Carya costata (C. PRESL ex UNGER) UNGER , 1850

Manchester, Steven R. & Kvaček, Jiří, 2024, Morphology And Affinities Of Carya Costata Hickory Nuts From The Oligocene Of Bohemia, Fossil Imprint 80 (1), pp. 154-160 : 158-159

Carya costata (C. PRESL ex UNGER) UNGER, 1850

Text-figs 2a, 3, 4a–p, 5

1838 Juglandites costatus C. PRESL in Sternberg, vol. II, 7/8, p. 207, pl. 58, figs 7–13, nom. inval. (ICN Art. 35.1)

1845 Juglandites costatus C. PRESL ex UNGER , p. 241.

1850 Juglans costata (C. PRESL ex UNGER) UNGER , p. 468.

1860 Carya costata (C. PRESL ex UNGER) UNGER , p. 41.

L e c t o t y p e. NM-E193 ( Sternberg 1838: pl. 58, fig. 10), selected by Mai (1981); for more details see Art. 40.3. of the Shenzhen Code ( Turland et al. 2018).

R e p o s i t o r y. Palaeobotanical Collection, National

Museum, Prague, the Czech Republic.

T y p e l o c a l i t y. Počerny near Karlovy Vary, the Czech Republic (non Staré Sedlo “Altsattel”; for more details see Kvaček et al. 2021) .

T y p e h o r i z o n. Volcanic complex above the coal seam Josef of the Sokolov Basin; Oligocene.

N o m e n c l a t u r a l h i s t o r y. This species was first described and figured as Juglandites costatus by C. Presl in Sternberg (1838: 207, pl. 58, figs 7–13); however the name was invalid according to Article 35.1 of ICN as noted by Kvaček et al. (2021), and subsequently validated with its publication as Juglandites costatus C. PRESL by Unger (1845). Subsequently, Unger (1850) transferred it to the extant genus Juglans . A decade later, Unger (1860) transferred the species to Carya : as Carya costata (C. PRESL) UNGER ( Unger 1860: 41, pl. 18, figs 13–17, pl. 19, fig. 16). From the original syntypes illustrated by Sternberg (1838), Mai (1981) selected NM-E173 as lectotype.

E m e n d e d d i a g n o s i s. ( Mai 1981, translated, with modifications in bold). Nut 25–35 mm long and 20–30 mm wide, suborbicular, apical tip missing, but somewhat pointed, base rounded with a rhombic attachment point; surface smooth with faint longitudinal grooves and four subtle longitudinal corners. Nutshell 2.6–3 mm thick on average (inner anatomy unknown); with small, slightly high secondary septum, which extends perpendicular to and along the primary septum to, at most, half the compartment length, but which does not extend outward to partition the locule; locule cast compressed, smooth to transversely wrinkled, 2 - to 4-lobed at the base, primary lobes both of equal length, rounded to triangular at base, with a crest-like ridge on the dorsal side, 19–33 mm long, 17–22 mm wide, reaching up to 18 mm deep into each shell.

D e s c r i p t i o n.The nuts are subovoid, wider in plane of the primary septum than in the plane of germinal separation. The surface is smooth to finely longitudinally grooved, with four subtle longitudinal corners (indicating margins of the shed husk valves) (arrows in Text-fig. 4i, k, o). The locule shows a prominent longitudinal cleft corresponding to the primary septum; however, the secondary septum is weak to absent, usually expressed only as a perpendicular flange on the primary septum. Lacunae within the nutshell are apparent in some specimens, where sediment has infilled ( Text-fig. 4b, g, e). There is one pair of shallow inner ribs on the nutshell straddling the plane of germinal splitting. The base of the locule, as viewed in the plane of germinal separation, is rounded to cuneiform ( Text-fig. 4a, i, l, m).

D i s c u s s i o n. Mai (1981) considered that Carya costata remains an unclear species, rendered heterogeneous due to later additions by other authors. He summarized other published reports of nuts attributed to C. costata but questioned their identification due to uncertain internal morphology. Here we focus only on material from the type area of Karlovy Vary (W. Bohemia) in anticipation that it will be helpful in re-evaluating specimens from other sites.

Our emended diagnosis differs from that of Mai (1981) mainly in the description of the base of the locule. Mai indicated that the locule cavity is basally 4-lobed, but in most of the type material it has only two lobes, separated by the primary septum; each of those lobes is rounded to triangular with no emargination of the kind seen in other species of Carya due to their prominent secondary septum ( Text-figs 3a, l, m, d, 4h). As he described, there can indeed be a secondary septum that runs lengthwise as a flange along both sides of the primary septum, but it does not extend across the locule to form a basal partition of the locule. The secondary septum is evidenced by a groove on the ventral side of the locule casts as viewed from the basal side (e.g., Text-fig. 3n) or ventral side (e.g., Text-fig. 5g). This is much like the weak secondary septum observed in fossils of Carya ventricosa ( Text-fig. 4s).

Nuts of Carya costata closely resemble those of C. ventricosa in the shallow inner ribs of the nutshell, weak development of secondary septum, and cuneiform base of the locule cast. The morphology of the locules is nearly identical (compare Text-fig. 4d, with Text-fig. 4t, and Text-figs 4l, 5e, with Text-fig. 4s). A distinctive feature of these nuts is that, rather than being radially symmetrical like nuts of most extant and fossil species of Carya , they are wider in plane of the primary septum than in the plane of germinal separation, as can be seen in apical ( Text-figs 4k, l, 5d) and basal ( Text-figs 3k, n, o, r, 4a, c) views as well as transverse sections ( Text-figs 4g, 5e). The same feature is also apparent in nuts of Carya ventricosa , although it was not emphasized in earlier treatments ( Text-fig. 4j).

Based on the observed similarities, it seems likely that Carya costata and C. ventricosa represent the same lineage, and perhaps the same biological species, differing mainly by the mode of preservation – lignitic in the case of C. ventricosa , but molds and casts in sediment in the case of C. costata . The older age inferred for C. costata (Oligocene) may indicate that the C. ventricosa lineage was already established in the Paleogene. We do not wish to synonymize these species because of the difference in preservational state, but it is worth noting that the name Carya ventricosa would take priority over C. costata , because the former epithet was validated when published as Juglans ventricosa by Brongniart (1828: 144) whereas the latter was validated later ( Unger 1845).

Deng et al. (2024) surveyed the morphology of many extant species of Carya by micro-CT scanning and recognized features that can distinguish extant North American species from the Asian ones. All North American species, and some of the Asian species, have strong inner longitudinal ribs in the locule on either side of the germination splitting plane; however, C. poilanei of Vietnam and Yunnan, China, as earlier observed by Mai (1981), has only shallow inner ribs, as is also reflected in the locule cast morphology. Carya costata also lacks prominent inner ribs. The C. costata specimens show some remnants of lacunae within the shallow ribs of the nutshell, preserved as casts (arrows in figs 3b, g, 4e).

Although not obvious from casual examination of the fossil specimens, many of the specimens we studied were damaged by gnawing ( Text-figs 3p, 4d, g-i, m, n, 5c, d, l-o), and the preservation of inner details is in part due to the fact that sediment could enter the nutshell through openings made by chewing animals prior to deposition to form casts of the locule and lacunae. Although such damage could possibly have been caused by birds or perhaps insects, the perpendicular grooves on the edges of the holes suggest the markings of rodent incisors. This is taken to indicate that hickory nuts were an important as a food source for these animals in the Oligocene.