Cretaceous Mammals of Southern Utah. III. Therian Mammals from the Turonian (Early Late Cretaceous)

Cretaceous Mammals of Southern Utah. III. Therian Mammals from the Turonian (Early LateCretaceous)Author(s): Richard L. CifelliSource: Journal of Vertebrate Paleontology, Vol. 10, No. 3 (Sep. 20, 1990), pp. 332-345Published by: Taylor & Francis, Ltd. on behalf of The Society of Vertebrate PaleontologyStable URL: http://www.jstor.org/stable/4523329 .

Accessed: 11/07/2014 10:16

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

The Society of Vertebrate Paleontology and Taylor & Francis, Ltd. are collaborating with JSTOR to digitize,preserve and extend access to Journal of Vertebrate Paleontology.

http://www.jstor.org

This content downloaded from 2.26.89.247 on Fri, 11 Jul 2014 10:16:45 AMAll use subject to JSTOR Terms and Conditions

http://www.jstor.org/action/showPublisher?publisherCode=taylorfrancis

http://www.jstor.org/action/showPublisher?publisherCode=vertpaleo

http://www.jstor.org/stable/4523329?origin=JSTOR-pdf

http://www.jstor.org/page/info/about/policies/terms.jsp


Journal of Vertebrate Paleontology 10(3):332-345, September 1990 @ 1990 by the Society of Vertebrate Paleontology

CRETACEOUS MAMMALS OF SOUTHERN UTAH. III. THERIAN MAMMALS FROM THE TURONIAN (EARLY LATE CRETACEOUS)

RICHARD L. CIFELLI Oklahoma Museum of Natural History and Department of Zoology,

University of Oklahoma, Norman, Oklahoma 73019

ABSTRACT-Eight taxa of therian mammals are herein recorded from the Smoky Hollow Member of the Straight Cliffs Formation, southcentral Utah. The assemblage is of middle to late Turonian age (early Late Cretaceous), a time period for which mammals are poorly represented worldwide in the fossil record. Two symmetrodonts, family Spalacotheriidae, are described as new; one is referred to the genus Symmetrodontoides, otherwise known from the early Campanian, and the other is placed in a new genus. Primitive tribosphenic taxa include two archaic forms characterized by single rank molar shearing; one is referred to the Deltatheridiidae and the other, of uncertain affinities, is similar to Picopsis of the early Campanian. A new species is tentatively referred to Anchistodelphys. This genus is marsupial-like in having an anteroposteriorly expanded protocone and, especially, in features of the lower molars (lingually placed paraconid and hypoconulid, reduced height differential between trigonid and talonid, presence of labial postcingulid) but lacks specializations of the stylar shelf thought to characterize marsupials, suggesting that acquisition of stylar cusps C and D occurred later in the evolution of marsupials than did the above-mentioned characters. Three unidentified and unnamed marsupial taxa are also present in the fauna. Evidence of some marsupial diversification in North America by the Turonian, the presence on the continent of primitive marsupial and marsupial-like taxa (depending upon how the group is defined), and the hypothesized derivation of South American and Australian taxa from an Alphadon-like form, suggest that marsupial origination in North America, followed by dispersal to South America, may be the simplest explanation for the temporal and geographic distribution of the group.

INTRODUCTION

Tribosphenic mammals, including placentals, marsupials, and their presumed allies, "therians of metatherian-eutherian grade" (Patterson, 1956), are defined by the possession of upper molars with a protocone and lower molars with a basined, three-cusped talonid (Simpson, 1936; Crompton, 1971). The early history of these taxa, representing the initial radiations of higher mammals, is very poorly documented. The earliest and most primitive form, Aegialodon dawsoni, is known by a single, worn lower molar of Valanginian age from England (Kermack et al., 1965). Early Cretaceous rocks in Asia have produced remains of tribosphenic mammals, including a suspected close ally of Aegialodon (Dashzeveg and Kielan-Jaworowska, 1984) and, apparently, the earliest placentals (Kielan-Jaworowska et al., 1979; Lillegraven et al., 1987), although these latter have not been fully described or illustrated. A diverse and well-represented array of eutherians and metatherian-eutherian grade mammals is known from the Late Cretaceous of Asia (Clemens et al., 1979). The age of the deposits containing the mammalian faunas is highly controversial (see summary by Lillegraven and McKenna, 1986), but it is apparent that a significant hiatus separates known Early and Late Cretaceous mammal assemblages of Asia. The situation is similar in North America. Cretaceous mammals are known

primarily from the northcentral Rocky Mountain region, where they are recorded in a relatively complete sequence of faunas, grouped into land mammal ages (Russell, 1975; see Lillegraven and McKenna, 1986) from about the beginning of the Campanian (recognized by marine criteria) onwards. The oldest Late Cretaceous mammalian local fauna is that from the upper Milk River Formation of Alberta, which records the presence of archaic therian groups, including "acute- angled" symmetrodonts (Fox, 1976, 1985), "obtuse- angled" symmetrodonts (Fox, 1984a), triconodonts (Fox, 1969), and various metatherian-eutherian grade taxa (Fox, 1972, 1980, 1982), as well as marsupials (Fox, 1971) and placentals (Fox, 1984b). The Wah- weap Formation of southern Utah has produced a similar assemblage, and may also be Aquilan in age (Cifelli and Madsen, 1986; Eaton and Cifelli, 1988; Cifelli, 1990b, c). However, very little is known prior to the Campanian. Eight therian taxa have been described from the Albian of north Texas (Patterson, 1955; Slaughter, 1971; Butler, 1978). The pre-Aquilan Cre- taceous record for North America is otherwise a virtual blank, consisting of one described species from the Cloverly Formation (Jenkins and Schaff, 1988), one from the Dakota Formation (Cifelli and Eaton, 1987), and several reports of unidentified materials (Clemens et al., 1979; Krause and Baird, 1979; Emry et al., 1981). This gap in the fossil record is unfortunate indeed, for

332



CIFELLI- TURONIAN THERIANS FROM UTAH 333

it corresponds to the time of earliest radiation and diversification of advanced mammals. In this context, even poorly preserved fossils fitting within this "twi- light zone" (Lillegraven, 1969) are of great interest to students of mammalian evolution. Herein is reported the first therian mammalian assemblage from the North American Turonian (early Late Cretaceous). Although known materials are highly fragmentary and most taxa cannot yet be fully identified or adequately diagnosed as new, they bear witness to a diverse fauna of therian mammals, both tribosphenic and non-tribosphenic.

