''Kollikodon'' is an extinct species of mammal, considered to be an early monotreme. It is known only from an opalised dentary fragment, with one

premolar The premolars, also called premolar Tooth (human), teeth, or bicuspids, are transitional teeth located between the Canine tooth, canine and Molar (tooth), molar teeth. In humans, there are two premolars per dental terminology#Quadrant, quadrant in ...

and two molars '' in situ'', as well as a referred

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

ry fragment containing the last premolar and all four molars. The

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s were found in the Griman Creek Formation at Lightning Ridge, New South Wales, Australia. ''Kollikodon'' lived in the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

period, during the

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

age (99–96 million years ago). Several other monotremes are known from the Griman Creek Formation, including '' Dharragarra'', '' Opalios'', '' Parvopalus'', '' Steropodon'', and '' Stirtodon''.

Etymology

''Kollix'' is an ancient Greek word (κολλίξ) for a bread roll. The strange teeth of ''Kollikodon'', when seen from above, resemble hot cross buns, traditionally toasted and eaten on

Good Friday Good Friday, also known as Holy Friday, Great Friday, Great and Holy Friday, or Friday of the Passion of the Lord, is a solemn Christian holy day commemorating the crucifixion of Jesus and his death at Calvary (Golgotha). It is observed during ...

. Originally, Michael Archer wanted to name it "Hotcrossbunodon", but met disapproval from his associates.

Description

Like ''Steropodon'', ''Kollikodon'' was a relatively large mammal for the

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

. The molars have a length of around 5.5 mm and a width of between about 4 and 6 mm. Based upon these data, the potential body length could be up to a metre. Assuming the accuracy of such a guess, ''Kollikodon'' would be a contender for the largest

mammal known, along with other possible giants such as '' Repenomamus'', '' Schowalteria'', and '' Bubodens''. Aside from its size, it is difficult to say what ''Kollikodon'' looked like. It is certain that its teeth were specialised to crush food, being perhaps a shellfish-eater or

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

. The description of the upper jaw showed that it was strongly specialised, with molars being subdivided into numerous rounded cuspules, some of which exhibit pits, possibly the result of crushing hard items.

In museums

Both ''Kollikodon'' and '' Steropodon'' can be found at the

Australian Museum The Australian Museum, originally known as the Colonial Museum or Sydney Museum. is a heritage-listed museum at 1 William Street, Sydney, William Street, Sydney central business district, Sydney CBD, New South Wales. It is the oldest natural ...

Sydney Sydney is the capital city of the States and territories of Australia, state of New South Wales and the List of cities in Australia by population, most populous city in Australia. Located on Australia's east coast, the metropolis surrounds Syd ...

, along with Eric, the

opal Opal is a hydrated amorphous form of silicon dioxide, silica (SiO2·''n''H2O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous (chemical) physical structure, it is classified as a ...

ised pliosaur.

References

External links

Australian Museum online: Lightning Ridge
Opal fossils from Oz.

Some observations on ''Hotcrossbunidon''.

{{Taxonbar, from=Q131958 Prehistoric monotremes Cretaceous mammals of Australia Monotypic prehistoric mammal genera Fossil taxa described in 1995