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Therian femora from the Late Cretaceous of Uzbekistan

100%

Chester S. G. B., Sargis E. J., Szalay F. S., Archibald J. D., Averianov A. O.

Acta Palaeontologica Polonica

2012

tom 57

nr 1

Femora referable to metatherians and eutherians recovered from the Bissekty Formation, Dzharakuduk, Kyzylkum Desert, Uzbekistan (90 Mya), are described. Fourteen isolated specimens were sorted based on size and morphology into groups that likely correspond to the species level or higher. Groups were then tentatively assigned to taxa known from teeth, petrosals, and/or other postcrania at these localities. One distal femur of a small arboreal metatherian, and several eutherian distal femora that probably represent zhelestids and/or zalambdalestids were identified. With the exception of one proximal femur that is similar in some aspects to the zalambdalestid Barunlestes, and a previously described multituberculate specimen, all other proximal femora from the Bissekty Formation exhibit a metatherian−like morphology. The dental record currently suggests the presence of twelve eutherian species and only one metatherian at Dzharakuduk, whereas the humeral and crurotarsal evidence supports the presence of at least two or four metatherian species, respectively. Given the sample size of the proximal femora, the morphological diversity present, and the overwhelming presence of eutherians at these localities, it is highly unlikely that the overwhelming majority of proximal femora actually represent metatherians. Therefore, this sample may suggest that the metatherian proximal femoral condition is primitive for Theria and that some eutherian taxa (probably including Zhelestidae, which are dentally most abundant at these localities) retain this condition.

Lower incisor in zalambdalestid mammals [Eutheria] and its phylogenetic implications

100%

Fostowicz-Frelik L., Kielan-Jaworowska Z.

Acta Palaeontologica Polonica

2002

tom 47

nr 1

Relationships of the specialized eutherian family Zalambdalestidae (Late Cretaceous, Asia) have long been debated. Beginning with suggestion of Van Valen (1964) and including the recent phylogenetic analysis of Archibald et al. (2001), a possible close relationship of Zalambdalestidae to Glires (Lagomorpha + Rodentia) has been repeatedly suggested (but see Meng and Wyss 2001). One of the characteristics of Glires is the structure of the lower incisor, which is enlarged and open−rooted. An open−rooted incisor has been documented in the oldest known zalambdalestid, Kulbeckia, but structure of this tooth has remained unknown for the Mongolian representatives of this family, Zalambdalestes and Barunlestes. Here we present evidence on the presence of an open−rooted first lower incisor in Zalambdalestes lechei and Barunlestes butleri; we argue, however, that structure of this incisor does not necessarily indicate relationship of Zalambdalestidae to Glires.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Archibald J. D.

1 Averianov A. O.

1 Chester S. G. B.

1 Fostowicz-Frelik L.

1 Kielan-Jaworowska Z.

1 Sargis E. J.

1 Szalay F. S.

1 2012

1 2002

Wyniki wyszukiwania

Therian femora from the Late Cretaceous of Uzbekistan

Lower incisor in zalambdalestid mammals [Eutheria] and its phylogenetic implications