Avizo reconstruction of Bone-cracking Borophagus coprolite lacm:vp:158714

Borophagine canids have long been hypothesized to be North American ecological ‘avatars’ of living hyenas in Africa and Asia, but direct fossil evidence of hyena-like bone consumption is hitherto unknown. We report rare coprolites (fossilized feces) of Borophagus parvus from the late Miocene of California and, for the first time, describe unambiguous evidence that these predatory canids ingested large amounts of bone. Surface morphology, micro-CT analyses, and contextual information reveal (1) droppings in concentrations signifying scent-marking behavior, similar to latrines used by living social carnivorans; (2) routine consumption of skeletons; (3) undissolved bones inside coprolites indicating gastrointestinal similarity to modern striped and brown hyenas; (4) B. parvus body weight of ~24 kg, reaching sizes of obligatory large-prey hunters; and (5) prey size ranging ~35–100 kg. This combination of traits suggests that bone-crushing Borophagus potentially hunted in collaborative social groups and occupied a niche no longer present in North American ecosystems.长期以来，学界普遍认为骨鬣犬亚科犬类（Borophagine canids）是非洲与亚洲现生鬣狗在北美生态系统中的生态“化身”，但迄今尚未发现与之对应的、类鬣狗啃食骨骼行为的直接化石证据。本研究报道了产自加利福尼亚晚中新世地层的罕见小骨鬣犬（Borophagus parvus）粪化石（coprolites，即石化粪便），并首次描述了明确的实证证据，证实这类掠食性犬类曾大量摄食骨骼。通过表面形貌分析、显微CT（micro-CT）扫描以及地层背景信息，我们得到以下五项发现：1）粪化石呈聚集分布，表明其存在气味标记行为，与现生群居食肉动物的粪堆行为模式一致；2）该类犬类日常会完整取食猎物骨骼；3）粪化石内部存在未被消化的骨骼碎屑，说明其消化系统与现生条纹鬣狗、棕鬣狗具有相似性；4）小骨鬣犬（B. parvus）的体重约为24千克，达到了专性大型猎物猎手的体型标准；5）其猎物体型范围约为35至100千克。上述特征的组合表明，具备骨骼啃食能力的骨鬣犬可能以群居协作的方式开展狩猎活动，并占据了如今北美生态系统中已不复存在的独特生态位。