A new taeniolabidoid multituberculate ( M ammalia) from the middle P uercan of the N acimiento F ormation, N ew M exico, and a revision of taeniolabidoid systematics and phylogeny

Multituberculates were amongst the most abundant and taxonomically diverse mammals of the late M esozoic and the P alaeocene, reaching their zenith in diversity and body size in the P alaeocene. Taeniolabidoidea, the topic of this paper, includes the largest known multituberculates, which possess highly complex cheek teeth adapted for herbivory. A new specimen from the early P alaeocene (middle P uercan; biochron P u2) of the N acimiento F ormation, N ew M exico represents a new large‐bodied taeniolabidoid genus and species, Kimbetopsalis simmonsae . A phylogenetic analysis to examine the relationships within Taeniolabidoidea that includes new information from Kimbetopsalis gen. et sp. nov. and gen. nov. and from new specimens of C atopsalis fissidens , first described here, and data from all other described N orth A merican and A sian taeniolabidoids. This analysis indicates that C atopsalis is nonmonophyletic and justifies our transfer of the basal‐most taeniolabidoid ‘ C atopsalis ’ joyneri to a new genus, Valenopsalis . Kimbetopsalis and T aeniolabis form a clade ( T aeniolabididae), as do the A sian L ambdopsalis , S phenopsalis , and possibly also P rionessus ( L ambdopsalidae). T aeniolabidoids underwent a modest taxonomic radiation during the early P alaeocene of N orth A merica and underwent a dramatic increase in body size, with T aeniolabis taoensis possibly exceeding 100 kg. T aeniolabidoids appear to have gone extinct in N orth A merica by the late P alaeocene but the appearance of lambdopsalids in the late P alaeocene of A sia suggests that they dispersed from N orth A merica in the early to middle P alaeocene.