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Information about Squalodon calvertensis (Kellogg, 1923), the long-snouted shark toothed whale
By Jayson Kowinsky
This is my rendition of a squalodon. Notice the large pectoral fins, reduced dorsal fin, mobile neck, the long beak, and the front teeth protruding from the jaw, creating small "tusks."
The body shape is based on an Irrawaddy Dolphin (Orcaella brevirostris), due to its large pectoral fins, mobile neck, and reduced dorsal fin. The head is based on many squalodon skulls, the body pattern is similar to a Rough-Toothed Dolphin (Steno bredanensis), because I think it looks cool!
Squalodons lived from the early-middle Oligocene into the middle Miocene, roughly 33 to 14 million years ago. The squalodon genus belongs to the Odontocete Order, the toothed whales. Specifically it belongs to the Squalodontidae superfamily. This superfamily is named after the shark squallus, since its' cheek teeth superficially resemble the teeth of a squallus shark; hence the name "shark toothed whale". The Squalodontidae superfamily contains three different groups of medium-sized (roughly 3 meters in length) shark toothed whales. They are the short-snouted shark toothed whales (prososqualodon), the medium-snouted shark toothed whales (phoberodon), and the long-snouted shark toothed whales. This last group contains the genus squalodon.
A strange mix of archaic and modern features characterizes this interesting superfamily. One of the most noticeable archaic features is their complex dentition. While other toothed whales were evolving simple conical teeth at this time, Squalodontidae retained their primitive teeth that their ancestors (the archaeocetis) had. For example their dentition is complex, their teeth are widely spaced apart, and their cheek teeth are triangular and serrated for grasping and cutting. An illustration of this similar archaeoceti dentition can be seen in figure 1.
Here is my illustration of a squalodon skull compared to an archaeoceti's skull. The archaeoceti illustrated here is an Eocene zygorhiza, which was actually much larger than a squalodon. Notice how similar the molars are.
An actual skull (minus the mandibles) of a squalodon can be seen on public display at the Smithsonian Museum of Natural History in Washington, DC. Below is a picture of their skull on public display. The rear of the skull has been partially restored. Also, the front of the maxilla has also been restored. However, it has been incorrectly restored, as the front "fangs" that stick straight out of the maxilla are not present.
Another archaic quality the Squalodontidae possess is their necks. The necks are more compressed than archaeoceti; however they were probably more mobile than the other "modern looking" toothed whales at the time. Finally, paleontologists believe the dorsal fins were larger than archaeocetis, but still somewhat reduced.
Despite these ancient features on Squalodontidae, they also had a mix of modern characteristics. For example, their craniums were well compressed, as their rostrums were telescoped outward, giving the appearance of modern toothed whales. Finally, squalodon skulls show evidence for the first appearance of echolocation. An illustration of a skull can be seen in figure 2.
This illustration shows a comparison of three skulls, zygorhiza, squalodon, and phoca (a modern porpoise). Notice how the squalodon has it's nasal passages upward toward the cranium, instead of on the rostrum as the zygorhiza has (the nasal passages are shaded in black, the zygorhiza has one large one on its snout, whereas the other skulls have two small ones further back.) This is remarkably similar to the nasal passage placement on modern dolphins, thus showing modern characteristics. Also notice how asymmetric modern dolphin skulls are (the asymmmetry aids in echolocation). In reality, the eocene zyghoriza is much larger than a squalodon and dolphin.
These strange looking creatures could be found throughout the world in the Oligocene and Miocene. However, they became extinct in the middle of the Miocene and left no descendants. Now, occasionally one can find an isolated tooth or bone from one of these great beasts while beach combing along the shores below the Calvert Cliffs of Maryland. In these cliffs, the remains of two species of squalodon can be found (although rarely). The first is a somewhat larger, unnamed squalodon species. The second is squalodon calvertensis. The recently discovered specimen is a S. calvertensis from Zone 11 of the Calvert Formation, which creates part of those famous cliffs in Maryland.
Carrol, R. (1988). Vertebrate Paleontology and Evolution. NY: W.H. Freeman & Company.
Mchedlidze G.A.; Translated by Chakravarthy, R. (1984). General Features of the Paleobiological Evolution of Cetacea. New Delhi: Oxonian Press. Translated for Smithsonian Institution Libraries.
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