castor |
Castor |
Castor |
|
Castoroides |
Palaeocastor |
Capacikalini |
Chalicomys |
Hystricops |
|||
Amblycastor |
Euhapsis |
Capacikala |
Steneofiber |
Sinocastor |
|||
Hystricops |
Chalicomys |
Pseudopalaeocastor |
Zamolxifiber |
Steneofiber |
|||
Trogontherium |
Sinocastor |
Castorini |
Romanofiber |
||||
Conodontes |
Castor |
Euhapsina |
Schreuderia |
||||
Euhapsis |
|||||||
Fossorcastor |
|||||||
Castorina |
|||||||
Propalaeocastor |
|||||||
Chalicomys |
|||||||
Palaeocastor |
|||||||
Hystricops |
|||||||
Castor |
|||||||
Castoroidinae |
Castoroidinae |
Castoroidinae |
Castoroidinae |
Castoroidinae |
Castoroidinae |
||
Steneofiber |
Monosaulax |
Steneofiber |
Castoroidini |
Dipoides |
Euroxenomys |
||
Monosaulax |
Eucastor |
Neatocastor |
Monosaulax |
Eucastor |
Monosaulax |
||
Eucastor |
Dipoides |
Asiacastor |
Eucastor |
Trogontherium |
Eucastor |
||
Dipoides |
Procastoroides |
Youngofiber |
Dipoides |
Euroxenomys |
Microdipoides |
||
Procastoroides |
Castoroides |
Trogontherium |
Castoroides |
Procastoroides |
Dipoides |
||
Castoroides |
Eucastor |
Procastoroides |
Castoroides |
Procastoroides |
|||
Trogontherium |
Schreuderia |
Trogontheriini |
|||||
Amblycastor |
Dipoides |
Trogontherium |
|||||
Boreofiber |
Boreofiber |
||||||
Romanofiber |
Euroxenomys |
||||||
Zamolxifiber |
Youngofiber |
||||||
Procastoroides |
Asiacastor |
||||||
Castoroides |
|||||||
Paradipoides |
|||||||
Palaeocastorinae |
Palaeocastorinae |
Palaeocastorinae |
Palaeocastorinae |
||||
Palaeocastorini |
Palaeocastor |
Euhapsis |
Palaeocastor |
||||
Palaeocastor |
Capacikala |
Fossorcastor |
Capacikala |
||||
Capatanka |
Pesudopalaeocastor |
Pseudopalaeo-castor |
Pseudopalaeocastor |
||||
Capacikalini |
Euhapsis |
Palaeocastor |
Euhapsis |
||||
Capacikala |
Fossorcastor |
Fossorcastor |
|||||
Pseudopalaeocastor |
|||||||
Euhapsini |
|||||||
Euhapsis |
|||||||
Fossorocastor |
|||||||
ungrouped |
|||||||
Migmacastor |
|||||||
Agnotocastor |
|||||||
Eutypomys |
|||||||
Priusaulax |
Table 2. Measurements of the skull and mandible of Capacikalagradatus from the John Day fossil Beds in millimeters.
greatest skull length |
59.93 |
zygomatic width (estimated from preserved right side) |
48.00 |
length of right zygomatic arch |
24.04 |
width of skull at external auditory meatus |
30.43 |
distal height of skull (condyle - sagittal crest) |
19.87 |
height of skull at auditory bullae |
23.45 |
angle occipital plane to base of skull |
90° |
height of skull at tooth row (at P4) |
22.97 |
width across condyles |
12.52 |
maximal width of the nasals |
9.25 |
maximal width of snout |
12.39 |
height of snout |
12.55 |
diastema |
19.34 |
length of incisive foramen |
5.24 |
a second foramen in front of incisive foramen present? |
yes |
form of infraorbital foramen |
slitlike |
height of infraorbital foramen |
3.03 |
infraorbital constriction |
8.66 |
width of parietale behind orbitae |
22.62 |
width of postzygomatic constriction |
25.05 |
length of right tooth row |
11.25 |
length of left tooth row |
11.34 |
distance P4/P4 |
4.31 |
distance M3/M3 |
7.2 |
postzygomatic skull length |
14.58 |
length of bulla |
11.46 |
tooth row visible trough orbital constriction |
yes |
rugosities on parietale |
yes |
masseter superficialis process prominent |
no |
masseter superficialis process clearly bordered |
no |
form of crista facialis in lateral view |
straight/diagonally |
form of crista facialis or rather infraorbital foramen in frontal view |
convex, diagonally |
lacrimal with dorsal part ? |
no |
Table 3. Measurements of the teeth of Capacikalagradatus JODA 621 in millimeters. Length of tooth rows: mandibular right 12.65 mm, mandibular left 12.72 mm, maxillar right 12.21 mm and maxillar left 11.27 mm.
