Eucommia eocenica (Berry) Brown, 1940

Blanchard, J, Wang, H & Dilcher, D, 2016, Fruits, seeds and flowers from the Bovay and Bolden clay pits (early Eocene Tallahatta Formation, Claiborne Group), northern Mississippi, USA, Palaeontologia Electronica 19 (3), pp. 1-59 : 26

Eucommia eocenica (Berry) Brown, 1940

( Figure 22 )

v. 1930 Carpolithus banisteroides Berry , p. 134; pl. 33, figs. 5-6.

v. 1930 Simarubites eocenicus Berry , p. 94; pl. 44, figs. 15-16.

v. 1940 Eucommia eocenica (Berry) Brown ; Brown, p. 349.

v* 1997 Eucommia eocenica (Berry) Brown ; Call and Dilcher, p. 800, figs. 4-12, 16-17.

v* 1999 Eucommia eocenica (Berry) Brown ; Manchester, p. 480, fig. 3B.

Description. “Fruits are asymmetrical, stipitate, bicarpellate samaras composed of a flattened ovate nutlet surrounded by an ovate narrow wing. The fruit apex is more or less acute. Samara length (excluding stipe) ranges from 11.5 to 21 mm (average 15.1, N=13), and samara width varies from 4.5 to 8.2 mm (average 6.33, N=13). The ratio of samara length to samara width varies from about 2 to 3 (average 2.4). Stipe length ranges from 2.5 to 5.0 mm. Stipe width at the base of the fruit body is approximately 1.0 mm, tapering slightly and evenly basipetally. The stipe is attached at an angle of ~ 45°” ( Call and Dilcher, 1997, p. 801).

Number of specimens examined. 18. UF15737- 8218, 8219, 11022, 11032, 11033, 11035, 11063, 11065, 11066; UF15738-11027, 11028, 11030a, 11030’a, 52526.

Remarks. Extant Eucommia is a monotypic genus of deciduous trees native to central China ( Zhang et al., 2003). However, fossil records show a much wider distribution in the Eocene of the western and southeastern United States ( Call and Dilcher, 1997; Geng et al., 1999; Manchester, 1999, 2000, 2001; Manchester et al., 2009), northeast China ( Geng et al., 1999), and Japan ( Huzioka, 1961), the Oligocene or Miocene of southern Mexico ( Magallón-Puebla and Cevallos-Ferriz, 1994), the lower Oligocene of Kazakhstan ( Akhmetiev, 1991) and Russia ( Ablaev et al., 1993), the Miocene of east China ( Hu and Chaney, 1940; Wang et al., 2003), Oligocene to upper Pliocene of Europe ( Szafer, 1950, 1954; Tralau, 1963; Negru, 1972; Zhilin, 1989; Mai, 1995), and the Miocene to Pliocene of Japan ( Tanai, 1961).

Many fossil fruits ( Call and Dilcher, 1997; Manchester, 1999; Manchester et al., 2009) have been reported from the Bovay and Bolden clay pits and other localities (personal observation). However, only one fragmentary leaf, i.e., Eucommia rolandii Call and Dilcher (1997, p. 808 -809, figures 13, 14, 18, 19), has been reported from the Bovay locality.

Call and Dilcher (1997, figure 9) indicated that one fruit (UF15738-011030) possesses two mature carpels. Our examination of both part and counterpart of this specimen ( Figure 22.12-13 ) shows that they are two fruits compressed together at their apices. If, as interpreted by Call and Dilcher (1997), the two nearly equally developed carpels form a bilaterally symmetrical samara whose apical stigmatic cleft, ventral suture, and stipe lie along the median longitudinal plane of the samara, it would be difficult to explain the gap between the two carpels at the base and why only one carpel bears the stipe.

Figures

FIGURE 22. Eucommia eocenica (Berry) Brown, 1940: 1) UF 15737-008218. Fruit showing apical stigmatic cleft (sc), fertile carpel (fc) bearing a conspicuous reticulum (r) composed of fascicles of vascular strands, infertile carpel (ic), and carpel suture (cs). Scale bar equals 2 mm; 2, 3) UF 15737-011033, 011033’. Part and counterpart of a specimen showing stout stipe (s). Scale bar equals 3 mm; 4) UF 15737-011032 - Incomplete fruit showing longer stipe. Scale bar equals 2 mm; 5) UF 15737-011063. Well developed fruit showing vascular strands of the reticulum and stout stipe. Scale bar equals 2 mm; 6) UF 15737-011035. Distal half of fruit showing compression of latex strands and strong carpel suture. Scale bar equals 2 mm; 7) UF15738-011027. Fruit showing stout stipe. Scale bar equals 3 mm; 8-9) UF15737-011022, 011022’. Fruit showing impression of reticulum, and compression of vascular and latex strands. Scale bar equals 3 mm; 10) UF 15737-008219. Fruit showing well developed fertile carpel on the right and infertile carpel on the left. Scale bar equals 3 mm; 11) UF 15737-011065. Fruit showing a complete stipe. Scale bar equals 3 mm. 12-13) UF 15738-011030a, 011030'a. Part and counterpart of a specimen showing two fruits. Note stigmatic cleft (sc). Scale bar equals 3 mm; 14-15) UF 15738-0052526, 0252526'. Part and counterpart of a specimen showing stigmatic cleft, reticulum, and stipe. Scale bar equals 3 mm; 16-17) UF15738-011028, 011028'. Fruit showing short stipe. Scale bar equals 3 mm.