![]() Molar morphology is similar to that of the earliest North American basal marsupialiforms, such as Dakotadens, Iugomortiferum, Adelodelphys, Synbadelphys, and Pariadens ( 8, 10 – 12). Tribosphenic mammal with marsupialiform characters: Paraconid enlarged (but smaller than metaconid) and lingual (posterior molars), hypoconulid lingual and approximated to entoconid (but not twinned), well-developed entoconid, paracone and metacone of similar size and well separated, wide stylar shelf, stylar cusps D and C present (but small), protocone well developed (uncompressed), no lingual cingulum. The mammal from Archingeay-Les Nouillers is the oldest modern therian known so far in Europe, that is, the oldest European representative of the clade including metatherians and eutherians. The earliest therian mammals from Europe are Aegialodon and Tribactonodon from the Early Cretaceous of England ( 6, 7). The new mammal material reported here includes 4 marsupial-like tribosphenic fragmentary teeth, which provide information on the early European boreosphenids. The present study describes a new mammal from basal Cenomanian deposits of the Font-de-Benon quarry, at Archingeay-Les Nouillers, Charentes ( Fig. Some rare, indeterminate mammal teeth were reported from Charentes ( 3, 4), attesting to the presence of this group in the terrestrial ecosystems of the Mid-Cretaceous European archipelago. New Cenomanian localities in western France (Charentes) have yielded some rich coastal assemblages, including continental vertebrates ( 2, 3). In Europe, there is a major gap in the mammal fossil record for the Late Cretaceous, especially for the totally blank Aptian–Santonian interval ( 1). The early evolution of modern therians (i.e., metatherian and eutherian boreosphenidan mammals) is documented mainly in North America and Asia, where numerous rich Mid-Cretaceous microvertebrate localities are known. The main significance of the Archingeay-Les Nouillers mammal discovery is that it indicates that the beginning of the stem marsupialiforms history involved not only North America but also Europe, and that this early history in Europe remains virtually unknown. Concerning the paleobiogeographical history of the first stem marsupialiforms during the Albian–Cenomanian interval, 2 possible dispersal routes from an Asian metatherian ancestry can be proposed: Asia to Europe via North America and Asia to North America via Europe. In addition, the presence of a mammal with North American affinities in western Europe during the early Late Cretaceous provides further evidence of a large Euramerican biogeographical province at this age or slightly before. ![]() ![]() Both the plesiomorphic and autapomorphic characteristics of Arcantiodelphys among Marsupialiformes might be explained by an Eastern origin from Asian stem metatherians, with some in situ European evolution. Moreover, Arcantiodelphys is characterized by an original and precocious crushing specialization. This resemblance, which is plesiomorphic within “tribotherians,” makes Arcantiodelphys one of the most archaic known Marsupialiformes. Among marsupialiforms, it shows a closer resemblance to Dakotadens. shares several significant marsupial-like features ( s.l.) with marsupialiform taxa known from the North American Mid-Cretaceous. We report the discovery of mammalian tribosphenic teeth from the basal Cenomanian of southwestern France that we refer to a new primitive marsupial-like form identified as a basal taxon of Marsupialiformes, a new clade recognized here to include the crown group Marsupialia and primitive stem lineages more closely related to Marsupialia than to Deltatheroida.
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