Multituberculates From The Woodbine

Bona fide Early Cretaceous mammals are known from four regions and stratigraphic units in North America: the Trinity Group, Texas and Oklahoma (figure 2.14); the Cloverly Formation, Wyoming and Montana; the Kelvin Formation, Utah (figure 2.10); and the Arundel Clay, Maryland (figure 2.15). A fifth, the Cedar Mountain Formation, Utah (figure 2.10), straddles Albian-Cenomanian time (Early-Late Cretaceous) and is arbitrarily discussed under this heading as well.

The Trinity Group in north-central Texas includes (in ascending order) the Twin Mountains, Glen Rose, and Paluxy formations. Invertebrates from the Glen Rose and

figure 2.14. Cretaceous mammal localities of Texas and Oklahoma. Black diamonds, Early Cretaceous (localities 1-7); gray diamonds (localities 8-14), Late Cretaceous. Localities or local faunas: 1, Paluxy Church (Twin Mountains Formation; late Aptian); 2, Pecan Valley Estates (Paluxy Formation; early Albian); 3, Butler Farm; 4, Greenwood Canyon; 5, Willawalla; 6, Umsted Farm; 7, McLeod Honor Farm (all Antlers Formation; Aptian-Albian); 8, Carter Field; 9, Bear Creek (Woodbine Formation; Cenomanian); 10, Commerce (Kemp Clay;Maastrichtian); 11, Terlingua; 12, Running Lizard; 13, Talley Mountain (upper shale member,Aguja Formation; late Cam-panian: Judithian).

figure 2.14. Cretaceous mammal localities of Texas and Oklahoma. Black diamonds, Early Cretaceous (localities 1-7); gray diamonds (localities 8-14), Late Cretaceous. Localities or local faunas: 1, Paluxy Church (Twin Mountains Formation; late Aptian); 2, Pecan Valley Estates (Paluxy Formation; early Albian); 3, Butler Farm; 4, Greenwood Canyon; 5, Willawalla; 6, Umsted Farm; 7, McLeod Honor Farm (all Antlers Formation; Aptian-Albian); 8, Carter Field; 9, Bear Creek (Woodbine Formation; Cenomanian); 10, Commerce (Kemp Clay;Maastrichtian); 11, Terlingua; 12, Running Lizard; 13, Talley Mountain (upper shale member,Aguja Formation; late Cam-panian: Judithian).

other marine units constrain the age of the Twin Mountains Formation as Aptian and that of the Paluxy Formation as early to middle Albian (Jacobs et al., 1991; Jacobs and Winkler, 1998). The Twin Mountains and Paluxy formations are terrigenous and are comprised of sandstones, claystones, and siltstones of fluviodeltaic origin, deposited on a coastal plain. Northward and eastward, in far northern Texas and southern Oklahoma, the Glen Rose pinches out. Here the terrigenous rocks of the Trinity Group are referred to the Antlers Formation and, lacking the marine invertertebrates needed for more precise correlation, are simply regarded as being of Aptian-Albian age. An excellent summary of the geology and faunas from localities in Texas is given by Winkler et al. (1990).

Thus far, only three mammals—an unidentified multi-tuberculate, an unidentified therian, and the triconodon-

tid Astroconodon denisoni—are known from beds unequivocally belonging to the Aptian Twin Mountains Formation. All of these are from a single site, Paluxy Church, Hood County, Texas (figure 2.14, table 2.14). The only mammal definitely known from a locality in the Paluxy Formation is Comanchea hilli, a somewhat aberrant tri-bosphenic mammal represented by an upper molar (Jacobs et al., 1989) from Pecan Valley Estates in Erath County, Texas (see chapter 11).

All the remaining mammals from the Trinity Group come from the Antlers Formation. The initial discovery was made in 1949, when personnel from the Field Museum recovered two jaws of the triconodontid Astro-conodon denisoni from the surface at Greenwood Canyon (see Patterson, 1951) (figure 2.14). Follow-up investigations by Bryan Patterson and colleagues led to the recov figure 2.15. Cretaceous mammal localities of the eastern United States. Black diamond, Early Cretaceous (locality 1); gray diamonds, Late Cretaceous (localities 2-7). Localities or local faunas: 1, Muirkirk (Arundel Clay facies, Potomac Group, ?middle Aptian, Maryland); 2, Vinton Bluff (Tombigee Sand, Eutaw Formation, late Santonian, Mississippi); 3, Elizabethtown Dump (Black Creek Group; ?Campanian, North Carolina); 4, Ellisdale (Marshalltown Formation, late Campanian, New Jersey); 5, Hop Brook; 6, Ramanssein Brook (both Mount Laurel Formation, Maastrichtian, New Jersey); 7, Monmouth Brook (?Campanian, New Jersey).

