BULLETIN FLORIDA STATE MUSEUM


type locality and from Florida are of generally similar size (compare
Tables 1-4).
 POSTCRANIAL SKELETON.-The following postcranial elements are
represented in the Florida specimens of Nannippus phlegon (for in-
dividual numbers see Referred Material above): right humerus, left
radius, left ulna, right magnum, ?left magnum, left medial (III)
metacarpal, left lateral (II) metacarpal, right and left lateral (IV)
metacarpals, femur, astragalus, navicular, right medial (III) metatar-
sal, left medial (III) metatarsal, medial (III) metapodials, lateral (II or
IV) metapodials, first medial (III) phalanx, and second medial (III)
phalanx. These postcranial elements are assigned to N. phlegon with
some certainty because: (1) they are very much smaller than those
associated with Equus (Dolichohippus = Plesippus)1 in the same
deposits; and (2) of their similarity to articulated N. phlegon material
(in the AMNH) from Crawfish Draw, Mt. Blanco.
 UF 22645 is a distal fragment of a right humerus. On the dorsal
side the olecranon fossa is preserved. On the volar side the coronoid
fossa is preserved. The medial epicondyle is smaller than the lateral
epicondyle. On the distal trochlea the medial condyle is smaller than
the lateral condyle, and these are separated by a well-developed
parasagittal ridge.
 The left radius and ulna are represented by two specimens, UF
7260 and UF 7263 (Fig. 8, Table 5). The proximal articular surface of
the radius is divided into two facets for articulation with the medial
and lateral condyles of the humerus. Approximately midway down the
shaft the cross-section of the radius is roughly oval, although the volar
surface is slightly concave. The distal articular surface of the radius
consists of facets for the proximal row of carpal bones, i.e. scaphoid
(this term is preferred to navicular, which is restricted here to the bone
in the tarsus) and lunatum. The proximal shaft of the ulna is broken so
that the olecranon process is not preserved. The proximal portion of
the shaft that is preserved is separated (unfused) from the radius by
the interosseous space. The remainder of the ulna, i.e. medially and
distally, is fused to the radius. The distal articular surface of the ulna
has facets for the triquetrum and pisiform.
 The right and possibly left magna are represented by UF 21325 and
UF 22644. Both specimens are somewhat waterworn, but several im-
portant features are preserved. The magnum of N. phlegon is relative-
ly wider than in some more primitive horses. The medial facet for the
scaphoid is concave and somewhat larger than the lateral facet for the
lunatum. The posterior keel is not preserved in these specimens. The
'Following the synomy of Skinner and Hibbard (1972), the subgenus Equus (Dolichohippus) is used here in place of E.
(Plesippus).


Vol. 25, No. 1