Description: The jaws of Brachyrhizodus and other rays are comprised of interconnected flat crusher teeth that are arranged
into a tooth battery. Like sharks teeth, they are highly resistant to stream wear. The central pavement teeth possess an
elongated, hexagonal outline as viewed from the top. The enamel covered crushing surface is about 2 cm (about .75 in) long,
while both the total tooth height and width are about .5 cm (about .1 in) each. The roots of the central teeth are often divided
into three or more lobes. The lateral teeth are similar except that their length and width are about the same and their roots are
only divided into two lobes. The top of the enamel of all teeth is slightly domed when viewed from the side.
The vertebral centra of batoids (rays and skates) are somewhat similar to shark vertebrae (amphacoelous) but are oval to
crescent shaped in outline as viewed in from the anterior or posterior faces. The sides of the vertebral centra are solid with no
openings. They are also generally more robust and larger than shark vertebrae. A usual sized vertebra is about 2.5 to 3 cm
(about 1 in) long, about 2 cm (about .75 in) wide and about 1.5 cm (About .5 in) high. Sometimes cartilage is found adhering to
the dorsal side of the vertebrae forming four shallow pits where the transverse processes and the muscles where attached. Due
to their isolated nature, it is uncertain which batted these vertebrae came from, but most sources label them as cf.
Brachyrhizodus wichitaensis. They could also be from Rhombodus or some other batoid.
The dermal scutes attributable to Brachyrhizodus are oval in outline and have a slight peak in the center. They can be
distinguished from the scutes attributable to Rhombodus by the ornamentation of small bumps surrounding the apex. These
scutes are delicate and most probably do not survive because of stream wear, so finding one intact is uncommon.
Rhombodus laevis, another cow nosed ray, is represented at Big Brook by its rather distinctive pavement teeth and scutes. The
teeth of this ray are blocky and have diamond shaped cross section. The crushing surface is smooth, flat and enamel coated.
The sides of the tooth are smooth with no striations. The root comprises about one third of the 5 to 6 mm (about .25 in) height
and the tooth width and length are about 4 mm (about .12 in) each. The roots are usually divided into two. These teeth are hard
to recover from the stream because they fall through most Â¼ in screens. This probably makes them appear less common than
they really are. A small mesh screen should be used to recover these teeth. They are more common in certain layers in situ.
Scutes attributable to Rhombodus are oval to tear drop shaped in outline and have a high peak in the middle. The ornamentation
consists of small radiating small grooves starting at the apex and running down to the margin of the scute.
Commonality: The most common ray fossils found at Big Brook are the teeth of Brachyrhizodus. The scutes of this ray are
very uncommon. Rhombodus teeth are uncommon partly because of their small size but are fairly common in certain layers of the
Mt. Laurel. The scutes are less common. The batoid vertebrae are somewhat common.
Similar fossils: The pavement teeth of Brachyrhizodus are distinguishable from Rhombodus teeth in that they are more
hexagonal in outline than the more diamond shaped outline of Rhombodus. Brachyrhizodus teeth are also larger. The scutes of
Brachyrhizodus can be distinguished form Rhombodus by the ornamentation of small bumps surrounding the apex. Batoid
vertebrae have a more crescent shape than the circular outline of shark vertebra.
Size: Both probably did not get very large with Brachyrhizodus from 1 to 1.5 meters (about 3 to 5 feet) long and Rhombodus
at about .75 to 1 meter (about 2.5 to 3 feet) long.
Notes: These early rays might have lived much like modern ones do today. If this is true, then they lived on the bottom of the
sea using their crusher teeth to extract the edible parts of the animals that they fed on, which included crustaceans, small bivalves,
sea urchins and other tidbits it found on the sea floor. Unlike modern sting rays, they would seem to of lacked a barbed stinger,
since there have been none found in the fossil record at this locality. Close relatives of the rays were widespread worldwide
during the Cretaceous and its close cousins are still alive today.
|Cow Nosed Rays
Brachyrhizodus wichitaensis Roemer
Rhombodus laevis Cappetta & Case
|Brachyrhizodus wichitaensis Roemer
|Central Crusher Tooth
a. Top b. Basal (root)
|Medial & End crusher tooth
a. lingual (side) b. occlusal
cf. B. wichitaensis Roemer
a. Specimen b. Drawing
cf. R. laevis Cappetta & Case
a. Specimen b. Drawing top view c. Drawing side view
a. Specimen b. Drawing
a. lingual b. basal (root)
|Rhombodus laevis Cappetta & Case
|Central Crusher Tooth
a. Top b. Side c. Root
|The root can have one or more
groves, depending on where the tooth
is in the jaw.
a. lingual b. basal (root) c. Top