Figures to accompany "Patterns of Evolution in Ischyromys and Titanotheriomys (Rodentia: Ischyromyidae) from Oligocene Deposits of Western North America," a thesis presented by Timothy Howard Heaton to the Department of Earth and Planetary S ciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the subject of Geology, Harvard University, Cambridge, Massachusetts, August, 1988.

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Figure 1. Map showing Chadronian and Orellan fossil localities (after Emry et al. 1987).


Figure 2. Correlation chart of Oligocene fossil localities (after Emry et al. 1987).


Figure 3. Idealized diagram of occlusal view of tooth showing points digitized and positions of accessory cusps.


Occlusal View of Lower Molar
Anterior
Lingual Posterior


Figure 4. Idealized diagram of lingual view of tooth showing points digitized and position of lingual accessory cusp.


Lingual View of Lower Molar
Anterior Posterior


Figure 5. Idealized diagram of lingual view of jaw showing points digitized.


Lingual View of Dentary
Anterior Posterior


Figure 6. Sample panels from database.

|-ISCHYROM.SPE-4588------------------------------------------------------------|
|Roll039.11 Frame 11  Field # 488-54G          Acc. #        Coll. #          |
|Cat. # UNSM  05513        Coll. Carl Vondra and John A. Howe   1954           |
|Loc. #UNSM Sx-26   Material D L M/1-2     0 3 3 0  Taxon I. typus            |
|Stratigraphy Orella A                            Section 53  Level   +5 +/-  5|
|0-10 feet above upper purple-white layer                                      |
|Ref.                                   Notes                                  |
|Comments                                                                  ░░░░|
|------------------------------------------------------------------------------|

┌-ISCHYROM.LOC-520-------------------------------------------------------------┐
|Loc. # UCM 78075    Name Cameron Spring                Lat. 42.47 Long. 107.33|
|Gas Hills, Wind River Basin                                                   |
|SE1/4, NW1/4, sec. 1, T32N, R90W                                              |
|Map Gas Hills                        County Fremont         State Wyoming     |
|Group White River Form. Chadron            Memb.                    Section76|
|Epoch Oligocene    Age Chadronian   Ref.                                     ░|
└------------------------------------------------------------------------------┘

┌-ISCHYROM.SEC-62--------------------------------------------------------------┐
|Section 54 ░ Name Toadstool Park, Sioux County, Nebraska                      |
|Schultz and Stout 1955; Skinner section book 4:116-119                        |
|                                                                              |
└------------------------------------------------------------------------------┘

┌-ISCHYROM.JAW-4014------------------------------------------------------------┐
|Roll358.02       Jaw Measurements from basic MEASURE program                 |
| 1 11.54   2 10.40   3  8.33   4  8.19   5 4.41   6 6.03   7 45   8 50   9 1  |
|Ant. jaw   Med. jaw   Post. jaw depth   Ant-Med  Med-post   A-M    M-P   Right|
|  depth      depth    (line)    (point) distance distance  angle  angle  /Left|
|                                                                              |
|                 Jaw measurements calculated from above data                  |
|10 25                                                                         |
|Jaw curve                                                                     |
└------------------------------------------------------------------------------┘

┌-ISCHYROM.P4-4014-------------------------------------------------------------┐
|Roll010.06      P/4 measurements from basic MEASURE program                  |
| 1 3.42   2 13.01    3 4.11    4 2.77    5 2.69    6 3.56    7 2.08    8 0.14 |
|   Area  Periphery   Length    A-width   M-width   P-width  M-valley  P-valley|
| 9 1.72   10 1.74   11 1.02   12 0.70   13 0.62   14 2.28   15 1.35   16 1.98 |
|ALin-val. Lab-val.  PLin-val. ALV-leng. ALV-width AC-height AV-height PC-heigh|
|17 1.33   18 0.00    19 42  20  77  21  79   22 4   23 0   24 2   25 2   26 0 |
|PV-height Lin-cusp  ALV-wall ALV-P   ALV-A   Wear  Lab-C   AM-C   PM-C  Lin-C |
|                                                                              |
|                 P/4 measurements calculated from above data                  |
|27  3.56   28 3.80   29 0.67   30 0.87   31 0.87   32 0.78   33 0.42   34 0.42|
|Max-width  Per/area   AW/len.   PW/len.  MaxW/len.   AW/PW   LiV/len.  LaV/len|
| 35 0.51   36 0.03    37  48   38 1.69   39 1.49                              |
| MV/len.   PV/len.  ALV*angle   AC/val.   PC/val.                             |
└------------------------------------------------------------------------------┘


Figure 7. Diagram of jaw measurements in lingual view.

