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Preliminary Survey of a Paleocene Faunule
from the Angels Peak Area, New Mexico

BY

ROBERT W. WILSON


University of Kansas Publications
Museum of Natural History

Volume 5, No. 1, pp. 1-11, 1 figure in text
February 24, 1951


University of Kansas
LAWRENCE
1951




UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, A. Byron Leonard,
Edward H. Taylor, Robert W. Wilson

Volume 5, No. 1, pp. 1-11, 1 figure in text

February 24, 1951


UNIVERSITY OF KANSAS
Lawrence, Kansas


PRINTED BY
FERD VOILAND, JR., STATE PRINTER
TOPEKA, KANSAS
1951

23-4458




Preliminary Survey of a Paleocene Faunule
from the Angels Peak Area, New Mexico

By

ROBERT W. WILSON


INTRODUCTION

Angels Peak stands on the eastern rim of a large area of badlands
carved by a tributary of the San Juan River from Paleocene strata of
the Nacimiento formation, and presumably also from Wasatchian strata of
the San José (Simpson, 1948). This area of badlands lies some twelve
miles south of Bloomfield, New Mexico in the Kutz Canyon drainage.
Angels Peak (Angel Peak of Granger, 1917) and Kutz Canyon (Coots Cañon
of Granger, and of Matthew, 1937) are names that have been applied to
the location (figure 1).

[Illustration: FIGURE 1. Map of a part of the San Juan Basin, New
Mexico, showing location of University of Kansas fossil locality west
of Angels Peak.]

E. D. Cope's collector, David Baldwin, possibly worked in this area in
the Eighties. The first published record, however, of mammalian fossils
from the Angels Peak badlands was made by Walter Granger in 1917 as a
result of his field work in the preceding summer. Granger obtained
specimens, usually poorly preserved, but occasionally rather abundant
locally, from various levels up to within 150 feet of the western rim
of the badlands basin. This collection was obviously of Torrejonian or
middle Paleocene age. In the 1917 report, Granger gave as a faunal list
the following species:

_Tetraclaenodon_
_Mioclaenus turgidus_
_Periptychus rhabdodon_
_Anisonchus sectorius_
_Protogonodon sp. nov._
_Tricentes_
_Deltatherium_
_Psittacotherium_

To this list should be added _Triisodon antiquus_, a specimen of which
is stated by Matthew to come from Kutz Canyon in his monograph
(1937:80) on the Paleocene faunas of the San Juan Basin.

In the summer of 1948, a field party from the University of Kansas was
fortunate in finding a local concentration of rather well preserved
material at the western edge of the badlands at Angels Peak. Because it
probably will be some time before a full account of this faunule can be
prepared, it is thought advisable, preliminarily, to give a general
statement as to occurrence, and tentatively to list the species.


OCCURRENCE

The mammalian fossils, numbering approximately 150 specimens, were all
obtained within a small area located in the NW 1/4 of sec. 14, T. 27 N,
R. 11 W, San Juan County, New Mexico. The specimens were collected from
a zone of reddish silt three to four feet in thickness. The actual bone
layer, not as yet located, may prove to be thinner than this. Almost
all the material was recovered from approximately 100 linear yards of
outcrop. A few specimens, however, were obtained at varying distances
away from this central area, as far distant perhaps as one-half mile.
Of these, nineteen were at the same level stratigraphically, and only
one was lower (by 70 feet) in the section. This latter specimen,
representing a new genus and species of Primates, is not certainly
duplicated by material at the main concentration. Seemingly, the others
are.

       *       *       *       *       *

The red zone at the "bone pocket" carries many concretionary masses
which frequently contain the fossil specimens. Not all specimens,
however, are from such lumps.

Even within the area of greatest concentration, specimens are of
sporadic occurrence. A low ridge, a few feet high, may have abundant
material weathering from the rock on one slope, but have the opposite
side barren. Occasionally, a small rill three or four feet in length
and six inches or so across may carry fragments of five or six
individuals representing several genera. For example, in one such rill
were found _Didymictis_, n. sp. b; _Goniacodon levisanus_; _Tricentes
cf. T. subtrigonus_; and _Protoselene opisthacus_. No specimens were
found in place in unweathered rock, but the quarry possibilities of the
bone pocket have still to be tested.