Tooth |
Length |
Width |
p4 left |
4.27 |
3.33 |
m1 left |
2.91 |
3.52 |
m2 left |
2.92 |
3.44 |
m3 left |
2.81 |
2.75 |
p4 right |
4.13 |
3.32 |
m1 right |
2.81 |
3.6 |
m2 right |
3.08 |
3.47 |
m3 right |
2.72 |
2.79 |
P4 left |
3.43 |
3.81 |
M1 left |
2.92 |
3.56 |
M2 left |
2.65 |
3.44 |
M3 left |
2.41 |
2.8 |
P4 right |
3.57 |
4.11 |
M1 right |
3.11 |
3.9 |
M2 right |
2.89 |
3.56 |
M3 right |
2.28 |
2.92 |
Table 4. Some values of procumbency angles of the upper incisors of some castorid taxa measured in accordance to the method of Lessa and Thaeler (1989) either from material at hand or the cited literature. Taxonomic assignments as in the cited literature. MTD – Senckenberg Natural History Collections Dresden, Museum für Tierkunde, UCMP – University of California Berkeley Museum of Paleontology.
Taxon |
Literature |
procumbency angle |
Castoroides ohioensis |
cast, MTD |
63° |
Capatanka magnus |
Martin, 1987, fig. 2 |
69° |
Monosaulax tedi |
Korth, 1999, fig. 1 |
70° |
Euhapsis breugerorum |
Samuels & Van Valkenburgh, 2009 |
80° |
Euhapsis platyceps |
Samuels & Van Valkenburgh, 2009 |
82° |
Castor fiber |
average of 10 specimens, MTD |
88° |
Castor canadensis |
Thomas, 1916 |
90° |
Palaeocastor simplicidens |
Samuels & Van Valkenburgh, 2009 |
90° |
Capacikala gradatus |
JODA 621, cast |
95° |
Palaeocastor fossor |
Martin 1987, fig. 2 |
95° |
Capatanka cankpeopi |
McDonald, 1963 |
99° |
Palaeocastor fossor |
Samuels & Van Valkenburgh, 2009 |
102° |
Dipoides tanneri |
Korth, 2007, fig. 8 |
103° |
Monosaulax pansus |
Stefen, 2001 |
110° |
Palaeocastor nebrascensis |
UCMP 114635 |
113° |
Palaeocastor magnus |
Samuels & Van Valkenburgh, 2009 |
114° |
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.
Abbreviations:
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 3. Skull of Capacikala gradatus, JODA 621 in frontal view with left infraorbital foramen (iof). Scale bar equals 5 mm.
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 5. Possible phylogeny of selected castorid taxa as illustrated by neighbour joining method.
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 8. Some cranial material assigned to Capacikala sp. 8.1) SDSM 55108, 8.2) SDSM 5489, 8.3) & 8.4) LACM 17435 in dorsal and ventral view, respectively. Scale bar = 1 cm.
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.
APPENDIX 1
Photograph of the locality accompanying the field notes. Archive of the John Day National Park. Curtesy of Joshua X. Samuels, JODA.
APPENDIX 2
List of taxa in alphabetic order and character matrix used for the phylogenetic analysis. The characters are derived from own observations (partially from Stefen, 2005, Stefen and Moers, 2008) and the relevant literature (Barbour and Schultz, 1937; Korth and Emry, 1997; Korth, 2001; MacDonald, 1963; Martin, 1987; Mörs and Hulbert, 2010; Moore, 1890a, b; Peterson, 1905; Rybzynski et al., 2010; Schreuder, 1929; Stirton, 1934, 1935, 1965; Xu, 1996) (available in PDF format).
