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Temporal range: Late Cretaceous–Miocene Possible Early Cretaceous record
Skull of Necrolestes
Life restoration and skull and jaws of Peligrotherium
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Cladotheria
Clade: Meridiolestida
Rougier, 2011

See text

Skull of Cronopio

Meridiolestida is an extinct clade of mammals known from the Cretaceous and Cenozoic of South America and possibly Antarctica. 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-sized Reigitherium to the dog-sized Peligrotherium. Mesungulatoideans had highly modified dentition with bunodont (low and rounded) teeth, and were likely herbivores/omnivores.[3] Meridiolestidans are generally classified within Cladotheria, more closely related to living marsupials and placental mammals (Theria) than to monotremes, barring one study recovering them as the sister taxa to spalacotheriid "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 with Dryolestida, a group of mammals primarily known from the Jurassic and Early Cretaceous of the Northern Hemisphere. However, some analyses have found this group to be paraphyletic, 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 the molariform teeth and the lack of a Meckelian 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 the La Meseta Formation from the Eocene of the Antarctic Peninsula.[9] The latest surviving meridiolestidan was the mole-like burrowing insectivore Necrolestes from the Miocene of Patagonia.[6]



  1. ^ Defler, Thomas (2019), "Ancient Mammals of Gondwanan South America", History of Terrestrial Mammals in South America, Topics in Geobiology, vol. 42, Cham: Springer International Publishing, pp. 29–44, doi:10.1007/978-3-319-98449-0_2, ISBN 978-3-319-98448-3, S2CID 134806427, retrieved 2022-01-15
  2. ^ Guillermo W. Rougier; Sebastián Apesteguía; Leandro C. Gaetano (2011). "Highly specialized mammalian skulls from the Late Cretaceous of South America". Nature. 479 (7371): 98–102. Bibcode:2011Natur.479...98R. doi:10.1038/nature10591. PMID 22051679. S2CID 4380850, supplementary information.
  3. ^ Harper, Tony; Adkins, Caleb; Rougier, Guillermo (2022). "Reconstructed masticatory biomechanics of Peligrotherium tropicalis, a non-therian mammal from the Paleocene of Argentina". Acta Palaeontologica Polonica. 67. doi:10.4202/app.00912.2021. ISSN 0567-7920. S2CID 247881626.
  4. ^ Averianov, Alexander O.; Martin, Thomas; Lopatin, Alexey V. (2013). "A new phylogeny for basal Trechnotheria and Cladotheria and affinities of South American endemic Late Cretaceous mammals". Naturwissenschaften. 100 (4): 311–326. Bibcode:2013NW....100..311A. doi:10.1007/s00114-013-1028-3. PMID 23494201. S2CID 18504005.
  5. ^ Martinelli, Agustin; Chornogubsky, Laura; Abello, María; I. Goin, Francisco; Reguero, Marcelo (2014). The first non-therian dryolestoid from Antarctica. 2014 SCAR Open Science Conference. Auckland, New Zealand. doi:10.13140/2.1.2770.8805.
  6. ^ a b c O’Meara, Rachel N.; Thompson, Richard S. (2014). "Were There Miocene Meridiolestidans? Assessing the Phylogenetic Placement of Necrolestes patagonensis and the Presence of a 40 Million Year Meridiolestidan Ghost Lineage". Journal of Mammalian Evolution. 21 (3): 271–284. doi:10.1007/s10914-013-9252-3. S2CID 880380.
  7. ^ Lasseron, Maxime; Martin, Thomas; Allain, Ronana; Haddoumi, Hamid; Jalil, Nour-Eddine; Zouhri, Samir; Gheerbrant, Emmanuel (2022). "An African Radiation of 'Dryolestoidea' (Donodontidae, Cladotheria) and its Significance for Mammalian Evolution" (PDF). Journal of Mammalian Evolution. 29 (4): 733–761. doi:10.1007/s10914-022-09613-9. S2CID 249324444.
  8. ^ a b Martin, Thomas; Averianov, Alexander O.; Schultz, Julia A.; Schwermann, Achim H.; Wings, Oliver (2021). "A derived dryolestid mammal indicates possible insular endemism in the Late Jurassic of Germany". The Science of Nature. 108 (3): Article number 23. Bibcode:2021SciNa.108...23M. doi:10.1007/s00114-021-01719-z. PMC 8126546. PMID 33993371.
  9. ^ Gelfo, Javier N.; Goin, Francisco J.; Bauzá, Nicolás; Reguero, Marcelo (30 September 2019). "The fossil record of Antarctic land mammals: Commented review and hypotheses for future research". Advances in Polar Science: 274–292. doi:10.13679/j.advps.2019.0021.
  10. ^ Martin, T.; Goin, F. J.; Schultz, J. A.; Gelfo, J. N. (2022). "Early Late Cretaceous mammals from southern Patagonia (Santa Cruz province, Argentina)". Cretaceous Research. 133: 105127. Bibcode:2022CrRes.13305127M. doi:10.1016/j.cretres.2021.105127. S2CID 245549530.
  11. ^ a b c d e Rougier, G. W.; Martinelli, A. G.; Forasiepi, A. M. (2021). "Dryolestoids". Mesozoic Mammals from South America and Their Forerunners. Springer Earth System Sciences. pp. 201–260. doi:10.1007/978-3-030-63862-7_6. ISBN 978-3-030-63860-3. S2CID 242314101.
  12. ^ a b Connelly, B. E.; Cardozo, M. S.; Montgomery, J. D.; Rougier, G. W. (2024). "New mammals from the Upper Cretaceous Allen Formation (Patagonia, Argentina) and reassessment of meridiolestidan diversity". Cretaceous Research. 162: 105935. doi:10.1016/j.cretres.2024.105935.
  13. ^ a b Rougier, G. W.; Turazzinni, G. F.; Cardozo, M. S.; Harper, T.; Lires, A. I.; Canessa, L. A. (2021). "New Specimens of Reigitherium bunodontum from the Late Cretaceous La Colonia Formation, Patagonia, Argentina and Meridiolestidan Diversity in South America". Journal of Mammalian Evolution. 28 (4): 1051–1081. doi:10.1007/s10914-021-09585-2. S2CID 254704047.