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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).

 figure1

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.

 figure2

FIGURE 3. Skull of Capacikala gradatus, JODA 621 in frontal view with left infraorbital foramen (iof). Scale bar equals 5 mm.

 figure3

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.

 figure4

FIGURE 5. Possible phylogeny of selected castorid taxa as illustrated by neighbour joining method.

figure5 

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).

 figure6

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.

figure7 

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.

 figure8

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.

figure9 

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.

 figure10

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.

figure11

 

APPENDIX 1

Photograph of the locality accompanying the field notes. Archive of the John Day National Park. Curtesy of Joshua X. Samuels, JODA.

 appendix1

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

 
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Cranial Morphology of the Oligocene beaver Capacikala gradatus from the John Day Basin and comments on the genus

Clara Stefan

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

419 arab

Translator: Ashraf M.T. Elewa

 

 

Clara Stefen
Senckenberg Naturhistorische Sammlungen Dresden
Museum of Zoology
Königsbrücker Landstrasse 159
01109 Dresden
Germany
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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.