The earliest known fisher (Mustelidae), a new species from the Rattlesnake Formation of Oregon

Abstract

Fishers are elusive carnivorans, with few occurrences in the fossil record. The origin and early evolution of fishers is unclear, but they likely originated in Asia. A new record of Pekania from the Rattlesnake Formation of Oregon represents the earliest known occurrence of a fisher, more than 5 million years earlier than other records in North America. This specimen has an unambiguous derived trait shared with other members of the genus, an external median rootlet on the upper carnassial. The age of this new find is inferred to be between 7.05 and 7.3 Ma, through radiometric and magnetostratigraphic dating. This age is supported by the presence of specimens of a shrew, Sorex edwardsi, and a rhinoceros, cf. Teleoceras, found at the same locality, as well as a rabbit, Hypolagus cf. vetus, and a tapir nearby, all of which are well known from early Hemphillian deposits. This find indicates that fishers were in both North America and Asia in the late Miocene, around the time of their divergence from other members of the clade as estimated from genetic data. Although it is over 7 million years old, this species shows remarkable similarity to extant P. pennanti, highlighting the highly conservative nature of gulonine mustelids. The Rattlesnake specimen is more robust than other fisher species, possibly representing something close to the ancestry of all fishers.

A new species ofGulofrom the Early Pliocene Gray Fossil Site (Eastern United States); rethinking the evolution of wolverines

“…However, those early occurrences of Plesiogulo precede the molecular estimates of divergence of the Gulo - Martes clade from other gulonines by nearly five million years. In contrast, the ages of recently described fossil specimens of Pekania ( Wang, Tseng & Takeuchi, 2012 ; Samuels & Cavin, 2013 ), and the new Gulo specimen described here, agree broadly with molecular divergence estimates of those extant genera ( Koepfli et al, 2008 ; Hughes, 2012 ; Sato et al, 2012 ; Li et al, 2014 ; Malyarchuk, Derenko & Denisova, 2015 ). In addition, the ages of Gulo sudorus and G. minor are similar to the latest records of Plesiogulo in North America and Asia.…”

“…Similarly, Malyarchuk, Derenko & Denisova (2015) estimated the divergence of Gulo and Martes to be around 5.6 Ma (95% CI [6.3–4.9] Ma). These estimates coincide with the earliest records of definite gulonine mustelids in the late Miocene, namely Pekania occulta from North America and P. palaeosinensis from Asia ( Wang, Tseng & Takeuchi, 2012 ; Samuels & Cavin, 2013 ), and Martes ginsburgi and M. wenzensis from Europe ( Stach, 1959 ; Wolsan, 1989a ; Anderson, 1994 ; Sato et al, 2003 ; Montoya, Morales & Abella, 2011 ). Each of these molecular estimates for the divergence of Gulo from other closely related gulonines ( Martes and Pekania ) are long after the earliest records of Plesiogulo , which date to the middle Miocene (MN6) of Turkey and Kazakhstan, between 15.2 and 12.5 Ma ( Schmidt-Kittler, 1976 ; Montoya, Morales & Abella, 2011 ).…”

“…The oldest confirmed gulonines are early records of fishers, including Pekania occulta from North America ( Samuels & Cavin, 2013 ) and P. palaeosinensis from Asia ( Wang, Tseng & Takeuchi, 2012 ). Pekania , which was formerly considered a subgenus of Martes , is distinguished by the presence of an external median rootlet on the upper P4 ( Anderson, 1994 ; Samuels & Cavin, 2013 ). Morphology of P. occulta , particularly the robust P4 with a large protocone, is similar to extant Gulo gulo and G. sudorus , suggesting that species may be similar to the shared ancestor of more recent Pekania and Gulo .…”

“…While some authors have considered Plesiogulo to be directly ancestral to Gulo ( Viret, 1939 ; Kurtén, 1970 ; Pasitschniak-Arts & Larivière, 1995 ), others considered such a line of descent to be unlikely ( Zdansky, 1924 ; Webb, 1969 ; Hendey, 1978 ; Harrison, 1981 ; Xu & Wei, 1987 ; Alcalá, Montoya & Morales, 1994 ; Montoya, Morales & Abella, 2011 ). Alternatively, some authors have suggested independent origins of Gulo and Plesiogulo , with Gulo originating from a fisher or marten-like ancestor in the late Miocene ( Samuels & Cavin, 2013 ) and Plesiogulo from an early Miocene ischyrictine like Iberictis ( Ginsburg & Morales, 1992 ; Alcalá, Montoya & Morales, 1994 ; Montoya, Morales & Abella, 2011 ).…”

A new hypercarnivorous mustelid (Mammalia, Carnivora, Mustelidae) from Batallones, late Miocene (MN10), Torrejón de Velasco, Madrid, Spain

“…Notable exceptions are the middle Miocene "Martes" sansaniensis (Lartet, 1851) from Sansan, MN6 (France) (Ginsburg 1961; Peigné 2012) and the late Miocene Pekania palaeosinensis (Zdansky, 1924) from China (Zdansky 1924;Wang et al 2012), which are known from several individuals. The genus Martes is incredibly diverse in the Miocene of Europe with more than a dozen species distributed from mammal biozones MN3 to MN14 (Morlo 1997;Ginsburg 1999;Nagel et al 2009;Montoya et al 2011;Peigné 2012), being its origin quite controversial (Anderson 1994;Sato et al 2003;Samuels & Cavin 2013;Li et al 2014). In view of this, abundant small marten-like mustelids from the early and middle Miocene of Eurasia and North America, which have been ascribed to "Martes", but show a different morphology are in need of thorough revision.…”