Triconodonta

Taxobox
name = Triconodonts
fossil_range = Late Triassic - Late Cretaceous

---

image_width = 250px
image_caption = "Gobiconodon"
regnum = Animalia
phylum = Chordata
classis = Mammalia
subclassis = Allotheria
ordo = Triconodonta
subdivision_ranks = Families
subdivision =
Amphilestidae
Eutriconodontidae
Jeholodentidae
Gobiconodontidae
Klameliidae
Repenomamidae
Triconodontidae

Triconodonta (also known as Eutriconodonta) is the generic name for a group of early mammals which were close relatives of the ancestors of all present-day mammals. Triconodonts lived between the Triassic and the Cretaceous. They are one of the groups that can be classified as mammals by any definition. Several other extinct groups of Mesozoic animals that are traditionally considered to be mammals are now placed just outside Mammalia by those who advocate a 'crown-group' definition of the word "mammal". [Traditionally, membership in Mammalia is diagnosed by the presence of a single dominant jaw joint, in which the dentary contacts the squamosal. However, taxonomists debate whether established names, such as Mammalia, should correspond to the clade which is closest to the traditional definition or, alternatively, should be restricted to the 'crown-group' (which includes only descendants of the most recent common ancestor shared by all "living" member species and excludes any fossil forms which diverged at an earlier stage, even if they meet the traditional criteria). Supporters of the crown-group approach refer to the broader grouping as the Mammaliformes or Mammaliaformes, whereas traditionalists describe the entire assemblage as "mammals". For a summary of the argument and issues, see Benton 2005: 289.]

Their name, meaning "Three conical teeth", is based on one of their fundamental characteristics. They had the typical morphology of the proto-mammals: small, furry, tetrapod animals with long tails. They probably had a nocturnal lifestyle to avoid dinosaur predators, coming out from their burrows after dusk to hunt for small reptiles and insects. However, recent evidence from China suggests that some triconodonts were indeed able to take on small dinosaurs. [http://www.newscientist.com/channel/life/dn6874.html] .

Notes

References

* Michael J. Benton. 2005. "Vertebrate Palaeontology". 3rd ed. Oxford: Blackwell Publishing. ISBN 0-632-05637-1
* Jeff Hecht. [http://www.newscientist.com/channel/life/dn6874.html Large mammals once dined on dinosaurs] . NewScientist.com news service, 12 January 2005.