Data from: Trace fossils of possible parasites inside the gut contents of a hadrosaurid dinosaur, Upper Cretaceous Judith River Formation, Montana

Tiny sinuous trace fossils have been found within probable gut contents of an exceptionally preserved specimen of a hadrosaurid dinosaur, Brachylophosaurus canadensis, from the Judith River Formation of Montana. Approximately 280 examples of the trace fossils were observed in 19 samples of gut region material. The tubular structures typically are about 0.3 mm across. Many have thin calcareous linings or layers, and some exhibit fine surficial striae. At least two dozen of these trace fossils share walls with adjacent tubular traces, and this association can extend for several millimeters. While the trace fossils share some characteristics with fine rhizoliths, these features are most consistent with tiny burrows, or possibly body impressions, of worms (vermiform organisms) of uncertain biologic affinity. Such trace fossils have not been reported previously, and herein described as Parvitubulites striatus n. gen. n. sp. Either autochthonous (parasites) or allochthonous (scavengers) worms may have created the trace fossils, but taphonomic factors suggest that autochthonous burrowers are more likely. Several lines of evidence, such as constant diameters and matching directional changes, suggest that the paired trace fossils were made by two individuals moving at the same time, which implies sustained intraspecific contact. Parvitubulites striatus provides a rare record of interactions between terrestrial, meiofaunal-sized, soft-bodied invertebrates and a dinosaur carcass. The evidence that the worms may have parasitized a living hadrosaur and subsequently left traces of intraspecific behavior between individual worms adds unique information to our understanding of Mesozoic trophic interactions.在美国蒙大拿州朱迪思河组（Judith River Formation）出土的一具保存异常完好的鸭嘴龙科（Hadrosauridae）恐龙——加拿大短冠龙（Brachylophosaurus canadensis）的疑似肠道内含物中，发现了细小的弯曲遗迹化石。研究人员在19份肠道区域标本中共观察到约280枚这类遗迹化石，其管状结构直径通常约0.3毫米。多数遗迹化石带有薄钙质衬层，部分表面可见精细的表面细条纹。至少24枚遗迹化石与相邻的管状遗迹共享管壁，这种关联结构可延伸数毫米。尽管这类遗迹化石与细根迹化石（rhizoliths）存在部分相似特征，但它们的形态特征更符合亲缘关系不明的蠕虫（蠕形生物，vermiform organisms）的小型潜穴，或是躯体印痕。这类遗迹化石此前未见报道，本文将其命名为条纹小管迹（Parvitubulites striatus）新属新种（n. gen. n. sp.）。这些遗迹化石可能由原地生活的寄生虫类蠕虫，或是异地来源的食腐类蠕虫形成，但埋藏学（taphonomic）证据显示，原地潜居的蠕虫可能性更高。多项证据——如管径恒定、运动方向变化一致——表明成对出现的遗迹化石由两只同时活动的蠕虫形成，这暗示它们存在持续的种内接触。条纹小管迹（Parvitubulites striatus）为陆生小型底栖生物（meiofaunal-sized）体型的软躯体无脊椎动物与恐龙尸体之间的相互作用提供了罕见的化石记录。这些蠕虫可能曾寄生于活的鸭嘴龙体内，且后续还留下了个体间种内行为的痕迹，这一发现为我们理解中生代营养级相互作用提供了独特的研究视角。