Fossils Attributed to the Orchidaceae

RUDOLF SCHMID AND MARVIN J. SCHMID1

INVESTIGATORS INTERESTED IN the evolutionary history of a family desire to have information from the fossil record to provide (hopefully) unequivocal evidence for the early history of that family. Unfortunately for orchidologists, the known fossil record of the Orchidaceae is extremely meager. We decided to summarize what is known of the fossil record of orchids (a) because there are no accounts available other than the rather superficial ones by Darrah (15) and Krackowizer (27a, 28) , (b) because there are number of misconceptions in the literature that should be corrected, and, most importantly, (c) because a reasonably complete list of fossils attributed to the Orchidaceae could be prepared since we had access to the Compendium Index of Paleobotany (see 3, 19 for accounts of i ts coverage) and to libraries with extensive holdings in rather obscure publications.

Most persons seem to favor a relatively great age for the Orchidaceae (e.g., 1, 5, 6, 12, M, 15, IS, 21-23, 48), but relatively few have ventured a specific time and/or place of origin. Garay (21-23), following Stebbins (48, pp. 501-502), postulates an origin in the early Cretaceous- and in addition proposes Malaysia as the most likely cradle of orchidhood. Leon Croizat (pers. comm., 1972) believes that the orchids arose "surely not later than the earliest Cretaceous. Brieger (5, 6) favors the early Tertiary and the "united Asiatic-American" tropics (6, p. 329, specific area not indicated). In contrast, some authors, notably Schultes, believe that the orchids may be "a comparatively young group" (44, p. 1; 45, p. 1043). While there is some dispute as to the exact time of origin of the family, nearly all workers (e.g., 5, 16, 17, 21. 40, 44) seem to agree that currently, and in the immediate past, the Orchidaceae are in a very active period of evolution.

Most workers have indicated either that there is no fossil record for the Orchidaceae (e.g., 1, 6, 10, 12, 13, 20, 24) or that there are only doubtful orchidaceous fossils (e.g., 15, 16, 18, 21, 25, 32-34, 36, 39, 40, 42, 44, 45). In contrast, a few persons (e.g., I I , 26, 28, 35, 38, 43, 49, 50, 52) have stated that valid orchid fossils exist. Most of these authors apparently based their view concerning the fossil record of the Orchidaceae chiefly or only on knowledge of the very dubiously orchidaceous Protorchis monorchis and Palaeorchis rhizoma described by Massalongo (31-34) from the Eocene of Italy.4 Nevertheless, a number of other fossils have also been attributed to the Orchidaceae, most significantly Straus' (49, 50) three species of putative orchid fruits (Orchidacites) from the Pliocene of Germany. With the exception of Gothan and Weyland (26), Kirchheimer (27), and Melchior (35), however, most recent workers seem unaware of Straus' finds. These and other taxa will be discussed in detail below.

Table 1. Geologic time scale (pre-Mesozoic omitted). (After Hartland, et.al. 26a)

Era Period Epoch Beginning of interval (in millions of years

Quaternary

Holocene (Recent)

Pleistocene (Glacial)