Arundel Formation Potomac Group Map

figure 2.15. Cretaceous mammal localities of the eastern United States. Black diamond, Early Cretaceous (locality 1); gray diamonds, Late Cretaceous (localities 2-7). Localities or local faunas: 1, Muirkirk (Arundel Clay facies, Potomac Group, ?middle Aptian, Maryland); 2, Vinton Bluff (Tombigee Sand, Eutaw Formation, late Santonian, Mississippi); 3, Elizabethtown Dump (Black Creek Group; ?Campanian, North Carolina); 4, Ellisdale (Marshalltown Formation, late Campanian, New Jersey); 5, Hop Brook; 6, Ramanssein Brook (both Mount Laurel Formation, Maastrichtian, New Jersey); 7, Monmouth Brook (?Campanian, New Jersey).

ery of fossils belonging to additional taxa, including at least one multituberculate (herein tentatively assigned to the primitive cimolodontan ?Paracimexomys crossi), the "symmetrodontan" Spalacotheroides bridwelli, and tri-bosphenic mammals, two of which (Holoclemensia texana and Kermackia texana) were later given formal names (see Butler, 1978a).8 The so-called "Trinity therians" occupy a prominent position among early mammals because their study led to the current interpretation of molar evolution during the Mesozoic (Patterson, 1956; see also Butler, 1939). Patterson employed underwater screenwashing and associated techniques to recover the mammalian fossils, as have all subsequent paleontologists working in the Trinity Group. As a result, virtually all the specimens are isolated

8 We omit Adinodon pattersoni, based on an edentulous dentary (Hershkovitz, 1995), which we consider indeterminate (see Cifelli and Muizon, 1997).

teeth or parts thereof. Notwithstanding an earlier statement (Patterson, 1956) to the contrary, there is no definitive evidence for "plagiaulacidan" multituberculates in the Trinity Group of Texas or, for that matter, from other Aptian-Albian faunas of North America. All specimens recovered thus far appear to represent primitive cimo-lodontans referable to the Paracimexomys group (Krause et al., 1990; Cifelli, 1997a). A nearby site to the north, Willawalla, was worked by personnel from the Field Museum (figure 2.14). Patterson (1956) mentioned unspecified mammals, but to our knowledge, the only published occurrence from this site (also known as King's Creek) is Astroconodon, reported by Winkler et al. (1990).

During the 1960s, Bob Slaughter, of Southern Methodist University, made a significant collection of mammalian fossils from several sites at Butler Farm, Wise County, Texas (figure 2.14). At least seven taxa are represented, four of which are tribosphenic therians. Slaughter (e.g., 1971) believed that both Marsupialia (Holoclemensia) and table 2.14. Early Cretaceous Mammals of North America (see figures 2.10, 2.14,2.15; locality numbers do not correspond between table and maps). Localities: 1, Paluxy Church (Twin Mountains Formation, Aptian); 2, Pecan Valley Estates (Paluxy Formation, Albian); 3, Greenwood Canyon; 4, Butler Farm; 5, Willawalla; 6, Umsted Farm; 7, McLeod Honor Farm (all Antlers Formation, Aptian-Albian); 8, Bridger (two sites, undifferentiated here); 9, Cashen Ranch; 10, Cottonwood Creek; 11, Crooked Creek; 12, Ninemile Hill (all Cloverly Formation, Aptian-Albian); 13, Coalville (Kelvin Formation, Aptian-Albian); 14, Muirkirk (Arundel Clay, Aptian)

Mammalia incertae sedis (11, 12, 13) Eutriconodonta

Gobiconodontidae

Gobiconodon ostromi (8, 9) Triconodontidae

Gen. et sp. indet. (10, 11) Arundelconodon hottoni (14) Astroconodon denisoni (1, 3, 4, 7) Astroconodon cf. denisoni (5, 6) cf. Astroconodon sp. (8, 9) Corviconodon montanensis (9) Multituberculata

