Platanites marginata (LESQUEREUX) K. JOHNSON

Manchester, Steven R., 2014, Revisions To Roland Brown’S North American Paleocene Flora, Acta Musei Nationalis Pragae Series B 70 (3 - 4), pp. 153-210 : 166

Platanites marginata (LESQUEREUX) K. JOHNSON

1873 Viburnum marginatum LESQUEREUX , p. 395; 1878 p. 223, pl 37, fig. 11, pl. 38, figs 1–4. (basionym).

For synonymy see Johnson (1996).

The compound-leaved plant formerly called Cissus marginata (LESQUEREUX) BROWN was recombined as

Platanites marginata (LESQUEREUX) K. JOHNSON (1996) . In addition to the complete compound-leaved specimens illustrated by Brown (1962), excellent examples are known from the uppermost Cretaceous Hell Creek Formation ( Johnson 1996). Brown (1962, p. 65) noted “The leaves of P. raynoldsii are in general not strongly lobed, and they resemble the terminal leaflets of Cissus marginata (LESQUEREUX) BROWN [here treated as Platanites marginata ] so closely that separation of the two species, especially when they are poorly preserved, is virtually impossible”. It is possible that P. marginata and P. raynoldsii are conspecific–if so, then the older epithet, raynoldsii , takes priority. However, the type specimen of Platanites marginata have a narrower angle between primary and secondary veins than is typical of P. raynoldsii .

Although compound leaves do not occur in extant Platanus , some of the extinct Cretaceous and Tertiary genera of Platanaceae were indeed compound. Platanites is recognized by its trifoliately compound leaves. Extinction of Platanites apparently occurred sometime after the middle Eocene; the youngest known occurrences are from the Eocene of Kisinger Lakes, Wyoming ( MacGinitie 1974, pl. 14, fig. 1), and John Day Gulch, Oregon (UF 27869, 27870, loc. 265). A related extinct genus, Erlingdorfia, with more distinct lobing of the trilobed terminal leaflet and markedly asymmetrical bilobed lateral leaflets, is apparently confined to the Late Cretaceous ( Johnson 1996).

“ Platanus ” bella (HEER) Z. KVAČEK , MANCHESTER et S.X. GUO

In addition to the above platanaceous taxa recognized by Brown (1962), Hickey (1980) found compound leaves that he referred to as Debeya sp. from the Paleocene of Montana. KVAČEK et al. (2001) showed that these trifoliate leaves match, in epidermal as well as architectural characters, those from the Paleocene of Greenland and China known as Platanus bella . Like Platanites , the leaves were compound, but in this species the leaflets were elliptical, without any lobation. Thus they resemble the lamina shape of extant Platanus kerrii , but that species, like all extant Platanus species, has only simple leaves. Cuticular investigations have revealed epidermal anatomy in this species conforming with extant Platanus ( Kvaček et al. 2001) . Although Kvaček et al. placed the leaves in an extinct subgenus of Platanus , named Glandulosa , it can be argued, based on the current concept of ranks within the family, including Macginitiea , and Platanites as genera distinct from Platanus , that this taxon also requires separate generic status. Kvaček et al. (2001) explained, however, that names previously considered, including Dewalquea and Debeya would be inappropriate for this species due to differences from the type material.