|Early Drum Fish
Anornaeodus phaseolus (Hay)
|Description: The pycnodont fish, Anomaeodus phaseolus, is represented at Big Brook by its isolated crusher and branchial teeth, jaw plates and possibly an occasional vertebre.
The most common find of this unusual and interesting fish is that of its isolated crusher teeth. Like modern drum fish, their teeth easily separate from the jaw while new ones grow in to take their place. These teeth are typically 5 mm to 2.5 cm (about .25 to 1 in) long and 5 to 9 mm (about .25 to .31 in) wide. Further, they are smooth, enamel coated with one side usually worn due to what the fish was eating during life. The medial teeth have an elongated oval outline, with the top rounded and the bottom of the tooth displaying a hollowed out cavity, looking somewhat similar to half of a peanut shell. The lateral teeth are similar to the medial teeth except they are round to slightly oval in outline. The vomerine teeth are very similar to the lateral teeth and it is hard to differentiate between the two, except when present in the jaws.
Their protruding mouths consisted of an upper and a lower battery of flat crushing teeth. The medial teeth were centrally located in the jaw with the lateral teeth beside them. The upper and lower jaw plates are similar to each other and are hard to segregate between them. The vomerine jaw is also a flat plate of bone supporting a battery of round to oval vomerine teeth.
The oral teeth of Anomaeodus are small hooked and partially translucent. These teeth are unusual and distinctive and two types can usually be recovered. The pharyngeal teeth are generally the most common and the larger of the two ranging up to 1 cm (about .4 in) in height and 5 mm (about .25 in) in width. When viewed from the side, the teeth are flat and only 1.5 mm (about .06 in) thick. The smooth enamel coated blades are somewhat translucent and make up about one half of the total vertical height. These teeth are strongly curved to the back of the jaws and look something like the claws of a cat. The roots, which are often worn off, are thin and display a trapezoidal shape. The premaxillary teeth are somewhat similar to the pharygeal teeth but are more asymmetrical, incisor-like, and lacking a strong hook.
Vertebrae of this pycnodont fish may also occur. They are presumably laterally compressed and have the neural processes fused to the centrum. The anterior and posterior faces are not deeply concaved and when viewed from the front or the back, the vertical measurement is larger than the horizontal. These vertebrae are typically 1.5 cm (about .5 in) long and 1 cm (about .5 in) wide. Although it is unsure which species these vertebrae came from, they are probably from a deep-bodied fish and probability would loosely place the pycnodont as the source.
Commonality: The isolated teeth from this fish are fairly common while the teeth articulated in the jaws and identifiable vertebrae are very uncommon.
Similar fossils: The teeth somewhat resemble some of the stream gravel but these lack the hollowed out cavity in the bottom of the tooth.
Size: Since they possessed narrow and deep bodies, the length was about the same as its height, about .5 to 1 meters (about 1.5 to 3 feet) long.
Notes: The diverse order of pycnodonts with their deep, narrow bodies along with elongated dorsal and anal fins suggest that these fish inhabited calm waters. Their flat crusher teeth indicate that it feed on mollusks, crustaceans, and sea urchins. It would appear that this pycnodont fish went extinct at the end of the Cretaceous and the entire order went extinct during the Eocene.
|Vomerine crusher tooth|
|Isolated cursher teeth w/
different wear facets
|Two crusher teeth
in part of Jaw
|Reconstructed jaw w/ the vomerine
teeth on the sides
a. Picture b. Drawing