SMgender

Steve Cunningham, Baltimore, Maryland, USA
Striatolamia macrota Agassiz, 1843
Two possible subsets

From Mike Folmer's collection, Fisher/Sullivan site, early Eocene (Ypresian stage) Potapaco Member of the Nanjemoy Formation. A Random sample of 9,250 S. macrota teeth were sorted to position and then separated into two subsets labeled "a" and "b" as shown below.

Photos by S. Cunningham. Teeth have been coated with sublimated ammonium chloride to enhance detail.
The teeth of each position are depicted by three views of the same tooth. In the photographs below, all teeth are representative of the positional files of teeth from which they came.

All positional characters are derived from, and comparable to, extracted C. taurus teeth.

Distinguishing characters that define each subset are consistent from anterior to posterior teeth and throughout ontogeny. The 8 files for each lateral subset shown below are arbitrary. It is not know how many files S. Macrota had. However, the teeth depicted below represent the array of positional changes in the study set.

In the study set of 9,250 teeth, subset "a" totaled 5,665 teeth; while subset "b" totaled 3,298. The total count of first upper anterior teeth is 287 suggesting that only one subset has this position. The UA1 is consistent in characters and cannot be differentiated into subsets.

Click here to see the positional tooth count and graph of positions for each subset

General differences
Subset a	Subset b
Courser striations	Not as coursely striated or smooth
"U" shaped root interspace in lateral teeth	"V" shaped root interspace on lateral teeth
Moderate protuberance	Stronger protuberance
Profile view of labial side of laterals is nearly flat or convex	Profile view of labial side of laterals is flat or obtuse angle of root and blade in lateral teeth
Crown rarely waisted (anterior teeth)	Crown more often waisted (anterior teeth)
Bulky crown and root appearance	Slender crown and root appearance
Lateral teeth bear distinct lateral cusplets	Lateral teeth bear shoulder-like lateral cusplets
Mesial lateral cusplet reduces in size to the posterior	Mesial lateral cusplet does not reduce in size
Root generally exhibits fine pits	Root is generally smooth

Click on a tooth, group or row of teeth to see the larger image.
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Typical striations

Strong striations

Weak striations or smooth

Clear here to compare both typical striations

Typical upper lateral characters
a	b
Striations well defined Root generally pitted Lateral cusplets well defined "U" shaped lobe interspace	Striations are weak or not present Root generally smooth or less pitted Lateral cusplets less defined "V" shaped lobe interspace

Click Here to compare both upper lateral examples

Typical lower lateral characters
a	b
Striations are generally course Root generally pitted Lateral cusplets well defined "U" shaped lobe interspace	Striations are weak or not present Root generally smooth or less pitted Lateral cusplets shoulder-like "V" shaped lobe interspace

Click here to compare both lower lateral examples

UA1

The UA1 is consistent in appearance and cannot be reliably assigned to either subset. Their numbers total 287 out of 9,250 suggesting the position belonged to only one subset. The Characters and graph ally it with subset "b."