Anterior Posterior


Figure 8. Diagram of tooth measurements in occlusal view.

Occlusal View of Lower Molar
Anterior
Lingual Posterior


Figure 9. Diagram of tooth measurements in lingual view.

Lingual View of Lower Molar
Anterior Posterior


Figure 10. Scatterplot of 486 M/2's from Toadstool Park.


Figure 11. Scatterplot of 717 M/2's from Munson Ranch.


Figure 12. Scatterplot of 59 M/2's from Geike Ranch.


Figure 13. Scatterplot of 161 M/2's from Lusk area.


Figure 14. Scatterplot of 115 M/2's from Douglas area.


Figure 15. Scatterplot of 47 M/2's from Chadron area.


Figure 16. Scatterplot of 127 M/2's from Slim Buttes.


Figure 17. Scatterplot of 59 M/2's from Little Badlands.


Figure 18. Scatterplot of 111 M/2's from Flagstaff Rim.


Figure 19. Histogram of canonical variable from the output of three pairwise discriminant analyses.


A = Orella A                                            A
C = Orella C                                            A  CC
P = Pipestone                                          AA  CC
                                                       CC  CC
                                                     A CC  CC
                                                  C  A CCA CC  C
                                                  C  C CCA CC  C
                                                  C  C CCC CCA C    CC
                                                  C  C CCC CCA C   CCCC
                                                  C  CACCC CCC CC  CCCC
                                      A           C  CACCCACCC CCCCCCCCC
                               A      A           C  CCCCCCCCCCCCCCCCCCC
                               A      A         CAC ACCCCCCCCCCCCCCCCCCC
                             AAA      A         CCC CCCCCCCCCCCCCCCCCCCC    AC
                   A     A  AAAA  A   A         CCC CCCCCCCCCCCCCCCCCCCCC CACCC
                  AA     AA AAAA AA AAA   AA A CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC A     C
                  AA   AAAA AAAAAAA AAA   AA A CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC  A CC
             A   AAAA  AAAAAAAAAAAAAACCA  CC C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC CCCCC C     C
A     A   A  A A CACAAAAAAAAAAACCCCACCCACCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC C   C
+....+....+....+....+....+....+...^+....+....+....+....+....+.^..+....+....+....+....+....+....+
    -4           -3          -2           -1           0           1            2           3

                                                               C
                                                               C
                                                               C C     C
                                                               C C     C
                                                            C  C CC C  C
                                                            C  CCCC C  C
                                                            C  CCCC C  C
                                                            C  CCCC C  C
                                                       P CC C CCCCC C  C
                                                       C CC CPCCCCC C  C
                                                       C CC CCCCCCCCC  C
                                                 P     C CCCCCCCCCCCC  CC
                                                 P    PCCCCCCCCCCCCCC  CC  P
                    P                            PC   CCCCCCCCCCCCCCC  CCC C
          P         P P P                        CC CPCCCCCCCCCCCCCCCCCCCCCC  C
          P         P P P                        CC CCCCCCCCCCCCCCCCCCCCCCCC  C
          P         P P P P                      CC CCCCCCCCCCCCCCCCCCCCCCCC  C
          P   P    PP PPP P                      CCCCCCCCCCCCCCCCCCCCCCCCCCC  CC
          P  PPP P PP PPP P P P  P            P PCCCCCCCCCCCCCCCCCCCCCCCCCCC CCCCCCC
          PPPPPPPPPPPPPPPPP PPPP P        PPP CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
    P PPP PPPPPPPPPPPPPPPPPPPPCPPPC       CPC CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC    C    C
+....+....+....+....+...^+....+....+....+....+....+....+....+...^+....+....+....+....+....+....+
    -5        -4        -3        -2        -1         0         1         2         3         4


