A Mesozoic gliding mammal from northeastern China.

Gliding flight has independently evolved many times in vertebrates. Direct evidence of gliding is rare in fossil records and is unknown in mammals from the Mesozoic era. Here we report a new Mesozoic mammal from Inner Mongolia, China, that represents a previously unknown group characterized by a highly specialized insectivorous dentition and a sizable patagium (flying membrane) for gliding flight. The patagium is covered with dense hair and supported by an elongated tail and limbs; the latter also bear many features adapted for arboreal life. This discovery extends the earliest record of gliding flight for mammals to at least 70 million years earlier in geological history, and demonstrates that early mammals were diverse in their locomotor strategies and lifestyles; they had experimented with an aerial habit at about the same time as, if not earlier than, when birds endeavoured to exploit the sky.

Characteristics of distribution and configuration of intracranial arachnoid membranes.

An understanding of the microsurgical anatomy of the arachnoid membranes and the subarachnoid cisterns is important in minimally invasive neurosurgery. But the topography of the arachnoid membranes has not been completely elucidated. The description of the distribution and the configuration of the intracranial arachnoid membranes is still a subject of controversy. In order to clarify this we examined eight Han Chinese adult human cadavers under an operating microscope. The dissections were performed with microsurgical instruments and techniques without staining of the intracranial structures nor injection of colored material into blood vessels. Twenty seven arachnoid membranes were identified. They were named according to their locations and attachment. They were divided into three groups: basal, convex and trabecular arachnoid membranes. They varied greatly in appearances and configurations. They were single-leaf structured except Liliequist's membrane, the chiasmatic membrane and the cerebellar precentral membrane. They were distributed extensively and unevenly and crisscrossed in the cranial cavity. The more complexly and intricately the blood vessels or the nerves converged or branched within the subarachnoid space, the more luxuriant and complex the arachnoid membranes and trabeculae were. The areas where the arachnoid membranes crowded most thickly in the subarachnoid space included the regions around the bifurcation of the internal carotid artery, the area around the hypothalamus, the interpeduncular cistern, the arachnoidal sheaths of the oculomotor nerve, the quadrigeminal cistern and the cisterna magna. Almost all the cranial nerves were encased by their own arachnoidal sheaths when they crossed the cisterns. The arachnoid membranes and trabeculae must be dissected or incised sharply during the operations. Thorough knowledge of the anatomy of the intracranial arachnoid membranes is valuable to take full advantage of the natural anatomic landmarks and interfaces formed by them during surgery.

Progress in radiology: historical review of the changing concepts of lower esophageal anatomy: 430 B.C.--1977.

Some of the classic studies on the anatomy of the lower esophagus are reviewed. In every case, the original sources have been consulted. The basis for a proposed anatomic description of the lower esophagus is established on the basis of the most modern research. The genesis of ideas on the anatomic nature of the cardia, phrenoesophageal membrane, esophageal pouches, esophageal sphincters, esophageal rings, gastroesophageal angle, flap valve, and cardiac notch is traced.