Plants

Hunt, A. P. & Lucas, S. G., 1992, Stratigraphy, paleontology and age of the Fruitland and Kirtland Formations (upper Cretaceous), San Juan Basin, New Mexico, New Mexico Geological Society, New Mexico Geological Society 43 rd Annual Fall Field Conference Guidebook, pp. 217-239 : 223-225

publication ID

https://doi.org/10.5281/zenodo.3614972

DOI

https://doi.org/10.5281/zenodo.4420195

persistent identifier

https://treatment.plazi.org/id/794487B6-D621-8614-F92C-FC90FDFBFF73

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Jeremy

scientific name

Plants
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Plants

The taxonomy of fossil plants from the Fruitland and Kirtland For ­ mations is confused. Most work has been based on the taxonomy of F. H. Knowlton, a preeminent paleobotanist of the early twentieth century. However. Knowlton, as was customary in his time, placed many Cretaceous specimens in modem taxa on the basis of gross mor ­ phological similarities (e.g.. Ficus , Laurus ) and with no regard to variability of the foliage on one plant. Initial collections were made by Bauer and his party ( Knowlton, 1916) and later, smaller samples were reported by other USGS geologists (Lee. I9I7; O ’Sullivan et.al., 1972). Specimens were collected more recently by Kues et al. (1977), Tidwell et al. (1981) and Robison et al. (1982). Large undescribed collections, principally made by J. McClammer, are at NMMNH and YPM.

Most recent workers (e. g., Kues et al .. 1977; Tidwell et al.. 1981) considered the Fruitland and Kirtland floras as one entity. We present separate floral lists for both formations ( Tables 1, 2) because they represent such different environmental settings and different ages. No megafossil plant specimens have been recovered from the Naashoibito Member of the Kirtland Formation. All early collections of plant fossils from the “Ojo Alamo Sandstone" of older usage were from the upper conglomerate or Ojo Alamo Sandstone of modem workers and not from the Naashoibito Member of the Kirtland, which earlier workers con ­ sidered to be part of the “Ojo Alamo." Additional specimens reported by Lee (1917) are from an undivided Fruitland-Kirtland sequence (“Laramie”) near Dulce, but it is clear that they are from the lower Fruitland Formation ( Lee, 1917, plate 25 A). It is not clear if other floras reported by Lee (1917), for example from near Durango, are from the Fruitland or Kirtland. O’ Sullivan et al.. (1972) listed specimens from an undivided Fruitland-Kirtland sequence, and these occurrences are not re ­ peated in Table 1. Kues et al. (1977) and Tidwell et al. (1981) both reported new occurrences but did not report, with a few exceptions, which of the two formations their specimens came from. Taxa that could not be assigned to either formation were not included and this, unfortunately, includes most of the palm diversity.

There are no recent detailed studies of the floras of the Fruitland and Kirtland Formations. Therefore, interpretations of differences in diversity must be considered preliminary, but we think that such comparisons are of some utility. It is clear that although the floras of the Fruitland and Kirtland Formation are of about equal diversity, there are major differences between the two floras ( Tables 1, 2). Ferns are more common in the Kirtland, which reflects the fact that modem fems in the tropics are more common in upland and better drained areas ( Berry, 1924). The genus Anema has modern species that are restricted to swamps ( Tidwell et al., 1981) and is restricted to the Fruitland. Conifers are more diverse in the Fruitland flora, and taxa that are important in swamp communities, such as Brachyphyllum macrocarpum and Sequoia cuneata (Parker, 1976; Tidwell et al., 1981) are restricted to the Fruitland.

The Kirtland flora ( Table 2) contains fewer monocots, which are represented by several families not found in the Fruitland (e g., Cyperaceae , Araceae . Cannaceae ). Palms arc only present in the Fruitland. The dicots form the majority of plant specimens in both the Fruitland and Kirtland floras ( Tidwell et al., 1981). Dicots are more diverse at

Scizaeaceae Anemia hesperia Anemia sp. Polypodiaceae ?Asplenium coloradense Coniferophyta Araucariaceae Araucaria sp. Araucaria longifolia Cupressaceae Brachyphyllum macrocarpum Taxodiaceae Sequoia reichenbachii Sequoia obovata ? Sequoia cuneata Cunninghamites pulchellus Anthophyta Monocotyledonae Palmae Sabalites imperialis Sabalites montana Sabalites sp. Pontederiaceae Heteranthera cretacea Dicotyledonae Saliceae Salix baueri Salix sp. Fagaceae Quercus baueri Moraceae Ficus squarrosa ? Ficus rhamnoides Ficus planicostata Ficus praetrinervis Ficus starkvillensis? Ficus praelatifolia Ficus curta? Ficus wardii Ficus baueri Ficus leei Ficus sp. Nymphaeceae Nelumbo sp. Cercidiphylluaceae?Cercidiphyllum sp. Menispermaceae Menispermites sp. Magnoliacea Magnolia cordifolia Lauraceae Laurus baueri Laurus coloradensis Cinnamomum sezannense Saxifragaceae Ribes neomexicana Leguminosae ? Leguminosites neomexicana Rhamnaceae Rhamnus goldianus?Zizyphus sp. Myrtacea Myrtophyllum torreyi Incertae sedis Phyllites neomexicanus Phyllites petiolatus Pterospermites undulatus Pterospermites sp. Carpites baueri Carpites sp.

Filicophyta

Filicophyta Asplenium neomexicana Asplenium sp. Onoclea neomexicana Woodwarthia crenata Salyinaceae Salvinia sp. Coniferophyta Araucariaceae Araucaria sp. Taxodiaceae Sequoia cuneata Anthophyta Monocotyledonae Cyperaceae Cyperacites sp. Araceae Pistia corrugata Cannaceae ? Canna maqnifolia Dicotyledonae Salicaceae Salix lancensis Juglandaceae Carya antiquorum Fagaceae Dryophyllum subfalcatum Moraceae Ficus crossii Ficus leei Menispermaceae Menispermites belli Magnoliacea Maqnifolia berryi Lauraceae Laurus coloradensis Laurophyllum salcifolium Laurophyllum wardiana Laurophyllum sp. Platanaceae Platanus nobilis Platanus raynoldsi Leguminosae ? Leguminosites neomexicana Rhamnaceae Rhamnus goldianus Rhamnus minutus?Zizyphus sp. Vitaceae Vitis lobata Cissus marginata Dillenaceae Dillenites cleburni Myrtacea Myrtophyllum torreyi Myrtophyllum neomexicanum Caprifoliaceeae Viburnum antiquum Incertae sedis Pterospermites sp. Carpites baueri Carpites lancensis Carpites sp.? Ficus trineruis unidentified flowers and fruit

the family level in the Fruitland, being represented by 14 families as opposed to 12 in the Fruitland. However, the specific diversity is apparently greater in the Fruitland flora, particularly within the Moraceae ( Table 1).

The floral evidence agrees with a general increase in drainage from the Fruitland to Kirtland. The abundance of medium-sized angiospermous leaves with entire or nearly entire margins and drip points suggests a warm-temperature to subtropical climate during deposition of both formations by analogy with modern floras ( Lucas, 1981; Tidwell et al., 1981; Robison et al., 1982).