                                                               A
                                                            P  A
                                                            P  A
                                                            P  AP
                                                        P   A  AA
                                                 P      A   A  AAP  A
                           P P  P    P   P       P     PAA AA  AAAA A
                         P PPPP P  P P  PP       P     AAAPAA  AAAA A   A
                         PPPPPP PPPPPP PPPP      PPPA AAAAPAA  AAAAAAAAAA
               P    P  P PPPPPPPPPPPPPPPPPPP  PP AAPA AAAAAAAAAAAAAAAAAAA  AAA A
          P  P P  PPP PPPPPPPPPPPPPPPPPPPAPP PAA AAAAAAAAAAAAAAAAAAAAAAAAA AAA AAA          A
+....+....+....+....+....+....+....+^...+....+....+....+....+..^.+....+....+....+....+....+....+
-6       -4        -3        -2        -1         0         1         2         3         4


Figure 20. Mean tooth area of M/2 for 30 foot stratigraphic intervals at Toadstool Park and Munson Ranch, Sioux County, Nebraska. The sample size for each interval is shown in parentheses.

Toadstool Park
| 289 | * (1) Whitney Mb. | -------┼---------------------------------------------------- 185 | * | (1) 163-177| * (40) | 130-150| * (127) | Orella Mb. 93-118| * (31) | 65-89 | * (22) | 40-58 | * (15) -------┼---------------------------------------------------- 0-28 | * (235) Orella A -------┼---------------------------------------------------- | -80--20| * (14) Chadron Fm. -------┼------------┬------------┬------------┬------------┐ 3.0 3.25 3.5 3.75 4.0
Mean Area of M/2 (cm)
|
Munson Ranch
230 | * (1) | Whitney Mb. -------┼---------------------------------------------------- 153-180| * (16) | 124-133| * (3) | Orella Mb. 92-120| * (310) | 62-90 | * (302) | 45-60 | * (37) -------┼---------------------------------------------------- 8-30 | * (47) Orella A -------┼---------------------------------------------------- | -40 | * (1) Chadron Fm. -------┼------------┬------------┬------------┬------------┐ 3.0 3.25 3.5 3.75 4.0
Mean Area of M/2 (cm)


Figure 21. Mean value of labial accessory cusp for 30 foot stratigraphic intervals at Toadstool Park and Munson Ranch, Sioux County, Nebraska. The sample size for each interval is shown in parentheses.

Toadstool Park and Munson Ranch, Sioux County, Nebraska LABIAL ACCESSORY CUSP M/1 and M/2 combined
210┤ | * (6) 180┤ | * (99) 150┤ | * (240) 120┤ | * (644) 90┤ | * (612) 60┤ | * (93) 30┤ | * (563) 0┤ | * (25) -30┼------------┬------------┬------------┬------------┬---- 0.0 0.2 0.4 0.6 0.8
Mean value for Accessory Cusp (0-4) M/3 alone
210┤ * (1) 180┤ | * (37) 150┤ | * (65) 120┤ | * (217) 90┤ | * (189) 60┤ | * (27) 30┤ | * (147) 0┤ | * (7) -30┼------------┬------------┬------------┬------------┬---- 0.0 0.2 0.4 0.6 0.8
Mean value for Accessory Cusp (0-4)


Figure 22. Mean value of anterior medial accessory cusp for 30 foot stratigraphic intervals at Toadstool Park and Munson Ranch, Sioux County, Nebraska. The sample size for each interval is shown in parentheses.

Toadstool Park and Munson Ranch, Sioux County, Nebraska ANTERIOR MEDIAL ACCESSORY CUSP M/1 and M/2 combined
210┤ | (6) * 180┤ | (94) * 150┤ | (229) * 120┤ | (630) * 90┤ | (591) * 60┤ | (91) * 30┤ | (549) * 0┤ | (22) * -30┼------------┬------------┬------------┬------------┬---- 0.0 0.2 0.4 0.6 0.8
Mean value for Accessory Cusp (0-4) M/3 alone
210┤ | (0) 180┤ | * (36) 150┤ | * (67) 120┤ | * (211) 90┤ | * (188) 60┤ | * (27) 30┤ | * (146) 0┤ | * (6) -30┼------------┬------------┬------------┬------------┬---- 0.0 0.2 0.4 0.6 0.8
Mean value for Accessory Cusp (0-4)


Figure 23. Mean value of posterior medial accessory cusp for 30 foot stratigraphic intervals at Toadstool Park and Munson Ranch, Sioux County, Nebraska. The sample size for each interval is shown in parentheses.