0.005

2.5

Cenozoic

Tertiary

Pleiocene

Miocene

Oligocene

Eocene

Paleocene

7

26

38

54

65

Mesozoic

Cretaceous

Jurassic

Triassic

136

190

225

Orchids are not favorable candidates for fossilization, an obvious conclusion that has not escaped previous authors (e.g., 15, 18, 28, 40. 44). The following characteristics of most Orchidaceae probably account for their scarcity as fossils: (a) predominant occurrence, both in the present and presumably in the distant past, in the wet tropics, which are areas of rapid decay; (b) herbaceous habit; (c) epiphytic habit, which would generally preclude orchids from the conditions (usually aquatic) most conducive to fossilization (see also 15) ; (d) production of pollinia (usually) rather than individual pollen grains, and dispersion of the former by animal vectors instead of wind: and (e) minute, easily degradable seeds. Krackowizer (28) and Schimper and Schenk (43), however, apparently believed a rather extensive fossil record of the Orchidaceae is to be expected, and Darrah (15) and also Krackowizer (28) suggested that fossil orchids might eventually be encountered in deposits in tropical areas when these become better known. Fossils that have been attributed to the Orchidaceae (or to the Protorchidaceae) are strictly megafossils (e.g., fruits, leaves, tubers, etc.); orchidaceous microfossils (e.g., seeds and pollen) have not been reported in the literature. Discoveries of cuticular remains (as those already found of the Pliocene Orchidacites wegelei of Straus, HI) perhaps offer the best hope for significant additions to the fossil record of (he Orchidaceae. Although there is no record of fossil orchid pollen, even if orchid pollen were preserved as fossils, it is a moot point that it would be recognizable as such. Botanists simply might not recognize the fossilized pollen of those orchidaceous forms that had not yet evolved pollinia. Perhaps significantly, the Asclepiadaceae, which like the Orchidaceae possess pollinia, are not listed in Potonie's (41) recent compendium of fossil pollen and spores. Although Chandler's (9, and works cited therein) extensive investigations (initially with the late Eleanor M. Reid) of the Tertiary London Clay Flora of England over a period of several decades failed to reveal any orchidaceous remains,

she suggested (8, p. 29) that "possibly search for pollen among the finer sediments and residues may eventually demonstrate the presence of this family" in the London Clay Flora. Subsequent palynological work (two 1961 Ph.D. theses by Ma Khin Sein and Jane Pallot at the University of London, both cited in 9, the latter published as 30) , however, has thus far failed to substantiate this prediction. As recently discussed by Eyde (19), there are several paths into the paleobotanical literature. We checked a variety of sources for records of orchidaceous fossils, most importantly the index by Andrews (3, including unpublished cards for additions since 19(>5) and the United States Geological Survey's Compendium Index of Paleontology, an unpublished file available for consultation only in the Natural History Building, Room W-300, of the Smithsonian Institution, Washington, D. C. (see 3, 19) . We checked the Compendium Index for most of the temperate genera listed in Schultes and Pease (46). Most tropical genera, however, were not sought in the Compendium Index due to the minuscule yield that could only result from such a mountain of effort. As noted above, tropical plants are unlikely candidates for fossilization. In addition, most tropical orchids are endemics that presumably evolved during the Quaternary, and hence any fossils of them would be unlikely to be encountered by paleobotanists, most of whom have worked (until very recently, at least) in temperate areas. Finally, any orchidaceous fossils of the pre-Quaternary tropical floras of presently temperate areas would probably be given generic names not based on living taxa.

REPORTS OF ORCHIDACEOUS FOSSILS5

Three extinct genera (Palaeorchis, Protorchis and Orchidacites) have been designated as orchidaceous or protorchidaceous. At least one other fossil taxon, Antholithes pediloides, has been regarded as an orchid. In addition, fossil remains from the Quaternary have been attributed to a number of extant, north temperate orchid taxa. Purists who restrict "fossils" to pie-Quaternary remains and therefore regard Pleistocene finds as "subfossils" may object to the inclusion of plant remains from the Quaternary in the following enumera-tion:

Jurassic

The Compendium Index of Paleobotany, citing Thurmann (51) , lists the

following extant species as occurring in the Jurassic strata at Porrentruy, France: Ophrys myodes Jacq., Orchis morio L., O. pyramidalls I,., Satyrium viride L., and Serapias rubra L. This is incorrect. Thurmann did indeed list these species, but only as part of the modern vegetation of this region.

Eocene

Protorchis monorchis Massalongo (31-33) and Palaeorchis rhizoma (.Massalongo) Massalongo (32) (= Protorchis rhizoma Massalongo, 31): These species represent the first described and also the geologically oldest fossils that might possibly represent orchids. In 1857 Massalongo (31) listed, without benefit of description or illustration (hence nomina nuda) , the new generic name Protorchis, with two new species P. monorchis and P. rhizoma based on specimens from the calcareous Eocene deposits at Monte Bolca, Italy. Massalongo had only four specimens at his disposal — three of the former species, one of the latter (33, 34). In 1858 Massalongo (32) validly published Protorchis monorchis and also the new combination Palaeorchis rhyzoma (the specific epithet is an orthographic error) based on Protorchis rhizoma. The next year a more complete description and also a photograph (see Fig. 1) of Protorchis monorchis were published (33). In his 1858 work Massalongo dated Protorchis as "1851" with the added notation "in lit.” et in Musaeo" (32, p. 749). Since the 1854 reference is obviously unpublished, the nomina nuda in the 1857 report (31) thus represent the actual first (though taxonomically invalid) publication of