Family incertae sedis

Gen. et sp. indet. (1, 7, 9) ?Paracimexomys crossi (7) cf. Paracimexomys sp. (3, 4, 11) Stem Trechnotheria ("symmetrodontans") Spalacotheriidae

Gen. et sp. indet. (10) Spalacotheroides bridwelli (3) cf. Spalacotheroides sp. (7, 10, 11)

Stem Boreosphenida ("tribotherians") Family incertae sedis Comanchea hilli (2) Slaughteria eruptens (4) Gen. et sp. indet. (1, 7,9, 10, 11) Kermackiidae

Kermackia texana (3) Trinititherium slaughteri (4) Pappotheriidae

Gen. et sp. indet. (7) Holoclemensia texana (3, 4) Pappotherium pattersoni (4) ?Deltatheroida

Family incertae sedis

Atokatheridium boreni cf. Atokatheridium boreni Eutheria

Family incertae sedis

Montanalestes keeblerorum (10)

Eutheria (Pappotherium) were present in the fauna, but evidence for this is tenuous (Butler, 1978a; Jacobs et al., 1989; Cifelli, 1999b), and they are treated later (chapter 11) as "tribotherians." Both Greenwood Canyon and Butler Farm are reportedly no longer accessible (Winkler et al., 1989), but ongoing investigations at other localities of the Trinity Group of Texas are being carried out by Louis L. Jacobs, Dale A. Winkler, and associates, also at Southern Methodist University (e.g., Jacobs et al., 1989; Jacobs and Winkler, 1998; Winkler et al., 1990).

The Antlers Formation also crops out in a narrow band along southern Oklahoma. Field parties led by Richard L. Cifelli have recovered mammals from two sites, Umsted Farm and the McLeod Honor Farm, both in Atoka County (figure 2.14). Mammals described thus far include the multituberculate ?Paracimexomys crossi; an unidentified (probably new) tribosphenic mammal (Cifelli, 1997a); and a possible deltatheroidan, Atokatheridium boreni (see Kielan-Jaworowska and Cifelli, 2001, and chapter 12). Several other mammals and a host of other microverte-brates are known from the sites (Cifelli, Gardner, et al., 1997), and work is continuing.

The Cloverly Formation, exposed along the margins of the Bighorn Basin and other areas of Montana and

Wyoming, is well known for its dinosaur fauna (Ostrom, 1970). Age constraints on the unit are imprecise; it is older than the overlying Thermopolis Shale, which is estimated on the basis of marine invertebrates to be early late Al-bian (Jacobs et al., 1991; Jacobs and Winkler, 1998). The Cloverly is generally assigned an Aptian-Albian age based on the similarity of its vertebrate assemblage with that of the Trinity Group (see, e.g., Brinkman et al., 1998). The Cloverly consists of fluvially deposited claystones, silt-stones, and occasional sandstones, with color banding suggestive of paleosol development. Three units of the Cloverly Formation, V-VII, are recognized in Ostrom's (1970) stratigraphic sequence, and each of these has yielded mammals. Though fewer taxa are known than from the Trinity Group, the Cloverly Formation is significant because it has yielded some rather complete specimens through surface prospecting and quarrying procedures, as well as isolated teeth obtained through bulk rock processing.

Field parties led by Farish A. Jenkins, of Harvard University, made the initial discovery of mammals in the Cloverly Formation in the 1970s, and work by Cifelli and associates is in progress. Lewis Pocket, southeast of Bridger (figure 2.10), yielded a remarkable series of a triconodon-

tid similar to Astroconodon, represented by nearly complete skulls and postcranial elements (Jenkins and Crompton, 1979; Crompton and Sun, 1985). The site is near the famous Yale Deinonychus Quarry (Ostrom, 1970); fossils occur in limonitic nodules in unit V. About 2 km to the east, a second site in the Bridger area yielded jaws and postcrania of the large eutriconodontan Gobi-conodon ostromi (see Jenkins and Schaff, 1988). The site is in the base of unit VII.

