Scientific Name: Rhinobatos casieri

Specimen location: Niobrara Chalk of Northwestern Kansas

Fossil sharks like Rhinobatos are known primarily by their teeth, as their cartilage skeletons typically decayed soon after death, before fossilization could occur. Scientists have found two types of ancient guitarfish teeth which probably represent differences between the male and female; similar differences are found in modern guitarfish.

Scanning electron micrograph (187.5x)

LACM 131958 (6074)
Discoverer: Marion Bonner

"What Lovely Teeth You Have"

These Pachyrhizodus skeletons were all cast from the same original fossil. That specimen had irregular teeth, probably a result of disease or infection. This Pachyrhizodus is much smaller than average, possibly due to diffuculties it had with hunting and eating caused by its bad teeth.

PACHYRHIZODUS minimus

(PAK ee rize OH dus)

Description: Ray-finned Fish

Specimen location: Niobrara Chalk of Northwestern Kansas

The teeth of Pachyrhizodus suggest they were predators. Although the fossilized digestive tract can be seen in this specimen, it is not enough evidence to tell us what exactly this fish ate.

LACM 148055(7309)
Discoverer: Chuck Bonner