MADRID – A team of Spanish scientists has found rare trilobite fossils with extraordinarily well-preserved soft tissue and legs, revealed a study published by “Nature” on Tuesday.
Trilobites were a diverse group of marine arthropods that populated the seas and oceans of the Paleozoic era, 541-252 million years ago.
The study, led by Juan Carlos Gutierrez-Marco, said in its abstract that trilobites’ “soft-part anatomy is only known from a few exceptionally-preserved specimens found in a handful of localities.”
The team discovered three large specimens of the asaphid trilobite Megistaspis (Ekeraspis) hammondi species in southern Morocco, whose appendages and digestive tracts had been incredibly preserved for over 450 million years.
Of the more than 20,000 known species of trilobites, some had smooth exoskeletons and others sported spiky exteriors.
They varied greatly in size, ranging from a few millimeters in length to several dozen centimeters (the largest specimen found to date, Isotelus rex, had a length of 72 centimeters, or 28.4 inches).
In general, only exoskeletons were preserved in trilobite fossils, although this find, in Morocco’s Lower Ordovician Fezouata Konservat-Lagerstätte, offers a rare glimpse into the anatomy of these extinct creatures.
Lagerstätten (German for “storage places”) are sedimentary deposits whose geology and nature enables an extraordinary preservation of tissues.
In these few locations, soft tissues are occasionally preserved by anoxic environments with few bacteria, in contrast to the typical decomposition and traceless disappearance of soft organic matter seen in most fossils.
“The Moroccan Fezouata Biota is the most important Ordovician Burgess Shale-type Lagerstätte known to date, having produced a very diverse marine assemblage,” the article’s introduction said.
“Preservation usually involves pyritization and subsequent weathering to iron oxides, thus the reddish colors of the fossils,” it added.
The study, titled “Digestive and appendicular soft-parts, with behavioral implications, in a large Ordovician trilobite from the Fezouata Lagerstätte, Morocco,” was co-authored by Spanish researchers Diego Garcia-Bellido and Isabel Rabano, as well as Portuguese geologist Artur Agostinho de Abreu e Sa.