As preserved and exposed in the Kaiparowits region of southcentral Utah, the Cretaceous System includes (in ascending order) the Dakota, Tropic, Straight Cliffs, Wahweap, Kaiparowits, and Canaan Peak formations (Gregory and Moore, 1931; Peterson, 1969a; Bowers, 1972). Four members of the Straight Cliffs Formation, which overlies the late Cenomanian to middle Turoni- an Tropic Formation (a marine shale), are recognized (Peterson, 1969b); collectively, they comprise about 500 m of sedimentary rocks. The lowest unit, the Tib- bet Canyon Member, is a nearshore regressive marine sandstone and, based on marine invertebrates, is of middle Turonian age (Peterson, 1969a). The overlying Smoky Hollow Member, of non-marine origin, con- sists predominantly of siltstones, carbonaceous clay- stones, and interbedded coals. The age of the Smoky Hollow Member remains to be directly established, but based on constraints of the underlying Tibbet Canyon Member and the overlying John Henry Member, the Smoky Hollow is considered to be middle to late Tu- ronian (Peterson, 1969a). The John Henry Member overlies the Smoky Hollow Member in apparent un- conformity (Peterson, 1969a, b), and the duration not represented is unknown. However, the basal John Hen- ry is of marine origin and contains an early Coniacian molluscan fauna (Eaton, 1987).

Fossil mammals described herein were recovered from two localities in the Smoky Hollow Member of the Straight Cliffs Formation, OMNH (Oklahoma Mu- seum of Natural History) locality V4 and MNA (Mu- seum of Northern Arizona) locality 995. Both sites are near Henrieville, Garfield County, Utah; precise co- ordinates are on file at the respective institutions. Spec- imens were recovered by underwater screenwashing of rock matrix. Fine mesh (0.305 mm) screens were employed; their use in such operations is advocated in- sofar as some of the complete teeth recovered have a maximum dimension of scarcely more than 0.6 mm.

Measurements and Abbreviations

Dental measurements were taken with a Reflex Mi- croscope and are as described by Lillegraven and Bie- ber (1986). Measurements are in millimeters and are abbreviated as follows (Lillegraven and McKenna, 1986): AP--anteroposterior length, ANW -anterior width (trigonid width of lower molars; greatest width of teeth with only one width measurement), POW -- posterior width (talonid width of lower molars).

Institutional abbreviations are as follows: AMNH, American Museum of Natural History, New York; MNA, Museum of Northern Arizona, Flagstaff; OMNH, Oklahoma Museum of Natural History, Uni- versity of Oklahoma, Norman; UALVP, University of Alberta Laboratory for Vertebrate Palaeontology, Ed- monton; ZPAL, Zaklad Paleobiologii, Polish Acade- my of Sciences, Warsaw.

SYSTEMATIC PALEONTOLOGY

Order SYMMETRODONTA Simpson, 1925 Family SPALACOTHERIIDAE Marsh, 1887 Genus SYMMETRODONTOIDES Fox, 1976

SYMMETRODONTOIDES OLIGODONTOS, sp. nov.

(Fig. 1 A-D)

Type Specimen-MNA 5789, posterior right lower molar, probably M7.

Hypodigm - The type, and OMNH 20381, corroded right lower molar, probably M4 or 5

Horizon and Localities--The type was collected at MNA locality 995, in the Smoky Hollow Member of the Straight Cliffs Formation (Turonian, Upper Cre- taceous), Garfield County, Utah. The referred specimen is from OMNH locality V4 in the same unit, Garfield County, Utah.

Diagnosis - Closely similar to Symmetrodontoides canadensis Fox, 1976 and S. foxi Cifelli and Madsen, 1986, but differing from both species in its smaller size. Molar cusps more slender and delicate than in S. canadensis and S. foxi, with anterior cingulum narrower than in corresponding teeth of those species.

Etymology - Oligos, Gr., little or scanty; odontos, Gr., tooth. Allusion is both to the small size of the species and the few known teeth by which it is represented.

Discussion and Description -The temporal and geographic distributions of spalacotheriid symmetrodonts are given in Table 1. With the exception of Spala- cotherium (see Clemens, 1963), the dental series of spalacotheriid symmetrodonts is poorly known. How- ever, lower molars representing at least six loci, probably M2-7, are known for Symmetrodontoides canadensis (Fox, 1976, and pers. obs.). Furthermore, additional materials collected since description of S. foxi by Cifelli and Madsen (1986) add knowledge of the molar series in that species, and substantiate the previously hypothesized positions of described specimens. The type of Symmetrodontoides oligodontos, MNA V5789, is believed to be an ultimate lower molar, perhaps M7 (assuming the species had a dental formula like that of Spalacotherium), based on its close resemblance to MNA V4522 and UALVP 12087, hypothesized to represent M7 of the other described species of Symmetrodontoides, respectively. These teeth are distinguished from those representing more anterior loci in having more anteroposteriorly compressed tri- gonids, taller crowns, a marked height differential between the anterior and posterior parts of the cingulum,






Etymology--Named for Dr. Malcolm C. McKenna,

who helped initiate the field project resulting in recov- ery of mammals from the Cretaceous of southern Utah.

Description-- MNA V5792 is remarkable for its small

size (AP = 0.65; ANW = 0.63), which is even less than the species described above, Symmetrodontoides oligodontos. The tooth is low-crowned relative to comparable teeth of Symmetrodontoides, has a somewhat obtuse trigonid angle, and has anterobasal and posterobasal cuspules at more equivalent heights than teeth representing the more posterior loci in Symmetrodon- toides foxi from the Wahweap Formation. In these respects, it more closely resembles teeth of that species and of S. canadensis thought to represent M4, and the specimen is accordingly hypothesized to belong to that tooth position. The anterobasal and posterobasal cuspules are subequal in size and are well-developed, as are the adjacent parts of the basal cingulum. The lingual cingulum is faint; the labial side of the crown base has been damaged, and it cannot be determined wheth- er the labial cingulum was complete, as in Symmetro- dontoides and Spalacotherium (in contrast to the condition in Spalacotheroides; Fox, 1976). The trigonid cusps are arranged in the form of an isosceles triangle, with the protoconid at the apex. The protoconid is the tallest cusp on the tooth; in contrast to all other known spalacotheriids, paraconid and metaconid are equal in robusticity and height; these cusps are about two-thirds the height of the protoconid, measured from the base of the crown. The protocristid and paracristid are equally developed; a deep but unslotted notch is present in each, about midway from the protoconid. Apical wear is seen on the tip of the protoconid; the specimen is otherwise lightly worn.