The stratigraphic position of the bone concentration in relation to
the total Nacimiento section exposed in Kutz Canyon has not been
determined. It is approximately 160 feet below the western rim at a
point nearest the "pocket". The upper 100 feet of strata consists of
sandstone believed by Granger (1917:822) to represent either: (1)
equivalent of the "Wasatch" (San José) of the Ojo Alamo section, or
(2) "Torrejon" (upper Nacimiento). Granger perhaps favored the first
interpretation, but the writer, at present, thinks the second
probable.


THE MAMMALIAN FAUNULE

The following mammalian species have been identified as present in the
Angels Peak "pocket".

Order Multituberculata
  Family Ptilodontidae
    _Mimetodon?_ cf. _M. trovessartianus_

Order Insectivora
  Family Palaeoryctidae
    _Palaeoryctes_ cf. _P. puercensis_
  Family Leptictidae
    _Prodiacodon?_ sp.
  Family Pantolestidae
    _Pentacodon_ n. sp.
  Family Mixodectidae
    _Indrodon malaris_

Order Primates
  Family Anaptomorphidae
    anaptomorphid? new gen. and sp.
      (70 feet stratigraphically below level of Angels Peak pocket).
  ? Primates, gen. and sp. indet.

Order Taeniodonta
  Family Stylinodontidae
    _Psittacotherium?_ sp.

Order Carnivora
  Family Arctocyonidae
    _Tricentes_ cf. _T. subtrigonus_
    _Chriacus truncatus_
    _Chriacus_ nr. _C. baldwini_
    _Deltatherium fundaminus?_
    _Claenodon_ n. sp.
    _Triisodon?_ sp.
    _Goniacodon levisanus_
  Family Miacidae
    _Didymictis_ n. sp. a
    _Didymictis_ n. sp. b

Order Condylarthra
  Family Hyopsodontidae
    _Mioclaenus turgidus_
    _Ellipsodon_ cf. _E. inaequidens_
    _Ellipsodon acolytus_
    _Protoselene opisthacus_
  Family Phenacodontidae
    _Tetraclaenodon_ nr. _T. puercensis_
  Family Periptychidae
    _Coriphagus encinensis_
    _Anisonchus sectorius_
    _Periptychus_ nr. _P. carinidens_


ANGELS PEAK CENSUS

The total number of specimens for each member (species or genus) of
the faunule is tabulated in the list on the page facing, page 7. For
the purposes of this list, census, a few of the isolated teeth have
been counted as jaws. They were so counted whenever they seemed to be
representative of separate, individual animals.

The census-count includes all of the specimens that were identified.
The numbers in parentheses, on page 7, refer to those individuals that
were found outside of the 100 linear yards or so of outcrop comprising
the principal area of concentration of specimens.

