''Kryoryctes'' is a genus of prehistoric monotreme mammal
from the Early Cretaceous
) Eumeralla Formation
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 Museums Victoria
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 honour of Cadbury chocolate
s, referring to the dark colour 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 ulna
r 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
'' 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.
Pridmore ''et al'' determined on the basis of the expanded distal and proximal ends of its humerus that the animal was likely adapted for a burrowing lifestyle.
In an analysis of the burrows made by prehistoric animals in 2009, Martin concluded that ''Kryoryctes'', though the largest mammal known from the Lower Cretaceous
of Victoria, was probably too small for most of the burrows in this area. They do point out that on the basis of its assignment by the authors as a burrowing animal, ''K. cadburyi'' may be postulated as a tracemaker for other fossilised burrow-like structures.
The authors note that the humerus appears to be similar in morphology to extant tachyglossids
, but have not explicitly allied it with echidnas based on a number of important elements which differ between it and all known members of the family. They conclude that if ''K. cadburyi'' is in fact a monotreme, it is likely a stem
This affinity was disputed in 2009 by Canens ''et al'', which allied ''K. cadburyi'' more closely with echidnas. This analysis was rejected in turn by a further analysis by Phillips, Bennett and Lee in 2010, which found it again to be distinct from tachyglossids, though they do reiterate that there is some possibility that the humerus attributed to ''K. cadburyi'' could belong to the contemporaneous stem-monotreme ''Steropodon'', which is similarly-sized.
Category:Cretaceous mammals of Australia
Category:Prehistoric mammal genera
Category:Fossil taxa described in 2005