Kryoryctes

Kryoryctes Temporal range: Early Cretaceous
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	?Monotremata
Genus:	†Kryoryctes
Species:	†K. cadburyi
Binomial name
Kryoryctes cadburyi Pridmore, Rich, Vickers-Rich & Gambaryan, 2005

Kryoryctes is a genus of prehistoric monotreme mammal from the Early Cretaceous (Albian) Eumeralla Formation of Victoria, Australia, from the Otway Group of Dinosaur Cove. It is known only from a partial right humerus, estimated at 106 million years old, and contains one species, K. cadburyi. The holotype, NMV P20894, was described in 2005 and is currently housed in the Museum Victoria Palaeontological Collection.

The genus name derives from Greek "kryo", meaning low temperature, in reference to the seasonal coldness common to the paleo-environment of Dinosaur Cove, and from the Greek "oryktes", meaning one who digs, referring to the robust humerus from which a fossorial lifestyle has been inferred. The species is named in honor of Cadbury chocolates, referring to the dark color of the holotype, as well as for the "recognition and support provided" by Cadbury chocolates during the field work that resulted in discovery of the specimen.

K. cadburyi is distinguished by the authors from all extant monotremes, as well as from fossil tachyglossids, by the presence of a broad, marginated, shallow bicipital sulcus on the proximal humerus, which extends distally onto the waist of the bone. It is also distinguished by the presence of a trochlear-form ulnar articulation and a distal olecranon fossa. Pridmore et al find these features sufficient to distinguish it from Steropodon as well as other non-tachyglossid but similar monotremes such as Obdurodon, Kollikodon, Teinolophos and Monotrematum. The bone itself measures a total length of 46 mm, though the authors point out that it is likely missing around an eighth of its true length and suffers from some amount of abrasion, and estimate the original length at around 50 mm in life.

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