Echinochimaera meltoni
Echinochimaera meltoni female
Echinochimaera meltoni is a holocephalan closely related both to the modern chimaeroids and to the contemporaneous cochliodonts (shell-toothed fish). Males range up to to 8 inches in length; females only grew to half the size of males. They were common and ubiquitous throughout the bay at all sizes.
They had rounded bodies, large pectoral fins, and two dorsal fins, the first with a spine that was movable. The body and fin forms and paddle-shaped tails indicate a slow maneuverer, not a predator and certainly not a fast swimmer. They had a complete covering of pointed placoid scales over the head and body. There were pairs of enlarged multicuspid scales between the second dorsal fin and the tail, and paired spikes projecting backward from the occipital region. The fins were very flexible; and probably translucent to transparent as in modern chimaeras. Fin radials are stiffened by scales but are well spaced, evidently with thin membrane between the radials.
Male Eichinochimaera meltoni
Mature males were much larger than females, and quite different in appearance. They bore 4 pairs of antler-like spikes over the eyes, had a taller and more elaborate first dorsal fin and spine, and had prepelvic claspers somewhat like those of modern chimaeroids. Female bodies were more rounded. Color pattern is unknown but was probably prominent, and particularly in the large, ornately shaped males. Considerable behavior can be inferred from this type of visually displayed sex dimorphism, and the body and tail form. The spikes and spines might also have protected against some predators as well as served to identify both the species and the sexual status of the individual.
The jaws were armed with evergrowing cutting-crushing dental plates rather than teeth, for eating harder foods. There were two pairs of plates in the upper jaws and one pair in the lower jaws. Upper jaws were fused to the braincase.
Reference:
- Lund, R. 1977. "Echinochimaera meltoni new genus and species (Chimaeriformes) from the Mississippian of Montana." Ann. Carnegie Mus. 46: 195-221.