Fossil mammals have also been recovered from the vicinity of Cashen Ranch (figure 2.10), southern Montana, in the base of unit VII of the Cloverly Formation. In addition to Gobiconodon (see Jenkins and Schaff, 1988), the triconodontid Corviconodon (see Cifelli et al., 1998) and several undescribed taxa are present (RLC, unpubl. data).

A third area for mammals in the Cloverly Formation is in the Cottonwood Creek drainage, east of Edgar, Montana (figure 2.10). The productive zone, again in the base of unit VII, has thus far yielded jaws of several undescribed taxa, as well as the tribosphenic mammal Montanalestes keeblerorum (see Cifelli, 1999b). Montanalestes appears to be a eutherian, which are known elsewhere in the Early Cretaceous only from Asia (Averianov and Skutschas, 2000a; Ji et al., 2002). Eutheria are otherwise unknown from North America until the early Campanian (Fox, 1984b; Cifelli, 1990e), which may not be surprising considering the sparseness of the fossil record from the early Late Cretaceous. A second mammal from Cottonwood Creek is a spalacotheriid symmetrodontan similar to Spala-cotheroides from the Antlers Formation of Texas. The fossil from Cottonwood Creek is a remarkably complete den-tary, including the canine and all postcanine teeth (Cifelli et al., 2000).

A small microvertebrate assemblage, obtained through screenwashing, is known from unit V of the Cloverly Formation at Crooked Creek, northern Wyoming (figure 2.10). Two mammals are known from this site; one is a triconodontid otherwise unknown from the Cloverly Formation, so it documents a considerable diversity of these primitive mammals from the unit—at least four eutriconodontans are known from the Cloverly (Cifelli et al., 1998). A single mammalian tooth, a lower premolar, has been recovered from beds presumed to represent the Cloverly Formation at Ninemile Hill, Como Bluff, Wyoming (Trujillo, 1999).

A single mammal specimen, an unidentified petrosal, has been recovered from a site near Coalville, Utah (figure 2.10). The specimen is from the Kelvin Formation, reported to be of Aptian-Albian age (Prothero, 1983). The site has also yielded dinosaur eggshell material (Jensen, 1970).

The Arundel Clay, exposed in Maryland (figure 2.15) and adjacent parts of the U.S. Eastern Seaboard, is another

Lower Cretaceous unit known primarily for its dinosaurs. Most such fossils were collected in the nineteenth century, while the clay was being mined for the sedimentary iron ore contained within it (Kranz, 1996), and consist of isolated, largely indeterminate elements (see, e.g., Gilmore, 1921). The Arundel Clay is considered to be a facies within the Potomac Group and appears to represent swamp deposits in a system of fluvial oxbows (Kranz, 1998). The Potomac Group is well known for its fossil flora; paly-nomorphs suggest an Aptian, probably middle Aptian, age for the Arundel Clay (Doyle, 1992). The only mammal known from the Arundel Clay is the triconodontid Arun-delconodon hottoni, based on a dentary found by Thomas R. Lipka at a site near Muirkirk, Maryland (a second, edentulous dentary from the same site is tentatively referred to the same species, see Rose et al., 2001). This species clearly belongs to an endemic North American clade of the group, but is more primitive than other taxa known from the Early Cretaceous of this continent (Cifelli, Lipka, et al., 1999).

The Cedar Mountain Formation, Utah (figure 2.10), is of interest because it appears to include rocks spanning the Barremian through the uppermost Albian. Several superposed dinosaur faunas are known (Kirkland et al., 1997) but, thus far, mammals are only known from the uppermost part of the Cedar Mountain Formation. Field studies by Jeffrey G. Eaton and Michael Nelson in 1983 led to recovery of the first mammals known from the unit (Nelson and Crooks, 1987;Eaton and Nelson, 1991).Later investigations by Cifelli and colleagues, still continuing, have resulted in a large, well-sampled collection, including some 80 taxa of vertebrates (Cifelli, Kirkland, et al., 1997). The fossil assemblage is from a restricted stratigraphic level in the Mussentuchit Member of the Cedar Mountain Formation and is termed the Mussentuchit local fauna (Cifelli, Nydam, Weil, et al., 1999). Mammals, known from eight sites, were collected mainly through bulk matrix processing, though some well-preserved specimens were found through quarrying. Most of the sites are in fluvial overbank deposits. A radiometric date of 98.39 ± 0.07 Ma places the Mussentuchit local fauna at the Albian-Cenomanian (Early-Late Cretaceous) boundary (Cifelli, Kirkland, et al., 1997).

