Triconodon

Triconodon Temporal range: Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Triconodon mordax jaw, Richard Owen 1861
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	†Eutriconodonta
Family:	†Triconodontidae
Genus:	†Triconodon Owen, 1859
Type species
†Triconodon mordax Owen, 1859
Other species
†T. averianovi Jäger, Cifelli & Martin, 2020
Synonyms
Triacanthodon Owen, 1871

Triconodon ("three-coned tooth") is a genus of extinct

The type specimen of Triconodon is BMNH 47764, a single mandible found in the Purbeck Group, England, pertaining to the type species (T. mordax).^[1] Since then, several other specimens have been found in this region, mostly represented by skulls and jaws, making it the most common mammal fossils in this area of Britain.^[2] These deposits date to the earliest Cretaceous, to the Berriasian at around 145-140 million years of age. The second species, T. averianovi, was named in 2020 based on fossils found in the Berriasian-aged Lulworth Formation, England.^[3]

A single specimen has also been found in the Champblanc Quarry in France, dating to roughly the same age. It is unclear if it belongs to the same species as the British form, though given the close temporal and geographical proximity it seems likely.^[4]

Classification

Triconodon is known from two species, represented only by T. averianovi and T. mordax (though see above). Besides being the type genus and species for Eutriconodonta as seen above, it is also the type genus and species for Triconodontidae, erected in 1887 by Charles Marsh.^[5] Within this group it is usually recovered in a basal position, sometimes as sister taxa to Trioracodon,^[6][7] or closer to the group containing the rest of the clade, rendering Trioracodon in the basalmost position.^[8]

Biology

Like most eutriconodonts, Triconodon was probably a

Triconodon is one of the few Mesozoic mammals with direct evidence of tooth eruption, thanks to a broad ontogenetic range presented by the specimens. Through several juvenile specimens we can document the replacement of its lower fourth premolar, erupting and coming into use when at least three out of its four molars were already fully erupted.^[11]

Brain

One of the earliest fossil brain endocast studies has been performed for Triconodon.^[11] The olfactory lobe is large, with a teardrop-shaped outline, suggesting a well developed sense of smell.

The cerebral hemisphere is long, oval and flat, lacking the inflated appearance present in

What this indicates about the animal's intelligence is currently unclear, though its overall brain proportions are somewhat smaller than those of more derived mammals like multituberculates and therians.[12]

References