Order AEGIALODONTIA Butler, 1978 Family DELTATHERIDIIDAE

Gregory and Simpson, 1926

Unnamed Genus and Species (Fig. 2A-C)

A metatherian-eutherian grade mammal is represented by the front half of a right ?ultimate lower molar, perhaps M4 (OMNH 20386), from OMNH locality V4, Smoky Hollow Member, Straight Cliffs Formation, Garfield County, Utah. It unquestionably represents a species and, probably, genus distinct from all others known, but materials at hand are insufficient to diagnose it adequately. As elaborated in the Discussion, it is referred to the Deltatheridiidae (perhaps including, in part at least, Aegialodontidae) on the basis of its possession of an enlarged paraconid and reduced metaconid, features that appear to be derived within the context of the Tribosphenida. Stagodontid marsupials, probably present in the Smoky Hollow Member of the Straight Cliffs Formation, are also characterized by an enlarged paraconid on lower molars. However, OMNH 20386 is not comparable to lower molars of stagodon- tids or any other marsupials, owing to the extreme reduction of the metaconid, the lack of a fully devel-

oped cristid obliqua (see Fox, 1975), and the apparent proportions of the talonid. The extreme reduction of the metaconid in OMNH 20386 is a point of similarity to M4 in Deltatheridium and Kielantherium (see Butler and Kielan-Jaworowska, 1973; Kielan-Jaworowska, 1975; Dashzeveg and Kielan-Jaworowska, 1984), indicating that the specimen is probably an ultimate molar, which would be M4 if the dental formula was as in those genera. The tooth is larger (ANW = 1.58) than in other deltatheridiids (by comparison, ANW of M4 in Deltatheridium pretrituberculare, ZPAL MGM I/91, is 0.97). The protoconid and paraconid are large, and differ from those of other deltatheridiids in being lanceolate, with curved, crest-bearing edges. The paraconid is about two-thirds the height of the protoconid, measured from the base of the crown. The corresponding keels of the paracristid on the two cusps are sharp and noticeably convex, meeting in a deep, slotted notch about midway between paraconid and protoconid. The paraconid appears to have been at the lingualmost margin of the tooth, and is placed well anterior to the protoconid. The labial faces of both cusps are gently convex. The metaconid is virtually lacking, being developed as a small knob on the lingual face of the protoconid, about half as high as the distance from the crown base to the apex of the paraconid. A weak keel ascends the lingual face of the protoconid from the metaconid. The posterior face of the protoconid also bears a salient, convex keel. This crest descends posteriorly and slightly lingually from the protoconid, and was apparently continuous with the crest linking what- ever talonid cusps were present, a similarity to the condition in the ultimate lower molar of Deltatherid- ium and a point of contrast to primitive Tribospheni- da, in which the metaconid is unreduced (the distal metacristid descends from the apex of the metaconid in these taxa; see Fox, 1975). The talonid is missing and its proportions cannot be determined, but what remains of it indicates that it was extremely low relative to the trigonid and was much narrower than that part of the tooth, as is typical of plesiomorphic Tri- bosphenida.

Order Uncertain Family Uncertain

Genus and Species Undetermined (Fig. 2D-J)

One (or, less probably, two) species of unidentified tribosphenic mammal is represented by molar fragments (OMNH 20030, 20032, 20036, posterolabial part of right Mx; 20035, posterolabial part of left Mx) from OMNH locality V4, Smoky Hollow Member, Straight Cliffs Formation. Although highly fragmentary, these specimens are of interest in that they record the presence of a tribosphenic taxon in which stylar cusps in the C and D position are well-developed, but the stylar shelf is narrowed or lacking entirely labial to the paracone. Until recently, such taxa would with- out hesitation have been referred to the marsupial fam-






stylar shelf is less than in that species or in most Cre- taceous peradectids. OMNH 20035 is somewhat larger than the other specimens, suggesting the possibility that it could represent a different species. However, in known respects it is morphologically similar to the remaining teeth, and OMNH 20035 is more plausibly interpreted as belonging to a large individual or a different tooth locus than the other specimens. The cusps are of robust construction. The metacone, centrocrista, and postmetacrista are heavily worn on all specimens. Strong cusps are present at the margin of the stylar shelf in the C and D positions on all specimens; an ectoflexus is consistently lacking. A faint keel variably (OMNH 20030, 20032, 20036) extends lingually or anterolingually from the base of cusp C. None of the specimens preserves the apex of the paracone, but the remnants of it in OMNH 20030 and 20036 indicate that the paracone occupied a position at the margin of the stylar shelf, so that a stylocone and preparacrista must have been lacking. The protoconal region of the tooth is not completely preserved in any of the specimens. However, OMNH 20032 includes the posterior part of this region of the tooth. The conformation of the tooth margin, the curvature at the base of the crown, and the conformation of the trigon basin all suggest that the protoconal region was narrow, both anteroposteriorly and transversely, and that in occlusal pro- file this part of the molar might have resembled that of a pre-ultimate molar of Deltatheridium or Pota- motelses. The enamel is broken in the region of the metaconule, but enough remains to suggest that this cusp, if present, was either miniscule and rapidly oblit- erated by wear or placed very lingually, near the protocone (or both). No metaconular cristae are present, and there is no labial extension of the postprotocrista past the lingual margin of the metacone base.

Several morphs of tribosphenic mammal lower molars are represented in the existing collections but, because of the small samples, the fragmentary nature of mammalian remains from the Smoky Hollow Member of the Straight Cliffs Formation, and the poor state of knowledge on primitive Tribosphenida, it is not possible to make secure associations of upper and lower molars. However, most of the upper and lower molars from the Smoky Hollow Member fall into discrete size and morphological groups, assumed to represent taxa, and in most cases, reasonable hypotheses regarding associations can be made. In the existing collections, three lower molars (MNA 5636, left

Mx [AP = 2.83; ANW = 1.20; POW = 1.29], locality MNA 995; OMNH 20372, broken right Mx, locality OMNH V4; and OMNH 20379, right ultimate lower molar [AP = 2.56; ANW = 0.98; POW = 1.07], locality OMNH V4) are distinctive in their large size, robusticity, and unusual morphology; in these first two respects, at least, they are appropriate for the upper molar fragments described above, and I hypothesize them to represent the same taxon, assuming that only one species is represented. These lower molars are characterized by the relatively low, robust construction of their crowns and

cusps, with the trigonid not being much higher than the talonid. The angle formed by the trigonid cusps is relatively obtuse, with the paraconid placed well anterior to the protoconid and the metaconid occupying a position posterior to that cusp. The protoconid is the tallest cusp on the tooth; paraconid and metaconid are subequal in height and are both placed at the lingual margin of the tooth. The paracristid and protocristid are both notched, but neither bears a carnassial slot. On OMNH 20372, an oblique, labially directed crest descends the posterior face of the metaconid toward the anterior extremity of the cristid obliqua. This crest delimits the lingualmost extent of occlusion with the paracone and preparacrista of the corresponding upper molar, and thus should be termed the distal metacristid (Fox, 1975). The only specimen that preserves the talonid intact is OMNH 20379. The talonid is much longer than the trigonid, suggesting that the tooth is a last molar. However, the talonid is wider than the trigonid, which is unusual for ultimate lower molars of primitive tribosphenic mammals. A faint oblique ridge descends from the deepest point in the notch of the protocristid in this specimen; a distal metacristid as such cannot be discerned, but the tooth is heavily worn. The talonid is basined and bears three cusps. The hypoconid is the anteriormost and lowest of the talonid cusps; the hypoconulid, which is centrally placed but not projecting at the posterior margin of the tooth, and the entoconid are subequal in height. No postcingulid is present.

?MARSUPIALIA, Family Uncertain

?Genus ANCHISTODELPHYS Cifelli, 1990 ?ANCHISTODELPHYS DELICATUS, sp. nov.