Toadstool Park and Munson Ranch, Sioux County, Nebraska POSTERIOR MEDIAL ACCESSORY CUSP M/1 and M/2 combined
210┤ * (6) 180┤ | * (94) 150┤ |* (227) 120┤ | * (612) 90┤ | * (589) 60┤ | * (89) 30┤ |* (546) 0┤ * (21) -30┼------------┬------------┬------------┬------------┬---- 0.0 0.2 0.4 0.6 0.8
Mean value for Accessory Cusp (0-4) M/3 alone
210┤ | (0) 180┤ * (36) 150┤ | * (64) 120┤ | * (208) 90┤ | * (176) 60┤ | * (23) 30┤ | * (142) 0┤ * (6) -30┼------------┬------------┬------------┬------------┬---- 0.0 0.2 0.4 0.6 0.8
Mean value for Accessory Cusp (0-4)


Figure 24. Mean value of lingual accessory cusp for 30 foot stratigraphic intervals at Toadstool Park and Munson Ranch, Sioux County, Nebraska. The sample size for each interval is shown in parentheses.


Toadstool Park and Munson Ranch, Sioux County, Nebraska LINGUAL ACCESSORY CUSP M/1 and M/2 combined
210┤ | (6) *> 180┤ value=1.5 | * (100) 150┤ | * (240) 120┤ | * (644) 90┤ | * (602) 60┤ | * (96) 30┤ | * (555) 0┤ | * (22) -30┼------------┬------------┬------------┬------------┬---- 0.0 0.2 0.4 0.6 0.8
Mean value for Accessory Cusp (0-4) M/3 alone
210┤ | (0) 180┤ | * (34) 150┤ | * (64) 120┤ | * (205) 90┤ | * (176) 60┤ | * (22) 30┤ | * (147) 0┤ * (6) -30┼------------┬------------┬------------┬------------┬---- 0.0 0.2 0.4 0.6 0.8 Mean value for Accessory Cusp (0-4)


Figure 25. Result of Cluster analysis using Ward method on standardized mean values of 27 groups of Ischyromys. Size is the first order distinguishing variable.

Scaled Dendrogram using Ward Method               Locality
on Jaw, M/2, and M/3 measurements ┌Big Badlands (512) <I. typus, parvidens, troxelli (overall size included) ┌┴Orella C (615) ┌┼-large Orella A (20) ┌--------┤└-Scotts Bluff (13) | └┬-Little Badlands (68) Large ┌-----------------┤ └-Slim Buttes (102) Orellan | | ┌small Colorado (31) Species | | ┌-┬┴Lusk (148) Large Size | └-------┤ └-Late Chadron Complex (31) ┌-------------------┤ └---Lyman (18)
| | ┌---┬-----large Flagstaff (10) | | ┌-------┤ └-----large Pipestone (9) Mixed | | ┌-------┤ └---------McCarty's MTN (11) <T. douglassi Group | └---┤ └-----------------West Canyon Creek (10) | └-------------------------large Colorado (3) <I. pliacus
| ┌-┬-small Flagstaff (52) Small | ┌-┤ └-Cameron Spring (14) Chadronian | ┌---------┤ └---small Pipestone (125) <T. veterior Group | ┌-------┤ └-----Beaver Divide (4) <T. wyomingensis | | └---------------Harshman Quarry (1)
| Small Size | ┌--┬small Orella A (176) Small └-------------------------┤ ┌---┤ └Douglas (70) Orellan Sp.
| ┌-----┤ └---early Flagstaff (14) | ┌-----┤ ├-------Ash Spring (2) Small └---┤ | └-------Cypress Hills (7) <I. junctus Chadronian | └-------------Ledge Creek (2) Group
└-------------------Porvenir (1) <I. blacki


Figure 26. Two dimensional output of multidimensional scaling on 27 populations including absolute size.