The fauna of some 28 mammal taxa (table 2.15) includes at least three triconodontids (two genera, Astrocon-odon and Corviconodon, are shared with the Aptian-Albian faunas of North America) and four "symmetrodontans" (one genus, Spalacotheridium, is shared with younger North American faunas), indicating a surprising diversity of these archaic groups. Both the triconodontids and the "symmetrodontans" belong to endemic North American clades and are distantly related to those known from else-

table 2.15. Albian-Cenomanian Mammals of the Mussentuchit Local Fauna, Utah (see figure 2.10)

Eutriconodonta Triconodontidae

Astroconodon delicatus Corviconodon utahensis Jugulator amplissimus Multituberculata

?"Plagiaulacida," family incertae sedis Ameribaatar zofiae Janumys erebos cf. Janumys erebos Gen. et sp. indet. Cimolodonta, family incertae sedis Bryceomys intermedius Bryceomys cf. intermedius Cedaromys bestia Cedaromys cf. bestia Cedaromys parvus Cedaromys cf. parvus ?Paracimexomys perplexus ?Paracimexomys cf. perplexus ?Paracimexomys robisoni ?Paracimexomys cf. robisoni Neoplagiaulacidae ?Mesodma sp. Stem Trechnotheria ("symmetrodontans") Spalacotheriidae

Spalacolestes cretulablatta Spalacolestes inconcinnus Spalacotheridium noblei Family incertae sedis Gen. et sp. indet. Stem Boreosphenida ("tribotherians") Picopsidae

Gen. et sp. indet. Family incertae sedis Gen. nov., sp. A Gen. nov., sp. B Marsupialia

?Stagodontidae

Pariadens mckennai Family incertae sedis Adelodelphys muizoni Kokopellia juddi Sinbadelphys schmidti where in the world (Cifelli and Madsen, 1998, 1999). As many as 15 taxa of multituberculates, collectively represented by more than 1,000 specimens, are known from the Mussentuchit local fauna (Eaton and Cifelli, 2001). Several may represent surviving "plagiaulacidans." Most of the multituberculates of the Mussentuchit local fauna belong to the Paracimexomys group of basal cimolodontans (see chapter 8); Bryceomys, otherwise known from the Turanian of Utah, makes its first appearance in this fauna. Also notable is the first appearance of Neoplagiaulacidae, in the form of ?Mesodma, a genus otherwise known from Aquilan and younger assemblages in the Late Cretaceous of North America. The Mussentuchit local fauna includes six boreo-sphenidan mammals, four of which are marsupials: Ade-lodelphys, Kokopellia, Pariadens, and Sinbadelphys (Cifelli, 1993a; Cifelli and Muizon, 1997; Cifelli, 2004). Pariadens, a possible stagodontid, is also known from the Cenoman-ian of Utah (Cifelli and Eaton, 1987; Eaton, 1993b). Despite the fact that they dominate the therian component of the Mussentuchit local fauna, marsupials of the Cedar Mountain Formation are rare and low in diversity (both taxonomic and morphologic) compared to Campanian-Maastrichtian faunas of North America. Currently, these four taxa are the oldest known marsupials. Their primi-tiveness, low diversity, and modest morphologic differentiation suggest that they may lie near the base of North America's Cretaceous marsupial radiation (Cifelli, 2004). There is as yet no definitive evidence for Eutheria in the Mussentuchit local fauna, despite their earlier (Aptian-Albian) presence in North America. Curiously, while the mammals seem to represent North American clades with no obvious close ties to groups known from elsewhere, other taxa in the Mussentuchit local fauna, particularly dinosaurs, suggest a proximal origin from Asia (Cifelli, Kirkland, et al., 1997).

Two footprints attributed to a mammal, Duquettichnus kooli, have been described from the Early Cretaceous of the Peace River Canyon, British Columbia. They are reported to show syndactyly of pedal digits II and III, so they have been referred to the Marsupialia (Sarjeant and Thul-born, 1986). Additional tracks from the Gates Formation, Alberta (Albian), are believed to represent several types of mammals (Sarjeant, 2000).

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