(Fig. 3)

Type Specimen-OMNH 20374, left M2 or 3 lacking the protocone and anterior corner of the stylar shelf.

Hypodigm-The type; OMNH 20375, left M4; and 20034, right M4 (assuming a marsupial dental formula), both lacking the protocone. Also tentatively referred to the species, but not formally included in the hypodigm, are seven lower molars described and listed below.

Horizon and Locality - OMNH locality V4, Smoky Hollow Member, Straight Cliffs Formation; Garfield County, Utah.

Diagnosis - Smallest species of the genus. Etymology-L., tender, dainty, in reference to the

appearance of the teeth. Description-OMNH 20374 (Fig. 3A) and 20375

(Fig. 3B) are both left upper molars and were recovered from the same small matrix lot, representing a fraction of the total collected from the locality. It is possible that they are from the same individual, although this will never be known. The species, as known, is clearly distinct from all described taxa. It is tentatively referred to Anchistodelphys based on close overall similarity and because stylar cusps C and D are variably lacking in the only other species of that genus (A. ar-






ridge borders the labial margin of the stylar shelf, but no cusps or cuspules are present in the C, D, or E positions. M4 (assuming a marsupial dental count) is represented by two specimens (Fig. 3B, C). The only standard measurement that can be taken is AP of OMNH 20034, which is 1.16 mm. The teeth differ in some minor details, but are closely similar in size and morphology. The paracone is the tallest cusp on the tooth; the metacone is small and is placed at the distal margin of the tooth. The parastylar region of the tooth is greatly expanded, with the margin of the stylar shelf tapering inward posteriorly, so that the shelf itself dis- appears adjacent to the middle of the centrocrista. The elongate, trenchant preparacrista extends to a small cusp at the anterolabial corner of the tooth; another small cusp is present immediately posterior to this one. The anterocingulum is strong, as is the paraconule, located at the lingual base of the paracone. The stylar shelf bears a weak labial keel; in one specimen (OMNH 20034), small, irregular cuspules are present on this keel. A sharp ridge descends lingually from the apex of the metacone, turning anteriorly as it approaches the protocone (which is not preserved on available specimens).

Seven isolated lower molars (OMNH 20302, 20377, 20384 [OMNH locality V4], MNA 5668, 5786, 5787, and 5788 [MNA locality 995]), not formally included in the hypodigm, are tentatively referred to the species (Fig. 3D-I). They vary somewhat in details and in size, but on present evidence they are all reasonably interpreted as belonging to the same species. Tooth locus assignment for each is problematic; there is some vari- ation in characters usually employed in determining tooth position (angle formed by trigonid cusps, height of trigonid with respect to talonid, relative talonid length, relative talonid width, projection of cusps at distal margin of talonid), but these are neither of suf- ficient consistency nor difference of expression to allow determination. The lower molars are generally of Al- phadon-like construction (Clemens, 1966; Lillegraven, 1969; Fox, 1979). The trigonid to talonid height differential is less than generally seen among metatherian- eutherian grade or Cretaceous eutherian taxa, and the talonid is as broad or broader than the trigonid. The anterocingulid is generally expressed as a short, oblique crest or knob, extending inferolabially from the notch in the paracristid, rather than as a more extensive, basal ridge seen in Cretaceous peradectids. The protoconid is the tallest cusp; the metaconid is slightly taller and more robust than the paraconid. The paraconid lies at the lingual margin of the tooth, in line with the metaconid and entoconid, and is placed well anterior to the protoconid on all specimens, so that the trigonid is relatively open lingually. The metaconid is placed just posterior to the protoconid. Both paracristid and protocristid are deeply notched. The cristid obliqua attaches to the trigonid below the notch in the protocristid, as is typical of Alphadon-like marsupial lower molars (Clemens, 1966, 1979; Lillegraven, 1969). The entoconid and hypoconid are trenchant and about

TABLE 2. Measurements of lower molars tentatively referred to ?Anchistodelphys delicatus, sp. nov., from localities OMNH V4 and MNA 995, Smoky Hollow Member, Straight Cliffs Formation, Utah. Abbreviations: AP, anteroposterior length; ANW, anterior width; POW, posterior width.

Specimen no. AP ANW POW

OMNH 20302 1.32 0.79 - OMNH 20377 - 0.90 0.94 OMNH 20384 1.35 0.76 0.71 MNA V5668 1.72 0.75 0.86 MNA V5787 - - 0.79 MNA V5788 1.30 0.67 0.70

equal in height; the hypoconulid is lingually placed and "twinned" with the entoconid. A well-marked postcingulid extends inferolabially from the hypoconulid to the base of the hypoconid. Measurements of the lower molars are given in Table 2.

Order MARSUPIALIA Illiger, 1811 Family Uncertain

Unnamed Genus and Species (Fig. 4A-G)

A new taxon is represented by several specimens from the Smoky Hollow Member of the Straight Cliffs Formation, but materials in hand are insufficient to diagnose it adequately. Broken upper molars are known from two loci (OMNH 20029, corroded left M2; 20373, left M3 [Fig. 4A]; both are from OMNH locality V4). The species is larger than ?Anchistodelphys delicatus, described above, but is small nonetheless (AP of OMNH 20373 = 1.65 mm; AP of 20029 = 1.71 mm), being comparable in size to Iqualadelphis lactea Fox, 1987. The paracone is slightly taller than the metacone and tilts labially; the cusps are closely appressed, tall, and sharp, with slightly concave labial faces. The stylar shelf is broad, even in comparison to most Cretaceous peradectids. Cusp A is present at the anterolabial corner of a well developed, flat anterior cingulum. Cusp B is poorly preserved in the two specimens, but enough of it remains in OMNH 20373 to indicate that it was small and anteroposteriorly developed, not conical. The preparacrista descends steeply from the apex of the paracone to the level of the stylar shelf, where it reaches its notch and effectively terminates. An ectoflexus is present in M2 and is strongly developed on M3. Pos- terior to this, an exceptionally tall cusp (poorly preserved in OMNH 20029) is present in the D position. The base of cusp D is conical, but two prominent, flattened surfaces ascend its slopes; one faces posteriorly and the other anterolingually. The margin of the stylar shelf is otherwise featureless; no cusp is present in the C or E positions. The postmetacrista is trenchant, descending vertically from the metacone to a notch at the base of that cusp, then labially to the posterolabial corner of the tooth.

Five isolated lower molars or fragments thereof






intermediate in size (POW = 1.32) between Alphadon marshi and A. wilsoni (see Lillegraven, 1969; Clemens, 1973a), documenting the presence of another unidentified taxon in the fauna.

Family ?Stagodontidae Marsh, 1889

Genus Undetermined (Fig. 4H-J)

A marsupial apparently referable to the Stagodon- tidae is represented by MNA 5652, a ?left ?P3 from MNA locality 995. The tooth (AP = 2.90; ANW = 1.73) is more inflated than those referred to Eodelphis (see Fox, 1981), but less so than in species of Didel- phodon (Fox and Naylor, 1986). The specimen lacks the bilobate appearance of posterior lower premolars typical of Didelphodon. Premolars are not yet known for Pariadens, the oldest member of the family, from the Cenomanian Dakota Formation (Cifelli and Eaton, 1987).

