JOURNAL ARTICLE

Early Cretaceous mammal from North America and the evolution of marsupial dental characters

R L Cifelli
Proceedings of the National Academy of Sciences of the United States of America 1993 October 15, 90 (20): 9413-6
8415715
A mammal from the Early Cretaceous of the western United States, represented by a lower jaw exceptional in its completeness, presents unambiguous evidence of postcanine dental formula in an Early Cretaceous marsupial-like mammal, and prompts a reconsideration of the early evolution of marsupial dental characters. A marsupial postcanine dental formula (three premolars and four molars) and several marsupial-like features of the lower molars are present in the new taxon, but a hallmark specialization of marsupials (twinning of the hypoconulid and entoconid on lower molars) is lacking. This, coupled with recent evidence from the Late Cretaceous of the western United States, suggests that the distinctive marsupial dental formula evolved prior to the most characteristic specialization of lower molars and that apomorphies presumed to be diagnostic of the upper molars (such as auxiliary stylar cusps) were relatively more recent developments in marsupial history. Dental evidence supports the monophyly of higher (tribosphenic) mammals and suggests that the predominantly Old World Deltatheroida, recently proposed as a sister taxon to marsupials, represents a primitive and unrelated group of higher mammals; by this interpretation, early marsupials and their presumed close relatives are restricted to North America. This, together with the hypothesized relationships of South American/Australian marsupials (in the context of the North American Cretaceous radiation) and evidence from the fossil record of South America, in turn supports a North American origin for the group.

Full Text Links

Find Full Text Links for this Article

Discussion

You are not logged in. Sign Up or Log In to join the discussion.

Trending Papers

Remove bar
Read by QxMD icon Read
8415715
×

Save your favorite articles in one place with a free QxMD account.

×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"