Dyrosaurids were highly specialized, largely marine, relatives of living crocodylians, and one of the few archosaur lineages to survive the K-Pg extinction. Dyrosaurids lived during the Cretaceous to the Eocene and represent a unique combination of morphology and ecology not seen in living crocodylians. Little is known about their endocranial anatomy, leaving many questions about their neurosensory adaptations unaddressed. Recently, µCT (micro-computed tomography) scans were made of a well-preserved skull of Rhabdognathus, a Paleocene dyrosaurid from Mali. This marks the first time the braincase and neurosensory features of a dyrosaurid have been examined using CT. We focus our attention to three specific internal structures: the cranial endocast; the inner ear; and the paratympanic sinuses. The cranial endocast of Rhabdognathus revealed novel features including a unique conformation of its paratympanic system, a prominent dorsal venous system that communicates with the external skull table, extremely enlarged tympanic vestibules that meet at the midline of the endocranium, a prominent spherical cerebrum, and elongate olfactory tracts accounting for half the total endocast length. The bizarre laterally facing lateral Eustachian foramen of dyrosaurids is now understood to be a complex fossa including both a ventrally directed lateral Eustachian foramen and a laterally directed foramen for the basioccipital diverticulum. A novel median pterygopharyngeal canal was discovered connecting the pharynx to the adductor chamber. These revelations require a reinterpretation of the associated external foramina visible on the posterior of the skull in dyrosaurids and potentially their close relatives the pholidosaurids. The olfactory tract terminates in an enlarged olfactory region possessing complex bony projections—a unique morphology perhaps serving to increase surface area for olfaction. The inner ear of Rhabdognathus exhibits characteristics seen in both Pelagosaurus and Gavialis. The vestibule is spherical, as in Gavialis, but is significantly expanded. The semicircular canals are enlarged but pyramidal in shape as in the thalattosuchian Pelagosaurus. The proportion of the cochlear length to total endosseous labyrinth height is roughly 0.5 in Rhabdognathus implying that the hearing capabilities resemble that of thalattosuchians. A suite of expanded sense organs (e.g., bony olfactory lamina; hypertrophied vestibule of the inner ear), and the clear expansion of the cerebrum to a more symmetrical and spherical shape suggest that dyrosaurids possess neuroanatomical modifications facilitating an agile predatory near-shore ecology.

中文翻译：

---

高分辨率计算机断层扫描显示古新世鳄形横纹猴的脑壳解剖

腕龙是高度专业化的，主要是海洋生物，生活在其中，它们是活鳄鱼的近亲，也是为数不多的能够幸免于K-Pg灭绝的恐龙世系之一。Dyrosaurids生活在白垩纪至始新世期间，代表着形态和生态学的独特结合，而这在鳄鱼生活中是没有的。关于他们的颅内解剖学知之甚少，关于神经感觉适应的许多问题仍未解决。最近，对保存完好的颅骨Rhabdognathus头骨进行了µCT（微型计算机断层扫描）扫描，该颅骨是马里的古新世dyrosaurid。这标志着首次使用CT检查了dyrosaurid的脑部情况和神经感觉特征。我们将注意力集中在三个特定的内部结构上：颅内铸件；内耳; 和鼓室旁窦。Rhabdognathus的颅内铸件显示出新颖的特征，包括其鼓膜旁系统的独特构型，与外部颅骨表相通的突出的背静脉系统，在颅骨的中线相遇的鼓膜前庭极大，突出的球形大脑和细长的嗅觉管道占内窥镜总长度的一半。现已知道，怪异的棘突侧向的侧向咽鼓孔侧向孔是复杂的窝，包括腹侧的咽鼓侧孔和基底枕憩室的侧向孔。发现了一条新型的咽咽正中管，将咽部与内收肌相连。这些发现需要重新解释在旋毛龙的头骨后部可见的相关外部孔眼，并可能重新解释它们的近亲。嗅觉管道终止于一个扩大的嗅觉区域，该区域具有复杂的骨突出物-独特的形态可能有助于增加嗅觉的表面积。Rhabdognathus的内耳表现出在Pelagosaurus和Gavialis中都看到的特征。前庭是球形的，如在Gavialis中一样，但显着扩展。半球形运河如塔拉托苏里式梭龙一样扩大，但呈金字塔形。在横纹猴中，耳蜗长度占总骨内迷宫高度的比例大约为0.5，这表明其听觉能力类似于tha壳动物的听觉能力。一套扩大的感觉器官（例如，骨嗅层; 内耳肥大的前庭），以及大脑清楚地扩展为更对称和球形的形状，表明旋龙科具有神经解剖学修饰，有助于敏捷的掠食性近岸生态系统。