DISCUSSION

Although not yet well-known, the fauna from the Smoky Hollow Member of the Straight Cliffs Forma- tion is of interest in that it documents the presence of a diverse therian mammal assemblage in the Turonian of the southwestern US, one which includes a mixture of non-tribosphenic, primitive tribosphenic, and advanced tribosphenic taxa. Of the eight taxa known, two are spalacotheriid symmetrodonts, three are metatherian-eutherian grade or "marsupial-like," and three are marsupials. Eutheria, which make their first undoubted North American appearance in the Aquilan (Fox, 1984b; Cifelli, 1990c), are not yet known from the Utah sequence lower than the Wahweap Formation.

Spalacotheriid (or "acute-angled") symmetrodonts are first known from the Late Jurassic and apparently persisted until the early Campanian in North America, where the family is represented by two Aquilan species of the genus Symmetrodontoides (Fox, 1976; Cifelli and Madsen, 1986). Spalacotheriids may have been widespread during the Campanian: Groebertherium, described as a dryolestid from the Los Almitos For- mation of Patagonia (Bonaparte, 1986), appears to be referable to the family. The presence of an additional species of Symmetrodontoides in the Turonian extends the range of the genus backward, but adds no information on its relationships (see Fox, 1976, 1985). The new genus Spalacotheridium is divergent from other members of the family in having lower molars with paraconid and metaconid of equal size. S. mckennai is distinctive also in being the smallest known spala- cothere. Its record in the Smoky Hollow Member of the Straight Cliffs Formation adds to the morphological and taxonomic diversity of the family, but little more can be said of it at present.

A distinctive but unnamed taxon, represented by a broken lower molar, is of metatherian-eutherian grade and is most similar to Deltatheridiidae among known

TABLE 3. Measurements of lower molars of Marsupialia, unnamed genus and species, from localities OMNH V4 and MNA 995, Smoky Hollow Member, Straight Cliffs Forma- tion. Abbreviations as in Table 2.

Specimen no. AP ANW POW

OMNH 20016 - 1.12 - OMNH 20017 - 1.12 - OMNH 20380 1.82 0.91 0.98 MNA V5638 1.94 0.98 0.96

forms. The best represented members of the family, Deltatheridium and Deltatheroides, are from the Late Cretaceous of Asia (Kielan-Jaworowska, 1975), but materials possibly referable to the latter genus are known from the Oldman and Lance formations of North America (Fox, 1974). Although primitive in many respects (see discussions by Fox, 1975; Kielan- Jaworowska, 1975), these two genera are distinctive among metatherian-eutherian grade mammals in several aspects of their dental anatomy. Postvallum/prevallid shearing (between postmetacrista and paracristid of upper and lower molars, respectively) is emphasized; thus, in the lower molars, the paraconid is nearly as tall as the protoconid and the metaconid is reduced to absent, particularly on the last lower molar. (A similar tendency, apparently acquired indepen- dently, occurred in the Stagodontidae; see, e.g., Clem- ens, 1979; Fox, 1981). Judged by trigonid morphology of other primitive therian mammals, this condition appears to be derived within the Tribosphenida (Clem- ens and Lillegraven, 1986). It is worth noting that this configuration of the lower molar trigonid is also seen in posterior lower molars of Kielantherium, from the Early Cretaceous of Asia, which is regarded as being closely similar to, if not congeneric with, Aegialodon (Fox, 1976, 1980; Clemens et al., 1979; Dashzeveg and Kielan-Jaworowska, 1984). These taxa are obviously very primitive in the weak development of lower molar talonids, but in the development of trigonid cusps, Kielantherium, at least, may depart from a morphotype for the Tribosphenida and, perhaps, may share derived morphology with the Deltatheridiidae. The Smoky Hollow taxon is too poorly known to assist in phylo- genetic interpretation of these mammals. In its large size, lanceolate paraconid and protoconid, and extremely reduced metaconid, it would appear to be advanced relative to most of the taxa under consideration.

Also poorly known and of even more enigmatic affinities is a second unnamed metatherian-eutherian grade taxon from the Smoky Hollow Member of the Straight Cliffs Formation, represented by upper molar fragments and, possibly, several lower molars. Com- parison with pediomyid marsupials is invited, because they share a reduced anterior stylar shelf; in addition, the robustness of the tooth cusps and the presence of well developed cusps in the C and D positions are



342 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 10, NO. 3, 1990

resemblances to various Late Cretaceous marsupials among the Pediomyidae and (except for the reduced stylar shelf) Peradectidae. However, a reduced anterior stylar shelf is also found in several metatherian-eutherian grade taxa and other evidence suggests the possibility that this condition may have evolved two or more times among taxa now referred to the Pediomy- idae, implying polyphyly of the family (Fox, 1987b). Furthermore, at least two of the specimens from the Smoky Hollow Member (OMNH 20032, 20036) suggest that upper molar construction in the species they represent may have differed in a fundamental way from that of known Cretaceous marsupials (or eutherians). As detailed by Fox (1975), in these advanced tribosphenic taxa, conules are strong, labially placed (near the bases of paracone and metacone, respectively), and bear wing-shaped cristae that provide for double rank or "en echelon" (Hiiemae and Kay, 1973) shearing with the crests above them. The postmetaconular crista extends posterolabially from the metaconule along the posterior face of the tooth, and is thus confluent with the postprotocrista lingually and the postcingulum labially. The protocone is broad relative to a tribosphenic morphotype as approximated by, for instance, Po- tamotelses (Fox, 1972, 1975). In the specimens in question, the metaconule was either weak and placed close to the protocone, or lacking altogether. There was, apparently, no development of metaconular cristae, nor extension of the postprotocrista (=postmetaconular crista=posterior cingulum in the region of the tooth in question) labially around the base of the metacone; the protoconal region of the tooth appears to have been anteroposteriorly constricted and transversely narrow relative to marsupials and eutherians.

Lower molars, if correctly referred, further contra- dict reference of this Smoky Hollow therian to the Marsupialia. Relative to a tribosphenid morphotype (as approximated by Aegialodon, or anterior molars, at least, of Kielantherium), the molar cusps are robust and the trigonid/talonid height differential reduced; these are trends seen in many Late Cretaceous marsupials (and other mammalian groups). However, de- finitive marsupial specializations, such as a lingually shifted hypoconulid and the development of a labial postcingulid (Clemens, 1979; Clemens and Lillegra- ven, 1986; Cifelli and Eaton, 1987) are lacking. Other characters of the Smoky Hollow lower molars regarded as primitive with respect to known marsupials include a very open trigonid, with the paraconid placed anteriorly and with a small, posteriorly placed metaconid; and the presence of a distal metacristid descending from the apex of the metaconid. This last feature is interpreted as indicating retention of primitive, single rank prevallum/postvallid shearing against the upper molar paracone and preparacrista (Fox, 1975).