+=============================+===========+===========+=============+
|                             |upper jaws |lower jaws | upper and   |
|                             |(isolated) |(isolated) | lower jaws  |
|                             |           |           |(associated) |
+-----------------------------+-----------+-----------+-------------+
| _Mimetodon_? cf.            |           |           |             |
| _M. trovessartianus_        |           |    1      |             |
+-----------------------------+-----------+-----------+-------------+
| _Palaeoryctes_ cf.          |           |           |             |
| _P. puercensis_             |           |           |      1      |
+-----------------------------+-----------+-----------+-------------+
| _Prodiacodon?_ sp.          |           |    1      |             |
+-----------------------------+-----------+-----------+-------------+
| _Pentacodon_ n. sp.         |           |    2 (1)  |             |
+-----------------------------+-----------+-----------+-------------+
| _Indrodon malaris_          |           |    4      |             |
+-----------------------------+-----------+-----------+-------------+
| Primates n. gen. and sp.    |   1 (1)   |           |             |
+-----------------------------+-----------+-----------+-------------+
| ? Primates                  |           |    2      |             |
+-----------------------------+-----------+-----------+-------------+
| _Psittacotherium?_ sp.      |   1       |           |             |
+-----------------------------+-----------+-----------+-------------+
| _Tricentes_ cf.             |           |           |             |
| _T. subtrigonus_            |   7       |   15      |      4      |
+-----------------------------+-----------+-----------+-------------+
| _Chriacus truncatus_        |   1       |    6      |      5 (2)  |
+-----------------------------+-----------+-----------+-------------+
| _Chriacus_ nr.              |           |           |             |
| _C. baldwini_               |           |    1      |             |
+-----------------------------+-----------+-----------+-------------+
| _Deltatherium fundaminus?_  |   3       |    1      |             |
+-----------------------------+-----------+-----------+-------------+
| _Claenodon_ n. sp.          |   1       |    1      |             |
+-----------------------------+-----------+-----------+-------------+
| _Triisodon?_ sp.            |   1       |           |             |
+-----------------------------+-----------+-----------+-------------+
| _Goniacodon levisanus_      |           |    2      |             |
+-----------------------------+-----------+-----------+-------------+
| _Didymictis_ n. sp. a       |           |    1      |      1      |
+-----------------------------+-----------+-----------+-------------+
| _Didymictis_ n. sp. b       |   1       |    3      |             |
+-----------------------------+-----------+-----------+-------------+
| _Mioclaenus turgidus_       |   2       |    2      |      2      |
+-----------------------------+-----------+-----------+-------------+
| _Ellipsodon_ cf.            |           |           |             |
| _E. inaequidens_            |           |    3 (1)  |             |
+-----------------------------+-----------+-----------+-------------+
| _Ellipsodon acolytus_       |   3       |   11      |      1      |
+-----------------------------+-----------+-----------+-------------+
| _Protoselene opisthacus_    |   3 (2)   |    3 (2)  |      2      |
+-----------------------------+-----------+-----------+-------------+
| _Tetraclaenodon_ nr.        |           |           |             |
| _T. puercensis_             |   5 (2)   |   18 (2)  |      4 (1)  |
+-----------------------------+-----------+-----------+-------------+
| _Coriphagus encinensis_     |           |    2      |             |
+-----------------------------+-----------+-----------+-------------+
| _Anisonchus sectorius_      |   4 (2)   |    8 (2)  |             |
+-----------------------------+-----------+-----------+-------------+
| _Periptychus_ nr.           |           |           |             |
| _P. carinidens_             |   3 (1)   |    3 (1)  |      2      |
+-----------------------------+-----------+-----------+-------------+
|       Totals                |  36       |   90      |     22      |
|                             |           |           |    148      |
+-----------------------------+-----------+-----------+-------------+


ENVIRONMENT

The faunal list is rather long for one obtained from such a restricted
area. It is not exceptional in this regard, however, for even longer
lists have been made from single quarry sites in the Paleocene
(Simpson, 1937:33-34). The exact number of genera and species
represented is still uncertain. It seems that twenty-one genera and
twenty-four species are present and that they are distributed among
eleven to twelve families and five to six orders. A greater number of
genera and species may be recorded eventually.

The ferungulate cohort constitutes most of the fauna (91 percent),
and this fact indicates a floodplain facies as the most probable
depositional environment. The small representation of multituberculates,
insectivores, and insectivore derivatives, however, may be attributed
in part to the difficulties inherent in surface collecting of minute
specimens.

Some resemblance in percentage composition is shown to the faunules of
the Fort Union Group if those forms too small to be seen readily in
collecting of surface material are omitted from the Montanan lists, but
differences exist not entirely the result of either geographic or
stratigraphic separation. Thus, the phenacodontids of the Angels Peak
are relatively abundant, matching figures obtained for surface
collecting in the Fort Union of Montana (Simpson, 1937:61).

