Postilla

Peabody Museum Q H
of Natural History /

Yale University XE 34x
SL i

New Haven, CT 06511

(Received 11 January 1984)
Abstract

Five mammalian specimens from the late
Paleocene Black Mingo Group, Berkeley
County, South Carolina, represent the first
occurrence of Paleocene land-mammals from
the east coast of North America. A P, or P,
represents the taeniodont Ectoganus
gliriformis lobdelli, known previously only from

the late Paleocene of western North America.

A M' or M? represents Mingotherium holtae,
new genus and species, a taxon which may
be closely related to pseudictopids,
uintatheres and xenungulates. A lower
premolar or molar can only be classified as
‘‘Tribosphenida incertae sedis."’ A ?canine
and a parietal can only be identified as
‘Mammalia incertae sedis.”

Key Words
Fossil mammal, Paleocene, South Carolina,

Ectoganus, Mingotherium, Pseudictops,
Dinocerata.

© Copyright 1985 by the Peabody Museum of
Natural History, Yale University. All rights reserved.
No part of this publication, except brief quotations
for scholarly purposes, may be reproduced without
the written permission of the Director, Peabody
Museum of Natural History.

Postilla Number 196
3 April 1985

a

Preliminary Description of a
New Late Paleocene
Land-Mammal Fauna from
South Carolina, U.S.A.

Robert Milton Schoch

Introduction i
During the excavation of a mreroclectics
turbine pit along the Santee Rediversion Canal
just north of St. Stephen, South Carolina, a
diverse late Paleocene biota was discovered
in the Black Mingo Group. The biota includes
calcareous nannofossils, dinoflagellates,
molluscs, sharks, rays, teleosts, turtles,
squamates, crocodiles and land-mammals.
This is the first known occurrence of
Paleocene-early Eocene land-mammals from
the east coast of North America (Schiebout
1979, Savage and Russell 1983). Schiebout
(1979, p. 85) reported, but did not describe or
illustrate, a single miacid tooth ‘‘from the base
of the Gosport Sand [i.e., Gosport Formation]
... at the Little Stave Creek site in Clark
County, Alabama.” This occurrence is
probably late middle Eocene (Bartonian,
chronozone 18) in age (Hazel, Edwards and
Bybell, in press). Notiotitanops
mississippiensis, described by Gazin and
Sullivan (1942) from the Lisbon Formation of
Clark County, Mississippi, is probably early
middle Eocene (Lutetian) in age (Hazel,
Edwards and Bybell, in press).

Albert E. Sanders (Curator of Natural
History, Charleston Museum, Charleston,
South Carolina) and Robert E. Weems (U.S.
Geological Survey, Reston, Virginia) kindly
entrusted me with the land-mammal material
from the Black Mingo Group for description.
Arrangements are currently being made for
publication of all of the vertebrate groups
from this locality, hopefully as separate
sections in a single outlet. However, such

2 Paleocene Land-Mammals Postilla 196
of South Carolina

Fig. 1

Ectoganus gliriformis lobdelli, ChM PV2926 (A-E)
and Mammalia incertae sedis, ChM PV2924 (F-/). A)
stereophotograph of occlusal view of left P3 or P,;
B) anterior view of left P; or P,; C) labial view of left
P, or P,; D) posterior view of left P; or P,; E) lingual
view of left P, or P,; F) lateral view of caniniform; G)
posterior view of caniniform; H) medial view of
caniniform; /) anterior view of caniniform. All figures
x 1.25.

Sirs nnn nnn n nn enn EE UIrE IEE UIIEIEIEIEIISSSEESSS SS

3 Paleocene Land-Mammals
of South Carolina

Postilla 196

publication is at least several years away. Due
to the extreme rarity and importance of the
South Carolina land-mammal material, it is
imperative that a brief, initial description be
made available to interested workers.
Therefore in this paper | illustrate and describe
the South Carolina land-mammal fauna. In the
aforementioned future contribution | will
discuss the detailed affinities,
paleobiogeographic and paleoecologic
implications of this land-mammal fauna. Tooth
nomenclature follows Zhou, Qiu and Li (1975).