Among described Tribosphenida not definitely referable to the Eutheria or Marsupialia, several are characterized by a reduced anterior stylar shelf. One of these is Falepetrus barwini, known by an upper molar from the Judithian "Mesaverde" Formation and

another of similar age from the Judith River Forma- tion (Clemens and Lillegraven, 1986). Falepetrus dif- fers from the Smoky Hollow therian in having more poorly developed stylar cusps in the C and D positions. Additionally, in Falepetrus the protocone and conules are well-developed. The protocone bears pre- and post- cingula, and crests extending labially from the conules indicate the presence of double rank shearing with the lower molars. The same is true of an unnamed therian from the upper Milk River Formation, described by Fox (1982). This taxon appears to have a better developed cusp in the C position than Falepetrus, and lacks protoconal cingula seen in that genus, but otherwise is similar and may be closely related to the Judithian form.

The only metatherian-eutherian grade mammal similar to the Smoky Hollow therian in having a reduced anterior stylar shelf and in retaining primitive single rank shearing is Picopsis, represented by upper molars and a lower molar trigonid from the Aquilan upper Milk River Formation (Fox, 1980). Like the Smoky Hollow therian, Picopsis has a well-marked cusp in the C position and has a cusp or cuspule on the posterior part of the stylar shelf. Available evidence is insufficient to evaluate the relationships of the Smoky Hollow therian, but its known morphology is weakly suggestive, at least, of Picopsis. Another possible relative of Picopsis is present in the Maastrichtian Lance For- mation, represented by AMNH 59451, an upper right molar described and illustrated by Clemens (1973a:fig. 26a, b).

A diminutive, new tribosphenic species from the Smoky Hollow Member is tentatively referred to An- chistodelphys, otherwise known from the lower Cam- panian Wahweap Formation of southern Utah (Cifelli, 1990b). The construction of the upper molars is rem- iniscent of marsupials, but cusps in the C and D positions are entirely lacking. Possession of a cusp in the D position, at least, is generally recognized as a marsupial characteristic, although many problems in the form of reversals within the Marsupialia and conver- gence by other, unrelated mammals, exist (see discussions by Clemens, 1979; Clemens and Lillegraven, 1986; Fox, 1987a, b; Cifelli, 1990a, b). Thus, based on existing criteria, ?Anchistodelphys delicatus is marsupial-like, but cannot be shown to share derived morphology of the upper molars in common with marsupials. The situation is complicated by consideration of the lower molars tentatively referred to this species. As with lower molars of the type species, A. archibaldi, these are clearly of marsupial design, specifically in the following features presumed to be derived within the Tribosphenida: paraconid lingually placed, in line with the metaconid and entoconid; trigonid to talonid height differential reduced; hypoconulid lingually placed and closely appressed to entoconid; and labial postcingulid extending from the hypoconulid around the base of the hypoconid (Clemens and Lillegraven, 1986; Cifelli and Eaton, 1987). It has been suggested that some of these features, at least, may be functionally related to an early




trend of marsupials toward anteroposterior expansion of the protocone and increase in size of the metacone relative to the paracone (Clemens and Lillegraven, 1986). Assuming the lower molars of both species of Anchistodelphys are correctly referred, this implies that the aforementioned specializations of the upper and lower molars may have occurred earlier in the evolution of marsupials than did diagnostic apomorphies of the stylar shelf. Although the possibility of cusp loss on the stylar shelf cannot be discounted, the simplest hypothesis for the relationships of Anchistodelphys is that it represents a marsupial sister taxon or primitive marsupial (depending on criteria employed in defining the group) in which a characteristic synapomorphy (consistent presence of stylar cusp D) had not yet evolved.

Two other members of the Smoky Hollow mammalian assemblage are probable marsupials but cannot be identified securely; one is represented by a highly inflated lower premolar suggestive of the Stagodonti- dae. The family is poorly represented in rock units overlying the Smoky Hollow Member of the Straight Cliffs Formation of southern Utah, although diverse mammalian faunas are known from the Wahweap and, especially, Kaiparowits formations (Eaton and Cifelli, 1988; Cifelli, 1990a, b, c). This is unusual in light of their abundance in more northerly faunas of Aquilan (Fox, 1971), Judithian (e.g., Russell, 1952; Sahni, 1972; Fox, 1981), and Lancian (Clemens, 1966) age. Stago- dontids have not been reported from the "Mesaverde" Formation (Lillegraven and McKenna, 1986) of Wy- oming or the Fruitland/Kirtland formations of the San Juan Basin, New Mexico (Clemens, 1973b; Flynn, 1986; Rigby and Wolberg, 1987), suggesting that the later distribution of the family was influenced by climate or geography. The earliest undoubted marsupial, Paria- dens kirklandi, from the Cenomanian Dakota For- mation, was referred to the Stagodontidae (Cifelli and Eaton, 1987). Stagodonts appear to be derived with respect to a marsupial morphotype in their emphasis on postvallum/prevallid shearing, characterized by a strongly developed postmetacrista on upper molars and paraconid/paracristid on lower molars, as well as in the enlargement and inflation of the premolars (Clem- ens, 1979; Fox, 1981; Fox and Naylor, 1986). Thus, the Marsupialia appear to have undergone some diversification by the Cenomanian, at least in North America. There exists little other direct evidence of this early radiation; however, primitive marsupials or marsupial-like taxa, such as Iqualadelphis (Fox, 1987a; Cifelli, 1990a), Anchistodelphys, and lugomortiferum (Cifelli, 1990b) were present in the Campanian and earlier, as the materials from the Turonian Smoky Hol- low Member attest. In South America, a diverse assemblage of marsupials is known from the latest Cre- taceous (Marshall and de Muizon, 1988) or early Tertiary (Van Valen, 1988); earlier deposits have yield- ed remains of other mammals but not, thus far, marsupials (e.g., Bonaparte, 1986). If a morphotype for all South American and Australian marsupials is approx-

imated by latest Cretaceous North American peradectids such as Alphadon (Clemens, 1966, 1979; Marshall, 1987; Reig et al., 1987), which appear to be derived relative to several Turonian and Campanian North American marsupials or marsupial-like taxa, then initial radiation of the group in North America, with Late Cretaceous dispersal to South America, rather than the reverse, may more simply explain their temporal and geographic distribution.

ACKNOWLEDGMENTS

I am grateful to Dr. Richard C. Fox, University of Alberta, for permission to study specimens in his care, to Drs. William A. Clemens, Jr. and Malcolm C. McKenna for comments on an earlier version of this paper, and to Dr. Jeff Eaton, for access to MNA specimens collected by him. I thank Scott Madsen, Ken Thiessen, Winford Sterling, Beth Larson, Dave Schmidt, and Mary C. Cifelli for assistance in field and laboratory activities. Support for this project was pro- vided by the Office of Research Administration and Department of Zoology, University of Oklahoma, and by grants from the National Geographic Society (2881- 84), National Science Foundation (BSR 8507598, 8796225, 8906992), and the Petroleum Research Fund of the American Chemical Society (20311 -G8). Stu- dent participation in the project was made possible by an REU supplement to the NSF award. The SEM pho- tos were prepared by Eric Sherburn at the Samuel Rob- erts Noble Electron Microscopy Laboratory, Univer- sity of Oklahoma.

