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

<i>Brachypsalis</i> 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 <i>Brachypsalis modicus</i> 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 <i>B. modicus</i> shares with Colorado and Texas specimens in having relatively robust cheek teeth indicative of a hypocarnivorous lifestyle. Associations of <i>Brachypsalis</i> with nearshore marine and non-marine deposits in California indicate potential incorporation of nearshore or marine prey in their diet. <i>Brachypsalis modicus</i> 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.

短面鼬属（Brachypsalis）是一类中等体型的鼬科食肉目动物，其化石记录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）北美陆地哺乳动物阶地层中。除该类群在西海岸整体较为稀有外，绝大多数被归入该属的化石材料均高度破碎，因此难以开展可靠的分类学鉴定。本文首次报道了西海岸地区确凿的中型短面鼬（Brachypsalis modicus）化石记录：这批化石采自加利福尼亚州卡亚马谷卡连特组巴斯顿期上穹泉本地动物群，包含单个成年个体的多件颌骨与齿部碎片。加利福尼亚的B. modicus标本与科罗拉多州、德克萨斯州的同类标本一致，均具有相对粗壮的颊齿，表明其具备弱食肉性的生活方式。短面鼬属的化石在加利福尼亚与近岸海相及陆相沉积物伴生，这暗示其食谱中可能纳入了近岸或海洋猎物。中型短面鼬是一类栖息于海岸的陆生食肉目动物，其生态形态可能与现生水獭亚科鼬科（河獭）及/或浣熊科（浣熊）存在趋同，亦或是占据了加利福尼亚海岸现生食肉目动物群落中完全缺失的生态位。