Avizo reconstruction of Bone-cracking Borophagus coprolite lacm:vp:158710

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，学界假设恐犬亚科犬类（Borophagine canids）是非洲与亚洲现生鬣狗在北美生态位中的对应“生态化身”，但迄今尚无鬣狗式骨骼啃食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恐犬（Borophagus parvus）粪化石（coprolites），并首次描述了确凿证据，证实这类掠食性犬类曾大量摄入骨骼。通过表面形态学分析、显微CT（micro-CT）检测以及背景信息梳理，研究揭示了以下五点结论：（1）粪化石的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坑行为类似；（2）该类群会常规取食完整骨骼；（3）粪化石内部留存有未被消化的骨骼，表明其胃肠道生理特征与现生条纹鬣狗、棕鬣狗相似；（4）小恐犬的体重约为24千克，体型达到专性大型猎物猎手的水平；（5）其猎物体型范围约为35至100千克。上述特征组合表明，具备骨骼粉碎能力的恐犬（Borophagus）可能以协作性群居群体开展狩猎，并占据了现今北美生态系统中已不复存在的独特生态位。