Temporal range: Late Cretaceous - Oligocene
|Fossil specimen of Leptictidium auderiense|
Leptictida (leptos iktis "small/slender weasel") is an extinct order of placental mammals. Their classification is contentious: according to cladistic studies, they may be (distantly) related to Euarchontoglires (rodents and primates and their relatives), although they are more recently regarded as first branch to split from basal eutherians. However, the most recent large scale cladistic analyses of eutherian mammals favor lepictidans as close to placental crown-clade.
The leptictids are a characteristic example of the non-specialized placental mammals that took part in the late Cretaceous-Paleocene evolutionary radiation, originally bunched together in the order Insectivora. The leptictids went extinct during the Oligocene, and their archaic cranium and dentition makes it difficult to determine their relationship to other groups. What is known of leptictid postcranial anatomy and lifestyle has been inferred from preserved middle Eocene Leptictidium specimens found at Messel, Germany. 
Judging from these specimens, lepticids were small placentals with a body length ranging between 60–90 cm. The head had a long and slender snout, probably featuring a short trunk which was probably used for scratching the undergrowth in search of insects and worms. The mouth's archaic dentition included two to three incisors, a canine, and V-shaped cheek-teeth - four premolars and three molars. 
Their forelegs were shortened but their hind legs elongated. While this anatomy is reminiscent of small kangaroos and jerboas, suggesting a jumping locomotion, the structure of the tarsal bones hints at a specialization for terrestrial running. Perhaps these animals were capable of both modes of locomotion; running slowly in search for food, and jumping quickly to avoid threats. Additionally, the Messel specimens feature a surprisingly long tail, unique among modern placental mammals, formed by forty vertebrae and probably used for balance. 
- Order Leptictida
- Family Leptictidae
- Family Pseudorhyncocyonidae
- Hooker, J. J. (2013). Origin and evolution of the Pseudorhyncocyonidae, a European Paleogene family of insectivorous placental mammals. Palaeontology, 56(4), 807-835.
- Wible, J.R., Rougier, G.W., Novacek, M.J. and Asher, R.J.. 2009. The eutherian mammal Maelestes gobiensis from the Late Cretaceous of Mongolia and the phylogeny of Cretaceous Eutheria. Bulletin of the American Museum of Natural History 327: 1-123.
- Augustí-Antón 2002, p 5
- Agustí, Jordi; Antón, Mauricio (2002). Mammoths, Sabertooths, and Hominids: 65 Millions Years of Mammalian Evolution in Europe. New York: Columbia University Press. ISBN 0-231-11640-3.
- Meehan, T. J.; Martin, Larry D. (2010). "New leptictids (Mammalia: Insectivora) from the Early Oligocene of Nebraska, USA". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 256 (1): 99–107. doi:10.1127/0077-7749/2010/0035.
- Novacek, Michael J. (1977) "A review of Paleocene and Eocene Leptictidae (Eutheria, Mammalia) from North America". PaleoBios 1(24)
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