             -3                  -2                  -1                   0                   1                   2
           2                                                                                                                  2



                                                              West
                                                             *Canyon
                                                              Creek

                                                                                                 *Harshman
                                                                                                  Quarry
           1                                                                                                                  1


                                        large
           D                             *Pipestone
           I
           M                                       large                                                   Cameron   Beaver
                                                  *Orella A                                   *small       Spring*  *Divide
                                                        Big                                    Pipestone
               large                                    Badlands
              *Colorado                             Orella *large    Lusk                      *early          *little
           0                                        C     **Flagstaff   **Chadron               Flagstaff       Flagstaff     0
                                    Slim*    Scotts**Little    *Lyman *      Small* *Douglas
                                    Buttes   Bluff   Badlands       small    Orella A
                                                                    Colorado                    Ash            *Cypress
                                                                                               *Spring          Hills
           T
           W
           O



          -1                                                                                      *Ledge                     -1
                                                                                                   Creek
                                             *McCarty's
                                              Mountain

                                                                                           *Porvenir




          -2                                                                                                                 -2
             -3                  -2                  -1        DIM        0        ONE        1                   2            


Figure 27. Two dimensional output of multidimensional scaling on 27 populations excluding absolute size.


                         -2                  -1                   0                   1                   2                   3
           2                *Ash                                                                                                  2
                             Spring

                                                                                    West
                                                                                   *Canyon
                                                                                    Creek



                                                                                                                      Porvenir*
           1                                                                                                                      1

                                                               Douglas         small
                                                                  *      Lusk**Orella A
           D                                          large Flagstaff*
           I
           M                                                          *small Colorado
                                                     early
                                          Cameron*   Flagstaff*  Slim     Orella
                                          Spring                 Buttes  *C
                                                   Little Badlands**   *Big Badlands
           0                                                      Lyman**        *Scotts                                          0
                                                    small*         *    Chadron   Bluff
                                         small      Flagstaff    large
                                 Ledge* *Pipestone               Orella A
                                 Creek
           T    *Cypress
           W     Hills
           O                                                                           *McCarty's
                                                                                        Mountain

                                                                             large
                                                                            *Pipestone
          -1                                                                                                                     -1




                                                       Harshman
                                                      *Quarry

                                                          Beaver                     large
          -2                                             *Divide                    *Colorado                                    -2
                         -2                  -1        DIM        0        ONE        1                   2                   3    


Figure 28. Result of Cluster analysis using Ward method on standardized mean values of 27 groups of Ischyromys after overall size was factored out.

Scaled Dendrogram using Ward Method               Locality
on Jaw, M/2, and M/3 measurements ┌Big Badlands (512) <I. typus, parvidens, troxelli (overall size excluded) ┌-┬┴Orella C (615) | ├┬Little Badlands (68) ┌-┤ |└Slim Buttes (102) Large | | └-large Orella A (20) Orellan ┌-┤ ├-┬-small Colorado (31) Species | | | └-Late Chadron Complex (31) ┌-------------------------┤ | └---Lyman (18) Ischyromys| | └-----Scotts Bluff (13)
┌---------┤ | ┌small Orella A (176) Small | | └-----┬┴Lusk (148) Orellan | | └-Douglas (70) Species
| └---------------------------------Porvenir (1) <I. blacki
┌-----┤ ┌-┬-----early Flagstaff (14) | | ┌-┤ └-----large Flagstaff (10) Large | | ┌-------┤ └-------McCarty's MTN (11) <T. douglassi Chadronian | | ┌---┤ └---------large Pipestone (9) Group | └---------------------┤ └-----------------West Canyon Creek (10)
| Ancestral & Misc Forms└---------------------large Colorado (3) <I. pliacus
| ┌-┬-small Flagstaff (52) | ┌---------┤ └-Cameron Spring (14) | ┌-------------┤ └---small Pipestone (125) <T. veterior | ┌---------┤ └-------------Beaver Divide (4) <T. wyomingensis | Titano- | | ┌---------┬---------------Ledge Creek (2) Small └-----------┤ └-┤ └---------------Cypress Hills (7) <I. junctus Chadronian theriomys | └-------------------------Harshman Quarry (1) Group └-------------------------------------Ash Spring (2)


Figure 29. Plot of mean values of the anterior and posterior angles between the tooth row and the ventral margin of the jaw.

