Iodes passiciensis, Del Rio & De Franceschi, 2020

Rio, Cédric Del & Franceschi, Dario De, 2020, Icacinaceae fossil fruits from three sites of the Paris Basin (early Eocene, France): local diversity and global biogeographic implications, Geodiversitas 42 (2), pp. 17-28 : 19-20

Iodes passiciensis

Del Rio & De Franceschi, sp. nov. ( Fig. 2 A-I)

Endocarp bilaterally symmetrical, unilocular, elliptical, lenticular in transverse section; outer surface of the endocarp with a reticulate pattern of rounded and thin ridges with a channel on the median apical part, enclosing 25-29 polygonal areoles per face, with few or no free-ending ridgelets; a keel surrounds the fruit in the plane of symmetry with the thicker side containing a vascular bundle embedded in the endocarp wall. Endocarp possesses a small pair of pores. Inner endocarp surface densely covered with regularly spaced and sessile rounded papillae. Endocarp length c. 7 mm, width c. 4.4 mm.

HOLOTYPE. — MNHN.F.44736 .

PARATYPE. — MNHN.F.44739 .

ETYMOLOGY. — From the latin name of Passy (Passicum) where the fossil taxon was recovered.

STRATIGRAPHY. — Early Eocene.

TYPE LOCALITY. — Passy ( France).

DESCRIPTION

Endocarp bilaterally symmetrical, unilocular, elliptical, lenticular in transverse section; length 6.7-7.2 mm, width c. 4.4 mm, thickness c. 4.4 mm. Outer part of the endocarp with a reticulate pattern of rounded and thin ridges with a channel on the median apical part of its surface corresponding to the trace left by the outer vasculature at the boundary between endocarp and mesocarp; 4-5 irregular longitudinal ridges and some inter-ridges, enclosing 25-29 polygonal areoles per face with few or no freely ending ridgelets ( Fig. 2A, C ); a keel surrounds the fruit in the plane of symmetry with one part thicker containing a vascular bundle embedded in the endocarp wall ( Fig. 2B ). Endocarp possessing a small pair of pores, positioned eccentrically and subapically on the apical endocarp ( Fig. 2F ); endocarp wall 0.15-0.21 mm thick (excluding ridges, 0.34-0.44 mm thick including ridges, Fig. 2G ). Cell walls of the endocarp not preserved. Inner endocarp surface densely covered with regularly spaced and sessile rounded papillae, 0.011 -0.019 (avg. 0.016 mm) in diameter ( Fig. 2H, I ).

REMARKS

This species is represented by only two lignitic endocarps.

SYSTEMATIC AFFINITY

Iodes passiciensis , sp. nov. is unique in having the following combination of characters: 25-29 areoles with no freely ending ridgelets, small pores and rounded ridges. This species differs from I. reidae Del Rio, Thomas & De Franceschi in having a pattern of reticulation more developed and a smaller size (both not overlapping). Iodes passiciensis , sp. nov. differs from I. tubulifera Del Rio, Thomas & De Franceschi in having rounded ridges and a smaller size. The horn-like protrusions are also more obvious in I. tubulifera and protrude sub-apically whereas we have pores in this new species. This species is similar to I. rivecourtensis Del Rio, Thomas & De Franceschi in having rounded ridges, small pores and a reticulation pattern developed without free ending ridgelets. However, I. passiciensis , sp. nov. is smaller, with more areoles, and with a smaller endocarp wall and ridges. This species differs from I. sinuosa Del Rio, Thomas & De Franceschi in having distinctly rounded ridges (despite the absence of cell wall preservation) and a more strongly developed reticulate pattern, but is close in other aspects. Iodes parva Del Rio, Thomas & De Franceschi is close to this species but is smaller, with fewer areoles and has horn-like protrusions that clearly protrude out from the endocarp wall. It also differs from Iodes occidentalis S.E. Allen, Stull & Manchester in lack of free-ending ridges and pores. Iodes multireticulata Reid & Chandler ( Stull et al. 2016) lacks pores and are bigger than those of I. passiciensis , sp. nov. Iodes germanica Knobloch & Mai is slightly smaller (4-5 mm) than this new species and apparently lacks pores ( Knobloch & Mai 1986). Iodes bilinica (Ettingshausen) Stull, Adams, Manchester & Collinson differs by the presence of frequent free-ending ridges. The length and width of I. eocenica Reid & Chandler ( Stull et al. 2016) are almost double those of I. passiciensis , sp. nov. Iodes acutiformis Chandler possesses an acute apex ( Chandler 1962), unlike I. passiciensis , sp. nov., but seems to be very similar in other characters despite having a more relaxed reticulation pattern. Iodes brownii (Berry) Stull, Adams, Manchester & Collinson and I. corniculata Reid & Chandler have a similar number of areoles but are larger in size. The channel on the median apical part of the ridges is also found in the species I. rigida Del Rio & De Franceschi from Le Quesnoy site. However, the ridge structures are different with I. rigida that showing an I-beam-like shape of ridges (almost rectangular). All these considerations allow us to describe a new species from these two specimens, which is close to I. sinuosa and I. parva described from the Rivecourt site.

Figures

FIG. 2. — A-I, Iodes passiciensis Del Rio & De Franceschi, sp. nov. (MNHN.F.44736): A, lateral view of an endocarp showing the reticulum pattern of rounded and thin ridges; B, dorsal view showing the keel, surrounding the endocarp; C, lateral view of second face of the endocarp; D, basal view; E, apical view; F, magnification showing the pores abraded; G, SEM view of wall and ridges in transversal section;H, SEM view of rounded papillae; I, same with magnification. J-Q, Iodes reidae Del Rio, Thomas & De Franceschi (MNHN.F.44737): J, lateral view of endocarp showing the reticulum pattern of rounded ridges; K, dorsal view showing the keel, surrounding the endocarp; L, lateral view of second face of endocarp; M, basal view; N, apical view; O, magnification showing the areoles from the reticulation of ridges; P, SEM view of wall and ridges in transversal section; Q, SEM view of the trace left by the vascular bundle embedded in the endocarp wall. Scale bar: A-E, 5 mm; O-Q, 1 mm; J-N, 10 mm; G, 500 µm; F, 100 µm; H, 50 µm; I, 10 µm.