''Leonardus'' is an extinct mammal genus from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger 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 ''creta'', ...

( Late Santonian to

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval ...

) of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

.''Leonardus''
at Fossilworks.org It is a meridiolestidan

dryolestoid Dryolestida is an extinct order of mammals, primarily and possibly exclusively known from the Jurassic and Cretaceous. They are considered members of the clade Cladotheria, close to the ancestry of therian mammals. It is also believed that they ...

, closely related to the also

'' Cronopio'' and the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

Necrolestes ''Necrolestes'' ("grave robber" or "thief of the dead") is an extinct genus of mammals, which lived during the Early Miocene in what is now Argentine Patagonia. It is the most recent known genus of Meridiolestida, an extinct group of mammals m ...

''.Guillermo W. Rougier, John R. Wible, Robin M. D. Beck and Sebastian Apesteguía (2012). "The Miocene mammal Necrolestes demonstrates the survival of a Mesozoic nontherian lineage into the late Cenozoic of South America". Proceedings of the National Academy of Sciences of the United States of America. 109 (49): 20053–20058. doi:10.1073/pnas.1212997109.Alexander O. Averianov, Thomas Martin and Alexey V. Lopatin (2013). "A new phylogeny for basal Trechnotheria and Cladotheria and affinities of South American endemic Late Cretaceous mammals". Naturwissenschaften. 100 (4): 311–326. doi:10.1007/s00114-013-1028-3.

Description

''Leonardus'' is a fairly small mammal, similar in size to ''

''. It is known from two specimens, the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

MACN-RN 172, composed of a left

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates 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. T ...

, four associated molariform

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, t ...

and two pairs of alveoli, and MACN-RN 1907, a right mandible with two molariforms. Said molariforms are vaguely peg-like, with a dome-like stylocone.

Discovery

''Leonardus'' is currently only known from the

Los Alamitos Formation The Los Alamitos Formation is a geological formation of the North Patagonian Massif in Rio Negro Province, northwestern Patagonia, Argentina, whose strata date back to the Late Cretaceous (Late Campanian to Maastrichtian). Dinosaur remains are amo ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. The holotype was found in 1990, while the second specimen was described more recently in 2010.

Classification

''Leonardus'' was originally referred to

Dryolestidae Dryolestidae is an extinct family of Mesozoic mammals, known from the Middle Jurassic to the Early Cretaceous of the North Hemisphere. The oldest known member, '' Anthracolestes'', is known from the Middle Jurassic Itat Formation of Western Siber ...

, but the lack of a parastylar hook on the molariforms, as well as a few features of the stylocone, suggest that it was grouped with other

n and

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

n dryolestoids at the exclusion of Laurasian species, in a clade known as Meridiolestida.Laura Chornogubsky, New remains of the dryolestoid mammal Leonardus cuspidatus from the Los Alamitos Formation (Late Cretaceous, Argentina), Article in Paläontologische Zeitschrift 85(3):343-350 · September 2011 DOI: 10.1007/s12542-010-0095-4 Within Meridiolestida, it consistently groups with ''

'' and '' Cronopio''.

Paleobiology

''Leonardus teeth are noted as being unique among dryolestids and the animal would have had an orthal and transverse jaw-stroke with tooth-to-tooth shearing, though no further comments have been made on its diet.

References

{{Taxonbar, from=Q28045585 Dryolestida Cretaceous mammals of South America Late Cretaceous tetrapods of South America Santonian life Campanian life Maastrichtian life Late Cretaceous genus first appearances Late Cretaceous genus extinctions Cretaceous Argentina Fossils of Argentina Los Alamitos Formation Fossil taxa described in 1990 Prehistoric mammal genera