46┐JAW CONVEX                                      JAW FLAT
  |                                                AND STEEP
  |                      small       *Lusk
  |                      Orella A
45┤                         *
  |
  |                Orella C*     *small
  |                               Colorado
44┤                  Douglas*
  |                              Big
  |            Slim Buttes*     *Badlands
  |                  *             *
43┤                large         Little         *
  |                Orella A      Badlands     Harshman
  |                                           Quarry
  |    *Scotts
42┤     Bluff
  |
  |             Chadron*      *Lyman
  |                                                Early   *
41┤      Ledge       Beaver     *West Canyon Ck.   Flagstaff
  |      Creek       Divide*
  |        *                *small Flagstaff
  |               Cameron*
40┤   *Ash Spr.   Spring   *large
  |                         Colorado
  |       *
  |     McCarty's
39┤     MTN
  |
  |
  |            *                             *
38┤          small                         large
  |          Pipestone                     Flagstaff
  |
  |
37┤
  |
  |
  |
36┤
  |                 *large
  |JAW FLAT          Pipestone
  |AND SHALLOW                                   JAW CONCAVE
35┴---┬------┬------┬------┬------┬------┬------┬------┬----
 ^   37     38     39     40     41     42     43     44
Posterior             Anterior Jaw Angle
Jaw Angle


Figure 30. Plot of mean values of the length of M/2 and M/3.

   |   M/2                                   large Colorado*
   | SHORTER
   |                                large Pipestone*
   |
   |                                                  Slim*
3.9┤                                   Scotts         Buttes
   |                                   Bluff      Little
   |                                     *       *Badlands
   |                         McCarty's MTN*   *large
   |                           Orella C*       Orella A
   |                                    *Big Badlands
   |
   |                                  *Lyman
   |
   |
   |                Chadron   small
3.6┤                     *   *Colorado
   | Porvenir
   |  *               *               *large
   |                Lusk               Flagstaff
   |
   |            Harshman
   |     small*     *   *West Canyon Creek
   |     Orella A
   |                 *Ledge Creek
   |             *
   |          Douglas
3.3┤
   |   early*        *small
   |   Flagstaff      Pipestone
   |
   |
   | *Beaver Divide
   |
   |           *Ash Spring
   |   *small
   | *  Flagstaff
   |Cameron
3.0┤
   |
   |
   |
   |                                                   M/3
   |   *Cypress Hills                                SHORTER
   ├-----------------┬-----------------┬-----------------┬--
^ 3.0               3.3               3.6               3.9
M/3                       M/2 Length
Length


Figure 31. Plot of mean values of the length of M/2 and the length from the posterior valley mouth to the posterior end of the tooth on M/3.

0.8┐         POSTERIOR                    *McCarty's
   |         END LARGE                     MTN
   |
   |                                   Scotts    large
   |                     West          Bluff     Pipestone
   |                     Canyon          *         *
   |                    *Creek
   |           Ledge             Lyman*       *large
   |           Creek**Harshman         *       Orella A
   |                  Quarry        Orella C
   |                                                large  *
0.7┤                                                Colorado
   |                                    *Big
   |              Lusk*    small         Badlands
   |                       Colorado
   |                         *                   *Little
   |       small                     *large       Badlands
   |       Orella A                   Flagstaff
   |          *          *Chadron                     Slim*
   |        *early                                    Buttes
   |         Flagstaff
   |
0.6┤
   |
   |             *Douglas
   |
   |
   |   *Cypress
   |    Hills
   |
   |
   |
   |           *Ash
0.5┤            Spring
   | small
   | Flagstaff
   |   *
   | *Beaver Divide
   |
   | *Cameron Spring
   |  *
   | Porvenir
   |                 *small              POSTERIOR END
   |                  Pipestone          COMPRESSED
0.4┼-----------------┬-----------------┬-----------------┬--
^ 3.0               3.3               3.6               3.9
M/3 Post.                 M/2 Length
Length


Figure 32. Plot of mean values of angles made by the posterior and medial walls of the anterior lingual valleys vs. tooth size.

   |                       *large                      LARGE
   |                        Colorado
7.5┤
   |
   |                    large
   |                    Pipestone
   |                       *
   |                         *Slim
   |                          Buttes
   |
   |                           Scotts
   |          large*          *Bluff
7.0┤          Orella A    *Little
   |                       Badlands
   |                Big                           McCarty's*
   |     Orella C* *Badlands                      MTN
   |
   |                  Lyman*
   |                                 *large
   |                                  Flagstaff
   |                        small
   |                       *Colorado
6.5┤             Chadron*
   |
   |            *Lusk             *West Canyon Creek
   |
   |
   |
   |*Harshman
   | Quarry          Orella A                 Porvenir
   |                    *                        *
   |          Douglas*    *small      *Ledge
6.0┤                       Pipestone   Creek
   |      *Beaver
   |       Divide
   |                          *early
   |*Ash                       Flagstaff
   | Spring
   |                small
   |               *Flagstaff
   |     *
   |  Cameron
5.5┤  Spring             *Cypress
   |                      Hills                        SMALL
   └-┬------------┬------------┬------------┬------------┬--
^    70           90          110          130          150
Area of          Posterior Angle - Wall Angle of
M/2+M/3        Anterior Lingual Valley of M/2+M/3


