Biggest Trilobite Sea Beasts Found ... in Swarms

Galvasean

Good news for all you trilobite fans out there (which I assume is everyone).

Christine Dell'Amore wrote:

Talk about ruining a good beach day.

Swarms of up to a thousand giant trilobites—extinct marine arthropods such as this 35-inch-long (90-centimeter-long) fossil specimen—roamed shallow prehistoric seas, new fossils show.

The 465-million-year-old fossils, found recently in northern Portugal, are of the largest trilobites ever discovered.

The trilobites may have clustered to mate and molt—shedding old exoskeletons as new ones grew in—as well as avoid predators, scientists say.

The benefits of swarming may explain why these distant relatives of horseshoe crabs were among the most widespread arthropods of the Paleozoic era (542 to 251 million years ago).

Even so, finding complete specimens bigger than 12 inches (30 centimeters) is rare—making the new find "remarkable," the study authors write in a recent edition of the journal Geology.

The critters lived at high latitudes near Gondwana—a huge southern supercontinent—and close to the South Pole during the Ordovician period.

This oxygen-rich, cold-water habitat may have contributed to these trilobites' gigantic sizes, the authors added.

But repeated, sudden, "lethal" influxes of oxygen-starved water may have led to the newfound trilobites' demise millions of years ago.

Photo by Artur Sá.

taram

90cm long :eek: Woah, never seen any samples bigger than about 20cm, 90cm is scary tbh.

marco_polo

Oops, I always thought they were about the size of a large beatle.

Capt'n Midnight

I like trilobites , I keep imagining them to be like horseshoe crabs

90 cm that's bigger than these guys http://en.wikipedia.org/wiki/Giant_isopod (no relation)

but still much smaller than Arthropleura

Scarinae

I'm a bit puzzled by where they got the 90cm figure from, the actual paper says 70cm. Still bloody massive though.

The photograph in the original post isn't actually the biggest of the specimens found - the caption of that photo in the paper says 'partially enrolled specimen 32cm wide' (the scale bar is 10cm)

Here is the 70cm specimen, I took it directly from the paper

Scarinae

Oh, and just in case anyone wants to actually look up the primary source for the story, the paper is called 'Giant trilobites and trilobite clusters from the Ordovician of Portugal' by Gutiérrez-Marco et. al in the May 2009 edition of the journal Geology.

Here is the abstract:

Large quarrying surfaces of roofing slate in the Arouca Geopark (northern Portugal), formed under oxygen-depleted conditions, have yielded a unique Ordovician fossil lagerstätte that reveals new information on the social behavior of trilobites. It provides several of the world’s largest trilobite specimens (some reaching 70 cm), showing evidence of possible polar gigantism in six different species, as well as numerous examples of monotaxic and polytaxic size-segregated autochthonous trilobite clusters, some of which contain as many as 1000 specimens. These reveal a very diverse social behavior, which includes temporary refuge from predation and synchronous molting and reproduction, demonstrated for the first time in five contemporary families of three different trilobite orders from a single formation.

Scarinae

Sorry to be completely hogging this thread today, but I just read the paper again and have figured out where the 90cm figure came from. They found that 70cm-long, nearly complete fossil of Ogyginus forteyi that is shown in the photograph in my above post; however, they also found a 21cm isolated pygidium (the lower, or posterior, body part) of Hungioides bohemicus which suggests a total length of 90cm. Hope that clears it up for everyone!