That the faunule is not completely of floodplain type is seen in the
absence or rarity of such relatively large carnivores as _Claenodon
ferox_, the larger species of _Chriacus_, _Triisodon_, and the entire
absence of the Mesonychidae. The absence of the mesonychids might, but
probably should not, be explained as a result of stratigraphic
differences. There seems to be no reason for thinking that the Angels
Peak faunule antedates the appearance of the Mesonychidae. They are
absent from the Dragon and earlier levels, but are also extremely rare
in the Lebo of the Fort Union Group. In the ungulate population, the
absence of species of _Ellipsodon_ other than _E. acolytus_ (_E.
inaequidens_ is so rare everywhere that it hardly seems an exception to
this statement), and the complete absence of _Haploconus_ likewise
suggest some, presumably local, peculiarity of environment. The latter
genus is absent from the Lebo, but is recorded from the Dragon (Gazin,
1941:3), a fact which prevents attaching any age significance to its
absence from the Angels Peak faunule. It should be mentioned, however,
that no remains of _Haploconus_ were reported as a result of the more
extensive collecting by Granger in the Angels Peak area. Incidentally,
the type of _Haploconus angustus_ is said to come from near Huerfano
Peak (Matthew, 1937:156).

The high ratio of carnivores to ungulates is a peculiarity shared with,
but far exceeded by, the Lebo fauna if figures obtained from surface
collections of the latter are used. It seems unlikely that this ratio
is the result of selective trapping in the accumulating sediments.
Perhaps, this high ratio reflects the imperfectly carnivorous habits of
the Paleocene creodonts as a group. One obvious explanation, regardless
of probability or merit, is that some of these do not belong to the
Carnivora.

The percentage composition of the Angels Peak faunule based on 148
identifiable mammalian specimens, is as follows:

                             Percent
Insectivora:                    5
Carnivora:
  Arctocyonidae:           32
  Miacidae:                 4
                          ---  36
Condylarthra:
  Hyopsodontidae:          22
  Phenacodontidae:         18
  Periptychidae:
    Anisonchinae:      10
    Periptychinae:      5
                      ---  15
                          ---  55

Others:                         4
                             ----
                              100

The most common forms in the Angels Peak faunule are: _Tricentes_ cf.
_T. subtrigonus_, _Chriacus truncatus_, _Ellipsodon acolytus_,
_Tetraclaenodon_ nr. _T. puercensis_, and _Anisonchus sectorius_.

Post-cranial skeletal elements are of relatively rare occurrence in the
pocket. The presence of several more or less complete skulls, and the
relatively frequent association of upper and lower dentitions, however,
seem to be points against ascribing the accumulation to the activities
of predators and scavengers, otherwise perhaps indicated by the large
amount of resistant tooth material.


AGE OF THE FAUNULE

The Angels Peak faunule, as Granger stated, is of Torrejonian age. This
fact is clearly evident for the genera are all, with the exception of
the forms referred to the Primates, represented in beds of that age
elsewhere in the Nacimiento. Further, approximately two-thirds of the
known "Torrejon" genera are recorded by specimens from the Angels Peak
pocket. The primate remains present no evidence for suspecting a
difference in age, because the order is otherwise unrecorded in the
Torrejonian of New Mexico. The species are in most instances identical
or closely allied with those hitherto recognized. It is evident from
this that the Angels Peak faunule is more closely correlated in time
with the San Juan Torrejonian fauna as a whole than with either the
Dragon fauna or the Tiffanian. In respect to the San Juan Torrejonian,
closest resemblance is to the _Deltatherium_ zone fauna rather than to
the _Pantolambda_ zone fauna (Osborn, 1929:62). The difference in the
faunas of these two zones is largely, if not entirely, facial in
character.

It is not clearly evident, however, that we are dealing with exactly
contemporaneous assemblages when comparison is made between the Angels
Peak faunule and the rest of the San Juan fauna which serves
collectively to define the typical Torrejonian. It may be: (1) that the
Angels Peak faunule is of slightly different age than the latter, or
(2) that the latter is susceptible of stratigraphic subdivision, and
the Angels Peak faunule marks one stage of a sequence in time. This
problem will not be easily solved, and perhaps may never be, for
concentrations similar to that of the Angels Peak faunule are of
infrequent occurrence. It is beyond the scope of the present paper, and
of the present stage of our knowledge of the "Torrejon" fauna, to
discuss at length the possible difference in age, but the following
remarks summarize the matter for the Angels Peak material.