LITERATURE CITED

Bonaparte, J. F. 1986. Sobre Mesungulatum houssayi y nuevos mamiferos Cretbcicos de Patagonia. IV Congreso Argentino Paleontologia y Bioestratigrafia:48-62.

Bowers, W. E. 1972. The Canaan Peak, Pine Hollow, and Wasatch formations in the Table Cliff region, Garfield County, Utah. Bulletin, United States Geological Survey 1331B:1-39.

Butler, P. M. 1978. A new interpretation of the mammalian teeth of tribosphenic pattern from the Albian of Texas. Breviora 446:1-27.

and Z. Kielan-Jaworowska. 1973. Is Deltatheridium a marsupial? Nature 245:105-106.

Cifelli, R. L. 1990a. Cretaceous mammals of southern Utah. I. Marsupials from the Kaiparowits Formation (Judi- thian). Journal of Vertebrate Paleontology, in press.

1990b. Cretaceous mammals of southern Utah. II. Marsupials and marsupial-like mammals from the Wah- weap Formation (early Campanian). Journal of Verte- brate Paleontology, in press.

1990c. Cretaceous mammals of southern Utah. IV. Eutherian mammals from the Wahweap (Aquilan) and Kaiparowits (Judithian) formations. Journal of Verte- brate Paleontology, in press.

and J. G. Eaton. 1987. Marsupial mammal from earliest Late Cretaceous of western US. Nature 325:520- 522.

and S. K. Madsen. 1986. An Upper Cretaceous symmetrodont (Mammalia) from southern Utah. Jour- nal of Vertebrate Paleontology 6:258-263.



344 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 10, NO. 3, 1990

Clemens, W. A. 1963. Late Jurassic mammalian fossils in the Sedgwick Museum, Cambridge. Palaeontology 6:373- 377.

1 1966. Fossil mammals of the type Lance Formation. Part II. Marsupialia. University of California, Publica- tions in Geological Sciences 62:1-122.

- 1973a. Fossil mammals of the type Lance Forma- tion. Part III. Eutheria and summary. University of Cal- ifornia, Publications in Geological Sciences 94:1-102.

1973b. The roles of fossil vertebrates in interpretation of Late Cretaceous stratigraphy of the San Juan Basin, New Mexico; pp. 154-167 in Four Corners Geo- logical Society Memoir Book, 1973.

1979. Marsupialia; pp. 192-221 in J. A. Lillegraven, Z. Kielan-Jaworowska, and W. A. Clemens (eds.), Me- sozoic Mammals: The First Two-thirds of Mammalian History. University of California Press, Berkeley.

and P.M. Lees. 1971. A review of English Early Cretaceous mammals; pp. 117-130 in D. M. Kermack and K. A. Kermack (eds.), Early Mammals. Zoological Journal, Linnean Society 50, supplement 1.

S and J. A. Lillegraven. 1986. New Late Cretaceous North American advanced therian mammals that fit neither the marsupial nor eutherian molds. Contributions to Geology, University of Wyoming, Special Paper 3: 55-85.

,, J. A. Lillegraven, E. H. Lindsay, and G. G. Simpson. 1979. Where, when, and what--a survey of known Me- sozoic mammal distribution; pp. 7-58 in J. A. Lille- graven, Z. Kielan-Jaworowska, and W. A. Clemens (eds.), Mesozoic Mammals: The First Two-thirds of Mam- malian History. University of California Press, Berkeley.

Crompton, A. W. 1971. The origin of the tribosphenic molar; pp. 65-87 in D. M. Kermack and K. A. Kermack (eds.), Early Mammals. Zoological Journal, Linnean So- ciety 50, supplement 1.

Dashzeveg, D., and Z. Kielan-Jaworowska. 1984. The lower jaw of an aegialodontid mammal from the Early Cre- taceous of Mongolia. Zoological Journal, Linnean So- ciety 82:217-227.

Eaton, J. G. 1987. Stratigraphy, depositional environ- ments, and age of Cretaceous mammal-bearing rocks in Utah, and systematics of the Multituberculata (Mam- malia). Ph.D. dissertation, University of Colorado, Boulder, 308 pp.

- and R. L. Cifelli. 1988. Preliminary report on Late Cretaceous mammals of the Kaiparowits Plateau, southern Utah. University of Wyoming, Contributions to Ge- ology 26:45-55.

Emry, R. J., J. D. Archibald, and C. C. Smith. 1981. A mammalian molar from the Late Cretaceous of northern Mississippi. Journal of Paleontology 55:953-956.

Flynn, L. J. 1986. Late Cretaceous mammal horizons from the San Juan Basin, New Mexico. American Museum Novitates 2845:1-30.

Fox, R. C. 1969. Studies of Late Cretaceous vertebrates. III. A triconodont mammal from Alberta. Canadian Journal of Zoology 47:1253-1256.

1971. Marsupial mammals from the early Cam- panian Milk River Formation, Alberta, Canada, pp. 145- 164 in D. M. Kermack and K. A. Kermack (eds.), Early Mammals. Zoological Journal, Linnean Society 50, supplement 1. - 1972. A primitive therian mammal from the Upper Cretaceous of Alberta. Canadian Journal of Earth Sci- ences 9:1479-1494.

1974. Deltatheroides-like mammals from the Upper Cretaceous of North America. Nature 249:392.

1975. Molar structure and function in the Early Cretaceous mammal Pappotherium: evolutionary implications for Mesozoic Theria. Canadian Journal of Earth Sciences 12:412-442.

1976. Additions to the mammalian local fauna from the Upper Milk River Formation (Upper Cretaceous), Alberta. Canadian Journal of Earth Sciences 13:1105- 1118.

1979. Mammals from the Upper Cretaceous Old- man Formation, Alberta. I. Alphadon Simpson (Mar- supialia). Canadian Journal of Earth Sciences 16:91- 102.

1980. Picopsis pattersoni, n. gen. and sp., an unusual therian mammal from the Upper Cretaceous of Alberta, and the classification of primitive tribosphenic mammals. Canadian Journal of Earth Sciences 17:1489-1498.

1981. Mammals from the Upper Cretaceous Old- man Formation, Alberta. V. Eodelphis Matthew, and the evolution of the Stagodontidae. Canadian Journal of Earth Sciences 18:350-365.

1982. Evidence of a new lineage of tribosphenic therians (Mammalia) from the Upper Cretaceous of Al- berta, Canada. Geobios, M6moire Special 6:169-175.

1984a. A primitive, "obtuse-angled" symmetrodont (Mammalia) from the Upper Cretaceous of Alberta, Canada. Canadian Journal of Earth Sciences 21:1204- 1207.

