Bi, S.; Zheng, X.; Wang, X.; Cignetti, N.E.; Yang, S.; Wible, J.R.
taxonomy · range · morphology · topology
Primary description of STM33-5 and a morphology-matrix reassessment of Sinodelphys; the resulting topology remains dataset-dependent.
Near-complete holotype STM33-5 preserves ear and hyoid anatomy used in a morphology matrix that recovered Ambolestes and Sinodelphys within Eutheria, shifting the oldest sampled metatherian record to younger North American fossils; this is a dataset-dependent topology, not an observed placental–marsupial split or direct ancestor.
claim:event:ambolestes-therian-boundaryAmbolestes zhoui is bounded by near-complete holotype STM33-5 from the Lujiatun Unit of the Yixian Formation within an approximately 126–125 Ma interval; its eutherian placement is matrix-dependent and does not make it a direct placental ancestor.
claim:taxon:ambolestes:fossil-rangeTherian boundary evidence is an atlas navigation route spanning separately sampled Juramaia, Eomaia and Ambolestes records from approximately 161–124.1 Ma; it is not a taxonomic clade, continuous lineage or ancestor sequence, and its older endpoint inherits the disputed Juramaia provenance.
claim:taxon:therian-boundary-evidence:route-boundary