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Smithsonian National Museum of Natural History

Information about the Fossil Family Day Trilobite Model

A brown, oval-shaped trilobite fossil specimen embedded in a piece of rock. It has two eyes near the front of its body.
Trilobite fossil, Megistaspidella cf. M. obtusa. Smithsonian image.
  • Official Name: Megistaspidella cf. M. obtusa
  • Official Number in NMNH Collection: USNM PAL 558598
  • Formation unknown, Russia
  • Lower Ordovician Period
  • Size of Trilobite:
    • Length: 4 inches (10 cm)
    • Width: 2 inches (3 cm)
    • Height: 3/4 inches (1.8 cm)
  • GUID for this specimen record (links to the Paleobiology Collections Database): http://n2t.net/ark:/65665/3ae3ea84b-4cb3-4b51-9067-6e5ff15a3b6e. The data was captured by NMNH intern Seth Clark. 
A gray 3-D model print of a trilobite fossil with a yellow tag tied to it. The tag identifies the specimen in the model.
3-D model designed by students at HB Woodlawn Program, Arlington, Va., Public Schools

The real specimen of this trilobite is featured in the new David H. Koch Hall of Fossils: Deep Time. It belongs to the genus Megistaspis. This specimen has a special “sub-genus” name, Megistaspidella, along with a provisional (“cf.”) species name, “obtusa.”  The genus Megistaspis was very widespread; it is found all over the Northern Hemisphere, including the United States, Europe, and China. The age of this genus ranges between 478.6 to 449.5 million years, which makes it Lower Ordovician in age. It lived near the ocean floor, was medium-sized for a trilobite, and ate organic detritus that accumulated on the muddy seabed.

Trilobites are extinct, but lived on Earth for about 290 million years, achieving incredible abundance during from the Cambrian to Devonian. The oldest trilobite fossils are about 540 million years old, but even earlier trilobites may have lacked the hard body parts that fossilize. Trilobites are one of the most diverse groups of extinct organisms known. Their variety of body forms were undoubtedly specialized to different modes of life. Imagine tiny (1 mm long) trilobites floating in the ocean and filter-feeding on suspended detritus, juxtaposed with a large (60 cm, or 2 feet long) predatory trilobite crawling on the seafloor and catching worms. In spite of their diversity, trilobites shared a three-lobed body plan consisting of a central axis from head to tail with lobes on each side. All three lobes were protected by a hard covering (exoskeleton) which, depending on the species, was ornamented with ridges, spines, and color. The last trilobite lineages disappeared during the huge end-Permian extinction event (about 252 million years ago).