WHOSE TOOTH IS THIS?

Artiodactyla

By David Thulman

In the Pleistocene of Florida, the order Artiodactyla included the families Tayassuidae (peccaries), Camelidae (llamas), Cervidae (deer), and Bovidae (bison). In addition to discussing the teeth of these families, this installment of Whose Tooth is This? also includes Antilocapridae (pronghorn antelopes) which were only present in Florida in the Miocene and Pliocene.

Artiodactyl means "even numbered toes," and although they may share a family propensity for toes in multiples of two, their teeth can be very dissimilar. The deer, llamas, bison and antelopes are called selenodonts, meaning the cusps of their premolars and molars have coalesced into crescent-shaped crests, while their cousins the peccaries and pigs have cheek teeth with more or less rounded cusps and canines large enough to be called tusks.

I've relied on the Checklist of the Fossil Vertebrates of Florida, Hulbert, R.C. 1992, Papers in Florida Paleontology, 6:1-35.

Tayassuidae (peccaries)

Two peccary genera roamed and rooted around Florida in the Pleistocene: Mylohyus and Platygonus. Mylohyus had rounded, lower crowned (bunodont) teeth (Figure 1)

compared to the angular, higher crowned teeth of Platygonus (Figure 2).

The teeth of Playtgonus can also be described as bilophodont, which means the cusps form two parallel ridges. The unworn molars of Platygonus look like miniature mastodon molars in profile. This difference in crown profile make the genera easy to distinguish in unworn specimens. However, once worn this distinction is lost and differentiating the genera is problematic. The premolars of Mylohyus have four cusps while the premolars of Platygonus have three.

Figure 3

is an upper (arrow) and lower canine of Platygonus.

There are not striking size differences between the genera and the dimensions vary between these samples by a few millimeters. This observation is borne out by the samples reported in Tayassuidae of the Irvingtonian Leisey Shell Pit Local Fauna, Hillsborough County, Florida, Wright, D.G., Bull. Fla. Museum of Nat. Hist., 37 Pt.II,(18):603-619 (1995). This article has some very good photographs of both Mylohyus and Platygonus.

The teeth of a modern pig (Sus) are bunodont and generally smaller than Mylohyus, however, modern pigs come in all sizes as does their dentition. In addition, the premolars do not have four cusps.

Antilocapridae (pronghorn antelopes)

These small selenodonts (Capromeryx arizonensis) capered about at the end of the Pliocene. Their teeth are remarkably small. Figure 4

shows individual molars and premolars. For comparision, a dime has a diameter of 18mm, while the largest molar in Figure 4 is 17mm wide.

Cervidae (deer)

The white tail deer (Odocoileus virginianus) is a common find in the rivers I dive. It apparently was not as ubiquitous at the end of the Pleistocene as it is today, and undoubtedly most of the jaws, teeth and antlers that turn up in my screen are from Holocene hunting seasons. Figure 5

depicts maxillary dentition.

Figure 6

depicts mandibular dentition of a specimen from Devil's Den. Since the occlusal surface is slanted, the crown height varies up to 3 mm on the lingual and buccal sides.

Camelidae (llamas)

Just as with Tayassuidae, two genera of Camelidae grazed and browsed across Pleistocene Florida. Hemiauchenia macrocephala, a mixed browser and grazer, was larger than Palaeolama mirifica, a browser. There is a good discussion and discrimination between Hemiauchenia and Palaeolama in Selenodont Artiodactlya (Camelidae and Cervidae) from the Leisey Shell Pits, Hillsborough County, Florida. Webb, S.D. and Stehli, F.G. Bull. Fla. Museum of Nat. Hist., 37 Pt.II,(18):621-643 (1995).

The teeth are not easily distinguished by size. Figure 7

is a maxilla of Hemiauchenia. In comparing these species it seemed to me that Hemiauchenia is generally more robust, but exactly why is difficult to articulate. In any event, this is only apparent in comparison of a number of known specimens.

Figure 8

is a mandible of a female Palaeolama.

Figure 9

is a mandibular symphysis from Palaeolama.

Hemiauchenia has a caniniform (canine-like) first premolar. Distinguishing between these species on the basis of crown pattern can be problematic since the crown pattern can change dramatically as the animal ages. Figure 10

shows molars from two Palaeolamas. The upper teeth (left m1 and m2) are hardly worn, while the lower teeth (right m2 and m3) are very worn. They look dramatically different. The differences are even more apparent by comparing the profiles of these teeth in Figure 11.

Relatively unworn cheek teeth can be distinguished because the crown height in Hemiauchenia is higher than in Palaeolama, but once the teeth are worn, the distinction is lost. On the teeth I measured from Leisey, none of the crowns from Palaeolama cheek teeth exceeded 24mm, so this may be another way to distinguish the species.

Figure 12

depicts five canines. The first and third from the left are identified as Palaeolama. The rest are identified as Camelidae.

A much better way to distinguish these teeth is by the presence of cementum on their surfaces. Webb and Stehli point out that Hemiauchenia had a heavy external coating of cementum over the entire tooth while Palaeolama did not. Figure 13

depicts from left to right, right upper molars from Hemiauchenia and Palaeolama. The cementum is visible on the tooth on the right as black, crenulated interlacing.

Bovidae (Bison)

Two Bison species inhabited Florida during the Pleistocene. Bison latifrons is found in the middle Pleistocene and Bison antiquus is found in the late Pleistocene. These species are distinguished by horn size and are indistinguishable on the basis of their dentition.

Figure 14

is maxillary dentition from Bison antiquus.

Figure 15

is a mandible from Bison latifrons.

Modern cows apparently are very clumsy and frequently trip and fall into rivers and drown and so their bones and teeth are fairly common finds. The lower teeth of a modern cow (Bos taurus) are close to the same size as the teeth from a jaw of a small Bison antiquus. However, the jaw of Bison antiquus itself is significantly larger than Bos. Apparently there is great size variation between individuals in Bovidae.

Vital Statistics

All figures are listed left to right and measured in millimeters, Length of crown x labial-lingual Width of crown x Height of crown. M = molar, p = premolar, c = canine, and i = incisor. The numbers after letters refer to number of the particular tooth. For example, m3 is the third molar. The (UFxxx) refers to the University of Florida vertebrate paleontology collection number for the particular specimen.