Tectocarya grandis (E.REID et M.CHANDLER) Manchester & Collinson, 2022

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 : 312-315

Tectocarya grandis (E.REID et M.CHANDLER) MANCHESTER et M.E.COLLINSON comb. nov.

Text-fig. 2a–n

B a s i o n y m. Mastixia grandis E.REID et M.CHANDLER ( Reid and Chandler 1933: The London Clay flora, p. 450, pl. 25, figs 7–9).

H o l o t y p e. V.22968 (Natural History Museum,

London).

P l a n t F o s s i l R e g i s t r y N u m b e r. PFN002905

(for new combination).

R e m a r k s. We studied the holotype of this species, V. 22968, by light microscopy of the exposed surfaces and by micro-CT scanning. It lacks the pair of prominent ovular bundles diagnostic of Mastixia and its close relatives Eomastixia and Retinomastixia KIRCHH. The separation planes of the germination valve margins directly intercept the locule limbs, indicating similarity to Diplopanax and to the fossil-genus, Tectocarya . The preserved part of the pericarp is resolved into two main layers, a dense layer of mostly periclinally oriented fibres lining the locule, about 1/5 of the wall thickness, and a thick outer layer with fibres and sclereids predominantly anticlinal in orientation with scattered, variously oriented vascular strands and canals.

Digital transverse sections of the T. grandis holotype ( Text-fig. 2h–n ) show that the dorsal infold has a median septum of fibres dividing the surrounding parenchymatous tissue into two longitudinal pockets ( Text-fig. 2k–n ) – a feature diagnostic of Tectocarya KIRCHH. ( Kirchheimer 1935, 1936, 1957; herein Text-fig. 2o–s ). Although the holotype of London Clay species is hereby reassigned to Tectocarya , the second specimen listed and figured under the name Mastixia grandis by Reid and Chandler (1933: 451, pl. 25, fig. 9; V. 22969; herein Text-fig. 5d, f, h ) appears to represent a distinct taxon, possibly Mastixiopsis .

Tectocarya was previously reported only from the Miocene, with three species distinguished by features of fruit shape, size, sculpture and relative thickness of endo- and mesocarp ( Kirchheimer 1935, 1936, 1957, Mai 1993). This genus is morphologically and anatomically similar to Diplopanax , but the distinct median septum of the dorsal infold characteristic of Tectocarya ( Text-fig. 2o, q, r ) has not been observed in the extant species of Diplopanax (cf. pl. 2, figs 1–12 of Manchester and Collinson 2019).

Tectocarya grandis represents the first recognition of an early Eocene species of Tectocarya . The specimen is from the Isle of Sheppey, UK where the age range of the London Clay is between 53.5 and 51.5 Ma ( Collinson et al. 2016). Another Eocene example, from the late Eocene of Post, Oregon, USA, formerly misassigned to Mastixicarpum occidentale MANCHESTER ( Tiffney and Haggard 1996, Manchester and McIntosh 2007), is also clearly recognizable as Tectocarya based on the septum in the dorsal infold ( Text-fig. 2r, s ). The holotype of M. occidentale from the Clarno Nut Beds ( Manchester 1994) is retained in Mastixicarpum , however, and does not represent Tectocarya .

Figures

Text-fig. 2. Tectocarya spp. a–n: Tectocarya grandis (E.REID et M.CHANDLER) comb. n. Holotype V.22968. a: Lateral view of broken endocarp, reflected light. b–d: Longitudinal views, surface renderings from micro-CT data. e: Translucent volume renderings. f: Apical view, surface rendering. g: View of transversely broken surface showing curved locule, reflected light. h–n: Successive digital transverse sections. Note septum in the dorsal infold (arrows). o, p: Tectocarya rhenana KIRCHH., Miocene of Germany, dorsal view and transverse section [Holotype of Mastixoidea tectocaryoides KIRCHH., Alfred Mine near Konzendorf, photo by Dieter Mai] (Synonym of T. rhenana MAI, 1993). q: T. rhenana transverse section. from Mine Alfred, Düren, Germany, coll. Claire A. Brown 1952, USNM 355632. r, s: Tectocarya sp. from late Eocene of Post, Oregon, USA, physical transverse section, reflected light. UF279-50014. [Surface views of same specimen shown in Manchester and McIntosh 2007: figs 62, 63]. Scale bars 1cm in (a–r), 0.5cm in (s).

Text-fig. 5. Mastixiopsis nyssoides KIRCHH. a, b, g–n: Organic preservation. a, b: Lignitic, unpermineralized, early Eocene Dorset Pipe clays at Arne, V. 40762. a: Ventral view (original illustration from pl. 18, fig. 1 of Chandler 1962). b: Transverse fracture, somewhat distorted by compression. c–f: Pyrite permineralization. c: Ventral view, V. 22963(1) from Sheppey, originally listed as Mastixia cantiensis. d: Lateral view, V. 22969 from Sheppey (identified as Mastixia grandis by Reid and Chandler 1933: pl. 25, fig. 8). e: Equatorial transverse physical section from (c). f: Equatorial transverse physical section from (d). g: Detail of pericarp from (e), showing endocarp formed of dense fibrous tissue, surrounded by mesocarp of anticlinally oriented larger cells. h: Detail of pericarp from (f). i–n: Type material from Eocene of Riestadt, Germany, MNB. i: Ventral view. j, k: Ventral and apical views of holotype. l: View of the transversely fractured surface from (j) showing horseshoe shaped locule. m: Equatorial transverse physical cut of the specimen in (i); note yellow resin cavity (arrow). n: Scanning electron microscopy of pericarp from (l) with locule lining at lower edge of image. Note dense endocarp tissue composed of small cells (fibres and sclereids), extending about 3/5 of distance to periphery, surrounded by mesocarp of larger, anticlinally oriented cells. Scale bars 1cm in (a–f), (i–k), 1mm in (g), 2mm in (h), 3mm in (l), m, 250 Μm in (n). Bar in (d) applies also to (c). Bar in (l) also applies to (m). Bar in (i) also applies to (j) and (k).