Systematics of the genus Palaeictops Matthew, 1899 (Mammalia: Leptictidae), with the description of two new species from the Middle Eocene of Utah and Wyoming
Author
Velazco, Paúl M.
Author
Novacek, Michael J.
text
American Museum Novitates
2016
2016-11-18
2016
3867
1
42
http://www.bioone.org/doi/10.1206/3867.1
journal article
5852
10.1206/3867.1
1d6299e9-5c62-4abd-be37-59efcb217cbf
0003-0082
4598386
Palaeictops bridgeri
(
Simpson, 1959
)
Figure 7
, table 1
Diacodon bridgeri
Simpson, 1959: 1–4
, fig. 1.
Palaeictops bridgeri
Van Valen, 1967: 232
. First use of current name combination.
HOLOTYPE
:
AMNH 56032
, consisting of a right ramus that retains p5–m3 (fig. 7).
TYPE LOCALITY: Locality 6 (Misery Quarry) of
McGrew (1959)
in the vicinity of Tabernacle Butte,
Wyoming
. Upper Bridger Formation, Middle Eocene (Bridgerian NALMA).
DIAGNOSIS: Like
Palaeictops altimontis
(see diagnosis below) and unlike other species of the genus in having a p5 with a low paraconid bordered posteriorly by a distinctly opened, lingual prefossid, a shortened talonid, and a deeply excavated talonid basin opened lingually and bordered posteriorly by steep faces of the entoconid and hypoconid (fig. 7). Both the
types
of
P. bridgeri
and
P. altimontis
have slightly worn, but low trigonids on m1–m3. Differs from
P. altimontis
in larger size (length of m1–m
3 in
P. bridgeri
equals
11.23 mm
, length in
P. altimontis
equals
9.18 mm
.), and in having a p5 metaconid positioned more posteriorly relative to the protoconid and a more anteroposteriorly “opened” trigonid due to a more salient paraconid on m2. M2 possibly referable to
P. bridgeri
is more transverse with a shallower ectoflexus than M2 of
P. altimontis
.
FIG. 6.
Palaeictops borealis
, occlusal (left), labial (center), and lingual (right) views of:
A,
right P5 (RSM P1654.221);
B,
right M1 (ROM 1676, holotype);
C,
left m1 (ROM 23595);
D,
right m2 (RSM P1654.225).
TABLE 1. Measurements of the cheekteeth of
Palaeictops
. All measurements are in millimeters.
| Upper teeth |
Lower teeth |
| Element |
L |
AW |
PW |
Element |
L |
WTR |
WTA |
|
Palaeictops bicuspis
|
|
AMNH 4802
type
|
| LP4 |
5.25 |
2.80 |
Lp5 |
3.92 |
1.55 |
2.14 |
| LP5 |
3.40 |
4.40 |
3.86 |
Lm1 |
3.11 |
2.15 |
2.35 |
| LM1 |
3.07 |
3.81 |
4.11 |
Lm2 |
3.00 |
| LM2 |
2.72 |
3.97 |
3.75 |
Lm3 |
3.27 |
2.37 |
1.70 |
| LM3 |
2.44 |
3.17 |
2.65 |
| AMNH 4255 |
| Lm2 |
3.09 |
2.00 |
2.45 |
| Lm3 |
3.40 |
2.30 |
2.14 |
|
Palaeictops bridgeri
|
|
AMNH 56032
type
|
| Rp5 |
4.25 |
2.31 |
2.22 |
| Rm1 |
3.65 |
2.52 |
2.47 |
| Rm2 |
3.58 |
2.69 |
2.64 |
| Rm3 |
4.00 |
2.39 |
2.03 |
|
Palaeictops borealis
|
|
ROM 1676
type
|
| RM1 |
4.45 |
4.60 |
4.70 |
| RSM P1654.220 |
| RDP5 |
4.00 |
4.80 |
4.36 |
| RSM P1654.221 |
| RP5 |
4.38 |
5.03 |
5.15 |
| RSM P1654.222 |
| RP5 |
4.30 |
5.11 |
5.21 |
| ROM 23595 |
| Lm1 |
4.04 |
2.15 |
2.42 |
| RSM P1654.226 |
| Rm1 |
2.47 |
| RSM P1654.225 |
| Rm2 |
4.27 |
2.28 |
2.50 |
| ROM1685 |
| Rm2 |
3.98 |
2.40 |
2.70 |
|
Palaeictops matthewi
|
|
FMNH 26904
type
|
| RP4 3.26 |
2.50 |
Lp4 |
4.02 |
1.60 |
| RP5 2.80 |
3.21 |
3.56 |
Lp5 |
3.90 |
2.05 |
1.84 |
| RM1 2.90 |
4.03 |
4.17 |
Rm1 |
3.10 |
2.36 |
2.04 |
| RM2 2.82 |
4.41 |
4.16 |
Rm2 |
3.21 |
2.36 |
2.13 |
| RM2 |
3.60 |
| FMNH 26481 |
| RP4 3.57 |
3.06 |
|
Palaeictops multicuspis
|
|
AMNH 14741
type
|
| Lp2 |
3.66 |
1.42 |
| Lp4 |
4.42 |
1.74 |
| Lp5 |
4.21 |
2.41 |
2.21 |
| Lm1 |
3.20 |
2.67 |
2.63 |
| Lm2 |
3.27 |
2.65 |
2.47 |
| Lm3 |
3.40 |
2.50 |
2.09 |
|
Palaeictops altimontis
,
new species
|
|
AMNH 96250
type
|
| RDP4 3.33 |
2.90 |
Lp5 |
3.55 |
2.17 |
2.07 |
| RDP5 2.59 |
3.57 |
3.47 |
Lm1 |
3.15 |
2.65 |
2.47 |
| LP5 3.34 |
3.36 |
3.65 |
Lm2 |
2.87 |
2.97 |
2.76 |
| LM1 2.85 |
3.95 |
4.34 |
Lm3 |
3.16 |
2.60 |
2.16 |
| LM2 2.80 |
4.12 |
4.33 |
| LM3 2.08 |
3.80 |
2.90 |
|
Palaeictops robustus
.
new species
|
| CM 11954 typea |
| LP1 3.23 |
1.83 |
| RP4 5.77 |
4.12 |
| RP5 5.55 |
5.38 |
5.86 |
| RM1 4.80 |
6.23 |
6.93 |
a
The dentition of this specimen is worn down, approximate measurements are given for size comparison with the other species.
FIG. 7. Right ramus of
Palaeictops bridgeri
AMNH
56032 (holotype), containing p5–m3, in (clockwise from upper left) lateral, occlusal, and medial views. Scale bar = 1 cm.
DISTRIBUTION: Bridger Formation, Bridger Basin, western
Wyoming
, Middle Eocene (Bridgerian NALMA).
REFERRED MATERIAL: AMNH 9873, left M2, Main locality, Tabernacle Butte, Sublette Co.,
Wyoming
. Upper Bridger Formation.
REMARKS:
Palaeictops bridgeri
was clearly described and illustrated by
Simpson (1959)
who first noted the distinctive characters of its lower, last premolar. The new
Palaeictops altimontis
species from the Tepee Trail locality (see below) is most similar to
P. bridgeri
, but the two species differ in size and in details of the lower dentition. Moreover, the possibility that a leptictid M2 (AMNH 98731) from Tabernacle Butte is referable to
P. bridgeri
provides further evidence for the distinction of this species from
P. altimontis
.