Systematic Paleontology

CLASS Mammalia Linnaeus, 1758

SUBCLASS Theria Parker and Haswell, 1897
INFRACLASS Tribosphenida McKenna, 1975
SUPERCOHORT Eutheria Gill, 1872

COHORT Epitheria McKenna, 1975

ORDER Taeniodonta Cope, 1876

FAMILY Stylinodontidae Marsh, 1875

TRIBE Ectoganini Cope, 1876 (Schoch, 1983a)
GENUS Ectoganus Cope, 1874

Ectoganus gliriformis Cope, 1874

Ectoganus gliriformis lobdelli (Simpson, 1929)
Schoch, 1981

(Fig. 1A-E)

Referred Specimen

ChM PV2926 (Charleston Museum,
Paleontology, Vertebrate), left P, or P,.

Horizon and Locality

Collected from upper Paleocene strata
belonging to the lower—upper Paleocene Black
Mingo Group, Santee Rediversion Canal
hydroelectric turbine pit, approximately 0.5
miles (0.8 km) north of St. Stephen, lat 33°30’
N, long 80°0' W, Berkeley County, South
Carolina, by Dawn Hepler, 11 April 1981. None
of the specimens described here were found
in situ; all came from spoil heaps resulting
from the excavation of the hydroelectric
turbine pit. It is probable that all of the land-
mammal material originated from a sand bed

approximately 18 to 59 feet (5.4 to 17.9 m)
above the base of the Black Mingo Group as
exposed at this locality. This is the youngest
fossiliferous horizon in the pit.

The stratum from which the land mammals
probably came contains dinoflagellates in its
lower part which are most comparable to the
forms of the Nanafalia-Tuscahoma formations
of the Gulf Coast and the Paspotansa
Member of the Aquia Formation in the
northern Atlantic Coastal Plain. The
dinoflagellates from near the top of this
stratum may be age compatible with the lower
assemblage, but it is entirely possible that
they could represent a somewhat younger
age equivalent to the Bashi and Hatchetigbee
formations of the Gulf Coast and the lower
member (Potapaco) of the Nanjemoy
Formation in the northern Atlantic Coastal
Plain (Lucy E. Edwards, written
communication, 1981). This stratum yielded no
diagnostic nannofossils at this site, but in the
canal dug east from the turbine pit
nannofossils were recovered from what
appeared to be the lower part of the
equivalent (but less leached) horizon. That
floral assemblage probably represents NP 7
(nannoplankton zone 7) or NP 8 (Laurel Bybell,
written communication, 1981). Together, these
floras indicate that the lower part of the
mammal-bearing stratum is late Paleocene in
age (NP 7/8) and the upper part is late
Paleocene (NP 9) to perhaps very early
Eocene (NP 10 equivalent) in age (Curry and
Odin 1982, Papp 1979: Papp places the
Paleocene-Eocene boundary in the lower third
of NP 12, whereas some other workers place
it at the top of, or within, NP 10). This interval
(NP 9-10) may correlate with supposed
“earliest Eocene” (North American late
Clarkforkian, early Wasatchian; European
Sparnacian) land-mammal faunas of western
North America and Europe (Savage and
Russell 1983, p. 46; see also Curry and Odin
1982, p. 624, fig. 5). Based on correlations to
marine paleoplanktonic stratigraphy the
Paleocene-Eocene boundary in western North
America may fall within the Wasatchian land-
mammal “‘age,"’ perhaps near the
Graybullian-Lysitean boundary (Lucas 1984)

4 Paleocene Land-Mammals
of South Carolina

or possibly later in the Wasatchian (Savage
and Russell 1983).

For a recent discussion of the Black Mingo
Group in South Carolina, see Van
Nieuwenhuise and Colquhoun (1982a, b). The
late Paleocene to possibly very early Eocene
age of this stratum indicates that it belongs in
their Williamsburg Formation.

Description

ChM PV2926 Is a left lower molariform tooth
bearing a well-developed trigonid anteriorly
and a well-developed talonid posteriorly.
Although the base of the enamel and root are
broken and lost, the tooth appears to have
been moderately hypsodont and bore a
single, large root below. Around the posterior
and lingual sides of the talonid the enamel,
which is approximately 1.0 mm thick, has
been lost. Where preserved unworn, the
enamel bears very fine horizontal (parallel to
the tooth row) striations.

The trigonid of ChM PV2926 is wider and
higher than the talonid. The maximum width of
the trigonid is 14.0 mm (=maximum width of
tooth); the maximum preserved width of the
talonid (including 1.0 mm estimated thickness
of missing enamel) is 12.5 mm. The maximum
preserved length of ChM PV2926 (not
including an estimate for lost enamel) is 14.4
mm.

