|Fig. 1 (left): Laterally-placed rostral teeth of a juvenile green sawfish (Pristis zijsron). Fig. 2 (right): Fossil rostral teeth and a portion of fossilized rostrum from the extinct sawfish genus Propristis, late Eocene.|
The modern sawfish group first showed up in the fossil record between the beginning of the Cenozoic (about 66 million years ago) and the beginning of the Eocene (about 56 million years ago). The only extinct genus (Propristis) had interesting broad flat teeth that were closely spaced along the rostrum (Fig. 2).
|Fig. 3: The anterior portion of a fossil rostrum and associated spines of the Cretaceous sawfish, Onchopristis numidus, Cenomanian.|
|Fig. 4 (left): Close-up of a rostrum of a saw shark (Pristiophorus sp.) showing the ventrally-placed spines. Fig 5 (right): Close-up of a rostrum of a saw shark (Pristiophorus sp.) showing the laterally-placed spines.|
The long, tooth-studded snouts of Cretaceous sawfishes, modern sawfishes, and saw sharks evolved separately and independently. Cretaceous sawfishes and modern sawfishes evolved independently from either the guitarfishes (Rhinobatidae; as suggested by some authors) or the wedgefishes (Rhynchobatidae; Fig. 6). Members of both groups have characteristics that they share with the modern sawfishes.
|Fig. 6: The dried head and rostrum of the whitespotted guitarfish (Rhynchobatus australiae). Note the superficial resemblance to that of modern sawfishes.|
In Part 2 of this series we’ll discuss paddlefish paddles, billfish bills, and swordfish….. Well, you get the idea! More anatomical oddities discussed and explained ahead so stay tuned!