APPENDIX 3
List and explanation of characters used for the phylogenetic analysis.
1 dentition: 0 non-beaver pattern; 1 beaver pattern
2 hypsodonty: 0 teeth basically brachydont; 1 teeth subhypsodont; 2 clearly hypsodont, root is hardly ever formed
3 incisor inf. frontal face: 0 clearly convex; well rounded; 1 slightly convex; 1 clearly flat
4 incisor sup. Frontal face: 0 clearly convex; well rounded; 1 slightly convex; 1 clearly flat
5 incisor inf. enamel: 0 smooth; 1 clearly striated; 2 faintly striated
6 incisor sup enamel: 0 smooth; 1 clearly striated; 2 faintly striated
7 form and curvature of lower incisor tip: 0 chisel shaped; 1 pointed
8 form and curvature of upper incisor tip: 0 chisel shaped; 1 pointed
Characters of the skull
9 masseter arrangement: 0 non sciuromorph masseter arrangement ; 1 sciuromorph masseter arrangement
10 skull shape measured: 0 narrow (length/width approximately 1.5) ; 1 intermediate (length/width approximately 1.3) ; 2 broad (length/Width approximately 1.2 ) ; 3 broadest (length/Width approximately 1.0)
11 skull shape appearance: 0 skull longer than wide; 1 skull approximately square, nearly as long as wide (width at zygomatic arch); 2 skull wider than long
12 position of infraorbital foramen: 0 low, in ventral third of snout; 1 approximately in the middle of the snout height; 2 high, in the upper third of the snout height
13 form of infraorbital foramen in frontal view: 0 oval, geometrical; 1 tearshaped; 2 slitlike (markedly straight sides); 3 other form
14 course of infroaorbital canal: 0 – straight; 1 – not straight
15 position of masseter superfacials process: 0 – ventral to slightly posterior to infraorbital foramen; 1 anterior to infraorbital foramen; 2 not applicable
16 course of crista facialis (masseter ridge) in lateral view: 0 straight; 1 slightly curved; 2 "s"-shaped;
17 relative distance of premaxillary-maxillary suture to crista facialis masseter: 0 close; 1 well anterior
18 course of premaxillary-maxillary: 0 more or less straight dorso-ventrally; 1 in a marked angle not relatively straight dorso-ventrally
19 infraorbital in relation to root of zygomatic arch: 0 posterior (still level to part of zygomatic root though; 1 ventral to it; 2 anterior to it (to the most antrior part of the zyg root)
20 connection between jugal and lacrimal: 0 yes; 1 no
21 jugal extension on zygomatic arch: 0 jugal extending upwards up to dorsal rim of orbita, meeting fronto-maxillar suture; 1 jugal only extending to about half way up the maxillar component of the zygomatic arch; 2 jugal extending upwards to less than one third of the maxillar component of the zygomatic arch
22 dorsal component of lacrimal: 0 yes; 1 no
23 position of orbital constricion in relation to length of skull: 1 clearly in anterior part of skull length; 0 approx. in the middle of skull length; 2 clearly in posterior skull length
24 angle of occipital plane to a plane extended from the base of the skull: 0 about 90°; 1 less than 90 ° (exoccipital plane bending anteriorly); 2 more than 90 ° (exoccipital plane bending posteriorly)
25 fossa occipitalis: 0 absent; 1 present
26 rugosities on parietale/interparietale: 0 no (or very few); 1 yes, marked
27 groove dorsal to incisor in lateral view: 0 absent; 1 partial; 2 complete
28 divergence of tooth rows, ratio of distance between M3s to distance between P4s: 0 parallel; 1 slightly diverging (up to 1.7); 2 diverging more strongly 1.7 – 2.499; 3 larger than 2.5; 4 larger than 4
29 distal palatal termination: 1 at level of M3s; 2 at level of M2s; 0 at level of post M3s
30 Development of crest at posterior sagittal-lambdoidal area: 0 undeveloped; 1 well developed
31 Form of fronto-parietal crest: 0 frontal crest meet anterior of interorbital constriction and form 1 crest; 1 frontal crest meet at interorbital constriction to form 1 crest; 2 frontal crest meet posterior of interorbital constriction to form 1 crest; 3 frontal crest never meet
32 Formation of fronto-parietal crest: 0 – crest form one narrow crest when they meet; 1 crest remains broad when they meet
33 form of nasals: 0 maximum length/width greater than 2.5; 1 maximum length/width smaller than 2.0; 2 between 2.0 and 2.5
