by Ida L. Thompson, Geology Department 



cuttlefTs 





This month's cover shows Geoteuthis, t 

 years ago. The original was drawn in i 

 reproduced it here in a sepia to give y( 

 is on display in Stanley Field Hall durir 

 Here is the story of Geoteuthis and its I 

 in the age of the great dinosaurs, whe' r 

 predators in warm shallow seas that c ' 



l^/CT SUN and other stars have been photographed by 

 their own light; many animals leave tracks on their trail. 

 Why not, we of the Geology Department thought, a picture 

 of a Jurassic cuttlefish drawn in its own 170 million-year- 

 old brown ink? 



The Museum's Geology Department had a specimen of 

 the well-known fossil cuttlefish, Geoteuthis, from the Jurassic 

 Period 1 70 million years ago. This cuttlefish was preserved 

 with its inksac intact. We also had a squid-like fossil from 

 the Pennsylvanian Period, about 100 million years earlier. 

 This squid-like fossil had a small amount of black material 

 adhering to it in approximately the position the inksac 

 should have been. Several members of the Geology De- 

 partment were curious to know if this dark substance was 

 the fossilized remnant of an inksac. Our plan was to dis- 

 solve some of the known cuttlefish ink, then see if the same 

 solvent would dissolve the black material on the squid. This 

 would have given us circumstantial evidence that the squid 

 fossil also contained ink. "Project Cuttlefish"' informally 

 established itself to carry out this experiment. 



The ink of the cuttlefish, Geoteuthis, was preserved in a 

 glassy solid that was soft enough to be cut away with a knife. 

 The next step was to immerse some flakes of the inky-looking 

 substance in the "universal solvent," water. Failure! Next, 

 we tried the other standard solvents : xylene, acetone, alco- 

 hol, hydrochloric acid and ammonia, .\gain failure. A bit 

 of research on the chemistry and preparation of cuttlefish ink 

 produced the needed information. Fresh cuttlefish pigment 

 is melanin, the same brownish substance that comes to the 

 surface of your skin when you tan in the sun. Melanin does 

 not dissolve to produce ink; rather it must be prepared in a 

 suspension, tiny particles in an alkaline solution. 



At this point we realized that "Project Cuttlefish" was 

 going to fail in its original goal. There just was not enough 

 black material on the squid fossil to try to make a suspen- 

 sion. But there was plenty of the cuttlefish fossil ink, so the 

 project continued out of curiosity to discover what could be 

 done with this ink. 



We applied mortar, pestle and elbow grease to the fossil 

 ink flakes, then mixed the resultant powder with ammonia. 

 We were startled to discover a deep brown mixture that 

 looked like artists' sepia pigment. It even flowed like ink 

 in a quill crow pen. 



Could it be used? We consulted Mr. Lido Lucchesi, an 

 artist with the Harris Extension of the Museum. He con- 

 firmed that it was not only sepia ink, but so fine in quality 

 that he agreed to immortalize the ancient cuttlefish, Geo- 

 teuthis, by drawing it in its own ink, 170 million years old. 

 The drawing, shown on the cover, was based on a recon- 

 struction of the Jurassic Age cuttlefish made by Naef, a 

 German fossil-cephalopod expert, and on the Museum's 

 photographs and drawings of extant cuttlefish. 



W"hile Mr. Lucchesi worked on the drawing, "Project 

 Cuttlefish" continued its research. Geoteuthis is a mollusk 

 of the class Cephalopoda, which also includes nautiloids, 

 squids and octopuses. Cuttlefish are easy to confuse with 

 squids, since both have similar body shapes, eight arms and 

 two long tentacles. The shell of the cuttlefish, though, is 

 oval and broad, while the squid's is long and narrow. The 

 shells of both animals are internal, although homologous to 

 the navitilus' external shell. 



The present cuttlefish evolved from an earlier cephalo- 

 pod with an external shell, perhaps similar to the straight- 

 shelled ammonites commonly found fossilized in Paleozoic 

 rocks. In the course of evolution the cuttlefish shell was 

 reduced in size and eventually enclosed within the mantle, 

 gaining the animal two important advantages, speed and 

 maneuverability. However, the price of increased swim- 

 ming capability was the loss of protection for many of the 

 animal's soft parts. To compensate for this vulnerability, 

 somewhere along the evolutionary line cuttlefish ancestors 

 developed an inksac. 



When a cuttlefish is alarmed, it shoots out a jet of ink as 

 a decoy. After discharging the ink, the cuttlefish changes its 

 color from sepia-brown to pale beige, almost white. The 

 brown ink in the water looks like a cuttlefish to witless pred- 



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