Lambdopsalidae is a family of extinct multituberculate mammals from the Late Paleocene of Asia. They are part of Taeniolabidoidea, a clade otherwise present in the Early Paleocene (and possibly the Late Cretaceous) of North America. The Lambdopsalids probably evolved from a single radiation that spread into Asia from North America in the mid-Paleocene or earlier. They are represented by the genera Lambdopsalis, Sphenopsalis and Prionessus.Williamson et al 2015Mao et al 2016, p 433 This group was first defined in 1978 by Chow and Tao Qi.Mao et al, 2016 pg 433
The Lambdopsalids were small mammals, with estimated adult body masses of about to .Wilson et al 2012, Supplemental table 5 They are notable for their enlarged teeth that implies adaptations towards leaf grazing, and adaptations for burrowing such as a short and flat snout, robust humeri, stiff neck and enlarged lower incisors.Kielan-Jorowowska and Qi, 1990Kielan-Jorowowska and Hurum, 2001 This group has a shared dental formula of Examples of Lambdopsalis are notable for offering direct evidence of hair and enamel and tooth prism patterns among multituberculates.Mao et al, 2015
Lambdopsalids lived during the Thanetian, the last stage of the Paleocene, with fossils ranging from 59-55 million years ago.Wilson et al 2012, Supplemental Tables 3 and 5 They disappeared around the PETM.
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References
Further reading
Wood, D. Joseph (2010). The Extinction of the Multituberculates Outside North America: a Global Approach to Testing the Competition Model (M.S.). The Ohio State University.