Message #237032

[In the Mouth of Madness]

-- At the existing degree of decomposition, a plesiosaur would probably have retained its upper jaws and teeth (Hasegawa and Uyeno 1978, p 63), but no teeth were reported in the specimen carcass (Obata and Tomoda 1978, p 48). A basking shark, however, is known to easily loose both jaws, and even if it retained the upper jaw, its extremely tiny teeth could be more easily overlooked.

-- The carcass length was reported as 10 meters (33 feet). Basking sharks commonly grow to 30 feet more (Dingerkus 1985; Freedman 1985), and specimens over 40 feet long have been reported (Heuvelmans 1968; Herald 1975; Soule 1981; Steel 1985). Some authors indicate they may even grow to 50 or more feet (Springer and Gold 1989; Perrine 1995; Allen 1996) The carcass size would also be compatible with a small plesiosaur, but the body proportions are not (explained below).

-- Although some of Yano's measurements seem surprisingly round (for example, 2000 mm for the tail and 10000 mm total length), if we assume they are reasonably accurate, then the body proportions (approximately 2:6:2 for the head+neck:torso:tail) are incompatible with any known plesiosaur fossils (Obata and Tomoda 1978, p 52). In many plesiosaurs the neck is by the longest section, and in no case is the torso (between the pelvic and pectoral fins) much longer than the head and neck, as it is in the carcass. The carcass could have lost some length through tail loss (discussed below), but the neck to torso ratio would still be incompatible with plesiosaurs.

-- The carcass body proportions are largely compatible with a large basking shark carcass, especially one that lost its tail (compare Figures 5 and 2). Loss of the tail would be likely, since the wide tail would tend to snap at the narrow juncture during decay and buffeting in the water. This would explain the blunt rather than tapering tail end in Yano's sketch. The rostrum (nose tip) may also have been lost, but would not appreciably affect the overall body length or proportions. Adding a tail would mean the shark was closer to 12.5 meters (41 feet) in life, which would be exceptionally large, but still within the generally accepted size range of basking sharks. After all, this poor basker may have died of old age.

The combined anatomical evidence thus strongly indicates a shark and and effectively rules out a plesiosaur. Obata and Tomoda (1978, p 52) conclude, "there are no known fossil reptilian species that agree with the animal under consideration." Likewise, Hasegawa and Uyeno (1978, p 64) write, "From the osteological point of view, we conclude that this creature does not belong to the plesiosaurian reptiles."