1980 MACFADDEN & WALDROP: FLORIDA NANNIPPUS PHLEGON 25

mesentocuneiform facet (medial), and one cuboid facet (lateral). These
mesentocuneiform and cuboid facets, which are as well developed as in
other advanced horses, indicate a functional de-emphasis of the lateral
(II and IV) metatarsals (Hussain 1975). Just below the proximal ar-
ticular surface, on the plantar portion of the shaft, are medial and
lateral depressions with facets for the lateral (II and IV) metartarsals.
The nutrient foramen is approximately one-quarter of the distance
down the plantar side of the shaft, which is oval in cross-section. It has
roughened areas that extend about two-thirds to three-quarters of the
distance down the plantar surface for attachments of the interosseous
lateral metatarsal ligaments. The distal portion of the medial (III)
metatarsal is very similar to the medial (III) metacarpal of N. phlegon
described above. Proximal to the distal trochlea are medial and lateral
prominences for the superficial collateral ligaments. In between these
prominences on the dorsal side is a shallow depression for the first
medial (III) phalanx. A well-developed sagittal ridge on the distal
trochlea extends approximately 2600 around the trochlea (see Table 9).
Hussain (1975) noted that the distal tuberosities (superficial collateral
ligament prominences) are wider than the distal trochlea in three-toed
horses, except in Nannippus, where he noticed the reverse. This condi-
tion in Nannippus is similar to that of one-toed horses. The
measurements for the two Florida N. phlegon specimens (.98 and 1.00,
Table 9) appear to be intermediate, i.e. the widths of both the distal
prominences and distal trochlea are approximately the same.
 Several incomplete specimens represent metapodials whose exact
position in the manus or pes cannot be determined. UF 7257, UF 7426,
and UF 7388 are fragmentary or water-worn medial (III) metapodials.
UF 22639 and UF 22640 are fragments of the medial region of the
lateral (II or IV) metapodials. Three specimens, UF 11890, 21321, and
22638 show the distal articular surface of lateral (II or IV)

TABLE 9.-MEASUREMENTS OF MEDIAL (III) METATARSALS FOR Nannippus phlegon
 FROM FLORIDA.
 UF 22630 UF 22620
 Right Left
Length* 227.2 210.7
AP length prox. surf. 24.8t 26.5
Trans. width prox. surf. 27.7 28.2
Width distal prominences 21.5 23.1
Width distal art. surf. 22.0 23.0
Ratio width dist. prom./width dist. art. surf. .98 1.00
Angle inscribed dist. art. sag. ridges 2600 2600
*Cuboid facet on proximal articular surface to distal sagittal ridge.
tMeasurement approximate.
$Probably accurate to approximately + 15.