34 nasal form: 0 broader anterior than posterior; 1 distal broader than anterior (<); 2 - broadest in approximately the middle of the nasal; 3 – of about equal width throughout
35 position of caudal end of nasals: 0 distal of complete root of zygomatic arch; 1 approximately above root of zygomatic arch; 2 anterior to root of zygomatic arch
36 interpremaxillary foramen: 0 absent; 1 present
37 distal ending of the lower incisor: 0 lingual, at least no blub on labial side of mandible; 1 a slight blub on labial side of mandible; 2 a marked blub on labial side of mandible
38 curvature of premaxillary-maxillary in the diastema: 0 little, nearly straight; 1 curved
2 very strongly curved
39 ratio diastema to tooth row: 0: 0 > 1.1; 1 0.91-1.09; 2 < 0.9
40 intersection of premaxillary-maxillary suture and incisive foramen: 0 posterior to foramen; 1 really intersecting foramen
41 relation of depth of skull at bulla and at tooth row: 0 bulla and tooth row about same ventral depth; 1 bulla extending further ventral than tooth row; 2 tooth row more ventral than bulla
42 ratio of maximum width of nasals versus maximum width of snout: 0 greater than 0.85; 1 between 0.80-0.65; 2 smaller than 0.55
43 relation of length of incisive foramen to diastema: 0 0,1; 1 0,11-0,4; 2 0,41-0,6; 3 >0,61
44 position of the incisive foramen: 0 about in the middle of the diastema; 1 position more caudally; 2 position more anterior
45 presence of maxillar/palatal grooves: 0 none; 1 from incisive foramen to anterior palatal foramen; 2 only partial grooves directly posterior to incisive f; 3 only in front of anterior palatal foramen
46 Location of anterior palatal foramina: 0 within palatal bone; 1 not completely in palatal bone; 2 completely in maxillary bone
47 tip of incisor in relation to tooth row: 0 line extending from occlusal surface of cheek teeth approximately level with tip of incisor; 1 tip of incisor well above this line; 2 tip of incisor well below this line
48 presence of dp3/dP3 known: 0 yes; 1 no
49 extension of postglenoid constriction: 0 about equal in width to snout; 1 broader than snout; 2 at least twice as broad than snout; 3 postglenoid constriction narrower than snout
50 appearance of the bullae: 0 unconspicious; 1 well rounded and globose; 2 extremely small in relation to the skull size
51 presence of temporal foramen: 0 absent; 1 single; 2 multiple
52 auditory tube: 0 absent; 1 present
53 direction of the external auditory meat: 0 lateral; 1 lateral and dorsal; lateral and ventral
54 presence of interparietal: 0 present; 1 absent or fused
55 foramen ovale: 0 confluent with foramen lacerum; 1 separate
56 spehnopalatine foramen: 0 small; 1 mittel; 2 large;
57 masticatory and buccinator foramen: 0 separate; 1 conjunct;2 absent
58 amxillary alisphenoid contact (Rybc 18): 0 absent; 1 posterior to M3; 2 dorsal to M3; 3 dorsal to M2/M3
59 lateral pterygoid plate (proportion of alisphenoid in lateral view of skull): 0 not clear, small; 1 clear like Cator; 2 enlarged
60 Hamulus pertygoideus (or internal pt. process): 0 not visible; 1 small; 2 large (like in Paramys)
61 alisphenoid part of pterygoid fossa: 0 small to non marked; 1 up to half length to bulla
2 extended to bulla (like in Joda specimen)
62 a angle of interorbital constriction (angle between frontale and parietale at interorbital constriction): 0 about 110-145°; 1 about 150-180°; 2 ca 90-110°
63 form of interorbital constriction: 0 hourglass, cranium (parietale in the orbit) well rounded; 1 gross concave (like in recent Castor); 2 nearly, straight, only little interorbital constriction
Mandible
64 chin process or mandible digastric eminence: 0 chin process absent; 1 chin process clearly present
65 course of angular shelf (ventral rim of angular process): 0 extending in horizontal elongation of mandibular ramus; 1 extending upwards in an angle to the ventral rim of the mandibular ramus; 2 extending downwards in extension to the ventral rim of the mandibular ramus
66 course of ventral rim of mandibular ramus : 0 about in horizontal line; 1 clearly bending upwards; 2 clearly bending downwards
67 orientation of angular shelf: 0 flat, main surface only visible in ventral view; 1 tilting laterally (part of ventral surface is visible in lateral view)
