2009年2月23日 · The image above provides most of the dorsal morphological terms used to define trilobite species, genera, families, and orders. Ventral (underside) morphology can also be important. For example, there are hypostomal attachment terms describing the way the hypostome (a hard mouthpart on the underside of a trilobite) attaches to the rest of the ...

Structure of Trilobites: The size varied from 8 mm of the fossils (Agnostus) to 75 cm (Uralichas). The body of trilobite was dorso-ventrally flattened and the most distinguishing feature was that two longitudinal lines divided the body into three lobes—median or axial part in the middle and two lateral or pleural parts on the sides (Fig. 18.32).

X-ray images of some trilobite specimens indicate a long, central (axial) structure typically considered an alimentary canal (intestines or gut). Sometimes the gut or its contents are also preserved as an axial structure. Only in extremely well-preserved agnostid specimens has a trace of a mouth and anus been detected.

Structure of Trilobites: The size varied from 8 mm of the fossils (Agnostus) to 75 cm (Uralichas). The body of trilobite was dorso-ventrally flattened and the most distinguishing feature was that two longitudinal lines divided the body into three lobes—median or axial part in the middle and two lateral or pleural parts on the sides

2008年3月25日 · Trilobites are a fossil group of extinct marine arthropods with a heavily calcified external skeleton that populated the oceans from about 520 million years ago to about 250 million years ago. Their name — meaning three-lobed — derives from the distinction between the elevated longitudinal axis and the flatter regions that bound it.

2009年8月6日 · The figure below shows the underside of a typical trilobite fossil, with cephalic, thoracic, and pygidial doublure, the rostral plate and associated sutures, and hypostome. The dark gray area represents the hollow interior of the dorsal shell.

In small groups, identify at least 5 morphological features of trilobites that you think are important for anatomical description. Mark the features on the trilobite diagram below, with lines pointing to them. Consider the variety of body forms shown in Figures 1 and 3.

Some trilobites were designed like a hydrodynamic rocket ship while others resembled nothing more than a primordial meatloaf. A few early species even featured a strange, multi-segmented opistothorax, which provided bold evidence of the trilobites' even more primitive, worm-like …

2013年11月14日 · Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest known groups of arthropods.

The name Trilobita is derived from the three (tri-) lobed structure of the exoskeleton, which has a raised central lobe (or axis) and a pair of side lobes, called pleurae. The trilobite body is also divided lengthwise into three regions or tagmata: a head or cephalon, a middle region (thorax) composed of several to many articulated segments ...