Meeting Abstract

P1.44  Thursday, Jan. 3  Development of the ethmoid in Caluromys philander compared with other didelphid marsupials MACRINI, Thomas E.*; S�NCHEZ-VILLAGRA, Marcelo; American Museum of Natural History, New York, NY, USA; Palaeontologisches Institut und Museum, Z�rich, Switzerland tmacrini@amnh.org

The development of the ethmoid of Caluromys philander (Didelphidae; Marsupialia) is described based on serial sections of a growth series of six individuals. The ethmoid of Caluromys is compared with those of the didelphids Monodelphis domestica and Didelphis marsupialis based on descriptions in the literature. Caluromys has two frontoturbinals and four ethmoturbinals that are present in the youngest animals examined, pouch young. Later in postnatal ontogeny, an additional element, an “interturbinal” develops between Ethmoturbinals II and III. A similar pattern of development is present in Monodelphis and Didelphis, with the exception being that Didelphis has an additional frontoturbinal. This additional frontoturbinal eventually becomes fused to Ethmoturbinal I in the adult Didelphis. The presence of an interturbinal between Ethmoturbinals II and III is likely conserved across didelphids as each of these taxa represent different and relatively distant clades within Didelphidae. This interturbinal corresponds with the bony element that is named Endoturbinal III (by some authors) in the adult didelphid skull. Endoturbinals are the bony turbinals located below the frontoturbinals and nasoturbinal; in didelphids these include the ethmoturbinals and interturbinal. Presence of two bony frontoturbinals (or ectoturbinals) and five endoturbinals in adult marsupials appears to be the ancestral condition for the clade. However, homologies of the individual bony elements in many adult marsupials are untested via comparative ontogeny. It is not clear if the developmental pattern for turbinals seen in didelphids is conserved across Marsupialia.