Palaeocarpinus joffrense SUN et STOCKEY

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 : 172

Palaeocarpinus joffrense SUN et STOCKEY

Infructescences and spiny-bracted fruits of the extinct betulaceous genus Palaeocarpinus CRANE were described by Brown as bur-like objects. The examples figured by Brown (1962 pl. 67, figs 39–42, 47) and Crane (1989, fig. 6.5F) correspond to Palaeocarpinus joffrense SUN et STOCKEY which was described based on infructescences and fruits from the Paleocene of Alberta ( Sun and Stockey 1992) and the late Paleocene-early Eocene Storvola flora of Spitsbergen ( Golovneva 2002, Budantsev and Golovneva 2009). Leaves that Brown called Corylus insignis were likely produced by the same plant. Brown (1962) used the name Corylus insignis HEER based on the specimens Heer (1871) identified from Greenland. Golovneva (2002) showed that the epithet malmgrenii (from Tilia malmgrenii Heer 1868 from the Eocene of Spitsbergen) takes priority for such leaves and observed that the “American leaves are morphologically identical to the leaves from Spitsbergen, associated with fruits of the same species.” The genus Corylites has been considered appropriate for leaves of this kind in association with Palaeocarpinus ( Manchester and Guo 1996), but Golovneva (2002) argued in favor of the genus Craspedodromophyllum CRANE. Golovneva provided a new combination Craspedodromophyllum malmgrenii (HEER) GOLOVNEVA , using the fossil-genus that Crane had established for foliage associated with Palaeocarpinus fruits from the Paleocene Reading Beds of England. Thus, C. malmgrenii applies to the Corylus -like leaves associated with Palaeocarpinus joffrense (i.e., leaves Brown identified as Corylus insignis ) known from several localities in North Dakota, Montana and Wyoming as well as Alberta and Spitsbergen.

Other species of Palaeocarpinus include fruits with very spiny bracts known from two localities in North Dakota ( P. dakotensis MANCHESTER, PIGG, et CRANE 2004), and those with mostly entire-margined bracts from some sites in southwestern Wyoming ( P. aspinosa MANCHESTER et CHEN 1989). These all co-occur with Corylus -like leaves that can be attributed to Corylites or Craspedodromophyllum , although formal specific epithets have not been proposed. As noted by Brown (1962), the single nut specimen that he assigned to Corylus was surprisingly small in comparison with extant Corylus nuts. It may have been either a nut of Palaeocarpinus , or a seed of Taxus , both of which have a longitudinally striate surface and truncate base where the involucre ( Corylus ) or aril ( Taxus ) attached.

Staminate catkins commonly associated with Palaeocarpinus contain Corylus -like pollen ( Manchester and Chen 1996; Manchester et al. 2004; Sun and Stockey 1992). Given the similarities of the leaves and pollen to that of extant Corylus , and the relatively minor differences between Palaeocarpinus and extant Corylus it seems clear that Palaeocarpinus was very close to extant Corylus , possibly plesiomorphic within the same lineage.

An additional betulaceous element common in the Paleocene of Wyoming, not treated by Brown, was the extinct genus Cranea , known from the Bighorn and Powder River basins of Wyoming, consisting of elongate infructescences with some similarity to modern Ostryopsis . Leaves associated with Cranea are more elongate than those of Corylites malmgrenii and have more closely spaced parallel secondary veins ( Manchester and Chen 1998).

Juglandaceae

The Juglandaceae are represented by leaves and fruits in the Paleocene floras reviewed by Brown (1962). Pollen of the family is also well represented and useful in biostratigraphy ( Nichols and Ott 1978, 2006). Brown (1962) used the broad concept of the extant genus Pterocarya (including Cyclocarya ), and accordingly attributed two species to Pterocarya that are now treated as the distinct genera Cyclocarya , and Polyptera MANCHESTER et DILCHER (1982, 1997).