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Ornithorhynchus pelvis
 
Akidolestes in situ
Akidolestes manus pes
akidolestes rostrum

Akidolestes cifellii (Li and Luo 2006; Yixian Formation, Early Cretaceous. 124 mya; NIGPAS 139381A, B) nests as a basal toothed platypus in the large reptile tree, contra the original interpretation that considered the many similarities convergent. Akidolestes was derived from a sister to Kuehneotherium (see below) with long jaws containing many more teeth than is typical for mammals.

As a monotreme, Akidolestes was an egg-layer, yet providing nourishment for its hatchlings with an early form of milk secreting from ventral glands in its skin.

It probably was a fish and tadpole eater and had a thick, probably waterproof, furry coat.

Teeth Prior to the toothless condition found in Ornithorhynchus, phylogenetic predecessors developed more teeth. Akidolestes is one example. Keuhneotherium is yet another (see below).

 

Akidolestes

 
Obdurodon and kin

Obdurodon dicksoni (Archer et al. 1992; QM F20568; Oligocene to Mioncene) is a large toothed ancestor of the extant platypus.

 

Archer M, Jenkins FA, Hand SJ, Murray P, and Godthelp H 1992. Description of the skull and non-vestigial dentition of a Miocene platypus (Obdurodon dicksoni n. sp.) from Riversleigh, Australia, and the problem of monotreme origins. Platypus and Echidnas 15-27.

Chen M and Luo Z-X 2013. Postcranial skeleton of the Cretaceous mammal Akidolestes
cifellii
and its locomotor adaptations. Journal of Mammal Evolution 20:159–189.

Li G and Luo Z-X. 2006. A Cretaceous symmetrodont therian with some monotreme-like postcranial features. Nature, 439:195–200.

Shaw G 1799. The Naturalist's Miscellany.

wiki/Ornithorhynchus
wiki/Akidolestes
wiki/Obduron

 
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