Lung morphology in rodents (Mammalia, Rodentia) and its implications for systematics

A new nomenclature of the lung lobes and of the bronchial tree is presented , with which the lungs in 40 species of 11 rodent families are described. W hole, fixed lungs and silicone casts of the bronchial tree are tested for 2 3 characters, based on the distribution of lung lobes, the number and geome try of first order bronchi, the pulmonary blood supply, and lung symmetry. Ten lung morphotypes are recognized, seven of them representing one or more families: Castor type (Castoridae), Cryptomys type (Bathyergidae), Ctenoda ctylus type (Ctenodactylidae), Eliomys type (Gliridae), Myocastor type (Myo castoridae), Octodon type (Octodontidae and Echimyidae) and Rattus type (Sc iuridae, Muridae pt. and Dipodidae). The Hydromys type is found only in Hyd romys chrysogaster (Muridae), while Galea type A and B both appear in Galea musteloides (Caviidae). The data are phylogenetically analyzed by the prog ram PAUP 4.0 using as outgroup Lagomorpha or Insectivora. On the species le vel, there are no well-resolved cladograms. On the family level, the cladog rams do not contradict traditional rodent systematics with one exception: t he Caviidae do not fall within Caviomorpha or even within the Hystricomorph a, but form a sister group to Dipodidae (Myomorpha). This appears to be a r esult of convergence. The lungs of Gliridae are more similar to those of Mu ridae than to those of Sciuridae. Included in the ingroup, Oryctolagus (Lag omorpha) forms a clade with Caviidae + Dipodidae. Thus, the "Glires hypothe sis" is neither supported nor refuted. (C) 2000 Wiley-Liss, Inc.