The trigonid bears a large and high
protoconid and metaconid which are equal in
size and connected by a blunt, transverse
crest. On the anterior face of ChM PV2926 is
a small but distinct paraconid. The trigonid
bears no cingulids or accessory cusps.

The talonid of ChM PV2926 bears a
moderate-sized hypoconid labially and a lower
entoconid lingually. These two cusps are
incorporated into the smooth, posteriorly
convex postcristid which forms the bulk of the
talonid proper. The enclosed talonid basin is
small and shallow. The hypoconid proper is
appressed against the middle of the posterior
face of the protoconid and the preserved
apex of the hypoconid is approximately 4.0
mm lower than the preserved apex of the
protoconid. The entoconid proper is

Postilla 196

appressed against the posterolingual base of
the metaconid and the apex of the entoconid
is approximately 7.5 mm lower than the apex
of the metaconid. The talonid bears no
preserved cingulids or accessory cusps.

Discussion

ChM PV2926 is identical in size and
morphology to previously described P, and P,
of the taeniodont Ectoganus gliriformis
(Schoch 1981, 1982, 1983b, in press). In M,_,
of Ectoganus gliriformis the trigonids and
talonids are subequal in size, whereas in P3_,
the talonids are slightly smaller and lower than
the trigonids as in ChM PV2926. P, and P, of
Ectoganus, however, are virtually identical in
size and morphology and it is not possible to
distinguish these teeth from one another in
isolation (Schoch 1983b); thus ChM PV2926
may represent a P, or P, of Ectoganus
gliriformis. The P,-M, trigonids of Ectoganus
gliriformis lobdelli bear small, but distinct,
paraconids as in ChM PV2926. Such
paraconids are either extremely minute or
lacking in Ectoganus gliriformis gliriformis
(Schoch 1983b).

Cohort Epitheria McKenna, 1975
MIRORDER ?Uintatheriamorpha Schoch, 1983a
ORDER Incertae sedis

FAMILY Mingotheriidae Schoch, new family
Type Genus

Mingotherium Schoch, new genus.
Included Genera

Only the type genus.

Distribution

Upper Paleocene of South Carolina.

Diagnosis

Same as that for the type genus, given below.

5 Paleocene Land-Mammals
of South Carolina

Postilla 196

Mingotherium Schoch, new genus
Type Species

Mingotherium holtae Schoch, new species.

Included Species

Only the type species.

Distribution
Upper Paleocene of South Carolina.
Etymology

Mingo after the Black Mingo Formation, from
which the genoholotype came, and therium
(from Greek therion = beast).

Diagnosis

Moderate-sized epitheres in which M'? (=M'
or M?, i.e., anterior upper molars) bear distinct,
well-separated, connate, subequal, far labially-
placed paracones and metacones and large,
far lingually-placed protocones; parastyles,
metastyles and hypocones entirely lacking;
M'? bear heavy, well-developed, subequal
anterior and posterior cingula which are
connected labially by poorly-developed labial
cingula, but do not contact lingually; M'* each
bear two moderate-sized, labially-placed roots
below the paracone and metacone
respectively and a single large, lingually-
placed root below the protocone; M'?
characterized by moderate crown hypsodonty
in which enamel extends farther up the single
lingual root than the labial roots.

Mingotherium holtae Schoch, new
species

(Fig. 2A-F)

Holotype

ChM PV4113, right M' or M?.

Horizon and Locality of the Holotype

Collected from upper Paleocene Williamsburg
Formation strata of the Black Mingo Group,
Santee Rediversion Canal hydroelectric
turbine pit, approximately 0.5 miles (0.8 km)
north of St. Stephen, lat 33°30’ N, long 80°0’
W, Berkeley County, South Carolina, by Doris
Holt, 30 February 1982.

Hypodigm

Known only from the holotype.
Etymology

Named for the collector, Doris Holt.
Diagnosis

Same as that for the genus, given above.
Description

ChM PV4113 is a large (maximum length =
14.8 mm; maximum width = 24.2 mm) upper
molariform tooth. The well-developed
tribosphenic (paracone, metacone, protocone)
morphology indicates that it is a molar rather
than a premolar. The nearly bilateral symmetry
of the tooth (relative to a transverse plane
running between the paracone and metacone
and through the middle of the protocone)
indicates that this tooth is an M' or M? rather
than an M°. Based on the relatively
generalized morphology of ChM PV4113, in
analogy with other mammals, it is expected
that the M' and M? of Mingotherium holtae are
nearly identical in morphology. Based on the
position of the presumed paracone, which is
set slightly labial of the presumed metacone,
ChM PV4113 is interpreted as a tooth from
the right side of the upper jaw.

