Mastixia cf. oregonensis (R.A.SCOTT) TIFFNEY et HAGGARD, 1996

Manchester, Steven R. & Collinson, Margaret E., 2022, Mastixioid Fruits (Cornales) From The Early Eocene London Clay Flora: Morphology, Anatomy And Nomenclatural Revision, Fossil Imprint 78 (1), pp. 310-328 : 318

Mastixia cf. oregonensis (R.A.SCOTT) TIFFNEY et HAGGARD, 1996

Text-fig. 4a–i

1954 Mastixioidiocarpum oregonense R.A.SCOTT , p. 84, pl. 16, figs 16–18.

1994 Mastixioidiocarpum oregonense R.A.SCOTT ; Manchester, p. 43, text-fig. 10B, pl. 10, figs 4–11.

1996 Mastixia oregonensis (R.A.SCOTT) TIFFNEY et HAGGARD , p. 42, pl. 2, figs 1–3.

R e m a r k s. Although the holotype that Reid and Chandler (1933) designated for Mastixia cantiensis belongs instead to Diplopanax (see above), some of the paratypes they identified to Mastixia cantiensis are readily distinguished from Diplopanax in having prominent endocarp sculpture and a pair of prominent ovular bundle canals in the endocarp adjacent to the germination valve margins. In particular, the specimens V. 22955 ( Reid and Chandler 1933: pl. 25, fig. 4), V. 22960(1) ( Text-fig. 4a–c ), and V. 22963(2) ( Text-fig. 4e–f ) resemble the fossil genus Mastixioidiocarpum R.A.SCOTT , previously described from the Eocene Clarno Formation of Oregon, USA ( Scott 1954, Manchester 1994). That fossil genus was subsumed into Mastixia by Tiffney and Haggard (1996), who noted that the only difference from modern species of the genus is the more prominently sculptured endocarp. Tiffney and Haggard (1996) also attributed similar fruits from the late Eocene LaPorte flora of California to the extant genus.

A clear distinction between the Oregon species and the London Clay specimens has not been seen, but the London Clay specimens typically show less prominent sculpture due to abrasion. We treat specimens of this kind as Mastixia cf. oregonensis . In Europe, such prominently sculptured fossil endocarps are present in some species of Eomastixia but are rare in Mastixia . Most similar are Mastixia thomsonii MAI from the Miocene of Konzendorf and Düren, Germany ( Mai 1970) and M. rattazzii MARTINETTO ( Martinetto 2011) from the Oligocene of Germany and Italy, respectively.

Figures

Text-fig. 4. Mastixia cf. oregonensis (R.A.SCOTT) TIFFNEY et HAGGARD from the London Clay, originally included within the concept of M. cantiensis. a–c: V. 22960(1). a: Transverse fracture, showing c-shaped locule, dorsal infold, and sculptured endocarp, reflected light. b: Transverse digital section from micro-CT scan data. c: Surface view of ribbed endocarp extracted from micro-CT data. d: Transverse fracture, reflected light, V. 22955 (originally illustrated in pl. 25, fig. 4 of Reid and Chandler 1933). e, f: Transverse physical section, V. 22963(2) showing U-shaped locule and longitudinal dorsal infold. g–i reflected light. g: Detail from left of (d). h, i: Detail from right of (f). Scale bars 5mm in (a–f), 1mm in (g–i).