Many of the Angels Peak specimens differ in minor ways from those
previously described from the Torrejonian of the San Juan Basin. Some
of these differences are sufficiently great for the recognition of new
species. Other differences at present are not clearly valid on a
specific level, and it may become necessary to restudy the entire fauna
if satisfactory conclusions ever are reached.

A direct comparison can be made between the Angels Peak faunule, and a
numerically smaller and less well preserved one obtained by the
University of Kansas from a bone concentration near the head of
Kimbetoh Arroyo. The latter faunule presumably is from the
"_Deltatherium_ zone," and hence does not occupy a demonstrably high
position in the "Torrejon," rather, one seemingly down toward the first
known appearance of the fauna. Closely related or identical species of
nine genera occur at both localities. Of these, the specimens of one
species seem to be indistinguishable; the specimens of another Angels
Peak member are perhaps slightly more advanced; and seven include
specimens, distinguishable in greater or lesser degree, which suggest,
principally in smaller size, a less advanced stage for the Angels Peak
faunule.

In general, the non-ferungulate part of the Angels Peak faunule seems
to depart more widely from what is typical of the "Torrejon" fauna than
do the Carnivora and Condylarthra. Because the former is very poorly
represented in the faunule, and not too well known elsewhere in the San
Juan Basin, it may be argued that the apparent differences would
disappear with the acquisition of more material. This may be so, but at
present the point can not be demonstrated.

It is not justified at present to maintain that the Angels Peak species
occupy an earlier position in the Torrejonian than do those obtained
from outcrops between Kimbetoh and the heads of the two forks of Arroyo
Torrejon. Indeed, the stratigraphic position of the Angels Peak pocket
with a considerable thickness of Torrejonian strata beneath it, tends
to argue against such a view. Nevertheless, it is possible, if not
probable, that such is the case, or at least that detailed work would
reveal a series of faunules of slightly different ages in the
Torrejonian stage of the Nacimiento formation. Of course, chance in
collecting, as well as geographic and ecologic differences, play their
part in giving such a local faunule as that at Angels Peak its somewhat
different aspect, but these factors may not account altogether for the
observed differences.


LITERATURE CITED

GAZIN, C. L.
  1941. The mammalian faunas of the Paleocene of central Utah, with
        notes on the geology. Proc. U. S. Nat. Mus., 91, no. 3121:
        1-53, 3 pls., 29 figs. in text.

GRANGER, WALTER.
  1917. Notes on Paleocene and lower Eocene mammal horizons of northern
        New Mexico and southern Colorado. Bull. Amer. Mus. Nat. Hist.,
        art. 32: 821-830, 2 pls., 1 fig.

MATTHEW, W. D.
  1937. Paleocene faunas of the San Juan Basin, New Mexico. Trans.
        Amer. Philos. Soc., n. s., 30: i-viii, 1-510, 65 pls., 85
        figs. in text.

OSBORN, H. F.
  1929. The titanotheres of ancient Wyoming, Dakota, and Nebraska.
        U. S. Geol. Surv., Monog. 55 (2 vols.): i-xxiv, i-xi, 1-953,
        236 pls., 797 figs. in text.

SIMPSON, G. G.
  1937. The Fort Union of the Crazy Mountain Field, Montana, and its
        mammalian faunas. U. S. Nat. Mus., Bull. 169: i-x, 1-287,
        10 pls., 80 figs. in text, 62 tbls.

  1948. The Eocene of the San Juan Basin, New Mexico. Amer. Jour.
        Sci., 246: 257-282, 363-385, 5 figs. in text.

_University of Kansas, Museum of Natural History, Lawrence, Kansas.
Transmitted July 1, 1950._




       *       *       *       *       *

Transcriber's Notes

Italicized text is shown within _underscores_.

Page 4: Changed preceeding to preceding
 (field work in the preceding summer).