Labially, ChM PV4113 bears a large,
anteriorly-placed paracone and a large,
posteriorly-placed metacone. These cones are
both conical, moderately high, well developed,
distinct, subequal in size and set against the
far labial edge of the tooth such that there is
virtually no stylar shelf. As stated above, the

Paleocene Land-Mammals Postilla 196
of South Carolina

7 Paleocene Land-Mammals Postilla 196
of South Carolina
paracone is positioned very slightly labial of Discussion

the metacone. Between the paracone and
metacone is a very small, low mesostyle. ChM
PV4113 bears a very low, poorly-developed
labial cingulum (ectocingulum) which wraps
around the anterolabial and posterolabial
corners of the tooth to connect with the
distinct anterior and posterior cingula
respectively. This cingular border of ChM
PV4113 does not form a distinct parastyle or
metastyle.

Lingually, ChM PV4113 bears a large,
distinct, far lingually-set protocone. The worn,
but distinct, preprotocrista runs from the apex
of the protocone to the anterolingual base of
the paracone and the worn, but distinct,
postprotocrista runs from the apex of the
protocone to the posterolingual base of the
metacone. These two cristae define the trigon
basin. Anterolingually and posterolingually
ChM PV4113 bears well-developed anterior
and posterior cingula respectively. These
cingula do not make contact around the
lingual face of the protocone.

ChM PV4113 bears two moderate-sized
roots labially, supporting the paracone and
metacone respectively, and a large root
lingually under the protocone. ChM PV4113
shows moderate crown hypsodonty and is
characterized by enamel that extends slightly
further up the protocone root lingually than
the paracone and metacone roots labially.
Where unworn, the enamel of ChM PV4113 is
very slightly rugose.

<4 Fig. 2

Mingotherium holtae Schoch, new genus and
species, ChM PV4113, (A-F) and Tribosphenida
incertae sedis, ChM PV2927, (G-/): A)
stereophotograph of occlusal view of right M’ or M?;
B) anterior view of right M' or M?; C) posterior view
of right M' or M2; D) root view of right M' or M?; E)
labial view of right M' or M?; F) lingual view of right
M' or M2; G) lingual view of left lower molariform; H)
labial view of left lower molariform; /)
stereophotograph of occlusal view of left lower
molariform. A-F x 1.25. G-I x2.0.

Mingotherium holtae is a highly distinctive
taxon that is not readily referable to any
known family or order. It is primitive in
retaining a simple tribosphenic (trituberculate)
upper molar crown morphology composed of
a simple paracone and metacone labially and
a simple protocone lingually (see McKenna
1975 for a discussion of character-state
morphocline polarities among primitive
mammals). The reduced stylar shelf and far
lingual positioning of the protocone are
probably derived character-states in
Mingotherium, but are of little help in
determining the affinities of this genus as
similar character-states of the primary cones
have probably been derived independently in
a number of groups (e.g., Taeniodonta,
Schoch 1983b; Primates, Szalay and Delson
1979; Condylarthra and Insectivora, Matthew
1937; Idiogenomys, Ostrander 1983:
Pseuaictops, Sulimski 1969; Dinocerata, Flerov
1967, Wheeler 1961; Tillodontia, Gazin 1953;
Mesonychidae, Szalay and Gould 1966).
Mingotherium bears the further derived
character-state of extremely well developed,
nearly symmetrical anterior and posterior
cingula on the upper molars. This same
combination of derived features (reduced
Sstylar shelf, lingual positioning of the
protocone, well-developed anterior and
posterior cingula) is seen in the Mongolian late
Paleocene genus Pseudictops Matthew,
Granger and Simpson, 1929 (Sulimski 1969).
Pseuadictops is also similar to Mingotherium in
being characterized by a moderate degree of
crown hypsodonty, in lacking true hypocones
and in having anterior and posterior cingula
which do not meet lingual of the protocone.
Pseuaictops, however, differs significantly
from Mingotherium in possessing well-
developed paralophs and metalophs (derived)
on the upper cheek teeth.

