Download cretaceous mammals of southern utah. ii. marsupials and marsupial

Journal of Vertebrate Paleontology 10(3):320-331, September 1990
© 1990 by the Society of Vertebrate Paleontology
CRETACEOUS MAMMALS OF SOUTHERN UTAH. II. MARSUPIALS AND
MARSUPIAL-LIKE MAMMALS FROM THE WAHWEAP FORMATION
(EARLY CAMPANIAN)
RICHARD L. CIFELLI
Oklahoma Musem of Natural History and Department of Zoology,
University of Oklahoma, Norman, Oklahoma 73019
ABSTRACT—The Wahweap Formation of southern Utah is probably early Campanian in age. Its
mammalian fauna is generally similar to that of the Aquilan upper Milk River Formation, Alberta,
but differs substantially from that and all other known Late Cretaceous mammalian local faunas.
Wahweap taxa referable to the Marsupialia include a new, somewhat derived species of Protalphadon
and an unidentified taxon. Two new genera and species of advanced therian mammals are described.
The status of these taxa is uncertain, because in some respects (such as the "twinning" of lower molar
hypoconulid with entoconid) they share advanced morphology with undoubted Cretaceous marsupials,
while in others (such as the variable or complete absence of stylar cusp D on upper molars) they may
be more primitive than known marsupials and, in fact, would be excluded from the group using most
currently-accepted criteria. Although these two Wahweap species could represent members of advanced
lineages in which characteristic marsupial specializations were lost, a simpler explanation is that they
are primitive in these regards, and represent either primitive marsupials or marsupial sister-taxa,
depending on how the group is defined.