Ornithothoraces Ornithothoraces Ornithothoraces is a group of avialans that includes all enantiornithes ("opposite birds") and the euornithes ("true birds"), which includes modern birds and their closest ancestors. The name Ornithothoraces means "bird thoraxes". This refers to the modern, highly advanced anatomy of the thorax that gave the ornithothoracines superior flight capability compared with more primitive avialans. This anatomy includes a large, keeled breastbone, elongated coracoids and a modified glenoid joint in the shoulder, and a semi-rigid rib cage. The earliest known members of the group are the enantiornitheans "Protopteryx fengningensis", "Eopengornis martini", and "Cruralispennia multidonta", as well as the euornithine "Archaeornithura
Plant anatomy Plant anatomy Plant anatomy or phytotomy is the general term for the study of the internal structure of plants. Originally it included plant morphology, the description of the physical form and external structure of plants, but since the mid-20th century plant anatomy has been considered a separate field referring only to internal plant structure. Plant anatomy is now frequently investigated at the cellular level, and often involves the sectioning of tissues and microscopy. Although some plant anatomy studies utilize a systems approach, such as the study of vascular tissues, plant anatomy is more classically divided into the following structural categories: