Arecaceae Infructescence

Na, Yuling, Blanchard, Jane & Wang, Hongshan, 2019, Fruits, seeds and flowers from the Puryear clay pit (middle Eocene Cockfield Formation), western Tennessee, USA, Palaeontologia Electronica (a 49) 23 (3), pp. 1-57 : 4-5

Claiborne Arecaceae Infructescence Type 1

Figure 3

Description. Laterally preserved, pedunculate infructescences consisting of at least four tightly clustered, orbicular, sessile, fibrous fruits ca. 5–7 mm in diameter. Peduncle ca. 9.5 mm long and 1.5 mm wide. A lateral projection ca. 1.5 mm in diameter present, ca. 2 mm below the terminal cluster of fruits.

Number of specimens examined. 2. UF15820- 059399, 059399’.

Remarks. The fibrous fruits are similar to the arecaceous endocarps from the Lamkin clay pit, Graves County, Kentucky described by Grote (1989, pp. 172–176, pl. VIII; Figure 4 ), except that the fruits from the Puryear locality are smaller (5–7 mm in diameter vs 18 mm long and 14 mm wide). It is possible that these fruits represent the same species but are not fully mature. The subterminal projection may represent the base of a detached fruit or another branch of the fruiting axis.

Based upon the material from the Lamkin clay pit, Grote (1989) suggested that the characters of this fruit type, including a thin exocarp, a fibrous mesocarp, and an endocarp circular in transverse section with a tapering trigonal apex, and possible ruminate endosperm, indicate a relationship with the Arecaceae . In this report, we agree with Grote’s (1989) assignment and treat this fossil fruit type as extinct member of the Arecaceae . As suggested by Grote (1989, p. 175), a detailed examination of the extant fruits and seeds of the entire family may yield closer relatives.

This fruit type from the Puryear clay pit is also similar to Castanopsoidea cupules in size, but they differ in that the fibers of the fruits from Puryear cover the entire fruit body while the cupules of Castanopsoidea are more elongate in shape and only have short scales.

Claiborne Arecaceae Fruit Type 1

Figure 4

Description. Laterally compressed fruit with attached fibers, ca. 15 mm wide at the middle and ca. 18 mm long. Slightly concave at the base. Fibers curving around the fruit and extending from the base to beyond the apex.

Number of specimens examined. 1. UF15820- 059477, 059477’.

Remarks. This specimen probably represents a palm endocarp with mesocarp fibers. This is probably the same fruit type described by Grote (1989, pp.172–176, pl. VIII, figures 1–8) because of their similar size and the presence of fibers. Grote (1989) reported 36 charcoalized, fibrous fruits from the Lamkin clay pit, Kentucky. Based on the characters that the fruit has a thin exocarp, fibrous mesocarp, and one seed with ruminate endosperm, he suggested that these fossils may be related to the Arecaceae . However, these characters are found in various groups throughout the large family, it is difficult to relate this fruit type to a particular tribe or a genus.

Figures

FIGURE 3. Claiborne Arecaceae Infructescence Type 1: 1) UF15820-059399, showing an infructescence with at least two terminal sessile fruits and a lateral projection; 2) UF15820-059399, counterpart showing at least three fruits. All scale bars equal 3 mm.

FIGURE 4. Claiborne Arecaceae Fruit Type 1: UF15820-059477, laterally compressed fruit with fibers. Note that curved fibers (indicated by arrows) extend from the base to beyond the apex of the fruit. Scale bar equals 2 mm.