Figure 33. Plot of mean values of cusp heights divided by valley heights in lingual view vs. tooth size.

   |                                              large*
   |                                              Colorado
7.5┤
   |
   |
   |                                      Slim
   |                                      Buttes*
   |                                               large   *
   |                                               Pipestone
   |
   |                                  large      Scotts
   |                                  Orella A* *Bluff
7.0┤                                          *
   |                                       Little Badlands
   |           *McCarty's MTN
   |                                   Big*       *Orella
   |                                   Badlands    C
   |       large                                           *
   |      *Flagstaff                                   Lyman
   |
   |
   |                        small*
6.5┤                        Colorado      *Chadron
   |
   |          West*          *
   |          Canyon        Lusk
   |          Creek
   |
   |*Harshman
   | Quarry                  small
   |      Ledge   Douglas   *Orella A
   |      Creek*       *  *
6.0┤                      small
   |    *Beaver           Pipestone
   |     Divide
   |*                                                Ash
   |early                                            Spring*
   |Flagstaff
   |                   small
   |                   Flagstaff*
   |                             *Cameron
   |                              Spring
5.5┤LOW              Cypress*                          HIGH
   |CUSPS            Hills                             CUSPS
   ├---------┬---------┬---------┬---------┬---------┬------
^ 5.6       5.8       6.0       6.2       6.4       6.8
Area of         Ant. Cusp Height/Ant. Valley Height +
M/2+M/3    Post. Cusp Height/Post. Valley Height of M/2+M/3


Figure 34. Phylogenetic tree showing possible relationships between species of Ischyromys and Titanotheriomys.

Age (MY)  Texas       Wyoming-Nebraska       Montana        Saskatchewan
------------------------------------------------------------------------

                                                                 Whitneyan
30 ---------------------- Orella C -------------------------------------
                     ╔══ (I. typus)                              Orellan
                     ║
                     ║    Orella A                               Orellan
31 ----------------- ║ (I. parvidens) ----------------------------------
                     ║        ║                                  Chadronian
                     ╚══ Late Chadron
                           Complex
32                         (I. sp.)
                              ║
   ╔══════════════════════════╝
   ║                                     small Pipestone
33 ║   Ash Spring      large Flagstaff ╔═ (T. veterior)
   ║    (T. n.s.)         (T. n.s.)    ║ large Pipestone
   ║        ║        ╔════════╝        ║    (T. n.s.)
   ║        ║        ║ small Flagstaff,║        ║
34 ║        ║        ║ Cameron Spring, ║        ║
   ║        ║        ║  Beaver Divide  ║ ╔══════╝
   ║        ║        ║  (T. veterior)  ║ ║
   ║        ║        ║        ╠════════╝ ║  McCarty's
35 ║        ║        ║        ║        ╔═╝  Mountain           Cypress
   ║        ║        ║        ║        ║ (T. douglassi)         Hills
   ║        ║        ║        ║        ║        ║           (T. junctus)
   ║        ╚═════════════════╬═══════════════════════════════════╝
36 ║                 ╚═early Flagstaff═╝        ║
   ╠?══════════════════ (T. veterior) ══════════╝
   ╠?═══════════════════╗     ║
   ╠?═════════════╗     ║     ?═════════════╗
37 ╠?═══════╗     ║     ╚═════║═════════════╣
   ?        ║     ╚═══════════╣             ║                    Chadronian
---║--- Porvenir ---- West Canyon Creek ----║---------------------------
   ║   (I. blacki) ══??══ (I. n.s.)         ║                    Duchesnean
38 ╚════════╦════════╝╚═══════╦═════════════╝
            ║           Badwater Creek
            ?           (taxon indet.)

Timothy H. Heaton: E-mail, Home page, Phone (605) 677-6122, FAX (605) 677-6121