the names involved. Although Massalongo (31) initially listed his new species under the Orchidaceae, he subsequently (32-34) very carefully indicated the tentatively orchidaceous nature of his fossil specimens by including them in a new taxon, the Protorchidaceae ("Protorchidee" in 32, 33; or the Latinized "Protorchideae" in 33, 34). Massalongo (32, 33) admitted that he was unable to find in the extant flora counterparts of his fossils. Massalongo (32, 33) noted a resemblance of both his fossil species to the Araceae, which he apparently regarded as being rather close to the Orchidaceae (32). A superficial likeness between Palaeorchis rhizoma and the fossil alga Delesserites was rejected when he decided on the affinities of the former (32). After additional concern that Palaeorchis rhizoma might be butomaceous, Massalongo (32) finally decided to retain this species in his Protorchidaceae. This discussion illustrates the difficulty Massalongo had in assigning his fossils to an extant plant group. This fact is apparently realized by very few authors since a number (e.g., 15, 18, 28, 42) incorrectly state or imply that Massalongo had regarded his fossils as orchids.

According to Massalongo (32, descriptive terminology below is his) , the Protorchidaceae are next to the orchids and the aroids and consist of small herbs with tubers or rhizomes bearing lateral fibrous roots and several very slender, cuneate-obovate or spathulate leaves with entire margins and fine midribs. Misstatements to the contrary (15, 25, 26, 28, 43), both species do not possess tubers. Protorchis monorchis (FIGURE 1) has a round, solitary tuber whereas Palaeorchis rhizoma (never illustrated by Massalongo) differs chiefly in having a perpendicularly cylindrical rhizome covered with circular,

papillate leaf scars (32). The two species also differ somewhat in having spathulate versus oblong to spathulate leaves, respectively (32). Massalongo (33) subsequently indicated that Protorchis monorchis, of which three speci-mens were available (33), strictly speaking does not have a true tuber, but rather a rounded rhizome (FIGURE 1). In the same publication he (33) also added the

following information for Protorchis monorchis: tuber 7-8 mm in diameter; leaves 3-4 per plant, attenuate into a petiole, 5 cm long, and 12-15-18 mm wide.11 Although Massalongo (34, p. 133) finally indicated that specimens of both this species and Palaeorchis rhizoma are seedlings, there is no mention in his previous descriptions (32, 33) of the probable developmental age of these fossils. Most workers, usually referring only to Protorchis monorchis, have subsequently concluded that Massalongo's fossils are not truly representative of the Orchidaceae (e.g., 15, 18, 21, 25, 26, 35, 39, 40, 42). Schimper and Schenk (43) , however, accepted Massalongo's finds as orchidaceous, and van der Pijl (39, 40) apparently seems tempted to accept Protorchis monorchis as validly orchidaceous, no doubt because its Eocene date ties in with his understanding of the evolution of the bees. Meschinelli and Squinabol (3i) included both of Massalongo's fossil species under the Protorchidaceae in the order Micro-spermae (= Orchidales), but these authors noted that Palaeorchis rhizoma is probably a member of the Butomaceae. Krackowizer (28) 7

accepted the views of Meschinelli and Squinabol (36) except that he regarded Protorchis monorchis as a true orchid rather than as a protorchid. Admitting that both of Massalongo's fossils are doubtfully orchidaceous, Leslie A. Garay (pers. comm., 1972) nevertheless maintains that of all the fossils attributed to the Orchidaceae, Protorchis monorchis is perhaps the most likely candidate for inclusion in the family, largely because of its similarity to Orchis pallens L. In conclusion, the orchidaceous nature of Massalongo's fossils is clearly very questionable. As has already been suggested (Chester A. Arnold, pers. comm., 1967; 15, 18), perhaps the most charitable tiling that can be said about the affinity of Protorchis and Palaeorchis is that they are monocotyledonous.

