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Longest Nautiloid Found
Not quite dino related...
FAYETTEVILLE, Ark. -- Three undergraduate students from the University of
Arkansas made a world-class discovery this week when they uncovered a
325-million-year-old nautiloid fossil just yards from two of
Fayetteville's busiest roads. At exactly eight feet in length, their find
represents the longest actinoceratoid nautiloid fossil in the world.
[geology professor Walter] Manger's initial skepticism can be understood,
considering the fact that only one other comparable nautiloid fossil is
known to exist. Not coincidentally, that specimen was also discovered in
Fayetteville in 1963 by University of Arkansas students and geology
professor Doy Zachry. Measuring seven feet, two inches, the 1963 fossil
was believed to be the largest in existence until Monday's discovery.
Belonging to the extinct species Rayonnoceras solidiforme, both fossil
specimens would have lived during the Mississippian era, when much of the
southern United States lay submerged beneath a shallow sea. A type of
cephalopod related to the modern-day squid, these organisms normally grew
no more than three to four feet in length.
The specimen uncovered by Kee, Morgan and Gillip represents what Manger
calls a pathological giant. Its discovery lends credence to a theory that
Manger first proposed to the scientific community in 1999 -- that these
nautiloids exhibited semalparous reproductive behavior. Like modern-day
squid, these creatures would have mated and laid eggs within three to four
years and then died.
Manger suggests that the giant specimens may have been rendered
reproductively sterile by parasitic trematodes. Unable to reproduce, they
could have lived for decades, diverting their energy to growth.
"The new fossil will definitely bolster that theory. When you only have
one example to go on, you wonder. But the students have given us another
example that fits perfectly with the hypothesis," Manger said.
The similarity of the two giant fossils provides evidence about the
reproductive patterns of these prehistoric creatures, but their
differences may prove even more enlightening. In modern nautiloids, males
and females show a difference in the diameter of their apertures -- the
open end of the shell, where the organisms reside. According to Manger,
the fossil giants show similar signs of sexual dimorphism.
"They're within a foot of the same length, but the aperture on the 1963
fossil is a third again as wide," Manger said. "We think we've just found
Sexing prehistoric organisms can be difficult because fossils are rarely
found whole. The specimen that Kee, Morgan and Gillip discovered is
remarkably well-preserved, offering essential information about the
creature's physical features and proportions. The tapering thickness of
the shell suggests that the fossil is complete up to the final growth
stage of the organism.
"Last semester I was an accounting major," [freshman geology major Sarah]
Kee said. "I think I made good switch."