The first record of Brachypsalis modicus (Carnivora, Mustelidae) in California from the Cuyama Valley (Caliente Formation, Middle Miocene)

Brachypsalis are medium-sized mustelid carnivorans known mostly from Hemingfordian to Clarendonian North American Land Mammal Age deposits in the Great Basin and Great Plains regions of North America. In addition to its general rarity along the west coast, most materials assigned to this genus are highly fragmentary and consequently, confident taxonomic assignment is difficult. Here I report on the first confirmed record of Brachypsalis modicus from the west coast. Several jaw and dental fragments of a single adult individual are described from the Barstovian Upper Dome Spring Local Fauna of the Caliente Formation, Cuyama Valley, California. The California record of B. modicus shares with Colorado and Texas specimens in having relatively robust cheek teeth indicative of a hypocarnivorous lifestyle. Associations of Brachypsalis with nearshore marine and non-marine deposits in California indicate potential incorporation of nearshore or marine prey in their diet. Brachypsalis modicus represents a medium-sized, coastal terrestrial carnivoran that may be ecomorphologically convergent with extant lutrine mustelids (river otters) and/or procyonids (raccoons), or alternatively, a niche that is entirely missing from extant carnivoran assemblages along the California coast.

短鼻鼬属（Brachypsalis）是一类中型鼬科食肉目动物，其化石主要发现于北美大盆地与大平原地区的赫明福德期（Hemingfordian）至克拉伦登期（Clarendonian）北美陆地哺乳动物时代地层中。除西海岸地区该属化石整体较为稀有外，绝大多数归入该属的标本都高度破碎，因此可靠的分类学鉴定颇具难度。本文报道了西海岸地区首个确凿的温和短鼻鼬（Brachypsalis modicus）化石记录：其标本采自加利福尼亚州卡亚马谷卡里恩特组的巴斯特顿期上穹顶泉本地动物群，为单个成年个体的数件颌骨与牙齿碎片。此次加利福尼亚发现的温和短鼻鼬标本，与科罗拉多州、得克萨斯州的同类标本一样，拥有相对粗壮的颊齿，暗示其具有弱食肉性的生活方式。在加利福尼亚州，短鼻鼬属化石与近岸海相及非海相沉积物伴生，这表明其食谱中可能包含近岸或海洋猎物。温和短鼻鼬是一类中型沿海陆生食肉动物，其生态形态或与现生水獭亚科（河獭）及浣熊科（浣熊）类群存在趋同演化，亦或占据了加利福尼亚沿海现生食肉动物类群中完全缺失的生态位。