1984b. Paranyctoides maleficus (new species), an early eutherian mammal from the Cretaceous of Alberta. Special Publication, Carnegie Museum of Natural His- tory 9:9-20.

1985. Upper molar structure in the Late Cretaceous symmetrodont Symmetrodontoides Fox, and a classification of the Symmetrodonta (Mammalia). Journal of Paleontology 59:21-26.

- 1987a. An ancestral marsupial and its implications for early marsupial evolution; pp. 10 1-105 in P. J. Currie and E. H. Koster (eds.), Fourth Symposium on Mesozoic Terrestrial Ecosystems. Occasional Paper 3, Tyrrell Mu- seum of Palaeontology, Drumheller.

S1987b. Palaeontology and the early evolution of marsupials; pp. 161-169 in M. Archer (ed.), Possums and Opossums: Studies in Evolution. Surrey Beatty & Sons and the Royal Zoological Society of New South Wales, Sydney.

and B. G. Naylor. 1986. A new species of Didel- phodon Marsh (Marsupialia) from the Upper Cretaceous of Alberta, Canada: paleobiology and phylogeny. Neues Jahrbuch Geologie Palaiontologie Abhandlung 172:357- 380.

Gregory, H. E., and R. C. Moore. 1931. The Kaiparowits region. A geographic and geologic reconnaissance of part of Arizona and Utah. United States Geological Survey, Professional Paper 164:1-161.

Hiiemae, K. M., and R. F. Kay. 1973. Evolutionary trends in the dynamics of primate mastication; pp. 28-64 in M. R. Zingeser (ed.), Symposium Fourth International Congress of Primatology. 3. Craniofacial Biology of Pri- mates. S. Karger, Basel.

Jenkins, F. A., and C. R. Schaff. 1988. The Early Cretaceous mammal Gobiconodon (Mammalia, Triconodonta) from the Cloverly Formation in Montana. Journal of Verte- brate Paleontology 8:1-24.

Kermack, K. A., P. M. Lees, and F. Mussett. 1965. Aegi-




alodon dawsoni, a new trituberculosectorial tooth from the lower Wealden. Proceedings, Royal Society of Lon- don, B 162:535-554.

Kielan-Jaworowska, Z. 1975. Evolution of the therian mammals in the Late Cretaceous of Asia. Part I. Del- tatheridiidae. Palaeontologica Polonica 33:103-132.

, T. M. Bown, and J. A. Lillegraven. 1979. Eutheria; pp. 221-258 in J. A. Lillegraven, Z. Kielan-Jaworowska, and W. A. Clemens (eds.), Mesozoic Mammals: The First Two-thirds of Mammalian History. University of California Press, Berkeley.

Krause, D. W., and D. Baird. 1979. Late Cretaceous mammals east of the North American western interior sea- way. Journal of Paleontology 53:562-565.

Lillegraven, J. A. 1969. Latest Cretaceous mammals of upper part of Edmonton Formation of Alberta, Canada, and review of marsupial-placental dichotomy in mammalian evolution. Paleontological Contributions, Uni- versity of Kansas 50 (Vertebrata 12):1-122.

- and S. L. Bieber. 1986. Repeatability of measurements of small mammalian fossils with an industrial measuring microscope. Journal of Vertebrate Paleon- tology 6:96-100.

and M. C. McKenna. 1986. Fossil mammals from the "Mesaverde" Formation (Late Cretaceous, Judithi- an) of the Bighorn and Wind River basins, Wyoming, with definitions of Late Cretaceous North American land- mammal "ages." American Museum Novitates 2840:1- 68.

,, S. D. Thompson, B. K. McNab, and J. L. Patton. 1987. The origin of eutherian mammals. Biological Journal, Linnean Society 32:281-336.

Marshall, L. G. 1987. Systematics of Itaboraian (middle Paleocene) age "opossum-like" marsupials from the limestone quarry at Sio Jose de Itaborai, Brazil; pp. 91- 160 in M. Archer (ed.), Possums and Opossums: Studies in Evolution. Surrey Beatty & Sons and the Royal Zoo- logical Society of New South Wales, Sydney.

and C. de Muizon. 1988. The dawn of the Age of Mammals in South America. National Geographic Re- search 4:23-55.

Patterson, B. 1955. A symmetrodont from the Early Cre- taceous of north Texas. Fieldiana, Zoology 37:689-693.

- 1956. Early Cretaceous mammals and the evolution of mammalian molar teeth. Fieldiana, Geology 13:1- 105.

Peterson, F. 1969a. Cretaceous sedimentation and tecto- nism in the southeastern Kaiparowits region, Utah. Open- file Report, United States Geological Survey, 259 pp.

- I 1969b. Four new members of the Upper Cretaceous Straight Cliffs Formation in southeastern Kaiparowits region, Kane County, Utah. Bulletin, United States Geo- logical Survey 1274J:1-28.

Reig, O., J. A. Kirsch, and L. G. Marshall. 1987. Systematic relationships of the living and neocenozoic American "opossum-like" marsupials (Suborder Didelphimor- pha), with comments on the classification of these and of the Cretaceous and Paleogene New World and Eu- ropean metatherians; pp. 1-89 in M. Archer (ed.), Pos- sums and Opossums: Studies in Evolution. Surrey Beatty & Sons and the Royal Zoological Society of New South Wales, Sydney.

Rigby, J. K., and D. L. Wolberg. 1987. The therian mammal fauna (Campanian) of Quarry 1, Fossil Forest Study Area, San Juan Basin, New Mexico. Special Paper, Geo- logical Society of America 209:51-79.

Russell, L. S. 1952. Cretaceous mammals of Alberta. Bul- letin, National Museum of Canada 126:110-119.

1975. Mammalian faunal succession in the Creta- ceous system of western North America; pp. 137-161 in W. G. E. Caldwell (ed.), The Cretaceous System in the Western Interior of North America. Special Paper, Geological Association of Canada 13.

Sahni, A. 1972. The vertebrate fauna of the Judith River Formation, Montana. Bulletin, American Museum of Natural History 147:321-412.

Simpson, G. G. 1928. A Catalogue of the Mesozoic Mam- malia in the Geological Department of the British Mu- seum. British Museum (Natural History), London, 215 pp.

1936. Studies of the earliest mammalian dentitions. Dental Cosmos (1936):1-24.

Slaughter, B. H. 1971. Mid-Cretaceous (Albian) therians of the Butler Farm local fauna, Texas; pp. 131-143 in D. M. Kermack and K. A. Kermack (eds.), Early Mam- mals. Zoological Journal, Linnean Society 50, supplement 1.

Van Valen, L. 1988. Paleocene dinosaurs or Cretaceous ungulates in South America? Evolutionary Monographs 10:1-79.

Received 24 May 1989; accepted 27 October 1989.



Documents

Cretaceous Mammals of Southern Utah. III. Therian Mammals from the Turonian (Early Late Cretaceous)