68 posterior view of mandible: 0 condyle, coronid and angular process aligned; 1 condyle, coronid and angular process alternating – usually coronoid and angular procesi in line; 2 condyle, coronoid and angular aligned
69 position of mental foramen: 0 anterior to p4; 1 ventral to anterior rim of p4; 2 posterior to anterior rim of p4; 3 none
70 tip of mandibular incisor in relation to tooth row: 0 line extending from occlusal surface of cheek teeth approximately level with tip of incisor; 1 tip of incisor well above this line; 2 tip of incisor well below this line
71 course of mandibular tooth row: 0 about horizontal and parallel to horizontal course of mandibular ramus; 1 tilted to horizontal course of mandibular ramus
72 proximal end of mandibular incisor: 0 about level with tooth row; 1 above tooth row; 2 below tooth row
73 bulb at posterior end of incisor: 0 no; 1 yes
74 anterior rim of mandibular ramus: 0 crossing m3; 1 crossing m2; 2 crossing m1 or p4; 3 distal to m3
75 ratio mandibular diastema to tooth row: 0: 0 > 1.1; 1 = 0.91-1.09; 2 < 0.9
76 groove between ventral rim of mandible and angular process: 0 yes; 1 no
Cranial Morphology of the Oligocene beaver Capacikala gradatus from the John Day Basin and comments on the genus
Plain Language Abstract
In this paper the cranial morphology of the small Oligocene beaver Capacikala gradatus is described on the basis of a well preserved, nearly complete skull and partial mandibles from the John Day Formation, John Day Fossil Beds, Oregon, USA. Even though there is more material – most of it however, fragmentary – that is referred to this species, the skull is of very good preservation and therefore worth to be described in detail. It is also the only skull that can be well dated as it was found between dated marker beds, so that it can be no older than 28.7 Ma, nor younger than 27.89 Ma. The skull is described, illustrated and relevant measurements given. The morphological features of the skull are compared to Palaeocastor and recent Castor.
The genus Capacikala had been named 50 years ago (MacDonald, 1963), it is still not well understood. The diagnostic features given by several authors are discussed with the current skull. There are some similarities and some discrepancies. A revision of features diagnostic for the Capacikala and Palaeocastor is intended. But, the scope of the paper does not allow a review of both genera in total. The material of Palaeocastor is too diverse for that.
A phylogenetic analysis with few selected castorid species was performed, but resulted in poorly supported trees. It only shoed the closeness of the described specimen to other material referred to Capacikala and its nesting with palaeocastorine beavers. A complete revision of beaver phylogeny and of the characters used is beyond the scope of the paper.
Resumen en Español
Morfología craneal del castor oligoceno Capacikala gradatus de la Cuenca John Day y comentarios sobre el género
La morfología craneal del pequeño castor oligoceno Capacikala gradatus se describe a partir de un cráneo casi completo y bien conservado y de mandíbulas parciales de los John Day Fossil Beds de la Formación John Day, Oregón, Estados Unidos de América. Se describe aquí en detalle el único cráneo casi completo conocido hasta ahora de la misma zona que el espécimen tipo. Esto es especialmente apropiado ya que el espécimen tipo proviene de una localidad desconocida dentro de la Formación John Day y corresponde solo a un cráneo fragmentario. El espécimen ahora descrito se encontró entre niveles datados, de modo que no puede ser más antiguo de 28,7 Ma, ni más reciente de 27,89 Ma. Aunque Capacikala fue descrito hace 50 años (MacDonald, 1963), no es bien conocido. Las comparaciones morfológicas se hacen teniendo en cuenta otros ejemplares citados o ilustrados de Capacikala, Palaeocastor y el actual Castor; se han observado similitudes y diferencias respecto a ambos géneros. El hallazgo del cráneo se discute con respecto a la descripción de los géneros Capacikala y Palaeocastor, y algunos caracteres son revisados. Se realizó un análisis filogenético con unas pocas especies seleccionadas de castóridos, pero se obtuvieron árboles poco sustentados. Sin embargo, una revisión completa de la filogenia de los castóridos y de los caracteres utilizados está más allá del alcance del presente estudio.