Pseudictops is an epithere (nonedentate
eutherian) of uncertain affinities. Sulimski
(1969, p. 107) referred the monogeneric family
Pseudictopidae to “‘Eutheria, Order incertae
sedis’’ and suggested that it may represent a
new order of mammals. Previously, Van Valen

8 Paleocene Land-Mammals
of South Carolina

(1964) had suggested that Pseudictops may
be close to the ancestry of the Lagomorpha.
Szalay and McKenna (1971) erected the new
order Anagalida for the families
Zalambdalestidae, Pseudictopidae,
Anagalidae and Eurymylidae and suggested
that this order may have been ancestral to the
Lagomorpha. McKenna (1975) included the
Pseudictopidae in the Lagomorpha, but
McKenna (1982) excluded pseudictopids from
the Lagomorpha. Most recently Lucas and
Schoch (1982; see also Tong and Lucas 1982)
have pointed out that Pseudictops shares
many derived character-states with the orders
Dinocerata (=uintatheres; Paleocene-Eocene
of Asia and western North America: see
Wheeler 1961) and Xenungulata (late
Paleocene of South America: see Paula Couto
1952) and may represent the sister-taxon of
Dinocerata plus Xenungulata. As noted above,
Mingotherium shares a number of derived
character-states with Pseudictops and thus
may have been part of a late Paleocene-early
Eocene dinoceratan/xenungulate/
pseudictopid/Mingotherium
(Uintatheriamorpha) radiation in Asia and the
Americas.

Tribosphenida incertae sedis
Genus and Species Indeterminate A
(Fig. 2G-l)

Referred Specimen

ChM PV2927, talonid and root of left lower
molariform tooth.

Horizon and Locality

Collected from upper Paleocene Williamsburg
Formation strata of the Black Mingo Group,
Santee Rediversion Canal hydroelectric
turbine pit, approximately 0.5 miles (0.8 km)
north of St. Stephen, lat 33°30’ N, long 80°0’
W, Berkeley County, South Carolina, by Dawn
Hepler, 30 May 1981.

Postilla 196

Description

ChM PV2927 is a medium-sized left lower
molariform tooth of which a single root and
talonid are preserved. The maximum width of
the talonid is 6.3 mm; the maximum preserved
length of the tooth is 8.8 mm; the maximum
preserved height of the root and crown is 15.0
mm and the maximum preserved height of the
enamel crown measured on the labial face is
4.5 mm.

The single root of ChM PV2927 is
compressed laterally (its maximum labial-
lingual width is 3.9 mm), extends straight
down vertically and converges to a sharp
point. The tooth crown Is relatively bunodont
(low-crowned). Where unworn, the enamel is
very slightly rugose. The enamel has been
worn smooth over most of the preserved
surface of the tooth.

Anteriorly, the entire trigonid was broken off
postmortem and lost. However, there is no
indication that a second, more anteriorly-
placed root was ever present on ChM
PV2927. As the single preserved root is
directed straight down, rather than directed
posteriorly, it is probably the sole root of ChM
PV2927 and supported both the talonid and a
short trigonid. The original entire length of
ChM PV2927 may have been only 9 or 10 mm.

Posteriorly, ChM PV2927 bears a well-
developed, but heavily worn, talonid. A
distinct hypoconid is borne on the
posterolabial corner of the talonid, and a
slightly smaller but distinct entoconid is borne
on the posterolingual corner of the tooth.
These two conids are connected by a smooth
(although worn), transverse postcristid. On the
postcristid there may be a small hypoconulid
just labial of, and closely approximated to, the
entoconid. If this ‘‘hypoconulid”’ is real, it is
badly obscured by wear. Alternatively, this
apparent, faint “‘hypoconulid’’ may be merely
an artifact of wear on the postcristid. A
distinct cristid obliqua, which is as high as the
hypoconid, runs from the apex of the
hypoconid to the presumed posterolabial base
of the protoconid. There is a very slight, low
cingulid just labial of the cristid obliqua. An
entocristid is not developed on ChM PV2927

9 Paleocene Land-Mammals
of South Carolina

Postilla 196

SSS EEE ESS SS ee ee ee ee

and the postcristid and cristid obliqua alone
enclose the shallow talonid basin.

