Two previously unidentified palynomorphs are common in Upper Tertiary deposits in the southern Gulf-Caribbean region. One is now identified as pollen of Mortoniodendron (Tiliaceae; Upper Miocene of Veracruz, Mexico, Middle Miocene of Panama, Pleistocene of Panama). The other represents spores of Sphaeropteris/Trichipteris (Cyatheaceae; Upper Miocene of Veracruz, Mexico). Neither have previously been reported in the fossil record. For a number of years two very distinct, unidentified palynomorphs have been known from Cenozoic deposits in the southern Gulf-Caribbean region. One of these is a relatively small, oblate, tricolpate, finely reticulate pollen grain with conspicuous endexine thickenings about the shortened colpus (costae colpi). The other is a trilete spore with numerous conspicuous pits in the wall. The biological affinities of the microfossils were unknown, but considering the relatively recent age of the specimens and their distinctive morphology, it seemed likely identifications would eventually be made. Both microfossils have now been identified, and they represent genera previously unreported in the fossil record. MORTONIODENDRON (Tiliaceae) Pollen description (fossil). -Peroblate, oval-triangular in polar view; tricolpate, the colpi equatorially arranged, meridionally elongated, equidistant, the inner margin entire, short (ca. 3.5 um apex to equator), conspicuous costae colpi ca. 1.5-2 um wide; semitectate; finely to moderately reticulate (diameter of the lumen from ca. 1 um to 3 um at the poles, finer toward the equator), reticulum closed, regular, the muri ca. 0.5 jm wide, straight to occasionally slightly sinuous, the surface psilate, the margins entire; size 18-27 um. This pollen type was recovered from the Upper Miocene Paraje Solo Formation, exposed in southeastern Veracruz state near the port of Coatzacoalcos, Mexico (Graham, 1976: 840, figs. 248-255; Fig. 3, this report). Later specimens were also found in core material from Gatun Lake, Canal Zone, Panama (Fig. 2). These sediments are from the Gatun Formation and are Middle Miocene in age. Bartlett & Barghoorn (1973: 242) reported similar specimens from Pleistocene deposits of the Canal Zone and suggested they may represent Mortoniodendron, although reference material was not available to them. The specimens have long been thought to represent some member of the Tiliaceae, or possibly the Stercu' I gratefully acknowledge reference pollen material and information on Mortoniodendron provided by Lorin Nevling (Field Museum). Gerald Gastony (Indiana University) provided spore material of Sphaeropteris and Trichipteris, as well as the SEM photomicrograph of Sphaeropteris, and his help and suggestions are sincerely appreciated. 2 Department of Biological Sciences, Kent State University, Kent, Ohio 44242. ANN. MissouRI BOT. GARD. 66: 572-576. 1979. 0026-6493/79/0572-0576/$00.65/0 This content downloaded from 207.46.13.160 on Mon, 17 Oct 2016 05:20:35 UTC All use subject to http://about.jstor.org/terms 1979] GRAHAM-MORTONIODENDRON AND SPHAEROPTERIS/TRICHIPTERIS 573 liaceae, because of the distinctive thickenings about the shortened colpi, as occur in Tilia. The principal difference between the fossil specimens and pollen of Tilia is that the fossil grains are only about half the size (ca. 18-27 um vs. 40-50 jum). Limited amounts of flowering material of two species (M. guatemalense Standley & Steyermark, Fig. 1; M. membranaceum Standley & Steyermark) were obtained from the Field Museum (Nevling, pers. comm., 1976), and the fossil specimens can now be referred to Mortoniodendron. The genus consists of about five species distributed from Mexico (states of Chiapas, Veracruz) through Central America. The plants range from small shrubs ca. 1 m tall (M. hirsutum Standley, Panama; M. membranaceum Standley & Steyermark, Honduras) to tall tropical forest trees (M. anisophyllum (Standley) Standley & Steyermark, Costa Rica, Panama). In Costa Rica the genus is represented in the lowlands of the Golfo Dulce by M. anisophyllum and M. guatemalense var. australe Morton & Steyermark. There the former species includes trees up to 30 m tall, and with the larger specimens strongly buttressed. In Veracruz M. guatemalense occurs in the Selva Alta Perennifolia (high evergreen selva, tropical rain forest) associated with Terminalia amazonia (Gmell.) Exell, Calophyllum brasiliense Camb., Dialium guianense (Aubl.) Sandwith, Bernoullia flammea Oliver, Brosimum alicastrum Sandwith, Ficus tecolutensis (Liebm.) Miq., and Pseudolmedia oxyphyllaria Donn.-Smith as dominants. Other aspects of the distribution and ecology of Mortoniodendron have been noted by Allen (1956: 268-269), Gomez-Pompa (1973: 108, 111), and Robyns (1964: 15-18). The genus is poorly known taxonomically and individual species are rarely represented by both flowering and fruiting herbarium material; Robyns (Paris) is presently preparing a monograph of Mortoniodendron. There have been too few studies in neotropical Cenozoic paleobotany to accurately summarize the probable stratigraphic range and paleogeographic distribution of Mortoniodendron. It is present in the Middle Miocene Gatun Formation of the Canal Zone, the Upper Miocene Paraje Solo Formation of Veracruz, Mexico, and in the Pleistocene Gatun Lake deposits of the Canal Zone; all are within the present range of Mortoniodendron. It has not been recovered from palynofloras studied from the lower Middle Eocene Chapelton Formation of Jamaica (Graham, 1977; unpubl. data), the Oligo-Miocene Simojovel Group of Chiapas, Mexico (Langenheim et al., 1967), the Oligocene San Sebastian Formation of Puerto Rico (Graham & Jarzen, 1969) or from the several Eocene to Oligo-Miocene microfloras presently under study from Panama (Graham, unpubl. data). It is not mentioned in Germeraad et al.'s extensive 1968 summary of Tertiary palynology of South America. To my knowledge it has not been reported from either the modern or fossil floras of South America, nor is it presently known from the megafossil record. Thus on the basis of information currently available, Mortoniodendron ranges from Middle Miocene to Recent, based on three known occurrences in southern Mexico and the Canal Zone. SPHAEROPTERIS/TRICHIPTERIS (Cyatheaceae) Spore description (fossil) .-Radially symmetrical, the amb oval-triangular, the margin lobate (from pits in equatorial section); trilete, the arms straight, This content downloaded from 207.46.13.160 on Mon, 17 Oct 2016 05:20:35 UTC All use subject to http://about.jstor.org/terms 574 ANNALS OF THE MISSOURI BOTANICAL GARDEN [VOL. 66