Protocallinassa mortoni (Pilsbry)
|Description: This shrimp is represented only by the claws, parts of arms and their filled in burrows at Big Brook. There are two different types of claws that this shrimp possessed. The defense claw is robust and has a roughly rectangular outline. Both the pincers on the defense claw are also robust and curved. The feeder claw is not as robust and has more of a rounded rectangular outline. The pincers are long, thin and where used as forceps, like their modern counterparts. Both claws with pincers (not including the rest of the arm) are about 2.5 cm (about 1 in) long. Most of the shrimp material is jet-black or brown in color.
Their filled in (cast) burrows are also found. They are usually long and tube-like with many random bumps. These may also branch into other side burrows. The burrows are in about 10 to 15 cm (about 4 to 6 in) long sections and about 1.5 cm (about .75 in) in diameter.
Commonality: The claws without the pincers are very common and less common with the pincers. Complete claw sets are very uncommon and even when found are very delicate and do not survive the stream wear. Their burrows are common in situ in the Mt. Laurel.
Similar fossils: The claws are very similar to the claws of the lobster (not covered) and it is difficult at best to tell the difference. The best way to tell the difference is by their commonality and the blocky nature of the claws. A more thorough reference is recommended.
Size: Judging from the size of the burrows and claws, the size of the shrimp would have been about 15 cm (about 6 in) long.
Notes: It is interesting that the claws and arms of this ghost shrimp were the only parts that where robust enough to fossilize. The body shape is unknown. These shrimp probably feed on carrion on the sea floor.
|Feeder and Protector Claws|