PALABRAS CLAVE: Castoridae; Palaeocastorinae; cráneo; Terciario
Traducción: Enrique Peñalver
Résumé en Français
Morphologie crânienne du castor de l'Oligocène Capacikala gradatus du bassin de John Day et commentaires sur le genre
La morphologie crânienne du petit castor de l'Oligocène Capacikala gradatus est décrite sur la base d'un crâne bien conservé et presque complet et des mandibules partielles de la Formation de John Day, John Day Fossil Beds, Oregon, Etats-Unis. Le seul crâne presque complet connu à ce jour dans la même région que le spécimen type est décrit ici en détail. Ceci est particulièrement approprié parce que le spécimen type vient d'une localité inconnue dans la Formation de John Day et est seulement un crâne fragmentaire. Le spécimen nouvellement décrit a été trouvé entre des lits marqueurs datés, de sorte qu'il ne peut pas être plus vieux que 28,7 Ma, ni plus jeune que 27,89 Ma. Bien que Capacikala ait été nommé il y a 50 ans (MacDonald, 1963), il n'est pas encore bien connu. Des comparaisons morphologiques sont apportées à d'autres spécimens mentionnés ou illustrés de Capacikala, Palaeocastor et Castor récent; il y a des similitudes et des différences avec chaque genre. La découverte du crâne est discutée en comparant avec la description des genres Capacikala et Palaeocastor et certains caractères sont révisés. Une analyse phylogénétique avec quelques espèces de castoride sélectionnés a été réalisée, mais a donné lieu à des arbres mal supportés. Cependant, une révision complète de la phylogénie des castors et des caractères utilisés est au-delà de la portée du papier.
MOTS CLÉS: Castoridae; Palaeocastorinae; crâne; tertiaire
Translator: Kenny J. Travouillon
Deutsche Zusammenfassung
Die Schädelmorphologie des schmalen Oligozänen Bibers Capacikala gradatus wird auf der Basis eines gut erhaltenen, nahezu kompletten Schädels und fragmentarischer Mandibeln aus der John Day Formation, John Day Fossil Beds, Oregon, USA, beschrieben. Dmit wird hier der einzige nahezu komplette Schädel, der bisher außer dem Typsexemplar bekannt ist, im Detail beschrieben. Das ist besonders angemessen, da der Typus von einer unbekannten Lokalität innerhalb der John Day Formation stammt und der Schädel fragmentarisch ist. Das neu beschriebene Material wurde zwischen datierten Markerhorizonten gefunden, so dass es nicht älter als 28,7 Mio und nicht jünger als 27,8 Mio Jahre sein kann. Obwohl die Gattung Capacikala vor gut 50 Jahren benannt wurde (MacDonald, 1963) ist sie noch nicht gut bekannt. Morphologische Vergleiche werden zu anderen erwähnten oder illustrierten Exemplaren von Capacikala, Palaeocastor und heutigem Castor gemacht; es gibt Ähnlichkeiten und Unterschiede zu beiden Gattungen. Die Befunde an dem Schädel werden diskutiert im Vergleich zu Beschreibungen von Capacikala und Palaeocastor und einige Merkmale werden revidiert. Eine phylogenetische Analyse mit einigen, wenigen ausgewählten Biber Arten wurde durchgeführt, aber hat schlecht unterstützte Bäume geliefert. Aber eine komplette Revision der Biber Phylogenie und der genutzten Merkmale ist außerhalb des Umfangs dieser Arbeit.
Translator: Author
Arabic
Translator: Ashraf M.T. Elewa
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Review: The Princeton Field Guide to Mesozoic Sea Reptiles
The Princeton Field Guide to Mesozoic Sea Reptiles
Article number: 26.1.1R
April 2023