Meridiolestida Temporal range:Late Cretaceous–Miocene PreꞒ Ꞓ O S D C P T J K Pg N PossibleEarly Cretaceous record
Skull ofNecrolestes
Life restoration and skull and jaws ofPeligrotherium
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Clade:	Cladotheria
Clade:	†Meridiolestida Rougier, 2011
Subgroups
See text

Meridiolestida is an extinct clade ofmammals known from theCretaceous andCenozoic ofSouth America and possiblyAntarctica. They represented the dominant group of mammals in South America during the Late Cretaceous.^[1] Meridiolestidans were morphologically diverse, containing both small insectivores such as the "sabretooth-squirrel"Cronopio,^[2] as well as the clade Mesungulatoidea/Mesungulatomorpha, which ranged in size from the shrew-sizedReigitherium to the dog-sizedPeligrotherium. Mesungulatoideans had highly modified dentition withbunodont (low and rounded) teeth, and were likely herbivores/omnivores.^[3]Meridiolestidans are generally classified withinCladotheria, more closely related to livingmarsupials andplacental mammals (Theria) than tomonotremes, barring one study recovering them as the sister taxa tospalacotheriid "symmetrodonts".^[4] However, more recent studies have stuck to the cladotherian interpretation.^[5][6] Within Cladotheria, they have often been placed in a group called Dryolestoidea together withDryolestida, a group of mammals primarily known from the Jurassic and Early Cretaceous of the Northern Hemisphere. However, some analyses have found this group to beparaphyletic, with the meridiolestidans being more or less closely related to therian mammals than dryolestidans are.^[6][7] Meridiolestidans differ from dryolestidans in the absence of a parastylar hook on themolariform teeth and the lack of aMeckelian groove.

Lakotalestes from the Early Cretaceous of North America, originally identified as a dryolestid, was noted in one paper to have a tooth morphology closer to that of meridiolestidans.^[8] A possible meridiolestidan is known from a tooth fragment, now lost, found in theLa Meseta Formation from the Eocene of theAntarctic Peninsula.^[9] The latest surviving meridiolestidan was the mole-like burrowing insectivoreNecrolestes from theMiocene of Patagonia.^[6]

• †Amarillodon^[10]
• †Austrotriconodon
• †Bondesius^[11]
• †Casamiquelia^[11]
• †Groebertherium?^[12]
• †Lakotalestes?^[8]
• †Paraungulatum^[11]
• †Quirogatherium^[11]
• †Solanutherium^[12]
• †Cronopioidea[11]^[13]
  • †Cronopio
  • †Leonardus?
  • †Necrolestes
• †Mesungulatoidea[13]
  • †Peligrotherium
  • †Reigitherium
  • †Coloniatherium
  • †Mesungulatum
  • †Orretherium

• Meridiolestidans
• Late Cretaceous first appearances
• Miocene extinctions
• Taxa named by Guillermo W. Rougier

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• Short description is different from Wikidata
• Articles with 'species' microformats