Avizo reconstruction of Bone-cracking Borophagus coprolite lacm:vp:158713

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，学界假说鬣狗犬类（Borophagine canids）是非洲与亚洲现生鬣狗在北美生态系统中的生态对应"替身"，但迄今仍未发现与鬣狗式骨骼啃食行为相关的直接化石证据。我们报道了产自加利福尼亚州晚中新世地层的小恐犬（Borophagus parvus）稀有粪化石（coprolites，石化粪便），并首次描述了这类掠食性犬类曾大量摄食骨骼的明确实证。通过表面形态学分析、显微CT（micro-CT）扫描与背景地层关联信息研究，我们揭示了以下五项关键发现：（1）集中分布的粪堆表明其存在气味标记行为，与现生群居食肉动物的粪场行为高度相似；（2）该物种存在习惯性啃食猎物完整骨架的行为；（3）粪化石内部留存有未被消化的骨骼，证明其消化系统与现生条纹鬣狗、棕鬣狗具有相似性；（4）小恐犬（B. parvus）体重约24千克，达到了专性大型猎物猎手的体型标准；（5）其猎物体重范围约为35至100千克。上述一系列特征表明，具备骨骼粉碎能力的恐犬类可能以群居协作的方式开展狩猎活动，其所占据的生态位如今已在北美陆地生态系统中不复存在。