early eutherian evolution

Ken Kinman kinman2 at YAHOO.COM
Sat Feb 19 13:25:17 CST 2005

Dear All,
     More complete material of a very cool, recently-described mammal fossil (Gomphos) is described in the latest issue of Science.  And the cladistic analysis pretty convincingly shows that Family Zalambdalestidae is far removed from Glires (or any other extant eutherian grouping for that matter).  Thank goodness we've finally got that settled (hopefully).  The BBC report has a nice picture of what Gomphos might have looked like (not surprisingly, it looks sort of like a cross between a pika and a ground squirrel):


R. J. Asher, M. Jin, J. R. Wible, M. C. McKenna, G. W. Rougier, D. Dashzeveg, and M. J. Novacek, 2005.  Stem Lagomorpha and the Antiquity of Glires.  Science, 307:1091-1094 (18 February 2005).
"We describe several fossils referable to *Gomphos elkema* from deposits close to the Paleocene-Eocene boundary at Tsagan Khushu, Mongolia.  *Gomphos* shares a suite of cranioskeletal characters with extant rabbits, hares, and pikas but retains a primitive dentition and jaw compared to its modern relatives.  Phylogenetic analysis supports the position of *Gomphos* as a stem lagomorph and excludes Cretaceous taxa from the crown radiation of placental mammals.  Our results support the hypothesis that rodents and lagomorphs radiated during the Cenozoic and diverged from other placental mammals close to the Cretaceous-Tertiary boundary."

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