Oligocene Antholithes pediloides Cockerell (11): T. D. A. Cockerell, the prolific describer of fossils from the western United States,8 in 1915 delineated from the Lower Oligocene (the age according to MacGinitie, 29; incorrectly regarded as Miocene by Cockerell, I I ) beds at Florissant, Colorado, a new species in the fossil artificial (or form) genus Antholithes. Cockerell attributed the fossil (FIGURE 9), A. pediloides, to the Orchidaceae because of its marked resemblance to the lip of Cypripedium, and he also presumed that the several small "subhyaline" spots scattered over the surface might represent the work of some insect. Other than the suggestive outline of the fossil, however, the lack of significant detail makes Cockerell's determination extremely doubtful. In his classic flora of the Florissant beds, MacGinitie (29) reached the same conclusion and disposed of A. pediloides among "species of somewhat doubtful taxonomic value" (p. 159) under incertae sedis .

Miocene Darrah (15) briefly discussed, and then discounted as truly orchidaceous, a fossil stem (apparently unnamed) from the Miocene of Hungary that had been described by a Robert Brown (there were several Robert Browns). Since Darrah provided no references in his note, and since alter considerable searching we have been unable to locate any additional information concerning this fossil, we can only quote Darrah (15, p. 149) fully:

"A third form [besides Massalongo's Protorchis and Palaeorchis] was once provisionally accepted as a fossil orchid. This fossil stem, found in rocks of Miocene age in Hungary, included a few structurally preserved hair-like roots which Robert Brown considered to be of some epiphytic: orchidaceous plant. . . .

As a matter of fact it was with this organ [the pseudobulb] that Robert Brown attempted to compare his supposed fossil from Hungary."

Pliocene Orchidacites orchidioides Straus (49), O. wegelei Straus (49), and O. cypripedioides Straus (50): In 1954 Straus (49) described from the Upper Pliocene of Willershausen, Germany, two species of fruits, Orchidacites orchidioides and O. wegelei which he assigned to the Orchidaceae. The two species, especially the former (as suggested by i t s name), were thought to resemble various species of Orchis (49). More recently, Straus (50) provided for Orchidacites a generic diagnosis, which had been omitted from the 1954 report, and described a third species, O. cypripedioides, with fruits regarded as similar to those of Cypripedium. These taxa are illustrated in FIGURES 2 to 8, reproduced from Straus' more recent paper (50). Orchidacites is a form genus proposed for fossil fruits comparable to the capsules of various extant orchid genera (50). According to Straus (50), the fossil capsules, 1.5 to 2.5 cm long, are ellipsoidal or narrowly ellipsoidal and have several longitudinal striae (FIGURES 2-8); the remnants of a corolla often occur at the fruit apex (FIGURES 2-4). Straus (50, also pers. comm., 1972) believes that the fossil fruits of Orchidacites came from epiphytes growing on rotting branches that eventually were blown into the sediments by wind, and, as a consequence, he has speculated (50, pers. comm., 1972) that many of the present-day orchids (e.g. Limodorum, Neottia, Corallorrhiza, and Cypripedium) were primitively epiphytic and now are terrestrial "secondary relicts." This view, of course, is dissonant with the conventional one that the terrestrial habit is ancestral and the epiphytic derived (e.g., 5, 6, 16, 17, 21-23, 39, 42). The Straus fossils have received little comment from either orchidologists or paleobotanists. Melchior (35) and Gothan and Weyland (26) accepted the fossils as unmistakably orchidaceous. Kirchheimer (27, p. 650), however, remained skeptical, believing that the inferior, wing like, ribbed gynoecium with a distinct styloid process evokes resemblances to young fruits of Halesia, Pterostyrax and other Styracaceae (a completely unrelated family in the dicotyledons). Straus (pers. comm., 1972), in counterargument, however, believes that the fruits he described are truly orchidaceous since fruits of the Styracaceae never show floral remains whereas fruits of the Orchidaceae often do. On examining the photographs reproduced herein (FIGURES 2-8), Garay (pers. comm., 1972) is also disinclined to accept Straus' fossils as orchidaceous because of the curious 3-pronged floral remnants (interpreted by Garay as a column) (FIGURES 2-4) and because of the apparently excessive number of ribs (FIGURES 2-8) for true orchid fruits (which have a maximum of six). Robert L. Dressier (pers. comm., 1972) is of a similar opinion, although he is less certain in excluding Orchidacites cypripedioides (FIGURES 5-8) from the orchids since the fossil "looks rather like a Cattleya fruit." In defense of Straus, we should note that a 3-pronged calyx of fused sepals occurs in some modern taxa (e.g. Pterostylis. see FIGURE 84 in 40: Masdevallia, etc.) and that on orchid fruits a greater number of ribs (than six) may be apparent since these may be variously secondarily divided (e.g., Trichopilia suavis Lindl. et Paxton). Unfortunately, Straus (50) hurts his own cause by interpreting the floral remnants (FIGURES 2-4) as a corolla, but it is perhaps more likely that they represent a calyx.