Discussion

Due to the incomplete and poorly preserved
condition of ChM PV2927, very little can be
concluded regarding this tooth. The
placement of ChM PV2927 in the tooth row
cannot even be established with certainty.
The large, laterally compressed root suggests
that it may be an M,, but the straight,
transverse postcristid suggests that it may be
a more anterior tooth. If ChM PV2927 originally
bore only a single root, this suggests that it
may be a molariform premolar.

The talonid of ChM PV2927 bears the
tribosphenic configuration of cristid obliqua,
hypoconid, postcristid, entoconid (Bown and
Kraus 1979) and thus it pertains to either a
marsupial or a placental. If the talonid really
does bear a hypoconulid which is closely
approximated to the entoconid (see
description above), this would suggest
marsupialian affinities for ChM PV2927
(Clemens 1979). If not, ChM PV2927 is so
poorly known that it could conceivably pertain
to almost any known eutherian order. ChM
PV2927 represents an animal that was
considerably smaller than Mingotherium
holtae.

Mammalia incertae sedis
Genus and Species Indeterminate B
(Fig. 1F-l)

Referred Specimen
ChM PV2924, a caniniform tooth.
Horizon and Locality

Collected from upper Paleocene Williamsburg
Formation strata of the Black Mingo Group,
Santee Rediversion Canal hydroelectric
turbine pit, approximately 0.5 miles (0.8 km)
north of St. Stephen, lat 33°30’ N, long 80°0’
W, Berkeley County, South Carolina, by Vance
McCollum, April 1981.

Description

ChM PV2924 is a stout caniniform tooth which
is single-rooted and very slightly curved. The
crown end is badly broken, but does preserve
a small portion of enamel base. When holding
the tooth such that the convex edge (Fig. 11)
faces away from the viewer (Fig. 1G), the
base of the enamel crown extends slightly
farther down the left side of the tooth than
the right side. Thus, when oriented in this
position, the left side is probably the lateral
side of the tooth and the convex edge of the
tooth is the anterior face. Accordingly, ChM
PV2924 is either a left lower caniniform tooth
Or an upper right caniniform.

The maximum preserved length of ChM
PV2924 (apex of crown to tip of root) is 39.2
mm. The maximum dimensions of the root in
cross-section are 14.6 mm anteroposteriorly
by 11.0 mm mediolaterally. The maximum
preserved crown height is approximately 12.0
mm. The crown appears to have come to a
simple point. There is a very slight cingulum/
cingulid on the posterior base of the crown.
The enamel is very slightly rugose where
preserved in relatively unworn condition.

Discussion

ChM PV2924 probably represents a true
canine, but there is also the possibility that it
represents a caniniform incisor or premolar. In
isolation a caniniform tooth such as ChM
PV2924 is very difficult to assign to a low-level
taxon; the difficulties are compounded by the
damaged nature of the tooth. ChM PV2924 is
a relatively large tooth and only a few groups
of mammals are known from the late
Paleocene and early Eocene which could
accommodate a canine this size (see Savage
and Russell, 1983, for faunal lists). Among the
large-bodied mammals of this time are
taeniodonts (Schoch 1983b), pantodonts
(Simons 1960), uintatheres (Wheeler 1961) and
certain large condylarths (Matthew 1937, Rose
1981). ChM PV2924 is unlike the large gliriform
canines of taeniodonts, but the possibility that
it represents one of the other orders cannot
be excluded. Finally, it should be noted that

10 Paleocene Land-Mammals
of South Carolina

Fig. 3

Mammalia incertae sedis, ChM PV4092, (A-D). A)
dorsal view of left parietal, anterior to left; B) lateral
view of left parietal, anterior to left; C) ventral view
of left parietal, anterior to left; D) medial view of left
parietal, anterior to right. All figures <0.95.

both ChM PV2924 and ChM PV4113 represent
relatively large mammals, and ChM PV2924
may be a canine of Mingotherium holtae.

Mammalia incertae sedis
Genus and Species Indeterminate C

(Fig. 3)

Referred Specimen

ChM PV40292, left parietal.

Postilla 196

Horizon and Locality

Collected from upper Paleocene Williamsburg
Formation strata of the Black Mingo Group,
Santee Rediversion Canal hydroelectric
turbine pit, approximately 0.5 miles (0.8 km)
north of St. Stephen, lat 33°30’ N, long 80°0’
W, Berkeley County, South Carolina, by Vance
McCollum, May 1981.

