ISSN:
1573-7055
Keywords:
ear region
;
Jurassic
;
Multituberculata
;
petrosal
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract We describe three previously unreported specimens of petrosal bones of paulchoffatiid multituberculate mammals, collected from strata of Late Jurassic age in the Guimarota lignite mine of Leiria, west-central Portugal. The new fossils allow correction, supplementation, and confirmation of anatomical details, thus refining knowledge of general adaptation in the ear region among Jurassic multituberculates. Virtually all observed characters in the paulchoffatiid otic region are primitive relative to homologous features seen among Late Cretaceous and younger representatives of the Multituberculata; we recognize few unique otic specializations in paulchoffatiids that would preclude ancestry to later multituberculates. The plesiomorphic nature of paulchoffatiid ear regions provides no evidence in support of the hypothesis of a special, sister-group relationship between multituberculates and Late Cretaceous/Cenozoic marsupials plus placentals. Used in isolation, objective evidence derived from paulchoffatiid ear regions is consistent with interpretation of multituberculate divergence from other mammals predating the stem to living monotremes and postdating the stem to extinct morganucodontids. More broadly based comparative studies among Mesozoic mammals, however, suggest that independent acquisition of similarly advanced “mammalian” features was a pervasive theme among evolutionary histories of early mammals, probably including multituberculates. Although the phylogenetic position of multituberculates relative to other mammalian groups has yet to be unequivocally resolved, we suggest that a very early divergence of the group remains a distinct possibility.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01027599
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