Quaternary

Quaternary orchid fossils are included here for completeness, although they are unimportant from the viewpoint of our understanding of the origin and most of the subsequent evolution of the family. The names of at least 20 extant species of orchids are listed in the Compendium Index of Paleobotany and are

attributed to both the Pleistocene and Holocene (= Recent or Postglacial) of the Quaternary. Most of these listings were compiled around the turn of the century, when the Compendium Index included casual, incidental references to fossils - a practice long discontinued (19) . Unfortunately, a number of these listings are not applicable because the original works discuss the various orchid species as components of the contemporary flora and not as fossils. This is the case with reports of Goodyera repens (L.) R. Br. from the Quaternary of Denmark, Himantoglossum hircinum (L.) Sprengel and Ophrys aranifera Huds. from the Postglacial of Switzerland, and Malaxis paludosa (L.) Sw. from the Holocene of Germany, which the Compendium Index attributes to Anderson (2), Naegeli (37, as cited in 7), and Becker (4), respectively. The Compendium Index also attributes the following extant orchid taxa to Sernander's (47) extensive work on the Quaternary (Wiirm Glacial and Postglacial) of Gotland, Sweden (names listed as they appear in Sernander): Anacamptis pyramidalis (L.) Rich., Cephalanthera ensifolia (Sw.) Rich., Corallorrhiza innata R. Br., Epipactis palustris (L.) Crantz, Gymnadenia conopsea (L.) R. Br., G. odoratissima (L.) Rich., Listera cordata (L.) R. Br., L. ovata (L.) R. Br., Malaxis monophyllos (L.) Sw., Neottia nidusavis (L.) Rich., Orchis angustifolia Wimm. et Grab., O. maculata L., O. militaris L., O. ustulata L., Platanthera bifolia (L.) Rich., and Sturmia loeselii (L.) Reichb. However, Sernander (47) merely discusses these and other orchid species in terms of a phytosociological survey of the modern bog vegetation of Gotland. The bogs Sernander studied did indeed contain identifiable fossils, but none of these were orchids. To our knowledge, there is only one report of a Quaternary fossil attributed to the Orchidaceae. In 1965 Vent (52, p. 200) described leaf and fruit impressions from the Riss-Wurm Interglacial of Weimar-Ehringsdorf, Germa-ny, and assigned these to "cf. Epipactis palustris (Mill.) Crantz" in the Orchidaceae. Garay (pers. comm., 1972) , however, discounted the orchidaceous nature of these fossils after examining Vent's photographs (FIGURE 10) .

SUMMARY Fossils dating from the Eocene to the Quaternary have been attributed to the Orchidaceae, but objections have been raised against the orchidaceous nature of all of these fossils. The most likely orchid fossils, nevertheless, remain Massalongo's famous fossils from the Eocene of Italy — Protorchis monorchis and Palaeorchis rhizoma — and especially Straus' recent finds from the Pliocene of Germany Orchidacites orchidioides, O. wegelei and O. cypripedioides. In conclusion, then, the Orchidaceae have no positive fossil record and in this sense present a striking parallel to two well-known gods of mythology: Athena, who sprang fully grown and fully armored from the head of Zeus; and the Aztec Huitzilopochtli, who was borne fully grown and fully armored from Coatlicue.

Acknowledgements: This study was carried out while the senior author was the recipient of a Smithsonian Institution postdoctoral fellowship. We thank Norris H. Williams and Leslie A. Garay for valuable discussions.

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