Description

ChM PV4092 is a thick, massive bone of the
posterior skull roof which | interpret as a left

11 Paleocene Land-Mammals
of South Carolina

Postilla 196

——— a ee

parietal. Its maximum preserved length is
approximately 75.0 mm. Only one original
articular surface of ChM PV4092 is preserved;
all of the rest have been broken off and lost.
The articular surface which remains preserves
a thickened sutural area (22.0 mm thick: Fig.
3D) which | interpret as the sagittal (middorsal
line) articulation of ChM PV4092 with its mate
on the other side. One side or surface (Fig.
3A) of ChM PV4092 is relatively flat and
roughly triangular-shaped; this surface is
perpendicular to the medial articular surface
and is thus interpreted as the dorsal surface
of the parietal. The dorsal surface is bounded
laterally by a prominent natural ridge which
appears to represent part of a parasagittal
crest. The parasagittal crest coverges toward
the midline of ChM PV4092 at one end (on the
right side as viewed in Figure 3A); this
convergence of the parasagittal crest toward
the midline marks the posterior part of the
parietal. Laterally the parasagittal crest
overhangs very slightly the more
posteroventral and lateral aspect of the
parietal. Seen in lateral view (Fig. 3B), the
anterolateral aspect of the parietal forms a
semicircle and is slightly concave; this area
may have formed part of the posterior orbital
region. The posterolateral aspect of the
parietal is smoothly convex and formed part
of the outer skull roof surface. Seen in ventral
view (Fig. 3C) the parietal is slightly concave
and appears to be pierced by several small
foramina.

Discussion

ChM PV4092 conforms in morphology to a
mammalian left parietal. It does not appear to
pertain to a reptile (specifically a crocodilian)
or other lower vertebrate as it lacks any
surface sculpturing. By late Paleocene-early
Eocene standards, ChM PV4092 pertains to a
relatively large mammal, and the animal it

belonged to had a set of moderately-
developed parasagittal crests. These features
suggest that ChM PV4092 may represent a
uintathere (Wheeler 1961) or a pantodont
(Simons 1960). The possibility also exists that
ChM PV4092 may pertain to Mingotherium
holtae.

Summary

Only two of the five specimens which
compose the Black Mingo local land-mammal
fauna (here named) are diagnostic of a
taxonomic category at the species level. ChM
PV2926 records a considerable geographic
range extension of the late Paleocene
taeniodont Ectoganus gliriformis lobdelli:
previously this taxon was known only from
Colorado, Montana and Wyoming (Schoch
1983b). ChM PV4113 represents a distinctive
new taxon, Mingotherium holtae, which may
have affinities with the Mongolian
Pseudictops, with the uintatheres of western
North America and Asia, and with the South
American xenungulates. ChM PV2927 can only
be classified as ‘‘Tribosphenida incertae
sedis." ChM PV2924 and ChM PV4092 can
only be classified as ‘Mammalia incertae
sedis’ at the present time, although there is
the distinct possibility that they may pertain to
Mingotherium holtae.

Acknowledgments

| thank Albert E. Sanders and Robert E.
Weems for making the study specimens
available to me and for providing locality
information. | thank Leigh M. Van Valen for
comments on the affinities of the Black Mingo
local land-mammal fauna. | thank A. Novick, J.
Ostrom, C. Pettit, C. Sibley, B. Tiffney and R.
Weems for reviewing the final manuscript.

12 Paleocene Land-Mammals Postilla 196
of South Carolina

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The Author

Robert Milton Schoch. Department of
Geology and Geophysics and Peabody
Museum of Natural History, Divisions of
Vertebrate Paleontology and Paleobotany,
Yale University, 170 Whitney Avenue, P.O. Box
6666, New Haven, CT 06511. Present address:
Division of Science, College of Basic Studies,
Boston University, 871 Commonwealth
Avenue, Boston, MA 02215.

Erratum for Postilla 191

In Postilla 191 [J. D. Archibald, R. M. Schoch
and J. K. Rigby, Jr. 1983. A new subfamily,
Conacodontinae, and a new species,
Conacodon kohibergeri, of the Periptychidae
(Condylarthra, Mammalia). 24 p.] it was
incorrectly reported that a joint Yale-U.S.
Bureau of Land Management study of the
stratigraphic position of lower Paleocene
mammal-bearing localities in the San Juan
Basin, New Mexico, was undertaken during
the summer of 1981. This study actually took
place during the summer of 1980 and the
holotype of C. kohlbergeri was collected by R.
M. Schoch on 21 June 1980.

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